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Maintaining Dynamic Equilibrium
Nervous System
Two major parts comprise the human nervous system. The central nervous system is made up of the spinal cord and the brain. The peripheral nervous system includes the nerves that lead into and out of the central nervous system p392
Central Nervous System
The CNS receives sensory info and initiates motor control. The CNS is well protected by bone, the skull forming an enclosure around the brain and the vertebrae enclosing the spinal cord. Cerebrospinal fluid fills the spaces between the meninges to create a cushion that further protects the CNS. The spinal cord extends from the vertebral canal up through the bottom of the skull and into the base of the brain. The spinal cord is the vehicle of communication between the brain and the PNS.
Peripheral Nervous System
Consists of the autonomic and somatic nervous systems. The autonomic is not consciously controlled. This system is made up of the sympathetic and parasympathetic nervous systems, which control a number of organs within the body.
Sympathetic Nervous System
The sympathetic sets of the fight or flight reaction and prepares the body to deal with an immediate threat. When the system is stimulated, heart rate and breathing rate increase and blood sugar is released from the liver for energy. P 393
Parasympathetic Nervous System
Has an opposite effect to that of the sympathetic. When a threat has passed, the nerves of this system slow heart and breathing rates and reverse the effects of the SNS response.
Somatic Nervous System
Made up of sensory neurons that carry impulses from the bodys sense organs to the CNS. Also consists of motor neurons that transmit commands from the CNS to the muscles. This system, to some degree, is under conscious control. P394
A reflex occurs when the system sets off a specific reaction when a certain action is experienced.
Neurons and the Reflex Response
The structural and functional unit of the nervous system is the neuron. Both the CNS and PNS are comprised of interconnected neurons. The PNS consists of nerves which are numerous neurons held together by connective tissue. The CNS consists of 90% of the bodys neurons.
A reflex arc is the nerve pathway that leads from stimulus to reflex action.
The cell body of a neuron has a large, centrally located nucleus with a large nucleolus. The cytoplasm contains numerous mitochondria and lysosomes along with a golgi complex and rough endoplasmic reticulum.
Dendrites are the primary site for receiving signals from other neurons. The number of dendrites can range from one to thousands depending on the neurons function.
Neurons last over 100 years, do not undergo cell division after adolescence.
The axon is a long, cylindrical extension of the cell body that can range from 1mm to 1 m in length. When the neuron is receives a strong stimulus, the axon transmits impulses or waves of depolarization along its length. At the end of the axon are specialized structures that release chemicals which stimulate neighboring neurons or muscle cells. P395
A sensory neuron takes info from a sensory receptor such as a pain receptor to the CNS, while a motor neuron takes info from the CNS to an effector such as a muscle fiber or a gland. The interneuron receives info from both other interneurons and from sensory neurons and it exchanges info among neurons in the CNS.
Brain Structures
Medulla Oblongata attached to the spinal cord at the base of the brain, has a number of major functions, each of which is related to a particular structure. The cardiac center controls heart rate and the force of the hearts contractions. The vasometer center adjusts blood pressure by controlling the diameter of blood vessels and the respiratory center controls rate and depth of breathing. Also contains reflex centers for vomiting, coughing, hiccupping and swallowing.
Cerebellum controls muscle coordination. Although it only makes up 10% of the brains volume, it contains 50% of the brains neurons.
Thalamus is a sensory relay center. It receives sensations of touch, pain, heat and cold, as well as information from the muscles. If the sensations are mild the thalamus relays the info to the appropriate part of the cerebrum. It strong, the thalamus triggers a more immediate reaction while at the same time transferring the sensations to the homeostatic control center, the hypothalamus.
Hypothalamus
Main control center for the autonomic nervous system. Enables the body to respond to external threats by sending impulses to various internal organs via the sympathetic nervous system. It then stimulates the parasympathetic nervous system. Controls hunger, body temperature, aggression and other aspects of metabolism and behavior.P400
Cerebrum
Where information from senses is sorted and interpreted. Voluntary muscles that control movement and speech are stimulated here. Memories are stored and decisions are made as well.
Corpus Callosum
A series of nerve fibers that connect the left and right hemispheres of the brain.
Midbrain
A short segment of brainstem between the cerebrum and the pons (sight and hearing)
Pons
Contains bundles of axons traveling between the cerebellum and the rest of the CNS. Functions with medulla to regulate breathing rate and has reflex centers involved in head movement.
Meninges
A series of three membranes that surround and protect the CNS.
Cerebrum
Responsible for complex behavior and intelligence, interprets sensory inputs and initiates motor impulses.
All or None Principle
If an axon is stimulated sufficiently, the axon will trigger an impulse down the length of the axon. The strength of the response is independent of the stimulus. An axon cannot send a mild or strong response, it can only respond or not respond. Like the trigger of a gun once the pressure is strong enough the bullet is on its way, pulling the trigger harder has no effect on the speed of the bullet. P 403
Depolarization
When a neuron is sufficiently stimulated, a wave of depolarization is triggered. When this occurs, the gates of the k+ channels close and the gates of the Na+ channels open, allowing sodium ions to move into the cell, neutralizing the negative charge in the axon. This change in charge is called the action potential. The depolarization of one part of the axon causes the gates of the neighboring Na+ channels to open, and this depolarization continues along the length of the axon. Action potentials can occur in the dendrites and the cell body as well.
Re-polarization
Any specific region of axon is only depolarized for a split second. Almost immediately after the sodium channels have opened to cause depolarization, the gates of the K+ channels re-open and potassium ions move out. The Na channels close at the same time. This process, combined with rapid active transport of Na out of the axon by the sodium potassium pump re-establishes the polarity of that region of the axon. The speed with which this process occurs allows an axon to send many impulses along its length every second, if sufficiently stimulated. The brief time between the triggering of an impulse along an axon and when it is available for the next impulse is the refractory period (o.oo1s)
Myelin Sheath
A fatty layer formed by Schwann cells which surrounds the axon; speeds up the rate of depolarization.
Between each schwann cell is a gap called the node of ranvier where the axon membrane is exposed.
The schwann cells perform another function. As mature cells, neurons are incapable of reproducing themselves. This means that damage to the nervous system either by accident of disease cannot follow the same healing process that occurs in other parts of the body. Neurons that have a neurolemma or outer layer of schwann cells are capable of regenerating themselves if the damage is not too severe. P 404
Damaged neurons in the CNS cannot regenerate, but if an area of the brain itself is damaged, its functions can often be taken over by other parts of the brain. Damage to the spinal cord is usually permanent, and can lead to paralysis.
Synapses
Tiny gaps between neurons. The neuron that receives the stimulus is called the post synaptic neuron while the neuron that sends the wave of depolarization toward the synapse is the pre synaptic neuron. When a wave of depolarization reaches the end of a pre synaptic neuron axon, it triggers the opening of special calcium ion gates which trigger the release by exocytosis of neurotransmitter molecules. The neurotransmitter is then released into the synaptic vesicles, which are produced in the end of the axon. The neurotransmitter diffuses into the gap. P 405
Dendrites had special receptor sites and the neurotransmitter attaches to these receptors and excites or inhibits the neuron. The excitatory response involves the opening of sodium gates, triggering a wave of depolarization. The inhibitory response makes the post synaptic neuron more negative on the inside in order to raise the threshold of stimulus. This process is usually accomplished by opening chloride channels to increase the concentration of these negative ions in the neuron. Neurotransmitters can also stimulate or inhibit cells that are not neurons, particularly muscles, where they trigger the contraction of the muscle.
Enzymes break down neurotransmitters in the synapse after being released from pre synaptic neuron. Cholinesterase breaks down acetulcholine which is the primary neurotransmitter of the sympathetic nervous system.
Glutatmate cerebral cortex neurotransmitter that accounts for 75% of all excitatory transmissions in the brain.
GABA the most commin inhibitory neurotransmitter of the brain.
Dopamine elevates mood and controls skeletal muscles.
Seratonin involved in alertness, sleepiness, thermoregulation and mood.
Drugs have been developed to stimulate or inhibit specific neurotransmitters. Valium increases GABA levels to alleviate anxiety and prozac, an antidepressant, enchances the action of serotonin. P 406
Diseases
Multiple Sclerosis
A progressive disorder affecting the nerve cells in the brain and spinal cord. The myelin sheath that surrounds the nerve cells becomes inflamed of damaged and this disrupts the nerve impulses that are normally produced. The disruption of nerve signals causes a variety of symptoms, including blurred or double vision, slurred speech, loss of coordination, muscle weakness, a feeling of tingling, numbness or constriction in the arms or legs and occasionally seizures.
- attacks may occur in episodes during which the symptoms worsen, alternating with periods where symptoms improve.
- autoimmune disorder in which the immune system attacks the myelin sheaths
- no cure, can be treated with medication to suppress autoimmune reaction. As well as medication for symptoms like fatigue.
Alzheimers Disease
A form of dementia which is an impairment of the brains intellectual functions such as memory and orientation. The brain gradually deteriorates causing memory loss, confusion and impaired judgment. It results from deposits of the protein amyloid that distorts the communication paths between brain cells. Levels of Acetylcholine begin to drop, causing further breakdown of communication.
- impairment of recent memories and difficulty learning and retaining new information
- older memories are lost, may not recognize familiar faces and may not be able to carry out simple tasks.
- personality changes, irritable, anxious, delusional, even aggressive.
- not preventable, limited treatment options
- cholinesterase inhibitors increase the level of acetylcholine and may improve intellectual function for up to 9 months
- irreversible
Parkinsons Disease
Chronic movement disorder caused by the gradual death of the neurons that produce dopamine, a chemical that acts to carry messages between the areas of the brain controlling body movements.
- slight tremors and stiffness in limbs on one side of the body. As the disease progresses, tremor spreads to both sides and the limbs become more rigid, body movements slow and abnormal gate develops. Chronic, progressive disorder. When symptoms appear, 70-80% of dopamine producing cells are lost.
- No cure, but symptoms can be treated individually. Usually involving medications that boost dopamine levels or mimic the effects of dopamine on target brain cells.
- Longterm use of the most effective drugs can lead to mental impairment.
- Surgery may be attempted, creating small lesions or implanting electrodes in the specific brain regions that are overactive
Meningitis
- caused by viral/bacterial infection of the meninges
- viral is relatively common in children and usually clears up in 7-10 days.
- If not treated immediately, bacterial is fatal. Symptoms include headache, fever and a stiff neck. Light sensitivity, vomiting and drowsiness.
- Diagnosed by testing the cerebrospinal fluid that surrounds the spinal cord for the presence of bacteria or indications of immune system activity (spinal tap)
- Prevention involves reducing the risk of catching viruses/bacteria from others. Vaccines for some bacteria but none for viral.
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Name of Disorder
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Symptoms |
Neurological Explanation |
Treatments |
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Multiple Sclerosis (MS) |
Progressive disorder affecting the nerve cells in the brain and spinal cord. Blurred or double vision; slurred speech; loss of coordination; muscle weakness; a feeling of tingling, numbness, or constriction in the arms or legs, and sometimes seizures. |
The myelin sheath that surrounds the nerve cells becomes inflamed or damaged, and this disrupts the nerve impulses that are normally produced. |
No cure. Treated using medications that suppress the autoimmune reaction. It can also be treated by using different drugs for each symptom. |
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Alzheimers Disease |
Disorder of the nervous system. A form of dementia, which is an impairment of the brains intellectual functions such as memory and orientation. Brain deteriorates causing memory loss, confusion, and impaired judgement. Develops from loss of recent memories and difficulty learning to older memory loss, unable to recognize faces, becoming irritable, anxious, delusional, and aggressive. |
Results from deposits of protein called amyloid that distort the commuication paths between brain cells. At the same time, levels of acetylcholine begin to drop causing further breakdown of communication. |
Limited. Cholinesterase inhibitors work to increase brains level of acetylcholine and improve intellectual function for up to nine months, but the disease is an irreversible illness and mental function declines over a period of three to 20 years prior to death. |
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Parkinsons Disease |
A chronic movement disorder. Begin as slight tremors and stiffness in limbs on one side of the body. As it progresses the tremor spreads to both sides of the body and the limbs become more rigid, body movements slow, and a characteristic abnormal gait develops. |
Caused by gradual death of the neurons that produce dopamine. (chemical that acts to carry messages between areas of the brain controlling body movements.) |
medications that boost dopamine levels or mimic the effect of dopamine on target brain cells. Long-term use of these can lead to mental impairment and other complications. Surgery may be attempted when drug therapy is not effective, creating small lesions or implanting electrodes in the areas that are overactive in the disease. |
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Meningitis |
headache, fever, stiff neck, light sensitivity, vomiting, and drowsiness.
Fatality rates 10% many survivors suffer from complications such as hearing impairment. |
Caused by a viral or bacterial infection of the meninges. |
Viral-common in children, often clears up after a few days, whereas the bacterial if not treated immediately is fatal.
Vaccines are available for bacteria that cause meningitis. |
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Huntingtons Disease (chorea) |
Memory loss, dementia, involuntary twitching, clumsiness, chorea, and personality changes appear at midlife, progressing until death (15 years) jerky movements
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Nerve cells in certain parts of the brain degenerate causing progressive decreases in mental and emotional abilities and loss of control over major muscle movements.
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No cure and no way of slowing progression.
Fatal |
Effects of Drugs
Categorized as nervous system depressants or stimulants. Depressants slow down the CNS so that an individual may feel relaxed and feel less pain, but will also experience reduced coordination and judgment. Depressant drugs include alcohol, opiates such as heroin and morphine and minor tranquilizers such as valium. Stimulants speed up the CNS, and individuals may feel increased energy, and confidence but experience paranoia. These include caffeine, cocaine, MDMD, ecstacy and nicotine. Ecstacy has been found to affect neurotransmitters that produce feelings of euphoria and well being. Research has shown that after two weeks of use, ecstacy can deplete up to 90% of the brains serotonin supply and longterm use may lead to permanent changes in neurotransmitter concentrations in the CNS. Anaesthetic drugs also affect the CNS, the local anaesthetic is used to numb a small area by blocking the passage of nerve impulses from the skin to the brain. They disrupt the sodium channels needed to generate the action potential. General aneasthetics are used during major surgeries so that the patient is unconscious and feels no pain. Gases such as ether alter the brains function by disrupting proteins in the cell membranes. Barbiturates enhance the activity of neurotransmitters such as GABA and so reduce the activity of brain cells.
The lack of oxygen to a portion of the brain as a result of stroke causes that portion of the brain to die. Treatment for thrombolytic stroke involves the use of clotbusting drugs. A major drawback is that the medicine must be taken within a short interval after the stroke occurs.
Another problem is that some patients experience life threatening bleeding in the brain. Aspirin may also be prescribed for an individual showing symptoms of a stroke. Aspirin reduces the stickiness of the platelets, so it decreases the chances of a clot forming. Some strokes are caused by aneurisms there a blood vessel breaks in the brain and in these cases when the blood is thinned as with aspirin, the bleeding can become worse.
The Eye
Lens: behind the iris, the choroids layer thickens and forms the ciliary body which contains muscles to control the shape of the lens. The clear flexible lens changes as you look at objects close up or far away. The lens is attached to the suspensory ligaments that are attached to the ciliary muscles.
Retina: the inner layer of the eye, the retina is composed of two types of photoreceptors-rods and cones-allowing the eye to detect color and light.
Cone cells: specific cells located within the retina that are able to detect red green and blue. Cones require more light to stimulate them than rod cells which are more sensitive, but lack the ability to detect color.
Fovea: located directly behind the lens the fovea centralis is an area where cone cells are concentrated. This are produces the most distinct image.
Glaucoma is caused by a buildup of aqueous humor between the lens and the cornea. This fluid produced continuously and has its own drainage system. If the system is blocked, the fluid builds up and creates pressure that can destroy the nerve fibers responsible for peripheral vision. The damage cannot be repaired, but it can be curbed with drugs or surgery.
Astigmatism is an abnormality in the shape of the cornea or lens that results in uneven focus. In these cases, the image of the object can be focused in front of the retina using corrective lenses.
Myopia or near sightedness is a condition in which the person has difficulty seeing things that are far away. It is usually caused by the eyeball being too long or the ciliary muscle system being too strong.
Hyperopia is a condition in which a person has difficulty seeing things close up. It is caused by the eyeball being too short or the ciliary muscle system being too weak to focus the image of nearby objects onto the retina.
Corneal Transplants
In the procedure the diseased cornea is replaced by a donor cornea which like livers and kidneys, comes from individuals who have died and donated their corneas. Corneas do not need to be type matched to the same extent as a kidney or liver. This procedure is used when the cornea is seriously impaired usually by the disease.
Photorefractive Keratectomy
An outpatient procedure preformed with local anaesthetic eye drops. The laser beam reshapes the cornea by cutting mircroscopic amounts of tissue from the corneas outer surface. This procedure takes only a few minutes and recovery time is quick.
Laser in situ keratomileusis (LASIK)
A more complex procedure performed for all degrees of nearsightedness. A knife is used to cut a flap of corneal tissue then a laser removes the tissue underneath and the corneal flap is replaced. Both of these procedures correct astigmatism, hyperopia and myopia.
The Ear
Tympanic membrane: passes sound waves to the malleus. Sound waves which travel by vibrations of air molecules cause the tympanic membrane to vibrate. These vibrations pass across the membrane to the malleus or hammer which cause the incus and finally the stapes to move.
Ossicles: located between the tympanic membrane and the oval window. Comprised of three small bones, the ossicles transmit sound waves through vibrations from the ear drum to the oval window.
Between the middle ear and the nasopharynx is the auditory tube or Eustachian tube. This tube allows air pressure to equalize, such as on airplanes where yawning can cause air to pass through the tube and the ear will pop.
Semi circular canals: located in the inner ear, are involved in balance and equilibrium.
Cochlea: located in the inner ear, involved in hearing, contains three canals: vestibular, chochlear, and tympanic, all of which are visible is the cochlea is uncoiled.
Nerve deafness is caused by damage to the hair cells in the spiral organ. Hearing loss is usually uneven, with some frequencies being more affected than others. Typically found with aging and cannot be reversed.
Conduction deafness is caused by damage to the outer or middle ear that affects the transmission of sound waves to the inner ear. Does not usually cause a total loss of hearing because sound waves can also be transmitted through the skull bones to the inner ear. This type of hearing loss can frequently be improved with the use of hearing aids.
Hearing Aids
Conventional: have a microphone that gathers sound, an amplifier to increase the volume, and a receiver that transmits the sound to the inner ear.
Programmable: have an analog circuit that a professional can program to an individuals needs. Automatic volume control.
Digital: an advancement that processes sound digitally. Individuals differ in the levels of hearing loss at different frequencies require different levels of amplification. It can shape amplifications across various pitches and frequencies according to individuals needs.
Eustachian tube implants
Tiny plastic tubes are placed in a slit in the eardrum, relieving the pressure from the fluid, which can cause chronic middle ear infections and allowing it to drain. The tubes are pushed out of the ear by the eardrum as it heals (6-24months)
FSH stimulates the process of spermatogenesis, allowing the seminiferous tubules to release inhibin.
Inhibin forms a negative feedback loop with FSH. It acts of the hypothalamus to slow the production of the releasing factors that control the release of FSH. The interaction of inhibin and FSH controls the rate of formation of sperm.
LH stimulates the interstitial cells of the testes that surround the seminiferous tubules which produce male sex hormones.
Testosterone major androgen, responsible for the development of the male secondary sexual characteristics.
Estrogen stimulates the endometrium of the uterus to thicken and increase the blood supply in preparation for a possible pregnancy. Also inhibits the levels of FSH, forming a negative feedback loop.
Progesterone during ovulation, LH stimulates the corpus luteum to produce progesterone, which inhibits the development of other follicles, thus only one ovum is released during each cycle.
Luteinizing hormone stimulates the corpus luteum to produce progesterone.
FSH - stimulates the follicle to produce estrogen.
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Gland |
Location |
Hormone Produced |
Target Tissue |
Effects |
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Pineal |
in the brain, above the pituitary gland (limbic system) |
Melatonin |
brain tissue |
sleepiness |
|
Pituitary (master gland) |
in the brain (limbic system) |
TSH (thyroid stimulating hormone)
HGH(human Growth Hormone)
Prolactin
ADH(anti-diuretic hormone)
Oxytocin
FSH
LH
ACTH
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· thyroid gland
· bones tissues
· mammary glands
· Kidneys
· smooth muscle in uterus, mammary glands.
· Ovaries, testes
· adrenal cortex
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· stimulates thyroid to produce and secrete thyroid hormone.
· stimulates body growth by increasing intestinal absorbtion of calcium & stimulating protein synthesis and lipid metabolism.
· stimulates the development of mammary gland tissue and milk production.
· regulates sodium levels in the bloodstream.
· triggers muscle contractions during childbirth and the release of milk from the breasts.
· ovulation |
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Hypothalamus |
In the brain (limbic system) connected to the pituitary gland |
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affects metabolism, kidneys, appetite, mental alertness, reproduction, and growth/ developement |
continuously monitors the state of the bodys internal environment and regulates pituitary gland activity. |
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Thyroid |
above trachea in neck |
Thyroxine, Calcitonin |
heart; skeletal muscles; liver; kidney; blood calcium levels |
increases basal metabolic rate; oxygen consumption; acts by increasing the amount of excreted calcium |
|
Parathyroid |
embedded in the thyroid glands above the trachea in the neck. |
PTH |
Bone tissue
kidneys
duodenum |
affects blood calcium levels |
|
Adrenal |
|
adrenaline and noradrenaline |
sympathetic nervous system |
excitatory neurotransmitters; having limited and short term effects on the body. |
|
Pancreas |
near small intestine |
glucagon; insulin |
muscle tissue; adipose tissues; liver; |
regulate metabolism; forces body to store nutrients |
|
Testes |
outside body cavity |
testosterone Inhibin FSH |
hypothalamus; sperm; muscle tissue; hair; fat; larynx; penis; testes. |
Slows FSH; produces sperm; causes development; inhibits production of LH |
|
Ovaries |
abdominal region |
estrogen |
|
development; reproduction |
|
Thymus |
between the lobes of the lungs in the chest cavity. |
thymosin |
t cells |
stimulates the production and maturation of lymphocytes in t cells. |
UNIT 2 REPRODUCTION AND DEVELOPMENT
#1 The stages of interphase:
1st stage gap 1 or g1; cells are carrying out metabolic activities to prepare for cell division.
2nd stage S phase; DNA is replicated
3rd stage gap 2 or g2; cells prepare to undergo division.
#2 The stages of mitosis:
1st stage prophase; chromatin coils and supercoils forming thick, condensed chromosomes. Each chromosome is made up of two sister chromatids, which are held together by a centromere. Sister chromatids are genetic copies of each other, having identical DNA. The nuclear membrane and the nucleolus disappear. Centrioles made up of microtubules migrate to opposite poles of the cell. Spindle fibers, also made up of microtubules, start to form between the two centrioles.
2nd stage Metaphase; the spindle fibers attach to the centromere of the replicated chromosomes. The chromatids are guided by the spindle fibers to the middle of the cell, also known as the cells equator. A spindle fiber from one pole is attached to one chromatid and a spindle fiber from the opposite pole is attached to the other chromatid at the centromere.
3rd stage Anaphase; the centromere splits apart and the chromatids are pulled to opposite poles of the cell by the spindle fibers. The chromatids are pulled as a result of the shortening of the microtubules that make up the spindle fibers.
4th stage Telophase; begins when the chromatids have reached the two opposite poles within the cell. At this time, each of the chromatids is called a single, non replicated chromosome. The chromosomes now begin to unwind and become less visible. The spindle fibers are no longer needed, so they break down and disappear. The nucleolus reappears. A nuclear membrane forms around each new set of chromosomes, which are located at the opposite poles of the cell.
#3 Cytokinesis the separation of the cytoplasm and the formation of two new daughter cells. During this process, the cytoplasm divides between the two halves of the cell. In animal cells, an indentation of the membrane surrounding the two daughter cells forms and deepens. In plant cells, a cell wall and membrane form and separate the two newly formed nuclei.
#4 It is important for chromosome number to be maintained during cell division and organism reproduction. Each new cell must have a complete set of chromosomes in order to maintain itself and to produce to new cells. In reproduction, a complete set of chromosomes is critical, due to the reduction from 46 to 23 chromosomes in the production of sex cells.
#5 The stages of meiosis:
Interphase as in mitosis, the chromosomes replicate during interphase before cell division begins in meiosis 1.
Prophase 1 each pair of chromosomes that carry the same genes, called homologous chromosomes, become aligned, forming tetrads. During the pairing process, crossing over can occur, in which non sister chromatids exchange segments of chromosomes. Each segment contains hundreds or even thousands of genes. This allows for the recombination of genes in each chromosome and contributes greatly to the genetic variation. As a result, individual chromosomes contain some genes from maternal origin and some genes from paternal origin.
Metaphase 1 a spindle fiber attaches to the centromere of each chromosome. A spindle fiber from one pole attaches to one pair of sister chromatids, and a spindle fiber from the opposite pole attaches to the other pair of sister chromatids in the tetrad. The fibers pull each tetrad to the equator of the cell. However, the chromosomes do not line up in single file as they do in mitosis. They line up in the homologous pairs, one on each side of the cells equator.
Anaphase 1 the homologous chromosomes separate and move to opposite poles of the cell. They are pulled apart by the shortening of the spindle fibers. The centromere does not split and the sister chromatids are held together. Thus, only one chromosome from each pair will move to each pole of the cell.
Telophase 1 does not occur in all cells, sometimes goes directly to meiosis II. If it does not occur, homologous chromosomes begin to uncoil and the spindle fibers disappear. The cytoplasm is divided, the nuclear membrane forms around each group of chromosomes and two cells are formed. Each new cell contains one copy of each chromosome. Because each chromosome already consists of two chromatids, a second chromosome replication does not take place between telophase 1 and prophase II. In females, meiosis II occurs after the egg is fertilized by a sperm cell.
Meiosis II the phases of meiosis II are identical to mitosis. The two cells from telophase I go through prophase II, metaphase II, anaphase II, and telophase II. Each cell beginning meiosis II is haploid but consists of replicated chromosomes.
Spermatogenesis p477
meiosis in mature males takes place in the testes. The production of sperm starts with a diploid germ cell called a spermatogonium. This cell enlarges and undergoes meiosis 1 and 2. The final product is four haploid sperm cells. Each cell has the same number of chromosomes and the same amount of cytoplasm. The sperm cells mature, the nucleus forms into a head and a long tail forms.
Oogenesis
Takes place in the ovaries
the process starts with a diploid germ cell called an oogonium. The cell enlarges and undergoes meiosis 1 and 2. At the end of meiosis 1, the cytoplasm is unequally divided. The cell with the most cytoplasm is the primary oocyte. The other cell is called a polar body. After meiosis 2, the cytoplasm is again unequally divided, only one of the cells becomes an egg. The purpose of the unequal division of the cytoplasm is to provide the ovum with nutrients in the first few days after fertilization.
Cloning
involves bypassing the meiosis step of animal reproduction in cells.
Instead, the nucleus of an egg cell from a surrogate mother animal is removed. The diploid nucleus of a cell from the animal to be cloned is placed in the egg and then implanted into the surrogate mother's uterus. The cells divides and forms an embryo, which develops into a new animal that will be an exact copy.
Stem Cells
undifferentiated cells that can give rise to any type of cell.
Until they differentiate, they have the unique ability to reproduce themselves. Found in embryos, bone marrow, blood, muscle tissue, lining of the digestive tract, brain and retina of the eye.
#10 Reproductive cloning the development of a cloned human embryo for the purpose of creating a cloned human being.
Therapeutic cloning the culturing of human cells for use in treating medical disorders.
#11 Three possible benefits to stem cell research are:
- treatment of cancers, strokes, hepatitis, spinal cord injuries, Alzheimers disease, diabetes, heart disease, muscular dystrophy, AIDS, and other disorders.
- A sick persons DNA could be transferred to a human egg. Stem cells from an embryo developed from the egg could be used to treat the sick person.
- It once seemed that adult stem cells could only develop into a few types of tissue, but recent findings have shown that scientists may be able to program adult stem cells to act like embryonic stem cells.
#8 At the end of meiosis I, the cytoplasm is not equally divided between the two daughter cells. The cell that receives most of the cytoplasm is called the primary oocyte. The other cell is called a polar body and is not a viable sex cell. As the primary oocyte undergoes meiosis II, the cytoplasm is again unequally divided. Only one cell becomes an egg, or ovum, and contains most of the cytoplasm. The other cell, a polar body, is not a viable sex cell. The purpose of the unequal division of the cytoplasm is to provide the ovum with sufficient nutrients to support the developing zygote in the first few days following fertilization.
Testes produce sperm and reproductive hormones. They hang outside of the body to ensure proper temperature for the production of healthy sperm
Penis transfers sperm into the female reproductive system during intercourse.
Seminiferous Tubules: long coiled tubes which make up the testes where spermatogenesis takes place.
Sertoli Cells: support, regulate and nourish developing sperm
Epididymus: where sperm mature and become motile.
Seminal Vesicles: produce a mucus like fluid containing the sugar fructose, providing energy for the sperm.
Prostate and Cowpers glands secrete an alkaline fluid to neutralize the acids in the female reproductive tract.
Vagina: entrance for the penis to deposit sperm
Cervix: the opening to the uterus
Uterus: thick walled, muscular organ
Endometrium: the lining of the uterus
Ovaries: produce ova and are suspended in the abdominal cavity.
Oviducts: transfer an ovum from the ovary to the uterus.
Fimbriae: finger like projections which sweep over the ovaries to sweep an ovum into the oviduct.
#12 FSH stimulates the process of spermatogenesis, allowing the seminiferous tubules to release inhibin.
Inhibin forms a negative feedback loop with FSH. It acts of the hypothalamus to slow the production of the releasing factors that control the release of FSH. The interaction of inhibin and FSH controls the rate of formation of sperm.
LH stimulates the interstitial cells of the testes that surround the seminiferous tubules which produce male sex hormones.
Testosterone major androgen, responsible for the development of the male secondary sexual characteristics.
#13 Estrogen stimulates the endometrium of the uterus to thicken and increase the blood supply in preparation for a possible pregnancy. Also inhibits the levels of FSH, forming a negative feedback loop.
Progesterone during ovulation, LH stimulates the corpus luteum to produce progesterone, which inhibits the development of other follicles, thus only one ovum is released during each cycle.
Luteinizing hormone stimulates the corpus luteum to produce progesterone.
FSH - stimulates the follicle to produce estrogen.
#14 Follicular stage increased levels of FSH stimulate the follicles to release increased quantities of estrogen into the bloodstream, stimulating the endometrium of the uterus to thicken and increase the blood supply in preparation for a possible pregnancy. Estrogen inhibits the production of FSH, while stimulating the hypothalamus to release large amounts of LH, which trigger the release of an ovum from one of the developing follicles.
Ovulation usually occurs at the midpoint of a 28 day cycle. The release of the ovum triggers a rapid biochemical change in the follicle that released the ovum. The follicle changes to become the corpus luteum, a group of cells that produces progesterone.
Luteal stage LH stimulates the corpus luteum to produce progesterone which
inhibits the development of other follicles and also inhibits the production of LH. As the level of LH decreases, the corpus luteum begins to degenerate and progesterone levels decrease, ending the luteal stage. This decrease in progesterone decreases the blood supply to the endometrium and leads to menstruation.
Menstruation the endometrium disintegrates, its blood vessels rupture, and the tissues and blood flow out of the vagina.
AIDS
attacks the immune system of the infected person, specifically the helper tcells. As the levels of these cells in the blood drop, the infected person becomes more susceptable to a variety of infections, eventually leading to sickness and death.
-weight loss,night sweats, fatigue, fever. Thrush and Herpes recur. Nervous disorders develop, pneumonias, skin cancer
-Treatments prolong death
Chlamydia
-bacterial
-burning sensation while urinating(men)
-discharge from vagin, pain, fever
-asymptomatic
-sores on the cervix increasing risk of aquiring aids.
-may contract PID
-treatable, curable with antibiotics
-no permanent effects.
Hepatitis B
-viral
-flu like, fever, headache, nausea, loss of appetite and abdominal pain, jaundice
-liver infection and failure, cancer or death
-some recover while others are asymptomatic carriers
-vacccines available
Genital Herpes
-viral
-cold sores, fever blisters on the mouth
-tingling or itching followed by blisters, painful sores.
-flu like symptoms
-some experience no symptoms
Syphilis
-bacteria
-ulcerated sores
-rash on palms and soles
-cardiovascular and nervous system affected.
Gonorrhea
-bacterial
-infection of the urethra, cervix, rectum and throat.
-pain on urination, PID, infertility
-infection can spread through blood to joints and heart valves or brain
-can be treated
Seven causes of human infertility:
Blocked oviducts (caused by PID)
Failure to ovulate (caused by hormonal imbalances)
Endometriosis (endometrium grows outside uterus)
Damaged eggs(caused by environmental factors)
Obstruction in the vas deferens or epidydymus(caused by STIs)
Low sperm count (numerous factors temperature, smoking/alcohol)
High proportion of abnormal sperm(factors such as temperature, toxins, STIs)
Technological solutions to human infertility:
artificial insemination (sperm implanted in vagina)
in vitro fertilization (fertilized oocytes placed in uterus)
in vitro maturation (follicles induced to mature into oocytes outside uterus)
superovulation ( FSH injections stimulate the development of multiple follicles)
surrogate motherhood (fertilized oocyte if placed in uterus of surrogate mother)
cryopreservation (oocytes, semen, and embryos preserved by freezing)
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Physical Method |
Chemical Method |
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Abstinence
vasectomy
tubal ligation
IUD
Diaphragm
Cervical cap
Male condom
Female condom
Rhythm method |
Birth control pill
Needle (depo-provera)
Spermicidal jelly and foam |
Fertilization
sperm and egg interact, forming a zygote
when the head of a sperm cell successfully connects with an egg, its acrosome releases enzymes that digest the jelly coating of the egg and stimulates the development of an impenetrable coat, preventing other sperm from entering
Cleavage after fertilization, the zygote continues down the oviduct toward the uterus, meanwhile undergoing cell division. Its overall size does not change.
Morula the mass of identical cells while the embryo is undergoing cleavage.
Blastocyst a nearly hollow ball of cells formed by the time the embryo reaches the uterus. Contains a group of cells called the inner cell mass which will eventually develop into a baby.
Gastrula during gastrulation, where the cells begin to specialize, the embryo is called a gastula.
Germ Layers distinct layers which the embryos cells are arranged into durng gastrulation. Formed by continuing mitotic division and migration. By the end of gastrulation there are 3 layers, endoderm, mesoderm, and ectoderm.
Neural development the mesoderm forms the notochord. The nervous system develops from the ectoderm that is located just above the notochord. Cells along the surface of the notochord thicken. Folds develop on each side of a groove along this surface, becoming a tube when they fuse. Once the folds have fused, the embryo is called the neurula. The anterior end of the neural tube becomes a brain.
Differentiation
the process in which each of the three layers of the gastrula develops into different parts of the body
The stages of childbirth
Dilation stage uterine contractions and oxytocin cause the cervix to open. During this stage, the amnion breaks and the amniotic fluid is released through the vagina.
Expulsion stage forceful contractions push the baby through the cervix to the birth canal. As the baby moves through the canal, the head rotates, making it easier for the body to pass through the birth canal.
Placental stage about 10-15 minutes after the baby is born, the placenta and umbilical cord are expelled from the uterus
Implantation at the end of the first week, when the embryo attaches itself to the endometrium. The trophoblast secretes HCG, which prevents the corpus luteum from disintegrating. For three weeks, the corpus luteum continues to produce progesterone. The progesterone maintains the endometrium and prevents menstruation.
Childbirth - progesterone levels drop and oxytocin is released, stimulating uterine contractions.
Lactation Prolactin, the hormone that is needed for milk production, is not secreted during pregnancy. High levels of estrogen and progesterone suppress the anterior pituitary production of prolactin. Once the mother has given birth, the pituitary begins to secrete prolactin. Milk production begins within a few days. When stimulated by a suckling infant, nerve impulses are sent to the pituitary, triggering the release of oxytocin, thus causing contractions within the mammary lobules
Chorion outer membrane enclosing the embryo of mammals, reptiles, and birds. It has a dense concentration of blood vessels and aids in the formation of placenta in mammals. Involved in gas exchange.
Allantois membranous sac that grows from the lower gut in the embryo of a mammal, reptile, or bird. In mammals, it helps to build the umbilical cord and placenta.
Amnione inner of the two membranes enclosing the embryo of a mammal, reptile, or bird and its amniotic fluid which provides a liquid environment for the developing embryo.
Yolk dense material containing protein and fats that provide nourishment for the developing embryos of animals such as birds and reptiles.
#21 Placenta - a blood vessel rich organ that is present only during pregnancy. It begins to form from the chorion once the embryo is fully implanted. The chorion develops many tree like projections that extend into the uterine wall, serving as an anchor. The projections contain blood vessels which together with the chorion, form the placenta. During and after its development it produces progesterone and estrogen, preventing any new follicles from maturing, also maintaining the uterine lining. The developing embryo depends upon the placenta for survival. It gets all its nutrients and oxygen from the placenta and all its wastes are removed through the placenta.
Umbilical cord connects the developing embryo and fetus to the placenta.
Teratogen
any agent that causes a structural abnormality due to fetal exposure during pregnancy.
ciggarette smoke may constrict the fetus's blood vessels, preventing it from getting enough oxygen. Babies may be underweight and may suffer convulsions.
Alcohol can affect the fetus's brain, CNS, and physical development. FAS babies have decreased weight, height, and head size. Head and face may be malformed.
Unit 3 Genetic Continuity
genetics
the branch of biology dealing with the principles of variation and inheritance in organsisms.
Mendel's principle of dominance:
when individuals with contrasting traits are crossed, the offspring will express only th dominant trait.
Law of segregation:
states that inherited traits are determined by pairs of factors. These factors segregate in the gametes, with one in each gamete.
Genes are part of the chromosome that governs the expression of a particular trait.
The product rule:
the probability or chance that two or more independant events will occur together is the product of their individual probabilities of occuring alone p531
Hybrid Cross
T t phenotype: 1:1 genotype: 1:1
T TT Tt
T TT Tt
X x phenotype: 3:1 genotype: 1:2:1
X XX Xx
x Xx xx
DiHybrid Cross
RRYy crossed with rrYY
RY Ry
rY RrYY RrYy
RrYy crossed with RrYy
Ry RY rY ry
RY RRYy RRYY RrYY RrYy
Ry RRyy RRYy RrYy Rryy
rY RrYy RrYY rrYY rrYY
ry Rryy RrYy rrYy rryy
Genotype : 9:3:3:1
Law of Independant Assortment
the inheritance of alleles for one trait does not affect the inheritance of alleles for another trait. p 537
Codominance
Red flower (RR) x White Flower (R'R')
R R
R' R'R R'R = all pink flowers
R' R'R R'R
Human Blood Types
phenotype genotype
A |A|A or |Ai
B |B|B or |Bi
AB |A|B
O ii
|A |B
|A |A|A |A|B
i |Ai |Bi
Chromosome Theory
genes are carried on chromosomes. It is the segregation and independant assortment of chromosomes during meiosis that accounts for the patterns of inheritance.
Gene Chromosome Theory
genes exist at specific sites arranged in a linear fashion along chromosomes.
Sex Linked Inheritance
Gene for eye color is on the X
red eye female xR xR
white eye male xry
xR xR
xr xRxr xRxr
y xRy xRy
Hemophilia!!!
Carried in the recessive gene (xh not xH)
Hemophiliac female = XhXh
Hemophiliac male = XhY
Normal male = XY
Normal female = XX
carrier female = XhXH
mother XHXh father XhY
Xh Y
XH XHXh XHY
Xh XhXh XhY
Down Syndrom
trisomy 21 - individual has 3 copies of chromosome 21.
moderate mental impairment, think tongue that can creat speech defects. The skeleton may not develop properly, short stocky body with think neck
Turner Syndrom
-single x chromosome and no y chromosome
an xo woman will be infertile, will have external female genitalia but no ovaries. webbed neck, heart defects, kidney abnormalities, learning difficulties, and thyroid dysfunction
Klinefelter Syndrom
xxy
will have immature male sexual organs and will not grow facial hair. They are also likely to show some breast development.
Jacob's Syndrom
speech and reading problems and persistant acne.
Tay Sachs Disease
an autosomal recessive disorder not specific to the sex of the person.
Children with this disease appear normal at birth. Their brains and spinal cords begin to deteriorate at 8 months of age. By their first birthday, these children are blind, mentally handicapped, and display little muscular activity.
They lack an enzyme in the lysosomes of the their brain cells. Lysosomes are cell organelles in which large molecules are digested. The recessive allele doesn't code for the production of the enzyme responsible for breaking down lipids inside the lysosomes. Undigested lysosomes become enlarged and eventually destroy the brain cells that house them.
PKU
Sickle Cell Anemia --> Page 556
Progeria
causes individual to age rapidly
results from random mutation of a gene which must be dominant
Ultrasound - provides an image of the developing fetus
Amniocentesis - sampling of the amniotic fluid
Chorionic Villi Sampling - removal of cells from the chorion which contain genetic material.
P 607
Fetoscopy
Genetic Markers
P 618
Human Genome Project
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