Bio-201 Exam 3 Module 10
23 g. How many Na and K ions does the Na/K pump move and in what direction do these two ions move?
3 Na+ out and 2 K+ in
41. Recognize AND explain examples of how various drugs can affect synaptic transmission. No, you don't have to memorize any of the specific drugs, but you are expected to predict the effects of a drug if you are provided with the mechanism of action of the drug.
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24. Explain each step involved in the transmission of an impulse from an axonal terminal across a synapse to the receptor membrane of a dendrite. You probably want to draw out the steps. Make sure to keep your ions straight, especially the roles of calcium and sodium. This one should take you some time!
AP reaches axon terminal. The AP opens the voltage gated ion channels for Ca 2+ to enter the axon terminal. The Ca 2+ pushes the vesicles full of neurotransmitters to the cell membrane of the neuron where exocytosis occurs. The neurotransmitter exits the cell and travels across the synapse where they bind with ligand-gated channels. The channels open allowing Na+ to stream into the cell, depolarizing the soma of the next neuron and starting a new AP.
35. Explain what would happen if acetylcholinesterase where inhibited.
Ach builds up in the synapse leading to continuous stimulation of the postsynaptic muscle cell - leads to asphyxia
34. Make sure you really, really, really understand the difference between the following: Agonist vs Antagonist vs Inverse Agonist
Agonist- drugs that occupy receptors and activate them Antagonist- Drugs that occupy receptors but do not activate them. Antagonists block receptor activation by agonists Inverse Agonist- reduce the activity of receptor, act to reduce agonist potency, but unlike antagonist, can reduce potency even when agonist is not present
16. What is the name of the cell whose function is to connect neurons to blood capillaries?
Astrocytes ·Abundant, Star-shaped Cells - Form Framework Of CNS ·Contribute To BBB And Regulate Composition Of Brain Tissue Fluid ·Convert Glucose To Lactate To Feed Neurons ·Secrete Nerve Growth Factor Promoting Synapse Formation ·Sclerosis - Damaged Neurons Replace By Hardened Mass Of Astrocytes
6. Compare and contrast the functions of axons and dendrites.
Axon- Only one per neuron Carries electrical signal (action potential) to target Axon structure is critical to function (i.e. Nodes of Ranvier) Dendrite- •Highly branched •Dendritic spines: -Many fine processes -Receive information from other neurons 80-90% of neuron surface area
4. What are the four neuroglia of the CNS and the two neuroglia of the PNS?
CNS (Central Nervous System) - neuroglia (glial cells) Astrocytes, microglia, ependymal cells, oligodendrocytes PNS (Peripheral Nervous System) - satellite cells, Schwann cells
23 b. What happens to bring a neuron up to threshold? What type (chemically-gated or voltage-gated) of ion channels are involved in reaching threshold? What exactly opens these ion channels?
Chemically gated ion channels allow Na+ inside the soma, making the soma depolarize and subsequently, a action potential propagate down the axon. Neurotransmitters are the chemical that open the chemically gated ion channels.
28. List AND describe the two classes of neurotransmitters.
Excitatory neurotransmitters: cause depolarization of postsynaptic membranes promote action potentials Inhibitory neurotransmitters: cause hyperpolarization (goes in opposite direction of depolarization) of postsynaptic membranes suppress action potentials
38. Explain how some common drugs affect the GABA-ergic receptor on the postsynaptic membrane.
GABA ensures important neurons fire only. Tetanus toxin blocks release of GABA resulting in unopposed action of excretory NT's on the postsynaptic cell Alcohol is one of the depressant drugs in widest use, and is believed to cause its effects by interacting with the GABA receptor. Initially anxiety is controlled, but greater amounts reduce muscle control and delay reaction time due to impaired thinking.
23 d. What ion is responsible for repolarization? What direction does this ion move? What type (chemically-gated or voltage-gated) of ion channel opens during repolarization?
K+ streaming out of the cell is responsible for repolarization. the ion moves out of the cell through voltage gated ion channels
23 c. What ion is responsible for depolarization? What direction does this ion move? What type (chemically-gated or voltage-gated) of ion channels of ion channel opens during depolarization?
Na+ streaming in to the neuron is what causes depolarization. Voltage gated ion channels are the type of channel that open during depolarization
13. Along the axons of myelinated neurons there are gaps in the myelin where the axolemma is exposed. What is the name given to these gaps in myelin?
Nodes of Ranvier
30. Explain the difference between temporal and spatial summation. You probably want to draw and graph of each of them.
Temporal summation- multiple depolarizing stimuli from same source in succession that work together to depolarize neuron Spatial Summation- multiple stimuli arrive from different sources that work together to depolarize neuron
32. Diagram AND explain (in your own words) the mechanism of action of tetanus toxin.
Tetanus Toxin blocks the release of inhibitory NT's resulting in unopposed action of excitatory NT's on the postsynaptic cell
23 h. Explain what nondecremental means.
The AP does not get weaker with distance
23 e. What is the cause of hyperpolarization?
The k+ voltage gated ion channels not closing right away after repolarization and some k+ slipping through
39. Explain how neurotransmitter reuptake inhibition affects the synapse.
The reuptake port is blocked not allowing neurotransmitter to leave the synapse causing the synapse to stay active and keep sending signal Other times, the neurotransmitter is not broken down until it is taken back into the presynaptic neuron (reuptake)
23 f. What is the sodium-potassium pump, and why is it so important to nerve impulse transmission?
The sodium potassium reestablishes resting membrane potential after hyper polarization occurs. If resting membrane potential is not established it is harder for the neuron to send another action potential.
23 m. Explain how it is possible in a myelinated axon for action potentials to occur at only the Nodes of Ranvier. In other words, what causes the action potential to occur at each of the Nodes of Ranvier?
There are wayyy more voltage gated channels in the nodes of Ranvier which make it easier for Na+ to enter the axon at the nodes more than anywhere else
23. Answer the following review questions regarding action potential generation and propagation: a. What is responsible for the resting membrane potential of a neuron?
a. The Na+/K+ pump is responsible for maintaining the resting potential of a neuron.
36. Describe the similarities between the neuromuscular junction between a neuron and a muscle cell and the cholinergic synapse between two neurons.
almost exactly the same, NMJ just needs Ach and Achnesterace ??
5. Label the structures found in a neuron AND describe their functions.
dendrite- receive neurotransmitters soma- integrate and send signal axon- where signal propagates axon terminal- where neurotransmitters sent to next neuron •Large nucleus and nucleolus •Cytoplasm (perikaryon - around the nucleus) •Mitochondria - What does this do? •Nissl Bodies - RER and ribosomes (produce neurotransmitters) •Cytoskeleton •Neurofilaments and neurotubules: -in place of microfilaments and microtubules •Neurofibrils: -bundles of neurofilaments support dendrites and axon
26. Classify the major receptor types that we use to "sense the world around us" as iontropic or metabotopic.
inotropic- mechanoreceptor- pressure opens ion channel thermoreceptor- temperature influences a membrane protein that is a cation channel or is closely associated with the channel electroreceptor- an electric charge opens an ion channel metabotropic- chemoreceptor- a molecule binds to a receptor, initiating a signal that controls the ion channel via second messenger cascade photoreceptor- light alters a receptor protein, initiating a signaling cascade that controls an ion channel
25. Compare and contrast, in detail, iontropic receptors and metabotropic receptors.
inotropic- Also called a ligand - gated receptor No second messenger is involved Think ion = direct effect on channel specific quick response, only 1 response metabotropic- ligand bind to receptor, cause G protein to do something slower to act, more complex, allow varied responses, lasts slightly longer, activates second messenger that can do more
2. What are the major functions of the human nervous system?
receiving information about the environment around us (sensation) and generating responses to that information (motor responses)
14. Describe how a nerve is "bundled."
·Endoneurium surrounds each fiber ·Groups of fibers are bound into fascicles by perineurium ·Fascicles are bound together by epineurium
18. Which cell of the CNS is responsible for circulating cerebrospinal fluid in the major cavities of the brain and spinal cord?
·Ependymal cells ·Have cilia ·Line cavities of the brain and spinal cord ·Produce AND circulate cerebrospinal fluid (CSF)
20. Which type of ciliated cell lines the ventricles of the brain, producing and circulating CSF?
·Ependymal cells ·Have cilia ·Line cavities of the brain and spinal cord ·Produce AND circulate cerebrospinal fluid (CSF)
19. What is the function of microglia?
·Microglia ·Spider-like phagocytes ·Dispose of debris in areas of infection, trauma or stroke
21. Which cells form myelin in the PNS? Which cells form myelin in the CNS?
·Oligodendrocytes Produce myelin sheath around nerve fibers in the central nervous system ·Schwann cells ·Form myelin sheath in the peripheral nervous system
17. What is the function of satellite cells found in the PNS?
·Satellite cells ·Protect neuron cell bodies ·Schwann cells Form myelin sheath in the peripheral nervous system
31. What is the significance of "synaptic delay?" What type of synapse is synaptic delay not really an issue? Explain!
•A synaptic delay of 0.2-0.5 milliseconds occurs between: -arrival of action potential at synaptic knob -and effect on postsynaptic membrane •Rate limiting factor in transmission of a nerve impulse •Not as much of a factor in an electrical synapse -Allow ions to pass between cells -Produce continuous local current and action potential propagation -Are found in areas of brain (hypothalamus burst) and eye (visual adaptation)
23 j. Compare and contrast absolute refractory period and relative refractory period. Which one of these two is it possible for another action potential to occur?
•Absolute refractory period -as long as Na+ gates are open -NO stimulus will trigger AP •Relative refractory period -as long as K+ gates are open -only especially strong stimulus will trigger new AP •Refractory period is occurring only to a small patch of membrane at one time (quickly recovers)
27. What are the four types of neurotransmitters?
•Acetylcholine - formed from acetic acid and choline •Amino acid neurotransmitters •Monoamines •Neuropeptides
33. Diagram the excitatory cholinergic synapse. Make sure to include the role of acetylcholinesterase!
•Action Potential opens voltage-gated calcium channels in synaptic knob •Triggers release of ACh which crosses synapse •ACh receptors trigger opening of chemically ligand gated Na+ channels producing local potential (postsynaptic potential) •When membrane reaches threshold, triggers APin postsynaptic neuron
15. Explain the pathophysiology of Multiple Sclerosis (MS).
•Autoimmune Disease •Oligodendrocytes and myelin sheaths of CNS degenerate •Replaced by hardened scar tissue •Between 20-40 yrs •Double vision, blindness, speech defects, neurosis, tremors, numbness •Variable cycles until bedridden •No Cure
8. Axolemma = _?_
•Axolemma: -specialized cell membrane -covers the axoplasm
7. Axoplasm = _?_
•Axoplasm: -cytoplasm of axon -contains neurotubules, neurofibrils, enzymes, organelles
9. Axon collaterals = _?_
•Collaterals: -branches of a single axon
23 k. Describe the effect of the diameter of an axon on impulse transmission speed
•Diameter of fiber presence of myelin •large fibers have more surface area for signals •think of a larger diameter pipe having less resistance than a smaller pipe •Myelinated faster than unmyelinated
1. List AND describe the properties of neurons.
•Excitability (irritability) -ability to respond to changes in the body and external environment called stimuli •Conductivity -produce traveling electrical signals •Secretion -when electrical signal reaches end of nerve fiber, a chemical neurotransmitter is secreted
29. Compare and contrast the events related to IPSP's and EPSP's. In other words, what is happening on the postsynaptic cell with each of these?
•IPSP = inhibitory postsynatic potential -NT causes postsynaptic membrane to become more permeable to Potassium (moves out) OR Chloride (moves in) •EPSP = excitatory postsynaptic potential -NT causes opening of more ligand gated Sodium channels on postsynaptic membrane
23 l. Compare and contrast impulse transmission in an unmyelinated axon with impulse transmission in a myelinated axon. Make sure to use the term salutatory conduction in your response.
•Myelinated faster than unmyelinated •Fast Na+ diffusion occurs between nodes recharges AP at each node causing it to jump from node to node really fast - Saltatory Conduction
22. Describe the relationship of sodium and potassium concentrations inside and outside of the cell with the resting membrane potential.
•Na+ concentrated outside of cell (ECF) and leaks into ICF •K+ concentrated inside cell (ICF) and leaks into ECF •NET effect? Inner membrane becomes slightly negative. This is called resting potential and typically has a value of -90mv when the neuron is at rest
37. Diagram the GABA-ergic synapse. Make sure to include what ion is involved on the postsynaptic membrane.
•Nerve signal triggers release of GABA (g-aminobutyric acid) which crosses synapse •GABA receptors trigger opening of ligand gated Cl- channels producing hyperpolarization Postsynaptic neuron now less likely to reach threshold
3. Which are the two major types/groups of cells that make up nervous tissue?
•Neurons - The basic functional units of the nervous system - the communicators! •Supporting cells CNS (Central Nervous System) - neuroglia (glial cells) Astrocytes, microglia, ependymal cells, oligodendrocytes PNS (Peripheral Nervous System) - satellite cells, Schwann cells
40. Explain the role of MAO (Monoamine Oxidase) on neurotransmitters that have been reabsorbed into the presynaptic cell. What happens if this enzyme is blocked?
•Neurotransmitter is sometimes broken down into smaller pieces once it is taken back into the presynaptic neuron •Other times, the neurotransmitter is not broken down until it is taken back into the presynaptic neuron (reuptake) •An enzyme, monoamine oxidase breaks down many types of NT's •Some old antidepressant drugs (called MOAI's) inhibit this enzyme increasing availability of some NT's involved with depression
11.1. Synaptic terminals = _?_
•Synaptic terminals: -tips of axon
10. Axon telodendria = _?_
•Telodendria: -fine extensions of distal axon
12. What is myelin and what is its primary function?
•Whitish, fatty protein layer (20% protein and 80% lipid) •Serves to protect and electrically insulate axon •Increases the speed of transmission of nerve impulses (up to 150 times faster) •Only associated with axons, not dendrites •All myelination completed by late adolescence
23 i. Explain why an action potential is irreversible in terms of ion channels.
•irreversible (once started goes to completion and can not be stopped) ion channels open trigger an action potential at that note, propagates down axon, AP never gets weak over distance
