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Clin. Neuro Class 2

QuestionAnswer
Name the parts of the neuron 1. body, soma, perikaryon 2. dendrites-may be apical or basal -spines 3. nucleus 4. Nissl substance (rough ER) 5. axon hillock 6. axon 7. myelin segments 8. nodes of Ranvier 9. synaptic ending, bouton, terminal 10. collaterals
What is located in the presynaptic terminal? 1. contains synaptic vesicles 2. large number of mitochondria 3. active zone
What is the active zone of the presynaptic terminal? where presynaptic membrane opposes postsynaptic membrane
What happens when the action potential reaches the presynaptic membrane? when action potential reaches presynaptic membrane synaptic vesicles fuse with membrane and release neurotransmitter into synaptic cleft
Where is the post synaptic site located? dendritic spine, dendrite, soma or axon
What is the motor endplate region? at neuromuscular junction axon branches and the postsynaptic region is on the muscle
Where are the receptors? postsynaptic membrane
What are receptors made of? Protein
How are receptors activated? may be activated either by a binding (ligand-gated) or by a local change in voltage (voltage-gated channel)
How does an ion channel regulate receptor activation? because of shape, size and/or charge only permit passage of one type of ion OR may be related to second messenger system
Ho does a second messenger system work? very complex and can change cell function by increasing neurotransmitter levels or number of receptors by activating gene expression. Can also cause prolonged opening of adjacent ion channels.
Where is the axon hillock? What happens here? 1. axon begins from soma 2. point of generation of the action potential
What is the size of an axon? few icrons to meters long
What is the function of the axon? transmit action potential to terminal, and can be myelenated or unmyelinated
Where is the action potential generated on a sensory neuron? action potentials are generated from receptors (modality gated)
Where is the action potential generated on a sensory neuron? peripheral and central segments of axon
T/F The cell body in dorsal root ganglion is unipolar. F, pseudounipolar
How does a cell membrane regulate membrane potential? ionic concentration
How is ionic concentration regulated? 1. phospholipid bilayer 2. ion channels
At rest what is the voltage potential inside vs. outside the cell? inside -65mV to -70mV
What is the range of voltage potential among neurons? -40 to -90
What concentration of ions give this voltage potential? 1. Na is relatively low in the cell 2. K is relatively high in the cell 3. CL is relatively low in the cell 4. Ca is very low relatively inside the cell
What maintains the Na and K concentrations inside and outside the cell? Sodium potassium pump
What would a diffusion gradient cause with Na in relation to K? would favor Na to flow in and K to flow out (pump maintains resting potential)
Start of the action potential a the synapse 1. neurotransmitter binds to receptor 2. causes ion channel to open 3. change in membrane permeability (flow of ions changes pot) 4. may become more neg (IPSP) or positive (EPSP) 5. graded- large or small 6. they can summate
What ions could the ion channel effect? Na, K, Ca, Cl
Where are action potentials generated? axon hillock
What happens when EPSPs summate to threshold? they can stimulate coltage gated Na and K channels to open
Which voltage gated channel responds more quickly? Causes what? 1. Na channels more quickly than K 2. rapid influx od Na
This influx of Na causese what? depolarization of the membrane up to +20 to +40
After the depolarization what happens? K channels open and repolarization occurs
How do Na and K return to normal? Na/K pump
What type of response is an action potential? all or none, stereotyped
What is an absolute refractory period? a second AP can't be generated
What is a relative refractory period? AP can be generated it the stimulus is of sufficient intensity
The increase in membrane potential causes what? conduction of the AP, the positive charge distributes along the adjacent membrane and causes voltage-gated channels in the adjacent membrane to open
What is the conduction velocity of AP? from 1-2 m/sec in unmyelinated axons to 70-120 m/sec in myelinated axons
What is saltatory conduction? the AP is propogated in a myelinated axon
What are the nodes of Ranvier? in myelinated axones these nodes have a high concentration of voltage gated Na channels
What is the effect of the nodes of Ranvier? this causes the AP to be thrust down the axon from node to node increasing conducting velocity
What factors influence the generation of an AP? 1. summation of postsynaptic potentials at axon hillock 2. distance of PSP to axon hillovk 3. PSPs on distal dendrites 4. PSPs summate over tiem and area 5. sum of inhib. or excit input 6. axo-axonic synapse (presynaptic inhibition
How does the distance of the PSP to axon hillock influence generation of AP? closer the greater the influence
PSPs on distal dendrites have more or less of an effect? less
Process of synaptic transmission? 1. AP reaches synaptic ending 2. voltage gated Ca open, Ca centers 3. synaptic vesicle binds to membrane 4. release neurotransmitter into synaptic cleft
Where are neurotransmitters synthesized? synaptic ending
Where does degradation of neurotransmitters occur? synaptic cleft, pre or post synaptic region or by glial cells
What is synaptic plasticity? The effect of synaptic transmission onthe postsynaptic neuron is not static, it can change overtime with repeated stimulation
How can synapses become more efficient and effective? 1. increased neurotransmitter production 2. creation of more post-synaptic receptors
How long will these plastic changes remain? long term and quasi-important
What neurotransmitter is used with a myoneural junction? acetyl choline
Where is the motor endplate? where synaptic ending releases transmitter into synaptic cleft to affect muscle
What is Myasthenia Gravis? autoimmune disorder, loss of strength with repeated contractions and recovery at rest
What causes myasthenia gravis? due to decreased number of Ah receptors available
What decreases the number of acetyl choline receptors antibody against receptors as part of autoimmune response
How common is myasthenia gravis? 1/10000 women>men
When does myasthenia gravis become life threatening? when it affects the respiratory muscles
What is the treatment anticholinesterase drugs and corticosteroids and other immunosupressant drugs
Name the four phases
Created by: 696592119