lecture 9- neurophysiology III

Question 1

a synapse=
and 2 types?

Answer 1

=the region where the neuron meets its target cell (neuron-neuron, neuron-muscle cell)

electrical synapse and chemical synapse

Question 2

electrical synapse

Answer 2

a gap junction where current flows directly from one cell to another

Question 3

what are gap junctions made of and what do they do?

Answer 3

gap junctions are made of connexin proteins

they allow for very rapid communication and synchronization of activity in a network of cells

Question 4

chemical synapse

Answer 4

electrical signals in the presynaptic cell are converted to a chemical signal for transmission to the postsynaptic cell

Question 5

explain how neurotransmitter is released at a synapse

Answer 5

an action potential depolarizes the axon terminal

the depolarization opens voltage gated Ca2+ channels and Ca2+ enters the cell

Ca2+ entry triggers exocytosis of synaptic vesicle contents

neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell

neurotransmitter binding initiates a response in the postsynaptic cell

Question 6

How is the stimulus (neurotransmitter) terminated?

Answer 6

when the chemicals are broken down, taken up into cells or diffuse away from the synapse

Acetylcholinesterase (ACh)= enzymatic breakdown of acetylcholine

Question 7

examples of neurotransmitters

Answer 7

Acetylcholine

Amines:
- norepinephrine, epinephrine

Amino acids:
-glutamate, aspartate, GABA, glycine

Question 8

what two things are stimulus intensity coded by?

Answer 8

frequency of AP firing and amount of NT released

Question 9

what is the action of excitation or inhibition dependent on?

Answer 9

depends on the transmitter molecule and the type of post synaptic receptor

Question 10

an excitatory post-synaptic potential (EPSP) is…

Answer 10

a depolarization

Question 11

an inhibitory post-synaptic potential (IPSP) is a

Answer 11

hyperpolarization

Question 12

two types of post-synaptic responses

Answer 12

Ionotropic

Metabotropic

Question 13

Ionotropic response=

Answer 13

fast, mediated by receptor channels

Question 14

metabotropic response=

Answer 14

slow, mediated by GPCRs

Question 15

two types of pathways

Answer 15

divergent pathway

convergent pathway

Question 16

divergent pathway

Answer 16

one presynaptic neuron branches to pass info to many downstream neurons

Question 17

convergent pathway

Answer 17

many presynaptic neurons send input to a smaller number of postsynaptic neurons

Question 18

presynaptic inhibition: 2 types

Answer 18

global presynaptic inhibition
= all targets of the postsynaptic neuron are inhibited equally

selective presynaptic inhibition
= an inhibitory neuron synapses on one presynaptic neuron and selectively inhibits one target

Question 19

synaptic diseases: one example

Answer 19

myasthenia gravis
= attacks neuromuscular junction between somatic motors and skeletal muscles

Question 20

symptoms of myasthenia gravis

Answer 20

muscle weakness, fatigue

caused by autoimmune-mediated decrease in acetylcholine receptors