Nervous Sytem VI

Question 1

What are the two categories of neurocrine receptors?

Answer 1

Ionotropic and metabotropic receptors

Question 2

What are ionotropic receptors?

Answer 2

Ligand gated ion channels
- ligand binding to ionotropic receptors causing conformational change leading to opening of channel
- can be specific for ion or non-selective

Question 3

What kind of postsynaptic response do ionotropic receptors mediate?

Answer 3

Fast (neurotransmitter)

Question 4

What are metabotropic receptors

Answer 4

G-protein coupled receptors
- cytoplasmic tail of receptor linked to 3 part transducer protein (G-protein)

Question 5

What kind of response to metabotropic receptors mediate?

Answer 5

Slower (neuromodulators)

Question 6

What 2 g-protein mediated cell responses happen in result of ligand binding to metabotropic receptor?

Answer 6

1. Interact directly with ion channels
   
   • can lead to opening or closing
2. Interaction with a membrane bound enzyme
   
   • phospholipase C signal transduction pathway
   • adenylyl cyclase signal transduction pathway

Question 7

Can a neurocrine have slow and fast responses?

Answer 7

Same neurocrine can act as neurotransmitter or neuromodulator depending on receptor present on postsynaptic cell

Question 8

Where are neurotransmitters released from?

Answer 8

Vesicles containing neurotransmitters accumulate in axon terminal

Question 9

What is neurotransmitter synthesis?

Answer 9

Large peptide neurotransmitters are produced and packaged into vesicles at the soma and transported with fast axonal transport
Small ones are synthesized and packaged at axon terminal

Question 10

How does neurotransmitter release happen?

Answer 10

Occurs via Ca2+ mediated exocytosis
High concentration of voltage gated calcium channels at pre-synaptic terminal

Question 11

Termination of neurotransmitter activity?

Answer 11

1. Nts return to axon terminals for reuse or transported into glial cells
2. Enzymes inactivate nts
3. Nts can diffuse out of synaptic cleft

Question 12

What releases more neurotransmitter?

Answer 12

A stronger stimuli, increased AP firing leads to greater influx of Ca2+ and increased neurotransmitter release

Question 13

What are 2 types of synaptic integration?

Answer 13

Convergence and divergence

Question 14

What is convergence?

Answer 14

Presynaptic neurons converge on one or a small number of postsynaptic neurons

Question 15

What is divergence?

Answer 15

Neurons can have branching axons that contact many different postsynaptic neurons

Question 16

What is integration of synaptic signaling?

Answer 16

Input from multiple presynaptic neurons converging on a single postsynaptic cell is summated to determine the output

Question 17

What is spatial summation?

Answer 17

Spatial= different locations
Occurs when the currents from multiple simultaneous graded potentials combine to create suprathreshold signal- create AP

Question 18

Why can spatial summation be inhibitory?

Answer 18

Efflux of K+
One inhibitory and 2 excitatory neurons fire and sum is below threshold

Question 19

What is temporal summation?

Answer 19

Two graded potential from one presynaptic neuron occur close together in time and sum and initiate AP

Question 20

What is presynaptic modulation?

Answer 20

Excitatory or inhibitory neurons may synapse on synaptic terminals and augment communication between pre and postsynaptic cell

Question 21

What is presynaptic inhibition?

Answer 21

Inhibits neurotransmitter release

Question 22

What is presynaptic facilitation?

Answer 22

Increase neurotransmitter release

Question 23

What is global presynaptic inhibition?

Answer 23

All targets cells don’t get stimulated and entire neuron is inhibited

Question 24

What is selective presynaptic inhibition?

Answer 24

Inhibitory neuron synapses one one of neurons so inhibitions happens are one target and other are unaffected

Question 25

What happens in postsynaptic modulation?

Answer 25

Strengthening or weakening of synapses due to changes in receptor expression on post synaptic
- changing structure, affinity or number of neurotransmitter receptors