Neurophys Review Part 1

Question 1

What are the main differences between electrical and chemical synapses?

Answer 1

• Electrical synapses propagate a signal using gap junctions (connexon) as opposed to NTs.
• Electrical are comparatively rare
• electrical are dendro-dendritic (mostly)

Question 2

What passes through gap junctions?

Answer 2

All ions

Question 3

What is the function of the pre-synaptic process (axon)?

Answer 3

Provides neurotransmitter

Question 4

What is the function of the post-synpatic process

Answer 4

To translate the neurotransmiatter into a useful signal (depolarization)

Question 5

What is the role of astrocytes?

Answer 5

Astrocytes are a type of glia that provide metabolic support to neurons and may modulate synaptic function

Question 6

What are the proteins that form the SNARE complex?

Answer 6

1. synaptobrevin
2. syntaxin
3. synaptotagmin
4. SNAP-25

Question 7

Give the sequence of events of the vesicle docking

and synaptic transmission.

Answer 7

1. vesicle docks
2. entering Ca++ binds to synaptotagmin
3. SNARE complexes form to pull PS membrane to vesicle membrane
4. Ca++ bound to synaptotagamin catalyzes membrane fusion by binding to SNARES/plasma membrane

Question 8

What chemical is used clinically and interferes with SNARE formation?

Answer 8

Botulinim toxin (Botox)

Question 9

Each neuron releases how many neurotransmitters?

Answer 9

ONE

*but some also release a peptide in addition to the primary NT

Question 10

What are the amino acid NTs?

Answer 10

glutamate

aspartate

GABA

glycine

Question 11

What are the catecholamine neurotransmitters?

Answer 11

dopamine

norepinephrine

epinephrine

*part of larger biogenic amine class

Question 12

What channel is defective in inherited Long QT Syndrome?

Answer 12

K+ Channel

Question 13

What channel type is defective in cystic fibrosis?

Answer 13

Cl-

Question 14

What effect does GABA have on the post-synaptic cell?

Answer 14

hyperpolarizes it

Question 15

How do GABAb receptors modulate Ca++?

Answer 15

They are located on the pre-synaptic terminals and when activated by NT, cause reduced Ca++ influx, thereby reducing the amount of NT released.

Question 16

What receptor type will additionally allow Ca++ into the cell under the right conditions?

Answer 16

NMDA

Question 17

Memantine is a drug used for _______ patients and acts by antagonizing ________receptors.

Answer 17

Alzheimer’s; NMDA

*reduces glu/Ca2+ in cell

**works in about 1/3 of patients

Question 18

What are the 3 major factors responsible for the uneven distribution of ions across the neuronal membrane?

Answer 18

1. selective permeability
2. large organic anions within the cytoplasm
3. ion pumps (Na+/K+ ATPase)

Question 19

What is the ratio of the Na+/K+ ATPase?

Answer 19

3:2

*net outward current causes small hyperpolarization

Question 20

What is the reversal potential for K+?

Answer 20

about -85 mV

Question 21

What is the reversal potential for Na+

Answer 21

about +57 mV

Question 22

What channels are mutated in Epilepsy ?

Answer 22

K+ and nicotinic

Question 23

What channels are mutated in Hyperekplexia?

Answer 23

Glycine

Question 24

What is the mechanism of action of lidocaine?

Answer 24

Blocks Na+ channels and has some specificity for inhibitory neurons (blocks pain neurons)

Question 25

What channels open first in the action potential?

Answer 25

voltage-gated Na+

Question 26

What is the "information code" transmitted from neuron to neuron?

Answer 26

the pattern of action potentials

Question 27

What are the spaces between myelin cells on a neuron called?

Answer 27

Nodes of ranvier

Question 28

Conduction along a myelinated axon differs from an unmyelinated axon in what respect?

Answer 28

It is saltatory - it "jumps" from node to node

Question 29

If an injected current does not reach threshold for a neuron, what happens?

Answer 29

Nothing (In other words, an EPSP must reach threshold to get an action potential)

Question 30

What is hyperkalemia?

Answer 30

elevated serum K+ usually caused by kidney dysfunction \*leads to depolarization of membrane

Question 31

What happens during hyperkalemia that causes irregular cardiac rhythms and skeletal muscle weakness?

Answer 31

The membrane of neurons depolarize slowly (seconds) or have sustained depolarization, leading to so many Na+ channels being deactivated, no AP can occur

Question 32

What gate opens first on Na+ voltage-gated channels?

Answer 32

M gate depolarizing phase

Question 33

What gate closes to de-activate Na+ voltage channels and when?

Answer 33

H gate at the top of the depolarizing phase

Question 34

When does the K+ voltage-gated channel open?

Answer 34

at the top of the depolarizing phase (n gate)