Neurotransmission

Question 1

Na+K+ depolarization and repolarization can be corrected ________.

Answer 1

Quickly

Question 2

The Na+K+ pump accounts for __% of the ATP requirement of the nervous system

Answer 2

70%

Question 3

Action potentials are propagated without _________ _______ and are _________.

Answer 3

Decreasing amplitude

Irreversible

Question 4

When are voltage-controlled Na+K+ pump channels are closed?

Answer 4

During the resting stage

When the current is -70mV

Question 5

What Na+K+ channels are always open?

Answer 5

Leakage channels

Question 6

What is the propagation rate of an unmyelinated fiber?

Answer 6

Up to 2m/s

Question 7

What kinds of responses are mediated by unmyelinated fibers?

Answer 7

Mediates slower, visceral responses

E.g. Secretion of stomach acid and the dilation of the pupils

Question 8

What is the propagation rate of a myelinated fiber?

Answer 8

Up to 120 m/s

Question 9

What kinds of responses are mediated by myelinated fibers?

Answer 9

Involved where speed is more important

E.g. motor to skeletal muscle, sensory signals for vision and balance

Question 10

In the cell, neurotransmitters are contained in?

Answer 10

Synaptic vesicles

Question 11

A synaptic vesicle contains how many molecules of this substance?

Answer 11

10,000 ACh (acetylcholine)

Question 12

Hos does ACh “leave” a synaptic vesicle? And what do the released molecules do?

Answer 12

ACh quickly diffuses out by exocytosis and crosses the narrow gap and binds to the receptor proteins in the postsynaptic membrane

Question 13

What is the refractory period?

Answer 13

A period of resistance to depolarization

Question 14

What is the absolute refractory period?

Answer 14

A period of no stimulation

Question 15

Why can’t the cell respond to stimulus during the refractory period?

Answer 15

The Na+ gates are open, so they cannot reopen as a response to a new stimulus

Question 16

What is the relative refractory period?

Answer 16

A time when only an unusually strong stimulus can depolarize the membrane to provide a new action potential
“Maybe” a signal can be sent -Beachy

Question 17

Why can signals be retransmitted during the relative refractory period?

Answer 17

The K+ gates are open, so an unusually strong stimulus can provide a new action potential

Question 18

What is EPSP?

Answer 18

Excitatory postsynaptic potentials
Any voltage change in a positive direction which makes a neuron more likely to fire
These are graded, not all-or-nothing

Question 19

What is summation?

Answer 19

A type of EPSP where the action potentials can be “added” together

Question 20

Where does EPSP occur?

Answer 20

In the axon hillock or “trigger zone”

Question 21

In EPSP what is “added up”?

Answer 21

Presynaptic potential

Question 22

What is temporal summation?

Answer 22

The signal hits the same place, one after another

A single synapse generates many EPSP

Question 23

What is spatial summation?

Answer 23

The signal hits different places at the same time

EPSP come from several different synapses at the same time

Question 24

What is IPSP?

Answer 24

Inhibitory Postsynaptic Potentials

A hyperpolarizing of the postsynaptic membrane

Question 25

What happens to the cell membrane in IPSP?

Answer 25

Membrane is more negative, so it’s less likely to fire

Question 26

What molecules, and by what mechanism, does IPSP occur?

Answer 26

GABA and glycine both open chloride gates, so chloride ions flow in and hyperpolarize the postsynaptic membrane

Question 27

What is presynaptic inhibition?

Answer 27

1 presynaptic neuron suppresses another presynaptic neuron

Question 28

What is a neuromodulator?

Answer 28

Chemical messengers that have long-term effects on entire groups of neurons

Question 29

What is substance P?

Answer 29

Facilitates transmission of pain signals to the brain

Question 30

What is an endorphin?

Answer 30

Inhibits transmission of pain signals to the brain

Question 31

What are the two categorizations of axonal transport?

Answer 31

Slow and fast

Question 32

What is slow axonal transport?

Answer 32

0.5-10 mm/day, anterograde only | Transport from soma (cell body) to end bulb only

Question 33

What is fast axonal transport?

Answer 33

200-400 mm/day, both anterograde and retrograde

Question 34

What are two pathogens that attack humans via axonal transport?

Answer 34

tetanus: Bacterium, toxin from bacterium travels retrograde rabies: virus, travels up axon (retrograde)

Question 35

What is the difference between flaccid and spastic paralysis?

Answer 35

Flaccid paralysis: eg loose arm | Spastic paralysis: ex rigid arm

Question 36

What is curare?

Answer 36

Arrowhead poison used in South America to hunt

Question 37

How does curare affect the body?

Answer 37

Blocks ACh receptors in muscle (mirrors ACh) | Flaccid paralysis in resp muscles, then death

Question 38

Is curare pre or postsynaptic?

Answer 38

Postsynaptic

Question 39

What is botulism?

Answer 39

Food poising caused by the botulin bacterium | Is the most potent known microbial toxin

Question 40

How does botulism affect the cell? And what kind of paralysis does it result in?

Answer 40

Blocks release of ACh @ presynaptic membrane | Flaccid paralysis

Question 41

What is polio?

Answer 41

A virus destroys the motor neurons

Question 42

Does polio result in flaccid or spastic paralysis?

Answer 42

Flaccid paralysis

Question 43

What is tetrodotoxin?

Answer 43

Founnd in the skin and some organs of the puffer fish

Question 44

What is the mechanism of tetrodotoxin?

Answer 44

A highly specific Na channel blocker. | Nerve fiber cannot generate and propagate an action potential

Question 45

Is tetrodotoxin pre or postsynaptic? What kind of paralysis does it cause?

Answer 45

Postsynaptic | Flaccid paralysis

Question 46

What is tetanus?

Answer 46

Toxin is tetanospasmin

Question 47

What is the mechanism of tetanus?

Answer 47

Toxin blocks glycine release and this causes overstimulation (hyperpolarization)

Question 48

What kind of paralysis comes from tetanus?

Answer 48

Spastic paralysis

Question 49

What is MG?

Answer 49

Myasthenia gravis | Autoimmune disease of generalized muscle weakness

Question 50

What is the mechanism of MG?

Answer 50

Muscle fibers become less and less susceptible to ACh

Question 51

Is MG pre or postsynaptic?

Answer 51

Postsynaptic (the receptors on muscle fibers are destroyed)

Question 52

What is used to treat MG and how does it work?

Answer 52

Use cholinesterase inhibitors to inhibit AChE, in the hope that more ACh can stimulate`

Question 53

What is MS?

Answer 53

Multiple sclerosis Degenerative disorder of myelin sheaths Breakdown of myelin in CNS, replaced with hardened scar tissue

Question 54

MS is a ________ disease which results in the loss of ______ function over time.

Answer 54

Progressive | Nerve

Question 55

What are some symptoms of MS?

Answer 55

Doublevision, blindness, speech defects, tremors and numbness

Question 56

What kind of synapse uses ACh?

Answer 56

Cholinergic

Question 57

What kind of synapse uses NE?

Answer 57

Adrenogenic