Membrane Potentials and Action Potentials

Question 1

What is the Nerst equation?

Answer 1

used to determine the electrical potential of a cell membrane in regards to one type of ion Nernst potential = 61 Log C intra/C extra

Question 2

What is the resting membrane potential in large myelinated peripheral nerves and skeletal muscle?

Answer 2

-90 mV

Question 3

The resting membrane potential is determined largely by which ion?

Answer 3

K+

Question 4

What is the resting membrane potential in the soma of the neuron?

Answer 4

-65 mV

Question 5

What is the resting memebrane potential in small nerve fibers and smooth muscle?

Answer 5

-55 mV

Question 6

How is the resting membrane potential maintained?

Answer 6

leaky K+ channels (potassium is -94 mV and 100 times more permeable than sodium)

Question 7

In the action potential pathway, what is the sequence for ion channel opening?

Answer 7

Question 8

What is the mechanism of tetrodotoxin?

Answer 8

voltage gated Na+ channel blocker

Question 9

What is the mechanism of Tetraethylammonium (TEA)?

Answer 9

voltage gated K+ channel blocker

Question 10

What neurotransmitter and what ion are associated with presynaptic inhibition?

Answer 10

GABA and Cl-

Question 11

In what synapses is ACh used as a neurotransmitter?

Answer 11

• motor cortex
• skeletal muscle
• preganglionic autonomic nerves
• postganglionic parasympathetic nerves
• postganglionic sympathetic nerves for sweat glands

Question 12

In what synapses is Norepi used as a neurotransmitter?

Answer 12

• pontine locus ceruleus
• postganglionic sympathetic nerve fibers

Question 13

Is dopamine excitatory or inhibitory? In what synapses is Dopamine used as a neurotransmitter?

Answer 13

inhibitory

substantia nigra projections to the putamen and caudate

Question 14

What is the rate limiting step in dopamine synthesis?

Answer 14

conversion of tyrosine to 3,4 DOPA by tyrosine hydroxylase

Question 15

Is glycine excitatory or inhibitory? In what synapses is glycine used as a neurotransmitter?

Answer 15

inhibitory

spinal cord (Renshaw cells)

Question 16

In what synapses is GABA used as a neurotransmitter?

Answer 16

• cortex
• basal ganglia
• cerebellum (Purkinje Cells)
• spinal cord

Question 17

Is glutamate excitatory or inhibitory? In what synapses is glutamate used as a neurotransmitter?

Answer 17

Excitatory

• cortex
• dentate gyrus of hippocampus
• striatum
• cerebellum (granular cells)

Question 18

Is serotonin excitatory or inhibitory? In what synapses is serotonin used as a neurotransmitter?

Answer 18

inhibitory

• Median raphe nuclei that project to the hypothalamus and spinal cord (dorsal horns)

Question 19

What neurotransmitter serves as the precursor to melatonin?

Answer 19

Serotonin

Question 20

Where are nicotinic receptors located?

Answer 20

• NMJ
• preganglionic sympathetics and parasympathetics

Question 21

What are the subunits of the autonomic nicotinic receptor?

Answer 21

2 alpha, one beta, one gamma, and one delta

Question 22

Which subunit on the nicotinic autonomic receptor binds the ACh?

Answer 22

the alpha subunit

Question 23

What blocks the ACh binding receptor on the nicotinic autonomic receptor?

Answer 23

hexamethonium (not reversed by acetacholinesterase)

Question 24

What are the subunits of nicotinic receptors at the NMJ?

Answer 24

2 alpha subunits

Question 25

Where are muscarinic receptors located?

Answer 25

- postganglionic parasympathetic - postganglionic sympathetics for sweat glands

Question 26

What intracellular messaging system is paired with muscarinic receptors?

Answer 26

G protein via second messahnger system

Question 27

Muscarinic receptors are blocked by what toxin?

Answer 27

pertussis toxin

Question 28

What messenger system is used by dopamine receptors?

Answer 28

cAMP second messenger

Question 29

What is the competitive antagonist of glycine receptors?

Answer 29

Strychnine

Question 30

Mutations in what receptor causes stiff person syndrome?

Answer 30

mutations in glycine receptor (loss of inhibition)

Question 31

GABA A receptors increase _______ permeability; GABA B receptors increase _______ conductance.

Answer 31

Cl- K+

Question 32

What are the GABA A agonists? What is their function?

Answer 32

Barbituates (prolong duration of Cl - opening) and Benzodiazepines (increase frequency of Cl- opening)

Question 33

What are GABA B agonists?

Answer 33

Baclofen

Question 34

What toxin blocks GABA receptor activity? What is the clinical manifestation?

Answer 34

Picrotoxin Causes seizure like activity

Question 35

NMDA receptors use what type of neurotransmitter?

Answer 35

Glutamate (requires glycine for coactivation)

Question 36

What blocks NMDA receptors?

Answer 36

Magnesium

Question 37

Kinesin mediates _________ and dynein mediates \_\_\_\_\_\_\_\_.

Answer 37

anterograde axonal transport retrograde axonal transport

Question 38

Excitatory action potentials lead to _____ channels opening while inhibitory action potentials lead to _____ channels opening.

Answer 38

NA+ K+ and Cl-

Question 39

Action potentials start at the _______ due to \_\_\_\_\_\_.

Answer 39

Neuronal axon hillock Higher concentrations of Na+ channels