Cell Transport, Action Potentials and Neuromuscular

Question 1

What are the 3 types of sensory information provided by muscle spindles and Golgi tendon organs?

Answer 1

1) speed (velocity) and the size of muscle length change
2) muscle position - proprioception
3) muscle tension

Question 2

What structures have sensory nerve endings wrapped around itself which send sensory info when the muscle contracts?

Answer 2

intrafusal fibers

Question 3

Sensory info goes in which horn of the spinal cord?

Answer 3

dorsal

Question 4

The sensory info sent through the dorsal horn of the spinal cord is sent of what cortex of the brain?

Answer 4

primary somatosensory cortex

Question 5

Where are primary motor neurons housed in the brain?

Answer 5

primary motor cortex

Question 6

Which horn of the spinal cord do primary motor neurons send through?

Answer 6

ventral horn

Question 7

primary motor neurons send motor information to what neurons in the muscle fiber?

Answer 7

alpha motor neurons

Question 8

primary somatosensory cortex sends information to what part of the brain?

Answer 8

primary motor cortex

Question 9

Function of dendrites

Answer 9

receive information as chemical signals - neurotransmitters

Question 10

When enough of the chemical signals accumulate at the dendrite, it causes the cell membrane to reach threshold and become what kind of signal?

Answer 10

electrical signal

Question 11

Once threshold has been reached, the electrical signal is transmitted down what part of the neuron?

Answer 11

Axon

Question 12

What must happen at the axon hillac of the neuron before an action potential can fire?

Answer 12

cell membrane must reach a threshold level at the axon hillac

Question 13

What type of cells make up the myelin sheath around the axon?

Answer 13

swchann cells

Question 14

What system are schwann cells unique to?

Answer 14

peripheral

Question 15

Where in the neuron does the electrical signal become chemical again?

Answer 15

Axon terminal (terminal bud)

Question 16

Typical membrane resting potential?

Answer 16

-80 to 90 mV

Question 17

What is an unequal distribution of ions across the membrane?

Answer 17

membrane potential

Question 18

Is the outside of the cell positive or negative with respect to the inside?

Answer 18

outside - positive

inside - negative

Question 19

What creates the membrane potential?

Answer 19

concentration gradient

Question 20

Why is the outside of the cell more positive?

Answer 20

Sodium potassium pump pumps out of the cell 3 sodium ions for every 2 potassium ions that diffuse into the cell

Question 21

Where is diffusion allowed to happen across the axon?

Answer 21

Nodes of Ranvier

Question 22

What ion is more permeable to the cell membrane?

Answer 22

potassium

Question 23

What creates the concentration gradient?

Answer 23

sodium potassium pump

Question 24

What is known as the force of the ion wanting to diffuse down an electrochemical gradient?

Answer 24

Nernst Potential (Diffusion potential)

Question 25

When there is lots of a positive ion inside the cell, what is the Nernst potential?

Answer 25

negative (when inside the cell, sign is opposite of ion)

Question 26

If there is a positive ion outside the cell, what is the Nernst potential?

Answer 26

positive (when outside the cell, sign is the same as the ion)

Question 27

Why is potassium diffusion potential higher inside the cell?

Answer 27

Because it is more permeable to the cell membrane and continuously wants to go down its concentration gradient outside the cell

Question 28

Is potassium’s diffusion potential higher or lower inside the cell?

Answer 28

Higher

Question 29

Is the sodium’s diffusion potential higher or lower outside the cell? Why?

Answer 29

Higher; sodium has a strong drive to diffuse inside the cell

Question 30

What is the resting membrane potential for motor neurons?

Answer 30

-50mV to -80mV

Question 31

What is known as the means by which nerve signals are transmitted and cause rapid changes in local membrane potential?

Answer 31

Action Potentials

Question 32

What must be reached to discharge an action potential across the entire cell?

Answer 32

Threshold

Question 33

the 3 stages of action potentials?

Answer 33

1) depolarization
2) repolarization
3) refractory period

Question 34

What occurs during depolarization?

Answer 34

• membrane becomes suddenly very permeable to sodium
• sodium rushes into the cell, creating a more positive membrane potential
• influx of sodium causes threshold to be reached, allowing the opening of 2nd voltage gated sodium channels

Question 35

What occurs during repolarization?

Answer 35

• sodium channels close via inactivation gate
• this causes an opening of voltage-gated potassium channels
• rapid diffusion of potassium OUT of the cell
• Membrane potential returns to resting (negative)

Question 36

What occurs during hyperpolarization?

Answer 36

• potassium gates are slow to close so extra potassium travels outside the cell, making the membrane potential even more negative than RMP

Question 37

What is considered threshold for AP?

Answer 37

-55 mV

Question 38

What occurs during the refractory period?

Answer 38

• period where a new AP cannot be initiated until the RMP has been restored

Question 39

What is the period in which no amount of excitatory signal will open sodium gated channels due to them being inactivated?

Answer 39

Absolute Refractory Period

Question 40

What is the period in which only a strong stimulus will create an AP due to the inactivation gates opening slowly?

Answer 40

Relative Refractory Period (some sodium gates re-open and some potassium gates still open)

Question 41

Are nerve action potentials unidirectional or bidirectional?

Answer 41

unidirectional

Question 42

Are skeletal muscle action potentials unidirectional or bidirectional?

Answer 42

bidirectional

Question 43

Action potentials will continue to propagate down the cell membrane until what occurs?

Answer 43

until the entire cell membrane becomes depolarized

Question 44

What is it called when AP jumps from node to node?

Answer 44

Saltatory conduction

Question 45

Once the action potential reaches the terminal axon bud, it opens what kinds of channels that release what, in order to release the neurotransmitter into the synaptic cleft?

Answer 45

opens voltage-gated calcium channels, allowing calcium to rush in and stimulate the release of neurotransmitter into the synaptic cleft

Question 46

What is the junction called where the axon nerve ending and muscle fiber meet?

Answer 46

Neuromuscular junction (NMJ)

Question 47

The axon ending dives into the sarcolemma of the muscle cell to create what?

Answer 47

synaptic cleft

Question 48

In the NMJ, what kind of receptors do the acetylcholine bind to in the postsynaptic sarcolemma?

Answer 48

cholinergic receptors

Question 49

Binding of AcH stimulates what in the muscle cell?

Answer 49

stimulates a conformational change and the opening of sodium channels, allowing an influx of sodium into the cell

Question 50

Influx of sodium into the muscle cell creates what at the sarcolemma, which results in what?

Answer 50

end-plate potential, resulting in activation of voltage-gated sodium channels, propagating an AP on the sarcolemma down the t-tubules, causing a massive calcium release into the myofibrils, needed for stimulation of muscle contraction