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A&P 2024 > Lecture 5/6 > Flashcards

Lecture 5/6 Flashcards

Exam 2

1
Q

How does the diameter of a nerve affect speed?

A

Larger diameter = faster
smaller=slower

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2
Q

How does length of nerve affect speed

A

Longer neuron = longer time, slower

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3
Q

Name of the insulation of the nerve

A

Myelin Sheath

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4
Q

How does myelination affect speed of a neuron?

A

Myelinated = faster
demyelinated = slower

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5
Q

What is the “Soma”?

A

neuron cell body

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6
Q

Where are dendrites located on a neuron and what are their function?

A

small branching projections off the soma
receive signals from other neurons

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7
Q

Where is the axon of a neuron and what is its function?

A

Long projection off the soma that sends signals

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8
Q

Where is the axon hillock and what is its function?

A

Area where the axon extends from the soma
functions to keep the brakes on the nervous system with GABA receptors

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9
Q

What is the name of the area on axon between myelination

A

node of ranvier

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10
Q

What cell forms the myelin sheath?

A

Schwann cell

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11
Q

Myelination allows ________ electrical propagation

A

faster

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12
Q

What is the term for the “jumping” of signals underneath the myelin sheath?

A

Saltatory conduction

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13
Q

How does extracellular Ca++ result in a calming effect on excitable cells?

A

Ca++ tries to enter Na+ leak channels, but too large to fit and blocks Na+ from leaking into the cell. The blocking of Na+ leak channels slows rate of depolarization, delaying AP from firing.

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14
Q

How does chloride affect the nervous system?

A

chloride puts the brake on the nervous system.

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15
Q

How would hypocalcemia affect cell excitability?

A

Cell would be more excitable. Vrm would be more + because cell becomes more permeable to Na+ because there is less Ca++ to block Na+ leak channels.

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16
Q

How many connexin to form a connexon?

A

6

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17
Q

How many connexons form a gap junction?

A

2

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18
Q

What is a connexon?

A

Formed of 6 connexin proteins, aligns with neighboring cell connexon which allows a channel for ions to move freely between the two cells. Allows for rapid conduction

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19
Q

What is a downside to gap junctions and what is an example?

A

movement of ions can go both ways, which can sometimes be bad.

ex. rogue pacemaker cells in the heart can fire signals in abnormal direction

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20
Q

What are the demyelinating disease examples given in lecture?

A

MS-multiple sclerosis
Optic Neuritis
Guillain-Barré (after COVID from antibodies)

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21
Q

What are some causes of demyelinating diseases?

A

genetics
infection
autoimmune (vaccines)
hyperactivity
polyneuropathies

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22
Q

Why does demyelination cause impaired signal firing?

A

Demyelination opens space that Na/K ATPase pumps can move and fill. VG Na+ and K+ channels don’t move/regenerate. So all the sodium ends up getting pumped out of the cell by the Na/K pumps stopping it from traveling further down the neuron

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23
Q

How does myelination speed up the rate of AP?

A

In the nodes on Ranvier, between the myelin sheaths, there is a high density of VG-Na and VG-K channels leaving little space for Na/K ATPase pumps. Not enough Na/K pumps to pump out the sodium, so the sodium travels to the next node to be pumped out, which causes the depolarization to continue down the axon.

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24
Q

What are supporting cells of the nervous system called?

A

Glial cells

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25
Q

What are the different types of glial cells?

A

CNS: oligodendrocytes
PNS: Schwann cells

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26
Q

which are better at regenerating? Schwann cells or oligodendrocytes?

A

schwann cells. the PNS is better at remyelinating than the CNS

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27
Q

Do myelinated neurons require more or less local anesthesia?

A

More

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28
Q

Gap junctions are an example of what type of cell signaling?

A

Direct coupling

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29
Q

Do all action potentials look alike?

A

No, some action potentials may take longer to reach threshold.
Stimulus strength may reach threshold faster and have larger initial spike.
Cardiac action potentials have a plateau phase

30
Q

What are the signs of hypocalcemia?

A
  • Trousseau sign - tetany of skeletal muscles
  • Chvostek sign
    (increased activity of motor neurons)
31
Q

How does calcium treat hyperkalemia?

A
  • If more [K+] in ECF → Vrm more (+)
  • Give Ca++ → blocks Na+ channels → decreases Vrm (-) back to normal
32
Q

What are the types of stimuli?

A

Sub-threshold, threshold, supra-threshold

33
Q

How does pressure affect action potential in pressure receptors?

A

Turns pressure into action potential to send back to the nervous system
Action potential depends on the amount of pressure: a lot of pressure - fast action potentials; little pressure - no or slow action potentials

34
Q

How do pressure receptors turn pressure into action potential?

A

Pressure → pressure sensitive Na channels get wider → Na+ enters cell → ICF (+) → action potential → nervous system

35
Q

______ is given for excessive depolarization in the heart

A

Mg2+
- reduces electrical activity
- smaller than Ca2+

36
Q

What affects how fast action potentials spread?

A
  1. Length of nerve (longer distance takes longer)
  2. Diameter of nerve (Wider = Faster; Less resistance)
  3. Insulation of the nerve (Myelin Sheath) - faster AP
37
Q

How do Schwann cells create myelination?

A

Schwann cell: grows and wraps itself in a spiral around neuron, each layer is compacted and water that was initially in the cell gets squeezed out → becomes good insulator once water is squeezed out (mostly lipid)

38
Q

What are the benefits of myelination?

A
  1. Decreases energy requirement (less Na/K+ pump ATP activity)
  2. speeds up action potential
39
Q

Nodes of Ranvier are dense in ________

A

Fast (V-G) Na+ channels

40
Q

________ prevents injury and ischemia of cells

A

Myelination

41
Q

Gap junctions communicate via simple diffusion of ions, primarily _____

A

Na+

42
Q

How do gap junctions work in the myocardium?

A
  • Has a lot of channels because wants action potential to spread quickly (low resistance)
  • Pacing system in heart has delays, or a pause from few gap junctions → higher resistance → harder to spread AP from one cell to another
43
Q

How do gap junctions work in the smooth muscle?

A

gap junctions that allow neighboring smooth muscles to act as a unit

44
Q

Chemical synapses take ______ than electrical synapses

A

longer

45
Q

Ach is _______ in the heart & _______ in the skeletal muscle

A

Inhibitory
Excitatory

46
Q

Chemical synapse requires a _______ connection between 2 cells

A

close
Presynaptic (sending) vs. postsynaptic (receiving) terminals

47
Q

What stimulates a nicotinic receptor?

A

binding of 2 ACh (acetylecholine)

48
Q

Where are nicotinic receptors located?

A

skeletal muscle

49
Q

Where are muscarinic receptors located?

A

heart, smooth muscle, lungs

50
Q

What type of receptor is the muscarinic receptor?

A

GPCR

51
Q

What type of channel is coupled with the muscarinic receptor?

A

K+

52
Q

The vagus nerve works through what kind of receptor?

A

muscarinic

53
Q

Does the muscarinic receptor cause polarization or depolarization?

A

polarization/hyperpolarization

muscarinic receptor when activated opens K+ channels that allow K+ to leave the cell, causing polarization

54
Q

How does muscarinic activity keep our HR in check?

A

HR if unchecked fires approx 100-110bpm. Vagus nerve constantly releasing ACh. Muscarinic activity decreases Vrm to make it take longer for AP to reach threshold, resulting in a lower HR.

55
Q

Why are they called muscarinic receptors?

A

They respond to a compound called “muscarine” found in the rainforest

56
Q

muscarinic receptors __________(increase or decrease) __________ permeability

A

increase K+ permeability
- activated by the alpha subunit on mACh-R

57
Q

Vagal stimulation causes our heart rate to increase or decrease? why?

A

decrease

Vagal stimulation causes increased ACh. ACh binds to muscarinic receptors which increase K+ permeability leading to hyperpolarization of pacemaker cells

58
Q

Antimuscarinic drugs increase or decrease heart rate? How?

A

Increase

blocks the binding of ACh on muscarinic receptors
decreases K+ permeability making Vrm more positive/depolarized.

59
Q

_______ is a common antimuscarinic drug

A

atropine

60
Q

______ opens chloride channels in neurons to hyperpolarize cells

A

GABA

61
Q

Propagation of an action potential can be a ______ process

A

2-way

62
Q

The ______ connects the end of the neuron and the receptor for neurotransmitters on the skeletal muscle

A

Neuromuscular junction (NMJ)

63
Q

nACh Channels/Receptors are specific for which ions?

A

(+) ions - mainly Na+ in; a little K+ can leak out, some Ca++ can enter ICF too
- net influx of (+) ions (depolarization) opens up fast Na+ channels

64
Q

Paralytics work at the _______

A

NMJ

65
Q

nACh channels are _______ electrical activity

A

stimulating; depolarization

66
Q

mACh-R channels are _______ electrical activity

A

suppressing; hyperpolarize

67
Q

Muscarinic receptors are found in the ____ of the heart

A

Nodes

68
Q

__________ come into contact with the pacing structures in the heart

A

Vagus nerves

69
Q

The _____ vagus nerve affects the SA node

A

Right

70
Q

The _____ vagus nerve affects the AV node

A

Left

71
Q

______ is the neurotransmitter that allows the vagus nerve to talk to the heart

A

ACh

72
Q

mACh-R antagonize ______ in the heart

A

Beta receptors

A&P 2024 (19 decks)

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