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Organ Systems > Part 7 > Flashcards

Part 7 Flashcards

0
Q

describe the function of a Cell body ?

A

Genetic and metabolic machinery for neurotransmitter synthesis. necessary for a cell to exist.

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1
Q

what are the structural features of a neuron?

A

Cell body, Axon, Dendrite, synapse

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2
Q

what is the function of an Axon?

A

propagates action potential

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3
Q

describe a dendrite?

A

filamentous extensions of cell body

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4
Q

what is a synapse?

A

axon terminal

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5
Q

what are cell bodies called in the CNS and PNS?

A

CNS - Nucleus

PNS - Ganglion

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6
Q

what are axons called in the CNS and PNS?

A

CNS - tract

PNS - nerve

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7
Q

all neurons in the PNS are surrounded by ?

A

Glia (Schwann Cells)

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8
Q

Gaps between Schwann Cells are called?

A

Nodes of Ranvier

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9
Q

4 Types of connective tissue surrounding nerves ?

A

Epineruium
perineurium
endoneurium
basement membrane

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10
Q

Epineurium ?

A

surrounds the whole nerve

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11
Q

Perineurium ?

A

surrounds fascicles of nerve fibers

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12
Q

endoneurium ?

A

surrounds individual axons

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13
Q

Basement Membrane ?

A

protein matrix secreted by Schwann cells

• forms a protein interface between Schwann cells and endoneurium

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14
Q

Nerve Fascicles ?

A

Bundles of axons that target single muscles or skin regions

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15
Q

Nervi Nervorum ?

A

bundles of axons that innervate CT layers of nerves

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16
Q

Vasa Nervorum?

A

Blood vessels to CT, axons and Glia in nerves

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17
Q

What is Neuropathy ?

A

Neural disease due to damage to axons or glial cells

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18
Q

What are some common causes of Neuropathy ?

A

Diabetes, kidney failure, alcoholism, nutritional deficiency, trauma,auto immune disease.

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19
Q

How does Axonal degeneration progress?

A

damage begins at the hands and feet distally and moves proximally

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20
Q

Explain demyelination

A

degeneration of glia and the unwinding of myelin sheaths around axons

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21
Q

what is Guillain-Barre ?

A

Demyelination of motor fibers due to an autoimmune response to infection, surgery or immunization

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22
Q

What is Multiple Sclerosis?

A

demyelination disease in the CNS

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23
Q

what is paresthesia ?

A

burning or tingling (pins and needles) feeling due to neuropathy

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24
Q

what is hyperalgesia ?

A

exaggerated pain response to normally painless stimuli

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25
Q

Explain sprouting in relation to Nerve regeneration

A

Branching by axon proximal to injury.

Basement membrane tunnels, created by Schwann cells, guide axons, using laminin.

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26
Q

What is Laminin?

A

neurite promoting glycoprotein, component of the basement membrane that is increased on the surface of schwann cells

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27
Q

Whats the speed of Axon regrowth for PNS and CNS?

A

PNS - 1mm/day

CNS - minimal due to lack of basement membrane

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28
Q

Gray matter is made up of ?

A

H shaped region of cell bodies dendrites and axons

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29
Q

why is White matter ‘White’?

A

myelin, glial cells surround many axons making it look ‘white’

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30
Q

rootlets extend out from ?

A

dorsal and ventral horns and converge into roots

31
Q

dorsal and ventral roots exit the vertebral column and unite to become ?

A

the spinal nerve

32
Q

Spinal nerve splits into two rami?

A

Dorsal and Ventral rami (aka Peripheral nerves)

33
Q

Where is the cell body found in the sensory neurons and motor neurons?

A

Sensory neuron - Dorsal root ganglion

Motor neuron - Ventral horn

34
Q

sympathetic neurons are found in nearly all nerves. they have two types of cell bodies

A

preganglionic - found in gray matter, projects axon to sympathetic ganglion
postganglionic - forms sympathetic ganglion, projects axons to periphery.

35
Q

this membrane constituent can increase permeability to water soluble molecules and stiffens membranes to help form lipid rafts

A

cholesterol

36
Q

types of membrane proteins?

A

transmembrane (alpha helix, beta barrel)
membrane associated
lipid linked
protein attached

37
Q

what are the benefits to carbohydrates connecting transmembrane proteins to the ECM?

A

carbohydrates bind lectins which mediate cell-cell adhesions

ex. blood clotting and inflammation.

38
Q

the most common transmembrane protein that crosses the membrane bilayer?

A

alpha helix

39
Q

the alpha helix can make multiple crossings or a single crossing across the membrane, explain the difference?

A

multiple crossings - create a pore used as an ion channel

single crossing- acts as a signal receptor

40
Q

Ion specificity of a channel depends on ?

A
  • charge distribution: positive channel will only allow negative through.
  • diameter and shape of channel: (size of ion is determined more by hydration shell than size of atom)
41
Q

what causes the sodium potassium pump to alter conformation?

A

donation of phosphate by ATP

42
Q

membrane polarization created by a single ion is known as?

A

equilibrium potential

43
Q

this potential is generated by the net flux of all ions?

A

membrane potential (Vm)

44
Q

product of net driving force and permiability

A

net flux

45
Q

sum of concentration and electrical gradients

A

net driving force

46
Q

ease of flux through a channel

A

permeability

47
Q

this ion has a high net flux, high permeability and concentration and electrical gradients are in opposite directions, reducing net driving force.

A

K+

48
Q

this ion has a low net flux, low permeability and concentration and electrical gradients are in the same directions, increasing net driving force.

A

Na+

49
Q

3 types of ion gaiting properties ?

A

Voltage gated
ligand gated
mechanically gated

50
Q

Voltage gated ion channels are located at ? and work by ?

A

Location : axion hillock and nodes of Ranvier

stimulus : de/hyper polarizing current which changes conformation and permeability

51
Q

ligand gated ion channels are located at ? and work by ?

A

location: neural or other cell surfaces
stimulus: neurotransmitters, ligands

52
Q

mechanically gated ion channels are located at ? and work by ?

A

location: skin, retina..etc

stimulus : pressure, touch, light..

53
Q

Receptor Stimulus increases Na+ permeability yielding?

A

a graded depolarization of the membrane potential

54
Q

At what location does the triggering of the all or none action potential take place?

A

nodes of Ranvier

55
Q

what mechanism causes the all or none action potential at the nodes of Ranvier?

A

influx of Na+ ions from the receptor potential depolarizes and opens Na+ gated ion channels.

56
Q

briefly explain the 4 phases of action potential

A
  • Incoming positive ionic current depolarizes membrane to threshold level of voltage.
  • At threshold, rapid depolarization to positive value,~50mV (Na)
  • Repolarization to initial potential
  • Hyperpolarization, ~-70mV (K)
57
Q

what happens during depolarization?

A

Na channel opens in response to depolarization (at threshold)
• Potential almost reaches +50mV (Na)

58
Q

what causes repolarization?

A

Na channel spontaneously inactivates

• K channels opens

59
Q

what happens during hyperpolarization

A
  • K channel still open; K flux happens through both leak & volt-gated channels
  • Potential almost reaches >-70mV (K)
60
Q

what type of channels do not participate in action potentials?

A

non gated, leakage K+ channels

61
Q

internal depolarization causes the protein configuration to?

A

open the outer portion of the channel

62
Q

initial depolarization and overshoot is strong because ?

A

Na influx has a high driving force

63
Q

why does Na+ have a high driving force?

A

both concentration and electrical gradients are in the same direction and summate.

64
Q

what is excitability?

A

sensitivity of the cells ability to produce an action potential

65
Q

what two variables can alter excitability?

A

– Concentration gradient
– Channel permeability and/or threshold
potential

66
Q

how does hyperkalemia (increasing extracellular K+ level) affect concentration gradient?

A

causes prolonged depolarization, Na+ channels are inactivated, the threshold is raised and the cell becomes less excitable.
• Decreasing extracellular K+ has reverse effect

67
Q

channel permeability can be altered by ?

A

channel blocking and protein reconfiguration. (lidocaine is an example of channel blocking)

68
Q

describe the refractory period

A

only happens in unmyelinated axons. the period of time after an action potential during which the membrane channels are less responsive to stimuli

69
Q

whats the difference between an absolute refractory period and a relative refractory period?

A

Absolute - channels cannot be activated

relative - takes a greater stimulus to create action potential.

70
Q

describe conduction in a myelinated axon.

A

AP’s are only produced in nodes of Ranvier and the axon hillock because this is where the voltage-gated channels are.

71
Q

What is Saltatory conduction?

A

refers to the skipping of AP generation from one node to the next.

72
Q

Why does amplitude decrease along a myelinated area of an axon?

A

because current leaks out through non-gated K+ channels.

73
Q

demyelination occurs due to Guullian - barre and MS, what does this due to conduction

A

conduction is slowed or halted because excess current leaks out through non-gated K channels.
This reduces the available current for the next node of Ranvier.

74
Q

How many axons does a neuron usually have?

A

One

75
Q

How many dendrites does a neuron usually have?

A

Many

76
Q

Na-K pump pumps __ Na ions out and __ K ions in against their concentration gradients. This results in what?

A

3; 2; Results in a net loss if one charge.

Organ Systems (20 decks)

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