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Physiology > Exam 2 Review- Lecture 6 > Flashcards

Exam 2 Review- Lecture 6 Flashcards

1
Q

What are the 2 functional divisions of PNS?

A

Afferent and efferent

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2
Q

What is an afferent (sensory) division?

A

Receives info from sensory receptors in peripheral tissues and organs and transmits it to CNS

Somatic sensory system detects stimuli we consciously perceive (from skeletal muscles, bones and joints)

Visceral sensory systems detects stimuli we do not perceive (from viscera (organs) and blood vessels)

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3
Q

What is an efferent (motor) division?

A

Initiates motor output and transmits it from CNS to effectors

Effectors= target organs that carry out motor commands

Somatic nervous system- voluntary and involuntary control of skeletal muscles

Autonomic nervous system (visceral motor)

  • involuntary control of heart, smooth muscles and glands
  • has sympathetic and parasympathetic divisions
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4
Q

What is the structure of an axon?

A

Single, long cytoplasmic process extending from cell body

Propagates electric signals (action potentials)

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5
Q

What is axoplasm?

A

Cytoplasm of axon

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6
Q

What is an axolemma?

A

Plasma membrane of axon

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7
Q

What is the initial segment of an axon?

A

Base of axon

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8
Q

What is an axon hillock?

A

Thick, triangular region on cell body that attaches to initial segment of axon

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9
Q

What are collaterals?

A

Branches of the axon

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10
Q

What is a telodendria?

A

Fine extensions of distal axon

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11
Q

What are axon terminals (synaptic terminals)?

A

Tips of telodendria

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12
Q

What are anaxonic neurons?

A

Have dendrites, no axons

Found in brain and special sense organs

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13
Q

What are unipolar neurons?

A

1 process (dendrite continuous with axon) and extends from cell body, which is off to the side

Splits into 2 processes

  • peripheral process splits into several receptive dendrites
  • central process leads to axon terminals in CNS

Most sensory neurons of PNS

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14
Q

What are bipolar neurons?

A

1 dendrite and 1 axon

Found on special sense organs (sight, smell and hearing)

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15
Q

What are multipolar neurons?

A

Many dendrites and 1 long axon

Most common in CNS

All motor neurons that control skeletal muscles

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16
Q

What are sensory (afferent) neurons?

A

Most are unipolar

Cell bodies grouped in sensory ganglia of PNS

Carry action potentials via afferent fibers (axons) from sensory receptors to CNS

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17
Q

What do somatic sensory neurons monitor?

A

External environment

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18
Q

What do visceral sensory neurons monitor?

A

Internal environment

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19
Q

What are the 3 types of sensory receptors?

A

1) Interoceptors
2) exteroceptors
3) proprioceptors

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20
Q

What are interoceptors?

A

Monitor internal systems (ex: digestive/ urinary)

Internal senses (stretch, deep pressure, pain)

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21
Q

What are exteroceptors?

A

Monitor external environment (ex: temp)

Complex senses (ex: sight, smell, hearing)

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22
Q

What are proprioceptors?

A

Monitor position and movement of skeletal muscles and joints

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23
Q

What are the 4 kinds of cells in your CNS?

A

1) Astrocytes (star shaped)
2) ependymal cells
3) microglia
4) oligodendrocytes

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24
Q

What are astrocytes?

A

Have large cell bodies with many processes

Stimulate formation of tight junctions in cells that make up walls of capillaries in CNS to form blood brain barrier (BBB)

Main glue in CNS

control exchange of materials b/n blood and neurons

Repair damaged nervous tissue

Stimulate neuronal growth and development

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25
Q

What are ependymal cells?

A

Line certain canal of spinal cord and ventricles (fluid filled cavities) of brain

Make up the choroid plexus- produce and monitor cerebrospinal fluid (CSF)

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26
Q

What are microglia cells?

A

Macrophage like cells

Immune cells of CNS

Engulf and digest cellular debris, wasted and pathogens

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27
Q

What are oligodendrocytes?

A

Small cell bodies with few processes

Processes wrap around axons of neurons forming myelin sheath

  • myelin (fat) insulated myelinated axons
  • increases speed of action potentials among the axon
  • makes nerves appear white
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28
Q

What are internodes in oligodendrocytes of the CNS?

A

Myelinated segments of axon

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29
Q

What are nodes (nodes of Ranvier) in oligodendrocytes of the CNS?

A

Unmyelinated segments b/n internodes

Where axon may branch

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30
Q

What is white matter in oligodendrocytes of the CNS?

A

Regions of CNS with many myelinated axons

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31
Q

What is gray matter in oligodendrocytes of the CNS?

A

Contains unmyelinated axons, neurons cell bodies and dendrites

32
Q

What 2 kinds of cells are in the PNS?

A

1) satellite cells
2) Schwann cells

Insulate neuronal cell bodies and most axons

33
Q

What are satellite cells?

A

Arranged around ganglia

Regulate nutrient and waste exchange for cell bodies in ganglia

34
Q

What are Schwann cells or neurolemmocytes?

A

Form myelin sheath or indented folds of plasma membrane around axons

Neurolemma

A myelination Schwann cell sheaths only 1 axon- many Schwann cells sheath entire axon

35
Q

What is a neurolemma?

A

Outer surface of Schwann cell

36
Q

After traumatic injuries, PNS axons regeneration is possible if:

A
  • neuron cell body is intact

- enough neurilemma remains

37
Q

After traumatic injuries, PNS axons regeneration success is more likely if:

A
  • amount of damage is less extensive

- distance b/n site of damage and structure innervates is shorter

38
Q

What is wallerian degeneration?

A

Axon distal to injury degenerates

39
Q

What do Schwann cells do after traumatic injury?

A

Form path for new growth

Wrap around new axon

40
Q

What is nerve regeneration in CNS?

A

Limited by astrocytes

Produce scar tissue and obstructs regrowth

Releases chemicals (growth-inhibiting) that block regrowth

41
Q

What is the 1st step of axon regeneration in PNS?

A

Axon severed by trauma

42
Q

What is the 2nd step of axon regeneration in PNS?

A

A) proximal to cut: axon seals off and swells

B) distal to cut: axon and sheath degenerate (wallerian degeneration) but neurilemma survives

43
Q

What is the 3rd step of axon regeneration in PNS?

A

Neurilemma and endoneurium form a regeneration tube

Schwann cells for cord, grow into cut and unite stumps

Macrophages engulf degenerating axon and myelin

44
Q

What is the 4th step of axon regeneration in PNS?

A

Axon regenerates guided by nerve growth factors released by Schwann cells in cord

Axon is remyelinated

45
Q

What is the 5th and final step of axon regeneration in PNS?

A

Axon reinnervates original effector or sensory receptor

46
Q

What is equilibrium potential in RMP?

A

Membrane potential at which there is no net movement of a particular ion across cell membrane

K+ = -90mV
Na+ = +66mV

Plasma membrane is highly permeable to K+

Resting membranes permeability to Na+ is very low

47
Q

What does it mean when a Plasma membrane is highly permeable to K+?

A

K+ diffusion is the most important factor setting RMP
- equilibrium potential for K+ is close to RMP (-70mV)

K+ leak channels (always open for continuous diffusion)
- K+ diffuses out of cell

K+ diffusion out is limited by the electrical gradient (- RMP pulls K+ into cell)

48
Q

What does it mean when a Resting membranes permeability to Na+ is very low?

A

Na+ has a small effect on resting potential

Na+ diffuses into cell

49
Q

In RMP, what is an active process across membrane and explain?

A

Sodium- potassium (Na+ - K+) exchange pump

  • Powered by ATP
  • Ejects 3 Na+ for every 2 K+ brought in
  • balances passive forces of diffusion
  • Stabilizes RPM (-70mV) when ratio of Na+ entry to K+ loss through massive channels is 3:2
50
Q

Why does RMP exist?

A

Cytosol differs from ECF in chemical and ionic composition

Plasma membrane is selectively permeable

51
Q

True or false:

Membrane potential changes in response to temporary changes in membrane permeability

Results from opening or closing specific membrane channels in response to stimuli

A

TRUE

52
Q

What are graded potentials?

A

Local potentials

Changes in membrane potential cannot spread far from site of stimulation (short- distance)

Produced by any stimulus that opens chemically gated ion channels- generated at the dendrites or cell body of neuron

53
Q

What is an example of graded potentials?

A

A resting membrane is exposed to a chemical (neurotransmitter)

  • chemically gated Na+ channels open
  • Na+ enter cell
  • membrane potential rises (depolarization)
  • Na+ moves parallel to plasma membrane- produces local current which depolarizers nearby regions of plasma membrane
54
Q

What is depolarization?

A

Potential moving from RMP to less negative values (closer to 0)

55
Q

What is repolarization?

A

When stimulus is removed, membrane potential returns to normal (RMP)

56
Q

What is hyperpolarization?

A

Results from opening K+ channels

K+ moves out of cell (efflux)- opposite effect of opening Na+ channels

Increases negativity of RMP- potential moving away from RMP in a more negative direction

57
Q

What is the 1st step of the generation of action potentials?

A

Graded depolarization to threshold

58
Q

What is the 2nd step of the generation of action potentials?

A

Activation of voltage gated Na+ channels

  • Na+ rushed into cytosol (Na+ influx)
  • inner membrane changes from negative to positive
  • results rapid depolarization
59
Q

What is the 3rd step of the generation of action potentials?

A

Inactivation of Na+ channels and activation of K+ channels

At +30mV voltage gated Na+ channels close becoming innactivated (unable to open)

Voltage gated K+ channels slowly open

K+ moves out of cytosol (K+ efflux)—> negative membrane potential

Repolarization begins

60
Q

What is the 4th step of the generation of action potentials?

A

Return to RMP

Voltage gated Na+ channels are now in resting state

Voltage gated K+ channels begin to close slowly

  • as membrane reaches normal RPM, K+ continues to leave cell
  • membrane is briefly hyperpolarized to -90mV

After all voltage gated K+ channels finish closing

  • RMP is restored
  • AP is over
61
Q

What are Type A fibers?

A

Myelinated

Large diameter

Transmit info to and from CNS rapidly

Ex: sensory info such as position and balance (somatic sensory neurons) and all motor impulses to skeletal muscles (somatic motor neurons)

62
Q

What are type B fibers?

A

Myelinated

Medium diameter

Transmit info at intermediate speeds

Ex: some visceral neurons and somatic sensory neurons from skin

63
Q

What are type C fibers?

A

Unmyelinated

Small diameter

Transmits info slowly

Ex: most sensory info

64
Q

What are synapses?

A

Specialized site where a neuron communicates with another cell (neuron or effector)

65
Q

What are presynaptic neurons?

A

Sends the message

66
Q

What are postsynaptic neurons?

A

Receives message

67
Q

What are electrical synapses?

A

Direct physical contact b/n cells

68
Q

What are chemical synapses?

A

Signal transmitted across a gap by neurotransmitters

69
Q

What are cholingeric synapses?

A

Type of chemical synapse

Releases acetylcholine (ACh)

  • All NMJs involving skeletal muscle fibers
  • Many synapses in CNS
  • All neuron to neuron synapses in PNS
  • All neuromuscular and neuroglandular junctions in parasympathetic divisions of ANS
70
Q

What are the 4 events at a cholinergic synapses?

A

1) AP arrives at axon terminal and depolarizes membrane
2) Extracellular Ca2+ enter axon terminal and trigger exocytosis of ACh
3) ACh binds to receptors on Postsynaptic membrane and depolarize it
4) ACh is removed from synaptic cleft by acetylcholinesterase (AChE)- AChE breaks ACh into acetate and choline

71
Q

What is a synaptic delay?

A

Occurs b/n arrival of AP at axon terminal and effect on postsynaptic membrane

Mostly due to time required for Ca2+ influx and neurotransmitter release

72
Q

Postsynaptic potential is the result of all OR none of the synaptic activity affecting it?

Postsynaptic neuron can bind to many OR one neurotransmitter simultaneously?

A

ALL

MANY

73
Q

To trigger an AP is 1 EPSP enough or do you need multiple EPSPs?

A

Multiple to trigger summation

74
Q

What is summation?

A

Voltage changes from dendrites and soma are added

75
Q

What is temporal summation?

A

Rapid, repeated stimuli occurring at different times at a single synapse (same presynaptic neuron)

Second stimulus arrives before first stimulus disappears

76
Q

What is spatial summation?

A

Simultaneous stimuli arrive at multiple synapses (different locations- 2 presynaptic neurons)

Cumulative effect of the multiple synapses

Physiology (7 decks)

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