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Physiology > Ch 7 > Flashcards

Ch 7 Flashcards

1
Q

CNS

A

brain + spinal cord

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2
Q

PNS

A

cranial/spinal nerves

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3
Q

neurons

A
  • -> conduct impulses but generally cannot divide 9but CAN repair)
  • respond to chemical/physical stimuli (ex. pain/pressure/heat)
  • conduct electrochemical impulses (ex. an action potential)
  • release chemical regulators (at synapse)
  • enable perception of sensory stimuli, learning, memory, and control of muscles/glands
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4
Q

glial cells (neuroglia)

A

support the neurons, can NOT conduct impulses, but CAN divide

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5
Q

Neuron Structure

A
  1. cell body
  2. dendrites
  3. axon
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6
Q

Cell body

A

contains the nucleus/other organelles

cluster in groups = nuclei/ganglia

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7
Q

nuclei

A

cell body in CNS

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8
Q

ganglia

A

cell body in PNS

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9
Q

dendrites

A

receive impulses and conducts a graded impulses toward the cell body
-shorter than axon

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10
Q

axon

A

conducts action potentials away from the cell body

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11
Q

axon hillock

A

where action potential is generated –> then propagated down the axon

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12
Q

Axonal Transport

A

an active process (needs energy) needed tome organelles and proteins from the cell body –> axon terminals

  • fast component moves vesicles (neurotransmitters)
  • slow components move microfilaments, microtubules, and proteins (a.k.a. cytoskeleton)
  • -> anterograde/retrograde transport
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13
Q

anterograde transport

A

cell body –> dendrites/axon

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14
Q

retrograde transport

A

dendrites/axon –> cell body

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15
Q

Functional classification of neurons

A
  • -> based on direction impulses are conducted
    1. sensory
    2. motor
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16
Q

sensory neurons

A

conduct impulses from sensory receptors to CNS

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17
Q

motor neurons

A

conduct impulses from CNS to target organs

-not just voluntary: somatic (ex. skeletal muscle) vs. autonomic (ex. HR)

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18
Q

Categories of motor neurons

A
  1. Somatic
  2. Autonomic
    - sympathetic
    - parasympathetic
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19
Q

somatic motor neurons

A

responsible for reflexes and VOLUNTARY control of skeletal muscles

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20
Q

autonomic motor neurons

A

innervate INVOLUNTARY targets such as smooth muscles, cardiac muscle, and glands

  1. sympathetic: emergency situations/”fight or flight”
  2. parasympathetic: normal functions/”rest and digest”
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21
Q

Nerves

A

bundles of axons located outside the CNS

  • most composed of sensory + motor neurons (“mixed nerves”)
  • some have sensory only
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22
Q

tract

A

bundle of axons in CNS

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23
Q

Types of neuroglia in PNS

A
  1. Schwann Cells

2. Satellite Cells

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24
Q

Types of neuroglia in CNS

A
  1. Oligodendrocytes
  2. Microglia
  3. Astrocytes
  4. Ependymal Cells
25
Q

Schwann Cells

A

PNS neuroganglia

form myelin sheaths around peripheral axons

26
Q

Satellite Cells

A

PNS neuroganglia
support cell bodies within the ganglia of PNS
-ex. secreting growth factors

27
Q

Oligodendrocytes

A

CNS neuroganglia
form myelin sheaths around the axons of CNS neurons
-analogous to schwann cells

28
Q

Microglia

A

CNS neuroganglia

migrate around CNS tissue and phagocytize foreign and degenerated material

29
Q

Astrocytes

A

CNS neuroganglia
regulate the external environment of the neurons
-regulate tight junctions to regulate material movement in endothelial cells –> create BBB

30
Q

Ependymal Cells

A

CNS neuroganglia

line the ventricles and secrete cerebrospinal fluid

31
Q

BBB

A
  • capillaries in the brain do not have pores between adjacent cells but are joined by tight junctions
  • substances can only be moved by very selective processes of diffusion through endothelial cells, active transport, and bulk transport
  • movement is transcellular, not paracellular
  • astrocytes: support cell bodies/regulate formation of BBB
32
Q

Resting Membrane Potential

A

neurons have a resting potential of -70mV

  • established by large negative molecules inside the cell
  • Na+/K+ pumps
  • permeability of the membrane to positively charged, inorganic ions

–> at rest there is a high concentration of K+ inside the cell and Na+ on the outside

33
Q

Depolarization

A

occurs when positive ions enter the cell (usually Na+)

  • -> membrane potential moves towards 0/more positive
  • EXCITATORY
34
Q

Hyperpolarization

A

occurs when positive ions leave the cell (usually K+)

-INHIBITORY

35
Q

Ion Gating

A

Two types of channels

  1. K+ leakage channels: not gated (always open), increases permeability to K
  2. Voltage-gated K+ channel: open when a particular membrane potential is reached, closed at resting potential

-Na+ voltage-gated channels are closed at rest, the membrane is less permeable to Na+ at rest

36
Q

Voltage Gated K+ Channel

A
  • -> these channels open if the membrane potential depolarizes to -55mV (a.k.a. threshold)
    1. Channels open –> sodium rushes in due to electrochemical gradient
    2. Membrane potential increases toward Na+ equilibrium potential
    3. Channels deactivated at +30mV
    4. Voltage-Gated K+ Channels open and K+ rushes out of cell following electrochemical gradient
    5. This makes the cell depolarize back toward K+ equilibrium potential
37
Q

Action Potentials

A
  1. At threshold membrane potential (-55mV), voltage-gated Na+ channels open and Na+ rushes in
  2. As cell depolarizes, more Na+ channels are open, and the cell becomes more and more permeable to Na+
    - POSITIVE feedback loop
    - causes an overshoot of membrane potential –> reaches +30mV
  3. At +30mV, Na+ channels close and K+ channels open
    - results in repolarization of membrane potential
    - NEGATIVE feedback loop
38
Q

All-or-None

A

-threshold is reached –> action potential occurs

  • size of stimulus will NOT:
    1. affect size of action potential (will always reach +30mV - may recruit more neurons)
    2. affect action potential duration, but will make them happen more frequently
39
Q

Refractory Period

A

action potentials can only increase in freq to a certain point

  • there is a refractory period after action potential when neuron can NOT become excited again (for milliseconds)
  • absolute vs. refractory periods
  • each action potential remains a separate, all-or-none event
40
Q

Absolute Refractory Period

A

occurs during the action potentials

-Na+ channels are inactive (not just closed)

41
Q

Relative Refractory Period

A
  • K+ channels are still open (still in hyper polarization phase)
  • only a very strong stimulus can overcome this
42
Q

Conduction of Nerve Impulses

A
  • action potential occurs at neuron membrane
  • voltage gated Na channels open as a wave down the axon
  • axon potential at one location serves as depolarization stimulus for next region of axon
43
Q

Conduction: Unmyelinated

A
  • chaotic/unorganized
  • axon potentials produced down entire length of axon
  • slow conduction rate b/c so many action potentials are generated
  • amplitude of each action potential is the same (conducted w/o reduction)
44
Q

Conduction: Myelinated

A
  • much more organized
  • myelin = insulation
  • Nodes of Ranvier allow Na and K to cross membrane every 1-2mm
  • -> Na ion channels concentrated at the nodes
  • action potentials “leap” from node to node
  • –> called “saltatory conduction”
45
Q

What is the resting potential in a myelinated neuron?

A

-70mV

46
Q

What is axon potential conduction speed increased by?

A
  1. diameter: reduces resistance to spread of charges via cable properties
  2. Myelination b/c of saltatory conduction
  • -> thin unmyelinated= 1 m/sec
  • -> thick myelinated= 100 m/sec
47
Q

Synapse

A
  • ->the functional connection between a neuron and the cell it’s signaling
  • electrical or chemical
  1. in CNS, second cell = another neuron
  2. in PNS, second cell= muscle/gland (neuromuscular junction)
48
Q

Electrical Synapses

A
  • can occur in mostly in smooth/cardiac muscle, between neurons of brain or glial cells
  • cells joined by gap junctions
  • stimulation causes phosphorylation or dephosporylation of connexion proteins to open or close the channels
49
Q

Chemical Synapses

A
  • most involve the release of a neurotransmitter from axon terminal
  • synaptic cleft: very small, released neurotransmitter can readily diffuse across this space
50
Q

Release of a Neurotransmitter

A

Neurotransmitter is enclosed in synaptic vesicles in the axon terminal

  1. when action potential reaches the end of the axon –> voltage gated Ca channels open
  2. Ca stimulates the fusing of synaptic vesicles to the plasma membrane and exocytosis of neurotransmitter
51
Q

Actions of Neurotransmitter

A

Neurotransmitter diffuses across the synapse, where it binds to a specific receptor protein.

  1. neurotransmitter is referred to as the ligand
  2. results in opening of chemically regulated ion channels (a.k.a. ligand-gated ion channels)
52
Q

Acetylcholine (ACh)

A

Neurotransmitter: directly opens ion channels when it binds to a receptor

  • Excitatory in some areas of CNS, in some autonomic motor neurons, and in all somatic motor neurons
  • Inhibitory in some autonomic neurons
53
Q

Nicotinic ACh Receptors

A
  • can be stimulated by nicotine

- found on motor end plate of skeletal muscle cells, in autonomic ganglia, and in some parts of the CNS

54
Q

Muscarinic ACh Receptors

A
  • can be stimulated by muscarine (from poisonous mushrooms)

- found in CNS and plasma membrane of smooth/cardiac muscles and glands innervated by autonomic motor neurons

55
Q

Agonists

A

drugs that can stimulate a receptor

56
Q

Antagonists

A

drugs that inhibit a receptor (ex. beta-blockers)

57
Q

Acetylcholinesterase (AChE)

A
  • enxyme that inactivates AChE activity shortly after it binds to the receptor
  • hydrolyzes ACh into acetate and choline, which are taken back into the presynaptic cell of reuse (recycles to rebuild ACh)
58
Q

Monoamines

A

Regulatory molecules derived from AAs

  1. Catecholamines: derived from tyrosine (ex. dopamine, norepinephrine, and epinephrine)
  2. Serotonin: derived from L-tryptophan
  3. Histamine: derived from histidine
59
Q

Monoamine Action/Inactivation

A
  • made from presynaptic axon, released via exocytosis, diffuse across synapse, and bind to specific receptors
  • quickly taken back into the presynaptic cell (reuptake) and degraded by monoamine oxidase (MAO)

Physiology (29 decks)

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