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Biology 152 > Nervous System > Flashcards

Nervous System Flashcards

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1
Q

What are the three functions of the nervous system?

A
  • detect changes in internal, external environments
  • integrates info, make unconscious and conscious decisions
  • stimulates muscles and glands to respond
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2
Q

What are the two divisions within the nervous system?

A
  • central nervous system (CNS) - brain & spinal cord, analyze & coordinates
  • peripheral nervous system (PNS) - sensory/afferent division & motor/efferent division
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3
Q

What is the job of the sensory division?

A

-receives input from special senses (eyes, ears, nose, mouth), from internal organs (visceral sensory neurons), and from joints and skeletal muscle (somatic sensory neurons)

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4
Q

What is the job of the motor division?

A
  • sends commands

- 2 parts: autonomic nervous system, somatic motor neurons

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5
Q

What is the autonomic nervous system?

A
  • mostly involuntary
  • sympathetic (fight or flight) to cardiac muscle, smooth muscle, glands
  • parasympathetic (rest or digest) to skeletal muscle
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6
Q

What is the role of somatic motor neurons?

A

-mostly voluntary

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7
Q

What are the special characteristics of neurons?

A
  • long-lived - entire lifetime
  • amniotic - can’t divide
  • high metabolic rate: needs lots of “food”: oxygen, and glucose
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8
Q

What are neurons made of?

A

-dendrites, cell body, dendritic spines, axons

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9
Q

What is the S&F of dendrites?

A

-dendrites: highly branched processes (stick out) that receive information

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10
Q

What is the S&F of dendritic spines?

A

-increase surface area to receive information

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11
Q

What is the S&F of the cell body?

A

-cell body: soma: large to produce neurotransmitters, clusters of cells in CNS are called nuclei, clusters of cells in PNS are called ganglia

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12
Q

What is the S&F of axons?

A
  • length varies
  • may be myelinated to increase the speed of impulse transmission
  • may have collateral branches = side branches
  • synaptic knobs at the end hold vesicles with NT
  • axons wrapped in connective tissue
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13
Q

What are the types of connective tissue that cover the axons?

A
  • endoneurium: covers single axon; has capillaries
  • perineurium: covers bundles of axons (nerve fascicles) has arteries and veins
  • epineurium: covers bundles of nerve fascicles
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14
Q

What are bundles of axons called in the CNS and PNS?

A

CNS: tract
PNS: nerve

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15
Q

What are the types of neurons?

A
  • multipolar
  • bipolar
  • unipolar
  • anaxonic
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16
Q

What are the characteristics of a multipolar neuron?

A
  • many dendrites, 1 long axon

- mostly common in CNS, all motor neurons

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17
Q

What are the characteristics of a bipolar neuron?

A
  • 1 dendrite, 1 axon

- rare, special sense organs

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18
Q

What are the characteristics of a unipolar neuron?

A
  • dendrites continuous with the axon
  • sensory neurons in the PNS
  • cell body in dorsal root ganglion
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19
Q

What are the characteristics of a anaxonic axon?

A

-can’t distinguish dendrites and axons

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20
Q

What is the classification by function for sensory neurons?

A
  • mostly unipolar
  • carry info from sensory organs/receptors to CNS
  • eg. exteroceptors: info from outside: touch, vision, sight
  • eg. interoceptors: monitor internal organs
  • eg. proprioceptors: monster muscle and joint position
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21
Q

What is the classification by function for interneurons?

A
  • mostly multipolar and found in CNS but some anaxonic
  • between sensory and motor neurons
  • integrate info
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22
Q

What is the classification by function for motor neurons?

A
  • ALL multipolar but the cell bodies are in the CNS

- carry info to muscles and glands

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23
Q

What is a characteristic of neuroglia?

A

-smaller than the neurons but also outnumber them 10:1

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24
Q

What are the 4 types of neuroglia in the CNS?

A

-astrocytes, microglia, oligodendrocytes, ependymal cells

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25
Q

What is the S&F of astrocytes?

A
  • most common, star-shaped
  • surround to maintain blood-brain barrier and control transport of the material into the interstitial fluid
  • create supportive network for neuron
  • recycle NT
  • guides neuronal migration in the embryo (growth)
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26
Q

What is the S&F of microglia?

A
  • small cells with “thorny” processes

- defend and remove debris (no WBC in CNS)

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27
Q

What is the S&F of oligodendrocytes?

A
  • processes wrap around portions of multiple CNS axons

- to myelinated/insulate axons to increase the speed of action potential

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28
Q

What is the S&F of ependymal cells?

A
  • look like epithelial
  • ciliated cells joined to tight junctions
  • lines ventricles of the brain, central canal of spinal cord
  • produce, monitor, circulate, cerebral spinal fluid (CSF)
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29
Q

What are the two types of neuroglia in the PNS?

A
  • schwann cells

- satellite cells

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30
Q

What is the S&F of Schwann cells?

A
  • whole cells wrapped around part of one axon = myeline axon –> AP travels 150x faster
  • many Schwann cells needed to myeline 1 axon
  • adjacent Schwann cells don’t touch (gap= node of Ranvier
  • AP is propagated at nodes of Ranvier
  • demyelination results in less sensation and control = MS
  • Schwann cells also guide axon growth during neuron repair
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31
Q

What is the S&F of satellite cells?

A
  • surround cell bodies in ganglia

- help regulate the environment around the neurons

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32
Q

What is the resting potential?

A

-difference in voltage (+,-) across the membrane when the cell is at rest

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33
Q

What generates the resting membrane potential?

A
  • most Na+ in body lies outside cells, most K+ is inside cells - a bit motor negative on the inside of the membrane (-70 mV)
  • cells have proteins (large molecules stay inside the cells) with negatively charged amino acids
  • cells have leaky K+ channels
34
Q

Why does K+ leak out of cell?

A

-leaky K+ channels
-K+ diffuses down the electrochemical gradient out of cells
-some K+ is pumped back in via Na+/K+ pump
= overall negative charge left inside the cell (70mV)

35
Q

Where is the location of the graded potential?

A

-dendrite –> soma –> axon hillock

36
Q

Where is the location that an action potential happens?

A

-axon hillock –> axon –> synaptic knob

37
Q

What is the location of neurotransmitters?

A

-synaptic knobs –> synaptic cleft –> dendrites (of another neuron)

38
Q

What are the three types of channels?

A

1) GP- ligand gated (molecule biding)/mechanically gated (Na/Cl channels)
2) AP- voltage gated Na+/K+ channels
3) NT- voltage gated Ca2+ channels

39
Q

What are the stimulus/triggers of the channels?

A

1) GP- forced movement (ligand or mechanically gated
2) AP- ion flow, depolarization (increase and charge)
3) NT- depolarization

40
Q

What are the distances that can be travelled?

A

1) GP-short distance travelled within soma through cytosol
2) AP-long distance travelled (cm) regenerated along the axon
3) NT-short distance across the synaptic cleft

41
Q

What are the events at the dendrites?

A
  • stimulus opens ligand-gated or mechanically-gated ion channels
  • ion flow generates graded potentials
42
Q

What stimuli open ligand-gated channels?

A
  • NT
  • food (smell molecules)
  • chemicals in body (eg. glucose, CO2)
  • chemicals released by injured cells
  • light (triggers reaction that produce molecules)
43
Q

What stimuli open mechanically-gated channels?

A
  • touch, pressure, vibration
  • stretch
  • sound
44
Q

When do positive ion flows generate graded potentials?

A
  • if positive ions enter dendrites- increases positive charge in cells = cell depolarizing - makes cell more likely to fire
  • if positive ions leaves dendrites -makes cell more negative = hyperpolarization and less likely to fire)
  • negative ions enter dendrites
45
Q

What factors change the strength of the graded potential?

A
  • week stimulus: few channels open, few ions flow

- strong stimulus: many channels open, many ions flow

46
Q

Why can a GP be excitatory?

A

-Na+ or K+ influx = depolarization = excitatory postsynaptic potential (EPSP)

47
Q

Why can a GP be inhibitory?

A

-K+ efflux/Cl- influx = hyperpolarization = inhibitory postsynaptic potential (IPSP)

48
Q

What determines if a threshold is reached?

A

-summation of all the EPSPs and IPSPs

49
Q

What happens if there is a weak stimulus?

A

-threshold is not reached = no signal passed on

50
Q

What happened in a strong stimulus?

A

-spacial summation or temporal summation

51
Q

What is spacial summation?

A
  • ions for many synapses add up because many terminals release Its simultaneously
  • few AP
52
Q

What is temporal summation?

A
  • high frequency of firing

- ions from one synapse add up over time because the new NT released before initial amounts degraded

53
Q

What is the axon hillock?

A
  • voltage-gated channels present at axon hillock
  • if axon hillock reaches threshold potential, voltage-gated channels open –> AP is generated
  • if axon hillock does not reach threshold potential, voltage-gated channels stay closed –> NO AP
54
Q

What does the amount of depolarization have to be in order for an AP to take place?

A
  • -55mV

- if its -30mV perhaps multiple will fire

55
Q

What are the characteristics of an action potential?

A
  • brief reversal in membrane potential =-70mV
  • always the same strength
  • only axons and muscle cells have excitable membrane - they have voltage-gated channels therefore can generate an AP
56
Q

What is the first step of an action potential?

A
  • resting membrane potential = -70mV

- voltage gated Na+, K+ channels @ axon hillock and axon are closed, capable of opening

57
Q

What is the second stop in an AP?

A
  • stimulus triggers graded potential in soma

- depolarization spreads through soma to voltage-gated Na+ channels at axon hillock

58
Q

What is the third step of an AP?

A
  • when depolarization reaches -55mV, threshold potential reached
  • voltage Na+ channels at axon hillock open
  • outer gates open fast, inner gate close slowly
59
Q

What is the fourth step of an AP?

A
  • fast depolarization to +30mV
  • Na+ rushes down electrochemical gradient
  • depolarization opens next set of voltage-gated Na+ channels, AP propagated along axon
60
Q

What is the turning point in an AP?

A
  • step 5
  • slow inner gates closed, Na+ channels closed
  • no more Na+ enters
  • voltage K+ channels open
61
Q

What is repolarization?

A
  • step 6 in AP

- K+ rushes down the electrochemical gradient

62
Q

What is hyperpolarization?

A

-step 7 of AP
-K+ gates slow to close
-excess K+ leaves the cell
Na+/K+ will eventually restore ion distribution

63
Q

How is the AP ‘“all or none”?

A
  • weak stimulus: subthreshold no AP
  • strong stimulus: threshold reached AP
  • stronger stimulus: threshold reached more often, increased AP but all AP are the same strength
64
Q

What is the refractory period in an AP?

A

-ensures unidirectional propagation of APq

65
Q

What is the absolute refractory period?

A
  • Na+ gates open or inactivated
  • region can’t respond to another stimulus
  • only Na+ channels further along axon can open
  • ensures AP
66
Q

What is the relative refractory period?

A
  • gates have been reset, are ready to open but cell is hyperpolarized
  • threshold stimulus won’t trigger another AP
  • stronger stimulus will reopen Na+ channels, trigger AP
67
Q

What is AP propagation?

A

1) AP along unmyelinated axons travel by continuous propagation
- voltage gated Na+ channels open along an axon
2) AP along myelinated axons travels by salutary conducting 150x faster
- myeline insulate fibres
- voltage-gated Na+ channels at nodes of Ranvier
- AP generated only at nodes

68
Q

What is the synaptic knob?

A
  • synapse is junction between 2 neurons or between neuron and effector
  • converts electrical impulse to chemical signal and back again
69
Q

What are the events at a synapse?

A

1) voltage-gated Ca2+ channels open
- Ca2+ floods in
2) Ca+ triggers synaptic vesicles to fuse with axonal membrane
- NT released by exocytosis
- Ca2+ removed by mitochondria
3) NT binds to receptors, open ion channels - open Na+ channels
- depolarization = EPSP
- opens K+ or Cl- channels - hyperpolarization =IPSP
4) NT removed from postsynaptic receptor by:
- degration (break down) of enzymes or removed by a transporter
- uptake by neuroglia cell =astrocytes or neuron that released it (presynaptic neuron) for storage (sometimes keeps parts to make something new)
- diffusion

70
Q

What are neurotransmitters (NT)?

A
  • may bind to different types of receptors on different postsynaptic cells
  • receptor type determines effect of NT on cell
  • NT may be excitatory, inhibitory or both depending on type/location on receptor
71
Q

What is Achetylcholine?

A
  • NT
  • excites skeletal muscle, inhibits cardiac muscle
    eg. snake venom & curare inhibit binding of Ach to receptor –> flaccid paralysis (NT can’t bind to receptor and channels don’t open so no AP)
    eg. nerve gas prevents Ach removal from synapse –> muscle spasms leading to death (diaphragm is a muscle) (NT builds up channels stay open producing too many AP)
72
Q

What are Monoamines?

A

NT

  • norepinephrine
  • dopamine
73
Q

What is norepinephrine?

A
  • excitatory/inhibitory depending on location
  • feeling good
  • tricyclin antidepressants block NE removal from synapse –> enhance good feelings
74
Q

What is dopamine?

A
  • excitatory/inhibitory
  • feeling good skeletal muscle control
  • coccaine binds competitively to dopamine
  • reuptake transported
  • given to Parkinson’s patients to control complex movement
  • fewer NT, channels stay closed - no AP
  • Add NT substitute –> channel opens
75
Q

What is serotonin?

A
  • NT
  • inhibitory
  • regulates mood, sleep, appetite, nausea
  • feeling good
  • prozac blocks seretonin uptake –> enhances positive feelings to reduce depression
  • LSD blocks seretonin activity –> inhibitory effect reduce excess AP –> hallucinations
76
Q

What affect does prozac have on AP?

A
  • NT builds up and opens more channels
  • cells stays hyperpolarized
  • decreased firing fear and anxiety centres
77
Q

What affect does LSD have on AP?

A
  • seretonin can’t bind therefore channel stays closed
  • K+ can’t leave but continues to enter through Na+/K+ pump
  • (+) charge builds up and cell depolarizes
  • excessive EPSP excess AP
78
Q

What are amino acids NTs?

A

eg. gabba
- inhibitory, opens Cl- channels
- principle inhibitory NT in brain
- alcohol and value –> augment effects

79
Q

What are neuropeptides?

A

eg. endorphins
- inhibitory
- widely distributed in brain, inhibits pain
- morphine, heroine are structurally similar (bind to receptors and mimic effect)

80
Q

What are neuromodulators?

A

eg. nitric oxide
- excitatory
- brain, spinal cord induces muscle relaxation
- nitroglycerin released NO –> relaxes smooth muscle of the blood vessels and increases blood flow in the heat, reduces angina

Biology 152 (12 decks)

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