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KP222 > Quiz #2 > Flashcards

Quiz #2 Flashcards

1
Q

What are the 2 main divisions of the nervous system?

A

central nervous system

  • integrating centre
  • spinal cord and brain

peripheral nervous system

  • all neural tissue outside CNS
  • afferent and efferent neurons
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2
Q

What are neurons?

A

excitable cells that send and receive electrical signals rapidly over long distances

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3
Q

What is the role of the brain and spinal cord in the CNS?

A

integrating centre for homeostasis, movement, etc.

controls the entire nervous system

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4
Q

What is the structure of a neuron?

A

cell body
- contains nucleus and other organelles

dendrites

  • thin, branched processes that receive incoming signals
  • allow communication with multiple other neurons
  • increase surface area

dendritic spines

  • very fine, branched processes
  • further increase surface area

axon

  • carries electrical signal from cell body to target
  • has axon hillock (where axons and action potentials initiate), axon terminal (where NT vesicles are released), and collaterals (spare branching off axon)
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5
Q

What is a synapse?

A

site of communication between the axon of one neuron and the dendrite of another OR between the axon of one neuron and an effector organ

pre-synaptic neuron to post-synaptic neuron

if the action potential is strong enough it will propagate across multiple neurons to get to its intended destination

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6
Q

What is anterograde transport?

A

transport from cell body to axon terminal

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7
Q

What is retrograde transport?

A

transport from axon terminal to cell body

  • slow: through cytosol
  • fast: using network of microtubules and neurofilaments, kinesin proteins carry NT vesicles
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8
Q

Describe the stages of fast axonal transport.

A

FAT walks vesicles and mitochondria along microtubule network

vesicles released into synapse by exocytosis

synaptic vesicle recycling (some come back into pre-synaptic neuron via reuptake)

retrograde FAT

old membrane components digested by lysosomes

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9
Q

What are the types of neurons?

A

multipolar
bipolar
pseudounipolar
anaaxonic

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10
Q

What are multipolar neurons?

A

most common
many processes, highly branched
lack long extensions

ex. motor neuron

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11
Q

What are bipolar neurons?

A

2 approximately equal fibers off the cell body
single axon, single dendrite

common with special senses

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12
Q

What are pseudounipolar neurons?

A

single axon
dendrites fused to axon, cell body attached to axon

most afferent/sensory neurons

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13
Q

What are anaxonic neurons?

A

no axon
numerous dendrites

interneurons in CNS

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14
Q

What is the difference between afferent, efferent, and interneurons?

A

afferent - carry info from sensory receptors to CNS

efferent - carry response from CNS to effector organs

interneurons
- interconnecting neurons with complex branching

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15
Q

What are the types of sensory/afferent receptors?

A

interoceptors
- monitor internal systems and senses

exteroceptors
- monitor external and distance senses

proprioceptors
- monitor position and movement

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16
Q

What are the 2 divisions of the efferent system?

A

somatic
- skeletal muscle

autonomic
- smooth muscle, cardiac muscle

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17
Q

What are neuroglial cells?

A

“glue”
make up half the volume of the nervous system
essential to survival and function

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18
Q

What are the types of neuroglia?

A 
ependymal
microglia
astrocytes
oligodendrocytes
Schwann cells/satellite cells
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19
Q

Describe the main role of ependymal cells.

A

line central canal of spinal cord and brain

- secrete and circulate CSF

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20
Q

Describe the main role of microglia.

A

clean up cellular debris, waste, and pathogens

smallest and least numerous

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21
Q

Describe the main role of astrocytes.

A

make up 1/2 the cells of the brain
communicate via gap junctions

maintain blood-brain barrier
guide neuron development

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22
Q

Describe the main roles of oligodendrocytes.

A

wrap around axons to form myelin sheaths

  • white matter
  • only in CNS
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23
Q

Describe the neuroglia of the PNS.

A

schwann cells

  • form myelin sheaths around axons
  • takes many cells to sheath entire axon
  • leave tiny gaps called nodes of ranvier

satellite cells

  • non-myelinated schwann cells
  • form supportive capsules around nerve cells
  • regulate environment around neuron
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24
Q

What is myelination?

A

increases speed of action potentials by insulating axons

makes nerves appear white (white matter)

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25
Q

What are nodes of Ranvier?

A

gaps between internodes where axons may branch

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26
Q

What are internodes?

A

myelinated segments of axon

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27
Q

What is an action potential?

A

large, rapid change in membrane potential produced by depolarization of an excitable cell to threshold (-55 mV)

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28
Q

What is equilibrium potential?

A

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

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29
Q

What are the 3 requirements for membrane potential?

A

ICF and ECF differ markedly in ionic concentration

selective permeability

cell transport do not ensure equal distribution across membrane

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30
Q

What is the resting membrane potential?

A

-70 mV

inside relative to outside

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31
Q

How are ions distributed when the cell is at rest?

A

outside - more Na+ and Cl-

inside - more K+ and organic anions

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32
Q

How do voltage gated channels work?

A

respond to change in transmembrane potential

activation gate (voltage dependent) opens, period of latency before inactivation gate (voltage and time dependent) closes, during latency molecules flow inward

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33
Q

What is a graded potential?

A

changes in transmembrane potential
signal travels short distance, losing strength as it goes

IPSPs or EPSPs

if enough strength at integrating region, forms action potential

may go above threshold (-55 mV) locally, but if below this at the axon hillock then no action potential will occur

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34
Q

What is repolarization?

A

when stimulus is removed and transmembrane potential returns to normal

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35
Q

What is hyperpolarization?

A

increased negativity of resting potential as a result of opening K+ cells

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36
Q

What is the all-or-none principle?

A

if a stimulus exceeds the threshold amount, the AP will be the same no matter how large the stimulus from the graded potential

strength of graded potential has no influence on amplitude, action potential is either triggered or it is not

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37
Q

What happens to the cell at +30 mV?

A

Na+ inactivation channels close, K+ channels open

repolarization begins

38
Q

What is the absolute refractory period?

A

membrane can’t produce another AP because Na+ channels are inactivated

AP can’t overlap

ensures 1 way travel of AP

39
Q

What is relative refractory period?

A

follows the absolute refractory period

when K+ channels are still open so it is possible, but more difficult for an AP to occur

40
Q

What are the 2 methods of action potential propagation?

A

continuous propagation - unmyelinated axons

saltatory propagation - myelinated axons

41
Q

Describe continuous propagation.

A

after AP fires, Na+ influx depolarizes adjacent region and generates new AP, repeats all along the axon

amplitude always the same

conduction is slow

42
Q

What things determine the speed of an action potential?

A

diameter
- larger = faster

myelination
- myelinated = faster

43
Q

Describe saltatory conduction.

A

APs leap from node of Ranvier to node of Ranvier where there are high concentrations of Na+ channels, and they are regenerated

myelin sheath prevents Na+ and K+ from leaving the cell

conduction is faster

44
Q

What are electrical synapses?

A

pass electrical signals through direct physical contact (gap junctions)

can be excitatory or inhibitory

45
Q

What are chemical synapses?

A

used by most neurons

cells not in direct contact, signal is transmitted across a gap by NT binding to receptor on postsynaptic cell that affects AP

46
Q

Describe the events at a chemical synapse.

A

AP arrives at end of axon terminal

Ca2+ channels open allowing it to enter down concentration gradient

influx of Ca2+ causes synaptic vesicles to move to the presynaptic membrane and fuse

once fused, contents released (exocytosis) to diffuse across cleft and bind to postsynaptic neuron receptors

generates a response

NT either diffuse out of the cell, are degraded by enzymes, or actively transported back into presynaptic cell

47
Q

What are ionotropic receptors?

A

NT binds to a receptor on a channel that causes conformational change

48
Q

What are metabotropic receptors?

A

NT binds to a receptor which activates a G-protein that activates a response

can either:

  • open/close ion channel (direct coupling)
  • activate/inhibit enzyme that produces a second messenger to carry out cellular tasks (second messenger system - slow but more broad effects)
49
Q

What are cholinergic synapses?

A

any synapse that releases acetylcholine (ACh)

can be excitatory or inhibitory depending on receptor subtype (nicotinic or muscarinic)

50
Q

What is acetylcholinesterase?

A

AChE

enzyme that breaks down acetylcholine into acetate and choline

rapidly breaks down ACh where choline can be transported back into presynaptic axon terminal (co-transport with Na+) and recycled to make more ACh

51
Q

What are nicotinic receptors?

A

ligand-operated/ionotropic

generate EPSP bringing closer to AP threshold (excitatory post-synaptic potential)

52
Q

What are muscarinic receptors?

A

G-protein operated/metabotropic

generate IPSP bringing further from AP threshold (inhibitory post-synaptic potential)

53
Q

What are biogenic amines?

A

derived from amino acids

ex. serotonin, dopamine, histamine

54
Q

What are catecholamines?

A

derived from tyrosine

dopamine, norepinephrine, epinephrine

55
Q

What amino acid neurotransmitters act a excitatory and inhibitory synapses?

A

excitatory: aspartate, glutamate
inhibitory: glycine, GABA

56
Q

What is summation?

A

additive effects of graded potentials (IPSPs and EPSPs)

temporal summation
- repeated stimulation of 1 synapse

spatial
- stimulate of several synapses at the same time

57
Q

What is frequency coding?

A

the degree of depolarization at the axon hillock is signalled by the frequency of APs

more APs = greater NT released = greater IPSP or EPSP at next neuron

58
Q

What are the 3 meninges?

A 
dura mater
- tough outside
pia mater
- tender inside
arachnoid mater
- spidery inside
59
Q

What is cerebrospinal fluid?

A

clear, watery fluid bathing the CNS
produced by ependymal cells of choroid plexus
recycled 3 times a day
circulates through ventricles to subarachnoid space

cushions brain and maintains stable interstitial fluid environment

60
Q

What is the blood brain barrier?

A

specialized network of capillaries that limit exchange of specific substances into the brain

tight junctions between epithelial cells

61
Q

What are the 3 types of white matter fibers in the brain?

A

projection fibers
- connect cerebral cortex with lower brain/spinal cord

association fibers
- connect 2 areas of the cerebral cortex on the same side of the brain

comissural fibers

  • connect 2 of the same cortical regions on either side of the brain
  • corpus callosum
62
Q

What is the spinal cord?

A

cylinder of nerve tissue surrounded by vertebral column

continuous with brain

origin of 31 pairs of spinal nerves

63
Q

What is a dermatome?

A

sensory region of the skin

each served by specific spinal nerve

64
Q

Describe the composition of the spinal cord/nerves.

A

grey matter

  • dorsal horn = sensory/afferent axons
  • ventral horn = motor/efferent axons

white matter
- forms tracts that are either ascending or descending

65
Q

What are reflexes?

A

automatic patterned responses to stimuli

66
Q

What are the components of the reflex arc?

A 
stimulus
sensory receptor
afferent neuron
integrating centre
efferent neuron
effector organ
response
67
Q

What are different ways to classify reflexes?

A

level of neural processing
- spinal vs cranial

efferent division control
- somatic vs autonomic

developmental pattern
- innate vs conditioned

number of synapses
- monosynaptic (only muscle spindle stretch) vs polysnaptic

68
Q

What is the muscle spindle stretch reflex?

A

tap on the tendon causes change in muscle fiber length in quads

spindles detect change and send afferent info to spinal cord, direct excitatory connection with efferent neurons that innervate quad to extend (kick leg)

afferent info also inhibits the hamstrings to allow the movement to occur

69
Q

What is the withdrawal reflex?

A

opposite leg sends afferent signal to extend leg so it can withdraw

gives a leg to stand on so you don’t tip over

70
Q

What is perception?

A

conscious interpretation of the world

71
Q

What is the law of specific nerve energies?

A

a given receptor is specific for each modality

detect specific forms of energy in the external environment

72
Q

What are the different types of sensory receptors?

A

photoreceptors
chemoreceptors
mechanoreceptors
thermoreceptors

73
Q

What do photoreceptors detect?

A

vision - photons of light

74
Q

What do chemoreceptors detect?

A

taste - chemicals in saliva
smell - chemicals in mucus
pain - chemicals in ECF

75
Q

What do thermoreceptors detect?

A

changes in temperature

specific ones for warm and cold

76
Q

What do mechanoreceptors detect? (2 components)

A

pacinian corpuscle
- vibration and pressure

hair cells

  • sound - sound waves
  • balance and equilibrium - acceleration
77
Q

What is sensory transduction?

A

conversion of stimulus energy into electrical energy

78
Q

What is receptor adaptation?

A

decrease in amplitude of receptor potential over time in the presence of a constant stimulus

corresponding decrease in the frequency of AP and in perception of stimulus

79
Q

What is a sensory unit?

A

single afferent neuron plus all receptors associated with it

80
Q

What is a receptive field?

A

area in which sensory unit can be activated

81
Q

Describe the generalized pathway for sensory systems.

A

first order neurons
- transmit from periphery to CNS

second order neurons

  • interneurons
  • may receive info from several first order neurons

third order neurons
- transmit to cerebral cortex for sensory perception

82
Q

What factors affect sensory coding?

A 
stimulus type
stimulus intensity (frequency of AP, # of receptors activated)
stimulus location (size and degree of overlap of receptive field)
83
Q

What does recruitment mean?

A

stronger stimuli activate more receptors

84
Q

What does acuity mean?

A

precision with which a stimulus is perceived

85
Q

What is lateral inhibition?

A

adjacent neurons can form inhibition synapses with branches off axon of activated neuron to allow more accurate sense of precision of where a sensation is coming from

86
Q

What are nociceptors?

A

receptors sensitive to pain

87
Q

Aside from nociceptors, what else is activated in the pain response?

A

autonomic responses
- increased BP, sweating

emotional responses
- fear, anxiety

reflexive withdrawl

88
Q

Describe the 2 pathways of pain.

A

A-delta afferent

  • myelinated
  • initial pain response
  • ex. immediate pain when you first stub your toe

C afferent

  • polymodal
  • delayed response
  • ex. dull ache in toe that comes later on

both terminate in dorsal horn of spinal cord

89
Q

What additional factor determines how you perceive pain?

A

past experiences

90
Q

What is the difference between visceral and referred pain?

A

visceral = pain originating from internal organs

referred = sensation “referred to body surface”
- ex. heart attack victim complains of pain on left side, not heart itself

91
Q

What is the gate control theory?

A

why you rub a painful area to relieve the pain

stimulates pressure-sensitive fibers, collateral axon can stimulate an inhibitory interneuron to reduce pain you initially felt

92
Q

What is endogenous analgesia?

A

brain can block pain

ex. soldiers in battle

KP222 (7 decks)

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