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PHYSL 210 CNS > CNS- Spinal Cord > Flashcards

CNS- Spinal Cord Flashcards

1
Q

what does the spinal cord do

A

conveys signals from sensory receptors to brain and from brain to muscles

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2
Q

what does “You Can Only Control What You Sense” mean

A

if sensory inputs are lost(de-afferentation), control is severely impacted

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3
Q

what is the dorsal root

A

sensory afferents cell bodies are located here, enter via dorsal roots

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4
Q

what is the interface b/w the PNS and CNS (sensory afferents)

A

sensory afferents enter spinal cord via the dorsal root, they’ll split into ascending–>form dorsal columns which will go into the brainstem(carry sensory info) and descending axons–>travel caudally for

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5
Q

what do ascending and descending axons do in the interface b/w PNS and CNS

A

send branches into grey matter of spinal cord that synapse onto interneurons and motorneurons

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6
Q

what is the interface b/w the PNS and CNS (motorneurons)

A

motorneuron cell bodies are located in the ventral horn, motor efferent axons leave spinal cord and form ventral roots

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7
Q

spinal cord tract–> grey matter

A

butterfly shape–> motorneurons, interneurons, dendrites and axons

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8
Q

spinal cord tract–> white matter

A

bundles of axons–> tracts
conveys sensory signals ascending to brain or motor commands descending from brain

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9
Q

what are the ascending tracts

A

sensory info from peripheral nerves is transmitted to cerebral cortex

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10
Q

what are the descending tracts

A

motor signals are sent from brain to lower motor neurons–> innervate muscles and produce movement

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11
Q

how is the spinal cord organized

A

31 spinal nerves–> 8 cervical(C1-C8), 12 thoracic(T1-T12), 5 lumbar(L1-L5), 5 sacral(S1-S5) and 1 coccygeal

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12
Q

what do the cervical nerves do

A

sensory input from head, neck, shoulders, arms and hands

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13
Q

what do the thoracic nerves do

A

sensory info from abdomen (trunk)

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14
Q

what do the lumbar nerves do

A

sensory info from waist, front of legs and feet

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15
Q

what do the sacral and coccygeal nerves do

A

sensory info from butt, genitals, anus, back of legs and feet

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16
Q

what is shingles

A

when the neurons in the dorsal root ganglia, 1 or 2 segments of S.C, become infected with the chicken pox virus that lies dormant until mutated–> those who have chicken pox when young more susceptible

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17
Q

why are dermatones important

A

clinically used to determine the level of a spinal cord injury

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18
Q

how do spinal cord injuries work

A

when the spinal cord gets damaged at a certain level, all sensation and motor function become absent or abnormal, depending on the severity of damage

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19
Q

what happens if there is a complete cut of spinal cord at levels C7-C6

A

paralysis of hand and finger movements but not of breathing control and heart rate, everything below C6-C7 will be impacted

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20
Q

what is modality

A

type of sensory info that is being transmitted
ex. vision, sense of tough, hearing, movement

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21
Q

what does structure of a sensory receptor determine

A

modality of stimulus

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22
Q

what do Meissner’s corpuscles do

A

respond to light touch of skin

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23
Q

what do Merkel’s corpuscles do

A

respond to touch

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24
Q

what is the adequate stimulus

A

modality activating a given receptor

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25
Q

what do free nerve endings do

A

respond to pain

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26
Q

what does the Pacinian corpuscles do

A

respond to vibration or deep pressure

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27
Q

what do ruffini corpuscles do

A

respond to skin stretch
act as thermoreceptors–> warm receptors–> increase firing rate as temp. rises
cold receptors–> increase firing as temp. falls

28
Q

what are the different sensory receptors

A

specialized endings of afferent axons
separate cells that respond to the stimulus and transmit signals via synapses with the afferent neurons

29
Q

what are somatosensory receptors

A

somatosensory–> sensations coming from body
cover surface of body and signal different sensory modalities to CNS

30
Q

what are mechanoreceptors

A

sense local tissue deformation in skin and vice versa

31
Q

what are thermoreceptors

A

sense temperature in skin and brain

32
Q

what are nociceptors

A

sense pain(tissue damage) in skin, vice versa, muscle

33
Q

what are proprioceptors

A

sense movement and force in muscles and joints

34
Q

what are vestibular receptors

A

head acceleration and tilt

35
Q

how does information transfer in NS vary b/w invertebrate and vertebrae

A

mechanism for information transfer in NS is the same for vertabraes and invertabraes, sensory receptors signal stimuli with action potentials in wide range of species (humans, invertebraes and vertabraes)
the

36
Q

what happened in vertebrae and not invertebrates

A

development of the myelin sheath around nerve axons which increases their conduction velocity

37
Q

what are the sensory axons with the fastest conduction velocities

A

type Ia
muscle spindle primary endings
Golgi tendon

38
Q

what are the sensory axons with the slowest conduction velocities

A

type IV
nociceptors
warmth receptor

39
Q

what are the autonomic axon with the fastest conduction velocities

A

preganglionic fibers

40
Q

what are the autonomic axon with the slowest conduction velocities

A

postganglionic fibers

41
Q

what happens as stimulus intensity increases

A

membrane potential at the initial segment of the sensory receptor’s afferent axon increases until AP are generated

42
Q

how are sensory receptors recruited

A

as the stimulus intensity increases it will increase the rate of the AP causing recruitment

43
Q

how are stimulus intensities encoded

A

Frequency code–> bigger the stimulus the more the membrane channels in the sensory endings are distorted, the greater the number of AP/s
Population code–>bigger the stimulus, more sensory neurons are recruited into activity, more AP/s
Temporal pattern code–> variability of firing rate(bursts vs. steady firing) may mediate certain types of sensation

44
Q

what is the duration of stimulus processing

A

slowly adapting (tonic) receptors respond the entire time a stimulus is applied
rapidly respond briefly each time as stimulus changes

45
Q

what does a rapidly adapting receptor do

A

respond briefly whenever the stimulus changes quickly–> Pacinian corpuscles and Meissner’s corpuscles

46
Q

what does a slowly adapting receptors do

A

tonic receptors, respond during the entire time that the stimulus is applied, seen by the continual production of action potentials–> Merkel’s corpuscles, free neuron endings and Ruffini corpuscles

47
Q

what does localization of stimuli depend on

A

density of receptors and sizes of their receptive fields
convergence (one neuron receives inputs from many sensory afferents) and divergence (each sensory afferent sends branches to many neurons in the CNS)
Lateral inhibition

48
Q

what is lateral inhibition

A

sharpens contrast by focusing activation of CNS neurons
stimulus location is perceived more precisely–> increase spatial acuity
remember slide
A and C inhibit B but since B is firing at a higher frequency it will inhibit A and C to a greater extent than A and C to B

49
Q

what is two-point discrimination and how does it relate to acuity

A

a smaller receptive field provides greater spatial acuity
due to the receptors being tightly packed
on lips able to tell that a set of pliers has two tips while on the back receptors are not as tightly packed and the two tips are felt as one –> sensory acuity is relatively low on the back compared to the lips

50
Q

where is two-point discrimination the best and why

A

hands and face, worst on abdomen and proximal parts of limbs
density of receptors is highest in skin areas with the best 2-point discrimination
surface area of sensory cortex is largest in regions to which receptors from skin areas with the best 2-point discrimination project

51
Q

what is sensation

A

the conscious awareness of a stimulus

52
Q

what is perception

A

sensation combined with an understanding of its meaning

53
Q

where do sensation and perception result

A

processing in cerebral cortex

54
Q

which body areas have the greatest representation in sensory cortex

A

face and hands

55
Q

what provides general information about location of a stimulus

A

overlapping stimulation b/w neighbouring receptive fields

56
Q

which body areas have the least representation in sensory cortex

A

abdomen, legs and feet

57
Q

what does descending inhibition do

A

can reduce the intensity of a perceived sensation because it can screen out certain types of sensory information by inhibiting neurons in afferent pathway
two types–> presynaptic inhibition and postsynaptic inhibition

58
Q

what is presynaptic inhibition

A

acts by reducing transmitter release at synapse b/w first and second order sensory neurons
inhibits specific sensations–> pain
lasts several ms

59
Q

what postsynaptic inhibition

A

acts by hyper-polarizing membrane of second-order sensory neurons
non-selective: reduces effect of all synaptic inputs
lasts less than 1 ms

60
Q

what is the process of pain

A

painful stimulus causes tissue damage and releases prostaglandins and histamine–> activate pain receptors, fire APs which travel to the dorsal part of spinal cord–> in the spinal cord, activity of pain fibers causes the release of Substance P which activates interneurons called projection neurons–> signal pain and excite neurons in the thalamus and cortex which results in sensation of pain

61
Q

what is Analgesia

A

suppression of pain transmission

62
Q

how does aspirin work to suppress pain

A

blocks production of prostaglandins which are released as a result of damaged tissue

63
Q

how does Gabapentin work to suppress pain

A

block conduction in nociceptive afferents–> C-fibre axons

64
Q

how does opioids work to suppress pain

A

in CNS will block release of Substance P onto the projection neurons in spinal cord

65
Q

what is referred pain

A

sensation of pain that is experienced at a site other than the injured or damaged tissue

PHYSL 210 CNS (3 decks)

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