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A&P module 4 CNS > 4.4 > Flashcards

4.4 Flashcards

1
Q
  • Integration of sensory information occurs at all levels of the CNS with the highest level of integration taking place in _____
A

the cerebral cortex -

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2
Q

generation and propagation of a series of action potentials in an afferent neuron

A

Neural encoding generation and propagation of a series of action potentials in an afferent neuron

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3
Q

conversion of physical energy (chemical, mechanical, thermal, or electromagnetic) into electrochemical energy (local potential) by the receptor

A

Stimulus transduction

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4
Q

A sensory receptor organ consists of one or more cells and possibly noncellular structures whose function is _____

A

transduction -

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5
Q

the unique type of energy (stimulus) that best activates a specific receptor and therefore a particular type of afferent nerve fiber

A

Adequate stimulus -

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6
Q

The ____ of a sensory nerve fiber isn’t absolute

A

specificity

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7
Q

If the amplitude of the receptor potential is large enough, the membrane is ____ and an ____ is triggered

A

depolarized to threshold, action potential -

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8
Q
  • Action potential firing frequency is ___ to the amplitude of the receptor potential
A

proportional

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9
Q
  • The amplitude of the receptor potential is ____ to the strength of the stimulus
A

proportional -

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10
Q

The receptor potential is ____, not all-or-nothing

A

graded -

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11
Q

Vibration receptors (Pacinian corpuscles) in subcutaneous tissue adapt in ____

A

hundredths of a second

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12
Q
  • Chemoreceptors adapt in ____
A

weeks or months

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13
Q
  • Baroreceptors adapt in ____
A

hours or days

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14
Q

Nociceptors adapt in ____

A

let’s just say they don’t

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15
Q
  • Sensory modality is encoded by a ____ code
A

“labeled line”

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16
Q

Since a receptor is maximally sensitive to only one specific stimulus energy, every afferent nerve fiber is a modality-specific ____

A

line of communication (“labeled line”)

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17
Q

Each type of receptor and afferent nerve fiber has a different set of ___; whether you feel pain or touch depends on the receptor and its central connections

A

connections in the CNS

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18
Q

No matter how a “labeled line” is stimulated, the stimulus will be interpreted by the brain as ____ for which the nerve fiber is specialized.

A

the specific modality -

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19
Q

Electrical stimulation of the cochlear nerve in the inner ear will be perceived as a ___, not ___

A

sound, touch or pain

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20
Q

Electrical stimulation of the olfactory nerve will be perceived as a ___

A

smell -

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21
Q
  • This law is responsible for the phenomenon of phantom limb syndrome
A

Law of projection -

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22
Q

no matter where a sensory pathway is stimulated along its course to the cerebral cortex, the conscious sensation produced is interpreted as coming from the site of the peripheral receptive field

A

Law of projection -

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23
Q
  • Higher action potential frequency causes greater ___ at the synapses in a sensory pathway
A

temporal summation

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24
Q

in addition to temporal summation, stronger stimuli can also activate a greater number of sensory receptors (spatial summation). Activating more receptors

A

Population code

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25
Q
  • In slow adapting receptors, stimulus duration is signaled by the interval during which____
A
  • In slow adapting receptors, stimulus duration is signaled by the interval during which____
    impulse firing is increased
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26
Q

Fast-adapting receptors signal the onset and offset of a stimulus with a ____ or a brief, high-frequency train of action potentials

A

single action potential -

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27
Q

involved with sensing pain

A

Insula:

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28
Q

involved with emotions

A

Cingulate gyrus

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29
Q

involved with fear and its sympathetic response

A

Amygdala

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30
Q

helps form and retrieve memories - Four structural components involved in interpreting pain:

A

Hippocampus

helps form and retrieve memories - Four structural components involved in interpreting pain:

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31
Q

Because nociceptive signals can be inhibited in the CNS (i.e., antinociception), nociception does not always lead to the ____

A

perception of pain

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32
Q

Nociceptors are ___ in the skin and in most internal structures (periosteum, vessel walls, joint surfaces, dura mater)

A

widespread -

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33
Q

Nociceptors are absent from ___

A

the brain and spinal cord and lung parenchyma

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34
Q

Three major types of nociceptors:

A

Mechanical nociceptors
Thermal nociceptors
Polymodal nociceptors

35
Q

Respond to intense mechanical pressure applied to the skin, Aδ nerve fibers; medium fast conduction velocity (5-30 meters per second)

A

Mechanical nociceptors

36
Q

Respond to high-intensity mechanical, thermal (heat or cold), or chemical stimuli

A

Polymodal nociceptors -

37
Q

Polymodal nociceptors

what type of fiber

A

C fibers slow conduction velocity (<1 meter per second)

38
Q

Respond to extreme temps (damaging or potentially damaging levels) of heat and cold (>113° F and <41° F)

A

Thermal nociceptors -

39
Q

Thermal nociceptors
what type of fiber
two for different sensations

A 
Aδ nerve fibers (medium fast conduction velocity [5-30 meters per second]) respond to cool temps
C fibers (slow conduction velocity [0.5-2 meters per second]) respond to heat
40
Q

Nociceptors are sensitized by a variety of chemicals released by damaged cells in the vicinity of an injury

A

lower the threshold -

41
Q

These substances ___ for activation of nociceptors
Examples of chemicals that sensitize nociceptors are:
brady, tom
has
sensitive
palms

A

bradykinin, histamine, prostaglandins and serotonin (i.e., 5-HT) - Examples of chemicals that sensitize nociceptors are:

42
Q

Neuroactive substances are released by the peripheral end of an activated nociceptive pseudounipolar neuron

A

backfiring neuron”

43
Q

These peptides contribute to the development of ____ in injured tissue by causing local vasodilation; they also encourage release of ____ which sensitizes the nociceptors

A

A “backfiring neuron” will release:
Substance P and CGRP
These peptides contribute to the development of edema in injured tissue by causing local vasodilation; they also encourage release of histamine from mast cells which sensitizes the nociceptors

44
Q 
Fast pain ("first pain")
receptor 
transmitted by what fibers? 
what type of pain
purpose?
A

Fast pain (“first pain”)
Perception begins within 0.1 msec of a stimulus
Transmitted by Aδ fibers that carry signals from thermal or mechanical nociceptors
Carried by medium-to-large diameter, myelinated Aδ fibers that conduct at 5-30 meters per second (intermediate speed)
Associated with “sharp”, “stabbing” pain
Purpose: rapidly generates motivation to stop or move away from a damaging stimulus

45
Q

pain from hollow organs

A

Visceral pain

46
Q

Pain receptors on hollow organs are ____ distributed

A

diffusely

47
Q 
Slow pain ("second pain")
receptors?
fiber
pain type 
purpose
A

Perception begins within seconds of a stimulus
Transduced primarily by polymodal nociceptors
Carried by small-diameter, unmyelinated C fibers that conduct at <1 meter per second (slow)
Associated with “dull”, “aching” persistent pain
Purpose: persistent reminder of tissue injury that provides motivation to care for and protect the injured area

48
Q

Transmission of visceral pain: afferent fibers get into the CNS by traveling within the same nerves (not nerve fibers) that carry ___ to the viscera

A

autonomic innervation

49
Q

Visceral pain in the pharynx, larynx, trachea, and upper esophagus is transmitted via ___, which also carry parasympathetic nerve fibers

A

cranial nerves IX and X

50
Q

Visceral pain in the distal colon, rectum, urinary bladder, and testes or cervix is transmitted via ___ which also carry parasympathetic nerve fibers

A

spinal nerve S2-S4 -

51
Q

Visceral pain in most organs of the thorax and abdomen is transmitted via ___ (e.g., splanchnic nerves) into the spinal cord

A

sympathetic nerves

52
Q

Characteristics of visceral pain:

A

a. Extreme unpleasantness, aching, or burning
b. Poorly localized
c. Typically referred to the body surface

53
Q

The CNS has modulatory circuits at many levels (cerebrum, diencephalon, midbrain, pons, medulla and spinal cord) whose function is to alter the ____

A

perception of pain

54
Q

G protein-coupled opioid receptors are involved in modulating ___

A

pain perception

55
Q

Opioids (i.e., enkephalin and endorphins) are generally released from ___

A

inhibitory interneurons

56
Q

Presynaptically, opioid receptor activation causes ___, which depresses neurotransmitter release

A

closure of voltage gated Ca2+ channels

57
Q

Postsynaptically, opioid receptor activation opens ___, resulting in IPSPs and inhibition of action potential firing

A

Postsynaptically, opioid receptor activation opens ___, resulting in IPSPs and inhibition of action potential firing
ligand gated K+ channels -

58
Q

The initial site of CNS pain modulation is in ____

A

the dorsal horn of the spinal cord

59
Q

According to this theory, nociceptive afferents are modified by non-nociceptive (typically tactile) afferents

A

gate control theory

60
Q

Enkephalin binds to opioid receptors on both the ___ (i.e., C fiber nociceptive afferent) and the ____ (excitatory interneuron) neuron.

A

presynaptic, postsynaptic

61
Q

Presynaptic effects of Enkephalin:

A

(i) Closure of voltage-gated Ca2+ channels
(ii) ↓ neurotransmitter release
(iii) Less nociceptive information sent up the spinothalamic tract

62
Q

Involves a ____ and a ____ that synapses on enkephalin- secreting, inhibitory interneuron. The nociceptive afferent and the inhibitory interneuron synapse on the same excitatory interneurons. If the faster-conducting, tactile Aβ fibers are activated concurrently with slower-conducting, nociceptive C fibers, the inhibitory interneurons are activated more often. The net is less transmission of pain information to the brain.

A

nociceptive afferent, tactile afferent - Mechanism of the gate control theory:

63
Q

Postynaptic effects of Enkephalin:

A

Postynaptic effects of Enkephalin:

(i) Opening of voltage-gated K+ channels
(ii) Hyperpolarization (i.e., IPSP) of the postsynaptic neuron.
(iii) Decreased probability of activating an action potential in the spinothalamic tract.

64
Q

____ is often referred to as the “fast pain” or “discriminative” or “lateral” pain pathway

A

The spinothalamic tract - Ascending fast pain pathway

65
Q

The spinothalamic tract brings fast pain primarily to the ____. Most fibers are of the Aδ variety (discriminative nociception) or C fibers for detecting heat

A

somatosensory cortex -

66
Q

Acute pain is typically both ____. The slow pain aspect of acute pain is carried by these slow pain pathways while fast pain is carried by the spinothalamic tract (a 3 neuron pathway)

A

fast and slow

67
Q

These pathways terminate on ____ of the CNS (brain stem, portions of the limbic system or non-somatosensory regions of the cortex).

A

medial aspects - Slow pain pathways typically utilize unmyelinated, polymodal C fibers (slow)

68
Q

The slow pain pathways do not always utilize 3 neurons like the spinothalamic tract but they do tend to run alongside it and are also located in the ____ of the spinal cord

A

anterolateral columns -

69
Q

Since slow pain pathways do not terminate on the somatosensory cortex, they are not ____ regarding the source of the pain, they are the “diffuse” pathways

A

well- mapped -

70
Q

There are three slow pain pathways:

A

Spinomesenphalic
Spinoreticular
Spino-emotional

71
Q

Terminates at the midbrain (periaqueductal gray [PAG])

PAG activates descending pathways to modulate incoming pain signals

A

Spinomesenphalic

72
Q

Terminates at the brainstem’s reticular formation (center for arousal, attention & sleep-wake cycles)
Thus, slow pain draws attention to the pain and may interrupt sleep

A

Spinoreticular

73
Q

These pathways receive input from ascending pathways and then send signals back down to the spinal cord in order to inhibit the ascending pain signals.

A

Descending pain pathways

74
Q

Three primary descending tracts:

A

Raphespinal tract
Ceruleospinal tract
Unnamed tract originating in the Periaqueductal Gray (PAG

75
Q

Originates in the raphe nucleus of the upper medulla
Receives innervation from the spinoreticular tract and from the Periaqueductal Gray (PAG)
Secretes serotonin
Synapses on an inhibitory interneuron (enkephalin-secreting) that eventually inhibits the ascending pathways

A

Raphespinal tract

76
Q

Originates in the locus coeruleus (“blue spot”) at the junction of the midbrain and the pons
Receives innervation from the spinoreticular tract and from the Periaqueductal Gray (PAG)
Secretes norepinephrine (NE)
Synapses on and suppresses the nociceptive C afferent via presynaptic inhibition
Mechanism of presynaptic inhibition involves α2 receptors, which activate Gi
inhibits voltage-gated Ca2+ channels (i.e., ICa) leads to ↓ norepinepherine release

A

Ceruleospinal tract

77
Q

Electrical stimulation of ___ produces “electrical analgesia” sufficient to perform surgery on anaesthetized animals

A

the PAG

78
Q

Neurons here send their axons down to the raphe nucleus and the locus coeruleus and make excitatory connections
Receives innervation from the spinomesenphalic tract and indirectly from the spinoemotional tract
Stimulation of this area causes profound analgesia without the loss of the other modalities of somatosensation (e.g., proprioception, discriminative touch, etc.).

A

Unnamed tract originating in the Periaqueductal Gray (PAG)

79
Q

Microinjection of ____ into the PAG inhibits GABAergic inhibitory interneurons that tonically suppress the PAG

A

morphine

80
Q

Microinjection of ___ into the PAG reverses the effects of systemically administered morphine

A

naloxone

81
Q

Members of the limbic system ____, ____ and ____ are key centers in this level of antinociception;expectations, excitement, distractions and placebos can all play a role in this pathway

A

Members of the limbic system ____, ____ and ____ are key centers in this level of antinociception;expectations, excitement, distractions and placebos can all play a role in this pathway
the cingulate cortex, the insula and amygdala

82
Q

Hormones and anticonception

A

endorphins, epinephrine and norepinephrine

83
Q

Anterior pituitary purportedly releases ____

A

endorphins

84
Q

Adrenal medulla releases ____ that presynaptically inhibit the primary nociceptive afferent (just like the ceruleospinal tract of the descending pain pathways)

A

epinephrine and norepinephrine

A&P module 4 CNS (7 decks)

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