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A-BIOL 1191 LECTURE > CH 16 > Flashcards

CH 16 Flashcards

1
Q

what is sensation?

A

conscious/subconscious awareness of stimuli external/internal to body

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2
Q

what does the nature of sensation and complexity/type of reaction generated depend on?

A

the destination of the input

(ex. sensations processed in spinal cord are simple reflexes, sensations processed in cerebral cortex we will be consciously aware of)

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3
Q

what is perception?

A

conscious awareness and interpretation of a sensation

  • must involve cerebral cortex
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4
Q

where are memories of our perceptions stored?

A

in the cerebral cortex

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5
Q

what are some stimuli our bodies are not aware of?

A

UV light, X-rays, ultra high frequency sound waves

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6
Q

what is a sensory modality?

A

a specific type of sensation (touch, pain, temp, smell, etc.)

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7
Q

what is receptor specificity?

A

a particular sensory neuron only carries info for one sensory modality

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8
Q

what are the two classes of sensory modalities?

A
  • general senses
  • special senses
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9
Q

what are types of general senses?

A
  • somatic
  • visceral
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10
Q

what are some somatic senses?

A
  • thermal
  • tactile
  • pain
  • proprioception
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11
Q

what are some visceral senses?

A

condition of internal organs (stretching, pressure, chemical)

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12
Q

what are some special senses?

A
  • vision
  • gustation
  • olfaction
  • hearing
  • equilibrium
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13
Q

how are sensations made?

A

starts w/ sensory receptor receiving specific stimulus

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14
Q

what is stimulus selectivity?

A

sensory receptors only responsive to some types of stimuli

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15
Q

how do sensations arise?

A
  1. SIGNAL SENSING: specific stimulus approaches cognate sensory receptor’s receptive field (area of receptor where signals received)
  2. SIGNAL TRANSDUCTION: energy transduced (converted to graded potential)
  3. SIGNAL PROPAGATION: if reaches threshold, nerve impulse generated
  4. SIGNAL INTEGRATION: nerve impulses integrated at cerebral cortex
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16
Q

what are first order neurons?

A

sensory neurons that conduct nerve impulses from PNS to CNS

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17
Q

where are nerve impulses integrated so we can be conscious of them?

A

at cerebral cortex

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18
Q

what are structural classifications of sensory receptors?

A
  • free nerve endings of 1st order neurons
  • encapsulated endings of 1st order neurons
  • separate cells
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19
Q

what are receptor location classifications of sensory receptors?

A
  • exteroceptors
  • interoceptors
  • proprioceptors
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20
Q

what are classifications of sensory receptors based on type of stimuli detected?

A
  • mechanoreceptors
  • thermoreceptors
  • nociceptors
  • photoreceptors
  • chemoreceptors
  • osmoreceptors
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21
Q

what are free nerve endings?

A
  • bare dendrites of 1st order neuron
  • senses some somatic senses (pain, temp, tickle, itch, light touch)
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22
Q

what are encapsulated nerve endings?

A
  • dendrites of 1st order neuron enclosed in connective tissue capsule
  • senses some somatic senses (pressure, vibration, deep touch)
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23
Q

what are separate sensory cells?

A

specialized cells that respond to stimuli and then synapse w/ 1st order neurons (not 1st order neurons themselves!)

  • stimulus generated graded potential in receptor cell, receptor cell releases neurotransmitter onto 1st order sensory neuron, generating postsynaptic potential
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24
Q

what are exteroceptors?

A

receptors found near surface of body to detect external stimuli

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25
Q

what are interoceptors?

A

receptors located internally to monitor internal environment
- usually subconscious except pain/pleasure

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26
Q

what are proprioceptors?

A

receptors that sense body position and movement, muscle length and tension located IN muscles, tendons, joints, inner ear

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27
Q

what are mechanoreceptors?

A

receptors that detect mechanical stimuli, including stimuli that deform, stretch, or bend cells

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28
Q

what are thermoreceptors?

A

receptors that detect temp changes

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29
Q

what are nociceptors?

A

receptors that detect tissue damage, leading to pain

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30
Q

what are photoreceptors?

A

receptors that detect light

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31
Q

what are chemoreceptors?

A

receptors that detect chemicals

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32
Q

what are osmoreceptors?

A

receptors that detect osmotic pressure in fluids

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33
Q

what is receptor adaptation?

A

tendency for receptor potentials to decrease in amplitude due to maintained, constant stimulus

  • tells body this is the new normal
  • perception of sensation fades/disappears even if stimulus persists
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34
Q

what are rapidly adapting receptors?

A

receptors that specialize in detecting changes in stimulus

  • ex. smell, touch, vibration
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35
Q

what are slowly adapting receptors?

A

receptors where nerve impulses continue for duration of stimulus because receptor adaptation is slow

  • ex. pain, body position, chemicals in blood
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36
Q

what are cutaneous sensations?

A

sensations felt on skin

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37
Q

what are tactile sensations?

A

includes touch, pressure, vibration, itch, tickle

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38
Q

what does touch stimulate?

A
  • tactile corpuscles
  • hair root plexuses
  • nonencapsulated sensory corpuscles
  • bulbous corpuscles
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39
Q

what are tactile corpuscles?

A

rapidly adapting touch receptors found in dermal papillae

  • encapsulated nerve endings abundant in fingertips, hands, eyelids, lips, nipples, etc.
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40
Q

what are hair root plexuses?

A

rapidly adapting touch receptors coiled around hair follicles

  • free nerve endings that detect stimuli to move hair at surface of skin
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41
Q

how are rapidly adapting receptors able to relay fast signals?

A
  • they relay signals to large-diameter myelinated neurons

– myelinated
– large-diameter, greater SA for transduction

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42
Q

what are nonencapsulated sensory corpuscles?

A

flat, plate-like free nerve endings that directly contact tactile epithelial cells that help you sense objects you are holding for lengthy periods

  • slow adapting touch receptors abundant in fingertips, hands, lips, external genitalia
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43
Q

what are bulbous corpuscles?

A

long, encapsulated receptors embedded in dermis and subcutaneous tissue sensitive to tissue stretching

  • slow adapting touch receptors
  • capsule enclosing the branched nerve endings are Schwann cells
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44
Q

how is pressure different from touch?

A

felt over a larger surface area

requires deeper deformation of skin + subcutaneous tissue

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45
Q

what receptors detect pressure?

A
  • lamellar corpuscles
  • bulbous corpuscles

bulbous corpuscles are slow adapting, can respond to steady, constant pressure

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46
Q

what receptors detect vibration?

A
  • lamellar corpuscles: high-frequency vibration
  • tactile corpuscles: low-frequency vibrations
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47
Q

what receptors detect itch?

A

free nerve endings
- involves chemicals (bradykinin, histamine, antigens)
- response to inflammation
- relay signals to small-diameter, unmyelinated neurons

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48
Q

what does scratching itches do?

A

relieves sensation of itching by activating pathway that inhibits itch signal transmission through spinal cord

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49
Q

what receptors detect tickle?

A

free nerve endings when someone else touches you
- relay signals to small-diameter, unmyelinated neurons

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50
Q

why do tickle receptors only activate when someone touches you?

A

nerve impulses from cerebellum interfere w/ ability to tickle yourself, as cerebellum anticipates movement

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51
Q

what are cold receptors?

A

free nerve endings w/ receptive fields ~1mm from skin surface located in stratum basale
- activated by temps 10-35°C
- relay signals to small-/medium-diameter myelinated neurons

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52
Q

what are warm receptors?

A

free nerve endings w/ receptive fields ~1mm from skin surface located in dermis
- activated by temps 30-45°C
- relay signals to small-diameter unmyelinated nerve fibres
- less abundant than cold fibres

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53
Q

why are cold receptors faster than warm receptors?

A

cold receptors relay signals to small-/medium-diameter myelinated neurons

warm receptors relay signals to small/diameter unmyelinated neurons
- also less abundant than cold receptors

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54
Q

what are nociceptors?

A

free nerve endings that sense pain
- above 45°C or less than 10°C
- intense stimuli lead to release of pain mediating chemicals (kinins, prostaglandins)

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55
Q

why does pain persist long after painful stimulus is gone?

A

nociceptors have little tendency to adapt

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56
Q

what is fast pain?

A

acute, sharp, prickling pain occurring ~0.1s after stimulus occurs

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57
Q

what is slow pain?

A

chronic, burning, aching, throbbing sensation occurring over 1s after stimulus, often increasing in intensity over time

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58
Q

what is superficial somatic pain?

A

pain arising from cutaneous nociceptor stimulation

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59
Q

what is deep somatic pain?

A

pain arising from stimulation of nociceptors in deeper tissues, including skeletal muscles, joints, tendons, fascia

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60
Q

what is visceral pain?

A

pain arising from stimulation of nociceptors in viscera/internal organs
- menstruation, kidney stones blocking ureters

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61
Q

what is referred pain?

A

pain sensations from stimulation of visceral nociceptors that are felt in the superficial tissues

  • superficial tissues and viscera mediated by same segment of spinal cord that suppies affected visceral tissue
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62
Q

what are evolutionary functions of pain?

A

pain acts as a signal to avoid or get away from evasive, painful stimuli

  • lets us not injure ourselves further without knowing stimulus might kill us
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63
Q

what do proprioceptive sensations permit?

A
  • recognizing one’s own body parts as self
  • registering where our body is in 3D space as we move
  • discriminating weight of loads
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64
Q

what is kinesthesia?

A

perception (conscious awareness) of body movements

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65
Q

what are proprioceptors?

A

slowly adapting sensory receptors that help us sense proprioceptive sensations

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66
Q

what are muscle spindles?

A

encapsulated nerve ending proprioceptors wrapped in CT and anchored to fascia of intrafusal fibres that sense changes in muscle length
- associated w/ gamma motor neurons

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67
Q

what are gamma motor neurons?

A

neurons that attach to ends of intrafusal fibres and adjust their tone as muscle length changes

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68
Q

why are gamma motor neurons important when muscles are contracted?

A

because muscles are contracted, the length decreases and muscle spindles desensitized to sense changes

gamma motor neurons keep intrafusal fibres extended to maintain their sensitivity to changes in muscle length

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69
Q

what are extrafusal muscle fibres?

A

muscle fibres that function in contraction
- associated w/ alpha motor neurons

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70
Q

what are alpha motor neurons?

A

neurons that send ACh to extrafusal fibres, stimulating skeletal muscle to contract
- associated w/ large-diameter myelinated nerve fibres

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71
Q

what are tendon organs?

A

propioceptors with free nerve endings that wrap around tendon fascicles, collagen fibres within the tendons that sense changes in muscle tension

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72
Q

what are joint kinesthetic receptors?

A

free nerve endings and bulbous capsules in articular capsule of synovial joints that respond to changes in pressure on joints

  • lamellar corpuscles external to articular capsule sense speed of joint movements
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73
Q

what are first order neurons?

A

neurons that relay nerve impusles from sensory receptors → 1) spinal cord OR 2) brainstem

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74
Q

what are second order neurons?

A

interneurons that conduct nerve impulses from spinal cord/brainstem → thalamus

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75
Q

what are third order neurons?

A

interneurons that conduct nerve impulses from thalamus → primary somatosensory cortex

76
Q

what are relay stations?

A

synapses btwn sets of neurons

  • thalamus
  • spinal cord
  • brainstem
77
Q

what are the three major somatosensory pathways?

A
  1. posterior column-medial lemniscus pathway
  2. spinothalamic pathway
  3. trigeminothalamic pathway
78
Q

which sensations are relayed by the posterior column-medial lemniscus pathway?

A

conveys tactile sensations from peripheral sensory receptors → cerebral cortex

(touch, pressure, vibration, itch, tickle)

79
Q

where do neurons decussate in the posterior column-medial lemniscus pathway?

A

axons decussate in brainstem

80
Q

where do signals go in the posterior column-medial lemniscus pathway?

A

axons terminate at primary somatosensory cortex

81
Q

which sensations are relayed by the spinothalamic pathway?

A

conducts nerve impulses from peripheral receptors for:

  • pain
  • temperature
  • touch
82
Q

where do neurons decussate in the spinothalamic pathway?

A

axons decussate in the spinal cord

83
Q

where do signals go in the spinothalamic pathway?

A

axons terminate at primary somatosensory cortex

84
Q

which sensations are relayed by the trigeminothalamic pathway?

A

peripheral receptors conduct facial senses to pons for:
- pain
- temperature
- touch
- proprioception

85
Q

where do neurons decussate in the trigeminothalamic pathway?

A

axons decussate in the brainstem

86
Q

where do signals go in the trigeminothalamic pathway?

A

axons terminate at the primary somatosensory cortex

87
Q

what determines the area of the primary somatosensory cortex devoted to processing sensations from each part of the body?

A

the number of sensory receptors found in the body part

88
Q

what do axon collaterals from sensory neurons that conduct nerve impulses to the cerebellum permit?

A

unconscious aspects of proprioception

89
Q

what are two major sensory tracts that DO NOT decussate?

A
  • anterior spinocerebellar tract
  • posterior cerebellar tract
90
Q

what do the anterior and posterior cerebellar tracts permit?

A

convey nerve impulses from proprioceptors of one side of body to same side of cerebellum

  • they are required for posture, balance, and coordination of skilled movements
  • not consciously perceived
91
Q

what are lower motor neurons?

A

motor neurons that conduct nerve impulses from brainstem and cerebral cortex → skeletal muscles directly

92
Q

what are upper motor neurons?

A

interneurons in upper brain centres extending from cerebral cortex, synapsing w/ either interneurons or lower motor neurons

  • regulating balance, posture, muscle tone, reflexive movements of head and neck
  • their cell bodies are located in upper brain centres
93
Q

what are the four major neural circuts that conduct impulses from brain to lower motor neurons?

A
  • local circuit neurons
  • upper motor neurons
  • corpus striatum neurons
  • cerebellar neurons
94
Q

what are local circuit neurons?

A

interneurons located close to cell bodies of lower motor neurons in brainstem/spinal cord that receive sensory input from nociceptors, muscle spindles, higher bran centres

  • regulate rhythmic movement (flexion/extension while walking)
95
Q

what are corpus striatum neurons?

A
  • provide input to upper motor neurons through additional circuits to cerebral cortex and brainstem
  • regulate starting/stopping movements, suppressing unwanted movement, establishing muscle tone
96
Q

what are cerebellar neurons?

A
  • control activity of upper motor neurons; activity is connected to cerebral cortex and brainstem
  • corrects errors in movement
  • not involved in initiating movement
97
Q

what does control of body movement involve?

A
  • motor portions of cerebral cortex (premotor cortex and primary motor cortex)
  • corpus striatum
  • cerebellum
98
Q

what is cortical area devoted to a muscle proportional to?

A

the number of motor units devoted to a muscle

  • large muscles have less motor units, gross movements
  • small muscles have more motor units, fine movements
99
Q

what are direct motor pathways?

A

axons of neurons in primary motor cortex synapse directly with lower motor neurons

  • axons descend from pyramidal cells in primary motor cortex
100
Q

what are the two main direct motor pathways?

A

1) corticospinal pathway

2) corticobulbar pathway

101
Q

what are indirect motor pathways?

A

axons of neurons in brainstem provide input to lower motor neurons

  • all motor pathways except corticospinal and corticobulbar are indirect
  • axons from upper motor neurons descend from various motor nuclei in brainstem into 5 major tracts, synapsing w/ local circuit neurons or lower motor neurons
  • all control involuntary movement (except rubrospinal)
102
Q

what does the corticospinal pathway control?

A

movement of trunk and limbs

103
Q

what does the lateral corticospinal pathway control?

A

skilled movements of hands and feet

104
Q

what does the anterior corticospinal pathway control?

A

movement of trunk and proximal portions of limbs (arms and legs)

105
Q

what does the corticobulbar pathway control?

A

movement of skeletal muscles in head and face: eyes, tongue, neck, expression, speech, chewing, swallowing

106
Q

where do signals come from in the lateral corticospinal pathway?

A

from primary motor cortex

107
Q

where do neurons decussate in the lateral corticospinal pathway?

A

in brainstem (pyramids of medulla)

108
Q

where do nerve impulses end in the lateral corticospinal pathway?

A

lower motor neurons exits spinal cord through anterior root of spinal nerves to skeletal muscles

109
Q

where do signals come from in the anterior corticospinal pathway?

A

in the primary motor cortex

110
Q

where do neurons decussate in the anterior corticospinal pathway?

A

spinal cord (anterior white commissure)

111
Q

where do axons end in the anterior corticospinal pathway?

A

lower motor neurons exit through anterior grey horn to skeletal muscles

112
Q

where do signals come from in the corticobulbar pathway?

A

primary motor cortex

113
Q

where do neurons decussate in the corticobulbar pathway?

A

some tracts decussate, others don’t

114
Q

where do axons end in the corticobulbar pathway?

A

lower motor neurons of cranial nerves end at effectors (skeletal muscles of head and face)

115
Q

what is the vestibulospinal pathway?

A

maintains posture and balance

  • from vestibular nuclei (CN VIII, pons) → spinal cord
116
Q

what are the lateral and medial reticulospinal pathways?

A

facilitate flexor and extensor reflexes to regulate muscle tone
- medial excites muscles
- lateral inhibits muscles
- from reticular formation → spinal cord

117
Q

what is the tectospinal pathway?

A

moves head, trunk, and eyes in response to visual or auditory stimuli

  • from superior colliculi (midbrain) → spinal cord
118
Q

what is the rubrospinal pathway?

A

allows for precise movements in distal upper limbs

  • voluntary
  • from red nuclei (midbrain) → spinal cord
119
Q

how does the corpus striatum function in motor control?

A
  • movement initiation and termination
  • regulation of muscle tone
  • regulation of nonmotor processes
120
Q

how does the corpus striatum function in initiating and terminating movements?

A
  • receives input from sensory, association, and motor cortex
  • output to thalamus → upper motor neurons in motor cortex
  • disorders associated w/ movement defects include huntington’s disease, parkinson’s disease
121
Q

how does the corpus striatum function in regulating muscle tone?

A

corpus striatum neurons interact w/ reticular formation, and the medial and lateral reticulospinal tracts, facilitating muscle tone

122
Q

how does the corpus striatum function in regulating nonmotor processes?

A

helps regulate memory, attention, planning, emotions

123
Q

what are the four aspects of cerebellar function?

A
  1. monitors intentions for movements
  2. monitors actual movement via proprioceptors
  3. compares intention with actual movements
  4. sends corrective feedback
124
Q

why is a reflex faster than voluntary movements?

A

reflex arcs have less connections that have to happen

voluntary movements involve more synapses and connections made

125
Q

Anand has had a serious accident. He lost sensation of pain and
temperature in the right side of the body. Which tracts carry sensory information about pain and temperature?

A

Spinothalamic tracts

126
Q

what are some integrative functions of the cerebrum?

A
  • consciousness
  • learning
  • memory
  • emotional responses
  • language
127
Q

what is integration?

A

the processing of sensory information by analyzing it and storing it and making decisions for various responses

128
Q

what are sleep and wakefulness controlled by?

A

reticular activating system of the reticular formation

129
Q

how does arousal occur?

A

when the reticular activating system is activated, cerebral cortex also activated

130
Q

what is consciousness?

A

state of wakefulness from the activation of the reticular activating system and the cerebral cortex

131
Q

what inputs can activate the reticular activating system?

A
  • pain
  • light
  • touch
  • noise
  • muscle activity
  • touch
132
Q

what inputs CANNOT activate the reticular activating system?

A

smell

133
Q

what is Adenosine?

A

sleep-inducing neurotransmitter in brain that inhibits RAS activity

134
Q

how does caffeine and theophylline in tea prevent sleepiness?

A

they bind to adenosine receptors, blocking adenosine from binding, preventing sleep-inducing effects of adenosine

135
Q

what are two components of normal sleep?

A

NREM sleep and REM sleep

136
Q

what is NREM sleep?

A

non rapid eye movement sleep

  • inactive brain
  • active body
137
Q

what is REM sleep?

A

rapid eye movement sleep

  • active brain
  • inactive body
138
Q

what occurs during NREM-1?

A

person is drifting off with eyes closed (first few minutes)

139
Q

what occurs during NREM-2?

A

light sleep

  • fragments of dream may occur
  • eyes roll from side to side
140
Q

what occurs during NREM-3?

A

moderate deep sleep (after ~20min)

  • person relaxed
  • body temp, heart rate, blood pressure decrease
141
Q

what occurs during NREM-4?

A

deepest sleep level

  • reflexes and muscle tone intact
  • difficult to wake person up during this stage
  • bed-wetting and sleepwalking occur during NREM-4
142
Q

describe cycle of sleep stages

A

takes ~90-120min

NREM1 → NREM2 → NREM3 → NREM4 → NREM3 → NREM2 → NREM1 → REM

143
Q

what sleep stage does most dreaming occur?

A

REM

144
Q

how many stages of REM occur during 7-8hrs of sleep?

A

4-5 episodes, increasing in length (1st is ~10min, last is ~50min)

145
Q

what is the total amount of time spent in REM sleep?

A

90-120 minutes

146
Q

describe how total amount of time spent in REM sleep changes over a person’s lifetime

A

decreases with age

  • 50% REM in infants, ~25% in adults
147
Q

in which sleep stage is neuronal activity and oxygen use the highest?

A

REM sleep, exceeding intense mental and physical activity

148
Q

what results in paralysis of skeletal muscles?

A

motor neurons are inibited (except for breathing and eye movements)

149
Q

what are some proposed functions of sleep?

A
  • memory consolidation
  • brain maturation
  • enhancement of immune system function
  • body repair and restoration
150
Q

what is learning?

A

the ability to acquire new information or skills through instruction/experience (behavioural change)

151
Q

what is associative learning?

A

learning based on connection between two stimuli

152
Q

what is non-associative learning?

A

learning based on repeated exposure to a stimuli

153
Q

what is habituation?

A

repeated exposure to an irrelevant stimulus causes decreases behavioural response

154
Q

what is sensitization?

A

repeated exposure to a harmful stimulus causes increased behavioural response

155
Q

what is memory?

A

process by which information acquired through learning is stored and retrieved

  • storage
  • retrieval
156
Q

what is declarative (explicit) memory?

A

experiences that can be verbalized or declared (events, names, facts, semantic and episodic memories)

  • requires **conscious recall*
  • stored in cerebral cortex
157
Q

what is procedural (implicit) memory?

A

memory of motor skills, rules, procedures

  • no conscious recall required
  • stored in basal ganglia/corpus striatum and cerebellum
158
Q

what is short-term memory?

A

briefly activated memory of a few items that is later stored or forgotten, ability to recall pieces of information for a short period of time (seconds or minutes)

  • involved hippocampus, thalamus, hypothalamus, frontal lobe
159
Q

how is short-term memory transformed to long-term memory?

A

by memory consolidation
- repetition contributes to memory consolidation

160
Q

what is memory consolidation?

A

process of distributing memories throughout brain

161
Q

what is long-term memory?

A

memory that lasts from days to years
- related to anatomical and biochemical changes at synapses

162
Q

where LTM for info that can be verbalized stored in?

A

cerebral cortex

163
Q

where is LTM for motor functions stored in?

A
  • corpus striatum
  • cerebellum
  • cortex
164
Q

what stimulates short-term memory as stored into long-term memory?

A

hippocampus

165
Q

how can an experience become part of memory?

A

experience must produce persistent structural and functional changes that represent the experience within the brain

166
Q

what is plasticity?

A

capability for change associated w/ learning

167
Q

what does plasticity involve?

A
  • changes in synaptic connections among neurons
  • changes in individual neurons: more presynaptic terminals, enlarged presynaptic end bulbs, more dendritic branches on postsynaptic neuron
168
Q

what reverses changes in individual neurons?

A

inactivity of neurons

169
Q

what are the two language areas in the cerebral cortex?

A
  • Wernicke’s area
  • Broca’s area
170
Q

what is Wernicke’s area?

A

association area in left cerebral hemisphere that interprets meaning of written AND spoken words

171
Q

what is Broca’s area?

A

motor area in left cerebral hemisphere that translates thoughts into speech

172
Q

how does Broca’s area turn thoughts into speech?

A

Broca’s area receives input from Wernicke’s area and develops motor plan → info sent to primary motor area → contraction of muscles required for speech

173
Q

When Joni first stepped onto the sailboat, she smelled the tangy sea air and felt the motion of water beneath her feet. After a few minutes, she no longer noticed the smell, but unfortunately she was aware of the rolling motion for hours.

What types of receptors are involved in smell and detection of motion? Why did her sensation of smell fade but the rolling sensation remain?

A

Chemoreceptors in the nose detect odors.

Proprioceptors detect body position and are involved in equilibrium.

The chemoreceptors in the nose are rapidly adapting, whereas proprioceptors are slowly adapting.

Thus the smell faded while the sensation of motion remained.

174
Q

Monique sticks her left hand into a hot tub heated to about 43°C (110°F) in order to decide if she wants to enter.

Trace the pathway involved in transmitting the sensation of heat from her left hand to the primary somatosensory cortex.

A

Thermal (heat) receptors in her left hand detect the stimulus. A nerve impulse is transmitted to the spinal cord through first-order neurons with cell bodies in posterior root ganglia. The impulses travel into the spinal cord, where the first-order neurons synapse with second-order neurons, whose cell bodies are located in the posterior gray horn of the spinal cord. The axons of the second-order neurons decussate to the right side in the spinal cord and then the impulses ascend through the lateral spinothalamic tract. The axons of the second-order neurons end in the ventral posterior nucleus of the right side of the thalamus, where they synapse with the third-order neurons. Axons of the third-order neurons transmit impulses to the specific primary somatosensory areas in the postcentral gyrus of the right parietal lobe.

175
Q

Marvin has had trouble sleeping. Last night his mother found him sleepwalking and gently led him back to his bed. When Marvin was awakened by his alarm clock the next day, he had no recollection of sleepwalking and, in fact, told his mother about the vivid dreams he had.

What specific stages of sleep did Marvin undergo during the night? What neurological mechanism awakened Marvin in the morning?

A

When Marvin settled down for the night, he passed through stages 1–3 of NREM sleep. Sleepwalking occurred when he was in stage 4 (slow-wave sleep). Because this is the deepest stage of sleep, his mother was able to return him to his bed without awakening him. Marvin then cycled through REM and NREM sleep. His dreaming occurred during the REM phases of sleep. The noise of the alarm clock provided the sensory stimulus that stimulated the reticular activating system. Activation of this system sends numerous nerve impulses to widespread areas of the cerebral cortex, both directly and via the thalamus. The result is the state of wakefulness.

176
Q

Which tracts carry information from proprioceptors in joints and muscles to the cerebellum?

A

The anterior and posterior spinocerebellar tracts carry information from proprioceptors in joints and muscles to the cerebellum.

177
Q

How is the rubrospinal tract different from the other tracts of the indirect motor pathways?

A

The rubrospinal tract helps promote voluntary contractions of the distal parts of the upper limbs, whereas the rest of the indirect motor pathways cause involuntary contractions of muscles in the body.

178
Q

The axons of the corticobulbar tract terminate in the motor nuclei of which cranial nerves?

A

The axons of the corticobulbar tract terminate in the motor nuclei of the following cranial nerves: oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), glossopharyngeal (IX), vagus (X), accessory (XI), and hypoglossal (XII).

179
Q

Which tract conveys nerve impulses that result in contractions of muscles in the distal parts of the limbs?

A

The lateral corticospinal tract conducts impulses that result in contractions of the muscles in the distal parts of the limbs.

180
Q

How do the functions of upper motor neurons from the cerebral cortex and from the brainstem differ?

A

Cerebral cortex upper motor neurons are essential for the execution of voluntary movements of the body. Brainstem upper motor neurons regulate muscle tone, control postural muscles, and help maintain balance and orientation of the head and body.

181
Q

How do the somatosensory and motor representations compare for the hand, and what does this difference imply?

A

The hand has a larger representation in the primary motor cortex than in the primary somatosensory cortex, which implies greater precision in the hand’s movement control than fine ability in its sensation.

182
Q

Which cranial nerve conveys impulses for most somatic sensations from the left side of the face into the pons?

A

The left trigeminal (V) nerve conveys nerve impulses for most somatic sensations from the left side of the face into the pons.

183
Q

What types of sensory deficits could be produced by damage to the right anterolateral tract?

A

Damage to the right spinothalamic tract could result in loss of pain, temperature, touch, and pressure sensations on the left side of the body.

184
Q

How is a muscle spindle activated?

A

Muscle spindles are activated when the central areas of the intrafusal fibers are stretched.

185
Q

Which visceral organ has the broadest area for referred pain?

A

The kidneys have the broadest area for referred pain.

186
Q

Which sensations can arise when free nerve endings are stimulated?

A

Pain, thermal sensations, tickle, and itch arise with activation of different free nerve endings.

187
Q

Which senses are served by receptors that are separate cells?

A

The special senses of vision, taste, hearing, and equilibrium are served by separate sensory cells.

A-BIOL 1191 LECTURE (12 decks)

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