Chapter 14

Question 1

Sensory receptor structure and function

Answer 1

Detect somatic sensory info
Specialized cell or dendrite of sensory neuron
Respond to environmental changes
Responsible for trandsduction: convert stimuli to into AP sent to CNS
1st order neuron: sensory neuron (PNS cell bodies)
2nd order interneuron (in nuclei of SC/brain stem)
3rd order interneurons (thalamus)

Question 2

Process of sensation

Answer 2

1. transduction: 1st order neuron converts stimulus to graded potential (if threshold reached, AP is formed)
2. Peripheral sensory receptor “linked” to cortical neuron
3. Cortical destination depends on stimulus location and nature
4. Different ascending tracts of axons in SC/brain carry specific stimulus type (filtered through thalamus)

Question 3

General senses (6)

Answer 3

temperature
pain
touch
pressure
vibration
proprioception

Question 4

special sense (5)

Answer 4

olfaction
vision
gustation
equilibrium
hearing

Question 5

receptor sensitivity

Answer 5

receptor detect specific stimuli, insensitive to others
simple: dendrites of sensory neurons (free nerve endings)
complex: eye’s protected visual receptors, hair cells

Question 6

receptive field

Answer 6

area monitored by single receptor cell
larger field = poorer ability to localize stimulus
ex: back surface vs fingertip

Question 7

how are sensory receptors classified?

Answer 7

location: exteroreceptor, interoreceptor, proprioceptor
activation stimulus: nociceptors (pain), thermoreceptors, mechanoreceptors, chemoreceptors
somatic vs. visceral

Question 8

Nociceptors

Answer 8

pain receptor
free nerve ending with large receptive fields
location: superficial skin, joint capsules in periosteum of bone, blood vessel walls
Type A and C fibers

Question 9

type A fibers

Answer 9

fast pain
myelinated fibers
reflex result

Question 10

type C fibers

Answer 10

slow pain
unmyelinated fibers
aware, but general idea of affected area

Question 11

thermoreceptors

Answer 11

temperasture sensor
free nerve endings in dermis, sk. muscle, liver, hypothalamus
cold receptors (superficial) > warm receptors (deep)
same pathway as nociceptors

Question 12

mechanoreceptors

Answer 12

distortion of plasma membrane (mechanically gated ion channels that open/close w/ stretch
Tactile: touch, pressure, vibration
Baroreceptor: pressure changes (blood vessel, digestive sys., urinary tract)
proprioceptors: position of joint/muscles

Question 13

chemoreceptors

Answer 13

chemical concentration changes
no conscious awareness: info sent to brain stem
central: respiratory system, brain (H+, CO2 in CSF)
peripheral: carotid bodies + aortic bodies (H+, CO2, O2 in blood)

Question 14

1st order neuron

Answer 14

unipolar neuron
sensory neuron delivers somatic sensory info to CNS
cell bodies located in DRG (spinal nerve) or cranial nerve ganglion (cranial nerve)

Question 15

2nd order neuron

Answer 15

interneuron
cell bodies in SC (dorsal horn) or brain stem
conduct to opposite side thalamus

Question 16

3rd order neuron

Answer 16

interneuron
cell bodies in thalamus
conduct impulses to same-side primary somatosensory cortex

Question 17

Somatic sensory ascending pathways

Answer 17

carry sensory info from skin and sk. muscles of body wall, head, neck, and limbs
Major pathways: posterior column, spinothalamic, spinocerebellar

Question 18

Posterior column pathway (medial lemniscus)

Answer 18

Carry sensation of localized “fine touch”, pressure, vibration, proprioception
Starts at peripheral receptor
Ends at primary somatosensory pathway

Question 19

Posterior column pathway neurons

Answer 19

1st: axons come into SC through dorsal root ganglia then ascend into posterior column
2nd: decussate in medulla oblongata and go to thalamus, synapses on opp side of 3rd order
3rd: in thalamus nuclei, filter arriving stimuli (nature/region)

Question 20

Spinothalamic pathway (anterolateral system)

Answer 20

Nerve impulses for poorly localized touch, pain, pressure, temp
Damage: phantom limb syndrome, interneurons activated when limb isn’t there

Question 21

Spinothalamic pathway neurons

Answer 21

1st: connect receptor to 2nd order in SC dorsal gray horn
2nd: cell bodies in posterior gray horn of SC decussate there, axons go to brainstem as spinathalamic tracts
3rd: cell bodies in thalamus, both tracts synapse in thalamus, sorted/sent to primary somatosensory cortex

Question 22

Visceral sensory pathway

Answer 22

Visceral sensory info collected by interoceptors
Inaccurate perception of sensory localization
Referred pain: pain is felt in location other than the stimulus
Visceral + somatic info from same segment runs together in same tract

Question 23

Spinocerebellar pathway

Answer 23

Posture, balance, coordination of skilled movement
Cerebellum receives proprioception info
Tracts enter cerebellum via cerebellar peduncles
Perjunke cells: last synaps in cerebellum
Doesn’t reach awareness

Question 24

Spinocerebellar pathway

Answer 24

1st: neurons synapse on 2nd order interneurons in SC dorsal gray horns
2nd: interneurons axons ascend via spinocerebellar tracts (anterior tracts decussate, posterior don’t)

Question 25

Upper motor neuron

Answer 25

Cell body located in cerebral cortex or a brainstem nucleus Synapses on lower motor neuron (inhibit/activate LMN) Carry impulses for movement

Question 26

Lower motor neuron

Answer 26

Cell body located in anterior horn or a brainstem nucleus Axons leave CNS through cranial or spinal nerves

Question 27

Motor/descending pathways (efferent)

Answer 27

Pyramidal tracts Extrapyramidal tracts

Question 28

Sensory and ascending pathways (afferent)

Answer 28

Dorsal column medial lemniscus system Spinocerebellar tracts Anterolateral system

Question 29

Corticospinal pathways (pyramidal system)

Answer 29

Control voluntary skeletal muscle movement Left cerebral cortex controls right side muscles Upper motor neurons originate in primary motor cortex Most UMNs decussate in brainstem 2 pyramidal tracts: lateral corticospinal tract, anterior corticospinal tract

Question 30

Lateral corticospinal tract

Answer 30

Individual digit movement, distal muscles (limbs) Tracts descend on opp side of SC + synapses on LMNs in ventral gray horns at correct SC segment LMN innervates motor unit through ventral root

Question 31

Anterior (ventral) corticospinal tract

Answer 31

Axial, Proximal muscle movement Decussates in anterior white commissure of SC

Question 32

Extrapyramidal system

Answer 32

Involuntary movement/reflexes, muscle tone, gross movements of neck, trunk, proximal limbs (posture/coordination) UMNs originate in brainstem Indirectly regulated by basal ganglia and cerebellum

Question 33

Basal nuclei

Answer 33

Indirectly regulate extrapyramidal system Innitiation and cessation of muscle activity/control Damage: Movement disorders (dyskinesia: parkinsons, huntingtons, CP)

Question 34

How does cerebellum influence movement?

Answer 34

Posture, Balance, Coordination Indirectly modulates extrapyramidal system Learning rapid, coordinated, skilled movement Compares actual movement to planned movement Adjust to fit plan Dysfunction: decreased muscle tone, intentional tremor

Question 35

Reflex inhibition

Answer 35

Counter excitation from spindles Generates normal reflex with certain speed/amplitude

Question 36

Muscle tone

Answer 36

Maintained by balance between spindle excitation and inhibition from descending tracts

Question 37

LMN lesion

Answer 37

Muscle permanently limp Less muscle tone Decreased reaction to thump on muscles Fasciculations (spontaneous twitches) Muscle atrophy/degeneration

Question 38

UMN lesion

Answer 38

No atrophy of twitch First increase in tone Hyper-reactive reflexes (lack of inhibition) Limbs resist passive stretch Positive babinski test

Question 39

Memory

Answer 39

Declarative: facts, data, events Procedural: learned motor behaviors, stored in brain stem, involve basal nuclei, cerebral cortex, and cerebellum

Question 40

Storage of memory

Answer 40

Working memory: few seconds Short term memory: info recalled immediately, contain small bits of info, primary memories Long term memory: secondary memories fade, tertiary last forever Memory consolidation: requires hippocampus, amygdala links memory to emotion

Question 41

Memory storage sites

Answer 41

Cerebral cortex: long term memory Visual association cortex: visual memory Premotor cortex: voluntary motor activity Temporal lobe: voices + words

Question 42

Cellular mechanisms of memory formation

Answer 42

Increased neurotrasmitter release: greater effect on postsynaptic neuron Facilitation at synapse: brings membrane closer to threshold Formation of additional synaptic connections: repeated communication, axons branch/form additional synapses on postsynaptic neuron

Question 43

Deep sleep

Answer 43

Slow wave Entire body relaxes Minimal cerebral cortex activity HR, BP, Respiratory rate, energy use decline 30%

Question 44

REM sleep

Answer 44

Dreaming Changes in BP and respiratory rate Muscle tone decreases Intense inhibition of somatic motor neurons

Question 45

Benefits of sleep

Answer 45

Increased protein synthesis in neurons Time for memory consolidation