lecture 4,5 & 6 General Sensory Mechanisms

Question 1

what do type of endings do mechanoreceptors include

Answer 1

both free and encapsulated endings receiving tactile sensibilities

Question 2

what are included in expanded tip endings of mechanoreceptors

Answer 2

merkel’s discs

Question 3

what are included in encapsulated endings of mechanoreceptors

Answer 3

meissner’s corpuscles
kraus’ corpuscles
pacinian corpuscles

Question 4

what is an example of a spray endings in mechanoreceptors

Answer 4

ruffini’s corpuscles

Question 5

what are mechanoreceptors involved in

Answer 5

hearing: sound receptors of cochlea
equilibrium: vestibular receptors
arterial pressure: baroreceptors

Question 6

define nocireceptors

Answer 6

free nerve endings responding to pain

Question 7

define electromagnetic receptors

Answer 7

include rods and cones of the eye for vision

Question 8

what do chemoreceptors sense

Answer 8

taste, smell, arterial oxygen, osmolarity, blood CO2, blood glucose, amino acids, and fatty acids

Question 9

define differential sensitivity

Answer 9

each type of receptor is highly sensitive to one type of stimulus and is almost non responsive to other types

Question 10

define modality

Answer 10

each of the principal types of sensation

Question 11

define labeled line principle

Answer 11

specificity of nerve fibers for transmitting only one modality of sensation

Question 12

what are the 4 mechanisms of stimulation for receptors

Answer 12

mechanical deformation,
application of a chemical,
temperature change,
electromagnetic radiation

Question 13

what are characteristics of tonic receptors

Answer 13

slow adapting,
detect continuous stimulus strength,
transmit impulses as long as stimulus is present

Question 14

what are types of tonic receptors

Answer 14

muscle spindles, golgi tendon organs, macula and vestibular receptors, baroreceptors, chemoreceptors

Question 15

what are characteristics of phasic receptors

Answer 15

rapidly adapting,
do NOT transmit a continuous signal,
stimulated only when stimulus strength changes,
transmit information regarding rate of change

Question 16

describe type A nerve fibers

Answer 16

large and medium sized myelinated fibers of spinal nerves

Question 17

describe type C nerve fibers

Answer 17

small, unmyelinated fibers,
conduct signals at low velocity,
make up more than half of all sensory fibers in most peripheral nerves and all postganglionic autonomic fibers

Question 18

what type of nerve fibers are in all postganglionic autonomic fibers

Answer 18

type C

Question 19

describe group 1a nerve fibers

Answer 19

fibers from annulospiral endings of muscle spindles

Question 20

describe group 1b nerve fibers

Answer 20

fibers from golgi tendon organs

Question 21

describe group II nerve fibers

Answer 21

from cutaneous tactile receptors and flower-spray

Question 22

describe group III nerve fibers

Answer 22

carry temperature, crude touch and pricking pain

Question 23

describe group IV nerve fibers

Answer 23

carry pain, itch, temperature and crude touch

Question 24

what group of nerve fibers is not Type A

Answer 24

group IV

Question 25

define receptor field

Answer 25

in spatial summation, the entire cluster of nerve endings from one pain fiber covers this area of skin

Question 26

define stimulatory field of neuronal pool

Answer 26

neuronal area within the pool stimulated by each incoming nerve fibers

Question 27

where do the terminals of the stimulatory field of a neuronal pool lie

Answer 27

lie on the nearest neuron it its field

Question 28

define discharge zone of neuronal pool

Answer 28

includes all the output fibers stimulated by the incoming fiber

Question 29

describe diverging neuronal pathways

Answer 29

* may result in amplification of initial signal | * may allow transmission of original signal to separate areas

Question 30

describe converging neuronal pathways

Answer 30

* multiple input fibers converge onto a single output neuron | * input fibers may be from a single source or from multiple separate sources

Question 31

what are reverberatory circuits caused by

Answer 31

positive feedback within neuron circuit

Question 32

define reverberatory circuits

Answer 32

also called oscillatory circuits: a circuit once stimulated that may discharge repetitively for a long time

Question 33

define somatic senses

Answer 33

collect sensory info from all over the body

Question 34

what are the types of somatic senses

Answer 34

mechanoreceptive, thermoreceptive, pain

Question 35

define special senses

Answer 35

vision, hearing, smell, taste, and equilibrium

Question 36

where do exteroreceptive sensations come from

Answer 36

from the surface of the body

Question 37

what does proprioceptive sensations refer to

Answer 37

physical state of the body: position sensations, muscle and tendon sensations, pressure sensations, equilibrium

Question 38

define deep sensations

Answer 38

deep pressure, pain and vibrations

Question 39

define mechanoreceptive somatic senses

Answer 39

include both tactile and position senses that are stimulated by mechanical displacement of some tissue of the body

Question 40

describe primary sensory neurons

Answer 40

from external receptors, travel through dorsal roots of spinal cord, synapse with secondary neurons

Question 41

describe secondary neurons

Answer 41

make up tracts in spinal cord and brainstem, usually terminate in thalamus, synapse with tertiary neurons

Question 42

describe tertiary neurons

Answer 42

from thalamus to primary sensory cortex, | travel through internal capsule

Question 43

what ascending pathways are for conscious perception

Answer 43

spinothalamic and medial lemniscal

Question 44

what ascending pathways are for unconscious perception

Answer 44

spinocerebellar, spino-olivary, spinotectal, spinoreticular

Question 45

what do lateral spinothalamic tracts carry

Answer 45

pain and temperature

Question 46

where doe primary fibers of lateral spinothalamic tract ascend/descend

Answer 46

1-2 spinal cord segments before synapses with secondary fibers

Question 47

where do the secondary axons of the lateral spinothalamic tract decussate

Answer 47

through anterior gray and white commissures

Question 48

what do the secondary fiber collateral that project to reticular formation (lateral spinothalamic tract) stimulate

Answer 48

wakefulness and consciousness

Question 49

what do tertiary fibers of the lateral spinothalamic tract form

Answer 49

part of internal capsule

Question 50

what sensations does the anterior spinothalamic tract carry

Answer 50

light touch (crude touch), pressure, tickle, itch

Question 51

where do the primary neurons of the anterior spinothalamic tract ascend

Answer 51

8-10 spinal cord segments before synapses with secondary neurons

Question 52

where do tertiary fibers of the anterior spinothalamic tract ascend

Answer 52

through internal capsule to primary sensory cortex

Question 53

what sensations does the medial lemniscus system carry

Answer 53

for 2 point sensation (fine touch), pressure and vibration

Question 54

where do the primary fibers synapse with secondary neurons in the medial meniscus system

Answer 54

medulla

Question 55

where do fibers of fasciculus gracilis synapse in

Answer 55

nucleus gracilis

Question 56

what do the fibers of fasciculus gracilis synapse in nucleus gracilis convey (medial lemniscus system)

Answer 56

convey sensations from below mid thoracic level

Question 57

what do the fibers of fasciculus cuneatus synapse in nucleus cuneatus convey

Answer 57

sensations from above mid thoracic level; also conveys proprioceptive sensations from arms to cerebellum

Question 58

what is the primary somatosensory area made up of

Answer 58

Brodmann's areas 1, 2, and 3

Question 59

what is the somatosensory association area made up of

Answer 59

Brodmann's areas 5 and 7

Question 60

where does somatosensory area 2 receive signals from

Answer 60

brain stem, transmitted upward from both sides of the body, secondarily from somatosensory area 1, and other sensory areas of the body (including visual and auditory)

Question 61

what do layers 1 and 2 of the somatosensory cortex do

Answer 61

receive input signals from lower brain centers

Question 62

what do layers 2 and 3 of the somatosensory cortex do

Answer 62

send info through corpus callosum to opposite hemisphere

Question 63

what do layers 5 and 6 of the somatosensory cortex do

Answer 63

large neurons in layer 5 project to distant areas (basal nuclei, brain stem, spinal cord) and axons from layer 6 project to thalamus

Question 64

where do primary sensory neurons originate

Answer 64

from peripheral receptors

Question 65

how do primary sensory neurons enter the spinal cord

Answer 65

via dorsal roots of spinal (cranial) nerves

Question 66

where do primary sensory neurons synapse with secondary neurons

Answer 66

spinal cord

Question 67

where do secondary sensory neurons synapse with tertiary sensory neurons

Answer 67

thalamus

Question 68

why is lateral inhibition important for 2 point discrimination touch

Answer 68

important in blocking the lateral spread of excitatory signals, thereby increasing the degree of contrast in the cerebral cortex

Question 69

where does lateral inhibition occur

Answer 69

(at each synaptic level): dorsal column nuclei, ventrobasal nuclei of thalamus, somatosensory cortex

Question 70

where do axons from the lower limbs travel (for dorsal column-medial lemniscal pathway)

Answer 70

travel in the medial portions of the 2 dorsal columns in areas called fasciculus gracilis

Question 71

where do the axons from the upper limbs travel (for dorsal column-medial lemniscal pathway)

Answer 71

in the lateral portions of the 2 dorsal columns (each of these areas is called fasciculus cuneatus)

Question 72

where do the axons in the fasciculus gracilis synapse in the lower medulla?

Answer 72

nucleus gracilis

Question 73

where do the axons in the fasciculus cuneatus synapse in the lower medulla?

Answer 73

nucleus cuneatus

Question 74

what paired tracts do the secondary neurons travel through the brain stem as in the dorsal column-medial lemniscal pathway

Answer 74

medial lemniscus

Question 75

what type of fibers typically carry fast pain

Answer 75

type A delta

Question 76

where do pain fibers of fast pain typically terminate

Answer 76

lamina A (lamina marginalis) of the dorsal horns of the spinal cord

Question 77

where do the pain fibers of slow pain typically terminate

Answer 77

layers 2 and 3 (substantial gelatinosa) of the dorsal horns of the spinal cord

Question 78

what type of fibers is slow chronic pain typically carried on

Answer 78

C type fibers

Question 79

what tract do the fast pain fibers make up

Answer 79

neospinaothalamic tracts

Question 80

what tract do the slow pain fibers make up

Answer 80

paleospinothalamic

Question 81

what neurotransmitter do fast pain fibers (type A-dalta) use

Answer 81

glutamate

Question 82

what neurotransmitter do type C fibers use

Answer 82

glutamate and substance P

Question 83

when does brown-sequard syndrome occur

Answer 83

when there is a hemisection of the spinal cord

Question 84

what are the 3 components of the analgesia system

Answer 84

* periaquaductal gray and periventricular regions of the brainstem and 3rd ventricle * raphe magnus nucleus and reticular nuclei in medulla * pain inhibitory complex in dorsal horns of spinal cords

Question 85

what are the 3 types of receptors that discriminate thermal gradation

Answer 85

cold, warmth, pain

Question 86

describe warmth nerve endings

Answer 86

free nerve endings and mainly transmitted over C-type fibers

Question 87

describe cold receptors

Answer 87

* 3-10 times as numerous as warm nerve receptors; | * small type A-delta myelinated endings

Question 88

when does referred pain occur

Answer 88

when visceral pain fibers are stimulated and stimulate some of the pain fibers that conduct pain signals from the skin

Question 89

how is all visceral pain from the thoracic and abdominal cavities tranmissted

Answer 89

via type C pain fibers

Question 90

what are headaches the result of

Answer 90

pain referred to the surface of the head from deep head structures