lecture 4,5 & 6 General Sensory Mechanisms Flashcards Preview

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Flashcards in lecture 4,5 & 6 General Sensory Mechanisms Deck (90):
1

what do type of endings do mechanoreceptors include

both free and encapsulated endings receiving tactile sensibilities

2

what are included in expanded tip endings of mechanoreceptors

merkel's discs

3

what are included in encapsulated endings of mechanoreceptors

meissner's corpuscles
kraus' corpuscles
pacinian corpuscles

4

what is an example of a spray endings in mechanoreceptors

ruffini's corpuscles

5

what are mechanoreceptors involved in

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

6

define nocireceptors

free nerve endings responding to pain

7

define electromagnetic receptors

include rods and cones of the eye for vision

8

what do chemoreceptors sense

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

9

define differential sensitivity

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

10

define modality

each of the principal types of sensation

11

define labeled line principle

specificity of nerve fibers for transmitting only one modality of sensation

12

what are the 4 mechanisms of stimulation for receptors

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

13

what are characteristics of tonic receptors

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

14

what are types of tonic receptors

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

15

what are characteristics of phasic receptors

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

16

describe type A nerve fibers

large and medium sized myelinated fibers of spinal nerves

17

describe type C nerve fibers

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

18

what type of nerve fibers are in all postganglionic autonomic fibers

type C

19

describe group 1a nerve fibers

fibers from annulospiral endings of muscle spindles

20

describe group 1b nerve fibers

fibers from golgi tendon organs

21

describe group II nerve fibers

from cutaneous tactile receptors and flower-spray

22

describe group III nerve fibers

carry temperature, crude touch and pricking pain

23

describe group IV nerve fibers

carry pain, itch, temperature and crude touch

24

what group of nerve fibers is not Type A

group IV

25

define receptor field

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

26

define stimulatory field of neuronal pool

neuronal area within the pool stimulated by each incoming nerve fibers

27

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

lie on the nearest neuron it its field

28

define discharge zone of neuronal pool

includes all the output fibers stimulated by the incoming fiber

29

describe diverging neuronal pathways

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

30

describe converging neuronal pathways

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

31

what are reverberatory circuits caused by

positive feedback within neuron circuit

32

define reverberatory circuits

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

33

define somatic senses

collect sensory info from all over the body

34

what are the types of somatic senses

mechanoreceptive, thermoreceptive, pain

35

define special senses

vision, hearing, smell, taste, and equilibrium

36

where do exteroreceptive sensations come from

from the surface of the body

37

what does proprioceptive sensations refer to

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

38

define deep sensations

deep pressure, pain and vibrations

39

define mechanoreceptive somatic senses

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

40

describe primary sensory neurons

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

41

describe secondary neurons

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

42

describe tertiary neurons

from thalamus to primary sensory cortex,
travel through internal capsule

43

what ascending pathways are for conscious perception

spinothalamic and medial lemniscal

44

what ascending pathways are for unconscious perception

spinocerebellar,
spino-olivary,
spinotectal,
spinoreticular

45

what do lateral spinothalamic tracts carry

pain and temperature

46

where doe primary fibers of lateral spinothalamic tract ascend/descend

1-2 spinal cord segments before synapses with secondary fibers

47

where do the secondary axons of the lateral spinothalamic tract decussate

through anterior gray and white commissures

48

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

wakefulness and consciousness

49

what do tertiary fibers of the lateral spinothalamic tract form

part of internal capsule

50

what sensations does the anterior spinothalamic tract carry

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

51

where do the primary neurons of the anterior spinothalamic tract ascend

8-10 spinal cord segments before synapses with secondary neurons

52

where do tertiary fibers of the anterior spinothalamic tract ascend

through internal capsule to primary sensory cortex

53

what sensations does the medial lemniscus system carry

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

54

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

medulla

55

where do fibers of fasciculus gracilis synapse in

nucleus gracilis

56

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

convey sensations from below mid thoracic level

57

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

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

58

what is the primary somatosensory area made up of

Brodmann's areas 1, 2, and 3

59

what is the somatosensory association area made up of

Brodmann's areas 5 and 7

60

where does somatosensory area 2 receive signals from

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)

61

what do layers 1 and 2 of the somatosensory cortex do

receive input signals from lower brain centers

62

what do layers 2 and 3 of the somatosensory cortex do

send info through corpus callosum to opposite hemisphere

63

what do layers 5 and 6 of the somatosensory cortex do

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

64

where do primary sensory neurons originate

from peripheral receptors

65

how do primary sensory neurons enter the spinal cord

via dorsal roots of spinal (cranial) nerves

66

where do primary sensory neurons synapse with secondary neurons

spinal cord

67

where do secondary sensory neurons synapse with tertiary sensory neurons

thalamus

68

why is lateral inhibition important for 2 point discrimination touch

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

69

where does lateral inhibition occur

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

70

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

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

71

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

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

72

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

nucleus gracilis

73

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

nucleus cuneatus

74

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

medial lemniscus

75

what type of fibers typically carry fast pain

type A delta

76

where do pain fibers of fast pain typically terminate

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

77

where do the pain fibers of slow pain typically terminate

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

78

what type of fibers is slow chronic pain typically carried on

C type fibers

79

what tract do the fast pain fibers make up

neospinaothalamic tracts

80

what tract do the slow pain fibers make up

paleospinothalamic

81

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

glutamate

82

what neurotransmitter do type C fibers use

glutamate and substance P

83

when does brown-sequard syndrome occur

when there is a hemisection of the spinal cord

84

what are the 3 components of the analgesia system

*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

85

what are the 3 types of receptors that discriminate thermal gradation

cold, warmth, pain

86

describe warmth nerve endings

free nerve endings and mainly transmitted over C-type fibers

87

describe cold receptors

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

88

when does referred pain occur

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

89

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

via type C pain fibers

90

what are headaches the result of

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