Chapter 47- Sensory Receptors Flashcards

1
Q

Mechanoreceptors

A

detect compression or stretching of tissues

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2
Q

Thermoreceptors

A

detect changes in temperature

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3
Q

Nociceptors

A

pain receptors, detect damage occurring in tissues

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4
Q

Electromagnetic receptors

A

detect light in the retina

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5
Q

Chemoreceptors

A

detect taste, smell, oxygen level in arterial blood, osmolality of body fluids, carbon dioxide concentration, other chemical factors

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6
Q

Differential sensitivity of receptors.

A

they are sensitive to one type of stimuli and not others (rods and cones to light but not heat/cold, pain only receptive to pressure once it is enough to cause damage)

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7
Q

What is the “labeled line” principle?

A

each nerve tract terminates at a specific point in the central nervous system, and the type of sensation felt when a nerve fiber is stimulated is determined by the point in the nervous system to which the fiber leads

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8
Q

What is the receptor potential?

A

type of stimulus that excites the receptor, its immediate effect is to change the membrane electrical potential of the receptor

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9
Q

Mechanisms of receptor potentials.

A

1) mechanical deformation of the receptors (stretching of the receptor membrane and ion channels open) 2) application of chemical to the membrane (ion channels open) 3) change of temperature (alters the permeability of the membrane) 4) electromagnetic radiation (changes the receptor membrane characteristics and allows ions to flow through channels)

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10
Q

Maximum amplitude of most sensory receptors.

A

100 mV

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11
Q

The more the receptor potential rises above threshold level, the greater the frequency of what?

A

action potentials

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12
Q

What allows sensory receptors to have an extreme range of response, from very weak to very intense?

A

frequency of repetitive action potentials
transmitted from sensory receptors increases approx. in proportion to the increase in receptor
potential; very intense stimulation of the receptor causes progressively less and less additional increase in numbers of action potentials

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13
Q

What is adaptation of sensory receptors?

A

adapt either partially or completely to any constant
stimulus after a period of time; pacinian corpuscle
adapts extremely rapidly and hair receptors adapt
within a second or so, whereas some joint capsule and muscle spindle receptors adapt slowly

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14
Q

How do mechanoreceptors adapt?

A

receptor potential occurs at onset of compression; accommodation (inactivation of Na channels as fiber gradually accommodates stimulus)

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15
Q

What are tonic receptors?

A

slowly adapting receptors that can transmit signal as long as stimulus is present; examples are muscle spindles, Golgi tendons, pain, baroreceptors, chemoreceptors of carotid and aortic bodies

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16
Q

Rapidly adapting receptors are also called?

A

“Rate receptors”, “Movement receptors”, “Phasic receptors”

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17
Q

If you haven’t done so (because you are only reading the outlines), go to page 576 in the 11th edition and read the heading: Importance of the Rate Receptors—Their Predictive Function.

A

that’s pretty cool.

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18
Q

Spatial summation.

A

increasing signal strength by using a greater number of fibers

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19
Q

Temporal summation.

A

increasing the frequency of nerve impulses in each fiber

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20
Q

Type A nerve fibers

A

large and medium-sized myelinated fibers of spinal nerves (alpha, beta, delta, gamma)

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21
Q

Type C nerve fibers

A

small unmyelinated nerve fibers that conduct impulses at low velocities; constitute more that one half of the sensory fibers in most peripheral nerves as well as all the postganglionic autonomic fibers

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22
Q

Group Ia nerve fibers

A

Fibers from the annulospiral endings of muscle spindles, alpha A fibers

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23
Q

Group Ib nerve fibers

A

Fibers from the Golgi tendon organs, alpha A fibers

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24
Q

Group II nerve fibers

A

Fibers from most discrete cutaneous tactile receptors and from the flower-spray endings of the muscle spindles, beta and gamma A fibers

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25
Q

Group III nerve fibers

A

Fibers carrying temperature, crude touch, and pricking pain sensations; delta A fibers

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26
Q

Group IV nerve fibers

A

Unmyelinated fibers carrying pain, itch, temperature, and crude touch sensation; type C fibers

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27
Q

Two ways to increase sensation of pain?

A

spatial and temporal summation

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28
Q

Give an example of amplifying divergence?

A

type of divergence is characteristic of the corticospinal pathway, in control of skeletal muscles, with a single large pyramidal cell in the moto cortex capable, under highly facilitated conditions, of exciting as many as 10000 muscle fibers.

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29
Q

Give an example of divergence into multiple tracts?

A

information transmitted up the dorsal column of the spinal cord takes two courses in the lower part of the brain: into cerebellum, and through the lower regions of the brain to the thalamus and cerebral cortex.

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30
Q

The signals from the interneurons ______ on the anterior motor neurons to control muscle function.

A

converge

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31
Q

Give an example of reciprocal inhibition.

A

at the same time that an excitatory signal is transmitted by one of neurons in the spinal cord to cause forward movement of the leg, the antagonist muscle has to be inhibited

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32
Q

What is a reverberatory, or oscillatory,

circuit?

A

circuits are caused by positive feedback within the neuronal circuit that feeds back to re-excite the input of the same circuit. The circuit discharges over a long period of time.

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33
Q

Give an example of reverberating circuit in the body.

A

autonomic nervous system to control such functions as vascular tone, gut tone, degree of constriction of the iris in the eye, and heart rate

34
Q

What occurs during epileptic seizures?

A

uncontrolled reverberating signals due to the areas of the being interconnected directly or indirectly

35
Q

What are the two basic mechanisms that prevent reverberating signals in the brain?

A

inhibitory circuits and fatigue of synapses

36
Q

Two types of inhibitory circuits in widespread areas of the brain help prevent excessive spread of signals:

A

inhibitory feedback circuits and neuronal pools that exert gross inhibitory control over widespread areas of the brain

37
Q

What is synaptic fatigue?

A

synaptic transmission becomes progressively weaker the more prolonged and more intense the period of excitation.

38
Q

As the receptor potential rises higher above a threshold, what happens to the new frequency of action potentials?

A

It Increases

39
Q

Which type of sensory fibers are signals from warm receptors mainly transmitted along?

A

slow conducting type C fibers

40
Q

Which region of the pain supression pathway do neurons use serotonin as a neurtransmitter?

A

Nucleus Raphes Magnus

41
Q

In chemical synapses that involve a so-calledd 2nd messenger, typically a G-protein linked to the post-synapic receptor is activated when the neurotransmitter binds to that receptor. What is an activity performed by the activated 2nd messenger?

A

Activation of cAMP or cGMP

42
Q

True or False: Dendrites can propagate action potentials.

A

False: Dendrites cannot initiate or conduct action potentials, but they can transmit electrical potentials by electronic conduction.

43
Q

An expanded tip tactile receptor found in the dermis of hairy skin that is specialized to detect continuously applied touch sensation

A

Merkel’s Disc

44
Q

This group of neurons in the brain’s endogenous pain suppression system has cell bodies located in a portion of the midbrain.

A

The Periaqueductal Gray

45
Q

True or False: Visceral pain fibers can provide input to anterolateral tract cells that also recive somatic pain signals from the skin surface. The convergent input of the two types of pain signals to a common set of spinal cord neurons is thought to be the basis for referred pain.

A

True

46
Q

Inhibition of pain signals by tactile stimulation of a skin surface involves which type of pain fibers?

A

Type Aβ (beta) fibers in peripheral nerves

47
Q

True or False: The size of the representaion of various body parts in the primary somatosensory cortex is correlated with the density of specialized peripheral receptors (aka cutaneous receptors) in that body part.

A

True

48
Q

Pain receptors in the skin are classified as this:

A

Free Nerve Endings

49
Q

Vibratory sensation is dependent on the detection of reapidly changing, repetitive sensations. The high frequency end of the repetitive stimulation scale is detected by which type of receptors?

A

Pacinian Corpuscles sense hihg-frequency repetitive stimulation (indentation or pressure) of the skin.

50
Q

This system conveys information concerning highly localized touch sensations and body position (proprioceptive) sensations.

A

Dorsal colum-medial lemniscal system

51
Q

Once initiate, the action potential is described as what type of process?

A

It is an “all or none” process, so once intiated, the action potential runs its course to completion.

52
Q

Yes or NO: Does brain tissue have pain receptors?

A

No, the brain itself lack pain receptors and is therefore insensitive to pain. Stretching of the dura, tugging on the venous sinuses and stimulation to the blood vessels of the meninges however causes intense pain.

53
Q

Where are first-order (primary afferent)neuronal cell bodies of the dorsal column-medial lemniscal system found?

A

Dorsal Root Ganglia

54
Q

True or False: An important functional parameter of Pain receptors is that they exhibit little or no adaptation.

A

True

55
Q

The gray matter of the primary somatosensory cortex contains six layers of cells. Which layer receives the bulk of incoming signals from the somatosensory nuclei of the thalmus?

A

Layer IV

56
Q

Proprioceptive sensation involves muscle spindles and ________?

A

both Tactile and Joint capsule receptors.

57
Q

This structure carries axons from neurons in the ventral posterolateral nucleus of the thalmus to the primary somatosensory cortex.

A

The Internal Capsule

58
Q

This disorder causes sever, stabbing pain to one side of the face as it occurs over the sensory distribution of cranial nerves V & IX. Treatment includes severing cranial nerve V just inside the cranium where the sensory and motor functions separate.

A

Tic Douloureux

59
Q

A transmitter agent used by the slow pain fibers that is released slowly over a period of seconds or minutes at synapses in the dorsal horn.

A

Substance P

60
Q

Is the range of stimulus intensity detected by the somatosensory sytem less, more or equivalent to that of other sensory systems such as vision & audition?

A

Equivalent

61
Q

Which pain fibers are responsible for the localization of a pain stimulus?

A

Type Aδ (delta) fibers, NOT Type C fibers.

62
Q

This substance enhances the sensitivity of pain receptors but does not directly excite them.

A

Prostaglandins

63
Q

This disorder is characterized by the loss of pain sensation throughout one entire side of the body and opposite side of the face.

A

Lateral Medullary syndrome

64
Q

Which structure carries axons from the nucleus gracilis to the thalmus?

A

Medial Lemniscus

65
Q

This disorder is characterized by excessive pain in a skin dermatomal distribution resulting from a viral infection of a dorsal root ganglion.

A

Herpes Zoster

66
Q

Which body parts is represented superiorly and medially within the postcentral gyrus?

A

The Lower Limb

67
Q

What is the Brodmann number designation for the primary somatosensory cortex?

A

3,1,2

68
Q

A non-encapsulated receptor found in the epidermis of the skin throughout the body as well as in the cornea, where it signals touch, pressure and pain sensations

A

Free Nerve Endings

69
Q

The concept of specificity in sensory nerve fibers that transmit only one modality of sensation.

A

Labeled Line Principle

70
Q

An elongated, encapsulated receptor found in the dermal pegs of blabrous skin, especially abundant on the lips & finger tips.

A

Meissner’s Corpuscle

71
Q

An encapsulated receptor found deep in the skin throughout the body as well as in facial layers, where it detects indentation of the skin (pressure) and movement across the surface (vibration)

A

Pacinian Corpuscle

72
Q

True or False: In spatial summation, incresing signal strength is transmitted by using greater numbers of sensory fibers.

A

True

73
Q

After a pain stimulus is applied, how long does it take for fast pain to be felt?

A

About 0.1 seconds

74
Q

This disorder involves a loss of pain sensation on one side of the body coupled with loss of proprioception, precise tactile localization and vibratory sensations on the contralateral side of the body.

A

Brown-Sequard syndrome

75
Q

This neurotransmitter typically evokes inhibitory responses.

A

Glycine

76
Q

This neurotransmitter is associated with the locus ceruleus

A

Norepinephrine

77
Q

Which transmitter agent is used by the fast pain fibers at their synapses in the dorsal horn?

A

Glutamate

78
Q

What is thought to be the cause of prodromal sysmptoms of migrane headaches such as nausea, loss of vision, visual aura or other sensory hallucinations?

A

Vasospasm & eventually ischemia in a sensory area of cortex are thought to be the basis for the prodromal symptoms associated with migranes.

79
Q

Glutamate

A

transmitter agent used by the fast pain fibers at their synapses in the dorsal horn

80
Q

Norepinephrine

A

This neurotransmitter is associated with the locus ceruleus

81
Q

An interneuron in this region uses enkephalin to inhibit pain transmission.

A

Dorsal Horn of the spinal cord