SDL-7 Sensory Receptors

Question 1

It takes an average of _____ms to appreciate and react to an incoming stimulus.

Answer 1

0.250ms

Question 2

_______________ are receptors that respond to stimuli arising from outside the body. May be divided into two subgroups:
I. Telereceptors
II. Contact receptors

Answer 2

Exteroreceptors

Question 3

______________ are receptors that detect signals originating some distance from the receptor (e.g. light detected by the eye, sound by the ear, and chemicals by the nose).

Answer 3

Telereceptors

Question 4

_____________ are receptors that detect signals impinging on the external skin such as touch, pressure, heat, and cold.

Answer 4

Contact receptors

Question 5

_____________ are receptors that are sensitive to signals from within the body, such as viscera, blood vessels, etc.

Answer 5

Interoreceptors

Question 6

_____________ are receptors that detect signals from somatic structures which contribute to our sense of orientation and movement of the body in space (e.g. angle of limbs).

Answer 6

Proprioceptors

Question 7

A specific modality of stimulus that a receptor is highly sensitive to is referred to as the ______________.

Answer 7

Adequate stimulus or specific energy

Question 8

The theory that receptors are highly sensitive to one specific modality of stimulus is known as the ____________ theory.

Answer 8

Specific nerve energy

Question 9

The ___________ theory states that sensation results from differing patterns of action potentials produced in a single sensory fiber.

Answer 9

Pattern

Question 10

The intensity of a stimulus is coded in a single nerve fiber by the (amplitude/frequency) of action potentials.

Answer 10

Frequency

Question 11

Most neurons are spontaneously active even when an action potential is not present. This rate of spontaneous activity represents a set point and is referred to as ______________.

Answer 11

Background frequency

Question 12

As the strength of a stimulus increases, receptors with (higher/lower) thresholds are recruited to the synapse.

Answer 12

Higher

Question 13

The absolute intensity of a stimulus involves the _______________________ and ___________________________.

Answer 13

I. Firing frequency of receptor nerve fibers

II. Number of receptor fibers carrying the signal

Question 14

The initial signal that depolarizes a membrane is the ______________.

Answer 14

Generator potential

Question 15

TRP receptors are non-specific, but the inward driving force for (Na+/K+/Cl-) is greater than the others, resulting in membrane depolarization.

Answer 15

Na+

Question 16

_____________ is either a decrease or complete cessation of response of a receptor to a continuing or repeated stimulus.

Answer 16

Adaptation

Question 17

Receptors capable of completely adapting to a stimulus are (phasic/tonic) receptors.

Answer 17

Phasic

Question 18

Receptors that continue their activity as long as the stimulus is present are (phasic/tonic) receptors.

Answer 18

Tonic

Question 19

____________ refers to a decrease in reflex action or to a decrease in awareness of a continuing or repeated stimulus due to decreased responsiveness of central neurons.

Answer 19

Habituation

Question 20

(T/F) Habituation involves changing the strength of associated synapses which results in altered afferent input.

Answer 20

True

Question 21

The ____________ of a single neuron is the area of body from which stimulation influences the neuron’s discharge rate.

Answer 21

Receptive field

Question 22

How is the two point discrimination test conducted?

Answer 22

Two point discrimination is done by touching the skin with one or two points and asking the subject to tell how many points were used. When the two points are less than a threshold distance apart, the subject will report feeling one point.

Question 23

What is an example of the wide variety of two point discrimination thresholds in the body?

Answer 23

Two point discrimination threshold distance is about 1mm on the fingers, compared to about 40mm on the back.

Question 24

The cell body of each primary somatosensory neuron is located in a (dorsal root/ventral root) ganglion of the ______________.

Answer 24

Dorsal root ganglion of the spinal cord

Question 25

Primary somatosensory neurons are (unipolar/bipolar/pseudounipolar).

Answer 25

Pseudounipolar

Question 26

Mechanoreceptors are exteroreceptors that detect the ___________ and/or ____________ of the skin by mechanical stimuli.

Answer 26

Displacement and/or velocity (rate of displacement) of skin

Question 27

Nociceptors are exteroreceptors that detect ____________ stimuli.

Answer 27

Painful

Question 28

Mechanoreceptors have afferent fibers in the ____ range.

Answer 28

Aβ (group II)

Question 29

Aα(Ia) fibers are sensitive to ___________ and ___________.

Answer 29

I. Limb position | II. Motion

Question 30

Aβ(II) fibers are sensitive to _________, _________, and _________.

Answer 30

I. Tactile II. Pressure III. Vibration

Question 31

Aδ(III) fibers are sensitive to ____________ and __________.

Answer 31

I. Fast pain | II. Cold

Question 32

C(IV) fibers are sensitive to _____________ and __________.

Answer 32

I. Slow pain | II. Warmth

Question 33

Nociceptors have fibers in the ____ and ____ range.

Answer 33

Aδ | C

Question 34

(T/F) Mechanoreceptors are only present in glabrous skin.

Answer 34

False. Mechanoreceptors are present in both hairy and glabrous skin.

Question 35

Merkel's disks and Ruffini's endings are examples of (nociceptors/thermoreceptors/mechanoreceptors).

Answer 35

Mechanoreceptors

Question 36

_____________ are slowly adapting mechanoreceptors that respond to small displacements of the skin.

Answer 36

Ruffini's endings

Question 37

____________ are mechanoreceptors that respond to indentation of the skin directly over their receptor.

Answer 37

Merkel's disks

Question 38

In hairy skin, _________ and _________ detect velocity of displacement in skin.

Answer 38

I. Hair follicle endings | II. C-mechanoreceptors

Question 39

In glabrous skin, ____________ detect velocity of displacement of skin.

Answer 39

Meissner's corpuscles

Question 40

Meissner's corpuscles detect (low/high) frequency vibrations, typically between __-__ Hz.

Answer 40

Low frequency vibrations; 5-40Hz

Question 41

A ____________ is a mechanoreceptor that detects primarily vibration of higher frequencies, between ranges of __-__Hz.

Answer 41

Pacinian corpuscle; 60-400Hz

Question 42

The most sensitive of the tactile mechanoreceptors is (Merkel's disk/Pacinian corpuscle/Ruffini's endings).

Answer 42

Merkel's disk

Question 43

Most unmyelinated nociceptors respond to mechanical, thermal, and chemical stimuli. Since they respond to multiple stimuli, they are referred to as ___________ receptors.

Answer 43

Polymodal

Question 44

(Aching/Burning/Pricking) pain is quickly felt, transmitted by Aδ fibers, can be accurately localized, and subsides quickly.

Answer 44

Pricking pain

Question 45

(Aching/Burning/Pricking) pain arises from deeper tissues and is often difficult to localize.

Answer 45

Aching pain

Question 46

(Aching/Burning/Pricking) pain is slow in onset, transmitted by C fibers, less able to be precisely localized, and can persist for many seconds after removal of the stimulus.

Answer 46

Burning pain

Question 47

(T/F) Pricking pain is often more difficult to endure than the other types of pain, evoking reflex increases in heart rate and respiration.

Answer 47

False. Burning pain is more difficult to endure and responsible for these effects.

Question 48

A skin injury is often followed by the triple response which entails:

Answer 48

I. Local reddening II. Red flare III. Formation of a wheal on the skin

Question 49

(T/F) The nerve fibers for both warm and cold sensation are myelinated.

Answer 49

False. The nerve fibers for cold sensation consist of myelinated and unmyelinated fibers, while the fibers for warm sensation are not.

Question 50

Visceral receptors primarily respond to:

Answer 50

I. Stretch II. Noxious stimuli III. Vibration

Question 51

Muscle stretch receptor organs (muscle spindles) contain modified skeletal muscle fibers known as _________________.

Answer 51

Intrafusal muscle fibers

Question 52

Intrafusal muscle fibers are innervated near both ends by (alpha/beta/gamma) motoneurons, while extrafusal muscle fibers are innervated by (alpha/beta/gamma) motoneurons only at the midpoint of the fibers.

Answer 52

Intrafusal - Gamma motoneurons | Extrafusal - Alpha motoneurons

Question 53

________________ are the larger intrafusal muscle fibers in which cell nuclei are concentrated in a central region.

Answer 53

Nuclear bag fibers

Question 54

________________ are the smaller intrafusal muscle fibers in which cell nuclei are arranged in a chain.

Answer 54

Nuclear chain fibers

Question 55

Intrafusal fibers have two types of sensory nerve endings: _____ and _____.

Answer 55

Ia and II

Question 56

In intrafusal muscle fibers, there is(are) typically (one/two/three/many) type Ia fiber(s) per spindle.

Answer 56

One

Question 57

In the muscle, intrafusal fusal fibers are arranged (in parallel/perpendicular) to extrafusal muscle fibers.

Answer 57

In parallel to

Question 58

When a muscle contracts and shortens, tension on the intrafusal muscle fibers is reduced and firing decreases. How is optimal tension maintained in this situation?

Answer 58

When tension on intrafusal muscle fibers is decreased due to muscle contraction, gamma motor neurons that are linked with alpha motor neurons activate the intrafusal muscle fibers and cause them to shorten in proportion with the length of the contracted muscle.

Question 59

(T/F) The sense of limb position is most likely signaled by only cutaneous receptors in the skin.

Answer 59

False. The best information is that limb position is signaled by a combination of skin, muscle, and joint receptors.

Question 60

Local anesthetics, such as procaine, block __ fibers first in the transmission of an action potential.

Answer 60

C fibers

Question 61

Hypoxia or pressure block __________ fibers first in the transmission of an action potential.

Answer 61

Large diameter fibers (A type fibers)