11.4

Question 1

What parts of the body have more sensory receptors?

Answer 1

Areas that are highly sensitive to touch (e.g. hands, feet, lips, tongue)

Question 2

What is glabrous skin?

Answer 2

Skin that does not have hair follicles but contains larger numbers of sensory receptors than do hairy skin areas (e.g. lips, tongue, palm of hands, feet)

Question 3

What is nociception?

Answer 3

The perception of pain, temperature, or itch (mostly free nerve endings on nociceptors)

Question 4

How do nociceptors send information about pain, temp, or itch

Answer 4

By secreting chemicals that stimulate the nerve to produce an action potential

Question 5

What is hapsis?

Answer 5

The perception of fine touch and pressure; the ability to identify objects by touch

Question 6

How are haptic receptors activated?

Answer 6

Mechanical stimulation of body hair or capsule of tissue the dendrite is encased in

Question 7

What is proprioception?

Answer 7

The perception of the location and movement of the body; body awareness

Question 8

What are the encapsulated nerve endings are proprioceptors sensitive to?

Answer 8

The stretch of muscles and tendons and the movement of joints

Question 9

What are rapidly adapting receptors?

Answer 9

Body sensory receptors that respond briefly to the onset of a stimulus on the body; they activate neurons when stimulation begins and ends

Question 10

What kinds of sensory receptors have rapidly adapting receptors?

Answer 10

Haptic receptors and Proprioceptors

Question 11

What are slowly adapting receptors?

Answer 11

Body sensory receptors that respond as long as a sensory stimulus is on the body; detect whether a stimulus is still occurring

Question 12

What kinds of sensory receptors have slowly adapting receptors?

Answer 12

Nociceptors and Haptic receptors

Question 13

What is a posterior root ganglion neuron (PRG)?

Answer 13

A neuron that carries sensory information into the CNS; their dendrite and axon are continuous and the cell body is off to the side

Question 14

What are the two subtypes of nociceptive neurons and what makes them distinct from each other?

Answer 14

C-fiber (unmyelinated for pain from prolonged stimulation) and A-fiber (sharp pain, myelinated)

Question 15

What are the axons of proprioception and haptic PRGs like?

Answer 15

Large and well-myelinated for fast transmission

Question 16

What is deafferentation?

Answer 16

The loss of incoming sensory input due to damage to sensory fibers; loss of afferent input to a structure

Question 17

What happens to someone who had deafferentation?

Answer 17

They are unable to feel anything physically; but typically only one part of the body (can be all)

Question 18

What are the two somatosensory pathways to the brain?

Answer 18

The posterior spinothalamic tract and the anterior spinothalamic tract

Question 19

What kind of information does the posterior spinothalamic tract carry? How do they travel up the spinal cord?

Answer 19

They carry information about haptic and proprioceptive stimuli to the somatosensory cortex. Travel up the spinal cord ipsilaterally and then decussate in the brainstem

Question 20

What kind of information does the anterior spinothalamic tract carry? How do they travel up the spinal cord?

Answer 20

Carry information about nociceptive stimuli. Travels up the spinal cord contralaterally.

Question 21

What happens to both spinothalamic pathways once they enter the brain?

Answer 21

They project to the ventrolateral thalamus, join the medial lemniscus, and project to the somatosensory cortex

Question 22

What happens to somatosensation when there is unilateral damage to the spinal cord?

Answer 22

Unilateral loss of hapsis and proprioception below the point of injury on the ipsilateral side of the body and loss of nociception below the point of injury on the contralateral side of the body.

Question 23

What is a monosynaptic reflex? What is an example?

Answer 23

A reflex requiring one synapse between sensory input and movement. Happens in the spinal cord
Example is knee jerk

Question 24

What is the main pain pathway to the brain?

Answer 24

The anterior spinothalamic tract

Question 25

How is the reticular formation involved in pain perception?

Answer 25

Is handles arousal to deal with pain

Question 26

How is the amygdala involved in the perception of pain?

Answer 26

It handles associative learning between pain and context (e.g. food poisoning); emotional response to pain

Question 27

What is the hypothalamus's role in the perception of pain?

Answer 27

Deals with the hormonal and cardiovascular response. Triggers the release of some hormones to help cope with pain (physical or emotional)

Question 28

Approximately how many pain fibers are there that carry information to the somatosensory cortex?

Answer 28

8

Question 29

What is the gate theory of pain?

Answer 29

Haptic-proprioceptive stimulation can reduce pain perception via a "pain gate" in our spinal cord

Question 30

What is the pain gate?

Answer 30

The hypothetical neural circuit in which activity in fine-touch and pressure pathways diminishes the activity in pain and temperature pathways

Question 31

How does the interneuron in the pain gate prevent pain signals from going to the brain?

Answer 31

The signals from haptic-proprioceptive receptors trigger the release of endogenous opiates which act as an inhibitor and allows the gate to close.

Question 32

What happens when the periaqueductal gray matter (PAG) is electrically stimulated?

Answer 32

Pain is suppressed

Question 33

How do PAG neurons suppress pain?

Answer 33

They excite pathways that project to the spinal cord where they close the pain gate (and endogenous opioid release)

Question 34

What is periaqueductal gray matter?

Answer 34

Nuclei in the midbrain that surround the cerebral aqueduct joining the third and fourth ventricles; PAG neurons contain circuits for species-typical behaviors and play an important role in the modulation of pain

Question 35

What is referred pain?

Answer 35

Pain that arises in one of the internal organs but is felt on the surface of the body

Question 36

What is the only localized part of the somatosensory system?

Answer 36

The vestibular system

Question 37

What do the semicircular canals do?

Answer 37

Signal changes in the direction and speed of head movements

Question 38

What are the otolith organs? (2)

Answer 38

The utricle and saccule

Question 39

What do the utricle and saccule do?

Answer 39

Tell the position of the body in relation to gravity and linear acceleration

Question 40

What affect does cilia hair in the canals have on the vestibular nerve cells when they bend to the right?

Answer 40

The vestibular nerve has increased activation (on one side, decreased on the other)

Question 41

What direction is the utricle oriented?

Answer 41

Horizontally

Question 42

What direction is the saccule oriented?

Answer 42

Vertically

Question 43

What is vertigo?

Answer 43

The sensation of spinning when one is not moving caused by disfunction of the inner ear

Question 44

What is peripheral vertigo?

Answer 44

Displacement of otolith or calcium debris located in the posterior semicircular canal (aka: Meniere disease)

Question 45

What is central vertigo?

Answer 45

Lesions affecting the vestibular nuclei in the brainstem or their projections to the cerebellum; more serious that peripheral vertigo

Question 46

Body senses contribute to the perception of ________ (touch and pressure), _________ (location and movement), and _________ (pain and itch)

Answer 46

hapsis; proprioception, nociception

Question 47

Haptic-proprioceptive information is carried into the CNS by the _________ spinothalamic tract; nociceptive information is carried in by the __________ spinothalamic tract

Answer 47

Posterior, anterior

Question 48

The two tracts interact in the spinal cord to regulate pain perception via a(n) _________

Answer 48

Pain gate

Question 49

In the midbrain, the _________ suppresses pain by activating neuromodulatory circuits that inhibit pain pathways

Answer 49

Periaqueductal gray matter

Question 50

The only localized somatosensory system is the ________ system, which help sus maintain __________ by signaling information about the head's position and our movement through space

Answer 50

Vestibular; balance

Question 51

Explain how proprioception acts as the "eyes of the body"

Answer 51

Without proprioception, sensory information about body location and movement is lost and can be regained only by using vision