Sensory Physiology

Question 1

What type of sensory fibers are the largest and fastest?

Answer 1

Aa - Ia and Ib

Question 2

What do Aa fibers supply?

Answer 2

Primary muscle spindles

Golgi tendon organ

Question 3

What type of sensory fibers are the smallest and slowest?

Answer 3

C - class IV

Question 4

What do C fibers supply?

Answer 4

Skin mechanoreceptors, thermal receptors, nociceptors

Question 5

What is the relationship of action potentials to the intensity of a stimulus?

Answer 5

Proportional

The more intense the stimulus, the higher the number of action potentials generated

Question 6

What is receptor adaptation?

Answer 6

Persistent stimulus without change in position or amplitude => neural response and sensation diminishes

Question 7

What receptors are activated with a stimulus is applied or removed? When a stimulus is sustained?

Answer 7

Rapidly adapting receptors

Slowly adapting receptors

Question 8

What types of sensory receptors are rapidly adapting?

Answer 8

Meissner corpuscle

Hair follicle receptors (both)

Pacinian corpuscle

Question 9

What types of sensory receptors are slowly adapting?

Answer 9

Hair follicle receptors (both)

Merkel disk

Ruffini corpuscle

Question 10

Meissner corpuscles detect what type of sensation? What is their field size?

Answer 10

Tap/flutter

Small

Question 11

Pacinian corpuscles detect what kind of sensation? What field size?

Answer 11

Vibration

Large

Question 12

Merkel cells detect what type of sensation? What field size?

Answer 12

Touch/pressure

Small

Question 13

Ruffini corpuscles detect what kind of sensation? What field size?

Answer 13

Skin stretch

Large

Question 14

If a two point prick is felt as one point on the skin, what is happening between the primary and secondary sensory neurons? What kind of receptive field does this usually occur in?

Answer 14

The primary sensory neurons from the two points are converging onto one secondary neuron

Large receptive field

Question 15

What is the purpose of presynaptic inhibition in perception of a stimulus?

Answer 15

Enhances perception by inhibiting neighboring neurons and localizing exactly where the stimulus is coming from

Question 16

What cells are the main output from the cortex?

Answer 16

Pyramidal cells

Question 17

What is the relationship between a neuronal column and its neighbors?

Answer 17

Neighboring columns receive sensory information from the same part of the body but a different sensory modality

Question 18

What cortex is involved in comparing objects, tactile sensation, and determining whether or not something becomes a memory?

Answer 18

Secondary somatosensory cortex (S2)

Question 19

What cortex is involved in taking all of the sensory input and analyzing spatial coordinate of self in the environment?

Answer 19

Parieto-temporal-occipital cortex

Question 20

What axons transmit information from the primary sensory cortex to the subcortical structures?

Answer 20

Descending corticothalamic axons (permits focusing)

Question 21

What projections allow for simultaneous processing of multiple sensations? On what side?

Answer 21

Cortico-cortical projections

Ipsilateral or contralateral

Question 22

What do corticofugal signals do?

Answer 22

Inhibit sensory input intensity (prevent sensory overload)

Question 23

Where are corticofugal signals transmitted?

Answer 23

Cortex to relay stations in thalamus, medulla, or spinal cord

Question 24

What is the doctrine of specific nerve energies?

Answer 24

No matter where along the afferent pathway is stimulated, the sensation that occurs is determined by the nature of the sensory receptor in the periphery connected to that pathway

(Light touch is perceived at all levels of the pathway)

Question 25

What is the law of projections?

Answer 25

No matter where along the afferent pathway is stimulated, the perceived sensation arises from the origin of the sensation

(Sensation from the right thumb is identified as the right thumb throughout the pathway)

Question 26

What is the difference between nociception and pain?

Answer 26

Pain is an unpleasant sensory/emotional experience associated with actual or potential tissue damage

Nociception is the neural process of encoding noxious stimuli that may be damaging (elevated blood pressure is not painful)

Question 27

What sensory afferent fibers transmit fast pain?

Answer 27

A-delta

Question 28

What occcurs during phenotype switching of nociceptors?

Answer 28

Non-nociceptive neurons acquire nociceptive-like properties in the event of trauma

Silent nociceptors become activated in cases of chronic pain/inflammation

Question 29

Nerve growth factor will induce expression of what peptides?

Answer 29

Substance P

CGRP (Calcitonin gene-related peptide)

Question 30

What kind of nociceptors are activated in diabetic neuropathy?

Answer 30

Non-peptidergic

Question 31

What ions are permeable through the TRP receptors?

Answer 31

Ca2+

Na+

K+

Question 32

Not only can TRP channels act as nociceptors, they can act as ___ receptors

Answer 32

Thermo

(Hot - TRPV, cold - TRPA)

Question 33

What NTs are released from C-fibers to the dendrites?

Answer 33

EAA

SP/CGRP

Question 34

In descending inhibition, what is the purpose of the serotonergic and noradrenergic neurons?

Answer 34

1. Activate local interneurons
2. Suppress spinothalalmic projection neurons

Question 35

What substance is involved in sub-threshold and neurogenic inflammation?

Answer 35

Bradykinin

Question 36

What cortex is responsible for processing and integrating all signals related to pain?

Answer 36

Insular cortex

Question 37

Asymbolia occurs as a result of damage to what structure? What happens?

Answer 37

Insular cortex

Pain without the emotional attachment

Question 38

What limbic structure is involved in the emotional aspect of pain?

Answer 38

Amygdala

Question 39

What tissue activate nociceptors for thermal, mechanical, and chemical stimuli?

Answer 39

Skin

(Joint, muscle, and viscera only process mechanical and chemical)