Sensory Physio

Question 1

Peripheral nerves are classified by two schemes.

Answer 1

1. Their contribution to a compound ACTION POTENTIAL (A, B, and C waves)
   recorded from an entire mixed peripheral nerve.
2. Based on FIBER diameter, myelin thickness, and conduction velocity
   (classes I, II, III, and IV).

Question 2

Which sensory (afferent) fiber type has the largest fiber diameter and the fastest conduction velocity?

Answer 2

A(alpha)

Question 3

Which sensory (afferent) fiber type has the smallest fiber diameter and the slowest conduction velocity?

Answer 3

C

Question 4

An appropriate stimulus applied to a somatosensory receptor produces a ? that, when large enough, leads to action potentials that can be carried over a considerable distance into the central nervous system

Answer 4

generator potential

Question 5

Information from all sensory systems except the olfactory are relayed through the ? on its
way to the cerebral cortex.

Answer 5

thalamus

Question 6

Sensory receptors encode the ? of the stimulus in the ?

of the receptor potential

Answer 6

• intensity

- amplitude

Question 7

The number of active receptors ? with increased intensity of the stimulus

Answer 7

increases

Question 8

When a stimulus persists unchanged for several minutes without a change in position or amplitude, the neural response diminishes and sensation is lost.

Answer 8

Receptor adaptation

Question 9

Receptors that respond to prolonged and constant stimulation

Answer 9

slowly adapting receptors

Question 10

Receptors that respond only at the beginning or end of a stimulus are only active when the stimulus intensity increases or decreases.

Answer 10

rapidly adapting receptors

Question 11

? are responsible for the sense of touch

Answer 11

Mechanoreceptors

Question 12

Individual mechanoreceptor fibers convey information from a limited area of skin

Answer 12

Receptive fields

Question 13

Allows for spatial resolution of detailed textures

Answer 13

2-point discrimination

Question 14

2-point discrimination:

• Tactile acuity is highest in?

Answer 14

fingertips and lips (smallest receptive fields)

Question 15

2-point discrimination:

• Tactile acuity is lowest on?

Answer 15

the calf, back and thigh (largest receptive

field)

Question 16

Primary afferent neurotransmission is controlled by ? and ?

Answer 16

pre- and

postsynaptic inhibitory mechanisms.

Question 17

probably the more powerful form of

inhibitory control in all primary afferent fibers.

Answer 17

Presynaptic inhibition

Question 18

This inhibition is actually a diminished excitatory signal:

Answer 18

1. GABAergic associated influx of Cl- into the axon
2. Results in hyperpolarization
3. Less Ca2+ enters cytosol
4. Leads to less NT release

Question 19

Cortical processing steps

Answer 19

1. Initial processing of the signal
2. Integration of the initial processing into
   larger schemes
3. Emotional response to the processing

Question 20

Each area of sensory cortex
shares with its subcortical
components a map of at least
part of the sensory periphery.

Answer 20

Response mapping

Question 21

Which layer of the cortex is enlarged in primary sensory cortex?

Answer 21

III and IV

Question 22

Which layer of the cortex is the main site of termination of axons from the
thalamus?

Answer 22

III and IV

Question 23

Cortex:

• Main output neurons are the?

Answer 23

pyramidal cells

Question 24

• Neurons stacked above and below each other are fundamentally ?
• Neuronal columns side by side are significantly ? from one
  another.

Answer 24

• similar

- different

Question 25

Sensory information arrives at it’s column in layer ? (via thalamus)

Answer 25

IV

Question 26

Sensory cortex includes ?, ?, and ?

Answer 26

primary, secondary and association areas

Question 27

* Located in post-central gyrus * Brodmann Area 3, 1, 2 * First stop for most cutaneous senses * Somatotopic representation

Answer 27

Primary somatosensory cortex (S1)

Question 28

involved in the integration of the information for position sense as well as size, shape discrimination.

Answer 28

Primary somatosensory cortex (S1)

Question 29

* Located in wall of the sylvian fissure * Receives input from S1 * Somatotopic representation (less detailed) * Cognitive touch

Answer 29

Secondary somatosensory cortex (S2)

Question 30

Comparisons between objects, different tactile sensations and determining whether something becomes a memory.

Answer 30

Secondary somatosensory cortex (S2)

Question 31

• High level interpretation of sensory inputs • Receives input from multiple sensory areas • Analyzes spatial coordinates of self in environment * Names objects * Many more functions

Answer 31

``` Parieto-temporal-occipital association cortex (PTO) ```

Question 32

What sends projections back down to subcortical structures?

Answer 32

Primary sensory cortex

Question 33

* sends projections back down to subcortical structures * Most often back to thalamus. • Descending corticothalamic axons > ascending thalamocortical axons. • Permits focusing activities

Answer 33

Primary sensory cortex

Question 34

establish parallel paths of sensation

Answer 34

Cortico-cortical projections

Question 35

• Links primary and association areas of the sensory cortex • Vision, audition, and somatic senses establish a hierarchy within the system. • Allows for simultaneous processing of multiple sensations. • Can be ipsilateral or contralateral hemispheric connections (via corpus callosum).

Answer 35

Cortico-cortical projections

Question 36

* Transmitted back from cortex to lower relay stations in the thalamus, medulla or spinal cord. * Controls the intensity of sensory sensitivity. * Typically inhibitory and suppresses sensory input

Answer 36

Corticofugal signals

Question 37

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

Answer 37

Law of projections

Question 38

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

Answer 38

pain

Question 39

The neural process of encoding noxious stimuli (a stimulus that is damaging or threatens damage to normal tissues.). - Consequences of encoding may be autonomic (e. g. elevated blood pressure) or behavioral (motor withdrawal reflex or more complex nocifensive behavior). Pain sensation is not necessarily implied.

Answer 39

Nociception

Question 40

A high- threshold sensory receptor of the peripheral somatosensory nervous system that is capable of transducing and encoding noxious stimuli.

Answer 40

nociceptors

Question 41

Location of pain

Answer 41

* Somatic or cutaneous pain * Muscle pain * Deep pain * Visceral pain

Question 42

Pain characterization: nociceptor modality

Answer 42

1. Thermal 2. Mechanical 3. Chemical

Question 43

non-nociceptor afferent that suddenly induce expression of the receptors that are activated by thermal, mechanical, and chemical. Non noceptor that suddenly express nociceptor properties so become fake nociceptor and transmit noxious stimuli

Answer 43

Phenotype switching

Question 44

so rarely stimulated that eventually if something happens (like ex chronic inflammatory (a chronic condition)) can change genetic expression.

Answer 44

Silent nociceptors

Question 45

• Lacks specialized receptor cells or encapsulations • Characterization can further be broken down by various molecular markers

Answer 45

free nerve endings.

Question 46

Transient receptor potential family of receptors

Answer 46

* TRPV1 * TRPA1 * TRPM8

Question 47

TRP receptors - Ligand-gated non- selective cation channel permeable to?

Answer 47

- Ca2+, Na+ and/or K+

Question 48

Activated by ligand capsaicin (ingredient in chilipepepr)

Answer 48

TRPV1

Question 49

Activated by menthol (in mint)

Answer 49

TRPM8

Question 50

- Activated by allyl. Isothiocyanate | - Found in mustards and radishes

Answer 50

TRPA1

Question 51

activated by hotter temperatures like fires

Answer 51

TRPV1

Question 52

activated by extreme cold

Answer 52

TRPA1

Question 53

Mechanosensitive sodium-channel expressed by nociceptors?

Answer 53

Na 1.7

Question 54

Receptor activated by ATP

Answer 54

P2X

Question 55

Receptor activated by H+

Answer 55

ASIC

Question 56

can be released by noceptors but also once released, can circle back around and activate noceceptors again

Answer 56

SP and CGRP

Question 57

What activates nociceptors?

Answer 57

- Sodium - ATP - H+ - SP and CGRP - Histamine - Kinins (bradykinin)

Question 58

Nociceptors are modulated by ? and ? in the dorsal horn.

Answer 58

- descending systems | - interneurons

Question 59

rubbing the spot that hurts | to ease the pain

Answer 59

Gate control theory of pain

Question 60

Gate control theory of pain includes?

Answer 60

* TENS units * Phantom-limb pain * Acupuncture?

Question 61

dampens input on its way to the cortex

Answer 61

Descending inhibition

Question 62

Gate is closed: No pain is sensed because the inhibitory interneuron is blocking the nociceptive signal from continuing to move forward.

Answer 62

Gate control theory

Question 63

Steps of Gate Control Theory of Pain

Answer 63

1. Activate an Aβ fiber by normal stimuli. The central process of this fiber branches in the dorsal horn and synapses on an inhibitory interneuron upon which it releases EAA. 2. The activated interneuron releases glycine and inhibits the secondary sensory neuron of the nociceptive pathway. 3. Rubbing an area of affected skin activates the A β fiber and reduces the sensation of pain.

Question 64

Descending inhibition: 1. PAG are activated by ?, ?, and ? 2. Descending projections travel to: • ? 3. ? and ?released into dorsal horn and activate inhibitory interneurons 4. Local inhibitory interneurons release ? 5. Opiates activate ? receptors on pre-synaptic (and post-syanaptic) terminals of a C-fiber. 6. Results in reduction of SP from the C-fiber and reduces nociception

Answer 64

- opiates, EAA, and cannabinoids - Locus Coeruleus (NE) - Raphe nucleus (Serotonin) - Serotonin and NE - opiates (like enkephalin) - mu

Question 65

Descending serotonergic and noradrenergic neurons: 1. Activate local ? 2. Suppress ?

Answer 65

1. interneurons 2. spinothalamic projection neurons

Question 66

What 2 signals are both used for chronic pain and central sensitization?

Answer 66

- Peripheral signal | - Central signal

Question 67

Important inflammatory mediator?

Answer 67

Bradykinin

Question 68

receive input from | nociceptors and play a role in localization of pain

Answer 68

S1 and S2

Question 69

particularly important | in interpretation of nociception

Answer 69

Insular cortex

Question 70

• Processes information about internal state of the body • Contributes to autonomic response to pain * Integrates all signals related to pain. *** * Damage causes asymbolia. **

Answer 70

Insular cortex

Question 71

sensation of pain but without emotional unpleasantness

Answer 71

Asymbolia

Question 72

Part of the brain important in the emotional component to pain.

Answer 72

Amygdala

Question 73

Visceral input travels with autonomic nerves goes to ? and ?, integrating physiological changes associated with visceral pain.

Answer 73

- hypothalamus | - medulla

Question 74

What stimuli is adequate to activate nociceptors in skin?

Answer 74

- Thermal - Mechanical (cutting, pinching, crushing) - Chemical

Question 75

What stimuli is adequate to activate nociceptors in joints?

Answer 75

- Mechanical (rotation/torque beyond the joint's normal range of motion) - Chemical

Question 76

What stimuli is adequate to activate nociceptors in muscle?

Answer 76

- Mechanical (blunt force, stretching, crushing, overuse) | - Chemical

Question 77

What stimuli is adequate to activate nociceptors in viscera?

Answer 77

- Mechanical (distension, traction on the mesentery) | - Chemical

Question 78

``` • Brain requires some experience to localize pain, visceral pain is not experienced often enough in early development to “train” the brain to localize it. ``` • Afferents converge in the dorsal horn. • Antidromic signaling further diffuses visceral pain across multiple organs.

Answer 78

Referred Pain