Somatic Sensation

Question 1

This process occurs in response to a sustained stimulus and results in a neuron showing a decreased firing rate over time

Answer 1

Adaptation

Question 2

What are the two types of adaptation a neuron may experience?

Answer 2

Fast and slow

Question 3

What are some characteristics of slow adaptation?

Answer 3

• It provides continuous information (tonic)
• It is relatively non-adapting
• Helps the cell respond to a sustained stimulus

Question 4

What are some examples of neurons that undergo slow adaptation?

Answer 4

• Joint capsule
• Muscle spindle
• Merkel’s discs
• Ruffini end organs
• Nociceptors

Question 5

What are some characteristics of fast adaptation?

Answer 5

• Rapid or phasic
• Reacts strongly when a change is taking place
• Responds to vibration

Question 6

What are some examples of neurons that undergo fast adaptation?

Answer 6

• Hair receptors (30-40Hz)
• Pacinian corpuscles (250Hz)
• Meissner’s corpuscles (30-40Hz)

Question 7

Membrane adaptation is thought to be due to entry of what ion during action potentials?

Answer 7

Calcium

Question 8

Which spinal joints are the most heavily innervated?

Answer 8

Cervical joints

Question 9

What are the four types of sensory receptors of the spinal joints?

Answer 9

Type I, II, III, IV

Question 10

Of the four spinal joint sensory receptors, which are the largest? Smallest?

Answer 10

Type I are the largest, while Type IV are the smallest

Question 11

Of the four spinal joint sensory receptors, which are myelinated? Unmyelinated?

Answer 11

Type I-III are myelinated, while Type IV are unmyelinated

Question 12

This type of mechanoreceptor is found on the outer layers of the joint capsule and fires at a degree proportional to the joint movement. They are low threshold, slow adapting, and have a tonic effect on lower motor neuron pools.

Answer 12

Type I mechanoreceptors

Question 13

This type of mechanoreceptor is found in the deeper layers of the joint capsule and functions in joint movement monitoring. They are low threshold, rapidly adapting, and have a phasic effect on lower motor neuron pools.

Answer 13

Type II mechanoreceptors

Question 14

This type of mechanoreceptor has recently been found in spinal joints and is the joint version of a Golgi tendon organ. They have a very high threshold and are slow adapting.

Answer 14

Type III mechanoreceptors

Question 15

This type of receptor is a nociceptor and are completely inactive in a physiologically normal joint. They have a very high threshold and activate with joint narrowing, increased capsule pressure, or chemical irritation.

Answer 15

Type IV receptors

Question 16

What does information transmitted to the brain from mechanoreceptors in fingers allow us to do?

Answer 16

• Feel the shape and texture of objects
• Play musical instruments
• Type on computer keyboards
• Palpate and perform adjustments
• Perform a multitude of tasks using our hands

Question 17

Tactile information from mechanoreceptors is ____ by receptors and must be integrated by the ____.

Answer 17

Fragmented; brain

Question 18

What is one of the most important complex functions of the somatosensory system?

Answer 18

The ability to recognize objects placed in the hand on the basis of touch alone.

Question 19

This is the ability to perceive form through touch.

Answer 19

Stereognosis

Question 20

What does stereognosis test?

Answer 20

• The ability of the dorsal column-medial lemniscal system to transmit sensations from the hand
• The ability of cognitive processes in the brain where integration occurs.

Question 21

What are the categories of sensory modalities?

Answer 21

Pressure receptors, cold receptors, warmth receptors, and nociceptors

Question 22

Which sensory modalities compose our perception of wetness? Ticklishness? Itching?

Answer 22

• Wetness: stimulation of pressure and temperature
• Ticklishness: gentle stimulation of pressure receptors
• Itching: gentle stimulation of nociceptors

Question 23

When fine textures are stroked on the fingerpad skin, the fingerprint ridges ____ and cause ____ ____ to respond enabling the detection of microtexture.

Answer 23

Vibrate; Pacinian corpuscles

Question 24

When perceiving shape, the depth of indentation and change in curvature of the skin surface are encoded by discharge rates of what types of fibers?

Answer 24

Slow adapting afferent fibers

Question 25

When perceiving shape, the velocity and rate of change in skin surface curvature are encoded by discharge rates of what types of fibers?

Answer 25

Slow adapting and rapidly adapting afferent fibers

Question 26

What are the rapidly adapting cutaneous mechanoreceptors?

Answer 26

Meissner's corpuscles, hair follicle receptors, and Pacinian corpuscles

Question 27

Where are Meissner's corpuscles typically found?

Answer 27

They are typically found in glabrous (non hairy) skin and concentrated in the fingertips

Question 28

Where are hair follicle receptors typically found?

Answer 28

Hairy skin

Question 29

Where are Pacinian corpuscles typically found?

Answer 29

Subcutaneous tissue

Question 30

What are the slowly adapting cutaneous mechanoreceptors?

Answer 30

Merkel's discs and Ruffini end organs

Question 31

What do Merkel's discs sense?

Answer 31

Curvature of an object's surface

Question 32

How are Ruffini end organs activated?

Answer 32

By stretching the skin. This can occur even at some distance away from the receptor

Question 33

These receptors are rapidly adapting (vibratory sensation) and are superficial (small receptive field).

Answer 33

Meissner's corpuscles

Question 34

These receptors are rapidly adapting (vibratory sensation) and are deep (large receptive field).

Answer 34

Pacinian corpuscle

Question 35

These receptors are slowly adapting (sustained pressure) and are superficial (small receptive field).

Answer 35

Merkel's discs

Question 36

These receptors are slowly adapting (sustained pressure) and are deep (large receptive field).

Answer 36

Ruffini's end-organ

Question 37

This area of the brain receives projections from the thalamus, has a somatotopic organization, and each central neuron has a receptive field.

Answer 37

Somatosensory cortex

Question 38

This term is used to describe the process by which a 1st order neuron synapses and subsequently excites 2nd order neurons as well as interneurons. This results in surrounding inhibition and the enhancing of edges.

Answer 38

Lateral inhibition

Question 39

Does lateral inhibition improve acuity?

Answer 39

No

Question 40

What are the two major pathways of the somatosensory cortex?

Answer 40

Dorsal column-medial lemniscal system (Epicritic) and the anterolateral system (Protopathic)

Question 41

This somatosensory pathway contains 1st order neurons that synapse in the brain stem and deals with most aspects of touch and proprioception.

Answer 41

Dorsal column-medial lemniscal system (Epicritic)

Question 42

This somatosensory pathway contains 1st order neurons that synapse in the dorsal horn of the spinal cord and deals with sensations of crude touch, nociception, temperature, tickle, itch, and sexual sensations.

Answer 42

Anterolateral system (Protopathic)

Question 43

What do 2nd order neurons do in both somatosensory pathways?

Answer 43

They cross to the other side and ascend, synapsing in the thalamus

Question 44

Does the dorsal column-medial lemniscal system (Epicritic) contain ipsiliateral or contralateral fibers?

Answer 44

Ipsilateral

Question 45

Does the anterolateral system (Protopathic) contain ipsiliateral or contralateral fibers?

Answer 45

Contralateral

Question 46

This type of pathway is old (phlogenetically), synapses in the cord, contralateral in the cord, has small fibers, initiates actions, and is involved with pain, temperature, tickle, itch, and sexual sensations.

Answer 46

Protopathic

Question 47

This type of pathway is new (phlogenetically), synapses in the brain stem, ipsilateral in the cord, has large fibers, modifies actions, and is involved with fine touch/proprioception.

Answer 47

Epicritic

Question 48

Most nerve cells are responsive to how many modalities?

Answer 48

Only one

Question 49

Which receptors provide input to Brodmann area 3a?

Answer 49

Muscle stretch receptors (spindles)

Question 50

Which receptors provide input to Brodmann area 3b?

Answer 50

Cutaneous receptors

Question 51

Which receptors provide input to Brodmann area 2?

Answer 51

Deep pressure receptors

Question 52

Which receptors provide input to Brodmann area 1?

Answer 52

Rapidly adapting cutaneous receptors

Question 53

What are the three different types of neurons in Broadmann areas 1 and 2 that have complex feature detection capabilities?

Answer 53

- Motion sensitive neurons - Direction-sensitive neurons - Orientation-sensitive neurons

Question 54

This type of neuron within Brodmann areas 1 and 2 responds well to movement in all directions but not selectively to movement in any one direction.

Answer 54

Motion sensitive neurons

Question 55

This type of neuron within Brodmann areas 1 and 2 responds much better to movement in one direction than in another.

Answer 55

Direction-sensitive neurons

Question 56

This type of neuron within Brodmann areas 1 and 2 responds best to movement along a specific axis.

Answer 56

Orientation-sensitive neurons

Question 57

This Brodmann area integrates tactile information from mechanoreceptors in skin with proprioceptive inputs from underlying muscles and joints.

Answer 57

Brodmann area 5

Question 58

This Brodmann area receives visual, tactile, and proprioceptive inputs. It integrates stereognostic and visual information.

Answer 58

Brodmann area 7

Question 59

What are some of the main functions of the posterior parietal cortex (Brodmann area 5 and 7)?

Answer 59

- Projects to motor areas of the frontal lobe | - Sensory initiation and guidance of movement

Question 60

This area of the brain is located in the superior bank of the lateral fissure and projects to the insular cortex, which innervates regions of the temporal lobe believed to be important in tactile memory. Projections from the primary somatic sensory cortex are required for function of this area.

Answer 60

Secondary somatic sensory cortex (S-II)

Question 61

These types of receptors are sensitive to temperature of the skin. They are slow adapting, discharge spontaneously under normal conditions, and discharge phasically when skin temperature is changing rapidly.

Answer 61

Thermoreceptors (two types: cold and warmth)

Question 62

At extreme skin temperatures thermoreceptors become inactive and these types of receptors become active.

Answer 62

Nociceptors (pain)

Question 63

What types of stimuli can activate nociceptors?

Answer 63

- Mechanical stimuli - Thermal stimuli - Chemical stimuli

Question 64

This term is used to describe the reception of signals in the CNS evoked by stimulation of specialized sensory receptors that provide information about tissue damage.

Answer 64

Nociception

Question 65

This term is used to describe the perception of adverse or unpleasant sensation that originates from a specific region of the body.

Answer 65

Pain

Question 66

These are the least differentiated of all sensory receptors and can be sensitized by tissue damage.

Answer 66

Nociceptors

Question 67

This nociceptive pathway contains A delta fibers, utilizes glutamate, deals with mechanical/thermal stimuli, has good localization, and is associated with sharp or pricking pain.

Answer 67

Fast nociceptive pathway

Question 68

This nociceptive pathway contains C fibers, utilizes substance P and glutamate, deals with polymodal/chemical stimuli, has poor localization, and is associated with dull, burning, or aching pain.

Answer 68

Slow nociceptive pathway

Question 69

Where does the fast nociceptive pathway terminate?

Answer 69

In the ventrobasal complex of the thalamus

Question 70

Where does the slow nociceptive pathway terminate?

Answer 70

It has a diffuse termination to the reticular formation, tectal areas of the mesencephalon, and the periaqueductal grey

Question 71

These fibers are part of the slow nociceptive pathway adn secrete both substance P and glutamate. They synapse primarily in substantia gelatinosa (lamina II and III of the spinal cord)

Answer 71

C-fibers

Question 72

Between glutamate and substance P, this secretion's effects are transient and short acting.

Answer 72

Glutamate

Question 73

Between glutamate and substance P, this secretion is release more slowly and concentrations build over time. It is responsible for slow pain.

Answer 73

Substance P (substance powder)

Question 74

What are some examples of nociceptive pathways?

Answer 74

- Spinothalamic-major (fast and slow) - Spinoreticular - Spinomesencephalic - Spinocervical (mostly tactile) - Dorsal columns (mostly tactile)

Question 75

What are the cardinal signs of inflammation?

Answer 75

Rubor: redness Calor: heat Tumor: swelling Dolar: pain

Question 76

What are the two types of pain control mechanisms?

Answer 76

Peripheral and Central

Question 77

What is gating theory?

Answer 77

It involves inhibitory interneurons in the cord impacting nociception projection neurons

Question 78

Where are endogenous opioids located and what do they do?

Answer 78

- Periaqueductal grey has enkephalin projections to Raphe - Raphe nucleus has serotonin projections to the cord - Inhibitory interneurons in the cord release enkephalins, which can cause pre-synaptic inhibition of incoming C and A delta fibers as well as 2nd order projection neurons

Question 79

Where are cannabinoid receptors found?

Answer 79

In the brain (CB1)

Question 80

Where are endogenous cannabinoids produced? What are some examples?

Answer 80

- They are produced in the brain | - Examples: anandamide, 2-arachidonoylglycerol (2-AG)

Question 81

What substance contributes to a "runner's high" during exercise?

Answer 81

2-arachidonoylglycerol (2-AG)

Question 82

What are some intracranial origins of headaches?

Answer 82

- Meningitis: inflammation of the meninges - Migraine: vasoconstriction/vasodilation - Irritation of the meninges: abuse of alcohol or constipation

Question 83

What are some extracranial origins of headaches?

Answer 83

- Muscle spasm - Irritation of nasal passages and/or sinuses - Eye disorders - Cervical joint dysfunction - Traction of dura

Question 84

What is the relationship between the cervical spine and headaches?

Answer 84

- CN V has sensory innervation of most of the head and face - CN V nucleus of termination extends to C2 - C2 afferents synapse both in the dorsal horn and CN V nuclei - Overlap between CN V and C2 can cause headache associated with cervical dysfunction.

Question 85

This term is used to describe the phenomenon of increasing signal strength transmitted by multiple fibers.

Answer 85

Spatial summation

Question 86

This term is used to describe the phenomenon of increasing signal strength due to an increased firing rate of a single fiber.

Answer 86

Temporal summation

Question 87

This term is used to describe a neuronal circuit causing both excitation and inhibition.

Answer 87

Reciprocal inhibition

Question 88

This term is used to describe a postsynaptic potential that lasts for milliseconds and can continue to excite a neuron.

Answer 88

Synaptic afterdischarge

Question 89

This is a type of circuit in which positive feedback due to collateral fibers restimulates itself or neighboring neurons in the same circuit.

Answer 89

Reverberatory circuit

Question 90

What are some characteristics of a self excitatory system (continuous signal output)?

Answer 90

- Less negative membrane potential | - Leaky membrane to Na+/Ca++

Question 91

What causes rhythmical signal output?

Answer 91

Reverberating circuits

Question 92

What are some mechanisms within the nervous system that maintain the stability of neuronal circuits?

Answer 92

- Inhibitory circuits - Fatigue of synapses - Decreasing resting membrane potential - Long-term changes by down regulation of receptors