Somatic Sensory System

Question 1

cutaneous

Answer 1

of or relating to the skin

Question 2

subcutaneous

Answer 2

hypodermic

Question 3

mechanoreceptor

Answer 3

A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion by firing action potentials.

Question 4

nociceptor

Answer 4

a sensory receptor that responds to potentially damaging stimuli by sending nerve signals to the spinal cord and brain.

Question 5

thermoceptor

Answer 5

A thermoreceptor is a sensory receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range.

Question 6

free nerve ending

Answer 6

A free nerve ending (FNE) is an unspecialized, afferent nerve ending, meaning it brings information from the body’s periphery toward the brain. They function as cutaneous receptors and are essentially used by vertebrates to detect pain.

Question 7

encapsulation

Answer 7

localization of knowledge within a module

Question 8

Receptor potential

Answer 8

Receptor potential, a type of graded potential, is the transmembrane potential difference of a sensory receptor.

Question 9

Sensory transduction

Answer 9

In physiology, transduction is the conversion of a stimulus from one form to another.

Question 10

Meissner’s corpuscles

Answer 10

Meissner’s corpuscles (or tactile corpuscles) are a type of mechanoreceptor. They are a type of nerve ending in the skin that is responsible for sensitivity to light touch. In particular, they have highest sensitivity (lowest threshold) when sensing vibrations lower than 50 Hertz. They are rapidly adaptive receptors.

Question 11

Pacinian corpuscles

Answer 11

Pacinian corpuscles are one of the four major types of mechanoreceptor. They are nerve endings in the skin, responsible for sensitivity to vibration and pressure. Vibrational role may be used to detect surface, e.g., rough vs. smooth.

Question 12

Phasic

Answer 12

rapidly adapting; receptors respond maximally but briefly to stimuli

Question 13

Tonic

Answer 13

slowly adapting; receptors keep firing as long as stimulus is present

Question 14

Four major types of receptors specialized to provide to CNS info about touch, pressure, vibration, cutaneous tension

Answer 14

Meissner’s Corpuscles, Pacinian corpuscles, Merkel’s disk, Ruffini’s corpuscles

Question 15

Meisner’s corpuscles, Pacinian corpuscles, Merkel’s disk, Ruffini’s corpuscles

Answer 15

Four major types of receptors specialized to provide to CNS info about touch, pressure, vibration, cutaneous tension

Question 16

Merkel’s disc

Answer 16

Merkel nerve endings are mechanoreceptors found in the skin and mucosa of vertebrates that provide touch information to the brain. The information they provide are those regarding pressure and texture. Each ending consists of a Merkel cell in close apposition with an enlarged nerve terminal.

Question 17

Ruffini’s corpuscles

Answer 17

The Bulbous corpuscle or Ruffini ending or Ruffini corpuscle is a class of slowly adapting mechanoreceptor thought to exist only in the glabrous dermis and subcutaneous tissue of humans. This spindle-shaped receptor is sensitive to skin stretch, and contributes to the kinesthetic sense of and control of finger position and movement. It is believed to be useful for monitoring slippage of objects along the surface of the skin, allowing modulation of grip on an object.

Question 18

Two-point discrimination

Answer 18

Two-point discrimination is the ability to discern that two nearby objects touching the skin are truly two distinct points, not one. It is often tested with two sharp points during a neurological examination and reflects how finely innervated an area of skin is.

Question 19

Two-point discrimination findings

Answer 19

The smallest and most dense sensory units are located in those areas that have the greatest somatosensory cortical representation. Normally, a person should be able to recognize two points separated by as little as 2-4 mm on the lips and finger pads, 8-15 mm on the palms and 30-40 mm on the shins or back.

Question 20

posterior column-medial lemniscus

Answer 20

upon damage to this pathway, two-point discrimination can be impaired. is the sensory pathway responsible for transmitting fine touch, vibration and conscious proprioceptive information from the body to the cerebral cortex. The name comes from the two structures that the sensation travels up: the posterior (or dorsal) columns of the spinal cord, and the medial lemniscus in the brainstem.

Question 21

receptive field

Answer 21

The receptive field of a sensory neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron. Receptive fields have been identified for neurons of the auditory system, the somatosensory system, and the visual system.

Question 22

Proprioception

Answer 22

the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement

Question 23

Muscle spindle

Answer 23

Muscle spindles are sensory receptors within the belly of a muscle, which primarily detect changes in the length of this muscle. This information can be processed by the brain to determine the position of body parts. The responses also play an important role in regulating muscle contraction, by activating motoneurons via the stretch reflex to resist muscle stretch.

Question 24

Intrafusal muscle fibers

Answer 24

Intrafusal muscle fibers are skeletal muscle fibers that comprise the muscle spindle and are innervated by gamma motor neurons. These fibers are a proprioceptor that detect the amount and rate of change of length in a muscle.

Question 25

Extrafusal motor fibers

Answer 25

Extrafusal muscle fiber is a term given to standard muscle fibers as to distinguish them from intrafusal muscle fibers. Extrafusal muscle fibers are innervated by alpha motor neurons and generate tension by contracting, thereby allowing for skeletal movement.

Question 26

Nuclear bag fibers

Answer 26

A nuclear bag fiber is a type of intrafusal muscle fiber that lies in the center of a muscle spindle. Each has a large number of nuclei concentrated in bags and they cause excitation of both the primary and secondary nerve fibers.

Question 27

Nuclear chain fiber

Answer 27

Nuclear chain fibers are intrafusal fibers which, along with nuclear bag fibers, make up the muscle spindle. Their nuclei are aligned in a chain and they excite the secondary nerve. They are static while the nuclear bag fibers are dynamic in comparison.

Question 28

Gamma motoneurons (γ-motoneurons)

Answer 28

Gamma motoneurons (γ-motoneurons), also called gamma motor neurons, are the efferent component of the fusimotor system, the system by which the central nervous system controls and modifies muscle spindle sensitivity.

Question 29

Relationship regarding muscle spindle abundance

Answer 29

Large muscles that generate relatively coarse movements get less muscle spindles; smaller ones requiring finesse have many more

Question 30

Golgi tendon organs

Answer 30

a proprioceptive sensory receptor organ that is located at the insertion of skeletal muscle fibers into the tendons of skeletal muscle. It provides the sensory component of the Golgi tendon reflex. Responds to tension as opposed to muscle length.

Question 31

Stretch and Golgi tendon reflex relationship

Answer 31

The stretch reflex operates as a feedback mechanism to control muscle length by causing muscle contraction. In contrast, the tendon reflex operates as a feedback mechanism to control muscle tension by causing muscle relaxation before muscle force becomes so great that tendons might be torn.

Question 32

Joint receptor

Answer 32

source for proprioceptive feedback that is not well-understood; rapidly adapting to provide dynamic information about limb position and joint movement

Question 33

Haptics

Answer 33

(haptic) of or relating to or proceeding from the sense of touch

Question 34

Dorsal root ganglia

Answer 34

dorsal root ganglion (or spinal ganglion) is a nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves. Location of neuronal cell bodies that produce first-order sensory axons

Question 35

first-order neurons

Answer 35

initiating afferent neurons of the sensory process, located in dorsal root ganglia

Question 36

Dorsal root

Answer 36

the afferent sensory root of a spinal nerve

Question 37

dorsal column-medial lemniscus pathway

Answer 37

the sensory pathway responsible for transmitting fine touch, vibration and conscious proprioceptive information from the body to the cerebral cortex; as well as tactile pressure, barognosis, graphesthesia, stereognosis, recognition of texture, kinesthesia and two-point discrimination

Question 38

Spino-thalamic pathway

Answer 38

The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch. The pathway decussates at the level of the spinal cord, rather than in the brainstem like the posterior column-medial lemniscus pathway and corticospinal tract.

Question 39

bifurcate

Answer 39

divide into 2 forks

Question 40

ipsilateral

Answer 40

Belonging to or occurring on the same side of the body

Question 41

Dorsal column

Answer 41

Posterior column or dorsal column refers to the area of white matter in the dorsomedial side of the spinal cord. It is part of an ascending pathway that is important for well-localized fine touch and conscious proprioception called the posterior column-medial lemniscus pathway.

Question 42

gracile nucleus

Answer 42

Located in the medulla oblongata, the gracile nucleus is one of the dorsal column nuclei that participate in the sensation of fine touch and proprioception of the lower body (legs and trunk). It contains second-order neurons of the dorsal column-medial lemniscus system, which receive inputs from sensory neurons of the dorsal root ganglia and send axons that synapse in the thalamus.

Question 43

cuneate nucleus

Answer 43

One of the dorsal column nuclei, the cuneate nucleus is a wedge-shaped nucleus in the closed part of the medulla oblongata. It contains cells that give rise to the cuneate tubercle, visible on the posterior aspect of the medulla. It lies laterally to the gracile nucleus and medial to the spinal trigeminal nucleus in the medulla.

Question 44

cuneate nucleus function

Answer 44

The cuneate nucleus is part of posterior column-medial lemniscus pathway, carrying fine touch and proprioceptive information from the upper body to the contralateral thalamus via the medial lemniscus.

Question 45

dorsal column nuclei

Answer 45

a pair of nuclei in the brainstem. The name refers collectively to the cuneate nucleus and gracile nucleus, which are present at the junction between the spinal cord and the medulla oblongata. Both nuclei contain secondary neurons of the dorsal column-medial lemniscus pathway, which carries fine touch and proprioceptive information from the body to the brain.

Question 46

gracile tract

Answer 46

The fasciculus gracilis (tract of Goll or gracile fasciculus) is a bundle of axon fibres in the posterior column of the spinal cord and carries information from the middle thoracic and lower limbs of the body.

Question 47

Cuneate tract

Answer 47

The fasciculus cuneatus (tract of Burdach, named for Karl Friedrich Burdach) is a tract of nerves in the spinal cord that primarily transmits information from the arms. It is part of the posterior column-medial lemniscus pathway.

Question 48

internal arcuate fibers

Answer 48

Internal arcuate fibers are the axons of second-order neurons contained within the gracile and cuneate nuclei of the medulla oblongata. These fibers cross (decussate) from one side of the medulla to the other to form the medial lemniscus. Part of the dorsal column-medial lemniscus system (second neuron), the internal arcuate fibers are important for relaying the sensation of fine touch and proprioception to the thalamus and ultimately to the cerebral cortex.

Question 49

medial lemniscus

Answer 49

The medial lemniscus, also known as Reil's band or Reil's ribbon, is a pathway in the brainstem that carries sensory information from the gracile and cuneate nuclei to the thalamus.