LECTURE 5

Question 1

What is the somatosensory system responsible for?

Answer 1

involved in conscious and unconscious perception of touch, proprioception, temperature and pain

Question 2

What is somatosensation?

Answer 2

is a term indicating the interpretation of sensory information from:
skin and musculoskeletal systems

Question 3

what is speed of information processing determined by?

Answer 3

Diameter of the axons
Degree of axonal myelination
Number of synapses in the pathway

Question 4

What are the three peripheral receptors and what do they do?

Answer 4

Mechanoreceptors- sensitive to touch, pressure, stretch, vibration.
Chemoreceptors- sensitive to chemicals released from cells.
Thermoreceptors- sensitive to temperature.

Question 5

What is a distal axon?

Answer 5

conducts messages from the receptor to the cell body

Question 6

What is a proximal axon?

Answer 6

projects from the cell body into the spinal cord or brainstem

Question 7

What is a receptive field?

Answer 7

area of skin innervated by a single afferent neuron

tend to be smaller distally and larger proximally.

Question 8

How is fine touch information transmitted?

Answer 8

transmitted through a variety of receptors all carried by A-Beta afferents

Question 9

what do a-delta fibers carry?

Answer 9

impulses produced by cooling

Question 10

what do C fibers carry?

Answer 10

information regarding heat

Question 11

What are the two types of pain response?

Answer 11

Fast pain or spinothalamic pain - is the initial and immediate sharp sensation that indicates the location of the injury.
Slow pain or spinolimbic pain - is the dull and throbbing ache following fast pain that is not well localized

Question 12

What are muscle spindles?

Answer 12

sensory organs in muscles that respond to stretch and provide information on fibre length and velocity of length change.

Question 13

what are the two types of muscle spindle endings and what are their roles?

Answer 13

Primary Endings (Ia afferents):
Rate of stretch
Length changes
Secondary Endings (II afferents):
Length changes

Question 14

What are the two types of intramural fibres?

Answer 14

Nuclear bag fibers - which are clumps of nuclei

Nuclear chain fibers - which are nuclei arranged in single file

Question 15

What are gamma motor neurons?

Answer 15

motor neurons are located in ventral horn of spinal cord
Innervate intrafusal muscle spindle receptors
Travel adjacent to alpha motor neurons to skeletal muscles

Question 16

What are Golgi Tendon Organs?

Answer 16

Tension in tendons is relayed from GTOs
Encapsulated nerve endings woven among the collagen strands near the musculotendinous junction
Monitor tension in tendons

Question 17

What are the 4 types of joint receptors?

Answer 17

Ligament receptors respond to tension of the ligaments (Ib)

Paciniform corpuscles respond to movement, not when joint position is constant (II)

Ruffini’s corpuscles signal extreme ranges of motion (II)

Free nerve endings stimulated by inflammation (alpha- delta and C)

Question 18

What are conscious relay pathways?

Answer 18

Conscious discriminative sensory perception

Question 19

What are divergent relay pathways?

Answer 19

Conscious and unconscious general sensory information to many locations in brainstem and cerebrum

Question 20

What are unconscious relay pathways?

Answer 20

Unconscious proprioception and posture information to cerebellum

Question 21

What are the two main conscious relay systems to the cerebral cortex?

Answer 21

Dorsal Column or Medial Lemniscus Tract
Fine touch, Proprioception and Vibration

Anterolateral Column or Spinothalmic Tract
Fast Pain, Temperature and Crude touch

Question 22

What is stereognosis?

Answer 22

is the ability to use touch and proprioceptive information to identify an object

Question 23

Where are the first, second and third order neurons in the dorsal tract?

Answer 23

first order from DRG to medulla- second order in medulla- third order in thalamus carry to primary somatosensory.

Question 24

What is facicullis gracilis?

Answer 24

medial column to lower body

Question 25

What is fascicles cuneatus?

Answer 25

lateral column to upper body

Question 26

Where are first, second and third order neurons located in spinothalamic tract?

Answer 26

First order in DRG, second in dorsal horn of spinal cord, third in thalamus.

Question 27

What is the difference between fast and slow pain?

Answer 27

Fast pain: is the initial and immediate sharp sensation which indicates the location of the injury Slow pain: is the dull, throbbing ache following fast pain that is not well localized

Question 28

What is analgesia?

Answer 28

is the absence of pain in response to stimuli that would normally be painful

Question 29

What is crossed analgesia?

Answer 29

is a pathologic circumstance where a single lesion can cause pain sensation to be lost on the ipsilateral side of the face and the contralateral side of the body

Question 30

What is the medial pain system?

Answer 30

divergent ascending network of neurons responsible for slow pain Activity of the medial pain system elicits motivational, withdrawal, arousal, and autonomic responses to pain

Question 31

What three tracts are used in the medial pain pathway?

Answer 31

Spinomesencephalic Spinoreticular Spinolimbic=Tracts are parallel ascending tracts-Only information in the spinolimbic tract is perceived as pain

Question 32

What is the Trigeminoreticulolimbic Pathway responsible for?

Answer 32

transmitting slow pain information to the face also using trigeminal nerve

Question 33

Where does the spinomesencephalic tract carry info too?

Answer 33

``` Superior Colliculus (midbrain) Involved in turning the eyes and head toward the source of noxious input ``` Periaqueductal gray Activates descending pain control system

Question 34

What is the reticular formation?

Answer 34

A neural network in the brainstem that includes the reticular nuclei and their connections

Question 35

Where does the spinelimbic tract transmit slow pain information?

Answer 35

limbic lobe in cerebral cortex, responsible for emotional response to pain

Question 36

Where do unconscious relay tracts transmit information from?

Answer 36

Proprioceptive receptors Activity in spinal interneurons via the spinocerebellar tracts

Question 37

What are the two high-fidelity pathways?

Answer 37

Posterior spinocerebellar pathway Transmits proprioceptive information from the legs and the lower half of the body Cuneocerebellar pathway Transmits proprioceptive information from the arm and upper half of the body Are ipsilateral

Question 38

What are the two internal feedback tracts?

Answer 38

Anterior spinocerebellar tract Transmits information from the thoracolumbar spinal cord Tract fibers divide to connect to both sides of cerebellum Bilateral projection reflects automatic coordination of lower limbs; versus more voluntary control of upper limbs Rostrospinocerebellar tract Transmits information from the cervical spinal cord to the ipsilateral cerebellum