the somatosensory system (2.4)

Question 1

divisions of the somatosensory system (3)

Answer 1

exteroceptive, proprioceptive, interoceptive

Question 2

exteroceptive vs proprioceptive vs interoceptive divisions

Answer 2

exteroceptive: external stimuli (applied to the skin; i.e., touch, pain, temperature)
proprioceptive: body position (i.e., muscles, joints, balance)
interoceptive: body conditions (i.e., temperature and blood pressure)

Question 3

touch mechanoreceptors of the skin (4)

Answer 3

Meissner’s corpuscles, Merkel’s disks, Ruffini endings, Pacinian corpuscles, free nerve endings

Question 4

Meissner’s corpuscles vs Merkel’s disks vs Ruffini endings vs Pacinian corpuscles vs free nerve endings

Answer 4

Meissner’s corpuscles: rapid adaptation; light touch, stroke
Merkel’s disks: adapt slowly; respond to gradual skin indentation
Ruffini endings: slow adaptation; respond to skin stretch
Pacinian corpuscles: largest and deepest; onionlike; adapt rapidly; vibration, strong pressure
Free nerve endings: simplest cutaneous receptors; neuron endings with no specialized structures on them; sensitive to temperature change and pain

Question 5

transduction (direct or indirect)

Answer 5

direct (Na+ flows in after direct opening of channels)

Question 6

polymodal nociceptors

Answer 6

nociceptor: pain receptor
polymodal: respond to all 3 kinds of stimuli (mechanical, thermal, chemical)

Question 7

thermoreceptors

Answer 7

highly sensitive to temperature in the innocuous range (not harmful); distinct warm and cold types; lower threshold to activate; i.e., TRP receptors (direct transduction and transmission) let Ca2+ flow

Question 8

transmission via…

Answer 8

Aδ fibers: myelinated; rapid adapting
C fibers: unmyelinated; slow adaptation

Question 9

two-point sensitivity test

Answer 9

will not know how many things poke you

Question 10

dermatome

Answer 10

area of the body that is innervated by the left and right dorsal roots of a given segment of the spinal cord; carry information from somatosensory receptors; gather together in nerves and enter the spinal cord via the dorsal roots

Question 11

ascending tracts (2)

Answer 11

dorsal-column medial lemniscus, anterolateral system

Question 12

dorsal-column medial lemniscus vs anterolateral system

Answer 12

dorsal-column medial lemniscus: mainly touch and muscles/joints (proprioception); first synapse in the dorsal column nuclei of the medulla; receptors -> dorsal column nuclei of the medulla (decussation) -> medial lemniscus fibers -> VPN in thalamus -> SI, SII, or posterior parietal cortex
anterolateral: mainly pain and temperature; three tracts

Question 13

anterolateral system tracts (3)

Answer 13

spinoreticular (look at something that causes pain), locus coeruleus (alert signal), spinothalamic tract (exclaim out in pain)

Question 14

muscle spindles vs Golgi tendon organs

Answer 14

muscle spindles: in parallel with muscle fibers; signal muscle length
Golgi tendon organs: in serious with muscle fibers; signal muscle tension
*both slow responders

Question 15

vestibular system

Answer 15

monitors the movement and position of the head, giving us our sense of balance or equilibrium; includes two structures (semicircular canals, otolith organs)

Question 16

semicircular canals vs otolith organs

Answer 16

semicircular canals: detect turning movements of the head; angular accelerations; push-pull
otolith organs: sense changes of head angle (position of the head); linear accelerations

Question 17

somatosensory homunculus

Answer 17

somatotopic map; distorted (more sensitive tactile/position discrimination)

Question 18

columnar organization

Answer 18

four functional strips (middle 2 are sensory from the skin,;outer 2 are sensory from muscles and joints)

Question 19

dorsal vs ventral stream

Answer 19

dorsal: from SI to posterior parietal cortex; direct attention
ventral: through SII (bilateral) to prefrontal; perception of object shape