lecture 12

Question 1

somatic sensation

Answer 1

sensation from the skin, skeletal muscles, bones, tendons and joints -will give us rise to touch, pressure, awareness of the body’s position and movements, temperature and itch -responsible for : cutaneous sensation (touch), proprioception (sense of limb in space), kinesthesis (sense of limb during movement)

Question 2

skin types

Answer 2

• hairy
• glabrous (no hair eg. palms)

Question 3

layers

Answer 3

epidermis : outer layer gets washed off every day

dermis : inner layer where sensors are located

Question 4

mechanoreceptors

Answer 4

mechanically-gated ion channels open in response to mechanical deformation (pressure) on skin

Question 5

types of mechanoreceptors

Answer 5

1. Merkel’s corpuscle
2. meissne’s corpuscle
3. ruffini corpuscle
4. pacinian corpuscles

Question 6

merkels corpuscle

Answer 6

• furthest on exterior
• disk shaped
• small receptive field
• slow adapting to stimulus

Question 7

meissners corpuscle

Answer 7

• 2/4 second most posterior
• flattened cells
• small receptive field
• rapidly adapts to stimulus

Question 8

ruffini corpuscle

Answer 8

• ¾ second most interior
• branched fibers in a cylindrical capsule
• large receptive field
• slow adapting to stimulus

Question 9

pacinian corpuscle

Answer 9

• 4/4 deepest
• layered, onion-like capsule
• large receptive field
• rapidly adapt to stimulus

Question 10

high tactile acuity

Answer 10

small receptive fields (eg. hands and lips)

Question 11

responsible for posture and movement

Answer 11

muscle spindle, golgi tendon organ, and vestibular organs

Question 12

muscle spindle

Answer 12

stretch receptors

• spindles located parralel with the regular muscle fibers
• undergo the same length changes as the rest of the muscles thus,
• they are in an ideal location to sense changes in muscle length

-1a afferent neuron grup 2 afferent neuron

Question 13

golgi tendon organ

Answer 13

muscle tension monitor

• located in the tendon of the muscle in series with the muscle fibers
• they become stretched when the muscle contracts thus
• they sense the force the muscle exerts

Question 14

muscle receptors (proprioception)

Answer 14

a) muscle stretch
- stretch, spindles stretching, action potentials throughout stretch
b) extrafusal fiber contraction
- cant fire as well, less action potentials
c) alpha-gamma coactivation
- gama motor neuron detect contraction and lead to AP’s occuring

Question 15

thermoreceptors

Answer 15

sense temperature change

• small in diameter
• slow adapting (allow to get hands off hot stove)
• have little myelin
• originate as free neuron endings
• seperate receptors for hot and cold

Question 16

nociceptors

Answer 16

sense pain stimuli

• free axon endings
• small diameter
• little myelin
• respond to extreme mechanical deformation, temperature and many chemicals

Question 17

non-steroidal anti-inflammatory drugs (NSAiDS)

Answer 17

alleviate pain

• inhibit activity of cyclooxygenase enzyme
• important enzyme for production of prostaglandis
• prostaglandins are significant chemical stimulators of nociceptors
• blocking production= reducing firing rate of pain receptors

Question 18

referred pain

Answer 18

sensation of pain is experienced at a site other than the injured or diseased tissues (eg. heart attack0

afferent neurons converting on the same spinal nerve

Question 19

hyperalgesia

Answer 19

increased sensitivity to pain

-can last for hours after stimulus is gone

Question 20

analgesia

Answer 20

inability to sense physical pain

• can’t sense it is burning you
• leads to injuries etc.

Question 21

itch

Answer 21

thought to be a somatic sensation

• are free neuron ending
• slow adapting (why if you dont scratch it right away it persists)
• activate by mechanical stimulation or chemical mediators

Question 22

2 pathways of the somatosensory system

Answer 22

anterolatteral/spinothalamic pathway and dorsal column

Question 23

anterolateral/spinothalamic pathway

Answer 23

• crosses over sooner
• for pain and temperature
• goes through brainstem, then thalamus, ends up in somatosensory cortex

Question 24

dorsal column

Answer 24

• doesnt cross over right away, goes up towards brainstem and then secondary neuron crosses from brainstem to thalamus
• for movement, limb position, fine touch, pressure
• ends up in somatosensory cortex

Question 25

somatosensory cortex

Answer 25

right side of body is perceived on left side of somatosensory cortex

Question 26

dermatomes

Answer 26

area of skin supplied by given spinal cord segment

-sensory

Question 27

myotomes

Answer 27

group of muscles supplied by a given spinal cord segment

-motor