WEEK 4 - The Peripheral Nervous System

Question 1

classification of sensory receptors by stimulus type

Answer 1

1. photoreceptors: stimulated by light (only eyes)
2. mechanoreceptors: touch, pressure (including blood), vibration, stretch
3. chemoreceptors: respond to chemical substances dissolved in body fluids
4. thermoreceptors: change in temperature
5. nociceptors: pain receptors

Question 2

classification of sensory receptors by location type

Answer 2

1. exteroreceptors: respond to stimuli outside body, touch, pressure, pain. temperature, including mouth
2. interoceptors: stimuli inside, chemical changes, cause discomfort and person is unaware
3. proprioceptors: respond to stretch in skeletal muscles, informs brain of movements

Question 3

2 general types of sensory receptors

Answer 3

non-encapsulated: free nerve endings, temperature, pressure, pain, itching, found in layers on the skin, and glands

modified free nerve endings, light pressure, basal layer of epidermic (SB)

hair follicle receptor: surrounds hair follicles

encapsulated: one or more fibre terminals of sensory neurons enclosed in CT capsule
almost all are mechanoreceptors

tactile: very very sensitive light touch eg nipples
lamellar: internal deep pressure, in dermis and hypodermis eg nipples
bulbous: deep continuous pressure in dermis and hypodermis
muscle spindles: muscle stretch, length in skeletal muscle
tendon organs: stretch due to muscle contraction in tendons
joint kinesthetic receptors: stretch in joints capsules

Question 4

intrafusal fibers

Answer 4

• needed for muscles to communicate when the muscle is stretched
• no myofilaments in middle where muscle spindle wraps
• stimulated by stretch
• important for reflexes

Question 5

5 components of reflex arc

Answer 5

• reflexes do not require the involvement of the brain
  1. receptor
  2. sensory neuron
  3. integration center
  4. motor neuron
  5. effector

2 types of reflexes: somatic (activate skeletal muscle) and autonomic (activate visceral effectors)

Question 6

ANS - preganglionic fibres release Ach

Answer 6

• ach binds to nicotinic receptor on postganglionic neuron and is always stimulatory bec allows ions to pass through

Question 7

parasympathetic pathway

Answer 7

• post ganglionic neurons release each
• binds to muscarinic receptor on effector organs of parasympathetic pathway and is excitatory