The Sensory Nervous System

Question 1

What is a ‘unencapsulated’ sensory receptor?

Answer 1

The sensory nerve endings are ‘free’ and not wrapped in any connective tissue

Question 2

What is an ‘encapsulated’ sensory receptor?

Answer 2

Nerve endings are wrapped in glial cells or connective tissue to increase sensitivity/selectivity with respect to the modality it responds to

Question 3

Explain how Nociceptors work

Answer 3

These are free nerve endings that signal tissue damage. The injured tissue releases chemicals (bradykinin, prostaglandins, histamine, ATP, K+) that activate Nociceptors.

• FIRST PAIN - myelinated axons, fast conducting speed, sharp, localised, stabbing pain at time or injury.
• SECOND PAIN - unmyelinated axons, slow conducting speed, long-lasting, dull, diffuse pain.

Question 4

Explain the pain signalling pathway

Answer 4

Pain signals reach the brain via 2 main routes:

• HEAD - CNV, VII, IX, X - brain stem (1st) thalamus (2nd) and then cerebral cortex (3rd)
• NECK DOWN -
  1) spinothalamic tract - somatic pain signals to cortex - perception
  2) spinoreticular tract - visceral, emotional, behavioural response to pain (nausea, fear)
  3) posterior column - visceral pain

Question 5

What is the difference between chronic and acute pain?

Answer 5

• CHRONIC - not associated with disease/injury, no biological purpose, hard to treat. No recognisable end point. Can be psychological.
• ACUTE - provoked by specific injury/disease, servers a biological purpose and is treatable. Associated with SNS activation and is self-limited

Question 6

Identify and list the special senses

Answer 6

• Vision
• Hearing
• Smell
• Taste

Question 7

List the different types of sensory receptors

Answer 7

• Thermoreceptors (heat/cold)
• Proprioceptors (movement)
• Nociceptors (pain)
• Chemoreceptors (chemicals)
• Photoreceptors (light)
• Baroreceptors (BP)

Question 8

Morphine:

Answer 8

Can cause respiratory depression

Question 9

What is NOT a side effect of NSAIDs

Answer 9

Constipation

Question 10

Which of the following is the correct pathway for the transfer of sensory information from the nociceptor to the brain?

Answer 10

Nociceptor ~ dorsal horn of spinal cord ~ spinothalamic tract ~ ventral posterior lateral nucleus in the thalamus ~ sensory cortex

Question 11

Nociceptors

Answer 11

Are sensitive to the chemical substances released by damaged cells or tissues