Neuro - Ascending Sensory Systems

Question 1

Distinguish between encapsulated and unencapsulated sensory receptors.

Answer 1

• encapsulated - receptors with layered capsules and thin capsules
• unencapsulated - receptors with free nerve endings and endings with accessory structures

Question 2

What is Meissner’s corpuscle and its it encapsulated? What does it sense? Where is it found? What type of fiber does it contain?

Answer 2

• elongated, encapsulated endings in the dermal papillae of hairless skin
• discriminative touch
• concentrated in finger tips
• A-beta fibers - fast conducting

Question 3

What is Pacinian corpuscle and is it encapsulated? What does it sense? Where is it found? What type of fiber does it contain?

Answer 3

• encapsulated
• detection of vibration
• concentrated in fingers and palms
• A-beta fiber - fast conducting

Question 4

What are free nerve endings?

Answer 4

• branching terminations of sensory fibers in the skin with no obvious specialization around them other than partial ensheathment by Schwann cells
• provide sensation of pain, crude touch, and temperature

Question 5

Identify the components of the axon reflex. What is the triple response?

Answer 5

1. the skin is scratched
2. the skin reddens due to capillary dilation (REDLINE?)
3. free nerve ending discharge and conduct a signal to the:
   
   • spinal cord (orthodromic conduction)
   • branches (antidromic conduction)
   • release of substance P
   • arteriolar dilation (THE FLARE)
   • activation of mast cells (release of histamine)
   • increased capillary permeability (THE WHEAL)
     * triple response noted in CAPS

Question 6

What are the Rexed laminae?

Answer 6

Laminae I, II, V

Question 7

Which of the Rexed laminae play a role in pain transmission and pain regulation?

Answer 7

• pain transmission - Lamina I, II, V

- pain regulation - Lamina II

Question 8

What is the input to the periaqueductal gray?

Answer 8

• amygdala - anxiety, emotional pain regulation

- dorsolateral prefrontal cortex - cognitive (?) pain regulation

Question 9

Identify the structures in the neuroanatomical basis of pain regulation. What is the role of each? Identify the neurotransmitters involved.

Answer 9

periaqueductal gray stimulates the nucleus raphe magnus which sends a signal via the raphe spinal tract and serotonin to the inhibitory interneuron in Lamina II