Body energy homeostasis

Question 1

What activates TRP channels?

How do they respond?

Answer 1

Hot/cold stimuli = they are thermosensitive
Allow Na+ flow through the cell and depolarisation
Temperature sensation

Question 2

Describe AV anastamoses

Answer 2

Present in areas where skin is exposed
Thick smooth muscle layer means there is a direct pathway from the arterioles to veins
There is a low resistance pathway for blood flow to the skin

Question 3

Describe the ascending neural pathways
What neurones are present ?
What type of neurones?

Answer 3

Transmit sensory information from the periphery
Made of sensory neurones which have their cell bodies mostly in peripheral ganglia and an axon which spreads into the tissue to determine its temperature

2 classes of sensory neurones which either respond to warmth ( 32-40) or cold ( 14-30)
Cell bodies in DRG or trigeminal ganglia

They are pseudouni polar with 2 axonal branches
1 branch innervates the skin/viscera
Other branch projects back to dorsal horn or spinal trigeminal nucleus

Question 4

Describe how the descending pathways control blood flow to the skin

Answer 4

Mainly controlled by vasoconstriction/vasodilation: Sympathetic fibres innervating vascular smooth muscle release NA

• RPA + RVLM has pre motor neurones which project onto the IML of the spinal cord to control vasomotor responses
• This activates pre ganglionic fibres to regulate sympathetic outflow

Question 5

Describe how the descending pathways control sweating

Answer 5

Mainly controlled by the release of acetylcholine from sympathetic fibres innervating sweat glands
- RVMN has pre motor neurones projecting onto the IML of spinal cord
- They project onto pre ganglionic fibres
- Pre ganglionic fibres innervate sympathetic outflow fibres
RVMN activates correlates with activation of the POA

Question 6

What does sympathetic stimulation of alpha 1 adreno receptors cause?

Answer 6

Contraction of arrector pili smooth muscle cells

Question 7

What are the 2 types of sweat glands?

Describe the main features of both

Answer 7

Apocrine : No active role in thermoregulation

• Large diameter but small in number
• Ducts empty into hair follicles

Epocrine: Active role in thermoregulation
- Small diameter but large in number

Question 8

Describe the actions of shivering thermogenesis as a way to produce heat

Answer 8

Repeated contractions of skeletal muscle causes heat production
Activation of Y motor neurones also causes unstable activation of the muscle spindle reflex to keep muscle length constant

Question 9

Where is BAT found?

What stimulates BAT + what does it result in?

Answer 9

Around the arteries supplying the brain,heart and major organs
Sympathetic innervation stimulates lipolysis
- Fatty acids released cause uncoupling of the ETC
- H+ can leak out via UCP1 channel
- Short circuiting of the ECT and H+ release allow for energy dissipation as heat

Question 10

What are some methods of non shivering thermogenesis?

Answer 10

• BAT + lipolysis
• Sarcolipin uncouples Ca2+ transport by the SERCA pump so ATP hydrolysis occurs in the absence of Ca2+, energy from this reaction is dissipated as heat