1- Neurophysiology of Thermoregulation

Question 1

Why do we need to thermoregulate?

Answer 1

Most people cannot tolerate a core temp of 42c whilst having a skin temp of 38c without heat illness

At a core temp of 32c most individuals lose consciousness

Question 2

Fatal heat storage due to no heat loss:

Answer 2

About 4 hours at rest and 25 minutes at moderate intensity exercise

Question 3

Geographical temperatures:

Answer 3

Average Global temp- 15.5 C, Sea bed- 3 C

Hottest inhabited place: 58 C- Libya

Coldest inhabited place: -68 C- Siberia

Question 4

Human metabolic and temperature stats:

Answer 4

Max metabolic rate: 25kcal. min
Min metabolic rate: 1kcal. min
Mean core temp- 37 C
Upper lethal core temp: 44 C
Lower lethal core temp: 25 C

Question 5

Mechanisms of Temp Control:

Answer 5

Sweating- 30-66 C, max 2 L.hr- 1300W

Shivering- 26 - -10C, max 40-50% VO2 max- 600W

Question 6

Thermoneutral Zone:

Answer 6

Range of ambient temperatures where body can maintain its core temperatures through dry heat loss (Vaso dilation and constriction)

Question 7

Body temp regulation:

Answer 7

Temp Receptors: skin, core, muscle CNS -> Controller: hypothalamus -> Controlled actions: Vasomotor, sweating, shivering, hormones, behavioural -> Controlled system (influenced by metabolic heat production, environment) affects B
body temp.

Question 8

Peripheral Thermoreceptors

Answer 8

Sensitive to temp.:
Warm- Free nerve endings; conduction velocity 0.2-2m/s; deep dermis
Cold- Free nerve endings; conduction velocity 20m/s; superficial sub-epidermal (0.22mm depth); 3-4x more than warm; lips:20, fingers: 5 per cm2

Question 9

Deep body thermoreceptors:

Answer 9

Preoptic area and hypothalmus
Mid brain
Medulla oblongata
Spinal chord
Abdominal cavity
Blood vessels
Joints

Question 10

Preoptic area and hypothalmus

Answer 10

Highest thermal sensitivity: preoptic nucleus-anterior
hypothalamic area (PO/AH)

PO/AH heating can inhibit
cold-induced vasoconstriction and shivering and
activate panting in a cold environment

Hypothalamic cooling can inhibit panting and
vasodilation and activate shivering in a hot
environmen