Hot Environments Flashcards

1
Q

at temperatures above 30C what method of heat loss is important

A

above 30C heat loss by radiation, conduction and convection become ineffective. EVAPORATIVE cooling becomes most important

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

two types of sweat gland

A

apocrine and eccrine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

apocrine sweat gland

A
  • armpits, genital,ears
  • no role in thermoregulation
  • low number and large diameter
  • secretion rich in lipids and carbohydrates
  • close to hair follicles and sebaceous gland (hair condition)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

eccrine sweat gland:

A

-high number & small diameter (50-100 microns)
-responsible for sweat production
150-340/cm2
-changes in populations (eskimos more in cheeks, less in thorax)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

components of eccrine sweat gland

A
  • Acinus region: primary secretion of a protein-free filtrate
  • Duct: Absorption of Na+ and Cl-
  • Pore
  • under sympathetic control (colonergic secretion, acetylcoline neuro transmitter)
  • GPCR receptor, Gq couple pathway
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

basal lateral (blood side) key transporters in Acinus

A
  • basal lateral membrane:
  • -Na+ K+ ATP ase pumps sodium out of cell, keep sodium inside the cell low
  • -NKCC (sodium potassium 2 chloride transforter) moves 1 K+, 1 Na+, 2 Cl- and water into cell
  • potassium channel to move it out = recycle

= gradient for chloride for Chloride to be secreted into lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

apical membrane key transporters in Acinus

A
  • chloride channel, chloride moves into lumen == hypertonic condition in the lumen
  • negative potential in lumen allowing for movement of Na+ (paracellular)

-also urea and lactate moved into lumen

ENDS being isotonic though (aqua porin 5)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

apical membrane key transporters in duct

A
  • ENAC (NA+)

- CFTR (Cl-) REABSORPTION FOR BOTH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

basal lateral membrane key transporters in duct

A
  • Na+ K+ ATPase pump (sodium out of cell)
  • K+ channel (out)
  • Cl- channel (out)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

eccrine and cystic fibrosis:

A

defect in CFTR channel, reabsorption of Na+ and Chloride in DUCT cells = large vol of salty sweat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

high levels of aldosterone (hormone) will up-regulate

A

ENAC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

sweat salinity varies with

A

flow rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

optimum sweat flow to reduce Na+ and Cl- loss

A

5mL/[min.m2]), increase flow rate = less Na and Cl removed (overload ENAC and CFTR channels)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

normal conditions can produce __ litres sweat/ hour

A

1.5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

once acclimatisation has taken place you can produce up to __ litres/hour

A

4 so we must adapt!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

sweat is ___, so you lose solute free water

A

hypertonic

-reducing cell volume and raising osmolarity in the cells

17
Q

why is it crucial for the body to adapt to increased temperatures?

A

as pre-adaption u can lose 30g of salt/day in sweat, post adaption this drops to a few grams/day = large volumes of v dilute sweat

18
Q

acclimatisation steps:

A

1) decrease sweating threshold (temp u start to sweat becomes lower)
2) increased volume of sweat
3) reduced osmolarity of sweat
4) decrease in HR
5) increase in total blood volume

-> over about 14 days

19
Q

acclimatisation: reduction in sodium being lost is due to an increase in

A

aldosterone production, which up regulates ENAC Na+ channel

20
Q

changes in sweating pattern:

A

through acclimatisation overall volume of sweat increases but also increase in legs and arms massively after adaptation (legs and arms have high SA)

21
Q

rate of heat loss by evaporation =

A

evaporative heat-transfer coefficient X (H2O vapour pressure of skin - H2O vapour pressure of environment) X SA

22
Q

Desert :

A

environment water vapour pressure V low –> easy for sweat to evaporate

23
Q

Rainforest :

A

Very high humidity –> water vapour pressure high, harder for sweat to evaporate

24
Q

3 problems with hot environments:

A
  • heat cramps
  • heat collapse
  • heat stroke
25
Q

Heat cramps:

A

cramping in calf/ abdomonal muscles

  • muscles contracted and not able to relax
  • loss of sodium, calcium and magnesium
26
Q

heat collapse:

A
  • 38.5-40 core temp
  • huge vasodilation to periphery , effect on blood pressure and amount of blood going to brain
  • sweating maintained
27
Q

why is it better to rehydrate by isotonic solutions not water

A

water just dilute,

28
Q

heat stroke

A
  • 41 degrees core
  • peripheral vasoconstriction, harder to get heat loss from body
  • after big loss of fluid from the body
  • no sweating