The cold environment

Question 1

thermal neutral zone

Answer 1

• endotherms temperature tolerance zone
• maintain just heat movement across the skin 28-31 degrees if it gets warmer u rely on evaporation of sweat, lower than rely on increase metabolic rate and shivering
• in water much lower range 34.5 - 35.5 (harder for evaporation to work)

Question 2

the core temp:

Answer 2

• vary in regards to environment temperature

- core region changes, small the colder outside (heart lungs and brain)

Question 3

2 regions of skin

Answer 3

apical and nonapical

Question 4

apical skin

Answer 4

around the ears, face, nose, hands & feet

• have arteriovenous anastomosis (glomus body) blood pathway to loose and increase heat loss
• sympathetic control of blood vessels, activation of sympathetic nervous system = vasoconstriction (no dilation control just constriction)

Question 5

non-apical skin

Answer 5

• majority of skin
• sympathetic activity (vasoconstriction)
• sympathetic vasodilator activity (cholinergic –> Bradykinin–> vasodilation effect)

Question 6

arrhythmias :

Answer 6

irregular heart beat

Question 7

water specific heat per unit volume

Answer 7

~4000X greater than air

Question 8

water thermal conductivity

Answer 8

~25X greater than air

Question 9

convective heat transfer in water compared to air

Answer 9

~100 times higher

Question 10

even in freezing water takes ___ to die from hypothermia

Answer 10

30 mins, before core temperature

Question 11

__% of open water deaths within first few minutes of entering water

Answer 11

~55%

~60% of deaths are within 3 metres of safety
`67% are ‘good’ swimmers–> SO MOST DEATHS ARENT DUE TO HYPOTHERMIA

Question 12

4 phases associated with cold water immersion:

Answer 12

Initial response to immersion (0-3 min)

Short-term immersion (3-15 min)

Long-term immersion (>30 min)

Post immersion (afterdrop)

Question 13

Initial response to immersion: 0-3min CARDIOVASCULAR EFFECTS

Answer 13

• rapid tachycardia within seconds (colder the water the bigger the tachycardia)
• peripheral vacosinstriction and reduction in peripheral blood flow. increase in arteriole pressure
• in healthy people these strain on CV system minor risk but greater risk in cases of hypertension or CHD

Question 14

tachycardia =

Answer 14

rapid HR

Question 15

Initial response to immersion: 0-3min RESPIRATORY RESPONSES

Answer 15

• threat
• inspiratory gasp followed by uncontrollable hyperventilation
• 4X increase in ventilation during first minute of immersion
• fall in end-tidal and arteriole CO2 levels leaves to alkalosis and hypocapnia
• changes to ventricular fibrillation
• cerebal hypoxia
• left shift in Oxygen/Hb curve (O2 bound to haemoglobin more tightly)
• tetany, disorientation & clouding of consciousness
• feeling of dyspnoea (struggling breathing) continues for 3 mins reduction in breath holding ability
• you then adapt

Question 16

Initial response to immersion: 0-3min METABOLIC RESPONSES

Answer 16

• rapid increase in metabolic rate
• increased CO2 production may counteract hypocapnia. but there is increase load on heart leading to risk of cardiac irregularities

Question 17

Initial response to immersion: 0-3min HORMONAL REPSPONE

Answer 17

• evidence not conclusive
• some evidence for increases in plasma noradrenaline and adrenaline
• noradrenaline linked to activation of sympathetic nervous system

Question 18

cold response mechanism: response if initiated by __

Answer 18

activation receptors in the skin that are stimulated by cold conditions
-thermosensitive mechanoreceptors, thermal nociceptors and cold receptors

Question 19

cold receptors are located

Answer 19

in the superficial layers above subcutaneous fat

underpins rapid nature of response

Question 20

cold response respiratory effects mechanisms:

Answer 20

• direct stimulation of respiratory centre by thermoafferents linked to peripheral cold receptors.
• may also be stimulation of pathways stimulating inspiratory muscles

Question 21

cold response cardiovascular effects mechanisms:

Answer 21

predominantly linked to sympathetic activation

Question 22

cold response metabolic effects mechanisms:

Answer 22

linked to increased muscle tension, increased activity of respiratory muscles

Question 23

diving reflex: wheres it found

Answer 23

-homeostatic mechanism observed in air breathing vertebrates

Question 24

diving reflex: type of mechanism

Answer 24

protective; activated by exposure of cold thermoreceptors in the face to water

Question 25

diving reflex results:

Answer 25

pronounced bradycardia (slowing of heart) and suppression of expiratory pathways (driven by activation of parasympathetic pathways) 
-peripheral vasoconstriction --> sympathetic mechanism

Question 26

diving reflex: Overall effect

Answer 26

redues oxygen delivery to non essential areas allow extended survival or extended diving times

Question 27

The after drop:

Answer 27

people recovered from cold water immersion, they appear to be responsive and recovering well but then suddenly die due to cardia arrhythmia (irregular HB)

Question 28

mechanism of after drop:

Answer 28

convective; cold blood from extremities reaching core but some research suggest its conductive