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Flashcards in Homeostasis Deck (35):
0

Define homeostasis?

Maintenance of a stable internal environment despite external changes

1

Where does homeostasis occur?

Cellular and whole body level

2

What is homeostasis essential for?

Normal cell function

3

What do your cells maintain?

Volume, pH, rate of division, ionic gradients, electrolyte concentration, rate of protein synthesis, level of nutrients & waste

4

What is a negative feedback loop?

Control system within the body that acts to restore the level of some variable to within a given range following any disturbance

5

What 3 things are required to form a feedback loop?

Receptors, integrator, effectors

6

Under what condition can a negative feedback loop be reset or overridden?

Bp during exercise

7

What makes positive feedback loop different to a negative one?

Magnifies a change, rather than negates it

8

When would a positive feedback loop be present?

Childbirth, lactation, ovulation, blood clotting

9

What happens to proteins when temperature reaches 42-43•c?

Become denatured (irreversible change)

10

What are the 4 different types of heat transference?

Radiation, conduction, convection, evaporation

11

What type of feedback loop is thermoregulation?

Negative

12

What are the receptor, integrator & effectors in thermoregulation?

Thermoreceptors, hypothalmus, physical responses

13

Where are thermoreceptors located?

Central nervous tissue & deep tissue

14

Where are peripheral thermoreceptors located?

Skin

15

Thermoregulators can only respond to one thing, what is this?

Either a fall or rise in temperature. Not both

16

How does the hypothalmus work as part of a negative feedback loop?

Receives information from thermoreceptors and organises appropriate effectors

17

Define effectors?

Strategies used by the body to restore normal levels

18

Effectors can be put in 2 categories. What are they?

Physical & behavioural

19

What responses does the body make to a fall in temperature?

Vasoconstriction of cutaneous blood vessels - blood flows to core away from surface, Shivering - muscles contract and relax very quickly to generate heat, Piloerection - hairs stand on end, Increased metabolic rate - heat is generated by the release of certain hormones

20

What hormones are secreted to help raise temp by increasing the bodies metabolic rate?

Adrenaline & thyroxine

21

What responses does the body make to a rise on temperature?

Vasodilation of cutaneous blood vessels - skin vessels widen so blood flows towards the skin (flushed), radiation, convection, conduction, hairs lie flat, sweating (evaporation)

22

What gland in the secretes sweat?

Eccrine glands of the skin

23

How much sweat is lost when cold?

Less than 500ml a day

24

How much sweat is lost when hot?

1.5 & 6 litres per hour in very hot weather and exercise

25

What do we loose from the body when we sweat?

Water & sodium chloride (salts)

26

What is it vital to replace to prevent heat exhaustion?

Fluids & salts

27

Why is thermoregulation harder for the elderly?

Thin skin, less hair, immobility, poor nervous system function, loss of subcutaneous fat, poor shivering, poor sweating

28

Define pyrexia?

Raised core temperature that is not caused by exercise or the enviroment

29

What can cause pyrexia?

Following infection by a virus or bacterium, hypothalmic set point is raised

30

In hyperthermia the body temperature rises. What temperature is it safe for the body to raise to for short periods of time?

43•c

31

What temperature for prolonged periods can lead to brain damage?

Excess of 40•c

32

What are the features of heat stroke?

Hot dry skin, weak respiration, low bp, cerebral oedema, convulsions, coma, death

33

Hypothermia is a drop in body temperature. At what temperature do your bodies thermoregulatory mechanisms fail?

33-34•c

34

What are the signs of hypothermia?

Comatose, shivering stops, sluggish reflexes, mental confusion, hallucinations, feeling of wellbeing may precede loss of consciousness, cardiac arrhythmias may occur leading to death from heart failure!