1
Q
what is homeostasis
A
- The maintenance of a dynamic equilibrium
- within narrow ranges in the body
2
Q
negative feedback
A
- a change is detected by sensory receptors
- effectors will work to reverse that change
- restore conditions to base level
- they reverse the initial stimulus
- E.g blood glucose levels
3
Q
positive feedback
A
- change is internal environment is detected by sensory receptors
- effectors are stimulated to reinforce that change and increase the response
E.g when BV is damaged, platelets stick to damaged region, initiated clotting and attracts more platelets until a clot is formed.
4
Q
ectotherm
A
- use heat from surroundings to warm bodies
- core body temp is dependant on their environment
- lizards
5
Q
endotherms
A
- rely on metabolic processes to warm bodies
- maintain stable core body temp regardless of env
- mammals and birds
6
Q
ectotherm - behavioural responses
A
- conduction : pressing bodies against warm ground
- cool down to ensure enzymes don’t denature: shelter from the sun (shade), hiding in cracks in rocks, digging burrows
- press bodies against cool earth
- move to water/mud
- orientate bodies so minimum SA exposed to un
- minimise movements to reduce metabolic heat generated
- extend areas of body to increase sa exposed to sun
7
Q
ectotherm - physiological responses
A
- alter heart rate to increase/decrease the metabolic rate
- ## darker colours in colder env
8
Q
endotherm - behavioural responses
A
- basking in the sun
- pressing against warm surfaces
- wallow in water
- hibernation (dormant in winter)
- aestivation (dormant in summer)
- Humans: clothes, house heat)
9
Q
endotherm - physiological responses : Vasodilation
A
- arterioles near skin surface dilate when temp inc
- arteriovenous shunt vessels constrict
- blood forces through capillary network close to skin surface
- skin flushed and cools due to inc radiation or when pressed against a cool surface (conduction)
10
Q
endotherm - physiological responses : sweating
A
- sweat spreads out across skin surface
- sweat evaporates
- heat is lost
- cools blood below surface
- animals that have fur open mouth and pant - water evaporates and heat is lost.
11
Q
endotherm - physiological responses : reducing insulating effect of hair/feathers
A
- hair erector muscles in skin relax
- hair/feathers lie flat on skin
- ## prevents trapping insulating layer of air
12
Q
endotherm - anatomical adaptations
A
- large SA:V
- maximises cooling
- large ears, wrinkly skin
- pale fur/feathers reflects radiation
- thick layer of insulating fat under skin
- hibernation (build up fat stores + lower metabolic rate)
13
Q
endotherm - physiological responses : vasoconstriction
A
- arterioles near surface of skin constrict
- arteriovenous shunt vessels dilate
- little blood flows through capillary network near skin surface
- skin is pale
- little radiation
- warm blood kept below surface
14
Q
endotherm - physiological responses : decreased sweating
A
- sweat productions stops
- no cooling down from sweat evaporation on skin surface
15
Q
endotherm - physiological responses : raising hair/feather
A
- erector pilli muscle contract
- hair/feather stand erect
- traps an insulating layer of air
- ## reduces cooling through skin
16
Q
endotherm - physiological responses : shivering
A
- rapid, involuntary contracting and relaxing of the large voluntary muscles
- ## metabolic heat from exothermic reactions warm up the body
17
Q
heat loss centre
A
- activated when temp of blood flowing through hypothalamus increases
- impulses sent to autonomic motor neurones
- impulse transmitted to effectors in skin + muscle that will decrease core temp
18
Q
heat gain centre
A
- activated when temp of blood flowing through hypothalamus decreases
- impulse sent to autonomic NS
- transmitted to effector that can increase core temp
