Chapter 15-homeostasis Flashcards
Where core body temp is monitored?
Hypothalamus
Type of cell that detects change in temp?
Thermoreceptor
Homeostatic mechanism that works to restore changes in temp to normal range?
Negative feedback
Responses that conserve heat?
- contraction of erector pili muscles
- curling up
- vasoconstriction of arterioles near skin surface
Behavioural response to decrease in temp?
Curling up
How large, thin ears help control body temp?
Large SA to lose heat
How ears that move forwards and backwards help control temp?
Increases air movement over skin
Define homeostasis?
Maintaining stable internal environment within narrow limits even though environment is changing
How negative feedback used to control blood glucose conc?
- B cells detect increase in blood glucose conc
- B cells in pancreas secrete insulin
- increases uptake of glucose by effector cells. Enters through glucose transport proteins
- glucose converted to glycogen by glycogenesis
- inc use of glucose in respiration
- if lower glucose conc, alpha cells in pancreases release glucagon
- increased conversion of glycogen to glucose by glycogenolysis
- increase covers on of other compounds like amino acids + lipids to glucose by gluconeogeneis
Role of ATP in cell?
- phosphate removed by hydrolysis to release 30kJmol-1 energy
- energy released used for metabolism
How endotherm prevents temp decreasing when external temp decreases?
- thermoreceptors stimulated by decrease in external temp
- impulses sent to hypothalamus through sensory neurones
- vasoconstriction of arterioles to reduce heat loss. Prevent heat Loss by conduction
- shivering. Involuntary muscle spasms to generate heat
- erector pili muscles contract to raise hairs/ fur to trap insulating layer of air
Why described as endotherm?
-generate heat from metabolism
Why more difficult for bees to maintain body temp than mammals? Both endotherms
- insects smaller + have larger SA:V ratio
- greater rate of heat loss
- mammals + birds have thicker insulation
Animals that are able to regulate + maintain core body temperature within narrow limits?
Endotherm
Increase in diameter of lumen of arterioles to allow more bloods to flow through?
Vasodilation
Hormone that increases metabolic rate so generates heat?
Adrenaline
Why are receptors + effectors important in homeostasis?
- body needs sensory receptors to monitor changes in external environment
- effectors respond to these changes + restore to original balance
Why effective homeostasis depends on negative rather than positive feedback systems?
- in (-) f.s , when change takes place, systems in body act to return situation to normal. They inhibit change
- in (+) f.s, when change takes place, systems in body act to reinforce the change
- in homeostasis, body seeks to maintain dynamic equilibrium. If there is a change, the need is to inhibit it + return things to original state
- possible with (-) but it (+)
What is an ectotherm?
Animals that use heat from their surroundings to warm their bodies so their core body temp is heavily dependent on environment
Example of ectotherm?
- lizards
- locusts
Give example of ectotherm warming up though radiation?
- basks in sun
- gains heat by radiation from sunlight
Give example of ectotherm warming up though conduction?
Presses against hot earth.
Gains heat by conduction
Give example of ectotherm warming up though convection?
Ectotherm stands up as high as if can off the ground
Will lose heat by convection currents in air around it
Give example of ectotherm warming up though evaporation?
- wallows in mud or water
- loses heat by evaporation of water from surface of skin
Why control of internal temp so important to ectotherms + endotherms?
- reactions of respiration are controlled by enzymes + have optimum temp
- if temp too low, reactions are v. Slow.
- not enough energy for muscle contraction for movement
- if temp too high, enzymes denature
- cells of body die which can lead to death
How evaporation of water in thermoregulatioj differs between ectotherms + endotherms?
- ectotherms don’t sweat. Cool down using evaporation of water only if they wallow or submerge in water
- when emerge from water or mud, they cool down as water evaporates from skin surface
- endotherms sweat as core body temp increases
- evaporation of water in sweat lowers skin surface temp which lowers temp of blood by conduction
Difference in role of peripheral temp receptors + temp receptors in hypothalamus?
- peripheral temp receptors are in skin + detect changes in surface temp
- receptors in hypothalamus detect blood temp within body
- peripheral receptors respond to environmental stimuli while receptors in hypothalamus respond directly to changes in core temp
Why endotherms in hot climates pale?
-pale colours reflect light + therefore heat so decreased amount of heat absorbed from sunlight
Why would you expect endotherms that live in cold climates to be dark coloured?
-dark colours absorb more heat +therefore help increase body temp
Not many endotherms in cold climates are acc dark. Why?
- cold places have lots of ice + snow
- dark colours show up against the white
- makes animals more visible to predators
Describe how arterioles under the skin helps control temperature?
- impulses sent to muscle
- muscles in arterioles contract
- lumen of arteriole constrict
- reduces blood flow to capillaries under skin
- reduces heat by evaporation
does secretion of adrenaline generate heat?
no
Why is it more difficult for moths and bublebees to maintain their body temp than mammals?
- have large SA:V ratio
- lose heat very quickly
