Chapter 15-homeostasis

Question 1

Where core body temp is monitored?

Answer 1

Hypothalamus

Question 2

Type of cell that detects change in temp?

Answer 2

Thermoreceptor

Question 3

Homeostatic mechanism that works to restore changes in temp to normal range?

Answer 3

Negative feedback

Question 4

Responses that conserve heat?

Answer 4

• contraction of erector pili muscles
• curling up
• vasoconstriction of arterioles near skin surface

Question 5

Behavioural response to decrease in temp?

Answer 5

Curling up

Question 6

How large, thin ears help control body temp?

Answer 6

Large SA to lose heat

Question 7

How ears that move forwards and backwards help control temp?

Answer 7

Increases air movement over skin

Question 8

Define homeostasis?

Answer 8

Maintaining stable internal environment within narrow limits even though environment is changing

Question 9

How negative feedback used to control blood glucose conc?

Answer 9

• 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

Question 10

Role of ATP in cell?

Answer 10

• phosphate removed by hydrolysis to release 30kJmol-1 energy
• energy released used for metabolism

Question 11

How endotherm prevents temp decreasing when external temp decreases?

Answer 11

• 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

Question 12

Why described as endotherm?

Answer 12

-generate heat from metabolism

Question 13

Why more difficult for bees to maintain body temp than mammals? Both endotherms

Answer 13

• insects smaller + have larger SA:V ratio
• greater rate of heat loss
• mammals + birds have thicker insulation

Question 14

Animals that are able to regulate + maintain core body temperature within narrow limits?

Answer 14

Endotherm

Question 15

Increase in diameter of lumen of arterioles to allow more bloods to flow through?

Answer 15

Vasodilation

Question 16

Hormone that increases metabolic rate so generates heat?

Answer 16

Adrenaline

Question 17

Why are receptors + effectors important in homeostasis?

Answer 17

• body needs sensory receptors to monitor changes in external environment
• effectors respond to these changes + restore to original balance

Question 18

Why effective homeostasis depends on negative rather than positive feedback systems?

Answer 18

• 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 (+)

Question 19

What is an ectotherm?

Answer 19

Animals that use heat from their surroundings to warm their bodies so their core body temp is heavily dependent on environment

Question 20

Example of ectotherm?

Answer 20

• lizards

- locusts

Question 21

Give example of ectotherm warming up though radiation?

Answer 21

• basks in sun

- gains heat by radiation from sunlight

Question 22

Give example of ectotherm warming up though conduction?

Answer 22

Presses against hot earth.

Gains heat by conduction

Question 23

Give example of ectotherm warming up though convection?

Answer 23

Ectotherm stands up as high as if can off the ground

Will lose heat by convection currents in air around it

Question 24

Give example of ectotherm warming up though evaporation?

Answer 24

• wallows in mud or water

- loses heat by evaporation of water from surface of skin

Question 25

Why control of internal temp so important to ectotherms + endotherms?

Answer 25

• 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

Question 26

How evaporation of water in thermoregulatioj differs between ectotherms + endotherms?

Answer 26

• 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

Question 27

Difference in role of peripheral temp receptors + temp receptors in hypothalamus?

Answer 27

• 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

Question 28

Why endotherms in hot climates pale?

Answer 28

-pale colours reflect light + therefore heat so decreased amount of heat absorbed from sunlight

Question 29

Why would you expect endotherms that live in cold climates to be dark coloured?

Answer 29

-dark colours absorb more heat +therefore help increase body temp

Question 30

Not many endotherms in cold climates are acc dark. Why?

Answer 30

• cold places have lots of ice + snow
• dark colours show up against the white
• makes animals more visible to predators

Question 31

Describe how arterioles under the skin helps control temperature?

Answer 31

• impulses sent to muscle
• muscles in arterioles contract
• lumen of arteriole constrict
• reduces blood flow to capillaries under skin
• reduces heat by evaporation

Question 32

does secretion of adrenaline generate heat?

Answer 32

no

Question 33

Why is it more difficult for moths and bublebees to maintain their body temp than mammals?

Answer 33

• have large SA:V ratio

- lose heat very quickly