Homeostasis

Question 1

What is homeostasis?

Answer 1

Body maintains a dynamic equilibrium, with small fluctuations over a narrow range of conditions

Question 2

What do sensory receptors do?

Answer 2

Detect changes in internal and external environments of organism

Question 3

What are some examples of what homeostasis monitors?

Answer 3

Detecting changes e.g.
PH of blood, Core body temp, Conc of urea and sodium ions in blood

Question 4

What do negative feedback loops involve?

Answer 4

-Receptor to detect stimulus
-Coordination system to transfer information through body
-Effector to carry out response

Question 5

What are the outcomes of negative feedback loops?

Answer 5

-Stimulus continuously monitored

If there is an increase in the factor, the body responds to make the factor decrease

If there is a decrease in the factor, the body responds to make the factor increase

Question 6

How do negative feedback loops work?

Answer 6

A small change is detected by sensory receptors, and effectors work to reverse the change and restore conditions to base level

Question 7

What happens in positive feedback systems?

Answer 7

A change in the internal environment of the body is detected by sensory receptors, effectors reinforce that change and increase response.

Question 8

Whats an example of a positive feedback loop

Answer 8

Blood clotting cascade

Question 9

What is cell signalling and why do we need it?

Answer 9

Process where cells communicate with each other, allows multicellular organisms to control and coordinate bodies to respond to environment

Question 10

What are the basic stages of cell signalling?

Answer 10

Stimulus received by receptor
Stimulus converted to a signal- transduction
Signal transmitted to effector
Response made

Question 11

What is thermoregulation?

Answer 11

Maintenance of a relatively constant core body temp to maintain an optimum enzyme activity

Question 12

What physical processes does thermoregulation depend on?

Answer 12

-Exothermic chemical reactions
-Latent heat of vaporisation
-Radiation
-Convection
-Conduction

Question 13

What are ectotherms?

Answer 13

Use their surroundings to warm their bodies, dependant on environment

Include inveribrate animals, fish, amphibians and reptiles

Question 14

Why do ectotherms living in water not need to regulate often?

Answer 14

High heat capacity of water, temperature of water doesn’t change much

Question 15

What are endotherms?

Answer 15

Rely on their metabolic processes to warm up and maintain a stable core temperature despite the external temperature.

Metabolic rate is higher so needs to consume more food to meet needs

Question 16

What behavioural responses have ectotherms developed?

Answer 16

Sometimes need to warm up to speed up metabolic reactions for them to be active e.g. orientate bodies for a large SA

Increase body temp by conduction through pressing body against warm ground

Cool down by preventing core temperature reaching point where enzymes begin to denature- shelter from sun etc

Question 17

What are physiological responses to warming

Answer 17

Dark colours absorb more- lizards in cold climates are darker
Alter heart rate to maintain metabolic processes

Question 18

How do endotherms detect temperature changes?

Answer 18

Peripheral temperature receptors detect changes in surface temp

Temp receptors in hypothalamus detect temp in blood

Question 19

What is vasodilation?

Answer 19

Arterioles close to surface of the skin dilate when the temp rises
Vessels that provide a connection between arterioles and venues constrict
Forces blood between capillary networks
Skin flushes and cools as a result of increased radiation
If skin pressed against cold surfaces, cooling results from conduction

Question 20

What causes increased sweating in endotherms?

Answer 20

As core temp increases- sweat increases- across surface of skin

As sweat evaporates from the skin, heat is lost, cooling blood below the surface.

Question 21

How do endotherms cool down from reducing insulating effect of hair/feathers

Answer 21

As body temp increase, erector pili muscles in skin relax- hair flattens to skin which avoids trapping of insulating layer of skin

Large SA:V ratios- maximum cooling, pale fur to reflect radiation

Question 22

How do endotherms warm up through vasoconstriction

Answer 22

Arterioles near surface of skin constrict. Arteriovenous shunt vessels dilate- so little blood flows through capillary networks near the skin.

Skin is pale and little radiation and warm blood kept below surface

Question 23

How does decreased sweating keep the body warm?

Answer 23

As core temp falls, rate of sweating decreases. Reduces cooling by evaporation of water from skin surface-

Question 23

How does raising body hair increase heating

Answer 23

As body temp falls, erector pili muscles in skin contract- pulling hairs erect

Traps an insulating layer of air and reduces calling

Question 24

How does shivering prevent heat loss?

Answer 24

Metabolic heat from exothermic reactions warm up body

Contracting and relaxing of body

Question 25

What are the two control centres in thermoregulation?

Answer 25

Heat loss centre
Heat gain centre

Question 26

What is the heat loss centre?

Answer 26

Activated when temp of blood flowing through hypothalamus increases
Sends impulses through autonomic motor neurones to effectors in skin and muscles- triggering responses