Communication and Homeostasis

Question 1

what conditions need to be maintained within cells?

Answer 1

temperature, pH, an aqueous environment and freedom from toxins and excess inhibitors

Question 2

what does a good communication system do?

Answer 2

cover the whole body, enable cells to communicate with eachother, enable specific and rapid communication, and enable short and long term responses

Question 3

what is cell signalling?

Answer 3

the process in which one cell will release a chemical that is detected by another cell, the second cell will then respond to this signal

Question 4

what is the neuronal system?

Answer 4

an interconnected network of neurons that signal to each other across synapse junctions. The neurons can conduct a signal very quickly and enable rapid responses to stimuli that may be changing very quickly

Question 5

what is the hormonal system?

Answer 5

a system that uses blood to transport its signals. Cells in an endocrine organ release the signal (a hormone) directly into the blood. The hormone is transported throughout the body, but is only recognised by a specific target cell. The hormonal system enables longer-term responses to be coordinated

Question 6

what is homeostasis?

Answer 6

maintaining a constant internal environment despite changes in external and internal factors

Question 7

what aspects can be maintained by homeostasis?

Answer 7

body temp, blood glucose, blood salt concentration, water potential of the blood, blood pressure and carbon dioxide cocentration

Question 8

what is negative feedback?

Answer 8

the mechanism that reverses a change, bringing the system back towards the optimum

Question 9

what processes must occur for negative feedback to work?

Answer 9

a change to the internal environment must be detected, the change must be signalled to other cells and there must be an effective response that reverses the change

Question 10

what is positive feedback?

Answer 10

increasing the original change away from the optimum

Question 11

what is an example of positive feedback?

Answer 11

During the dilation of the cervix. As the cervix begins to stretch it causes the posterior pituitary gland to secrete the hormone oxytocin. The birth ends the production of oxytocin

Question 12

what is an ectotherm?

Answer 12

an organism that is not able to control body temperature as effectively as they rely on external sources of heat. Using various behavioural mechanisms some can control temperature in extreme conditions

Question 13

what do ectotherms do if they are not warm enough?

Answer 13

Moving into a sunny area
Lie on a warm surface
Expose a larger surface area to the sun

Question 14

what do ectotherms do if they are too warm?

Answer 14

Moving out of the sun
Move underground
Reduce the surface area exposed to the sun

Question 15

what are advantages of ectotherms?

Answer 15

They do not use up energy to keep warm so:
Less of their food is used in respiration
More energy and nutrients gained from food can be used for growth
They need to find less food
Can survive for long periods without food

Question 16

What are disadvantages of ectotherms?

Answer 16

Less active in cooler temperatures
At risk from predators while they are unable to escape
Can’t take advantage of available food when they are cold

Question 17

what is an endotherm?

Answer 17

organisms that control their body temperature within very strict limits, they use a variety of mechanisms to control body temperature and are largely independent of external temperatures

Question 18

what are responses of the skin if an endotherm is too hot?

Answer 18

Sweat glands secrete fluid, as it evaporates it uses heat from the blood as the latent heat of vaporisation

Hairs and feathers lie flat to reduce insulation and allow greater heat loss

Vasodilation of arterioles and precapillary sphincters directs blood to the skin surface so more heat can be radiated away

Question 19

what are responses of the skin if an endotherm is too cold?

Answer 19

Less sweat is secreted, so less evaporation means less heat lost

Hairs and feathers stand erect to trap air that insulates the body

Vasoconstriction of arterioles and precapillary sphincters leading to the skin’s surface, blood is diverted away from the surface of the skin and less heat is lost

Question 20

what is the response of the gaseous exchange system if an endotherm is too hot?

Answer 20

Panting can increase evaporation of water from the surface of the lungs and airways. Evaporation uses heat from the blood as the latent heat for vaporisation

Question 21

what is the response of the gaseous exchange system if an endotherm is too cold?

Answer 21

Less panting, so less heat lost

Question 22

what is the response of the liver if an endotherm is too hot?

Answer 22

Less respiration takes place so less heat is released

Question 23

what is the response of the liver if an endotherm is too cold?

Answer 23

Increased respiration in the liver cells mean that more energy from food is converted to heat

Question 24

what is the response of the skeletal muscles if an endotherm is too hot?

Answer 24

Fewer contraction mean less heat is released

Question 25

what is the response of the skeletal muscles if an endotherm is too cold?

Answer 25

Spontaneous muscle contractions (shivering) releases heat

Question 26

what is the response of the blood vessels if an endotherm is too hot?

Answer 26

Dilation to direct blood to the extremities so that more heat can be lost

Question 27

what is the response of the blood vessels if an endotherm is too cold?

Answer 27

Constriction to limit blood flow to the extremities so that the blood isn’t cooled - can lead to frostbite

Question 28

what are advantages of being an endotherm?

Answer 28

Maintain a fairly constant body temperature
Remain active even when external temperatures are low (can escape predators or catch prey)
Inhabit colder parts of the planet

Question 29

what are the disadvantages of being an endotherm?

Answer 29

Use a significant part of their energy intake to maintain body temperature
Need more food
May overheat in hot weather

Question 30

how is temperature regulated?

Answer 30

Temperature receptors in the hypothalamus detect change and then send an impulse to reverse the change

Question 31

what happens if the core temperature is too low?

Answer 31

the hypothalamus will bring about:
Changes in the skin to reduce heat loss
Release of heat through extra muscular contraction
Increased metabolism in order to release more heat from exergonic reaction

Question 32

what is the role of peripheral temperature receptors?

Answer 32

they monitor the temperature in the extremities as this can help initiate a faster response in the thermoregulatory centre in the hypothalamus