5.1 Communication and Homeostasis

Question 1

what do all living things need to maintain

Answer 1

-a suitable temperature
-a suitable PH
-an aqueous environment that keeps the substrates and products in solution
-freedom from toxins and excess inhibitors

Question 2

what is the environment of cells

Answer 2

they are protected by epithelial tissues and organs such as skin or bark. Internal cells and tissues are bathed in tissue fluid

Question 3

how do activities of the cells alter their own environment

Answer 3

as cells undergo their various metabolic activities, they use up substrates and create new products. Some of these compounds may be unwanted or toxic. They move out of cells into the tissue fluid.

Question 4

why is it Important that concentrations of waste products and other substances in the blood are monitored closely

Answer 4

it ensures that the body does not excrete too much of any useful substance but removes enough of the waste products to maintain good health. It ensures that the cells in the body are supplied with the substrates they need

Question 5

why is a multicellular organism more efficient than a single celled organism

Answer 5

its cells are differentiated- they are specialised to perform particular functions. groups of these cells form tissues and organs. A good communication system is required to ensure that different parts of the body work together effectively

Question 6

what will a good communication system do

Answer 6

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

Question 7

how does cell signalling work

Answer 7

one cell will release a chemical that is detected by another cell and the second cell will respond to the signal released by the first cell

Question 8

define neuronal system

Answer 8

and interconnected network of neurones that signal to eachother across synapse junctions. It conducts signals very quickly and enables rapid responses to stimuli

Question 9

define hormonal system

Answer 9

a system that used the blood to transport its signals. Cells in an endocrine organ release the signal directly into the blood and the hormone is transported to a specific target cell. It enables longer term responses to be coordinated

Question 10

define aspects maintained by homeostasis

Answer 10

-body temp
-blood glucose conc
-blood salt conc
-water potential of the blood
-blood pressure
-CO2 conc

Question 11

what is the standard response pathway

Answer 11

stimulus
receptor
communication pathway(cell signalling)
effector
response

Question 12

define sensory receptor

Answer 12

cells/ sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potential

Question 13

define communication system

Answer 13

system which signals between cells. is is used to transmit a message from receptor cells to effector cells via a coordination centre

Question 14

define effector

Answer 14

a cell, tissue or organ that brings about a response

Question 15

define homeostasis

Answer 15

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

Question 16

define negative feedback

Answer 16

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

Question 17

what processes must occur for negative feedback to work?

Answer 17

1. a change to the internal environment must be detected
   2.the change must be signalled to other cells
2. there must be an effective response that reverses the change in conditions

Question 18

define postitive feedback

Answer 18

the mechanism that increases a change, taking the system further away from the optimum

Question 19

why must body temperature be controlled

Answer 19

Cell activities depend upon enzyme activity. All enzymes have an optimum temperature. Too low and they work too slowly, too high and they become denatured.

Question 20

define ectotherm

Answer 20

an organism that relies on external sources of heat to maintain body temp

Question 21

define endotherm

Answer 21

an organism that uses heat from metabolic reactions to maintain body temp

Question 22

when ectotherms are not warm enough, they try to absorb more heat from the environment. What may they do to do this?

Answer 22

-move into a sunny area
-lie on a warm surface
-expose a larger surface area to the sun

Question 23

what may ectotherms do if they re too hot

Answer 23

-move out of the sun
-move underground
-reduce the body surface exposed to the sun

Question 24

what behavioural adaptations do snakes have

Answer 24

they bask in the sun and can often be found lying on an exposed path beside vegetation. this absorbs heat directly from the sun

Question 25

what behavioural adaptations do lizards have

Answer 25

many lizards use burrows or crevices between rocks. they hide in them during the hottest part of the day and coolest part of the night. They tend to have a more stable temp than the air. In the hottest part of the day, it will be cooler in the burrow and at the coolest time, it will be warmer in it

Question 26

what behavioural adaptations do horned lizards have

Answer 26

it can change its shape by expanding or contracting its ribcage. They can increase the surface area exposed to the sun so more heat can be absorbed

Question 27

advantages of ectothermy

Answer 27

-less of their food is used in respiration
-more of the energy and nutrients gained from food can be converted to growth
-they need to find less food
-they can survive for long periods without food

Question 28

disadvantages of ectothermy

Answer 28

-less active in cooler temp
-at risk from predators when they are cold and unable to escape
-cannot take advantage of food that is available while they are cold

Question 29

define the hypothalamus

Answer 29

the part of the brain that coordinates homeostatic responses

Question 30

many chemical reactions in the body are exergonic. what does this mean

Answer 30

they release energy in the form of heat

Question 31

what is the behaviour or endothermic organisms when they are too hot

Answer 31

-hide away from sun in shade or burrows
-orientate body to reduce surface area exposed to sun
-remain inaction and spread limbs out to enable greater heat loss
-wet skin to use evaporation to help cool the body

Question 32

what is the behaviour or endothermic organisms when they are too cold

Answer 32

-lie in the sun
-orientate body towards sun to increase surface area exposed
-move about to generate heat in the muscles
-roll into a ball shape to reduce surface area and heat loss
-remain dry

Question 33

how does the skin respond if the body is too hot

Answer 33

-sweat glands secrete fluid onto the skin surface
-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 from the body

Question 34

how does the skin respond if the body is too cold

Answer 34

-less sweat is secreted so less evaporation so less heat is lost
-hairs and feathers stand erect to trap air which insulates the body
-vasoconstriction of arterioles and precapillary sphincters leading to skin surface. blood is diverted away from the surface of the skin and less heat is lost

Question 35

how does the gaseous exchange system respond if the body is too hot

Answer 35

some animals pant, increasing evaporation of water from the surface of the lungs and airways. Evaporation uses heat from the blood as the latent heat of vaporisation

Question 36

how does the gaseous exchange system respond if the body is too cold

Answer 36

less panting so less heat is lost

Question 37

how does the liver respond if the body is too hot

Answer 37

less respiration takes place so less heat is released

Question 38

how does the liver respond if the body is too cold

Answer 38

increased respiration in the liver cells means that more energy from food is converted to heat

Question 39

how does the skeletal muscles respond if the body is too hot

Answer 39

fewer contractions mean that less heat is released

Question 40

how does the skeletal muscles respond if the body is too cold

Answer 40

spontaneous muscle contractions release heat (shivering)

Question 41

how do the blood vessels respond if the body is too hot

Answer 41

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

Question 42

how do the blood vessels respond if the body is too cold

Answer 42

constriction to limit blood flow to the extremities so that blood is not cooled too much- this can lead to frostbite in extreme conditions

Question 43

advantages of endothermy

Answer 43

-can maintain a fairly constant body temp whatever the temp is externally
-they can remain active even when external temperatures are low, which means they can take advantage of prey that may be available or escape from potential predators
-inhabit colder parts of the planet

Question 44

disadvantages of endothermy

Answer 44

-use a significant part of their energy intake to maintain body temp in the cold
-need more food
-use for growth a lower proportion of the energy and nutrients gained from food
-may overheat in hot weather

Question 45

what is the importance of maintaining a core body temperature

Answer 45

core temp changes alter the temp of the blood. this is detected by temp receptors in the hypothalamus. It then sends out imposes to cause different responses that will reverse the change.

Question 46

what will the hypothalamus bring about if the core temp is too low

Answer 46

-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 reactions

Question 47

what’s the role of a thermoregulatory centre

Answer 47

monitor blood temperatures and detect changes in the core body temp

Question 48

when will the brain initiate behavioural mechanisms

Answer 48

if the thermoregulatory centre signals to the brain that the external environment is very cold or very hot

Question 49

what is the role of peripheral temperature receptors

Answer 49

monitor the temperature of the extremities