5.1.1 Communication and homeostasis

Question 1

homeostasis definition

Answer 1

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

Question 2

effector definition

Answer 2

cell, tissue or organ that brings about a response

Question 3

stimulus definition

Answer 3

change in environment, causing a response

Question 4

response definition

Answer 4

change in behaviour/physiology as a result of stimulus

Question 5

internal environment definition

Answer 5

conditions inside organism

Question 6

external environment definition

Answer 6

conditions outside organism

Question 7

cell signalling definition

Answer 7

communication between cells to help them work together to co-ordinate their actions

Question 8

positive feedback definition

Answer 8

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

Question 9

negative feedback definition

Answer 9

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

Question 10

conditions in organisms that need to be maintained

Answer 10

suitable temperature
suitable pH
free of toxins and excess inhibitors
aqueous environment (substrates and products in solution)

Question 11

good communication system features

Answer 11

covers whole body
enable cells to communicate with each other
enable specific communication 
rapid communication 
short+long term response

Question 12

neuronal system features

Answer 12

short-term
quick
electrical impulses carried by neurotransmitters across synapses
very specific effect

Question 13

hormonal system features

Answer 13

long term
slow
hormones carried in blood
specific to target cells but have general widespread effect

Question 14

homeostasis examples

Answer 14

body temp.
body glucose + salt conc.
water potential in blood
blood pressure
CO2 conc.

Question 15

mechanism for responding to stimulus

Answer 15

stimulus -> receptor -> communication pathway (neuronal or hormonal) -> effector -> response

Question 16

feedback in general

Answer 16

effectors brings about response, changing conditions inside body
receptor detects change and input/response pathway changes

Question 17

negative feedback conditions

Answer 17

change in external/internal environment detectable
change signalled to other cells
effective response reversing the change is present

Question 18

negative feedback mechanism

Answer 18

conditions change away from optimum
receptor detects change
(input)
comm. system informs effector
(output)
effector reacts to reverse change
return to optimum condition
optimum conditions reached and repeat cycle

Question 19

positive feedback facts

Answer 19

tends to be harmful

sometimes necessary e.g. pregnancy and activity of neurones

Question 20

positive feedback mechanism

Answer 20

change away from optimum
receptor detects change
(input)
comm. system informs effector
(output)
effector reacts to increase change

Question 21

how having a number of steps in the signalling pathway enables a small number of hormone molecules to rapidly cause large effects

Answer 21

one molecule causes production/activation of many other molecules
multiplying effect is repeated at every step