5.1.1- Homeostasis and Communication

Question 1

what are the 4 needs for communication systems in multicellular organisms?

Answer 1

-stimulus and response, so that organisms respond to changes in external and internal environments.
-coordination, organisms must coordinate the function of different cells/systems to operate effectively
-cell signalling, cells communicate with eachother, using nervous and hormonal systems
-keeping cells alive/survival, need to maintain set of conditions so work when there are changes.

Question 2

why are multicellular organisms more efficient?

Answer 2

they have differentiated cells, which are specialised to perform particular functions and can form tissues and organs.

Question 3

what are the 5 points that all good communication systems will have?

Answer 3

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

Question 4

what is an example of the way animals coordinate?

Answer 4

when the muscles respire, they coordinate with red blood cells so that the oxygen that is being carried in the blood can reach the muscle for respiration.

Question 5

what are two example of the way plants coordinate?

Answer 5

1-flowering plants coordinate with pollenators by having chemicals change at different times of the day, helping the plant to flower, chemical communication, plant hormones
2-plant stem moves towards the light due to hormones

Question 6

what are example of internal changes that organisms must respond to?

Answer 6

-blood glucose concentration
-internal temperature
-cell pH level
-water potential
-blood pressure
-blood salt concentration
-carbon dioxide concentration

Question 7

what are some examples of external changes that organisms must respond to?

Answer 7

-temperature
-humidity
-light intensity
-sudden sound

Question 8

explain why communication systems must cover the whole body?

Answer 8

so actions of all cells/tissues can coordinate

Question 9

explain why communication systems must enable specific communication?

Answer 9

so cells that are needed will respond to signal

Question 10

explain why communication systems must enable rapid communication?

Answer 10

to enable response to rapid changes in the environment.

Question 11

explain why communication systems must enable short/long term responses?

Answer 11

so responses can be suited to the environmental change, short=short response, long=long response

Question 12

what is cell signalling?

Answer 12

the communication and coordination of cells using signals
-many molecules/internal processes within the cell acts as signals.

Question 13

how do cells detect signals?

Answer 13

-cells detect internal/external signals to carry out life processes.
-cells have receptors on the membranes
-the secreting cell releases a chemical, while the target cell detects this and responds to it.

Question 14

what are two systems that work by cell signalling?

Answer 14

-neuronal system
-hormonal system

Question 15

why is cell signalling important?

Answer 15

it allows multicellular organisms to control and coordinate their bodies and to respond to their environments

Question 16

what is Paracrine signalling.

Answer 16

signalling between cells that are close together

Question 17

what is Endocrine signalling?

Answer 17

signalling between cells that are far apart, which involves the signalling molecule being transported in the circulatory system

Question 18

what type of molecule are the receptors on the cell membrane

Answer 18

-proteins
-glycoproteins (protein + glycoprotein)

Question 19

what are the basic stages of cell signalling?

Answer 19

-stimulus is received by a receptor cell
-stimulus is converted to a signal (nearly always a chemical) that can be passed on (transduction)
-signal is transmitted to a target cell (effector) that can detect it (via receptors in its cell membrane-an appropriate response is made

Question 20

what is homeostasis?

Answer 20

the maintenance of a constant internal environment, despite changes in the surroundings.

Question 21

what is a receptor?

Answer 21

an extristic glycoprotein that binds to chemical signals, and trigger a response

Question 22

what is an effector?

Answer 22

a muscle/gland that carries out a body’s response to a stimulus.

Question 23

what are some examples of receptors?

Answer 23

-sensory receptors in the skin
eg-thermo

Question 24

what is negative feedback?

Answer 24

when any change away from the optimum conditions is reversed back towards the normal optimum

Question 25

what is positive feedback?

Answer 25

if change from the optimum is increased, it continues to increase.

Question 26

what are the 10 points of the negative feedback mechanism?

Answer 26

1-receptors detect the stimulus
2-input is passed onto the coordination centre
3-output is sent to the effectors
4-effectors reverse the initial change in the conditions
5-system moves closer to the optimum
6-stimulus is reduced
7-receptors detect the reduction in the stimulus
8-input is reduced
9-output is also reduced, effectors reduce their activity
10- response is eventually reduced.

Question 27

what are the 4 mechanisms of positive feedback?

Answer 27

1- change away from the optimum
2-receptor detects change
3-communication system informs effector
4-effector reacts to increase change

Question 28

what are 2 examples of positive feedback?

Answer 28

-hypothermia
-child birth

Question 29

explain hypothermia?

Answer 29

-the cold reduces molecule’s kinetic energy, so metabolic reactions slow down
-respiration slows down
-slowed exergonic reactions (releases heat)
-we get colder

Question 30

expalin child birth and oxytocin?

Answer 30

-head of fetus pushes on cervix
-this stimulates pressure receptors that means that nerve impulses are transmitted to the brain
-brain stimulates the pituitary gland to secrete oxytocin
-oxytocin is carried in the bloodstream to the uterus
-oxytocin stimulates uterine contractions and pushes fetus towards the cervix
-this all stops when the baby is born.

Question 31

what is an ectotherms?

Answer 31

animals that use their surroundings to warm their bodies up, their core temperature is very dependent on the environment

Question 32

what is an endotherm?

Answer 32

animals that rely on their metabolic processes to warm up their bodies and maintain their core temperature.

Question 33

what are the examples of ectotherms?

Answer 33

reptiles, insects, fish and amphibians

Question 34

what are the examples of endotherms?

Answer 34

mammals and birds

Question 35

what is the response of ectotherms when their is an external temperature change?

Answer 35

behavioural responses

Question 36

what is the behavioural response of a horned lizard?

Answer 36

can change it’s shape by expanding/contracting it’s ribcage, which increases the SA exposed to the sun, so more heat is absorbed

Question 37

what is the behavioural response of a snake?

Answer 37

basks in the sun, which allows heat energy to be absorbed.

Question 38

what is the behavioural response of a lizard?

Answer 38

use of burrows/crevices between rocks, as this is used as protection from the sun during the day, but at night it is warmer than outside

Question 39

what is the behavioural response of a locust?

Answer 39

-increases rate of breathing/depth of breathing when hot, which allows more evaporation of water, cooling the body
-sits in the sun in early morning, sitting side on, which allows more heat energy to be transferred.

Question 40

what is the advantages of ectotherms?

Answer 40

they dont rely on energy to keep warm, so they need less food, meaning the energy and nutrients gained from food can be used for growth rather than respiration

Question 41

what is the disadvantage of ectotherms?

Answer 41

they are less active in cooler temperatures so they are more at risk from predators, as they are unable to escape and cannot take advantage of food that is available.

Question 42

what are the 3 advantages of endotherms?

Answer 42

-don’t rely on external temp, so can still have a constant body themp
-remain active even in cold, so can hunt/escape
-can inhabit colder environments

Question 43

what are the 3 disadvantages of endotherms?

Answer 43

-will need lots of food to gain energy for processes
-can overheat in hot weather
-less energy is used for growth

Question 44

how does temperature regulation occur in endotherms?

Answer 44

-peripheral thermoreceptors in skin
-hypothalamus in brain contains thermoregulatory centre, which detects changes, sending signals to reverse this
–behavioural responses and physiological responses

Question 45

what is the advantage of having receptors in the thermonregulatory centre and peripheral receptors in the skin?

Answer 45

the combination of the two gives the body increased sensitvity

Question 46

what are some examples of physiological responses of endotherms?

Answer 46

-sweating
-mouth open/panting
-erector pili muscles, hair on skin
-vasodilation and vasoconstriction
-rate of metabolism/respiration
-muscle contractions and shivering

Question 47

what happens when the blood glucose level is too high?

Answer 47

-receptors detect this increase
-beta cells in pancreas release insulin
-increased uptake of glucose by effector/liver, which enters through glucose transport proteins
-glucose is converted into glycogen
-leads to increased respiration (increased use of glucose)

Question 48

what happens when the blood glucose levels are too low?

Answer 48

-alpha cells in pancreas release glucagon
-increased conversion of glycogen to glucose
-conversion of other compounds to glucose (eg- amino acids)
-glucose leaves cell by facilitated diffusion