communication and homeostasis

Question 1

what are the two types of cell signalling

Answer 1

neural and chemical

Question 2

what is cell signalling

Answer 2

The way cells adjacent or distant communicate with each other is by cell signalling there are two communication systems (neural and chemical)

Question 3

what is an example of cell signalling from communicable diseases?

Answer 3

• in the humoral response, t helper cells bind to specific APC’s (clonal selection) before clonal expansion is triggered by cytokine, interleukin 1.
• T helper cells then bind to specific B lymphocytes, stimulating plasma cell production by cytokine interleukin 2.

Question 4

what is the nervous system

Answer 4

interconnected network of neurones that signal to each other across synapses via neurotransmitters.

Question 5

what are neurones?

Answer 5

neurones are specialised cells, which can conduct electrical impulses very quickly to enable rapid response. e.g. reflexes.

Question 6

what is the hormonal system

Answer 6

cell within the endocrine gland release hormones directly into the blood.

Question 7

what is a hormone

Answer 7

it is a chemical messenger, which has a specific shape which is recognized by specific target cells.

Question 8

what has longer responses, the hormonal or nervous system

Answer 8

the hormonal system

Question 9

compare the nervous system to the hormonal system

Question 10

outline 3 roles, of glycoproteins in membranes

Answer 10

• antigen for cell recognition
• binding site for hormones/neurotransmitters
• receptors for cell signalling

Question 11

give 5 examples of internal environment

Answer 11

• blood pH
• internal body temperature
• blood water potential
• blood glucose levels
• blood pressure

Question 12

give 5 examples of external environment

Answer 12

• external temperature
• humidity
• atmospheric oxygen levels
• pressure on the skin -> pain?
• sudden loud bang

Question 13

what is homeostasis

Answer 13

the maintenance of a constant internal environment, around a set point, despite environmental changes (interna and external)

Question 14

what are examples of homeostasis

Answer 14

• thermoregulation -> ensure optimum temp for enzymes
• blood glucose concentration -> important for respiration + maintaining cells water potential
• water potential of the blood
• blood pressure -> to high and it could damage arteries

Question 15

what is feedback

Answer 15

when effectors bring about a response they change the condition of the body and this new condition will be detected by receptors (i.e.. the input has changed) which in turn will affect the response)

Question 16

what is positive feedback

Answer 16

• the mechanism that increases a change, taking the system further way from the optimum
• tends to be harmful
• not involved in homeostasis

Question 17

why is it necessary to control body temperature?

Answer 17

to ensure optimum temperature for enzyme activity ^ in temp, causes an increase in the number of successful collisions, -> to high of a temp means enzymes denature and tertiary structure changes (active site changes shape)

Question 18

what is the key to a good communication

Answer 18

• cover the whole body so the action of all cells and tissues can be coordinated
• enable localised communication between cells
• enable long distance communication between cells
• enable specific communication -> targets specific cell to respond only
• be rapid -> allowing fast response to rapid changes
• enable long term responses -> hormones
• enable short term responses -> neuronal

Question 19

give an example of positive feedback

Answer 19

• blood clotting -> platelets attract more platelets which accelerates clotting.

Question 20

what happens when we increase body temperature

Answer 20

hyperthermia - respiratory enzymes denature and organ failure occurs -> (heat + brain have very high energy demands)

Question 21

what happens when we decrease body temperature

Answer 21

hypothermia -positive feedback loop, i.e. as temp decreases rate of reaction ^

Question 22

what is core temperature

Answer 22

• operating temperature inside of the body

Question 23

what is peripheral temperature

Answer 23

• the temperature of the skin -> more variable, as influenced by the environment

Question 24

what are the key things to remember about endotherms (warm blooded)

Answer 24

• use heat energy from metabolic reactions, to maintain body temp -> mammals have a high metabolic rate.
• controls body temperature, within strict limits (set point)
• uses a variety of methods to control temp, e.g. behavioural + physiological
• activity level is largely independent of external temperature

Question 25

what are the key things to remember about ectotherms (cold blooded)

Answer 25

- external sources of heat, to maintain temperature - unable to control internal temperature, and cannot increases there metabolism accordingly. - body temperature fluctuates with external temperature - activity level, depends on external temperature - more active when it's warmer - likely to exploit a much narrower ecological niche, i.e. have a more specific role in an ecosystem.

Question 26

what will ectotherms do, if they are too cold

Answer 26

- move to a sunny area, to bask in the sun - lie on warm surfaces - expose more of their body to the sun, to warm up - move around, to generate some heat energy -> contraction of muscles.

Question 27

what will ectotherms do if they are too hot

Answer 27

- move out of the sun (seek shade) - move under - ground (burrow) - decrease the surface area exposed to the sun - increase the rate and depth of breathing, to loose water vapour by evaporation

Question 28

suggest why aquatic ectotherms, have relatively few problems in maintaining a stable body temperature

Answer 28

- water has a high specific heat capacity, this means that a large amount of energy is needed in order to raise the temperature of the water by 1 degree, therefore, the temperature remains relatively stable at all times.

Question 29

what is the role of the hypothalamus - thermoregulatory centre

Answer 29

- monitors blood temperature flowing through it via thermoreceptors. - receives impulses from the thermoreceptors in the skin - send impulses, via motor neurones to the sweat glands, and to the muscle in the arterial walls + to the skeletal muscles and hair erector muscles.

Question 30

what is the role of the sympathetic nerve

Answer 30

causes the release of sweat. (autonomic nervous system)

Question 31

shunt vessels, allow blood to bypass capillaries in the surface of the skin ->

Answer 31

+ reduce blood flow through the capillaries to reduce heat loss if you to hot, vasodilation of the arterioles increases blood flow in order to increase the amount of heat loss.

Question 32

what is the role of the thermoregulatory centre in the hypothalamus

Answer 32

to sense the temperature of blood, flowing through the hypothalamus.

Question 33

what is vasodilation

Answer 33

the widening of the blood vessels in order to increase blood flow

Question 34

what is vasoconstriction

Answer 34

the narrowing of the blood vessels in order to decrease blood flow

Question 35

describe and explain two physiological mechanism that would be initiated, following a decrease in core body temperature.

Answer 35

- vasoconstriction of arterioles, to reduce heat loss from surface - shivering to generate heat from respiration.

Question 36

suggest why the ear provides a more accurate measurement of body temperature than the skins surface.

Answer 36

due to sharing its blood supply with the thermoregulatory system, thus meaning that the reading will be much closer to that of the thermoregulatory system, than that of the skin.

Question 37

what are the general features of a negative feedback mechanism

Answer 37

to help maintain the internal environment around a set point, furthermore receptors, detect change from that set point and effectors produce change.

Question 38

what are the symptoms of hypothermia

Answer 38

- pale skin + cold - shivering violently - slow shallow breathing

Question 39

when can hypothermia be useful

Answer 39

- gentle rewarming - heart surgery

Question 40

why would it be bad to give someone with hypothermia an alcoholic drink

Answer 40

due to alcohol leading to the vasodilation of blood vessels, which in turn will lead to further heat loss thus exacerbating the problem.