5.1.1 Communication and homeostasis

Question 1

What is the need for communication systems in plants so they respond to external environment?

Answer 1

avoid herbivory;
grow towards sunlight/water;

Question 2

Why do animals need to respond to their environment?

Answer 2

to catch prey;
avoid predation;

Question 3

What is the need for communication systems in multicellular organisms?

Answer 3

respond to abiotic and biotic factors;

Question 4

Why do plants and animals need to respond to their internal environment?

Answer 4

enzyme controlled reactions involved in metabolic reactions;

Question 5

What is a transducer?

Answer 5

a receptor that converts one type of energy into another type of energy

Question 6

What is the reflex arc?

Answer 6

receptors attached to sensory neurone > CNS where there are relay neurones > brain coordinates a response > motor neurone > effector (muscle or gland)

Question 7

What are effectors?

Answer 7

muscles or glands that bring a response from a stimulus and produce an effect

Question 8

What are the two types of hormones?

Answer 8

peptide hormones;
lipid based hormones;

Question 9

How do lipid based hormones cause an effect to a cell?

Answer 9

as it can diffuse through the phospholipid bilayer;
hormone binds to a receptor in the cytoplasm forming a receptor hormone complex;
RHC enters the nucleus and triggers gene transcription;
transcribed mRNA is translated and proteins are produced to alter cells activity

Question 10

How do peptide hormones cause an effect to a cell?

Answer 10

they use 1st messengers and a 2nd messenger response;

first messenger is the hormone and it binds to the receptor as it is specific and complementary;
this activates the enzyme adenyl cyclase;
the enzyme activates the 2nd messenger cAMP;
cAMP triggers a response inside the cell;

Question 11

What is a receptor?

Answer 11

detects a change in the body

Question 12

What is homeostasis?

Answer 12

maintaining a relatively stable internal environment ;
within narrow limits;
even though the environment is changes

Question 13

What factors need to be kept constant in the body?

Answer 13

core body temperature
blood pH
blood glucose conc
water potential of blood

Question 14

Why does core body temperature need to be controlled by homeostasis?

Answer 14

enzymes/other proteins are sensitive to temperature changes;
they function best at their optimum temperature;
at low temperatures they don’t work efficiently and at high temperatures they denature;

Question 15

Why does blood pH need to be controlled by homeostasis?

Answer 15

enzymes/other proteins are sensitive to pH;
they function best at their optimum pH;
away from optimum, enzymes don’t work efficiently/denature

Question 16

Why does blood glucose concentration need to be maintained by homeostasis?

Answer 16

glucose is a respiratory substrate;
cells need a constant supply;
needed to make ATP used in muscle contraction via aerobic respiration;
keeping blood glucose conc constant ensures a constant water potential;

Question 17

What is negative feedback?

Answer 17

the effector causes a change that brings the environment back to ‘normal’ conditions

Question 18

What is positive feedback?

Answer 18

the situation is amplified until there is a change brought about

Question 19

What are endotherms?

Answer 19

regulate their own body temperature

Question 20

What are ectotherms?

Answer 20

doesn’t regulate their own body temperatare as effectively;
as they rely on external sources

Question 21

How does the hypothalamus regulate body temperature?

Answer 21

there is a thermoregulatory centre in the hypothalamus;
contains thermoreceptors which monitor temp of blood;
sends messages to parts of the body to increase/decrease

Question 22

What occurs to blood vessels when the body temperature is too high/low?

Answer 22

vasoconstriction; blood vessels narrow near the surface of the skin; more blood travels through shunt vessel; less heat loss through epidermis

vasodilation; the shunt vessel constricts more blood rushes towards the surface of the skin; more heat loss through epidermis

Question 23

What occurs to the hairs on the skin when body temp is too high/low?

Answer 23

hair erector muscle;
contracts or relaxes
stand on end;
creates insulating layer of air

Question 23

How is a temperature increase or decrease detected by the skin?

Answer 23

detected by peripheral temperature receptors on the skin

Question 24

What is the neuronal impact of increased temperature?

Answer 24

1) skeletal muscles prevent shivering
2) vasodilation
3) relaxation of hair erector muscle
4) sweating

Question 25

What is the physiological response to an increase in core body temperature?

Answer 25

decreased production of adrenaline and thyroxine;
causes decrease in metabolism;
decrease in heat production as a by product of aerobic respiration;

Question 26

What is the neuronal impact for a decrease in core body temperature?

Answer 26

1) skeletal muscles contract = shivering
2) vasoconstriction
3) hair erector muscles contract
4) no sweating

Question 27

What is the physiological response to low core body temperature?

Answer 27

increased production of adrenaline and thyroxine;
increase in metabolism;
increased heat production as a by product of aerobic respiration

Question 28

What are the behavioural responses in ectotherms to control body temperature?

Answer 28

cold:
- basking in hot areas
- expose a larger SA of their body to the sun

hot:
- move out of the sun
- move underground/burrow

Question 29

What are the advantages of ectotherms?

Answer 29

less food used in respiration

less food needs to be found

can survive extended periods without food

more energy from food goes into growth

Question 30

What are the disadvantages of ecotherms?

Answer 30

less active when colder

risk of predation when cold

unable to tale advantaged of food available when cold

restricted range of habitats

Question 31

How does sweating cause a reduction in body temperature?

Answer 31

sweat is secreted from the sweat glands on the skins surface;
heat is supplied by the body and is used for evaporation;
as water has a high latent heat of vaporisation, a lot of heat energy is transferred from the body during evaporation leading to a reduction in body temperature