Unit 2 Topic 1: Homeostasis

Question 1

Homeostasis

Answer 1

the maintenance of relatively stable internal conditions within narrow tolerance limits via negative feedback mechanism.

Question 2

receptors

Answer 2

thermoreceptor - temperature
nociceptor - pain
photo - light
mechano - pressure
chemo - chemicals

Question 3

effectors

Answer 3

muscles - contract
glands: endo and exocrine

Question 4

metabolism

Answer 4

sum of the net chemical processes in the body

Question 5

changes in metabolic activity and catalytic activity

Answer 5

1. enzymes denature from metabolic heat
2. decreased means dereased ROR

Question 6

CNS

Answer 6

brain
spinal chord
interconnecting neurons

Question 7

PNS

Answer 7

the rest of the body, motor and sensory neurons

Question 8

myelin sheath

Answer 8

1. insulates and protects signa;
2. speeds up transmission of signal

Question 9

Nerve impulse transmission within neuron

Answer 9

resting potential:
more negative inside, 2K in and 3Na out

action potential:
K gates close, Na gates open, influx of ions, becomes more negative on outside.

repolarisation:
k gates open again
Na gates close
active pumping begins again

Question 10

between neurons

Answer 10

actional potential arrives at the presynaptic terminal of the neuron where synaptic vessels with the neurotransmitters fuse with the terminal and diffuse into the synaptic cleft, here they bind to the receptors on the postsynaptic neurpn where the signal changes from chemical to electrical (signal transduction).

Question 11

hormones

Answer 11

are chemical messengers released from glands that prompt a response from specific cells.

they only act upon cells with the complementary receptor.

Question 12

water soluble hormones

Answer 12

binds extracellularly, from amino acids.
1. ion channel receptor
2. G protein couples receptor
3. tyrosine kinase

Question 13

fat soluble hormones

Answer 13

bind intracellularly, drived from glycerol and fatty acids

Question 14

how does receptor binding activate signal transduction

Answer 14

1. binding
2. activation
3. signal transduction
4. amplification (second messengers)
5. changes in cellular activity
6. negative feedback

Question 15

heat loss and gains

Answer 15

endotherms: regulate internal temp
exotherms: internal temp is affected by environmental conditions

Question 16

structural features of thermoregulation

Answer 16

1. insulation
   more distance for heat to travel, less heat transfer e.g polar bear
2. brown adipose tissue
   specialised fat tissue for heat production e.g. babies have a lot
3. size and shape
   higher SA:V means more heat loss e.g fox and polar bear

Question 17

behavioural

Answer 17

1. kleptothermy
   huddling e.g penguins huddling
2. torpor
   temporary reduced metabolic rate to retain or lose heat e.g. hummingbirds enter daily torpor when feeding is not possible
3. hibernation vs aestivation
   extended torpor for extreme heat or cold e.g bears and lizards

Question 18

physiological

Answer 18

1. vasomotor control
   dilation - more heat loss
   constriction - less heat loss
2. evaporative heat loss
   water is a good heat conductor
   sweating to cool down
3. counter-current heat exchange
   blood loses heat as it reaches outside of the body for minimal heat loss due to concentration G, blood vessels are close together for more efficient heating up
4. thermogenesis
   shivering - muscles
   non-shivering - brown adipose tissue
5. homeostatic
   thyroid hormone (thyroxin) released to increase metabolic activity. Hypothalamus releases TRH
   pituitary secretes TSH
   then T3 and T4 released
   more respiration needs more glucose
   more insulin
   then needs more glucose again
   glucagon converts glycogen into glucose for more uptake.

Question 19

osmoregulation in animals

Answer 19

structural: kidney reabsorbs water through loop of henle

behavioural: burrowing, drinking more water, nocturnal behavious

physiological: loop of henle

homeostatic: antidiuretic hormone for more water absorption

Question 20

osmoregulation in aquatic

Answer 20

osmoconformers - doesnt maintain internal conditions e.g crustaceans

osmoregulators - maintains internal conditions regardless of the environmental conditions e.g. fish

freshwater fish:
- hypertonic relative to the water
- drink lots of water
- constantly losing water
- urinate very little

saltwater fish:
- hypotonic relative to the water
- barely drink water
- urinate lots
- water constantly coming into the fish

Question 21

osmoregulation in plants

Answer 21

xerophytes: have no water, small leaves to decrease transpiration, thick waxy cuticle, more stomata under leaf to decrease transpiration

mesophytes: normal
waxy cuticle is thinner than that of xerophytes

hydrophytes: in water
do not have stomata
have very air spongy mesophyll for efficient gas exchange

halophytes: salty
mostly same as xerophytes
actively transport salt into roots for osmosis of water

homeostatic:
absisic acid, promotes the water from the vacuoles from guard cells to be reabsorbed