Unit 2 Topic 1: Homeostasis Flashcards
Homeostasis
the maintenance of relatively stable internal conditions within narrow tolerance limits via negative feedback mechanism.
receptors
thermoreceptor - temperature
nociceptor - pain
photo - light
mechano - pressure
chemo - chemicals
effectors
muscles - contract
glands: endo and exocrine
metabolism
sum of the net chemical processes in the body
changes in metabolic activity and catalytic activity
- enzymes denature from metabolic heat
- decreased means dereased ROR
CNS
brain
spinal chord
interconnecting neurons
PNS
the rest of the body, motor and sensory neurons
myelin sheath
- insulates and protects signa;
- speeds up transmission of signal
Nerve impulse transmission within neuron
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
between neurons
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).
hormones
are chemical messengers released from glands that prompt a response from specific cells.
they only act upon cells with the complementary receptor.
water soluble hormones
binds extracellularly, from amino acids.
1. ion channel receptor
2. G protein couples receptor
3. tyrosine kinase
fat soluble hormones
bind intracellularly, drived from glycerol and fatty acids
how does receptor binding activate signal transduction
- binding
- activation
- signal transduction
- amplification (second messengers)
- changes in cellular activity
- negative feedback
heat loss and gains
endotherms: regulate internal temp
exotherms: internal temp is affected by environmental conditions
structural features of thermoregulation
- insulation
more distance for heat to travel, less heat transfer e.g polar bear - brown adipose tissue
specialised fat tissue for heat production e.g. babies have a lot - size and shape
higher SA:V means more heat loss e.g fox and polar bear
behavioural
- kleptothermy
huddling e.g penguins huddling - torpor
temporary reduced metabolic rate to retain or lose heat e.g. hummingbirds enter daily torpor when feeding is not possible - hibernation vs aestivation
extended torpor for extreme heat or cold e.g bears and lizards
physiological
- vasomotor control
dilation - more heat loss
constriction - less heat loss - evaporative heat loss
water is a good heat conductor
sweating to cool down - 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 - thermogenesis
shivering - muscles
non-shivering - brown adipose tissue - 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.
osmoregulation in animals
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
osmoregulation in aquatic
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
osmoregulation in plants
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
