Homeostasis Flashcards
Homeostasis (def)
Process by which an organism maintains a stable internal environment, despite fluctuating external environmental conditions
Pos feedback ↺
- Enhances or amplifies change from a system
- This moves the system away from equilibrium
- e.g. the process of parturition is a PFL
Neg feedback ထ
- Detects change and brings the system back to equilibrium
Why homeostasis important?
- constant internal environ ensures efficient transport of substances around body
- ensures enzymes function effectively -> optimises metabolic efficiency
Draw neg feedback ထ
homeostasis process (5)
- STIMULUS (provokes resp)
- RECEPTOR (organ that contains neurons/detects change)
- CONTROL CENTRE (information passed through nervous system to brain)
- EFFECTOR (creates response i.e. muscles/glands)
- RESP (occurs and counteracts changes thus maintaining stability)
TEMP NFL - stim? recep?
both too high/too low
- stim: Body temperature increases/decreases bc weather/exercise
- recep: Thermoreceptors recognise blood warmer/colder than hypothalamic set point
TEMP NFL - contr cen?
both too high/too low
- temp too ↑: Activates heat-loss center in hypothalamus (anterior - front area)
- temp too ￬: Activates heat-promoting center in hypothalamus (posterior - back area)
TEMP NFL - effectors?
when too high (3)
- vasodilation - capillaries flushed with warm blood near skin surface -> heat loss
- sweat glands activated - perspiration/evaporation which uses heat to work - the heat comes from body (cools skin surface/🩸)
- thyroid glands activated (picture) = lower metabolism rate = ↓ amount of thyroxine produced = generate < body heat
TEMP NFL - effectors?
when too low (4)
- vasoconstriction - blood from skin capillaries withdrawn to deeper tissues to minimise heat loss
- contraction of hair erector cells - standing hair traps layer of warm air -> reduces heat loss
- pituitary gland increases thyroxine secretion, ↑ rate of metabolism & generating more heat in the body
- rapid contraction of muscles -> shivering (generates heat)
BGL NFL - hormone released when glucose too high?
insulin
BGL NFL - hormone released when glucose too low?
glucagon
BGL NFL - stim? recep?
both too high/too low
- stim: rising/declining BGL (after eating/hungry respectively)
- recep: High BGL detected by beta cells in pancreas, Low BGL detected by alpha cells in pancreas
BGL NFL - cont cent?
both too high/too low
- too high = Beta cells in pancreas stimulate the release of insulin into the blood
- too low = Alpha cells in pancreas stimulate the release of glucagon into the blood
BGL NFL - effectors
both too high/too low
- too high = Most cells take up more glucose & Liver stores glucose as glycogen
- too low = Liver breaks down glycogen into glucose and releases it into the blood
BGL NFL - resp?
both too high/too low
- too high = BGL declines to set point, stimulus for insulin release diminishes as BGL decreases
- too low = BGL increases to set point, stimulus for glucagon release diminishes as BGL increases
🌊 concentration NFL process?
endotherms
organisms that can maintain a constant internal body temperature through homeostatic mechanisms, independent of the environment
ectotherms
organisms that have a limited ability to control their body temperature
- their cellular activities generate little heat thus their body temperatures rise and fall with ambient temperature changes
endotherm behav adap (gen)
- movement to wet/shaded/sunny area
- licking: enables more heat to be evaporated through saliva
- drinking water
- nocturnal activity
- migration -> assists thermoregulation
endotherm struc adap (gen)
- insulation (feathers, fur, hair)
- hot environ -> smaller animals with large SA:V ratio -> lose heat easily
- large, thin ears -> rapid heat loss
endotherm phsy adap (gen)
- vasoconstriction & vasodilation
- metabolic rates: can be increased to increase the production of heat energy internally, or decreased to cool body temp
- muscle contraction (e.g. shivering)
- sweating & panting
behav, struc, phys adap
- b: lick chest & inside of forearms - when the moisture evaporates it cools the blood, which circulates close to the surface at these points
- s: large ears which have lots of blood vessels close to the surface
- p: vasodilation of capillaries at extremities (& licks)
additional behav adap
Kangaroos are mostly active in the early morning or evening, when it is cooler.
During the day, when the temperature is most extreme, kangaroos spend the time resting under the shade of trees.
what is this animal?
Greater Bilby (Macrotis lagotis)
behav, struc, phsy adap
B: Sleeps in a deep burrow during the day to avoid the heat
S: Large, thin ears to release heat
P: Produces concentrated urine to reduce water loss
what happens to the metabolic rate of endotherms as external temp increases?
their metabolic rate decreases
2 methods msgs are sent arnd body?
via nerve impulses or hormones
nerve impulses much faster compared to hormones which travel through the circulatory system
hORmoNEs
- signalling molecules used by the body to regulate physiology and behaviour
- affect cells by binding to specific receptors on their surfaces, enacting changes in a process called signal transduction
sig transdu process
The process where cells receive and convert signals from the enviro to cell responses
- reception
- transduction
- response
endo syst - pituitary gland loc?
base of brain, directly under hypothalamus
endo syst - pituit. gland func?
- ‘master gland’ releases hormones often in direction from the hypothalamus to regulate the activity of the other glands
- anterior (front) secretes growth hormone
- posterior (back) secretes antidiuretic hormone (ADH) which helps regulate the concentration of water in the body AND oxytocin for when one is having a baby
how homeostasis maintained by pituit. gland for post. ADH?
- If receptor cells in the hypothalamus detect that the levels of water in the body are too low, hypoth stimulates the pituitary gland to release ADH
- This acts to conserve water in the body by promoting its reabsorption by the kidney tubules
- Opposite occurs when the level of water in the blood is too high – the hypothalamus detects this and directs the pituitary gland to reduce its production of ADH
- This leads to less water being absorbed in the kidneys and the increased excretion of water
endo syst - hypothal loc?
endo syst - hypothal func?
CONTROL CENTRE FOR MAINTAINING HOMEOSTASIS
- releases thyrotropin, ADH, oxytocin (milk ejection, labour contraction)
- acts as a link btwn nervous & endocrine systems
endo syst - pineal gland?
Secretes melatonin which helps regulate circadian rhythm (which involves sleep-wake cycle)
endo syst - thyroid gland?
(two lobes located on either side of the neck)
- Produces thyroxine (speed up chemical reactions/metabolism)
- Makes calcitonin which can lower the blood calcium level
endo syst - parathyroid glands (PG)?
WHEN PG detects calc lvl too low, it secretes parathyroid hormone (PTH); when lvl too high, stops secrete PTH
- function = maintain level of calcium in blood
- calcium is required for successful transfer of nerve impulses in the nervous system and allows muscles to contract properly
- PTH travels to effectors: bone - release calcium into blood, small intestine - absorb more calcium from digested food, kidneys - reabsorb more calcium in the tubules
endo syst - adrenal glands - loc? consists of?
loc on top of each kid-knee
adrenal medulla & adrenal cortex
endo syst - adrenal medulla?
- regul by nerve impulses from hypothal
- in homeostasis, secretes hormones adrenaline and noradrenaline -> fight or flight resp
endo syst - adrenal cortex?
- secretes cortisol which increases BGLs
- plays a role in regulating cardiovascular function and blood pressure
- releases aldosterone which increases the reabsorption of sodium ions and decreases the reabsorption of potassium ions in the kidney -> return to tol limits
- opp can occur - low level of sodium ions in the blood will reduce blood volume and therefore blood pressure
endo syst - pancreas loc?
back of abdomen (belly)
endo syst - pancreas func?
Chemoreceptors in beta cells detect high levels of glucose in the blood & stimulate production of insulin
◗ In the liver, the glucose is converted into glycogen and fat.
◗ Skeletal muscles convert the glucose into glycogen.
◗ Glucose is converted into fat in fat storage tissue.
Alpha cells in the islets of Langerhans produce glucagon in response to low levels of glucose in the blood
◗ the breakdown of glycogen in the liver
◗ the breakdown of fat in the liver and the fat storage tissues
nerv syst - spinal cord CNS?
acts as a conduction pathway for nerve impulses from the receptors around the body to the brain
&
for nerve impulses from the brain to the effectors
neurons are…
& draw/label
Specialised cells that transmit nerve impulses through electrochemical signals
types of neurons
& what do they look like?
- Sensory neurons - PNS → CNS - transmit impulses from sense organs to other neurons in the CNS
- Motor neurons - transmit nerve impulses from the CNS to muscles and glands
- Connector neurons - connect sensory neurons and motor neurons (usually in the CNS)
nerv syst - types of receptors (part of homeostasis)
- Thermoreceptors - detect changes in temperature
- Chemoreceptors - detect changes in pH and the concentration of certain chemicals inside the body
- Osmoreceptors - detect changes in osmotic pressure and are located in the hypothalamus
wtf is osmotic pressure?
Osmotic pressure in the blood is determined by the concentration of substances dissolved in the blood plasma. Small changes in osmotic pressure cause the body to implement processes that regulate the amount of water in the body, keeping it within the tolerance limits.
nerv syst - action potential - polarisation
The inside of the membrane is said to be negative in relation to the outside - the membrane is polarised - the resting potential of the axon cell membrane is -70mV (millivolts)
nerv syst - action potential - depolarisation
- when neuron detects stimulus, it causes sodium (Na+) channels in the cell membrane to open
- more Na+ ions outside the neuron than inside, the Na+ ions move into the neuron and reduce the overall negative charge
- if stim strong enough, it could change the resting potential to its threshold value of
–55mV (the movement of Na+ ions into neuron will continue independently of stim –> ALL OR NONE PRINCIPLE) - this causes the inside of the membrane to become more positive in relation to the outside of the neuron, and the potential to move to 0mV and beyond - the membrane has been depolarised.
nerv syst - action potential - repolarisation
- Just as quickly, the potassium channels open and K+ ions move out of the neuron, causing the repolarisation of the membrane
- The potassium channels stay open a little longer and the action potential goes past –70mV (hyperpolarisation) before returning to its original resting state
nerv syst - action potential - refractory period
check this is correct
for another signal to start, memb pot needs to be brough back to -70
- need to have more Na+ outside and some k+ inside
- but Na+ refuses to move outside as there are more Na+ outside
- Na/K pump uses ATP to move Na+ out and K+ in by active transport
what fig must be reached for act pot to occur?
reach a threshold value of –55mV
Adaptations of Australian Plants to Prevent Water Loss
what plants?
- southern 🔵 (blue) gum
- needle bush (💉🌳)
- casuarina
Adaptations of Australian Plants to Prevent Water Loss
southern blue gum (🌿 adap)
- 🌿 change orientation during the day to ensure only edges, not the full SA, are exposed to 🌞
- Shiny 🌿 -> refl 💡
- Thick, waxy cuticle - 💧 can’t move past oily outer cuticle
- Partially deciduous (lose 🌿 during extended dry periods)
Adaptations of Australian Plants to Prevent Water Loss
southern 🔵 gum (bark 🤜🏿 adap)
- Dry bark to prevent water loss
Adaptations of Australian Plants to Prevent Water Loss
southern blue gum (√ adap)
- √ system is deep & well developed -> allow access to deep ground 💧
Adaptations of Australian Plants to Prevent Water Loss
💉🌳 adap
- Thin needle-like leaves = less transpiration of 💧 = less 💧 loss
Adaptations of Australian Plants to Prevent Water Loss
casurarina adap
- 🌿s reduced to tiny 🟤 scales
- Stem has taken over photo synthetic function which reduces the SA:V ratio -> minimises 💧 loss
adaptations 🌴s have to:
max uptake of 💧
- extensive root systems
- stems & trunks shaped so they direct water twrds roots
adaptations 🌴s have to:
📉 plant 🍃 internal 🌡️
- Shiny waxy cuticle or thick leathery cuticle
-> ensures that all the epidermal cells are waterproof, preventing loss of 💧 by evaporation from these surface cells - ⚪ hairs reflect 💡
-> reduces 🌡️ on the surface of 🍃 and thus reduces evaporation
adaptations 🌴s have to:
📉 the difference in 💧 concentration btwn the 🌴/outside air
- sunken stomata
- epidermal hairs to trap humidity
- curled or rolled leaves (e.g. spinifex)
glycogen vs glucagon
- glucagon = hormone that pancreas makes to help regulate blood glucose (sugar) levels
- glycogen = stored form of glucose
when labelling action potential, it only occurs…
above -70mVs
NOT hyperpolarisation + refractory period below -70mVs
as seen in the graph
what instrument do they use to measure act pot?
oscilloscope
if asked a Q about act pot graph, …
‘divide’ the graph in parts and talk about them individually - don’t talk about it generally
adaptations plants have to minimise water loss
- curling of leaves
- hairy stomata
- controlled stomata opening and closing
- hanging leaf orientation
- thick, waxy cuticle
