Homeostasis Flashcards
negative feedback
small change in one direction is detected by sensory receptors and effectors are signalled to reverse the change and restore conditions to their basic level within a narrow range
positive feedback
change in the internal environment of the body is detected by sensory receptors and effectors are signalled to reinforce the change and increase the response
two examples of positive feedback
- blood clotting (platelets release clotting factors which attract more platelets until a clot is made)
- childbirth (head of baby pressed against cervix which stimulates production of oxytocin stimulating contractions to press head harder against the cervix
six example of physiological factors controlled by homeostasis in mammals
- temperature
- metabolic waste (CO2, urea)
- water potential of blood
- blood pH
- blood glucose concentration
- respiratory gases concentration in blood (CO2 and O2)
why is thermoregulation important?
- optimum temps must be maintained for enzymes in metabolic reactions
- high temps can denature proteins
- high temps can disrupt membranes
why is osmoregulation/salt balance important?
- it affects blood Ψ
- high blood Ψ will make water move out of blood into cells causing lysis
- low blood Ψ will make water move out of cells into blood causing high blood pressure and slowing cellular metabolic reactions
why is glucose concentration important to maintain?
- glucose is the only fuel for some cells (e.g. brain cells)
- low [glucose] will slow respiration rate
- high [glucose] will decrease Ψ of blood and increase blood pressure
why is it important to control blood pressure?
- low blood pressure causes blood to stagnate (slow blood flow means less O2 etc transported via blood)
- high blood pressure can damage delicate blood vessels
what directlt determines blood pressure?
- force of heart contraction
- dilation of blood vessels
why is it important to control [CO2]?
- CO2 is acidic and can lower blood pH
- affects tertiary structure of Hb and lowers affinity for O2
transduction
the process of converting a stimulus into a signal that can be passed on
what are the two types of signalling pathways in animals?
- paracrine signalling
- endocrine signalling
paracrine signalling
signalling between cells that are close together
endocrine signalling
signalling between cells that are far apart (which involves transport of a signaling molecule via the circulatory system)
difference between signaling molecules produced by cells and endocrine signaling
- paracrine signaling molecules produced by cells can belong to various chemical groups including proteins, glycoproteins, amino acids, lipids and phospholipids
- endocrine signalling molecules are always hormones
what do negative feedback loops involve?
- receptor
- coordination system (nervous of endocrine)
- effector
how does the magnitude the correction change during negative feedback?
as the factor gets closer to its normal value the magnitude of correction reduces
methods of gaining heat in ectotherms (label as behavioural or physiological)
behavioural:
- basking
- body raising (minimise SA touching surface to minimise heat dissipation)
- positioning themselves for maximum exposure to radiation (e.g. butterflies spreading wings)
- contract muscles/vibrate to increase cellular metabolism
physiological:
- bradycardia (reduce blood flow, reduce heat loss)
- change in skin colour (lighter absorbs more radiation)
methods of losing heat in ectotherms (labelled as behavioural or physiological)
behavioural:
- shelter/shade
- bathing in water
- lying flat (increase SA in contact with surface to dissipate more heat energy)
physiological:
- tachycardia (increase blood flow to increase heat loss)
- change in skin colour (lighter absorbs less radiation)
endotherms
animals that possess physiological mechanisms for the maintenance of internal body temperature
ectotherms
animals that rely on behavioral mechanisms to maintain internal body temperature
four types of heat transfer and what are they?
- radiation - heat transfer in the form of EM waves (usually infrared)
- conduction - heat transfer with physical touch with a surface
- convection and evaporation - transfer of heat through liquids and gases
why don’t ectotherms living in water need to thermoregulate?
water is thermostable, it has a high specific capacity so the external environment doesn’t change much
why is the metabolic rate of endotherms so much higher than ectotherms of similar size?
endotherms regulate their temperature actively with physiological responses whereas ectotherms rely more on behavioral responses which don’t require metabolic processes
