homeostasis Flashcards
homeostasis definition
the maintenance of internal environments within restricted limits through physiological control systems
why is homeostasis important
ensures the maintenance for optimal conditions for enzyme action and cell function
give 6 examples of factors controlled by homeostasis
- core body temperature
- metabolic waste e.g. CO2,urea
- blood ph
- blood glucose conc
- blood water potential
- conc of respiratory gases in blood, e.g.CO2, O2
what are the 3 main factors controlled by homeostasis
temperature
ph
blood glucose conc
what are the effects of temperature being too high or low
if temp is too high enzymes denature as heat breaks peptide bonds so less enzyme substrate complexes formed
if temp is too low enzymes are too slow as they don’t have enough energy so less enzyme substrate complexes formed
what are the effects of ph being too high or low
at ph extremes enzymes denature because excess OH-/H+ causes peptide bonds to break so active site shape changes so less enzyme substrate complexes formed
what are the effects of blood glucose conc being too high or low
if blood glucose conc is too high it can have a large impact on water potential of blood and can lead to crenation/bursting of cells
if blood glucose conc is too low there may not be enough glucose for respiration
ectotherm definition
an animal that is dependent on external sources of heat and behaviourally thermoregulates
endotherm definition
an animal that can internally generate heat and physiologically thermoregulates
thermoregulation definition
the ability of an organism to keep its body temp within specific limits
hypothalamus definition
a region of the brain which controls homeostatic systems + nervous systems + pituitary gland
what makes up the nervous system
CNS - central nervous system, consists of brain + spinal cord - and PNS - peripheral nervous system, consists of the rest of the nerves in the body
outline the function of the nervous system
it allows us to detect + respond to surrounding stimuli and coordinate + regulate bodily functions
this is done by sending information through nerve impulses
responses are instant
nerve impulse definition
electrical signals that pass along nerve cells/neurones
nerve definition
a bundle of neurones
outline the function of neurones
neurones coordinate the activity of sensory receptors and decision making centers in CNS and effectors
hormone definition
a chemical substance produced by an endocrine gland and carried in the blood
outline the function of a hormone
hormones transmit information within an organism and bring about a change by altering the activity of one or more target organs
they are used to control functions that don’t need instant responses
gland definition
a group of cells that produce + secrete substances + hormones
cell signalling definition
the process by which cells communicate with eachother
what makes the nervous and endocrine system effective communication systems
- they cover the whole body
- enable both long and short term responses
why is cell signalling important
it allows multicellular organisms to control and coordinate their bodies and respond to their environments
outline the process of cell signalling
- stimulus is received by receptor cell
- stimulus is converted into a signal (a chemical) through transduction
- signal is transmitted to a target cell (effector) that can detect it via receptors on the cell surface membrane
- an appropriate response is made
what are the 3 types of cell signalling pathways
paracrine, endocrine, neuronal signalling
pacrine signalling vs endocrine signalling
paracrine signalling is signalling between cells that are close together, with cytokines that diffuse through tissue fluid and are either taken up by cells or regraded by enzymes
endocrine signalling is signalling between cells that are far apart via circulatory system
what is a cell signalling molecule
these are the signal molecules transported around in the process of cell signalling
can be proteins, glycoproteins, amino acids, lipids, etc - e.g. in endocrine signallign it is always hormones, either peptide or lipid
should be small for easy transport across cell membranes
what are receptor molecules
receptor molecules allow target cells ot detect the signalling molecules so a specific change or reaction can be carried out
receptors can be either proteins or glycoproteins, and can be on the cell surface membrane or in the cell cytoplasm
negative feedback definition
when the body responds to a change by reversing the change or reducing the initial effect of the stimulus
what 3 parts are involved in a negative feedback cycle
receptor - to detect stimuli
coordination system - to transfer information, e.g. endocrine or nervous
effector - to carry out response
give 2 examples of processes managed by negative feedback cycles
ADH secretion
blood glucose regulation
positive feedback cycle definition
when the body responds to a change by enhancing the initial effect
give 2 examples of positive feedback cycles
cervical contractions in labour - due to oxytocin
blood clotting
what is the optimum core body temp in humans
37C
what does it mean if body temp is too high or low
above 38C can indicate fever
below 35C can indicate hypothermia
give 2 examples of endotherms
mammals, birds
how do endotherms detect temperatures
through peripheral receptors - found in skin + mucous membranes, receptors for both hot and cold - these receptors communicate with the hypothalamus to bring about a physiological response to changing external temperatures
the hypothalamus also detects body temp by monitoring the temp of the blood flowing through it
give 2 examples of ectotherms
replites, fish
give an example of how ectotherms heat up and cool down
to heat up they seek out the sun or warm surfaces, and rest or bask until their body temp has been sufficiently raised
to cool down they seek shade or water
outline some advantages and disadvantaged of being an endotherm or an ectotherm
the behaviour of ectotherms is more limited by environmental temps, so they cannot easily colonise habitats that are very hot or very cold
endotherms require much more energy to maintain body temps so much greater food requirements, so they cannot survive as well in environments where food is limited
what is the difference between environments on land and in water
on land temperature can vary greatly across seasons or in a single day - this means terrestrial ectotherms may experience lots of difficulty maintaining their stable environment
however water is a stable environment and has a very high specific heat capacity so temp of water is much less variable - aquatic ectotherms have little difficulty maintaining a stable internal environment
give 3 examples of cooling mechanisms in endotherms
vasodilation
sweating
flattening of hairs
describe how vasodilation aids in thermoregulation
- heat exchange occurs at skin surface due to short distance between blood and external environment
- arterioles have muscles in walls so can relax to dilate lumen allowing them so carry higher volumes of blood
- supplying capillaries in skin with a higher volume of blood increases heat loss by radiation
describe how sweating aids in thermoregulation
- sweat is secreted by sweat glands + cools the skin by evaporating off it, which uses heat energy from the body
- this is less effective in high humidity due to shallower water potential gradient
describe how flattening of hairs aids in thermoregulation
- hair erector muscles in skin relax so hairs lie flat
- this stops an insulative layer of air from forming and so heat can leave body through skin via radiation
give 4 warming mechanisms in endotherms
vasoconstriction
boosting metabolic rate
shivering
erection of hairs
describe how vasoconstriction aids in thermoregulation
- arteriole wall muscles contract to constrict lumen, so vessels can only carry smaller volumes of blood
- this causes blood to be diverted to shunt vessels further from skin surface, increasing diffusion distance
- this means there is a lower volume of blood near the skin to less heat loss via radiation
describe how boosting metabolic rate aids in thermoregulation
- most metabolic reactions are exothermic so release heat, so increase body temp
- body secretes thyroxine to increase basal metabolic rate and increase heat production in body
describe how shivering aids in thermoregulation
- a reflex action in response to decrease in core body temp
- nervous system response
- muscles are effectors - they rapidly contract and relax
- metabolic reactions needed to generate energy for this movement are exothermic so generate heat so increase body temp
describe how erection of hairs aids in thermoregulation
- hair erector muscles in skin contract and cause hairs to stand up
- this forms an insulating layer over skins surface by trapping air between hairs, so stops heat loss via radiation
some insects are also endotherms - give 2 reasons why would it be more difficult for insects to thermoregulate than mammals or birds
- mammals/birds have thicker insulation
- insects have higher SA:Vs so heat generated is lost more easily
