Communication And Homeostasis Flashcards
what is homeostasis
regulation of the internal conditions of a cell or organism to maintain optimum conditions for function
in response to internal and external changes
two types of communication system
endocrine + nervous
describe the effect of high pH on enzymes
Hydrogen + ionic bonds hold the tertiary structure together
solutions with an excess of H+ / OH– ions = cause these bonds to break
alters shape of active site
enzyme-substrate complexes form less easily
eventually, enzyme-substrate complexes can no longer form at all
complete denaturation
purpose of cell signalling
allows multicellular organisms to control and coordinate their bodies and to respond to their environments
describe the stages of cell signalling
A stimulus is received by a receptor cell
stimulus is converted to a signal - e.g chemical - that can be passed on
(this process = transduction)
signal is transmitted to target cell that can detect it via receptors in its cell membrane
An appropriate response is made
what is paracrine signalling
signalling between cells that are close together
what is endocrine signalling
signalling between cells that are far apart
being transported in the circulatory system
examples of paracrine signalling molecules
amino acids / lipids / phospholipids / glycoproteins
examples of endocrine signalling molecule
hormone
what is negative feedback
reduces initial effect of the stimulus
what is positive feedback
enhances the effect of original stimulus
state three examples of positive feedback
clotting cascade
childbirth
bone repair
describe the clotting cascade as a positive feedback cycle
Blood vessel damaged + platelets stick to region
Release factors that initiate clotting + that attracts more platelets
describe childbirth as an example of positive feedback
Head of baby pressed against cervix
Production of oxytocin
stimulates uterus to contract + baby head pushes even harder against cervix
more oxytocin – until baby born
describe bone repair as an example of positive feedback
involving special cells - osteoblasts and osteoclasts
osteoblasts secrete a hormone - inactive osteocalcin
osteoclasts secrete acid = causes the inactive osteocalcin to become active
active form of osteocalcin binds to a receptor on beta cells in pancreas
stimulates them to release insulin
Osteoblast possess insulin receptors + when stimulated causes them to release more inactive osteocalcin
osteoblast cells enhance the effect of the original stimulus (insulin) - positive feedback
Insulin is known to have anabolic effects, promoting the building of tissues, including bone
what is an endotherm
an animal that possess physiological mechanisms to control their internal body temperature
what is an ectotherm
animals that rely on behavioural adaptations to control temp
example of endotherm
mammals + birds
example of ectotherms
reptiles and amphibians
what is radiation, convection and conduction
radiation – transmission of EM waves
convection – heating + cooling by currents of air / water
conduction – heating by collision of molecules
state the ways an animal can gain + lose heat
how do endotherms detect temperature
detect external temperatures via peripheral receptors / thermoreceptors
hypothalamus monitors temp of blood flowing through it
where are thermorecpetors found
skin and mucous membranes
state the cooling mechanisms of an endotherm
Vasodilation / Sweating / Flattening of hairs
state the warming mechanisms of an endotherm
Vasoconstriction / Boosting metabolic rate / Shivering / Erection of hairs
what is vasodilation / vasoconstriction caused by
caused by the relaxing and contracting of muscles in the arterioles, not capillaries
Capillaries do not have muscles in their walls
describe vasoconstriction + vasodilation
vasoconstriction - muscles in arteriole walls contract + more blood is directed through the shunt vessel
vasodilation - muscle in arteriole wall relax + more blood flow through capillaries near skin surface
how are hairs risen
hair erector muscles contract
how does shivering generate heat
Rapid / involuntary contracting + relaxing of large muscles
Metabolic heat from exothermic reaction
how does rising hair generate heat
insulating layer of air formed
how does sweating loose heat
latent heat of vaporisation
structure of hypothalamus
heat loss centre
heat gain centre
what happens when the heat loss / gain centre is activated
Sends impulses via autonomic nervous system to effectors in skin / muscles
state the difference between thermoregulation of ectotherms in water vs on land
ectotherms in water – don’t need to thermoregulate because of high heat capacity of water = temp stable
types of responses that ectotherms carry out
behavioural
physiological
what are the behavioural responses of ectotherms to cool down
seek shade or water
digging burrows
pressing bodies against cool ground
minimise SA
what are the behavioural responses of ectotherms to warm up
seek out the sun / bask – increase SA
pressing bodies against ground – conduction
contract muscles / wings – exothermic metabolic reactions
what are the physiological responses of ectotherms to warm up
dark skin – absorb more radiation
alter heart rate
what are the issues with ectotherms
environmental temps vary a lot – seasons / in a day
need more energy to maintain body temp
= metabolic rate + food requirement is higher
survival weaker
