Physiology Flashcards
what is a membrane?
form the outer boundary of every cell- selectively permeable and control entry and exit to a cell.
What is a phospholipid bilayer?
hydrophobic, non polar, uncharged tail
hydrophillic, polar, charged head
what is the function of cholesterol?
contributes to stability and fluidity, stiffens the membrane
what are the different types membrane proteins?
intergral- embedded in bilayer, receptors
peripheral- do not penetrate bilayer
transmemrane- extend through membrane, transporters and channels
What are membrane carbohydrates?
small chains on outer surface, glycoproteins and glycolipids
functions of lipid bilayer?
- basic structure
- barrier
- responsible for membrane fluidity
Functions of proteins?
- water filled highly-selevtive ion channels
- carrier/transporters
- interact with secretory vesicles leadign to exocytosis of vesicle content
- membrane bound enzymes
- receptors
- cell adhesion molecules (cadherins- hold cell within tissue together, integrins- span membrane acting as a link between extra and intra cellular environments)
functions of carbohyrates?
serve as self-identifying markers enabling cells to identify and interact with one another
what are desmosomes?
adhering junctions that anchor cells together
what are tight junctions?
join lateral edges of epithelial cells near luminal membranes
what are gap junctions?
communicating junctions that allow movement of charge carrying ions and small molecules between 2 adjacent cells
what is passive transport?
diffusion down a concentration gradient or movement along an electrical gradient- does not require energy
what is an electrochemical gradient?
where an electrical and a concentration gradient may be acting on a particular ion at the same time
define osmosis
net diffusion of water down a concentration gradient
what are aquaporins
water channels
what is osmoralilty
concetration of osmotically active particles in a solution
what is tonicity
effect a solution has on a cell volume
iso/hypo (cell swells)
hyper (cell shrinks)
what tonicity is saline
isotonic
What is facilitated diffusion?
no energy required- carrier mediated, from high to low concentration
what is active transport?
energy required- moves agains concentration gradient, from low to high
what is active transport?
energy required- moves agains concentration gradient, from low to high
what is primary active transport?
energy directly requires (ATP)
what is secondary active transport?
ransporter protein couples the movement of an ion (typically Na+ or H+), the transfer of the ion supplies the driving force
Symport transport:
co-transport, solute and Na+ move in same direction
Antiport transport:
exchange, solute and Na+ move in opposite direction
what is Na+K+ATPase an example of
primary active transport
3 Important roles of Na+K+ATPase
- establish Na and K conc gradients across membrane
- regulate cell volume by controlling concentration of solutes inside cell
- energy used to drive the pump indirectly serves as energy source for secondary active transport
What is endocytosis?
is the process by which materials move into the cell (engulfed into a vesicle)
what is exocytosis?
vesicle fuses with membrane and releases its contents to the extracellular fluid
what happens to a cell when it is placed in hypertonic solution
water flows out of cell
what happens to a cell when it is placed in hypotonic solution
water flows into the cell
describe the concentration gradients for K+ and Na+
K+= outwards Na+= inwards
describe the membrane potential of an ion
the greater the membrane potential for a given ioan, the greater the tendancy for that ion to drive the membrane potential towards the ions own equilibrium potential
describe the membrane potential of an ion
the greater the membrane potential for a given ioan, the greater the tendancy for that ion to drive the membrane potential towards the ions own equilibrium potential
(this is why the mem poten is closer to K than Na+)
what is the membrane potential for K
-90mV
what is the membrane potential for Na
+61mV
what is nernst equation
Eion=61log10 x ion(in)/ion(out)
what is the resting membrane potential for a typical nerve cell?
-70mV
why is the resting potential not identical to Ek
due to the slight inward leak of Na+ into the cell
Goldman-hodgkin-katz equation
calculates overall membrane potential
(hyperpolarisation= more neg)
(depolarisation=more pos)
Hormones that control glucose:
- in absorptive and post absorptive states (insulin and glucagon) in the pancreas
- in emergencies (adrenaline) in the adrenal gland
- during starvation (cortisol) in the adrenal gland and (growth hormone) from the pituitary gland
what are the pancreatic islets of langerhans?
Pancreatic islets, also called islets of Langerhans, are tiny clusters of cells scattered throughout the pancreas. Pancreatic islets contain several types of cells. (endocrine glands)
what are the different types of pancreatic islets?
alpha cells= glucagon
beta cells= insulin
delta cells= somatostatin
in absorptive state of glucose what happens to the pancreatic cells?
insulin rises and glucagon falls (increase in glucose)
what is the function on insulin?
stimulated the uptake of glucose from the blood into muscles and fat cells
what is the function on insulin?
stimulated the uptake of glucose from the blood into muscles and fat cells (favours anabolism) hormone of the fed state, turns glucose–> glycogen and fatty acids–> triglycerides
effects of insulin?
- increased glucose
- increased amino acids
- increased parasympathetic activity
what is GLUT4
glucose transporter protein that insulin causes to be inserted into the plasma membrne of muscle and fat cells, originates from intracellular stores
what is the function of glucagon?
breaks down to form glucose, hormone of the hungry state
effects of glucagon?
- raises glucose by increasing gylcogenolysis
- inhibits live glycogen synthesis
- promotes live gluconeogenesis
- increased sympathetic activity
why doe severe diabetes cause thirst
severe diabetes causes thirst- high glucose levels in urine cause large urine volume in addition to high glucose in conc in blood–> dehydration
what us lipolysis?
compensatory increase in order to provide an alteration in energy source
what are ketone bodies
formed in severe diabetes due to the metabolism of fatty acids generating acetyl CoA, the liver is unable to process the excess acetyl CoA through the citric acid cyle so they are converted to ketone bodies
blood gas alterations in severe diabetes
metabolic acidosis (compensatory hyperventilation) blood pH is lowered
Type 1 diabetes
- early onset
- no isulin secretion
- defect in beta cells
- ketosis development
- insulin injections requires
Type 2 diabetes
- adult onset
- insulin secretion may be normal
- defect in insulin sensitivity
- diet/excercise/oral drugs
effects of adrenaline
- raised glucose
- stimulates glycogenolysis/ gluconeogensis
- produced by storage granules of the medulla
- released in emergencies
- important in the rapid metabolism of fuel
effects of cortisol
- raised glucose
- produced byt hte zona fasciculate in adrenal gland
- stimulates protein catabolism
- stimulates gluconeogensis
- stimulates lipolysis
- not important for rapd mobilisation of fuel
- conc is highest at morning and lowest at night
- produced in response to stress
Effects of growth hormone
- important in starvation
- anteriror lobe of pituitary
- decreases glucose uptake by muscles
- mobilises glucose from liver
- promotes lipolysis in fat cells
where are baroreceptors located
carotid sinus and aortic arch
function of baroreceptors
sensitive to stretch, firing rate increases when MAP increases and decreases when MAP decreases. they only respond to acute changes in BP- changes in HR, SV, TPR
where is the baroreceptor control centre
medulla
What is BP
hydrostatic pressure exerted by the blood on blood vessel walla
what is MAP
the average arterial blood pressure during a single cardiac cycle
What are the major resistance vessles?
arterioles
what MAP is required to perfuse body tissues
60mmHg
what is vasomotor tone?
tonic discharge of sympathetic nerves resulting in the continuous release of noradrenaline
Homeostasis
component of our bodies internal environment must be maintained within narrow ranges
core body temp
37.8, normal body temperature is optimum for cellular metabolsim and function- shows dinural variation
consequences of over heating
- protein denature
- nerve malfuntion
- death
- convulsion
what hormones can increase basic metabolic rate?
- adrenaline
- noradrenaline
- thyroxine
how is heat lost from the body?
- radiation
- convection (air next ot skin warmed by conduction, warmed air less dense so rises and cool air moves next to skin)
- conduction
- evapouration(energy is required to convert water in the skins surface and the lining of the resp airway into water
passive evapouration
water passively diffuses from surface of the skin and the linigsof the resp airways
active evapouration
sweating controlled by sympathetic nervous system
how is core temp maintained
negative feedback control
where are the temp receptors located?
central (hypothalamus and abdominal organs)
peripheral (skin)
hypothalamus
small area in brain, bodys therostat posterior hypothalamus= cold -vasoconstriction -increased muscle tone -shivering Anterior hypothalamus= warm -vasodilation -sweating -decreased muscle tone
what nervous system stimulated sweating
sympathetic nervous system
what nervous system stimulated sweating
sympathetic nervous system
what is an endogenous pyrogen
chemicals that macrophages release in response to infection or inflammation and stimulate the release of protiglandin in the hypothalamus
what is the effect of pyrogen
they reset the thermostat in the hypothalamus to a higher temp ie fever
what happens when pyrogen release is stopped?
the thermostat is set to normal
fever
38-40
hyperthermia
> 40
hypothermia
<35
hypoglycaemia
4 is the flood
chronic can damage blood vessels
what is glycosuria
glucose in the urine
