physiology Flashcards
what is homeostasis
maintaining stable internal environment by coordinated physiological mechanisms
where are intrinsic controls released from
inside organ
where are extrinsic controls released from
outwith organ eg endocrine or nervous
what is negative feedback
change happens and is detected, mechanisms then activated to decrease change. closed loop
what is the plasma membrane made of
phospholipid bilayer, cholesterol, proteins, carbs
what are phospholipids made of
hydrophilic head and hydrophobic tail
what is the function of cholesterol in the membrane
fluidity and stability
what is the glycocalyx layer formed of
short carb chains bound to membrane proteins. act as surface markers
what are the 3 types of membranes and what are their functions
integral (receptors), transmembrane (channels), peripheral (enzymes)
what are docking marker acceptors
integral proteins on inside of cell that allow secretions
what is the purpose of the phospholipid bilayer
fluidity, barrier, selectively permeable (non polar and size)
what are tight/ occluding junctions
join lateral edges of epithelial cells near apical end
what are desomosomes
adhering junctions that hold cells together
what are gap junctions
allow communication of charge between adjacent cells
what must the concentration gradient be for passive diffusion
high to low
what is Fick’s law
rate of diffusion is affected by: size of % gradient, SA of membrane, lipid solubility, molecular weight and diffusion distance
what is an electrical gradient
differing charges in adjacent membranes promotes high to low movement
ion channel proteins can let ions enter by what 2 ways
leak, or ligand gates
what is an electrochemical gradient
electrical and chemical gradient at same time
what is osmosis
the movement of water down it’s concentration, is passive
what channels let water in
aquaporins
what is osmolarity
% of osmotically active particles in a solution
what is tonicity
effect a solution has on cell volume
what 2 types of carrier mediated transport are there
facilitated diffusion and active transport
what happens to a carrier once it’s substrate binds
conformational change
what is facilitated diffusion
requires no energy, high –> low
what is active transport
requires energy, low –> high
what is primary active transport
energy from ATP directly needed
what is secondary active transport
needs energy indirectly, often from ion % gradient
what are the 2 mechanisms for secondary active transport
symport (co-transport): solute and ion move in same direction.
antiport: exchange where they move in opposite directions
in the NaKATPase pump what goes in and out
2K in, 3 Na out
what type of transport is NaKATPase pump
primary active transport
what are 2 types of vesicular transport
endocytosis (release) and exocytosis (engulf)
what happens in a hypotonic solution
water diffuses out of cell down % gradient
what causes membrane potentials (Em)
separation of opposite (+ive/-ive) charges across a membrane
at resting potential, the membrane is __x more permeable to __ rather than __
100 to K rather than Na
what is the membrane potential (Em) for K+ (Ek)
-90mv (K out of cell than in)
what is the membrane potential (Em) for Na++ (ENa)
+60mv (more Na in cell than out)
what does the NaKATPase pump do
sets membrane potential for cell
what is the Ernest equation (words)
used to calculate equilibrium potential of ion
what is the Ernest equation (maths)
Eion = 61log ([ion]o / [ion]i)
what is resting potential of typical nerve cell
-70mV
why is resting potential closest to K+
cell is more permeable to K, there is a slight leak of Na though
what is the equilibrium potential of an ion
the charge difference when rate of electrical gradient and conc gradient are the same
what is used to calculate overall membrane potential
GHK:
Em = 61log x [(PK+[K+]o + PNa+[Na+]o) / (PK+[K+]i + PNa+[Na+]i)]
what is BP
outward (hydrostatic) pressure of blood on blood vessel walls
what is the normal systolic values
less than 140 mmHg
what is the normal diastolic values
less than 90 mmHg
what is pulse pressure
difference between DBP and SBP, normally 30-50
what is Mean arterial BP equations
MAP = [(2x DBP) + systolic]/3 MAP = DBP + [(DBP + SBP)/3]
what is the normal MAP and what must it be for perfusion
70-105, 60mmHg
what receptors detect changes in BP and where are they located
baroreceptors, carotid sinus and carotid arch
where do baroreceptors send signals too
control signals in medulla oblagata
what are the effectors of baroreceptor response
heart and blood vessels
when BP increases what happens to the rate of firing of baroreceptors
increases, sensitive to stretch
can baroreceptors detect chronic hypertension
no, only small changes. recognise it as ‘normal’
what is autorhythmicity
ability of heart to beat without external stimuli
what is stroke volume
volume of blood ejected by ventricles each beat
what is cardiac output (CO)
blood out of heart in a minute. CO = HR x SV
what effect would increasing contractility have on SV
increase it
what is the equation for BP
BP = SV X HR x SVR
what is vasomotor tone
vascular smooth muscle being partially constricted at rest
what is the normal body temp
37.8 degrees
what is the basic metabolic rate (BMR)
minimum amount of energy required to sustain vital body functions, leads to heat production
how do you increase BMR
hormones eg adrenaline, muscle activity and shivering
what is radiation and how much body heat is lost through it
electromagnetic waves, half
what comes from evaporation
sweating
what sensors detect the core temp and where are they
thermoreceptors in hypothalamus, abdomen, peripheral ones in skin
what are the effectors
skeletal muscles, skin arterioles, sweat glands
what part of the hypothalamus is activated by cold
posterior
what part of the hypothalamus is activated by warmth
anterior
to initiate a fever, what is released in response to infection and by what cells
endogenous pyrogens from macrophages
what does this stimulate to be released from hypothalamus
prostoglandins
what then happens in hypothalamus
core temp is reset to higher, making a fever
what temp indicated fever
38-40
hyperthermia temp
> 40
hypothermia temp
35>
what is normal blood glucose
5 mol (roughly)
what hormones control glucose in absorptive and post-absorptive states and from where
insulin and glucagon from pancreas
in emergencies what hormones control glucose
adrenaline from adrenal gland
during starvation what hormones control glucose
cortisol from adrenal gland and growth hormone from pituitary
in the pancreatic islet cells of endocrine glands. what do alpha cells release
glucagon
in the pancreatic islet cells of endocrine glands. what do beta cells release
insulin
in the pancreatic islet cells of endocrine glands. what do delta cells release
somatostatin
how does insulin lower blood sugar levels
stimulates glucose uptake from blood and activating liver enzymes to convert glucose –> glycogen
how does glucagon raise blood sugar levels
increases glycogenolysis, inhibiting glycogen synthesis
describe diabetes mellitus type 1
little/ no insulin secretion
describe diabetes mellitus type 2
defect in insulin sensitivity normally from being overweight
what transporter can become desensitise in type 2 and what can be done to increase expression
GLUT4, exercise
how does cortisol raise glucose level
stimulates gluconeogenesis, lipolysis and protein catabolism
