what is the hydrophilic bilayer composed of
- hydrophilic heads
- hydrophobic tails
what is the role of cholesterol in the cell membrane
- contributes to fluidity and stability
- stiffens membrane
what are the 3 possible locations of proteins in/around cell membrane
- integral (embedded within)
- peripheral (don’t penetrate membrane)
- transmembrane (extend through membrane)
what is the location of carbohydrates in relation to the cell membrane and what types are there
- small amount located on outer surface
- glycoproteins, glycolipids
what are the 3 functions of the lipid bilayer
- basic structure of membrane
- hydrophobic interior acts as barrier
- responsible for membrane fluidity
The glycocalyx layer is formed by…
Short carbohydrate chains bound to proteins and lipids
what are the main functions of proteins
- water filled, selective ion channels
- carrier/transport proteins
- docking/marker acceptors
- receptors or enzymes
- cell adhesion molecules
what are the 2 types of cell adhesion molecules
- Cadherins (hold cells within tissues together)
- Integrins (span membrane to link intra and extracellular environments)
what are occlusion/tight junctions
join neighbouring cells together to prevent diffusion
what are anchoring/desmosome junctions
they provide mechanical support, anchor cells together
what are communicating/gap junctions
they create pores to allow the movement of molecules between 2 cells
what are the 2 types of passive transport
- diffusion
- electrical gradient
during passive transport where do cations move to
cations move towards -vely charged areas
what does Fick’s Law of diffusion relate to
- size of concentration gradient
- surface area of membrane
- lipid solubility
- molecular weight
- distance for diffusion
what is an electrochemical gradient
Where an electrical and a chemical concentration gradient may be acting on a particular ion at the same time
define osmosis
- Net diffusion of water down its concentration gradient
- conc. of osmotically active particles in a solution
- aquaporins are water channels
how is osmolarity calculated
Using molar concn (mM) and number of osmotically active particles (n)
150mM NaCl has osmolarity = ?
150 x 2 (Na+ and Cl-) = 300mOsm
define tonicity
effect a solution has on cell volume
what effect does a hypotonic solution have on cell volume
increases cell volume
what effect does a hypertonic solution have on cell volume
decreases cell volume
what happens during carrier-mediated transport
substance binds to specific carrier and changes its conformation to transport it
what effects carrier-mediated transport
- specificity
- saturation
- competition
what is facilitated diffusion
- no energy required
- carrier-mediated
- from high to low conc.
what is active transport
- energy required
- from low to high conc.
what is primary active transport
energy directly required
what is secondary active transport
- energy required but not used directly
- energy stored in form of ION CONC. GRADIENT (usually Na+)
what are the mechanisms of secondary active transport
- symport (same direction)
- antiport (opposite direction)
what is vesicular transport
- energy for vesicle formation
- endocytosis or exocytosis
what type of active transport is is NaKATPase pump
- primary active transport
_ Na+ out for every _ K+ in with regards to Na-K pump
3, 2
3 roles of NAKATPase pump
- Establish Na and K concentration gradients across
- regulate cell volume
- energy source
what is the membrane potential (Em)
- separation of charges across membrane
- units are mV
what are the direction of Na and K ion movements
- K moves outwards
- Na moves inwards
at resting potential the membrane is 100x more permeable to what
more permeable to K than Na
describe movement of K+ ions
- K+ move down con gradient out of cell
- still negative anions inside cell
- results in electrical gradient moving K+ back into cell
describe movement of Na+ ions
- Na+ move down conc gradient into cell
- still negative anions outside cell
- results in electrical gradient moving Na+ out of cell
what is the membrane potential of Ek
-90mV
what is the membrane potential of Ena
+61mV
what does the Nernst equation calculate
membrane potential of a single ion
what does the Goldman - Hodgkin - Katz equation calculate
overall membrane potential
what is the resting membrane potential of a typical nerve cell
- 70mV
is the resting membrane potential nearer to Ek or Ena
- Ek
- not exactly the same due to slight inward leak of Na
Na channels are…
K channels are….
Na = depolarisation K = repolarisation
define action potentials
brief electrical signals in which the membrane polarity is momentarily reversed
- spread along with constant size and velocity
glucose is a…
metabolic fuel
hormones controlling glucose in absorptive and post absorptive states are..
insulin and glucagon
pancreas
hormones controlling glucose in emergencies are…
adrenaline
adrenal gland
hormones controlling glucose in starvation are…
cortisol (adrenal) and growth hormone (pituitary gland)
name the pancreatic islets of Langerhans (endocrine cells)
- alpha cells = glucagon
- beta cells = insulin
- delta cells = somatostatin
What are the absorptive states
- increased glucose levels
- insulin rises
- glucagon falls
what does insulin favour and what does it do
- favours anabolism
- converts glucose > glycogen
insulin is a hormone of what state
the fed state
diabetes mellitus type 1 has what properties
- early onset
- no insulin secretion
- defect in beta cells
- insulin injections required
diabetes mellitus type 2 has what properties
- adult onset
- insulin secretion may be normal
- defect in insulin sensitivity
- diet/exercise/oral drugs
Diabetics can increase GLUT4 expression by doing what?
exercise
the pulse pressure is the difference between what
systolic and diastolic BP’s
what is the normal MAP range
70-105
how do you calculate MAP
MAP = [(2x diastolic) + systolic]/3 MAP = diastolic + [systolic - diastolic]/3 MAP = CO x SVR
Which receptors control mean arterial BP and where are the receptors
Baroreceptors, located in aortic arch + carotid sinus
what is the control centre used by baroceptosr and what are the effectors
control centre = medulla
effectors = heart and blood vessels
MAP of at least __ is needed to perfuse heart, brain, kidneys
60mmHg
MAP needs to be low enough so that it doesn’t…
damage blood vessels
what happens to the firing rate in baroreceptors when MAP increases
firing rate also increases
Cardiac Output is
- The volume of blood pumped out by each ventricle per minute
- (SV x HR)
Stroke Volume is
- the volume of blood pumped out by each ventricle per heart beat
Increasing contractile strength of the heart causes stroke volume to ____
increase
Vasomotor tone is described as what
Vascular smooth muscle being constricted at rest
define homeostasis
maintenance of a stable internal environment
to maintain homeostasis you must be able to do what
- sense deviations from normal
- integrate this information
- make appropriate adjustments to restore variable
what are intrinsic controls
within organ
what are extrinsic controls
- outside organ
- use nerves and hormones
define feedforward
responses made in anticipation of change
define feedback
responses made after change has occurred
define negative feedback
- opposes initial change
- eg controlling body temp.
define positive feedback
- amplifies initial change
- eg uterus contractions become stronger until birth
what is the core body temperature
37.8 degrees
what is normothermia
when body temperature varies during day (lowest in early morning)
define basal metabolic rate
minimum energy required to sustain body functions
how can the basal metabolic rate be increased
- hormones eg adrenaline
- muscle activity/shivering
what are the 4 methods of heat gain
- metabolic heat
- radiation
- convection
- conduction
what are the 4 methods of heat loss
- convection
- conduction
- radiation
- evaporation
pOsterior hypothalamus is activated by what
cOld
Anterior hypothalamus is activated by what
wArmth
Which receptors monitor body heat? Where are they, the control centre and effectors located?
- Thermoreceptors
- located in the hypothalamus and skin
- Control centre: hypothalamus
- Effectors: skeletal muscles, skin arterioles, sweat glands
a fever is a temperature between what
38-40 degrees
hyperthermia is a temperature between what
> 40 degrees
hypothermia is a temperature between what
35 or below degrees