FOM Flashcards
What is pinocytosis?
- form of endocytosis. Cell engulfs extracellular fluid and dissolved substances into vesicles
- non-specific, energy-dependent, continuous
What is autocrine communication?
-communication within the same cell
What is paracrine communication?
- communication with neighbouring cells
What is endocrine communication?
- communication with distant cells
What is the redundancy?
- multiple systems may regulate given parameter
- give alternatives to take over when there is a system fail
What are the clinical effects of excess water?
- hyponatraemia: low sodium. Too much water diluting electrolytes
- oedema: pooling of fluid in interstitial spaces
What is the clinical effect of loss of water?
- dehydration: mild (up to 3L)/severe (up to 7L)
Who are more susceptible to dehydration?
- young: dependency issue, inability to communicate, SA:V
- old/woman: depending, communication, inaccurate assessment of input and output
What is osmotic pressure?
- physical pressure required to oppose the osmotic movement of water across the membrane
What is osmolarity?
- measure of particles within a solution (osmoles)
- used to refer to concentration of biological fluids
- number of osmotically active particles/litre water
What is osmolality?
- number of osmotically active particles/kg water
What are the roles of biomembranes?
- form boundaries, divide cells into compartments, allow conc. gradients to be established, place of communication and transport
What does amphipathic mean?
- portion of a molecule is charged (polar) whilst rest is uncharged (non-polar)
What is the liquid crystalline phase?
- double bonds prevent very close packing of acyl chains, bilayer where chains are mobile
How do ligand gated channels work?
- gate opens when chemical/ligand binds to channel/receptor
- gate is closed when chemical/ligand is absent
How do voltage gated channels work?
- gate opens when there is a certain level of charge imbalance across the cell membrane
- gate is closed under resting conditions
What are the general classes of hormones?
- peptide/protein
- amino-acid derived: stored in secretory vesicles prior to release, rapidly broken down
- steroid/lipid: derived from cholesterol, lipid soluble
Explain anticipatory feedback in relation to thermoregulation
- body prepares for a change in physiological variable before change actually occurs
- step into cold environment, body may start vasoconstriction even before core body temp. drops
Describe lipids in biomembranes
- lipid signalling occurs in membrane regions rich in cholesterol called lipid rafts
- based on sterols, glycerides and sphingolipids
What does increasing unsaturation of lipid cause?
- add flexibility and fluidity to membrane
- increase space in membrane for movement
- maintain liquid crystalline phase
Describe ICF ion distribution
- low sodium, high potassium, low chloride
What are symports?
- membrane transport proteins that move two or more substances across a cell membrane in the same direction simultaneously
- type of secondary active transport mechanism
What does hyperkalaemia result in?
- results in depolarisation of resting membrane potential
- causes an initial increase in excitability followed by a reduction in excitability
