Unit 1 Flashcards
what is physiology?
the science of the function of living systems
function vs process
function –> why
- why does the system exist
-why does the event occur
Process –> How
-how does a system work
- physiological mechanism
what is homeostasis
- maintenance of a relatively stable internal environment around a set point
local vs relex control
Local
- cells near site of change initiate response
reflex control
- cells at a distant site control response
what is a response loop
stimulus, sensor, input signal, integrating centre, output
signal, target, response
what are the types of feedback
- negative feedback- stabilizes variable
- feedforward control- anticipates change
- positive feedback- reinforces stimulus – not homeostatic
what are electrical signals
- changes in membrane potential
- restricted to nerve and muscle cells
what are chemical signals
- secreted into extracellular fluid by all cells
- responsible for most of the communication
- cells that respond to signals are called target cells
what are the types of long range cell- cell communication
- endocrine
-neural - neuro endocrine
what is endocrine communication
chemical (hormone) released into blood stream and distributed throughout body
what is neural communication
electrical signal travels down neuron; reaches end and is translated to chemical signal (neurotransmitter) which transmits information to next cell
what is neuro endocrine communication
electrical signal travels down neuron; reaches end and is secreted into blood
what is a target cell
- Only cells that have receptors for that signal will respond to it
- signal molecule that binds to a particular receptor is its ligand
- Receptors are proteins that project to outside of the membrane, or are within the cell, in the cytoplasm
- Chemical properties of signal molecules (ligands) determine what type of receptor they will interact with
what are the types of ligands and receptors
- water soluble = hydrophilic = lipophobic –> surface receptor
- water insoluble = hydrophobic = lipophilic –> intracellular receptor
what are the types of membrane receptors
- ion channel
- enzyme coupled receptor
- G protein coupled receptor (GPCR)
- integrin receptor
variation of signal pathways
- one ligand may have several different types of receptors
- receptors exhibit saturation, specificity, competition for their ligands (and molecules similar to their ligands)
- cells can change their response to signals by changing receptor number or sensitivity
explain ligands having different receptors
- same signal can have different effects in different cell types
explain how receptors exhibit saturation, specificity, competition for their ligands
- e.g. relative affinities of adrenergic receptors for epinephrine versus norepinephrine
– e.g. agonists and antagonists competing with endogenous ligands
explain how cells can change their response to signals by changing receptor number or sensitivity
- increase –> ↑ gene expression (up-regulation)
– decrease –> internalize surface receptors (down-regulation)
– change receptor sensitivity –> e.g. phosphorylation 19
what is an agonist
- a molecule that is similar to the natural ligand and it activates the receptor
what is an antagonist
- a molecule that is similar to the natural ligand but it does not activate the receptor (blocker)
**Cholera**
what are cannon’s postulates
- the nervous system has a role in maintaining ‘fitness’ of the internal environment (coordinates responses that regulate blood volume, blood pressure, osmolarity, body temp, …)
- some systems are under tonic control
- some systems are under antagonistic control
- one chemical signal can have different effects in different tissues
what is tonic control
- regulates physiological parameters in an “up- down” fashion
- such as a neuron increasing or decreasing its firing rate
