Lecture 3 Flashcards
What is Resting Membrane Potential?
Refers to the fact that the inside of a cell is negatively charged compared to its external surface.
Magnitude of negativity inside cell is…….
if outside of membrane is taken as zero
-70mV
What causes RMP?
Separation of a small number of oppositely charged ions across the lipid bilayer.
(overall concentration of ions in the ICF and ECF are not affected)
Definition of RMP:
The resting membrane potential is an……
electrical potential that exists across the cell membrane and is due to different concentrations of ions on each side of the membrane and their respective permeabilites to it.
What is the major determinant for RMP?
The cell membrane is normally much more permeable to K+ than other ions and so K+ is the major determinant of the RMP.
Process of RMP
When the amount of K+ leaving the cell down its ion gradient is balanced by that moving back in due to the electrical gradient we have the RMP.
K+ leaves, negative charge left inside
Electrical gradient atactisch positie ions back in.
What is Regulated Variable?
The variable that the system senses and tries to keep stable
What is Set Point?
The target value for the variable
What is Reference Range?
Values of the regulated variable within acceptable limits.
What is Variation?
In regulated variable values within and between normal people (intra and inter individual variation)
Within an individual variables fluctuate around the ___ _____ in response to ______ _______
Set point
Normal activity
Within an individual, set point can ______ in a regular way in response to _______ ________
Change
Biological Rhythms
Homeostasis is achieved by a combination of _______ and _______-________ control systems
Feedback
Feed-forward
What is Negative Feedback?
Control system that opposes the change in the controlled variable and move it back toward the ‘set-point’
What are the key components and their functions of a negative feedback control system?
1) Sensor - monitors the actual value of the regulated variable
2) Integrator - compares actual and set point values
- determines and controls the response
3) Effector - produce the responses that restore the regulated variable to its ‘set point’
4) Communication Pathways - carry signals between components.
What are two types of physiological communication pathways?
Neuronal
> involves action potentials in axons and neurotransmitter release at synapses
> fast and specific and brief responses
> good for when conditions are changing rapidly and where an immediate response is required to prevent tissue damage or loss of homeostatic control
Hormonal
> released into blood (or ECF)
> targets any cells that have receptors specific for the particular hormone (so 1 hormone can affect many tissues or organs)
> good for widespread sustained responses
Definition of Feed Forward.
Function: Integration centre
Involves detection or anticipation of external (or internal) conditions or situations that could alter a controlled variable if some sore of action was not taken.
Establishes a future ‘predicted value’ for the controlled variable, compares it to the ‘set-point’ and makes anticipatory corrections.
Definition of Positive Feedback.
When is it useful?
Response to a stimulus that moves the controlled variable even further away from the ‘set-point’
When there is a specific end-point or purpose.
e.g. child birth or blood clotting
What are the four ways heat can be transferred between the body and environment?
- Evaporation
- Radiation
- Conduction
- Convection
If the _______ of one compartment changes then water will diffuse by ______ until ________ has been restored.
Osmolarity
Osomosis
Equilibrium
RMP refers to the fact that the _____ of the cell membrane is _______ charged compared to its ______ surface.
Inside
Negatively
External
The resting membrane ______ is an ______ potential that exists across the cell ________ and is due to different ________ of ions on each side of the membrane and their respective _________ to it.
Potential Electrical Membrane Concentrations Permeabilities
Values within ____ standard deviations of the _____ are
considered ‘normal’
Two
Mean
In physiological control of body temperature ‘‘cold’ _____ in the skin detect decreased ______ temperature and then the _________ compares the ______ value with the ‘set-point’ in ____ ______’.
Receptors External Hypothalamus Predicted Feed Forward
Feed-forward involves detection or ________ of external conditions or _______ that could alter a ________ variable if some sort of ______ was not taken.
Anticipation
Situations
Controlled
Action
The _______ centre establishes a future ‘_______ _______’ for the controlled ______ and compares this with the ‘___-____’ and makes anticipatory _______.
Integration Predicted value Variable Set-point Corrections
Positive ______ is a response to a _______ that moves the controlled variable even further _____ from the ‘___-___’.
Feedback
Stimulus
Away
Set-point
