Lecture 3

Question 1

What is Resting Membrane Potential?

Answer 1

Refers to the fact that the inside of a cell is negatively charged compared to its external surface.

Question 2

Magnitude of negativity inside cell is…….

if outside of membrane is taken as zero

Answer 2

-70mV

Question 3

What causes RMP?

Answer 3

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)

Question 4

Definition of RMP:

The resting membrane potential is an……

Answer 4

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.

Question 5

What is the major determinant for RMP?

Answer 5

The cell membrane is normally much more permeable to K+ than other ions and so K+ is the major determinant of the RMP.

Question 6

Process of RMP

Answer 6

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.

Question 7

What is Regulated Variable?

Answer 7

The variable that the system senses and tries to keep stable

Question 8

What is Set Point?

Answer 8

The target value for the variable

Question 9

What is Reference Range?

Answer 9

Values of the regulated variable within acceptable limits.

Question 10

What is Variation?

Answer 10

In regulated variable values within and between normal people (intra and inter individual variation)

Question 11

Within an individual variables fluctuate around the ___ _____ in response to ______ _______

Answer 11

Set point

Normal activity

Question 12

Within an individual, set point can ______ in a regular way in response to _______ ________

Answer 12

Change

Biological Rhythms

Question 13

Homeostasis is achieved by a combination of _______ and _______-________ control systems

Answer 13

Feedback

Feed-forward

Question 14

What is Negative Feedback?

Answer 14

Control system that opposes the change in the controlled variable and move it back toward the ‘set-point’

Question 15

What are the key components and their functions of a negative feedback control system?

Answer 15

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.

Question 16

What are two types of physiological communication pathways?

Answer 16

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

Question 17

Definition of Feed Forward.

Function: Integration centre

Answer 17

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.

Question 18

Definition of Positive Feedback.

When is it useful?

Answer 18

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

Question 19

What are the four ways heat can be transferred between the body and environment?

Answer 19

• Evaporation
• Radiation
• Conduction
• Convection

Question 20

If the _______ of one compartment changes then water will diffuse by ______ until ________ has been restored.

Answer 20

Osmolarity
Osomosis
Equilibrium

Question 21

RMP refers to the fact that the _____ of the cell membrane is _______ charged compared to its ______ surface.

Answer 21

Inside
Negatively
External

Question 22

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.

Answer 22

Potential
Electrical
Membrane
Concentrations
Permeabilities

Question 23

Values within ____ standard deviations of the _____ are

considered ‘normal’

Answer 23

Two

Mean

Question 24

In physiological control of body temperature ‘‘cold’ _____ in the skin detect decreased ______ temperature and then the _________ compares the ______ value with the ‘set-point’ in ____ ______’.

Answer 24

Receptors
External
Hypothalamus
Predicted 
Feed Forward

Question 25

Feed-forward involves detection or ________ of external conditions or _______ that could alter a ________ variable if some sort of ______ was not taken.

Answer 25

Anticipation
Situations
Controlled
Action

Question 26

The _______ centre establishes a future ‘_______ _______’ for the controlled ______ and compares this with the ‘___-____’ and makes anticipatory _______.

Answer 26

Integration
Predicted value
Variable
Set-point
Corrections

Question 27

Positive ______ is a response to a _______ that moves the controlled variable even further _____ from the ‘___-___’.

Answer 27

Feedback
Stimulus
Away
Set-point