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HUBS191 > Principles of Homeostasis > Flashcards

Principles of Homeostasis Flashcards

0
Q

Resting Membrane Potential (RMP)

A

Refers to the fact that the inside of the cell membrane is negatively charge compared to its external surface.

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1
Q

What happens if the osmolarity of one compartment changes?

A

Water will diffuse by osmosis until equilibrium is restored.

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2
Q

What is the magnitude of the negativity inside the cell?

A

Typically about -70mV

If outside of membrane is taken as 0mV

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3
Q

What causes the RMP?

A

The separation of a small number of oppositely charged ions across the lipid bilayer. (Doesn’t affect conc of ions in ICF and ECF)

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4
Q

What is the major determinant of the RMP?

A

K+ because it is cell membrane is more permeable to it than other ions.
Can ignore other ions for now.

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5
Q

Hypothetical cell has ICF K+ conc of 150mmol/L and ECF K+ conc of 4mmol/L, what happens?

A

When amount of K+ leaving the cell down its conc gradient is balanced by that moving back in due to the electrical gradient we have the RMP.

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6
Q

Does the RMP remain constant?

A

Yes for most cells

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7
Q

What tissues have a RMP that changes?

A 
Excitable tissues (nerve/muscle) 
Must change to function
Usually via opening/closing specific channels
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8
Q

Physiological significance of RMP?

A

It must change for the nervous system and cardiac muscle to function.

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9
Q

Controlled variable

A

The variable that tries to stay stable.

Eg speed of a car

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10
Q

Set point (for variable)

A

Target variable for controlled variable

Eg. 100km/h

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11
Q

Reference (normal) range

A

Values of the controlled variable within acceptable limits.
Eg 90-110km/h
Average 2 s.d. Either side of set point

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12
Q

Variation for homeostasis

A

Values within and between ‘normal’ people

Inter and intra individual variation

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13
Q

What causes variation in homeostasis?

A
  • genetic factors give different set points (interindividual variation)
  • variation may occur within an individual (intra individual variation)
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14
Q

Variation in response to biological rhythms

A

24hrs blood glucose

Monthly female hormones

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15
Q

What context needs to be considered for variations in homeostasis?

A

Age/sex/size/time of day

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16
Q

Homeostasis is controlled by

A

Feedback and feed forward control systems

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17
Q

Negative feedback

A

Opposes the change in controlled variable and moves back towards the set point

18
Q

Key components of the negative feedback system

A
  1. Sensor
  2. Integrator
  3. Effector
  4. Communication pathways
19
Q

Sensor

A

Monitors actual value of controlled variable.

Can be same as integrator

20
Q

Integrator

A
  • Compares actual and set point values
  • Determined and controls the response
  • Can be the same as sensor
21
Q

Effector

A

Produce response that restores to set point

22
Q

Communication pathways

A

Carry signals between components

23
Q

Physiological communication pathways

A

Neuronal (relies on nerves)

Hormonal

24
Neuronal physiological communication pathways
- fast (up to 100m/s) - specific - good for rapidly changing conditions Where immediate response required to protect tissue from damage or loss of homeostatic control - good for brief responses
25
Hormonal physiological communication pathway
- hormones released into blood (or ECF) - target cells that have specific receptors for particular hormone - good widespread sustained responses Eg fluid volume regulation
26
Evaporation
Of water from the skin takes heat from the body
27
Radiation
Transfer of heat from the surface of one object to another without contact. Heat radiates from the body to cooler objects. To the skin from warmer objects.
28
Conduction
Transfer of heat to any substance in contact with body
29
Convection
Transfer of heat away from the body by movement of heated air or fluid particles.
30
Feed forward
Detection/anticipation of external/internal conditions that could alter a controlled variable (or disrupt homeostasis) if action not taken.
31
What role does the integration centre have in feed forward
Establishes a future 'predicted' value for controlled variable, compares this with the set point and makes anticipatory corrections. Eg goosebumps/shivering when cold (Physiological) - putting more clothes on/seeking shelter if skin cold (behavioural)
32
Positive feedback
A response to a stimulus that moves controlled variable even further away from a set point. - not commonly physiological and most causes harm (detrimental)
33
Physiological positive feedback
Where there is a specific end point/purpose: - childbirth (uterus expanding) - blood clotting (blood cells moving to clot)
34
Diabetes Mellitus:
Failing to regulate blood glucose concentration
35
What type of diabetes Mellitus is no insulin produced?
Type 1
36
What happens if type 1 diabetes is not treated?
Polyuria: large amounts of water lost from body (urine) increased osmolarity Polydipsia: leads to excessive thirst Polyphasic: can't get glucose from blood to cells (energy deprived) excessive hunger
37
Type 2 diabetes Mellitus
- decreased insulin secretion | - hyperglycaemia (but different to type 1) eg less fat breakdown & ketone production
38
Consequences of absolute insulin deficiency (acute) | Type 1 mostly
- hyperglycemia - glycosuria - polyuria - dehydration - thirst - breakdown of protein and fat - ketoacidosis
39
Hyperglycemia
High blood glucose - inability of most cells to absorb glucose - low energy production - ice eased output of glucose by liver (body thinking it is being fed)
40
Glycosuria
Glucose in the urine | - kidneys can't absorb all glucose
41
Ketoacidosis
Fatty acids metabolised so there are too many | - pH drops
42
Consequences of absolute insulin deficiency | Chronic problems
- cardiovascular disease - renal failure - retinal damage - poor wound healing - peripheral nerve damage - susceptibility to infection
43
Type 2 diabetes problems
Still some insulin production - enough to prevent ketoacidosis & limit tissue breakdown - not enough to prevent hyperglycemia

HUBS191 (13 decks)

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