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Endo > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

Draw or describe the overall homeostatic control of circulating cortisol?

A
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2
Q

Why does the value of a controlled variable always oscillate around a set point?

A

There is a time delay in sensing a change and its
correction
- Never a flat line basically

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3
Q

Draw or describe the overall homeostatic control of blood pressure?

A

Changes to heart (CO) and peripheral resistance

  • > Occurs via symp. nerves (Increases, when BP falls)
  • > Leads to changes to CO (CO increases with activation of symp.
  • >Leads to changes to HR and TPR -> affecting BP

Due to HR= CO x SV and BP= TPR x HR

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4
Q

What is the effect of a pyrogen on the homeostatic control of body temp.

A

Pyrogen (Bacterial or viral infection)

Infection will cause set point to a higher level
resulting in fever
-> Core body temp. rises

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5
Q

Outline principle of negative feedback and +ve feedback

A
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6
Q

What is the benefits of a higher body temperature in defence of pyrogens?

A

Inhibits bacterial growth
Speeds up metabolic reactions
Increases delivery of white blood cells to infection sites

Pyrogens (viral or bacterial infection)

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7
Q

State 2 examples of regulated physical entities?

A

Blood pressure
Core temperature

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8
Q

State 2 examples of Circulating concentrations of chemical substances?

A

Ions e.g. Na+, Ca2+
Nutrients e.g. blood glucose concentration
Hormones

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9
Q

What is the role of the detector/sensor in the homeostatic feedback system?

A

Detects when controlled variable moves away from set point
-> Known as afferent pathway (goes towards control centre)

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10
Q

Describe how BP is restored after a haemorrhage

A

After a haemorrhage blood volume and hence blood pressure are reduced
To help restore blood pressure several homeostatic control systems are activated:
1. Baroreceptor reflex to increase cardiac output and total peripheral resistance
2. stimulation of vasopressin (ADH) secretion to increase blood volume

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11
Q

Role of effector in the homeostatic feedback system?

A

Effector use processes formulated via control centre to
return variable to set point via efferent pathway
- Induces response

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12
Q

Describe the process of control of uterine contractions in labour and how it shows
positive feedback?

A
  1. In labour oxytocin stimulates contraction of uterine muscles
  2. Cervix dilates and activate stretch receptors
  3. Action potentials signal to hypothalamus
  4. Stimulates further release of oxytocin
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13
Q

State the 5 components of the feedback system in homeostasis in order?

A
  1. Regulated factor/controlled variables
    - Set point, operating range, error signal
  2. Detector/sensor (afferent pathway)
  3. Comparator/control centre (intrinsic or extrinsic)
  4. Effector (efferent pathway)
  5. Response
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14
Q

Draw or describe the overall homeostatic control of the core body temp.?

A

At last stage, Body temps change is measured by receptors and send back to hyp. creating a feedback loop until set point is reached

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15
Q

How is the body temperature increased during an infection?

A

Blood flow shifted to core to conserve heat
Increased muscle activity (shivering)
Chills stop when high temp reached

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16
Q

State the components of the controlled variables in the homeostatic feedback
system and define?

A
  1. Set point= Pre-defined normal value
  2. Operating range= Normal range that variable can oscillate around set point
  3. Error signal= value of the controlled variable minus the set point
    - > When value is out of operating range or moving away from set point
    - > Signals to control centre
17
Q

What does the integrated feedback loops within the body ultimately control?

A

Sodium balance
Blood pressure
Fluid volume

18
Q

Which events would induce an increase in body tempature during its regulation?

A

Shivering
Vasoconstriction
Increased metabolism

FC:
Reduces heat loss to the enviroment

19
Q

What stimulates the release of cortisol?

A

In hypo.CRH (corticotropin-releasing hormone) stimulates ACTH secretion
From PG., ACTH (adrenocorticotropic hormone) stimulates cortisol secretion via adrenal gland

20
Q

What is the effect of long-term hypertension on the homeostaic control pathway of BP?

A

Hypertension= Increases BP long term
-> Causes the sensitivity of baroreceptors to reset

Baroreceptors adapt to sustained changes in arterial BP

21
Q

Role of comparator/control centre in the homeostatic feedback system?

A

Determines set point of variable, compares and maintains variable at set point

Occurs via

  • Intrinsic: local – cell or tissue autoregulates
  • Extrinsic: endocrine system, nervous system
22
Q

What is the homeostatic control cycle of blood pressure known as?

A

Baroreceptor reflex

23
Q

State the receptors and control centre involved in the homeostatic pathway of
blood pressure?

A

Baroreceptors- strecth receptors
Stretch receptors found in wall of arteries which detect BP

Control centre= Medulla

24
Q

What is the set point for cortisol affected by?

A 
Stress (increases)
Circadian rhythm (body clock)
25
Q

Which events would induce a decrease in body tempature during its regulation?

A

Vasodilation
Sweating

26
Q

Describe how the body temp. in terms of its time course differs during an infection?

A

Infection leads to a rapid shift in set point
- But actual temp. lags behind for many hours until reaching it
- Even when reached, regulation is maintained during fever
but is less precise

27
Q

State the role of vasopressin in the control of BP?

A

ADH leads to vasoconstriction and renal fluid reabsorption
-> Renal fluid reabsorption leads to increased blood volume

Both vasoconstriction and increased blood volume increases arterial pressure

28
Q

How does haemostasis display positive feedback?

A

The response of the effector output reinforces the stimulus e.g. blood clotting, ovulation, childbirth
- Clotting occurs where platelets come once break in wall occurs, which then attract more platelets via released chemicals

Less common physiologically as it is like a “runaway train” (less control)

29
Q

Define homeostasis?

A

Ability or tendency of an organim or cell to maintain internal equilibrium
by adjusting its physiological process

30
Q

State the receptors and control centre involved in the homeostatic pathway of
core body temp?

A

Cutaneous temp. receptors
Hypothalamic temp. receptors

Control centre= Hypothalamus

31
Q

What causes the release of ADH from the pituitary glands?

A

Angiotensin II
Hyperosmolarity
Decreased atiral receptor firing
Sympathetic stimulation

32
Q

How is ‘challenge’ and ‘physiology’ involved in homeostasis?

A 
Challenge'= Produces change in body status
'Physiology'= Responds to maintain homestasis

Endo (9 decks)

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