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Principles > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

What is human physiology?

A

The study of normal human function and the mechanisms controlling this

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2
Q

Define the term homeostasis

A

The maintenance of steady states within the body by coordinated physiological mechanisms

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3
Q

What does the body need to function normally?

A

Stable internal environment

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4
Q

What is feedforward control?

A

When responses made in anticipation of change

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5
Q

What is feedback control?

A

When responses made after change occurs

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6
Q

What is positive feedback control?

A

When change occurs, signal produced initiates further change eg. child birth - the more oxytocin the body produces, the more oxytocin is produced and the faster the contractions become
The initial change is amplified
Less common than negative feedback control

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7
Q

What is the main tupe of homeostatic control in the body?

A

Negative feedback control

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8
Q

What happens when homeostasis is disrupted?

i.e. homeostatic mechanisms are deficient, inappropriate, or excessive

A

Disease or death

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9
Q

How does negative feedback promote stability?

A

Regulation of a controlled variable by monitoring the information flowing through a closed loop

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10
Q

Give examples of variables controlled at cell membrane level

A

Water and electrolyte concentration within and outwith cells

Membrane potential

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11
Q

What are the three steps through which a physiological control system maintains homeostasis?

A
  1. Sensing a variable move outwith accepted limits
  2. Integrating information with other relevant info
  3. Initiating response to return variable to within accepted limits
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12
Q

What are the three steps through which a physiological control system maintains homeostasis?

A
  1. Sensing a variable move outwith accepted limits (sensor)
  2. Comparing value sensed with set point (control center)
  3. Initiating response to return variable to within accepted limits (effector)
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13
Q

What is negative feedback control?

A

When a change occurs, signal produced initiates counteraction, when no action is needed, no signal produced
No news, is good news

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14
Q

What is negative feedback control?

A

When a change occurs, signal produced initiates counteraction, when no action is needed, no signal produced
No news, is good news

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15
Q

Give two examples of variables controlled by negative feedback

A

Blood pressure

Body temperature

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16
Q

What is blood pressure?

A

outwards pressure exerted by blood on vessel walls

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17
Q

What is systolic blood pressure?

A

Pressure exerted on walls of aorta and systemic arteries when heart contracts
<140 mm Hg

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18
Q

What is diastolic blood pressure?

A

Pressure exerted on walls of aorta and systemic arteries when heart relaxes
<90 mm Hg

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19
Q

What does pulse mean?

A

The difference between systolic and diastolic blood pressures
Usually between 30 to 50 mmHg

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20
Q

What does the mean arterial blood pressure (MAP) mean ?

A

Average arterial blood pressure during one cardiac cycle

Normal range = 70 to 105 mm Hg

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21
Q

How can mean arterial blood pressure be estimated?

A

MAP = [ ( 2 x diastolic ) + systolic ] /3

MAP = diastolic + (pulse/3)

MAP = Stroke volume x heart rate x systemic vascular resistance

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22
Q

Why is it important to control MAP?

A

If < 60 mm Hg, pressure not high enough to perfuse internal organs

If >105 mmHg, pressure is too high and could damage blood vessels or put extra strain on heart

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23
Q

What is the baroreceptor’s role in short-term regulation of MAP?

A

Senses change in blood pressure and sends information to medulla via 9th and 10th
Firing rate increases when MAP increases, and decreases when MAP decreases

24
Q

What is cardiac output?

A

Volume of blood pumped by each ventricle of heart per minute

25
Q

What is systemic vascular resistance?

A

Sum of resistance of all vasculature in systemic circulation

26
Q

What is a normal systolic/diastolic pressure under resting conditions?

A

systolic - < 140 mm Hg

diastolic - < 90 mm Hg

27
Q

What is a normal heart rate?

A

60 to 100 bpm

28
Q

What is a normal MAP?

A

70 to 105 mm Hg

29
Q

What makes up systemic arterial blood pressure?

A

Systolic and diastolic blood pressures

30
Q

Define Hypertension

A

Clinic blood pressure of 140/90 mmHg or higher

Day time average of 135/85 mmHg or higher

31
Q

Why is MAP not average of systolic and diastolic blood pressures?

A 
Diastole = 2/3 of time during cardiac cycle
Systole = 1/3 of time during cardiac cycle
32
Q

What is stroke volume?

A

Amount of blood pumped by left ventricle into aorta per contraction

33
Q

How is Cardiac output (CO) calculated?

A

CO = stroke volume x heart rate

34
Q

What type of receptors are baroreceptors?

A

Mechanoreceptors

35
Q

What 3 things can regulate MAP?

A

Heart rate
Stroke volume
Systemic vascular resistance

36
Q

What is autorhythmicity?

A

The heart’s ability to beat without any external stimuli

37
Q

What alters heart rate?

A

Autonomic nervous system

38
Q

What increases the heart rate?

A

Stimulation from sympathetic nerves using noradrenaline on beta1 receptors

39
Q

What is tachycardia?

A

Fast heart rate

40
Q

What is bradycardia?

A

Slow heart rate

41
Q

What decreases heart rate?

A

Stimulation from parasympathetic vagus nerve (10th cranial nerve)
using acetylcholine

42
Q

What kind of receptors does acetylcholine act on?

A

Muscarinic

43
Q

What increases stroke volume?

A

Increased contractile strength of heart

44
Q

What stimulates contractile strength of heart to increase?

increasing stroke volume

A

Sympathetic nerves in ventricular myocardium

45
Q

Are there many parasympthetic nerves in the ventricular myocardium?

A

No

46
Q

Can stroke volume be controlled intrinsically?

A

Yes, through Starling’s Law of the heart

47
Q

Which blood vessels produce the most systemic resistance?

A

Arterioles

48
Q

What regulates the systemic vascular resistance?

A

Smooth muscle in vasculature

49
Q

What does contraction of smooth muscle in blood vessels cause?

A

Vasoconstriction

50
Q

What does relaxation of smooth muscle in blood vessels cause?

A

Vasodilation

51
Q

How does vasoconstriction affect SVR and MAP?

A

Increases SVR and MAP

52
Q

How does vasodilation affect SVR and MAP?

A

Decreases SVR and MAP

53
Q

What is vasomotor tone?

A

When smooth muscles in blood vessels are constantly partially contracted

54
Q

What causes vasomotor tone?

A

Sympathetic nerves constantly causing low level of stimulation, meaning noradrenaline is constantly released

55
Q

Is vasomotor tone affected by any parasympathetic nerves?

A

No

Except in penis and clitoris

56
Q

How does increased /decreased sympathetic discharge affect vasomotor tone?

A

VT increased - vasoconstriction

VT decreased - vasodilation

Principles (21 decks)

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