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JL Principles > Physiology - Human > Flashcards

Physiology - Human Flashcards

0
Q

Define the term feedback

A

Refers to responses made after a change has been detected

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1
Q

Define the term feedforward

A

The term used for responses made in anticipation of a change

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2
Q

Give an example of a negative feedback system

A

Control of blood pressure

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3
Q

Name the three components of negative feedback systems

A
  1. Sensor - monitors magnitude of a controlled varfiable
  2. Control center - compares sensor’s input with a set point
  3. Effector - makes a response to produce a desired effect
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4
Q

What does positive feedback do?

A

Amplifies an initial change

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5
Q

Give an example of positive feedback

A

Uterine contractions during labour become increasingly stronger until the birth of baby

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6
Q

In relation to the negative feedback system of mean arterial pressure: state the controlled variable, sensor, control centre and effector.

A

Mean arterial pressure
Baroreceptors
Cardiovascular control centre (medulla)
Heart (heart rate and stroke volume) and blood vessels (total peripheral resistance)

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7
Q

What is blood pressure?

A

The outwards (hydrostatic) pressure exerted by teh blood on blood vessel walls

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8
Q

What is systolic arterial blood pressure?

A

The pressure exerted by the blood on the walls of the aorta and systemic arteries WHEN THE HEART CONTRACTS.

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9
Q

What is the normal systolic pressure?

A

Normally <140 mmHg under resting conditions

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10
Q

What is diastolic arterial blood pressure?

A

The pressure exerted by the blood on the walls of the aorta and systemic arteries WHEN THE HEART RELAXES.

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11
Q

What is the normal diastolic arterial blood pressure?

A

Normally <90 mmHg

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12
Q

What is mean arterial blood pressure (MAP)?

A

The average arterial blood pressure during a single cardiac cycle, which involves contraction and relaxation of the heart.

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13
Q

Which portion of the cardiac cycle is longer - diastolic or systolic?

A

The diastolic portion is twice as long as the systolic portion.

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14
Q

What is the formula for estimating mean arterial blood pressure?

A

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

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15
Q

What is the other formula for estimating mean arterial blood pressure using pulse pressure?

A

MAP = DBP + 1/3 (pulse pressure, which is the difference between SBP and DBP)

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16
Q

What is the normal range of mean arterial blood pressure?

A

70 - 105 mmHg

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17
Q

What is the minimum mean arterial blood pressure needed to perfuse the coronary arteries, brain and kidneys?

A

At least 60 mmHg

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18
Q

Where are the 2 groups of baroreceptors located in?

A

The aortic arch and carotid sinus

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19
Q

How do the carotid baroreceptors signal to the medulla?

A

Via the IXth CN (glossopharyngeal)

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20
Q

How do the aortic baroreceptors signal to the medulla?

A

Via the Xth CN (vagus)

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21
Q

What kind of receptors are the baroreceptors and what are they sensitive to?

A

The baroreceptors are mechanoreceptors which are sensitive to stretch.

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22
Q

What stimulates an increase in the firing rate of baroreceptors afferent neurons?

A

Increases when the mean arterial blood pressure increases

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23
Q

Where do the baroreceptors send afferent impulses to?

A

The cardiovascular control centre in the medulla of the brainstem

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24
Q

What is the Nucleus Tractus Solitarius (NTS)?

A

The site of 1st synapse for all CVS afferents in the medulla

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25
Q

What other regions of the brain does the NTS relay information to?

A

The medulla, hypothalamus and cerebellum

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26
Q

Where is the generation of vagal outflow to the heart relayed to?

A

The nucleus ambiguus in the medulla

27
Q

CO X TPR = ?

A

MAP

28
Q

What is cardiac output?

A

The volume of blood pumped by each of the ventricles of the heart per minute

29
Q

CO = ?

A

stroke volume (SV) x heart rate (HR)

30
Q

What is stroke volume?

A

The volume of blood pumped by each ventricle of the heart per heart beat

31
Q

What is total peripheral resistance (TPR)?

A

The sum of resistance of all peripheral vasculature in the systemic circulation

32
Q

What three things can regulate MAP?

A

Heart rate
Stroke volume
Total Peripheral Resistance

33
Q

What is autorhythmicity?

A

The heart being capable of beating rhythmically in the absence of external stimuli.

34
Q

What acts on beta-1- receptors?

A

Noradrenaline

35
Q

What does acetylcholine act on?

A

Muscarinic receptors

36
Q

What are the major resistance vessels?

A

Arterioles

37
Q

What are vascular smooth muscles supplied with?

A

Sympathetic nerve fibers

38
Q

Vascular smooth muscles are partially constricted at rest - what is this called?

A

Vasomotor tone

39
Q

What is vasomotor tone caused by?

A

Tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline

40
Q

What will an increased sympathetic discharge do to the vasomotor tone?

A

Increase it resulting in vasoconstriction

41
Q

When the MAP is low what happens to the rate of carotid afferent nerve fibres firing?

A

Decreases

42
Q

When the MAP is low, what happens to the rate of cardiac vagak efferent nerve fibres activity?

A

Decreases

43
Q

When the MAP is low, what happens to the cardiac sympathetic efferent nerve fibres activity?

A

Increases

44
Q

When the MAP is low, what happens to the sympathetic vasoconstrictor nerve fibres activity?

A

Increases

45
Q

Acute changes in BP are only responded to by?

A

Baroreceptors

46
Q

What is normothermia?

A

The normal core body temperature

47
Q

What does overheating do to protein, nerves and the body?

A

Protein denaturation, nerve malfunctions, convulsions and death

48
Q

What is tympanic temperature?

A

Temperature taken from the ear drum

49
Q

What is oral temperature affected by?

A

Consumption of food and drinks

50
Q

When will an individual have their lowest temperature?

A

In the early morning - diurnal variation in body temperature

51
Q

What happens to the normal body temperature during menstrual cycle?

A

In menstruating females it is higher during the 2nd half of the cycle from the time of ovulation

52
Q

What are the 4 ways heat can be lost to the external environment?

A

Convection
Conduction
Radiation
Evaporation

53
Q

What leads to the basic level of heat production?

A

The Basal Metabolic Rate

54
Q

What is the basal metabolic rate?

A

The minimum amount of energy required to sustain vital body functions

55
Q

What 3 hormones can increase the BMR?

A

Adrenaline
Noradrenaline
Thyroxine

56
Q

Where are the central thermoreceptors located?

A

In the hypothalamus and abdominal organs

57
Q

Where are the peripheral thermoreceptors located?

A

In the skin

58
Q

What are the 3 effectors in the negative feedback of temperature control?

A

Skeletal muscles
Skin arterioles
Sweat glands

59
Q

What does the hypothalamus act as?

A

The body’s thermostat (maintains the temperature at a set point)

60
Q

What is the posterior hypothalamic centre activated by?

A

The cold

61
Q

What is the anterior hypothalamic centre activated by?

A

The warmth

62
Q

What 4 things does the hypothalamus have neural connections with?

A

The limbic system
The cerebral cortex
The motor neurons - control skeletal muscles
The sympathetic nervous system

63
Q

What acts as an endogenous pyrogen, in relation to a fever?

A

Chemicals released from macrophages in response to infection or inflammation

64
Q

What do endogenous pyrogens do and name one?

A

Interleukins

Stimulate the release of prostaglandins in the hypothalamus

65
Q

What do the prostaglandins act on and what does this do?

A

They act on the hypothalamic thermo-regulatory centre to reset the thermostat at a higher temperature

66
Q

What 2 things would restore the hypothalamic set point to normal i.e. reduce it?

A

Stop or reduce the pyrogen release

Decrease or cease the synthesis of prostaglandins

JL Principles (12 decks)

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