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BMA - SEMESTER 2 > Module 3 > Flashcards

Module 3 Flashcards

1
Q

what is the overall purpose of the circulatory system

A

to provide adequate blood flow to all tissues/organs according to their immediate needs

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2
Q

define blood flow

A

the volume of blood flowing through a vessel, organ or the entire circulation

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3
Q

what 2 factors determine blood flow

A
  1. blood pressure

2. resistance

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4
Q

define blood pressure

A

the force exerted on a vessel wall by the blood in that vessel

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5
Q

define resistance

A

a measure of the amount of friction blood encounters as it flows through a vessel
(opposition to blood flow)

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6
Q

what are the 3 sources that affects total peripheral resistance (TPR)

A
  • blood viscosity
  • total blood vessel length
  • blood vessel diameter
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7
Q

TPR: Viscosity

A

the thickness of fluid

  • increase in RBC increases viscosity
  • dehydration increases viscosity `
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8
Q

TPR: Vessel Length

A

resistance to flow increases as vessel length increases

e.g. easier to drink a milkshake through shorter straw

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9
Q

TPR: Vessel Diameter

A

the amount of contact between 2 surfaces determines friction

more contact blood has with the walls = more friction = more resistance to blood flow

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10
Q

what does increased vessel diameter result in

A

decreased contact between blood and vessel walls = decreased friction = decreased resistance to blood flow

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11
Q

what occurs as a result of vasoconstriction

A

decrease in daimeter = increases resistance = decreases blood flow

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12
Q

what occurs as a result of vasodilation

A

increases diameter = decreases resistance = increases blood flow

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13
Q

equation for blood flow

A

F= P/R

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14
Q

systemic blood pressure - when does the steepest drop in pressure occur and why

A
  • arterioles

- resistance to blood flow = greatest

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15
Q

What are the 2 factors that reflects arterial pressure

A
  1. how much elastic fibres can be stretched

2. The volume of blood forced into the elastic arteries by ventricular contraction

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16
Q

define systolic pressure

A

peak pressure generated in the large arteries when the ventricles contract

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17
Q

define diastolic pressure

A

pressure in the large arteries during ventricular relaxation

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18
Q

formula for pulse pressure

A

pp= systolic pressure - diastolic pressure

19
Q

define mean arterial pressure (MAP)

A

the pressure that propels blood through the vessels

20
Q

formula for MAP

A

MAP= diastolic pressure +(1/3 pulse pressure)

or
Map = COxR

21
Q

why does an increase in CO result in higher BP

A

because an increase in CO pushes more blood into the arteries = increased MAP

22
Q

what is the cause of chronic hypertension

A

sustained systolic pressure > 140mmHg

23
Q

Why is thin capillary blood pressure required

A
  1. High pressure would damage thin walled, fragile capillaries
  2. Most capillaries are very permeable so low pressure is adequate to fluid exchange with tissues
24
Q

Describe venous Blood Pressure

A
  • constant at 15mmHg
  • small pressure gradient
  • too low to provide adequate census return to the heart
25
Q

Characteristics of Venous Return (5)

A
  1. Valves - prevent blood back flow; shifts blood in small volumes
  2. Muscular Pump - contracts squeezed veins and pushes blood to heart
  3. Respiratory Pump - pressure changes during breathing to help blood move toward the heart by squeezing abdominal veins as thoracic veins expand
  4. Pulsation - in nearby arteries
  5. Venoconstriction - pf tunica media under sympathetic control
26
Q

what are the 3 factors that influence pressure, and therefore blood flow

A
  1. Cardiac Output (rapid, short term)
  2. Peripheral resistance (TPR) (rapid, short term)
  3. Blood Volume (slower, long term regulation)
27
Q

define cardiac output

A

CO = stroke volume x heart rate

28
Q

how does cardiac output influence BP

A

increased Sv or HR = increased CO = increased BP

decreased SV or HR = decrease CO = decreased BP

29
Q

how does Peripheral Resistance (TPR) influence BP

A
  • vasoconstriction = increased resistance = increased BP but decreased BF
  • vasodilation = decreased resistance = decreased Bp and increased BF
30
Q

how is blood flow maintained

A

more pressure is applied which is generated by the heart

31
Q

how does blood volume influence BP

A
  • controlled by renal and endocrine mechanisms
  • increased BV = more blood pushing on vessel walls = increased BP

vice versa

32
Q

List the 4 different ways blood pressure is regulated

A
  1. Autoreguation - occurs within tissues
  2. Neural Regulation - involves the cardiovascular centres and the ANS
  3. Renal Mechanisms
  4. Endocrine Regulation
33
Q

describe regulation in context to regulating blood pressure

A

tissues can regulate their own blood flow + pressure in response to local conditions by:

  1. altering arteriole diameter
  2. opening/Closing of pre capillary sphincters
34
Q

describe how neural regulation regulates blood pressure

A

cardiovascular centres in the medulla oblongata contain 3 centres:

  1. Cardioinhibitory centre
  2. Cardioacceleratory centre
  3. Vasomotor centre
35
Q

Neural Regulation - Cardioinhibitory Centre

A
  • provides parasympathetic input into the SA and AV nodes

- slows heart rate

36
Q

Neural Regulation - Cardioacceleratory Centre

A
  • provides sympathetic input to the SA and AV nodes and ventricular myocardium
  • increases heart rate
  • increases force of contraction and thus SV
37
Q

Neural Regulation - Vasomotor Centre

A

Sympathetic vasomotor fires to the smooth muscle of the arterioles = change in vasomotor tone = change in vessel diameter

  • increased sympathetic activity = increase in vasomotor tone = vasoconstriction

vice versa

38
Q

Renal mechanisms and their influence on the regulation of blood pressure

A
  1. Direct Mechanism

2. Indirect mechanism

39
Q

Renal Mechanism - Direct Mechanism

A
  • the rate of urine formation is determined by BP

increased BP = increased bf to kidneys = increased filtration = increased urine = decreased BV and BP

vice versa

40
Q

Renal Mechanism - Indirect Mechanism

A
  • involves hormones
    (Renin Angioensins - Aldosterone SYstem = (RAAS)
  • stimulates vasoconstriction = increased R = increased BP
  • stimulates aldosterone = maintains/increases BV and thus BP
  • stimulates DH = maintains/increases BV and BP
41
Q

Endocrine regulation of blood pressure

A

hormones that increase BP

  • adrenalin and noradrenalin
  • angiotensin II

hormones that decrease BP

  • ANP
42
Q

location of baroreceptors

A
  • carotid sinuses
  • aortic arch
  • walls of most large arteries in the neck and thorax
43
Q

role of carotid sinus reflex

A

monitors and protects blood flow to the brain

44
Q

role of aortic arch baroreceptor reflex

A

monitors and maintains blood flow into the systemic circuit

BMA - SEMESTER 2 (8 decks)

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