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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
Characteristics of Venous Return (5)
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
what are the 3 factors that influence pressure, and therefore blood flow
1. Cardiac Output (rapid, short term) 2. Peripheral resistance (TPR) (rapid, short term) 3. Blood Volume (slower, long term regulation)
27
define cardiac output
CO = stroke volume x heart rate
28
how does cardiac output influence BP
increased Sv or HR = increased CO = increased BP decreased SV or HR = decrease CO = decreased BP
29
how does Peripheral Resistance (TPR) influence BP
- vasoconstriction = increased resistance = increased BP but decreased BF - vasodilation = decreased resistance = decreased Bp and increased BF
30
how is blood flow maintained
more pressure is applied which is generated by the heart
31
how does blood volume influence BP
- controlled by renal and endocrine mechanisms - increased BV = more blood pushing on vessel walls = increased BP vice versa
32
List the 4 different ways blood pressure is regulated
1. Autoreguation - occurs within tissues 2. Neural Regulation - involves the cardiovascular centres and the ANS 3. Renal Mechanisms 4. Endocrine Regulation
33
describe regulation in context to regulating blood pressure
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
describe how neural regulation regulates blood pressure
cardiovascular centres in the medulla oblongata contain 3 centres: 1. Cardioinhibitory centre 2. Cardioacceleratory centre 3. Vasomotor centre
35
Neural Regulation - Cardioinhibitory Centre
- provides parasympathetic input into the SA and AV nodes | - slows heart rate
36
Neural Regulation - Cardioacceleratory Centre
- provides sympathetic input to the SA and AV nodes and ventricular myocardium - increases heart rate - increases force of contraction and thus SV
37
Neural Regulation - Vasomotor Centre
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
Renal mechanisms and their influence on the regulation of blood pressure
1. Direct Mechanism | 2. Indirect mechanism
39
Renal Mechanism - Direct Mechanism
- 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
Renal Mechanism - Indirect Mechanism
- 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
Endocrine regulation of blood pressure
hormones that increase BP - adrenalin and noradrenalin - angiotensin II hormones that decrease BP - ANP
42
location of baroreceptors
- carotid sinuses - aortic arch - walls of most large arteries in the neck and thorax
43
role of carotid sinus reflex
monitors and protects blood flow to the brain
44
role of aortic arch baroreceptor reflex
monitors and maintains blood flow into the systemic circuit

BMA - SEMESTER 2 (8 decks)

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