haemodynamics

Question 1

what is haemodynamics?

Answer 1

Haemodynamics explains the physical laws that govern the flow of blood in the blood vessels
aka the dynamics of blood flow; study of the physical + physiological principles governing the movement of blood through the circulatory system

Question 2

what is the function of circulation?

Answer 2

Function of circulation - to supply nutrients to tissues and remove waste products

Question 3

Local blood flow is controlled by ______ which function like a tap

Answer 3

Local blood flow is controlled by arterioles which function like a tap

Question 4

Arteries transport blood under ____ pressure to tissues

Answer 4

Arteries transport blood under HIGH pressure to tissues

Question 5

Arterioles contribute to maintaining mean arterial pressure and tissue perfusion as they are the important site of __ ___ ____. By increasing or decreasing the ____, they also play a principal role in regulating blood flow in an organ or tissue-specific manner.

Answer 5

Arterioles contribute to maintaining mean arterial pressure and tissue perfusion as they are the important site of TOTAL PERIPHERAL RESISTANCE. By increasing or decreasing the DIAMETER, they also play a principal role in regulating blood flow in an organ or tissue-specific manner.

Question 6

____

arterioles are a site of ____ resistance

Answer 6

arterioles are a site of high resistance

Question 7

Capillaries exchange fluids, nutrients, gases, and electrolytes with __________ _____ in local tissues, and have the highest cross-sectional area

Answer 7

Capillaries exchange fluids, nutrients, gases, and electrolytes with INTERSTITIAL FLUID in local tissues, and have the highest cross-sectional area

Question 8

Venules collect blood from _______

Answer 8

Venules collect blood from capillaries

Question 9

Veins return blood to the ____ and act as a _____ of blood

Answer 9

Veins return blood to the heart and act as a reservoir of blood

Question 10

Why do veins act as a natural reservoir of blood?

Answer 10

Veins return blood to the heart and act as a reservoir of blood ;primary function of returning blood to the heart, veins are blood reservoirs, since systemic veins contain approximately 64% of blood volume at any given time. Their ability to hold this much blood is due to their high capacitance, that is, their capacity to distend (expand) readily to store a high volume of blood, even at a low pressure. The large lumens and relatively thin walls of veins make them far more distensible than arteries; thus, they are said to be capacitance vessels.

Question 11

what is blood flow?

Answer 11

Flow (rate)= volume/time
Blood flow is the volume of blood that flows through a vessel or an organ over some period of time

Question 12

Differences in blood pressure throughout the body keep blood flowing from high-pressure areas, like the arteries, to low-pressure areas, like the veins. This _________ is the main driving force for blood flow.

Answer 12

Differences in blood pressure throughout the body keep blood flowing from high-pressure areas, like the arteries, to low-pressure areas, like the veins. The PRESSURE GRADIENT is the main driving force for blood flow.

Question 13

Flow is directly proportional to ____________ and
inversely proportional to _________

Answer 13

Flow is directly proportional to PRESSURE GRADIENT and inversely proportional to RESISTANCE

Question 14

what is the equation linking flow, pressure gradient and resistance

Answer 14

flow = pressure gradient/ resistance

Question 15

What are the 2 types of flow in the circulation? Describe the difference

Answer 15

laminar blood flow + turbulent blood flow.
*Laminar blood flow: streamlined or smooth, when blood flows in parallel layers, without disruption. Laminar flow is prominently observed at low velocities.
- The layer with the highest velocity flows in the centre of the vessel lumen

• Turbulent blood flow: random and chaotic. There is mixing of the layers. creates murmurs and bruits
  
  • What causes the flow to become turbulent?
    -Increasing velocity
    -narrowing of vessel radius
    -decreasing viscosity of blood

Question 16

The total blood flow out of the heart (liters/min) is the ________

Answer 16

The total blood flow out of the heart (liters/min) is the cardiac output.

Question 17

State the relationship between stroke volume, heart rate and cardiac output

Answer 17

Cardiac output = Heart Rate x Stroke Volume

Question 18

what are factors that affect heart rate

Answer 18

*atrial reflex
* autonomic innervation
*hormones
*heart rate

Question 19

what are factors affecting stroke volume

Answer 19

*preload
*contractility
*afterload

Question 20

what is blood pressure

Answer 20

Blood pressure - force that the blood exerts on the surface area of the walls of the blood vessels
Differences in blood pressure throughout the body keep blood flowing from high-pressure areas to low-pressure areas

Question 21

State equation linking area, force and pressure

Answer 21

Pressure = force/area

Question 22

What is a normal average systolic and diastolic blood pressure. How do we work out pulse pressure

Answer 22

• Systolic blood pressure (SBP): pressure during systole Maximum pressure in arteries. Normally approx. 120mmHg
• Diastolic blood pressure (DBP): pressure during diastole. Minimum pressure in arteries. Normally approx. 80mmHg
  pulse pressure = difference between systolic + diastolic blood pressure

Question 23

pulse pressure is ______ _____ to stroke volume and _____ ____ to arterial compliance

Answer 23

pulse pressure is DIRECTLY PROPORTIONAL to stroke volume and INVERSELY PROPORTIONAL to arterial compliance

Question 24

what is a korotkoff sound

Answer 24

sounds detected by the stethoscope in the auscultatory blood pressure measurement, known as Korotkoff sounds, are used to define systalic (high value) and diastolic (low value) pressures inside the arterial system.

korotkoff sounds:
* Phase 1: sharp tapping. The first sound heard as the cuff pressure is released. This sound provides the systolic pressure reading.
* Phase 2: swishing/whooshing sound as the blood flows through blood vessels as the cuff is deflated.
* Phase 3: A thump (softer than phase 1). Intense thumping sounds that are softer than phase 1 as the blood flows through the artery but the cuff pressure is still inflated to occlude flow during diastole.
* Phase 4: A softer, blowing, muffled sound that fades as the cuff pressure is released. a.k.a the first diastolic reading.
Phase 5: Silence occurs when the cuff pressure is released enough to allow normal blood flow. a.k.a second diastolic reading.