haemodynamics Flashcards
what is haemodynamics?
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
what is the function of circulation?
Function of circulation - to supply nutrients to tissues and remove waste products
Local blood flow is controlled by ______ which function like a tap
Local blood flow is controlled by arterioles which function like a tap
Arteries transport blood under ____ pressure to tissues
Arteries transport blood under HIGH pressure to tissues
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.
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.
____
arterioles are a site of ____ resistance
arterioles are a site of high resistance
Capillaries exchange fluids, nutrients, gases, and electrolytes with __________ _____ in local tissues, and have the highest cross-sectional area
Capillaries exchange fluids, nutrients, gases, and electrolytes with INTERSTITIAL FLUID in local tissues, and have the highest cross-sectional area
Venules collect blood from _______
Venules collect blood from capillaries
Veins return blood to the ____ and act as a _____ of blood
Veins return blood to the heart and act as a reservoir of blood
Why do veins act as a natural reservoir of blood?
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.
what is blood flow?
Flow (rate)= volume/time
Blood flow is the volume of blood that flows through a vessel or an organ over some period of time
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.
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.
Flow is directly proportional to ____________ and
inversely proportional to _________
Flow is directly proportional to PRESSURE GRADIENT and inversely proportional to RESISTANCE
what is the equation linking flow, pressure gradient and resistance
flow = pressure gradient/ resistance
What are the 2 types of flow in the circulation? Describe the difference
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
- What causes the flow to become turbulent?
The total blood flow out of the heart (liters/min) is the ________
The total blood flow out of the heart (liters/min) is the cardiac output.
State the relationship between stroke volume, heart rate and cardiac output
Cardiac output = Heart Rate x Stroke Volume
what are factors that affect heart rate
*atrial reflex
* autonomic innervation
*hormones
*heart rate
what are factors affecting stroke volume
*preload
*contractility
*afterload
what is blood pressure
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
State equation linking area, force and pressure
Pressure = force/area
What is a normal average systolic and diastolic blood pressure. How do we work out pulse pressure
- 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
pulse pressure is ______ _____ to stroke volume and _____ ____ to arterial compliance
pulse pressure is DIRECTLY PROPORTIONAL to stroke volume and INVERSELY PROPORTIONAL to arterial compliance
what is a korotkoff sound
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.
