OIA1004 (TERMS) CVS III

Blood Flow

Volume of blood passing a point per unit time (ml/min)

Blood Velocity

Displacement of blood in circulation (cm/s)

Pressure Gradient

Force pushing liquid through a vessel

Resistance

Opposition to blood flow in vessels

Closed System

Cardiovascular system with no openings

Mean Arterial Pressure

Average pressure in arteries driving blood flow

Pressure Drop

Decrease in pressure from arteries to veins

Ohm's Law

Flow = Pressure gradient / Resistance

Total Peripheral Resistance (TPR)

Sum of all vascular resistance in systemic circulation

Poiseuille's Law

Flow = ΔP . π r^4 / 8ηl

Vasoconstriction

Decrease in vessel radius, increasing resistance

Vasodilation

Increase in vessel radius, decreasing resistance

Arterioles

Small arteries with high resistance to flow

Blood Viscosity

Thickness of blood affecting flow resistance

Length of Blood Vessel

Longer vessels increase resistance to flow

Radius of Blood Vessel

Critical factor affecting resistance to flow

Fluid Dynamics

Study of fluid flow principles in physiology

Systemic Circulation

Flow of blood from heart to body and back

Pulmonary Circulation

Flow of blood from heart to lungs and back

Parallel Flow

Independent regulation of blood flow to organs

Pressure Variation

Changes in blood pressure throughout circulation

Cardiovascular System

System comprising heart and blood vessels

Bulk Flow

Movement of blood driven by pressure gradients

Circulatory System

Network of vessels transporting blood

Arteriolar tone

Partially contracted state of arterioles at rest

Vasodilation (function)

Decreased contraction (increased radius)

Blood flow

Defined as the volume of blood which passes a given point in the circulation per unit time, in ml/min

Blood velocity

Displacement of blood from point of the circulation to another in cm/s

Velocity of blood flow

Inversely related to the cross sectional area of blood vessels

Cross sectional area of blood vessels

Highest in capillaries and lowest in aorta

Mean Arterial Pressure (MAP)

Average pressure in the aorta throughout the cardiac cycle

Cardiac output (CO)

Volume of blood flowing through systemic circuit per minute

Pressure gradient (ΔP)

The force that drives the flow (equals pressure difference across the system)

Total peripheral resistance (TPR)

Combined resistance of the systemic organs plus all blood vessels leading to and from them

Blood pressure (BP)

Refers to the pressure in the arteries/aorta exerted by the blood in the inner wall of the blood vessels

Systolic pressure

Achieved during ventricular contraction, approximately 120-140 mmHg in a healthy resting adult

Diastolic pressure

Achieved during relaxation phase of cardiac cycle, approximately 70-90 mmHg in a healthy resting adult

Pulse pressure

Systolic BP - diastolic BP

MAP calculation

MAP = 1/3 (systolic BP - diastolic BP) + diastolic BP

Blood pressure regulation factors

BP = Cardiac output (CO) x Total peripheral resistance (TPR)

Baroreceptor reflex mechanism

High pressure sensors that respond to stretch caused by blood pressure

Afferent innervation

Sensory impulses from the aortic arch baroreceptors travel in the vagus nerve

Cardiovascular Centre (CVC)

Located in the medulla oblongata, integrates impulse from other areas in the brain

Nucleus of tractus solitaries (NTS)

Receives impulse from the vagus and glossopharyngeal nerves

Cardio-Acceleratory Centre (CAC)

Transmits excitatory impulse to the heart and blood vessel via the sympathetic nerves

Cardio-Inhibitory Centre (CIC)

Transmits inhibitory impulse to the heart via the parasympathetic nerve

Vasomotor centre

Inhibited by increased blood pressure, reducing sympathetic vasoconstrictor tone

Parasympathetic activity

Innervates SA node and AV node, releasing acetylcholine which acts on muscarinic receptors

Acetylcholine

Neurotransmitter that activates muscarinic receptors.

Muscarinic receptors

Receptors that mediate parasympathetic effects.

Heart rate (HR)

Number of heartbeats per minute.

Venodilation

Widening of veins, decreases venous return (VR).

AV nodal delay

Increased delay in electrical conduction through the AV node.

Sympathetic discharge

Nerve signals that increase heart and vessel activity.

Contractility

Strength of heart muscle contractions.

Stroke volume (SV)

Amount of blood ejected by the heart per beat.

Baroreceptor reflex

Response to changes in blood pressure via baroreceptors.

Nucleus tractus solitarius (NTS)

Brain region processing baroreceptor signals.

Cardioaccelerator center (CAC)

Stimulates sympathetic activity to increase heart rate.

Vasomotor center

Regulates blood vessel constriction and dilation.

Noradrenaline

Neurotransmitter that stimulates sympathetic responses.

β1-adrenoreceptors

Receptors that increase heart rate and contractility.

Renin-angiotensin-aldosterone system (RAAS)

Hormonal system regulating blood pressure and volume.

Atrial Natriuretic Peptide (ANP)

Hormone that decreases blood volume and pressure.

Juxtaglomerular cells

Cells in kidneys that release renin.

Angiotensin II

Hormone that increases blood pressure and volume.

Aldosterone

Hormone that promotes sodium and water retention.

Antidiuretic hormone (ADH)

Hormone that increases water reabsorption in kidneys.

Blood volume regulation

Determines venous pressure and cardiac output.

Short-term blood pressure regulation

Immediate response to blood pressure changes.

Long-term blood pressure regulation

Regulates blood pressure through fluid balance.