Unit 4 - Part 1 Flashcards
Pericardium
A tough membranous sac surrounding the heart. It is made up of two layers with a small amount of fluid between them that acts as lubricant (in the pericardial cavity).
Vena Cava
Superior and inferior. Brings unoxygenated blood back to the heart into the right atrium.
Left Ventricle
Lower left chamber. Receives blood from the left atrium and sends it to the body via the aorta (systemic circuit).
Aorta
Transports highly oxygenated blood away from the heart in the systemic circuit. Monitors blood pressure to the body.
Semilunar Valves
Aortic and pulmonary valves. Just inside the aorta and pulmonary trunk to prevent backflow into the ventricles. Do not need cords to brace them because of their shape and function.
SA Node
Sinoatrial node. Located in the right atrium, near the superior vena cava. It spontaneously generates action potentials without input from the nervous system.
AV Node
Atrioventricular node. Is the only pathway where the action potential from the atria can travel to the ventricles.
Purkinje Fibres
Transmits signals very rapidly around the ventricles of the heart.
Artery
Transports blood away from the heart. Thick walls of muscle and elastic material to withstand high pressure.
Arteriole
The smallest arteries.
Capillary
Smallest blood vessel with no smooth muscle. Involved in exchange of material.
Venule
The smallest veins. Little smooth muscle.
Vein
Transports blood back to the heart at low pressure. More smooth muscle than venule but less than an artery.
Baroreceptors
Stretch sensitive mechanoreceptors found in vessel walls of the carotid artery and aorta.
Diastolic Pressure
Time when the ventricle relaxes (lowest arterial pressure).
Systolic Pressure
Time when the heart is contracting (highest arterial pressure).
Myocardial Infarction
Heart attack. Caused from a lack of blood supply to the heart.
Left Atrium
Upper left chamber. Receives blood from the pulmonary veins and sends it to the left ventricle.
Pulmonary Trunk
Brings unoxygenated blood to the pulmonary arteries from the right ventricle to go the lungs.
AV Valves
Atrioventricular valves. Tricuspid and bicuspid/mitral valves. Attached on the ventricular side to collagenous cords that holds the valves and prevents them from being pushed back into the atrium.
Bundle of His
The AV bundle. Where the action potential goes after the AV node.
Bundle Branches
The two pathways that separate from the bundle of His.
Systole
Contraction.
Diastole
Relaxation.
End-Diastolic Volume (EDV)
Maximum volume in the ventricle (end of ventricular filling).
End-Systolic Volume (ESV)
Minimum volume in the ventricle (end of ventricular contraction).
Stroke Volume
EDV - ESV
Vasodilation
Widening of the blood vessel.
Vasoconstriction
Narrowing of the blood vessel.
Blood Pressure
How much force blood exerts on the blood vessels.
Mean Arterial Pressure (MAP)
The average arterial pressure throughout one cardiac cycle.
Peripheral Resistance
The constricting and dilating of blood vessels to decrease or generate flow.
Diffusion
The spontaneous movement of molecules down their respective gradients.
Bulk Flow
The movement of a mass amount of molecules due to the presence of a gradient.
Pressure Gradients
Flows from high pressure to low pressure.
Systemic Circulation
Oxygenated blood leaves the heart via the aorta, goes around the body, becomes deoxygenated, and returns to the heart via the superior and inferior vena cava.
Pulmonary Circulation
Deoxygenated blood leaves the heart via the pulmonary trunk/arteries, goes to the lungs, becomes oxygenated, and returns to the heart via the pulmonary veins.
Contractile Cell Action Potentials
Phase 4 - Resting Membrane Potential (-90 mV).
Phase 0 - Depolarization (the AP opens voltage-gated Na+ channels causing a rapid increase in membrane Na+ permeability (close again)).
Phase 1 - Initial Repolarization (open fast K+ channels allow initial repolarization).
Phase 2 - The Plateau (initial depolarization triggers voltage-gated Ca^2+ channels to slowly open causing an increase in Ca^2+ permeability and the fast K+ channels close).
Phase 3 - Rapid Repolarization (the Ca^2+ channels close and the slow voltage-gated K+ channels open (triggered by the initial depolarization) and the resting stage ion permeability is restored (Phase 4)).
Pacemaker Action Potentials
1) If channels close and Ca^2+ channels open. Continued depolarization. When threshold is reached, many Ca^2+ channels open and there is a rapid influx of Ca^2+ (steep depolarization phase of action potential).
2) At end of depolarization the Ca^2+ channels close and K+ channels open slowly. Efflux of K+ causes repolarization.
ECG/EKG
Records the electrical activity of the heart at the surface of the skin using electrodes. Measures the voltage differentials occurring during the cardiac cycle (a single contraction-relaxation of the mechanical events). Nowadays, 12 leads are used to give information about different regions of the heart.
Cardiac Cycle
The period from one heartbeat to the next and has two phases, systole and diastole.
We Require From the Environment
1) Nutrients
2) Oxygen
Components of the Cardiovascular System
1) Heart (pump)
2) Blood Vessels (vasculature)
3) Blood Cells and Plasma (fluid)
Coronary Arteries
Nourish the heart muscle (supplies blood to the heart).
Endocardium
A thin layer of epithelial cells that lines the chambers of the heart.
Myocardium
Heart muscle.
Epicardium
Epithelial cells that are attached to the outer side of heart muscle.
Pericardial Cavity
Filled with fluid that acts as a lubricant.
Parietal Layer of Pericardium
Between the pericardial cavity and the connective tissue.
Fibrous Pericardium
Connective tissue on the outside of the heart. Not part of the pericardium.
Base
The top of the heart.
Apex
The bottom point of the heart.
Right Atrium
Upper right chamber. Receives blood from the vena cava and sends it to the right ventricle.
Right Ventricle
Lower right chamber. Receives blood from the right atrium and sends it to the lungs via the pulmonary trunk and arteries (pulmonary circuit).
Valves
Ensures flow is unidirectional (one-way).
Pacemaker/Autorhythmic Cells
Have an unstable membrane potential that slowly drifts upwards from a starting point of -60 mV (pacemaker potential) until it reaches threshold and initiates an action potential (never at rest). It initiates the electrical excitation of the heart. Depolarization spreads to neighbouring cardiac cells via gap junctions in the intercalated discs.
If Channels
Funny channels. Are permeable to K+ and Na+.
Norepinephrine (NE)
Released from sympathetic neurons and binds to β1 adrenergic receptors resulting in the release of cAMP through the signalling pathway which binds to open If channels. The channels stay open longer, increasing the permeability to Na+ and Ca^2+ which increases the depolarization rate which increases the rate of action potentials (heart rate increases).
Epinephrine (E)
Released from the adrenal medulla and binds to β1 adrenergic receptors resulting in the release of cAMP through the signalling pathway which binds to open If channels. The channels stay open longer, increasing the permeability to Na+ and Ca^2+ which increases the depolarization rate which increases the rate of action potentials (heart rate increases).
Acetylcholine (ACh)
Released from parasympathetic neurons and binds to muscarinic receptors resulting in increase K+ permeability (not by funny channels, by adjacent cells) which hyperpolarizes the cell (pacemaker potential starts at more negative value therefore it takes longer to reach threshold potential (heart rate decreases)).
Events of Cardiac Conduction
1) Action potential is fired from the SA node and spreads to adjacent cells.
2) Rapid spread through cells of internodal pathway. The spread is slower through contractile cells of the atrium.
3) Signal is passed through the AV node only at the AV junction. A layer of fibrous connective tissue (fibrous skeleton of the heart) acts as an insulator preventing electrical signals from the atrium to travel to the ventricle directly. The signal is slightly delayed by the AV node to make sure that the atria have finished contracting.
4) Signal is carried to the bottom of the heart (apex) through bundles of His.
5) Bundle of His divides into left and right branches and goes to the Purkinje fibres which transmits the signals very rapidly to ensure that all the contractile cells at the apex contract together.
Events of Cardiac Contraction Pathway
SA Node → Internodal Pathway → AV Node → AV Bundle/Bundle of His → Bundle Branches → Purkinje Fibers
Einthoven’s Triangle
Uses 3 leads to give information about the heart.
Lead 1
Horizontal, right to left (negative to positive).
P Wave
Atrial depolarization.
QRS Complex
Ventricular depolarization.
T Wave
Ventricular repolarization.
Segments
Sections of baseline between two waves. Mechanical events (lag slightly behind electrical events).
PR Segment
Atrial contraction.
ST Segment
Ventricular contraction (just after Q wave).
Phases of the Cardiac Cycle
1) Late Diastole - atria and ventricles are relaxed (semilunar valves are closed and AV valves are open allowing blood to enter the ventricles passively).
2) Atrial Systole - atria contracts and ventricles are relaxed (semilunar valves are closed and AV valves are open so a small amount of blood enters the ventricles).
3) Isovolumetric Ventricular Contraction - ventricles contract (semilunar and AV valves are closed so the volume stays the same).
4) Ventricular Ejection - semilunar valves open and AV valves close (blood is ejected from the heart).
5) Isovolumetric Ventricular Relaxation - semilunar and AV valves are closed.
6) Go back to Late Diastole and repeat.
Lub
The first sound of a heart beat caused by the closing of AV valves during isovolumetric ventricular contraction.
Dub
The second sound of a heart beat caused by the closing of the semilunar valves during isovolumetric ventricular relaxation.
Cardiac Output Formula
Heart Rate x Stroke Volume
Cardiac Output
The amount of blood pumped by the heart in one minute.
Factors Influencing Heart Rate
1) Parasympathetic Stimulation (releases ACh and decreases heart rate)
2) Sympathetic Stimulation (releases NE and increases heart rate)
3) Plasma Epinephrine (from adrenal medulla and increases heart rate)
Factors Influencing Stroke Volume
1) Parasympathetic Stimulation (decreases contractility)
2) Sympathetic Stimulation (increases contractility)
3) Plasma Epinephrine (increases contractility)
4) Increased End-Diastolic Volume (increases stroke volume)
Blood Vessels
Hollow tubes made up of lumen (central cavity) and a wall (made up of multiple layers).
Blood Vessel Wall Structure
1) Inner Lining (endothelium made up of endothelial cells).
2) Elastic Connective Tissue.
3) Vascular Smooth Muscle (controls vasoconstriction and vasodilation).
4) Fibrous Connective Tissue.
Blood Flow
Is directly proportional to the pressure gradient and inversely proportional to resistance. Occurs from high pressure to low pressure.
Factors That Influence Blood Flow
1) Myogenic Autoregulation (vascular smooth muscle) (stretch receptors in wall of arterioles when activated cause vasoconstriction (controls pressure)).
2) Paracrine Hormones (released from vascular endothelium and tissues. Causes vasodilation or vasoconstriction).
3) Innervation By Sympathetic Division of Autonomic Nervous System (norepinephrine, binds to alpha receptors causing vasoconstriction and epinephrine, binds to alpha receptors which reinforces vasoconstriction).
4) Hormonal Signals Via Circulating Epinephrine (binds to β2 receptors. Found only in vascular smooth muscle of heart, liver, and skeletal muscle which causes vasodilation).
Friction
The force that resists relative motion between two bodies in contact.
Sphygmomanometry
The use of a blood pressure cuff and a stethoscope to estimate the blood pressure.
Steps to Take Blood Pressure
1) Inflate cuff (cuts off blood flow).
2) Cuff is gradually deflated. When pressure in cuff is equal to systolic pressure, blood will start to flow.
3) Turbulent flow results in sound. Korotkoff sound (first initial sound) (with each heartbeat).
4) Cuff pressure is further reduced.
5) Eventally all sound will cease because flow is no longer turbulent (diastolic pressure).
Mean Arterial Pressure (MAP) Formula
Diastolic Pressure + 1/3 x (Systolic Pressure - Diastolic Pressure)
Factors Affecting Mean Arterial Pressure
1) Cardiac Output
2) Changes in Blood Volume
3) Peripheral Resistance (vasodilation and vasoconstriction)
Carotid Artery
Monitors blood pressure to the brain.
Waves
Deflections above or below the baseline that show electrical events.
