Cardiovascular Physiology Flashcards
What are the four chambers of the heart?
Right atrium (RA): Receives deoxygenated blood from the body (via vena cava)
Right ventricle (RV): Pumps blood to lungs (via pulmonary artery)
Left atrium (LA): Receives oxygenated blood from lungs (via pulmonary veins)
Left ventricle (LV): Pumps oxygenated blood to body (via aorta)
What are the four heart valves & their functions?
π΅ Atrioventricular (AV) valves (separate atria from ventricles)
Tricuspid valve: Between RA & RV
Mitral (bicuspid) valve: Between LA & LV
π’ Semilunar valves (prevent backflow into ventricles)
Pulmonary valve: Between RV & pulmonary artery
Aortic valve: Between LV & aorta
Which major veins return blood to the heart?
Superior vena cava (SVC): Drains blood from upper body into RA
Inferior vena cava (IVC): Drains blood from lower body into RA
Pulmonary veins: Bring oxygenated blood from lungs into LA
Which major arteries carry blood away from the heart?
Pulmonary artery: Carries deoxygenated blood to lungs (only artery with deoxygenated blood)
Aorta: Carries oxygenated blood to the body
What is the coronary circulation?
The heartβs own blood supply via coronary arteries & veins
What are the major coronary arteries?
Left coronary artery (LCA) β branches into:
Left anterior descending (LAD): Feeds anterior LV & septum
Circumflex artery (LCX): Feeds LA & lateral LV
Right coronary artery (RCA): Feeds RA, RV, SA & AV nodes
What are the major coronary veins?
Great cardiac vein: Runs alongside LAD
Middle cardiac vein: Drains posterior heart
Small cardiac vein: Drains RV
Coronary sinus: Main drainage, empties into RA
What happens when coronary arteries are blocked?
Myocardial infarction (MI) due to ischemia (lack of oxygen)
What are the key structural features of cardiac muscle?
Striated, short-branched cells, uninucleate, intercalated discs, larger T-tubules over Z-discs
What is the role of intercalated discs?
Allow electrical & mechanical coupling between cells for synchronous contraction
What makes up the intrinsic conduction system?
Pacemaker cells & conduction pathways coordinating atrial & ventricular contraction
Why do pacemaker cells have an unstable membrane potential?
Due to If (funny) channels, which allow slow Na+ influx & K+ efflux, leading to spontaneous depolarization
What are the phases of pacemaker potential?
1οΈβ£ Slow depolarization (-60mV β -40mV) via If Na+ channels
2οΈβ£ Threshold reached (-40mV) β Ca2+ influx causes depolarization
3οΈβ£ Repolarization β K+ channels open, K+ efflux
ow does sympathetic stimulation affect pacemaker cells?
Noradrenaline & adrenaline bind to Ξ²1 receptors, increasing If channel activity, leading to faster depolarization & increased HR
How does parasympathetic stimulation affect pacemaker cells?
ACh binds to muscarinic receptors, increasing K+ permeability & decreasing Ca2+ influx, causing hyperpolarization & slower HR
How does the action potential of contractile myocardial cells differ from skeletal muscle?
Plateau phase (phase 2) in cardiac cells prevents tetanus, ensuring proper relaxation between beats
What are the phases of a myocardial action potential?
Phase 4: Resting (-90mV)
Phase 0: Rapid depolarization (Na+ influx)
Phase 1: Initial repolarization (K+ efflux)
Phase 2: Plateau (Ca2+ influx via L-type channels)
Phase 3: Repolarization (Ca2+ channels close, K+ efflux)
What is calcium-induced calcium release?
Ca2+ enters via L-type channels, triggering Ca2+ release from SR, leading to contraction
How does Ξ²1 receptor activation affect contraction?
Increases Ca2+ influx via L-type channels, enhancing SR Ca2+ release & contractility
What are the phases of the cardiac cycle?
1οΈβ£ Rest (End Diastole): Blood fills atria & ventricles
2οΈβ£ Atrial Systole: Atria contract β complete ventricular filling
3οΈβ£ Isovolumetric Contraction: AV valves close (π βlubβ)
4οΈβ£ Ventricular Ejection: Semilunar valves open β blood ejected
5οΈβ£ Isovolumetric Relaxation: Semilunar valves close (π βdupβ)
What causes the first and second heart sounds?
β
Lub (S1): Closure of AV valves (mitral & tricuspid)
β
Dup (S2): Closure of semilunar valves (aortic & pulmonary)
What is the equation for cardiac output (CO)?
CO = Stroke Volume (SV) Γ Heart Rate (HR)
How does the autonomic nervous system regulate CO?
β
Sympathetic: β HR (chronotropic), β conduction speed (dromotropic), β contractility (inotropic)
β
Parasympathetic: β HR, β conduction speed, β contractility
What is the Frank-Starling Law?
β Increased preload (ventricular filling) = increased stroke volume, due to better actin-myosin overlap
What does the Frank-Starling Law state?
β The more the heart fills (preload), the stronger the contraction β β Stroke Volume (SV)
How does increased preload affect stroke volume?
β More blood returning to the heart (venous return) β more stretch on ventricular walls
Better overlap of actin & myosin filaments
Stronger contraction β β SV
What factors increase preload?
Increased venous return (exercise, IV fluids)
Slower HR (more filling time)
What factors decrease preload?
Blood loss (hypovolemia)
Dehydration
Tachycardia (less filling time)
How does afterload affect stroke volume?
Afterload = resistance the heart must overcome to eject blood
β Afterload (e.g., hypertension, aortic stenosis) β β SV
β Afterload (e.g., vasodilation) β β SV
What is the equation for Mean Arterial Pressure (MAP)?
MAP = CO Γ SVR (Systemic Vascular Resistance)
How do baroreceptors regulate BP?
Located in carotid sinus & aortic arch, sense stretch, send signals to brainstem to adjust HR & vessel tone
What hormones are involved in long-term BP control?
β Renin-Angiotensin-Aldosterone System (RAAS):
Renin β Angiotensin II: Vasoconstriction
Aldosterone: Na+ & water retention
β
ADH (vasopressin): Increases water retention
β
Atrial Natriuretic Peptide (ANP): Promotes Na+ excretion
Where are baroreceptors located?
β Carotid sinus (internal carotid artery) & aortic arch β most sensitive to BP changes
How do baroreceptors sense BP?
β Stretch receptors that fire action potentials based on arterial wall stretch
What happens when BP increases?
β More stretch β β baroreceptor firing β stimulates parasympathetic NS (PNS)
β HR (bradycardia)
β contractility
β vasoconstriction β β BP
What happens when BP drops?
β Less stretch β β baroreceptor firing β stimulates sympathetic NS (SNS)
β HR (tachycardia)
β contractility
β vasoconstriction β β BP
What are the two types of baroreceptors?
Type A: High sensitivity, rapid response
Type C: Lower sensitivity, higher threshold, better at handling high BP
Are there other stretch receptors?
β Yes!
Coronary artery baroreceptors β More sensitive than carotid & aortic ones
Veno-atrial mechanoreceptors β Detect blood volume changes (e.g., when lying down)
Unmyelinated mechanoreceptors β Found in ventricles (during systole) & atria (during inspiration)
What triggers RAAS activation?
Low BP (sensed by kidney baroreceptors)
Low Na+ levels
SNS activation (Ξ²1 receptors on kidneys)
What is the function of RAAS?
Regulates BP & blood volume via vasoconstriction & sodium retention
What are the steps of RAAS?
1οΈβ£ Renin release (kidneys) due to low BP
2οΈβ£ Renin converts angiotensinogen (liver) β angiotensin I
3οΈβ£ ACE (lungs) converts angiotensin I β angiotensin II
4οΈβ£ Angiotensin II effects:
Vasoconstriction β β BP
Aldosterone release (adrenal glands) β Na+ & water retention β β blood volume
ADH release (posterior pituitary) β β water reabsorption
How does RAAS affect long-term BP control?
Increases blood volume & vascular resistance, maintaining BP in hypovolemia or dehydration
What is shock?
β Acute failure of the CV system to perfuse tissues adequately
What are the types of shock?
Hypovolemic: Blood/fluid loss (hemorrhage, burns)
Distributive: Vasodilation (sepsis, anaphylaxis)
Cardiogenic: Heart pump failure (MI, myocarditis)
Obstructive: Blockage (PE, tamponade, tension pneumothorax)
What happens in response to blood loss?
β Baroreceptors & chemoreceptors activate:
β HR, vasoconstriction, RAAS activation
Release of vasopressin, angiotensin II
Increased respiration due to hypoxia
