Cardiovascular System Flashcards
What is the heart?
A closed system that pumps blood and has blood vessels that circulate blood.
What does the heart do?
Deliver oxygen and nutrients + removes CO2 and other waste products
*Where is the heart?
- Thorax between the lungs
- Pointed apex towards the left hip
- About size of the fist
- <450g
*What are the main structures of the heart?
Vena Cava (IN) Atrium (Right) Ventricle (Right) Arteries (Pulmonary) LUNGS Veins (4 Pulmonary) Atrium (Left) Ventricle (Left) Aorta (+ branches) BODY
*What are the heart coverings?
Pericardium - double serous membrane that goes over the top of the heart
- visceral pericardium - right by the heart
- parietal pericardium - outside layer of the heart
*What are the components of the heart wall?
Epicardium - outside layer (parietal pericardium)
- connective tissue layer that ensures heart sits in right place
Myocardium - Middle Layer
- mostly cardiac muscle (contracting part)
Endocardium - Inner Layer
- Endothelium in contact with blood when its pumping
*What are the main heart valves?
ATRIOVENTRICULAR VALVES Between atria and ventricles - Bicuspid (mitral) valve = left - Tricuspid valve = right SEMILUNAR VALVES Between ventricle + artery - Aortic S-L valve = left - Pulmonary S-L valve = right
What are heart valves held in place by?
Chordae Tendinae (heart strings)
*How do AV valves open?
- Blood fills atria from body, puts pressure against AV valves + forces them open
- As ventricles fill, AV valves flap limply + hang into ventricles
- Atria contract, forcing last bit of blood into ventricles
*How do AV valves close?
- Ventricles contract, force blood against AV valve cusps
- AV valves close
- Chordae Tendinae tighten, preventing valve flaps from everting back into atria
*How do S-L valves open?
As ventricles contract + intraventricular pressure rises. blood is pushed up against S-L valves, forcing them open.
*How do S-L valves close?
As ventricles relax + intraventricular pressure falls. blood flows back from arteries, filling the cusps of S-L valves + forcing them to close.
What supplies the heart with its own blood supply?
Nourishing circulatory system:
- Coronary arteries
- Cardiac veins
- blood empties into right atrium via the coronary sinus
*What is involved in the conduction system of the heart?
- SAN in right atrium is pacemaker
- AV node (junction of right + left atria + ventricles)
- AV Bundle (Bundle of His)
- Bundle branches (right + left)
- Purkinje Fibres
*How is an electrical impulse sent through the heart?
- EI spreads from SAN throughout Left + Right Atria
- EI spreads from Bundle Branches throughout Left + Right Ventricles
What is systole?
Contraction
Increase in pressure
What is diastole?
Relaxation
Decrease in Pressure
*What are the stages of the cardiac cycle?
- VENTRICULAR FILLING - mid to late diastole
- Ventricular Filling
- Atrial contraction - VENTRICULAR SYSTOLE - atria in diastole
- Isovolumetric contraction phase
- Ventricular Ejection Phase - EARLY DIASTOLE
- Isovolumetric Relaxation
How can we measure cardiac output?
Heart rate x stroke volume
What is cardiac output?
The amount of blood pumped by each side of the heart in one minute
What is stroke volume?
Volume of blood pumped out by each ventricle in one contraction.
How is increased heart rate regulated?
- Sympathetic nervous system = in crisis or low BP
- hormones = adrenaline, thyroxine
- exercise
- decreased blood volume
How is decreased heart rate regulated?
- Parasympathetic nervous system = high BP or high blood vol
- Decreased venous return
What does Digitalis provide in congestive heart failure?
Heart worn out + pumps weakly in CHF
BUT
digitalis provides slow, steady but STRONGER beat
