Heart physiology Flashcards
Function of CVS
Transport mechanims of:
O2, CO2, nutrients, antibodies, hormones, waste products and thermoregulation
Describe the heart and how blood flows through it.
The heart is a muscular sack found at the center of the CVS. Blood is received by the superior vena cava (deoxygenated) into the right atrium. The right atrium feeds into the right ventricle which contracts following depolarisation. The deoxygenated blood moves to the lungs for gas exchange and returns to the heart to pump oxygenated blood to oxygen deficient organs.
Oxygenated blood enters via pulmonary vein into the left atrium. The oxygenated blood enters the left atrium which pumps oxygenated blood via the aorta to the rest of the body for gas exchange at organs in action.
Name all the valves and the function.
Mitral, aortic, pulmonary and tricuspid. All function to prevent backflow
What is the heart enclosed by and how do they facilitate heart function?
Heart is enclosed by pericardium and myocardium.
Pericardium -a fibrous sac that encloses the heart and great vessels. Keeps the heart in stable location in the mediastinum and facilitates its movements
Myocardium - muscle of the heart. Make up the middle and the thickest layer of the heart wall. Lies between single cell endocardium layer and the outer epicardium
What is found inbetween pericardium and musclular wall of the heart?
The pericardial cavity filled with fluid to aid the contraction by preventing friction
How does the heart meet its own oxygen demnds?
Occurs via the coronary artery found running on the outside of the heart. Often the site for disease.
Coronary arteries branch directly from the aorta
What are the 3 main blood vessesl?
Vein, Aorta and capillary
Describe the artery compositions
Thick smooth muscle layer and elastic layer, since the arteries are under high pressure – these two components allow the arteries to expand and contract
Elastic layer function to recoil to normal configuration following contraction
Describe the veins compositions
Unlike arteries the veins do no recieve blood under high pressure, thus, have a smaller elastic layer.
Carries blood against the gravitational pull - tendency for backflow - counteracted by valves found in veins
Movement of blood is assisted by skeletal muscles.
Describe the capillary beds compostions
As blood passes through the artery it branches off into smaller and smaller blood branches called arterioles and then into capillaries
- Capillaries carries blood through an organ or tissue
They then combine back together to venules and then to veins
At the arteriole the fluid is squeezed out of the capillary due to higher blood pressure, whilst fluid enters capillary in venule due to osmotic attraction
What cells exist in the heart to aid contraction?
Conducting cells - specialised cells co-ordinate heart beat (cardiac conduction system aka action potential)
Contractile cells - generate pressure to move blood using myocardium
Describe how the electrical impulses induce the contractility of the heart.
The action potential begins in the sinoatrial node (SA) found in the right atrium. Here the action potential passes through to the left atrium causing them to contract simoultaneously. The action potential is then passed down through the atrium to the atrioventricular node. The action potential reaches apex of the heart via the bundle of his fibres. At the apex the action potential passes up via the purkinjo fibres causing contraction of the ventricles bottom up. Thus, forcing blood to move out the heart
What is the most accurate tool to investigate the hearts function?
ECG (electrocardiogram)
Basics of an ECG
Produces 12 views of the heart using electrodes placed 1x right arm, 1x left arm, 1x left leg, 1x right leg, and 6x chest.
Uses the action potential between the different electrodes, known as leads, to produce an accurate oversight of the heart. LEAD two is the most useful
ECG what do the different intervals represent. (look at a pic)
First peak (PQ interaval/P wave) is atrial depolarisation
Second (and largest) peak (QRS complex) is ventricular depolarisation
Final peak (T wave) - is ventricular repolarisation
Remember the atrial repolarisation is hidden in the QRS