Heart Minus The Vessels Flashcards
The sinoatrial node
Does it affect ventricles?
Spontaneously active and it’s excitation (forms an electrical signal and is start of heart beat) spreads through walls of atria causes contraction and blood flow into atria.
Excitation prevented from spreading into ventricles, making them contract from the top down by insulating fibres
The cardiac cycle
Refers to a sequence of events taking place during heart’s beating.
Excitation does spread to ventricles though, how?
Only via atrioventricular node, slowing because of higher electrical resistance. Allowing time blood to flow totally into ventricle before contraction.
Where does excitation spread after avnode in ventricles?
Spreads through bundle of His which have a low electrical resistance and found in septum wall.
After passing bundle of his in where, where does it now go? (the excitation)
In the septum wall. It then branches into purkinje fibres which carry excitation upwards through ventricular muscles
The delayed contraction of ventricle walls…
Contract from bottom up forcing blood up and out through pulmonary artery and aorta.
How can the role of the San impulses be controlled?
Other factors…?
They can be altered by nerves from brain,
- accelerator nerve impulse speeds the heart beat.
- vagus nerve impulse slows heart beat.
Other factors include adrenaline and emotions.
Heart cycle. What to keep in mind.
Muscle > volume of chamber > pressure of chamber > blood flow through valves.
Atrial systole length and facts.
Lasts 0.1 seconds.
Atrial cardiac muscle contract, reducing volume of atria, increasing pressure, and blood is forced through AV valve into ventricle down pressure gradient.
Ventricular systole.
Lasts 0.3 seconds. 0.3 seconds. 0.3 seconds.
The ventricular cardiac muscle contracts, decreasing volume, increasing pressure, and blood oils forced through semilunar valve down pressure gradient into aorta. AV VALVE CLOSES PREVENTING BACK FLOW OF BLOOD.
Ventricular diastole.
Lasts 0.4 secs. Lasts 0.4 secs. Lasts 0.4 secs. Lasts 0.4 sec.
Ventricular cardiac muscle relaxed, volume increases, pressure decreases.
SEMILUNAR VALVE CLOSES TO PREVENT BACKFLOW OF BLOOD.
Closed circulation.
Open circulation.
Closed circulation is the movement of blood with vessels.
Open circulation is movement of blood without vessels.
What causes ventricles to reach a minimum or maximum?
As ventricles contract (systolic) the pressure reaches a max, as the relax (diastolic) it reaches a minimum.
Blood pressure can be recorded with a what?
Sphygmomanometer
The systolic blood pressure ad diastolic blood pressures refer to what on a sphygmomanometer?
The systolic blood pressure is the maximum pressure produce in left ventricle during systole.
The diastolic blood pressure is the minim pressure in aorta.
Recordings of a sphygmomanometer have systolic over diastolic. What is a normal adult’s range? Systolic values and diastolic values over what give what or what?
Normal adult: 110-140/60-90
Systolic over 150mmhg and diastolic over 90mmhg are high blood pressures or hypertension.
How is hypertension dangerous?
As over a long term it can damage the delicate endothelial lining leading to increase risk of thrombosis which can lead to MYOCARDINAL INFARCTION, and strokes.
But how does hypertension really do it’s job? Or how does it occur?
Hypertension occurs due to atherosclerosis
Atherosclerosis.
Ldls deposit under endothelial lining of arteries> artery wall stretches and scar tissue develops> the lipid buildup and scar tissue is called atheroma> this can break the endothelium forming an artery blocking blood clot> if a thrombus forms in a coronary artery, the muscle below clot will starve of oxygen and die> this is coronary heart disease/ischemic heart disease> leading to MYOCARDINAL IBFARCTION.
Other factors inducing atherosclerosis?
Tobacco smoke, smoking, stress, high salt intake, high alcohol intake
ECG stands for what and does what!
Electrocardiogram measures electrical activity inside heart.
What does an ECG consist of? What do the letters stand for?
ECG consists of a number of waves that correspond to definite electrical events during cardiac cycle.
P equals atrial contraction
Q,R and S precede ventricular contraction.
T equals relaxation of ventricles.
Deviation of heart rhythm is called arrhythmia, a patient can have one of three. What does v f stand for?
Ventricular fibrillation is where the contraction of heart is irregular- no clear pqrs spike.
Chb means what?
Complete heart block. Altria an ventricles are bearing independantly. P wave is occurring after or before qrs.
