The heart Flashcards
cardiac muscle cells
heart is composed of these muscles
cardiac cell functions
- contract without stimulation by nervous system (contraction is myogenic)
- branched, allowing for faster signal propagation and contraction in 3 dimensions
- not fused together, but are connected by gap junctions at intercalated discs
- have more mitochondria, as they are more reliant on aerobic respiration than skeletal muscle
cardiac cell structural features
- longer period of contraction and refraction, which is needed to maintain a viable heartbeat
- does not become fatigued
- interconnected network of cells is separated between atria and ventricles, allowing them to contact separately
atrial contraction
within right wall of right atrium is specialized cluster of cardiomycocytes called sinoatrial node
- acts as primary pacemaker, controlling rate at which heart beats
- sends electrical signals
atrioventricular node
- signals from SA node must be relayed through second note located within cardiac skeleton
- AV node separates atrial and ventricular contractions
- AV node propagates electrical signals more slowly than SA node, creating a delay in passing on the signal
ventricular contraction
occurs following excitation of atrioventricular node
- AV node sends signals down septum via Bundle of His
- Bundle of His innervates fibres in ventricular wall, which causes the cardiac muscle to contract
heart relaxation / diastole
after every contraction of the heart, there is a period of insensitivity to stimulation
- recovery period is long and allows heart to passively refill with blood between beats
- long recovery period also helps prevent heart tissue becoming fatigued
electrical activity
P wave: depolarization of atria in response to signalling from SA node (atrial contraction)
QRS complex: depolarization of ventricles (ventricular contraction), triggered by signals from AV node
T wave: repolarization of ventricles (ventricular relaxation) and completion of standard heart beat
cardiac output
the amount of blood the heart pumps through the circulatory system in 1 minute
effects of heart rate
- exercise
- age
- disease
- temperature
- emotional state
control of heart rate
- sympathetic nervous system and decreased by parasympathetic stimulation
- increased hormonally via adrenaline
stroke volume
amount of blood pumped to body (from left ventricle) with each beat of the heart
changes in stroke volume
affect blood pressure - more blood or more pressure will increase overall pressure
- systolic bp is higher, as it represents the pressure of blood following contraction of heart
- diastolic bp is lower, as it represents the pressure of blood while heart is relaxing between beats
hypertension
- abnormally high blood pressure (either systolic, diastolic, or both)
thrombosis
formation of a clot within a blood vessel that forms part of the circulatory system
- occurs in arteries when the vessels are damaged as a result of the deposition of cholesterol (atherosclerosis)
- Atheromas (fat deposits) develop in the arteries and significantly reduce the diameter of the vessel (leading to hypertension)
- high blood pressure damages the arterial wall, forming lesions known as atherosclerotic plaques
- If a plaque ruptures, blood clotting is triggered, forming a thrombus that restricts blood flow
