how does the heart pump blood around the body?
- when heart contracts, muscle cells get shorter, space in cavities decrease, creates high pressure inside, low pressure outside, blood flows outside of heart to body
- endocardium: inside layer of muscle of heart. Made with epithelial tissue
- myocardium: muscle that separates outside from inside heart.
- pericardium: outside layer of heart
lining of heart
a sac-like thing that encloses the whole heart. made with connective tissue.
in between pericardium layers
in between these two layers, there is fluid which reduces friction while heart beats. the sac protects the heart and keeps the fluid contained.
why is left side thicker
left side of heart has a thicker wall since it is responsible for pumping blood all around the body
heart has valves that control blood flow. They are open if there is pressure on one side but closed if there is pressure on the other. tricuspid: 3 flaps, bicuspid:2 flaps. the chordae tendineae and papillary muscles stop the flaps from turning inside out.
pumps to all body (on left side)
: pumps to lungs (on right side of heart)
does heart need blood?
- heart needs blood since blood carries glucose and oxygen (energy) in order to contract
- has own branch of circulation: coronary arteries which supply oxygen rich blood to the heart directly. this is pulmonary circuit
blood flows from…
superior vena cava and inferior vena cava carry o2 poor blood to right atrium
- right atrium to right ventricle
- right ventricle to pulmonary semi-lunar valve to pulmonary trunk to the two pulmonary arteries to lungs
- four pulmonary veins carry o2 rich blood, enter the left atrium
- left atrium sends blood to bicuspid valve to left ventricle
- left ventricle to aortic semilunar valve into aorta to rest of body
first branches off of aorta that provide oxygen to myocardium
pericardium (encloses heart), myocardium (heart muscle), endocardium (interior lining)
Cardiac Muscle (contractile)
shortens when stimulated. membrane is polarized with excess calcium ions. when stimulated, ion channels on the membrane allow positive ions to rush inside, these cause actin and myosin filaments to move past each other, generating a force.
Cardiac Muscle (Self excitable)
cardiac muscle can spontaneously open its ion channels with a neuron signal. neighbour muscles can signal other when their ions leak across connections at intercalated disks. this is depolarization because electrical charges were polarized before event. muscles must use energy to repolarize
Cardiac Muscle (autorhythmic)
if not signaled, cardiac muscles will depolarize with a regular rhythm. pacemaker cells depolarize at a faster rhythm than other cardiac muscle
Cardiac Muscle (nonfatiguing)
can contract indefinitively without tiring. this is a good feature since more energy should go to heart muscle since it supplies oxygen to everything
cardiac muscle features
- contractile, self excitable, autorhythmic, nonfatiguing
Intercalated discs contain two types of specialized junctions: desmosomes (hold the cells tightly together AND enable muscle cells to resist the mechanical stress associated with the stretching and contraction of the cardiac cycle) gap junctions (Rapid communication of action potentials between cardiac muscle cells).
ventricles do what?
produce the main pumping action of the heart
chordae tendinae (heartstrings)
Valves are one way gates that open if there is pressure on one side and close if there is pressure on the other side. They typically consist of two or more flaps of tissue.
The chordae tendineae are tough bands of connective tissue that attach the AV valves (tricuspid and bicuspid) to the opposite wall of the ventricle. They help to pull the AV valves open when the ventricle relaxes, but their main function is to support the AV valves during ventricular systole so they don’t get blown inside out.