The Circulatory System Flashcards
where does the right atrium receive blood from?
superior vena cava, inferior vena cava, coronary sinus
where does the right ventricle receive blood from, and send blood to?
receives blood from the right atrium, sends blood to the lungs
where does the left atrium receive blood from?
pulmonary veins
where does the left ventricle receive blood from, and send blood to?
receives blood from left atrium. sends blood all over the body
what is the pericardium?
the thin sac surrounding the heart
- keeps heart contained in chest cavity, prevents heart from over-expanding, limits heart motion
what are the layers of the heart wall?
epicardium: outer protective layer
myocardium: muscular middle layer
endocardium: inner layer
what structures enable the myocardium to behave as a single coordinated unit?
intercalated discs (zone between adjacent cardiomyocytes) contain two types of cell junctions:
- desmosomes: anchoring junctions, keep heart from pulling itself apart
- gap junctions: allow the electrical impulse to move from cell to cell so heart beats synchronously
why do cardiac cells have many mitochondria?
because the heart is extremely active and requires a lot of energy to constantly pump blood through circulatory system
why is the myocardium of the left ventricle thicker than that of the right ventricle?
right pumps blood to adjacent lungs.
left pumps to the rest of the body.
in a resting state… is the intracellular fluid of heart cells more negatively charged than extracellular fluid?
yes. the cells are ‘polarised’ - when electrically stimulated by another cell, the permeability of the cell membrane to positive charged ions increases
what is an ECG?
electrocardiogram - sum total of electrical changes of individual cells
define depolarisation
electrical activation of the myocardium
define repolarisation
restoration of electrical potential of the heart
define systole
contraction of the heart
define diastole
relaxation of the heart
steps of action potential movement through the heart
- depolarisation of atrial contractile fibres (P wave)
- atrial systole
- depolarisation of ventricular contractile fibres (QRS complex)
- ventricular systole
- repolarisation of ventricular contractile fibres (T waves)
- ventricular diastole
what is the SA node?
sinoatrial node - pacemaker of the heart
- fires at regular intervals to cause the heart beat at 60-70bpm for a healthy resting heart
outline the sequence of excitation during cardiac conduction
- SA node
- through atria
- atrio-ventricular node
- atrio-ventricular bundle
- R& L branches
- purkinje fibres (ventricular contraction)
what are some influences on the conduction system?
neurotransmitters and hormones from sympathetic nervous system can modify the heart rate and force of contraction, do not set fundamental rhythm
- parasympathetic nervous system releases acetylcholine
- heart is under parasympathetic dominance at rest
what does blood flow through coronary arteries do?
delivers oxygenated blood and nutrients the myocardium
what does blood flow through coronary veins do?
removes carbon dioxide and wastes from the myocardium
define cardiac output.
the volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk each minute
define stroke volume.
the amount of blood pumped out of the ventricle in one beat
what is the cardiac output formula?
CO(mL/min) = SV (mL/beat) x HR (beats/min)
what are factors affecting stroke volume?
- preload: amount of ventricular stretch at the end of diastole
- contractility
- afterload: amount of resistance the heart must overcome to open the aortic valve and push the blood volume out into the systemic circulation
what is the function of heart valves?
controls flow of blood through the heart, preventing back flow
identify each heart valve.
- tricuspid valve
- pulmonic or pulmonary valve
- mitral (bicuspid) valve
- aortic valve
identify each layer of blood vessels.
- tunica interna - innermost layer
- tunica media - middle layer, smooth muscle and elastic fibres
- tunica externa - outermost layer, adjacent to surrounding tissue
describe the difference between arteries and veins.
arteries are built to endure exposure to much greater pressure than veins
- arterioles can constrict and dilate due to smooth muscle. elastic tissue enables arteries to withstand greater pressure
veins are capacitance vessels and have little elastic.
- veins operate at low pressure, low speed and possess values to prevent back flow
why is the radius/diameter of blood vessels important?
radius/diameter of blood vessels are one of the most important ways we can regulate BP, and adapt to environmental changes.
what is an anastomosis?
union of the branches of 2 or more arteries supplying blood to the same region of the body - alternate route for blood flow
what are capillaries?
microscopic vessels that connect arterioles and venules
what are venules?
small vessels that are formed by union of several capillaries
what are veins?
formed from union of several venules
what is blood pressure, and what is it determined by?
the pressure exerted by the blood against the walls of arteries
- determined by cardiac output and vascular resistance
what is resistance, and what does it depend on?
the opposition to blood flow due to friction between blood and the walls of blood vessels - higher resistance = smaller blood flow
- depends on:
1. diameter of blood vessel lumen
2. blood viscosity
3. total blood vessel length
4. arterial stiffness
how is blood pressure regulated?
- medulla oblongata contains cardiovascular centre, which is a group of neurons that regulate heart rate, contractility and blood vessel diameter
- hypothalamus also contains cardiovascular centre (sympathetic only)
baroreceptors: pressure-sensitive sensory neurons that monitor stretching of the walls of the blood vessels and atria
what is auto regulation of blood pressure?
ability of tissue to automatically adjust own blood flow to match metabolic demand for delivery of oxygen and nutrients and removal of wastes
what is the mean arterial pressure? (MAP)
MAP = CO x total peripheral resistance
what are the major components of blood?
plasma (55%)
cells (45%)
state the major functions of blood?
- transportation (dissolved gases, wastes, hormones, enzymes, nutrients etc.)
- maintain body temp
- controls pH
- removes toxins from body
state the types of white blood cells.
- basophils: release histamine, cause hypersensitivity reactions/asthma attacks
- neutrophils: role in acute inflammatory response
- eosinophils: digest bacteria and pathogens
- monocytes: phagocytic cells
- lymphocytes: chronic inflammation and long term immunity
