The Heart Flashcards
Heart
pump, which is made of two pumps into one, pushes blood through two distinct circuits
Pulmonary circuit
blood is pushed from the heart to the lungs, and then back to the heart
Systemic circuit
blood is pushed from the heart out to the various body systems and tissues, and then back to the heart
How much blood does the human heart pump?
7200 liters of blood a day/1800 gallons
Heart location
thoracic cavity, in the pericardial cavity, covered by a membrane known as the pericardium
Base (top)
the part in which the great vessels arise
Apex (bottom)
the pointed tip to the inferior end of the heart
Cardiac muscle fibers
branching, intercalated discs, striations, one nucleus per cell; auto-rhythmic - capable of contracting on their own
Structures of the heart
four chambers, great vessels, four valves
Heart chambers
right atrium, left atrium, right ventricle, left ventricle
Ventricles
located towards the apex (bottom) part of the heart, thick walled, left ventricle has the thickest chamber wall
Great Vessels
aorta, pulmonary trunk, superior vena cava, inferior vena cava, pulmonary vein
Artery
A vessel that carries blood away from the heart
Vein
A vessel that carries blood towards the heart
Aorta
carries blood away from the left ventricle, goes to various body and organ tissues
Pulmonary trunk
carries blood away from the right ventricle, going to the lungs
Superior vena cava
carries blood toward the right atrium, coming back from the upper body
Inferior vena cava
carries blood toward the right atrium, coming back from the lower body
Pulmonary veins
carry blood toward the left atrium, coming from the lungs, come from both right and left sides
The four valves
designed to prevent backflow of blood
Tricuspid valve (right atrioventricular valve)
located between the right atrium and the right ventricle, prevents backflow into the right atrium, three large cusps
Bicupsid valve (left atrioventricular valve)
located between the left atrium and left ventricle, prevents backflow into the left atrium, two large cusps
Pulmonary semilunar valve
located at the base of the pulmonary trunk, it prevents backflow into the right ventricle
Aortic semilunar valve
located at the base of the aorta, prevents backflow into the left ventricle
Route of blood flow through the heart
deoxygenated blood from the tissues begins to return toward the heart in larger veins, reaches the superior vena cava or inferior vena cava, enters the right atrium, through the tricuspid valve, enters the right ventricle, through the pulmonary semilunar valve, through the pulmonary trunk, through pulmonary arteries to the right and left lung, is oxygenated, through the pulmonary veins to the left atrium, through the bicuspid valve and enters the left ventricle, through the aortic semilunar valve into the aortic arch, to aorta, to smaller arteries, and back to the tissues
The heart cycle
each beat felt is one heart cycle; both atria must contract at the same time followed by the ventricles both contracting; one heart cycle = atria contract, ventricles contract, rest
Conduction system of the heart
cardiac muscle cells that coordinate the entire heart cycle
Sinoatrial node
the heart’s pacemaker
Cardiac output
volume of blood pumped per minute; stroke volume x heart rate
Stroke volume
the volume of blood pumped per beat
Heart rate
the number of beats per minute
Intrinsic regulation
a mechanism that is contained within the heart itself
Extrinsic regulation
this regulatory mechanism is dependent on input from outside the heart, input from the nervous and endocrine systems
Nervous system
two sets of nerve fibers that innervate the SA node
Sympathetic
these nerve endings release a neurotransmitter that stimulates the SA node to reach threshold more easily, resulting in more frequent firing, which increases the heart rate
Parasympathetic
these nerve endings release a neurotransmitter that stimulates the SA node to reach threshold less easily, resulting in less frequent firing, which decreases the heart rate
Endocrine System
many hormones affect the heart rate. epinephrine has a powerful stimulatory action on the SA node, causing the heart rate to increase dramatically.
Tunica intima
the most important feature of this layer is the innermost lining of the blood vessel; has an endothelium along the inner wall; endothelium is simple squamous epithelium
Arteries
carry blood away from the heart; have thicker walls than veins; have more smooth muscle in their walls; stronger and more elastic; operate under higher pressure; small lumen and diameter than veins
Elastic arteries
the largest of the arteries; have very elastic walls and are especially good at expanding and recoiling when surges of blood hit them; example is aorta
Muscular arteries
medium-sized arteries; very thick tunica media; especially good at regulating blood flow, which changes the size of the lumen that blood flows through; example is radial artery
Veins
carry blood toward the heart; simple valves scattered throughout their length
Muscular action
when skeletal muscles contract, they squeeze against the veins, forcing blood to move; valves prevent backflow and the blood will move in the correct direction
Capillaries
very thin-walled; two different categories: continuous and fenestrated
Continuous capillaries
cells that form the walls are very tightly joined together; substances must diffuse or be transported through the cell membrane; they are less permeable than fenestrated capillaries; they are the most common type found in the body
Fenestrated capillaries
the cells have pores between them; substances can move more freely throughout the pores, larger substances will be able to move through the capillary wall; they are more permeable than continuous capillaries; they are less common, usually found in specialized situations
Aging of the arteries
deposits being to form on the walls of the arteries; walls become less elastic, thicker, and tougher; the flow of blood becomes more restricted; blood pressure must be higher to over the increased resistance, creating hypertension; the work load of the heart is greater, which is detrimental
Arteriosclerosis
hardening of the arteries
Atherosclerosis
the accumulation of plaque deposits
Vessel wall friction
the number one source of resistance
Blood viscosity
how thick the blood is
Local control
this mechanism will regulate how much blood flows to one small, local, specific capillary bed; automatic mechanism, no outside neural or hormonal control
Regional control
involves adjusting the amount of blood flow to a particular organ of the body or an organ system; regulated by both the nervous and endocrine system
Neural control
autonomic; two branches that stimulate the smooth muscle cells in the vessel wall
Sympathetic stimulation
increases blood blow to the systems that are important for activity; examples include nervous, respiratory, and muscular systems
Parasympathetic stimulation
increases blood flow to the systems that use periods of physical inactivity to operate at full capacity; examples include the digestive and urinary system
Endocrine control
a particular hormone may stimulate some blood vessels to dilate and others to constrict; example is epinephrine
Sympathetic innervation
stimulates the SA node to beat faster
Parasympathetic stimulation
stimulates the SA node to beat slower
Epinephrine
stimulates the SA node to beat faster
Stroke
sudden decrease in blood supply to an area of the brain
Embolism stoke
floating blood clot; travels in arteries and gets stuck as the vessels narrow which can completely cut off blood flow to an area of the brain
Hemorrhagic stroke
occurs when a blood vessel ruptures; can happen from trauma or a weakening of the vessel wall (aneurysm)
