Chapter 1 Flashcards: Anatomy and Physiology

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Describe the location of the heart.: The heart is a hollow muscular organ that lies in the middle of the thoracic cavity (mediastinum) behind the sternum, b/w the lungs, and just above the diaphragm. It is surrounded by pericardium (protective sac) and is attached to the thorax through the great vessels (pulm. arteries and veins, aorta, superior and inferior vena cavae.)
Apex of the heart: It is the bottom of the heart and is formed by the tip of the left ventricle.
Base of the heart: It is the top of the heart that is at approximatelhy the level of the second intercostal space.
How big is the heart?: The heart is about a side of a man's fist.
What does the right side of the heart do?: The right side of the heart acts as a low-pressure system that pumps venous blood to lungs.
What does the left side of the heart do?: The left side of the heart is a high-pressure system that pumps arterial blood to the systematic circulation.
What are the septa?: The septa are muscular partitions that separate the heart into two functional pumps: the low-pressure pump (RA and RV) and the hight pressumer pump (LA and LV).
What are atria and what do they do?: The atria are thin-walled, low pressure chambers that receive blood.
Functions of Right Atrium (RA): The right atrium receives deoxygenated blood from the superior vena cava, and the coronary sinus .
Functions of Left Atrium: The left atrium receives oxygenated blood from the lungs via the right and left pulmonary veins.
What do ventricles do?: The ventricles pump blood to the lungs and systemic circulation. They are larger and thicker than the atria.
Endocardium: *Innermost layer of the heart.
*Lines the inside of the myocardium.
*Covers the heart valves
Myocardium: *Middle and thickest layer of the heart.
*Responsible for contraction of the heart.
Epicardium: *External layer of the heart.
*Coronary arteries, blood capillaries, lymph capi
Sarcolemma: Membrane that covers smooth, striated, and cardiac muscle fibers.
Sacromere: The basic protein units responsible for contraction. Myofibrils consist of sacromeres.
Which two types of protein filaments does each sacromere consist of?: Each sacromere consists of two types of protein filaments: actin and myosin.
What do actin myofilaments contain?: They contain tropomyosin and troponin, two proteins that inhibin the formation of cross bridges with myosin.
Sarcoplasmic Reticulum: Network of tubules and sacs that plays and important role in muscle contraction and relaxation by releasing and storing calcium ions.
Syncytium: A unit resembling a network of cells with no separation b/w the individual cells. Cardic muscle fibers are long branching cells that fit together tightly at junctions called intercalated disks. The anatomical arrangement of these tight-fitting junctions gives the appearance of a syncytium. The gap junctions present in myocardial cells allow the cells to conduct electrical impulses very rapidly.
Atrioventicular Valve: Separates the atrium from the ventricle
Tricuspid Valve (Right AV): AV valve that separates the RA and RV
Mitral (Bicuspid) Valve (Left AV): AV valve that separates the LA and LV
Semilunar Valve (SL): Prevent backflow of blood from the aorta and pulmonary arteries into the ventricles during diastole.
Pulmonic Valve: Separates RV and Pulmonary Artery.
Aortic Valve: Separates LV and Aorta
How do heart sounds occur?: Heart sounds occur as a result of vibrations in the tissues of the heart that are created as the blood flow is suddenly increased or slowed with the contraction and relaxation of the heart chambers and with the opening and closing of the heart valves.
1st heart sound "lub": Occurs during ventricular contraction when the tricuspid and mitral (AV) valves are closing.
2nd heart sound "dub": Occurs during ventricular relaxation when the pulmonic and aortic (SL) valves are closing.
Systole: A period during which the chamber is contracting and blood is being ejected. Pressure within the chamber rises.
Diastole: A period of relaxation during which the chamber is filing. Pressure within the chamber falls
How long is the cardiac cycle in a resting adult?: 0.8 seconds
Baroreceptors (pressoreceptors): Specialized nerve tissue sensors located in the internal carotid arteries and aortic arch. They detect changes in blood pressure and cause a reflex response in either the sympathetic or parasympathetic divisions of the autonomic nervous system.
Chemoreceptors: Located in the internal carotid arteries and aortic arch, they detect changes in the concentration of hydrogen ions (pH), oxygen, and CO2 in the blood.
What is heart rate determined by?: The heart is innervated by both the sympathetic and parasympathetic divisions of the autonomic nervous system.
Sympathetic division: "fight or flight" response, allows the body to function under stress
Parasympathetic division: Is responsible for the conservation and restoration of body resources. (feed-and-breed)
Acetylcholine: It is a neurotransmitter that is released when parasympathetic (cholinergic) nerve fibers are stimulated. Acetylcholine binds to parasympathetic receptors.
Parasympathetic receptors: Nicotinic and Muscarinic
Nicotinic parasympathetic receptor: Located in skeletal muscle
Muscarinic parasympathetic receptor: Located in smooth muscle
What is the net effect of parasympathetic stimulation?: Slowing of the heart rate.
Norepinephrine: A neurotransmitter which increases the force of ventricular contraction, heart rate, blood pressure, and cardiac output.
What do sympathetic (accelerator) nerve fibers supply?: They supply the SA node, AV node, atrial muscle, and the ventricular myocardium.
Types of sympathetic (adrenergic) receptor sites: Alpha-receptors
Beta-receptors
dopaminergic receptors

Dopaminergic receptor sites are located in the coronary arteries and renal, mesenteric, and visceral blood vessels. Stimulation of dopaminergic receptor sites results in dilation.

Alpha-receptors more sensitive to norepinephrine

Beta-receptors more sensitive to epinephrine.
Beta-1 / Beta-2: Beta-1 receptors are found in the heart. Their stimulation results in increased heart rate, contractility, and irritability of cardiac cells.

Beta-2 receptor sites are found in the lungs and skeletal muscle blood vessels. Their stimulation results in dilation of the smooth muscle of the bronchi and blood vessel dilation.
Venous Return: Amount of blood flowing into the RA each min from the systemic circulation
Cardiac Output: Amount of blood pumped into the aorta each minute by the heart.

Cardiac Output = stroke vol x heart rate. (CO = SV x HR).

Average adult: 4-8 L/min
Why does an increase in myocardiac contractility occur?: It can occur because of norepinephrine and epinephrine release from the adrenal medulla, thyroxin, insulin and glucagon release from the pancreas, and medications such as calcium and digitalis.
Why does a decrease in myocardiac contractility occur?: Severe hypoxia, decreased pH, hypercapnea (elevated carbon dioxide levels), and medications such as propranolol (Inderal).
What is blood pressure?: Blood pressure is a force exerted by the circulating blood volume on the walls of the arteries.
What is peripheral resistance?: It is the flow of blood determined by blood vessel diameter and the tone of the vascular musculature.
What does blood pressure equal to?: Blood pressure
=
cardiac output x peripheral resistance

Therefore, blood pressure is affected by any condition that increases peripheral resistance or cardiac output.
Preload: Preload is the force exerted by the blood of the walls of the ventricles at the end of diastole
Afterload: Afterload is pressure or resistence against which the ventricles must pump to eject blood.
The Frank-Starling Law: To a point, the greater the volume of blood in the heart during diastole, the more forceful the cardiac contraction, and the more blood the ventricle will pump (stroke volume.)
Describe the blood flow throught the Right Atrium and Right Ventricle.: *The RA receives deoxygenated blood from the superior and inferior vena cavae and the coronary synus.
*Blood flows from the RA through the tricuspid valve into the RV.
*RV contracts, tricuspid valve closes.
*RV expels the blood through the pulmonic valve into the pulmonary trunk.
*Pulmonary trunk divides into L and R pulmonary arteriey, each carries blood to one lung.
Describe the blood flow through the Left Atrium and Left Ventricle: *LA receives oxygenated blood from lungs.
*Blood flows from the LA through the mitral(bicuspid) valve into the LV.
*LV contracts, mitral valve closes.
*Blood leaves the LV through the aortic valve to the aorta and its branches and is distributed throughout the body (systemic circuit)
Superior Vena Cavae: Deoxygenated blood from the head and neck is emptied there.
Inferior Vena Cavae: Blood from the lower body is emptied there.

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