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The Cardiovascular System. Functions of Cardiovascular System. Pump blood through the body Brings oxygen and nutrients to all body cells Removes waste. Hollow cone-shaped muscular pump Located in the thoracic cavity, just above the diaphragm The pericardium encloses the heart

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The Cardiovascular System

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The cardiovascular system l.jpg

The Cardiovascular System


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Functions of Cardiovascular System

  • Pump blood through the body

  • Brings oxygen and nutrients to all body cells

  • Removes waste


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Hollow cone-shaped muscular pump

Located in the thoracic cavity, just above the diaphragm

The pericardium encloses the heart

Pericardial cavity – space between the parietal and visceral layers of the pericardium

Structure of the Heart


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3 layers

Epicardium – outer layer, protects the heart by reducing friction (serous membranes)

Myocardium – thick middle layer mostly composed of muscle

Endocardium – inner layer consists of connective tissue and epithelium

Wall of the heart


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4 hollow chambers

2 atria (left and right)

2 ventricles (left and right)

Septum separates the atrium and ventricles on the right and left sides

Keeps blood from right side of heart from mixing with blood from the left side of the heart

Valves

Atrioventricular valve (AV Valve) – ensures one way flow of blood between the atria and ventricles

Tricuspid valve

Bicuspid valve (mitral valve)

Pulmonary valve

Aortic valve

Heart Chambers and valves


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Path of Blood Through the Heart

  • Low Oxygen/High Carbon Dioxide

    • Enters right atrium through vena cavae

      • Contraction of atrium

    • Tricuspid valve

    • Right ventricle

      • Contraction of Ventricle (tricuspid valve closes)

    • Pulmonary valve to pulmonary arteries to capillaries in lungs (alveoli)

  • High Oxygen/Low Carbon Dioxide

    • Oxygenated blood returns to heart through the pulmonary veins

    • Enters left atrium

      • Contraction of atrium

    • Bicuspid valve

    • Left ventricle

      • Contraction of Ventricle (bicuspid valve closes)

    • Aortic valve to aorta and its branches


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The heart must have its own blood supply in order for it to function (myocardium must have oxygen for muscles to contract)

Coronary arteries (brings blood to heart tissue)

Cardiac veins (carries blood away from heart tissue)

Blood Supply to the Heart


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The heart chambers function in a coordinated fashion

Systole – contraction

Diastole – relaxation

When the atria contract, the ventricles relax. When the ventricles contract, the atria relax

Cardiac Cycle – series of events constitutes a complete heartbeat

Heart Actions


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Cardiac Cycle


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Cardiac Cycle

  • During the cardiac cycle, pressure within the heart chambers rises and falls.


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Heart Sounds

  • The heart beat through a stethoscope sounds like lubb –dupp

  • Sounds are due to vibrations in the heart tissues associated with closing of the valves

  • Lubb – ventricular contraction when the A-V valves are closing

  • Dupp – ventricular relaxation when the pulmonary and aortic valves are closing


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Clumps of specialized cardiac muscle tissue distribute impulses throughout the myocardium instead of contracting

Sinoatrial node (SA node) – can initiate impulses without stimulation from nerve fibers

Pacemaker of the heart

Atrioventricular node (AV node)

Cardiac Conduction System


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Regulation of Cardiac Cycle

  • The volume of blood pumped changes to accommodate cellular requirements. (ie. strenuous exercise)

  • Since the S-A node normally controls heart rate, changes in this rate are often a response to motor impulses carried by the parasympathetic and sympathetic nerve fibers

  • The cardiac control center of the medulla oblongata maintains balance between the inhibitory effects of parasympathetic fibers and the excitatory effects of sympathetic fibers

  • Impulses from the cerebrum and hypothalamus also influence the cardiac control center


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Blood Vessels

  • Blood Vessels form a closed circuit of tubes that carries blood from the heart to cells and back again

    • Arteries – strong, carry blood away from the heart under high pressure

    • Arterioles – thinner, finer branches

    • Capillaries – smallest diameter blood vessels, connect smallest arterioles and smallest venules.

    • Venules – microscopic vessels that continue from the capillaries

    • Veins – carry blood back to the atria


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Blood Vessels

  • Remember, the walls of arteries and veins contain smooth muscle that can contract, reducing the diameter of the vessel (vasoconstriction)

  • Vasodilation – relaxation of the muscle fibers, causing the diameter of the vessel to increase


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Exchanges in Capillaries

  • Gases, nutrients, and metabolic by-products are exchanged between the blood in capillaries an the tissue fluid surrounding body cells.

  • The substances exchanged move through capillary walls by diffusion and osmosis (based on difference in concentration gradients) and filtration (force molecules through a membrane with hydrostatic pressure)


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Veins

  • Return blood to the heart

  • Many veins, particularly those in the upper and lower limbs, contain flap-like valves which close if blood begins to back up into a vein.

    • They aid in returning blood to the heart by preventing blood from flowing in the opposite direction


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Blood Pressure

  • Most commonly refers to pressure in arteries supplied by branches of the aorta.

  • Systolic pressure – the maximum pressure during ventricular contraction

  • Diastolic pressure – the lowest pressure that remains in the arteries during ventricular relaxation


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Factors Influencing Arterial Blood Pressure

  • Heart action

    • Stroke volume – the volume of blood discharged from the left ventricle with each contraction

    • Cardiac output – the volume of blood discharged from the left ventricle per minute

  • Blood Volume – the sum of all the formed elements and plasma in the vascular system

  • Peripheral Resistance – friction between the blood and the walls of the blood vessels (contraction and dilation of vessels)

  • Blood Viscosity – the ease with which a fluid’s molecules flow past one another

    • “blood is thicker than water


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Control of Blood Pressure

  • Read: Control of Blood Pressure (pg 348-350) and summarize in your notes

  • Complete CYR questions on pg 350


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ORQ

  • Cigarette smoke contains thousands of chemicals, including nicotine and carbon monoxide. Nicotine constricts blood vessels. Carbon monoxide prevents oxygen from binding to hemoglobin. How do these two components of smoke affect the cardiovasuclar system?


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