Circulatory System

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Circulatory System
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Do Now

• Why is it important for your heart to continue
  beating even when youre sleeping?
• What does your body need?
• What are some wastes?

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Circulation and Respiration

• Each breath brings oxygen rich air into your body
• Your cells need that oxygen
• Your heart delivers oxygen to your cells
• Working together, your circulatory and
  respiratory systems supply cells throughout the
  body with the nutrients and oxygen that they need
  to stay alive!

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Multicellular Needs

• Unicellular organisms dont need a circulatory
  system, because the cell is in direct contact
  with the environment and oxygen, nutrients and
  wastes can easily diffuse across the cell
  membrane by diffusion.
• Multicellular organisms need a circulatory system
  to transport substances made in one part of the
  body to sites where they are needed in another
  part of the body.

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Function

• The circulatory system transports substances
  including oxygen, nutrients and wastes to and
  from cells responding to changing demands by
  diffusion (from high to low concentration along
  concentration gradient).

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Structure

• Humans have a closed circulatory system.
• Blood is pumped through a system of vessels
• (In an open system, blood flows in vessels and
  sinuses/gills)
• Sometimes the circulatory system is also called
  the cardiovascular system because
• Cardio heart
• Vascular vessels
• The human circulatory system consists of
• The heart
• A series of blood vessels
• Blood that flows through them

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The Heart

• Located near the center of your chest
• A hollow organ about the size of your fist
  composed of cardiac muscle.
• Enclosed in a protective sac of tissue called the
  pericardium
• Inside there are two thin layers of epithelial
  and connective tissue
• Contractions of the myocardium, a thick cardiac
  muscle, pump blood through the circulatory system
• The heart contracts about 72 times a minute
• Each contraction pumps about 70 mL of blood

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Heart

• Septum, or wall, separates the right side form
  the left side preventing mixing of oxygen-rich
  blood and oxygen-poor blood
• Flaps of connective tissue called valves divide
  each side into 2 chambers totaling 4 chambers
• Upper chambers receive blood atrium
• Lower chambers pump blood out of heart ventricle

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Types of Circulation

• Pulmonary circulation from right side of the
  heart to lungs where carbon dioxide leaves the
  blood and oxygen is absorbed
• Systemic circulation from left side of the
  heart to organs
• Coronary circulation through heart tissue

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Pulmonary Circulation

• The right side of the heart pumps blood from the
  heart to the lungs
• In the lungs, carbon dioxide leaves the blood
  while oxygen is absorbed.
• The oxygen-rich blood goes into the left side of
  the heart

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Systemic Circulation

• The oxygen-rich blood from the left side of the
  heart is pumped to the rest of the body
• Oxygen-poor blood returns to the right side of
  the heart
• This blood is oxygen-poor because the cells
  absorbed the oxygen and released carbon dioxide
  into the blood
• The oxygen-poor blood is ready for another trip
  to the lungs to get oxygen again

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Figure 37-2 The Circulatory System
Section 37-1
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Coronary Circulation

• Remember the heart is an organ and needs
  nutrients, oxygen and creates wastes.
• Blood flows to the tissues of the heart too!

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Blood Flow through the heart

• Blood leaves the heart in arteries, and blood
  returns to heart in veins.
• Oxygenated blood returns from the lungs through
  the pulmonary veins to the left atrium.
• Oxygenated blood is pumped from the left atrium
  through the mitral valve to the left ventricle.
• Oxygenated blood leaves the left ventricle
  through the aortic valve to the aorta, which is
  the largest artery of your body.
• The aorta branches into various arteries pumping
  blood through your body.
• Deoxygenated blood returns from the top of your
  body through the superior vena cava and from the
  bottom of your body through the inferior vena
  cava to the right atrium.
• Deoxygenated blood is pumped from the right
  atrium through the tricuspid valve to the right
  ventricle.
• Deoxygenated blood leaves the right ventricle
  through the pulmonary valve to the pulmonary
  arteries.
• The pulmonary arteries pump blood to the lungs to
  absorb oxygen and release carbon dioxide.

Heart circulation animation http//www.nhlbi.nih.
gov/health/dci/Diseases/hhw/hhw_pumping.html
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The Path of Blood
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Valves

• Blood enters into the atria of the heart,
  separated from the ventricles by valves,
  preventing back-flow of blood keeping the blood
  flowing in one direction
• When the atria contract, the valves open and
  blood flows into the ventricles
• When the ventricles contract, the valves close
  preventing blood from flowing back into the atria
  and blood flows out of the heart
• At the exits of the ventricles, there are valves
  that prevent blood from flowing back into the
  heart
• The lub-dup sound of your heart is caused by
  the closing of the hearts valves. The lub is
  when the ventricles contract and blood being
  forced against the artioventricular or A-V
  (tricuspid or mitral) valves. The dup is the
  blood being forced against the semilunar (aortic
  or pulmonary) valves.

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Figure 37-3 The Structures of the Heart
Section 37-1
Left Atrium
Right Atrium
Left Ventricle
Septum
Right Ventricle
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Heartbeat

• There are two muscle contractions in the heart
• The atria
• The ventricles
• Each contraction begins in a small group of
  cardiac muscle cells in the right atrium that
  stimulate the rest of the muscle cells
  sinoatrial node (SA node)
• Since the sinoatrial node sets the pace for the
  heart it is also called the pacemaker
• The impulse spreads from the pacemaker through
  fibers in the atria to the atrioventricular node
  (AV node) and through fibers in the ventricles
• When the atria contract, blood flows into the
  ventricles
• When the ventricle contract, blood flows out of
  the heart

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The Sinoatrial Node
Section 37-1
Contraction of Atria
Contraction of Ventricles
Sinoatrial (SA) node
Conducting fibers
Atrioventricular (AV) node
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Changing Heartbeat

• Your heart can beat faster or slower, depending
  on your bodys need for oxygen-rich blood
• When you exercise, your heart rate can increase
  to 200 beats per minute
• The autonomic nervous system influences heart
  rate
• Neurotransmitters released by neurons in the
  sympathetic nervous system can increase heart
  rate, and those released by the parasympathetic
  nervous system can decrease heart rate

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Blood vessels

• Blood circulates in one direction and it is moved
  by the pumping of the heart
• As blood flows through the circulatory system, it
  moves through three types of blood vessels
• Arteries
• Capillaries
• Veins

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Arteries

• Large vessels that carry blood away from the
  heart to tissues of the body
• Except for the pulmonary arteries, all arteries
  carry oxygen-rich blood.
• Arteries have thick walls of elastic connective
  tissue, contractible smooth muscle, and
  epithelial cells that help them withstand the
  powerful pressure produced when the heart
  contracts and pushes blood into the arteries.

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Capillaries

• The smallest of the blood vessels connecting
  arteries and veins
• Walls are one cell thick allowing for easier
  diffusion of nutrients and oxygen from
  capillaries to body cells and wastes and carbon
  dioxide from body cells to capillaries

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Veins

• Return blood to the heart
• Veins have walls of connective tissue and smooth
  muscle
• Large veins contain valves that keep blood
  flowing towards the heart
• Many veins are located near skeletal muscles, so
  when the muscles contract, they help force blood
  through the veins, even against gravity
• Exercise helps prevent accumulation of blood in
  limbs and stretching veins out of shape

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Figure 37-5 The Three Types of Blood Vessels
Section 37-1
Vein
Artery
Capillary
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Blood Pressure

• The heart produces pressure when it contracts.
• The force of blood on the arteries walls blood
  pressure
• Blood pressure decreases when the heart relaxes,
  but there must always be some pressure to keep
  the blood flowing
• Doctors measure blood pressure with a
  sphygmomanometer recording two numbers
• Systolic pressure force felt in arteries when
  ventricles contract
• Diastolic pressure force of blood felt in
  arteries when ventricles relax
• Average adults blood pressure 120/80

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Regulating Blood Pressure

• With the nervous system
• Sensory neurons at several places in the body
  detect blood pressure and send impulses to brain
  stem (medulla oblongata)
• When too high, the autonomic nervous system
  releases neurotransmitters that cause the smooth
  muscles around blood vessels to relax, lowering
  blood pressure.
• When too low, neurotransmitters are released that
  cause the smooth muscles to contract, elevating
  blood pressure.
• With the endocrine/excretory system
• Hormones produced by the heart and other organs
  cause kidneys to remove more water from the blood
  when blood pressure is too high, reducing blood
  volume and lowering blood pressure

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Disorders

• Disorders of the circulatory system are very
  common
• High Blood Pressure
• Heart Attack
• Stroke
• Most stem from atherosclerosis fatty deposits
  (plaque) builds up on walls of arteries,
  obstructing blood flow, increasing blood pressure
  and risk of blood clots

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High Blood Pressure

• Also known as Hypertension
• Forces heart to work harder, which may weaken or
  damage the heart muscle and vessels
• More likely to develop heart disease and
  increased risk of heart attack and stroke

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Heart Attack

• A medical emergency
• Coronary arteries (supplying heart blood) bring
  oxygen and nutrients to the heart muscle itself
• Blockage of coronary artery may damage or kill
  part of heart muscle (myocardium) due to lack of
  oxygen heart attack
• Symptoms include chest pain/pressure, feeling of
  heartburn/indigestion, sudden dizziness, or brief
  loss of consciousness

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Stroke

• Blood clots may break free from vessels and get
  stuck in a blood vessel leading to a part of the
  brain stroke
• Brain cells relying on that vessel may begin to
  die from lack of oxygen and brain function in
  that region may be lost
• Strokes can also occur when a weakened artery in
  the brain burst, flooding the area with blood

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Prevention

• Cardiovascular diseases are easy to prevent
• Exercise increases respiratory systems
  efficiency
• Weight control reduces body fat and stress
• Sensible diet low in saturated fat reduces risk
  of heart disease
• Not smoking reduces risk of heart disease