chapter 13 heart rate and blood pressure. the cardiac cycle each heartbeat is called a cardiac cycle...
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Chapter 13
Heart Rate and Blood Pressure
The Cardiac Cycle
• Each Heartbeat is called a Cardiac Cycle• Step 1: the two atria contract at the same time– This pushes blood into the ventricles
• Step 2: the two ventricles contract at the same time– The Right Ventricle pushes the blood into the Lungs– The Left Ventricle pushes the blood into the Body
• Step 3: all the chambers relax– The atria fill with blood returning to the heart
• Systole This refers to the heart muscle contracting
• Diastole This refers to the heart muscle relaxing
Ventricular SystoleAtrial Diastole
Ventricular DiastoleAtrial Systole
What Controls the Heartbeat?• There are two areas that control how fast the
heart beats.1. Intrinsic Control inside the heart there are
nerves that control the heart beat2. Extrinsic Control a part of the brain controls
the heart beats
Intrinsic Control• In the upper right atrium there is a sinoatrial node
(SA node)• In the lower right atrium there is a atrioventricular
node (AV node)• These nodes are made of muscle but is mostly
made of nervous tissue
Intrinsic Control1. The SA node starts the heartbeat and sends out an
electrical pulse that causes the atria to contract.2. When the electrical pulse reaches the AV node
there is short delay. This delay allows the atria to finish their contraction.
3. The AV node sends the signal down the Atrioventricular bundle, which then branches into Purkinje Fibres.
4. This signal sent by the AV node causes the ventricles to contract
Purkinje Fibres
Atrioventricular Bundle
Atrioventricular Bundle
AV node (atrioventricular node)
SA node (Sinoatrial node)
Its time for a Review Break• Draw a picture of the heart from your memory.• No books no notes. Just a pen and paper.
1. Right atrium, left atrium2. Right ventricle, left ventricle3. Atrioventricular valves4. Semilunar valves5. Pulmonary trunk, aorta, pulmonary veins, superior
vena cava, inferior vena cava6. Chordae Tendineae7. Septum8. AV node and SA node
Extrinsic Control• A part of the brain controls the heart and
controls how fast or slow the heart rate will be• The part of the brain that controls the heart is
called the Medulla Oblongata
• The heartbeat is part of your autonomic nervous system– The autonomic nervous system is the part of the
nervous system that you do not think about. It happens automatically
– Ex./ heartbeat, peristalsis, gall bladder squirting bile.
• The autonomic nervous system has 2 parts1. The Sympathetic Nervous System2. The Parasympathetic Nervous System
The Parasympathetic Nervous System• The is the system that takes over when you
are resting.– Your body is relaxed– You are at rest– Your body sends its blood to its stomach so it can
digest food– Your heart rate decreases because you are at rest
The Sympathetic Nervous System• This is the system that takes over when something
is threatening you and your “flight or fight” reaction takes over or if you are very stressed (physically or mentally)– Your body sends blood to the large muscles in your body,
so it can have more energy to run or fight– Your body releases several different hormones that
cause an increase in heart rate• Brain sees or smells or hears something that causes fear or
stress. It sends a message to the adrenal glands to release hormones like epinephrine and norepinephrine. These hormones increase heart rate
• You are Eating and watching TV
• Suddenly a Ninja jumps though the window and tries to KILL you
• You easily Beat the Ninja and go back to watching TV
• Parasympathetic
• Sympathetic
• Parasympathetic
• Heart Rate Low• Blood is around
your digestion system
• Hormones released into your blood
• Heart rate is faster• Blood moves into
muscles to Beat this Ninja up
• Heart rate starts to slow down
The Pulmonary Circuit• Blood leaves the Right Ventricle to go to the
Lungs It goes through the pulmonary Trunk• The pulmonary Trunk branches off into
pulmonary arteries• The pulmonary arteries Branch and branch until
they are capilliaries in the lungs to exchange gases
• The blood returns to the Left Atrium oxygenated
• The blood comes back through the pulmonary Veins
Systemic Circuit• Systemic means spread throughout this refers to
the cells in our body. They are spread throughout our bodies
• Blood leaves the heart via the Aorta• Blood then branches off into many different arteries• Blood comes back to the heart through many
different veins
• Arteries– Subclavian Artery– Mesenteric Artery– Renal Artery– Iliac Artery– Carotid Artery – Coronary Arteries
• Veins– Subclavian Vein– Hepatic Portal Vein and Hepatic Vein– Renal Vein– Iliac Vein– Jugular Vein– Coronary Vein
Provincial Exam Questions
Blood Flow• Blood Velocity– Arteries have the highest blood flow– It gets slower and slower the narrower the tubes
get until capillaries, which is the slowest– The capillaries turn to venules and the blood starts
to move faster– The venules turn to veins and it is moving a little
faster
Arte
ries
Arte
riole
Cap
illar
y
Venu
le a
nd V
ein
Blood Flow• Blood Pressure– The pressure that is put against the wall of the blood
vessel– Arteries will have the highest pressure– Veins will have the lowest pressure– Two types of pressure
1. Systolic Pressure Ventricles contract2. Diastolic Pressure Ventricles relax
Blood Flow• Blood Pressure– The pressure is high coming out of the heart and it
slowly decreases– The pressure decreases because it gets farther
away from the Heart– Pressure gets very low in the Veins. The body
relies on the veins and the muscles to move blood back to the heart
Blood Pressure Problems• Hypotension– Low Blood Pressure– Blood vessels widen– Caused from hormone changes, heart problems
• Hypertension– High Blood Pressure– Narrow blood vessels– Caused from Stress, obesity, hormone problems
Category Systolic Pressure DiastolicNormal Less than 120 And Less than 80
Prehypertension 120-139 Or 80 – 89High Blood
PressureStage 1 140 – 159 Or 90 – 99Stage 2 160 or Higher Or 100 or Higher
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