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

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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