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 Systole
Atrial Diastole
Ventricular Diastole
Atrial 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 beat
2. 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 Control
1. 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
SA node
(Sinoatrial node)
Atrioventricular
Bundle
Purkinje
Fibres
AV node (atrioventricular
node)
Atrioventricular
Bundle
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.
2.
3.
4.
5.
Right atrium, left atrium
Right ventricle, left ventricle
Atrioventricular valves
Semilunar valves
Pulmonary trunk, aorta, pulmonary veins, superior
vena cava, inferior vena cava
6. Chordae Tendineae
7. Septum
8. 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 parts
1. The Sympathetic Nervous System
2. 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
• Parasympathetic
• Heart Rate Low
• Blood is around
your digestion
system
• Suddenly a Ninja
• Sympathetic
jumps though the
window and tries to
KILL you
• Hormones released
into your blood
• Heart rate is faster
• Blood moves into
muscles to Beat this
Ninja up
• You easily Beat the
Ninja and go back to • Parasympathetic
watching TV
• 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
Renal Vein
Iliac Vein
Jugular Vein
Coronary Vein
and
Hepatic Vein
Provincial Exam Questions
• Blood Velocity
Blood Flow
– 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
Capillary
Venule and Vein
Arteriole
Arteries
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 contract
2. 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
Normal
Less than 120
Prehypertension
120-139
High Blood
Pressure
Stage 1
140 – 159
Stage 2
160 or Higher
And
Or
Diastolic
Less than 80
80 – 89
Or
Or
90 – 99
100 or Higher