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Heart Beat & Blood Flow
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Heart Video
Pulmonary
Artery
Lungs
Pulmonary
Vein
Right
Ventricle
Left
Atrium
Right
AV
Valve
Left AV
valve
Right
Atrium
Left
Ventricle
Vena
Cavae
Aorta
Body
Use Page 320 of your text book to label your heart
diagram located in your workbook…
The Heart…
muscular organ, size of your fist
 surrounded by a fluid-filled membrane:
pericardium which reduces friction
1. Circulation
 PULMONARY CIRCULATION
 deoxygenated blood pumped from the right
side of the heart to the lungs via the
pulmonary arteries
 blood picks up oxygen (oxygenated) and
travels back to the left side of the heart via
the pulmonary veins.
 the pulmonary arteries are the only group of arteries that carry
deoxygenated blood
 the pulmonary veins are the only group of veins that carry
oxygenated blood

SYSTEMIC
CIRCULATION


left side of heart pumps blood
to the entire body via the
aorta (largest artery)
from the aorta blood is
diverted to:
a) coronary arteries - serve
heart tissue
b) upper body arteries
c) lower body arteries
d) Hepatic/Portal system
(digestive)

two large veins: the superior and inferior vena cava return
blood to the right side of the heart
Heart Beat
• The stimulus that triggers a heart beat is an electrical
signal from a bundle of nerve tissue in the right wall of
the atrium.
•This bundle is called the Sinoatrial node (SA node) or
the pacemaker (because it sets the pace for our heart
beat).
Heart Beat
• The electrical signal from the SA node causes muscle
cells to contract and relax rhythmically.
• The signal leaves the SA node and spreads out over
the left and right atria and makes them contract
simultaneously.
Heart Beat
• As the atria contract, the signal reaches the
atrioventricular (AV) node.
• The AV node sends the impulse first through the
bundle of His in the septum and then to the Purkinje
fibers along the outside of the left and right ventricles.
Heart Beat
• The signal traveling along the Purkinje fibers causes a
simultaneous contraction of the left and right
ventricles.
• The contractions and relaxations continue
rhythmically 70-90 times a minute.
Heart Animation
Heart Beat Sounds
• Our heart beat is a long and loud
“lub” followed by a “dub” sound.
• The “lub” sound is made by the
sudden closing of the AV valves
and the opening of the semi lunar
valves. This happens right after
atria contract.
• The “dub” sound is made by the
closing of the semilunar valves and
the opening of the AV valves. This
happens right after the ventricles
contract.
• See and hear an actual heart beat
here!
If a valve does not close completely, then
a murmur is detected
 This murmur is the sound of blood rushing
backwards through a valve, and creates a
gurgling sound

Reading a heart beat - Electrocardiogram
• The voltage change in the heart can be measured by
by electrocardiogram (ECG).
• The heart emits different voltages as muscles contract
and relax, which are observed on a graph.
• You will need to know how to read one!
Reading a heart beat - Electrocardiogram
External Regulation of Heart Rate

The S.A node is regulated externally by the
parasympathetic and sympathetic nerves
which conduct electrical impulses from the
medulla oblongata of the brain
Stress
Relaxed
Activates
sympathetic
nerves
Activates
parasympathetic
nerves
Signals to S.A
Node to increase
H.R
Signals to S.A
Node to
decrease H.R
BENEFIT OF CARDIOVASCULAR EXERCISE
Why do doctors say we need cardiovascular
exercise at least 3 times a week? The answer
lays in our hearts!
Cardiac Output and Stroke Volume
Cardiac output = amount of blood pumped by heart (ml/min)
Cardiac output is an indicator of the level of oxygen being
delivered to our body and the amount of work the body’s
muscles can perform.
Two factors affect cardiac output: heart rate and stroke volume.
Cardiac Output = heart rate x stroke volume
Cardiac Output and Stroke Volume
Heart rate = number of heartbeats per minute.
Stroke volume = amount of blood forced out of the heart with each
heartbeat.
Stroke volume is affected by how much blood returns to our heart
and how strong the ventricles contract to push the blood out.
Cardiac Output and Stroke Volume
The average cardiac output is 4900mL a minute (remember we have
about 5000mL of blood in our body).
Because cardiac output is heart rate x stroke volume, the larger an
individual’s stroke volume is, the smaller the heart rate has to
be.
(Don’t take my word for it…..try a calculation yourself and see!)
Ex: Calculating Cardiac Output

Tom’s heart has a stroke volume of 50 mL
and a heartrate of 100 beats per minute.
Calculate his cardiac output.
Cardiac Output and Stroke Volume
Regular cardiovascular exercise enlarges the ventricular chambers,
increases the elasticity of the ventricles, and strengthens the
ventricle walls.
With stronger ventricles, the heart has more power to push out
more blood on each contraction (increase stroke volume).
Because of this, a low heart rate is an indicator of high
cardiovascular fitness, because as stroke volume increase,
heart rate should decrease!
Cardiac Output and Stroke Volume
Knowing what you do about cardiac output, who is the most
physically fit person:
Individual
Heart rate
(beats/min)
Stroke Vol.
(ml/beat)
Cardiac OP
(ml/min)
A
70
70
4900
B
98
50
4900
C
35
140
4900
Blood Pressure

Sphygmomanometer
– measures blood pressure
– gauge that measures the pressure that blood
exerts during ventricular contraction (systolic
blood pressure) ~ 120 mm Hg
– also measures pressure during ventricular
relaxing (diastolic blood pressure) ~ 80 mm Hg

Why would internal hemorrhaging
(bleeding) cause diastolic blood pressure to
drop?

Blood pressure changes as the heart beats:
When left
ventricle
pumps out
the blood
Pressure
rises to a
MAXIMUM
SYSTOLIC blood
pressure
When left
ventricle is
filling with
blood
Pressure falls
to a
MINIMUM
DIASTOLIC
blood pressure

Blood pressure is described by two numbers:
– Example of a healthy individual:
120 means:
80
– systolic blood pressure is 120 mm Hg
– diastolic blood pressure is 80 mm Hg

healthier values are usually lower, although it is possible to
have blood pressure that is too low
Measuring Blood Pressure
Blood Pressure

Two factors affecting blood pressure
1. Cardiac output
–  cardiac output,  blood pressure
2. Arteriolar Resistance
–  diameter causes a  blood pressure
–  diameter causes a  blood pressure
How to measure your blood pressure:

https://www.youtube.com/watch?v=Gmic
13mvsgo
Hypertension
Caused by increased resistance to blood
flow which results in increased blood
pressure
 High blood pressure can lead to weakened
blood vessels


Major cause is diet, but may also be
hereditary
Response to Exercise

NS stimulates adrenal gland to release
adrenaline (epinephrine)
– This stimulates the release of RBC’s
– Increased RBCs = increased O2 transport
– Adrenaline also increases heart rate and
breathing which increases O2 transfer rate
through body
Regulation of Blood Pressure

Nervous system responses cause either
increased outflow of blood from arteries
(sympathetic NS) or decrease heart rate
and stroke volume (parasympathetic NS)
Why is high blood
pressure a problem?
 The heart must work
harder to pump blood
which can cause it to
enlarge and weaken
 There is a increased force
on the blood vessels,
which can cause them to
weaken and increase the
risk of stroke or heart
attacks
 Increase chance of blood
clot formation

Thermoregulation
Let’s Try This
-
We know that stroke volume increases with
cardiovascular fitness.
The higher the stroke volume, the quicker it takes
your heart rate to return to rest after exercise.
We are going to do a little test with the blood
pressure lab (open your book to page 278 to see
what we are going to do).
Copy these charts
Condition
Blood Pressure
(mmHg)
Heart Rate
(beats/minute)
Cardiac Output
(mL/min)
Stroke Volume
(mL/beat)
Control (regular)
Caffeine
Physical Activity
Nicotine
Resting Heart Rate
(beats/minute)
4500 (female)
5500 (male)
To Do:

Textbook Questions p. 335 #2, 5, 7, 10