Download The Heart - csfcbiology

Starter - review
Using these key words write 3 sentences
about the human circulatory system.
What are the parts of the circulatory system?
What is its function (job)?
How is it designed to do this function ?
Words: Closed, transport, pump, blood,
double, pressure, oxygenated, deoxygenated,
blood vessels
Lesson Aims
How is the structure of the heart related
to its function?
How much
blood5.6
does the
human
litresbody
contain?
The Heart
Where is it?
• Between the two lungs
• Enclosed by the
PERICARDIUM
• Pericardial fluid is secreted
between them to aid movement
• The pericardium protects the
heart from over expansion
Hold your hand in front of
you and make a fist. Squeeze
and relax. How long can you
do this for?
• The walls of the heart are
made of cardiac muscle
(MYOCARDIUM)
• Only found in heart
• Never tires but can’t tolerate
lack of O2.
Activity
Drag the labels to the right place to complete the
diagram and the key
Internal
Features
Semi-lunar valves
(bicuspid valve)
Septum
Pericardial membranes
Internal
Structure
Task: Add
labels to
the
diagram
Watch this Video
• Blood flow through the heart
How far does
nearly
your 12,000
blood
miles
travel
in one
day?
Blood flow through the heart
• Blood comes into the heart from the body
• It then has to pass to the lungs to collect
oxygen
• This is called a double circulatory system
• After it returns to the heart it leave again to
be transported to the body.
Task: Draw a flow diagram to show the flow of blood
through the heart. You should start and finish with the
body.
Body
Atrium- receives blood from veins
Ventricle- pumps blood into arteries
Left
Vena cava
Deoxygenated blood
Right
atrium
Oxygenated blood
atrium
Tricuspid valve
Bicuspid valve
Right ventricle
Left ventricle
Pulmonary artery
aorta
lungs
body
External Features
Task: Add
labels to your
diagram
External Structure
Heart
Dissection
How
many
around
35
times
does
the
million
times
heart beat in a
lifetime?
Your sheep’s
heart
What external
features can you
identify?
A
B
C
D
How much
a million
blood
does the
barrels
of in
heart
pump
a blood
lifetime?
E
F
External Features
FRONT
Apex
BACK
Intact Heart…
This shows the heart from
the front, with the portion
on the right of the picture
being the left side of the
heart and vice versa.
The aorta is clearly visible at
the top, with an atrium on
either side, while the
ventricles are in the
bottom left.
The first incision…
… is along the right
ventricle.
The right ventricle can be
identified by squeezing
the heart, since the
myocardium on the right
side is much less rigid
than that of the left
ventricle.
This allows us to see the
tricuspid valve and the
right ventricular outflow
tract which includes the
pulmonary valve.
Longitudinal Cut…
The right ventricle has been
cut open from the bottom
towards the top.
In this picture, the
myocardium is being held
back. My finger is stuck
underneath one leaflet of
the tricuspid valve, which
leads to the pulmonary
valve.
The Tricuspid Valve up close…
The tricuspid
valve allows
blood to
flow from
the right
atrium into
the right
ventricle.
Pulmonary Valve…
When the heart is
contracting, the
pulmonary valve is open
because the blood pushes
the cusps out of the way.
After contracting, the
ventricles begin to relax
and the pulmonary valve
closes and prevents backflow (called regurgitation)
of blood into the
ventricle.
The Left Ventricle…
This longitudinal incision
extends from the
bottom to the top of
the left ventricle, then
continues up into the
atrium to allow us to
view the entire left
heart.
The Mitral (bicuspid) valve…
The mitral valve
prevents blood from
flowing back into the
left atrium
The mitral valve is
positioned between
the atrium (at top)
and ventricle (at
bottom).
Left Ventricular Outflow…
Blood flows into the
ventricles by
passing through
the mitral valve,
but can you see
where it flows
out? This is a bit of
a trick question
because the
outflow tract is
hidden behind the
mitral valves
What to do next!
• Answer the questions
on the worksheet
• Match the keywords
and their definitions
1. Why are pig or sheep hearts used to study the anatomy of the
human heart?
2. How can you tell which side of the heart is the ventral surface?
3. How many chambers are found in the mammalian heart? What
other group of organisms would have this same number of
chambers?
4. What is the advantage in having this number of chambers
compared to organisms with a fewer number of chambers?
5. Which chambers are the pumping chambers of the heart?
6. Which chambers are the receiving chambers of the heart?
7. How do the walls of the atria compare with the walls of the
ventricles and why are they different?
8. What is the purpose of heart valves?
9. Name & compare the heart valves found between the upper &
lower chambers of the right and left sides of the heart.
10. Vessels that carry blood away from the heart are called
__________, while __________ carry blood toward the heart.
11. Which artery is the largest and why?
12. What is the purpose of the coronary artery and what results if
there is blockage in this vessel?
13. Use the diagram of the heart below to trace blood flow
through the heart:
Questions to answer
after the dissection
Oxygenated
Deoxygenated
Pulmonary vein
Relating to the lungs
The valve which prevents backflow from the pulmonary artery to the right ventricle
Separates the two sides of the heart, keeping oxygenated and deoxygenated blood apart.
Pulmonary artery
Blood vessels on the surface of the heart which supply the heart itself with blood.
Aorta
Vena cava
Ventricle
Blood without oxygen (usually coloured blue on a diagram)
The valve which prevents backflow from the right ventricle to the right atrium
The major blood vessel which carries oxygenated blood from the heart to the body.
Atrium
Relating to the body
Mitral valve
One of the bottom two chambers of the heart
Tricuspid valve
Blood with oxygen (usually coloured red on a diagram)
Pulmonary valve
One of the top two chambers of the heart
Aortic valve
Septum
Myocardium
Pulmonary
Systemic
Blood vessel which returns with oxygenated blood from the lungs to the left atrium
The muscle of the heart, cardiac muscle which never fatigues (gets tired)
Blood vessel which leaves the right ventricle transporting deoxygenated blood to the lungs
Valve which prevents backflow from the aorta to the left ventricle
The valve which prevents backflow from the left ventricle to the left atrium
Coronary artery
The major blood vessel which returns deoxygenated blood to the heart from the body
Activity
Drag the labels to the correct numbered boxes
on the diagram of the blood system
The Circulatory System
• Valves prevent backflow
• When pressure in ventricles exceeds that in
the atrium the bicuspid/tricuspid valves
shut
• This makes the first noise we hear with a
stethoscope.
• Tendinous chords attached to Papillary
Muscles prevent valves turning inside out.
• Semi-lunar valves prevent backflow in the
pulmonary artery and dorsal aorta.
• Closure of these makes the second noise of
the heart beat. (hence lub-dub)
• The heart requires a lot of oxygen and
nutrients
• Some oxygenated blood leaving the left
ventricle goes directly to the heart through
the coronary Arteries.
• These branch many times to supply oxygen
and nutrients throughout the cardiac
muscle.
• When these get blocked a heart attack is
likely and by-pass surgery required.
Task: Label the
diagram of the
circulatory
system
• Follow the red
blood cell
through the
circulatory
system
The Cardiac Cycle
• Cardiac muscle contracts without nervous
or hormonal stimulation these are
MYOGENIC contractions.
• The muscle cells work together to produce
the heartbeat (cardiac cycle)
• Heart beat animation
• The cycle starts at the Sinoatrial
node (SA node)
• A small piece of tissue with a
inherent rhythm of contraction.
• The rhythm can be slowed or sped
by nervous impulses and hormones.
• The SA node is also known as the
pacemaker
• The SA node generates waves of
electrical impulses called cardiac
impulses.
• The electrical impulses pass over the atria
until they hit the Atrioventricular septum
• This is non-conductive with only one gap in it
called the Atrioventricular Node (AV node)
• This is the only route for cardiac impulse
transmission.
• This is the second pacemaker and can take
over if the SA node malfunctions
• Conducting sytem of the heart animation
Cardiac Cycle
• Cardiac Cycle animation
Systole (contraction)
a)
•
•
•
Atrial systole
Atria contract
Semi-lunar valves closed
Blood forced from the atria into the
ventricle
b)
•
•
•
Ventricular systole
Ventricle contracts
Blood is forced into arteries
Bicuspid and tricuspid valves closed
Systole (contraction)
• Cardiac impulse relayed from AV node over the
ventricles through the Bundle of His (atrioventricular
bundle)
• Bundle branches into Purkinje (Purkyne) Fibres
• The cardiac impulse passing through the fibres causes
a wave of contraction.
• It starts at the apex of the heart and rapidly passes
over the ventricles (ventricular systole)
• Regions close to the AV node have thin fibres
therefore slow the impulse so all ventricle contracts at
once.
Diastole (relaxation)
• Heart relaxes and fills with
blood from the veins.
• Semi-lunar valves closed to
blood entering through
arteries.
• Cardiac Cycle Tutorial
• Task: Order the diagrams of
the cardiac cycle and
annotate.
Pressure Changes
• You need to be able to explain the pressure
changes in the heart in. terms of what is
happening inside the heart
• You also need to be able to identify where the
valves open and close and explain why in terms of
pressure
• Task: Label this diagram
of pressure changes in the
heart. What is happening
at A, B, C and D?
Answer these questions:
• Explain the
difference in
pressure between
the atria and the
ventricles.
• What causes the
valves to open and
close?
Pressure changes in the heart
• Atrium has lower max pressure as only pumps
blood into the ventricle; ventricle pumps to the
whole body.
• Closure of the valves is a passive process; it
depends on the relative pressures on either side
of the valve.
• The Atrioventricular valves close when the
pressure in the ventricles is higher than in the
atrium.
• They open when the pressure is higher in the
atrium than the ventricle.
• Cardiac Cycle Overview
An Electrocardiogram - ECG
• Cardiac muscle contracts as a result of electrical stimulation,
this is detected with recording electrodes.
• Electrical signals are shown on a cathode ray oscilloscope or a
chart recorder; this is an ECG.
R
P
Q
T
S
P
A single cardiac cycle: P = atrial systole; QRS = wave of ventricular
systole; T = ventricular diastole
• heart rate calculated from interval between P waves
ECG changes in a diseased heart are used by doctors for diagnosis
Interpreting an ECG Trace
• Electrocardiogram animation
Cardiac output
Cardiac Output = Stroke Volume X Heart rate
( Volume of blood
leaving left ventricle
with each beat)
(beats per
minute)
• Average resting for a man is 75cm3 (stroke) and 70
beats per minute (rate)
• When exercising both stroke and rate increase
• The fitter a person is the lower the resting rate
and higher stroke volume.
Heart rate is measured by the pulse
As the heart beats, it releases regular surges (increased
volumes) of blood. As these pass along the arteries, the
vessel must stretch to allow it to pass. This stretching
pushes on the skin, which we sense as a pulse.
Skin surface
Blood flow
Blood flow
Control of the heart beat
• Although the heart has its own rhythm it is also
regulated by the nervous and hormonal systems.
• Sensory receptors in the walls of heart and blood
vessels are sensitive to changes in blood pressure
• These send impulses to the CARDIORESPIRATORY
CENTRE in the medulla oblongata
• A vagus nerve branch leads to the SA node.
• The vagus nerve is part of the Parasympathetic
Nervous System and so is an inhibitory nerve,
impulses slow the heart rate.
• Branches of a sympathetic nerve also lead
to the heart, these impulses will speed up
the heart rate.
• When excited or in danger the sympathetic
nervous system also stimulates the release
of Adrenaline from the adrenal glands.
• Adrenaline increase the strength (stroke)
and speed (rate) of the heart.
The cardiac output is therefore modified by the
parasympathetic and sympathetic nervous
systems.
• The cardiac output also varies with the Venous
Return (volume of blood returning to heart)
• If venous return is high, walls of atrium are
stretched, which is detected by stretch
receptors.
• The effect of this is that the heart beats faster;
this is called the Bainbridge reflex.
• High venous return also stretches the ventricle
wall, this results in the ventricle contracting
stronger, giving a greater stroke volume; this is
called the Frank-Starling Effect.