Heart Function L1

1. TOPIC 5 – HEART FUNCTION
Understand the structure of the heart and the cardiac cycle
Learning Outcomes:
A – Identify, describe and explain the structure
of the heart and the cardiac cycle
CJ, CE
B – Identify and describe the structure of the
heart and the cardiac cycle
SF, AC, JH, RM
C – Identify the key terms of the structure of
the heart and the cardiac cycle
JB, JB, AA, GB
Do Now Task – Explain the blood redistribution
mechanism

2. DO NOW TASK – EXPLAIN THE BLOOD REDISTRIBUTION MECHANISM
Understand the structure of the heart and the cardiac cycle

3. BACKGROUND
Understand the structure of the heart and the cardiac cycle
1 • Muscles Contract – requiring energy
2 • Muscles need oxygen to make energy
3 • Oxygen found in air
4 • Lungs breathe in air
5 • Oxygen transported around body in blood
6 • How do we get the oxygen rich blood around?

4. RECAP – INFORMATION ON THE HEART
Understand the structure of the heart and the cardiac cycle
 The heart is a 2-sided pump.
 The right side has deoxygenated blood
 The left side has oxygenated blood
 Heart – Lungs – Heart = Pulmonary Circulation
 Heart – Body – Heart = Systemic Circulation
 Ventricles are more muscular than the atria – Why?
 Left Ventricle has a thicker muscular wall to the Right Ventricle
 There are valves in our heart that keep blood flowing in the right
direction
 Pressure through contraction pushes blood
through these valves

5. STRUCTURE OF THE HEART
Understand the structure of the heart and the cardiac cycle

6. CARDIAC CYCLE
Understand the structure of the heart and the cardiac cycle

7. CARDIAC CYCLE
Understand the structure of the heart and the cardiac cycle
The heart is mainly composed of cardiac muscle and contracts like
skeletal muscles. It also has the ability to generate its own
electrical signal for conduction, not needing the nervous system.

8. SAN – SINO-ATRIAL NODE
Understand the structure of the heart and the cardiac cycle
Is a small mass of specialised
cardiac muscle found in the right
atrium.
This sets the hearts rhythm and
can be known as a pacemaker.
Intrinsic heart beat – comes from
within the heart.
Myogenic – because it occurs
without nervous simulation.
Sends out a wave of impulses
causing the atria to contract

9. SAN – SINO-ATRIAL NODE
Understand the structure of the heart and the cardiac cycle
This period of contraction is
called Systole.
Therefore the atria contracting is
called atrial systole.
The impulse cannot spread into
the ventricles because the valves
act as a barrier.

10. AVN – ATRIO-VENTRICULAR NODE
Understand the structure of the heart and the cardiac cycle
The impulses reach another mass
of specialised tissue called the
AVN.
This conducts the impulse from
the atria across the ventricles.
There is a pause between these 2
contractions – WHY?

11. BUNDLE OF HIS & PURKINJE FIBRES
Understand the structure of the heart and the cardiac cycle
The impulse from the AVN passes
down the hearts septum via the
Bundle of His to the tips of the
ventricles.
Here it branches out to spread
through the ventricle walls
through the Purkinje Fibres.
It is these fibres that carry the
impulse that makes the ventricles
contract

12. NERVOUS SYSTEM
Understand the structure of the heart and the cardiac cycle
Timings of the hearts intrinsic contractions can be altered through
the autonomic nervous system and hormones.
Parasympathetic branch – Vagus Nerve sends impulses to slow
down intrinsic rhythm. Can also decrease force/strength of
contraction
Sympathetic branch – Speeds heart rate up by stimulating SAN,
can also increase strength of contraction
Adrenalin can also increase speed and force of contraction from
the SAN.

13. CARDIAC CYCLE
Understand the structure of the heart and the cardiac cycle
The time it takes for the hearts
chambers to go through a complete
cycle of contraction (systole and
diastole) is called the cardiac cycle.
At rest and with a normal heart rate
the cardiac cycle lasts 0.8 seconds.
0.5 is diastole, where the heart is
filling up
0.3 systole, contraction.