1. Introduction to the circulatory system

2. Aims of the seminar
Recap on previous seminar ‘the muscle fibres in the body’.
To introduce the term ‘circulatory system’.
To give a detailed explanation of the structure and functions of the circulatory system.
To examine the direction of blood flow through the heart.

3. Muscle Fibre Types
Muscles are composed of thousands and thousands of individual muscle fibres
Not all fibres are alike in structure and function
Can be classified into 3 types:
Type I
Type IIA
Type IIB

4. Type I Fibres Slow twitch or slow oxidative fibres: Red in colour
Large amounts of mitochondria, myoglobin and capillary network
Work slowly (split ATP at a slow rate)
Able to repeatedly contract or maintain contraction for a long duration
High resistance to fatigue
Fibres work mainly aerobically

5. Type IIA Fibres Fast twitch or fast oxidative glycolytic fibres (FOG)
Similar to Type I Fibres
Red in colour
Large amounts of myoglobin, many mitochondria and capillaries
Resistant to fatigue
Work rapidly to split ATP, fast contraction speed
Work aerobically or anaerobically
Used in high intensity, short duration activities such as 200m swim or 800m

6. Type IIB Fibres Fast twitch or fast twitch glycolytic (FTG) fibres
White in colour
Low number of myoglobin, few mitochondria, few capillaries
Fatigue easily
Fast contraction speed, split ATP quickly
Much stronger force of muscle contraction
These are used for activities of a very high intensity (anaerobic)
e.g. powerlifting or 100m sprint

7. Fibre Mix Most skeletal muscle is a mixture of all 3 types
Proportion of types varies in relation to usual action of the muscle
For example – the postural muscles of the neck and back and leg have a higher proportion of Type I Fibres
Why do you think this is?

8. The function of the circulatory system
The circulatory system has three major function:
Transport
Moving things around the body in the blood stream such as oxygen and nutrients like glucose.
Body temperature control
Thermoregulation, moving blood near the skin cools down the body. That’s why you look redder when you exercise heavily.
Protection
Moving anti-bodies around the body fighting diseases and clotting cuts.

9. The structure of the heart
Oxygenated blood has more oxygen and is found in the arteries (except in the pulmonary artery).
Deoxygenated blood has less oxygen and is found in the veins (except in the pulmonary vein.)

10. The cardiovascular system: HEART
The heart
Situated in the left-hand side of the chest
Muscular pump whose purpose is to drive the blood into and through the arteries, to deliver it to the tissues and working muscles
Considered as two separate pumps
Two chambers on the right, and two chambers on the left side
What are they?

11. The cardiovascular system: HEART
Structure of the Heart
Surrounded by sac known as the pericardium, which prevents friction as the heart beats.
Heart wall is made of:
Epicardium (outer layer)
Myocardium (strong middle layer)
Endocardium (inner layer)
Right separated from left by Septum

12. Strokes of the heart
Heart rate per minute is how many time the heart beats in one minute.
Stroke volume is the amount of blood pumped from the heart per beat.
Cardiac output is the amount of blood pumped from the heart in one minute.
Cardiac output = Stroke volume + Heart rate

13. Double circulation
Every time the blood goes around the body it goes through the heart twice, this is known as a double circulation.

14. Circuits of the body
There are two circuits of the body you need to know:
Systemic
The main circuit of the body, it carries oxygenated blood around the body through arteries.
It carries deoxygenated blood back to the heart and lungs through veins to be deoxygenated in the pulmonary system.
Pulmonary
Consists of the heart and lungs, deoxygenated from the heart to the lungs to be oxygenated. The oxygenated blood then goes back to the heart to be pumped around the body.

15. The flow of blood through the heart and around the body.

16. Blood Flow Through the Heart
Vena Cava – Superior/Inferior
Right Atrium
Tricuspid Valve
Right ventricle
Pulmonary Artery
LUNGS

17. Blood Flow Through the Heart
Pulmonary veins
Left Atrium
Bicuspid/Mitral/Atrioventricular valve
Left Ventricle
Aorta
MAJOR ORGANS

18. The Heart Made of cardiac muscle (myocardium)
Has it’s own blood supply
Two upper thin walled chambers – atria
Two lower thick walled chambers – ventricles
Atria collect blood from the body – attached to veins
Ventricles send blood to the body – attached to arteries

19. The Heart Right side – deoxygenated Left side – oxygenated
Separated by a thick walled septum
Right atrium and ventricle connected by tricuspid valve
Left atrium and ventricle connected by bicuspid (mitral) valve
Cuspid valves held shut by Chordae Tendinae
Left ventricle is thicker than the right

20. Vessels of the Heart Pulmonary artery* Pulmonary vein
Superior and Inferior Vena cava
Aorta*
*Semi-lunar valves

21. Control of the Heart
Myogenic-Initiated from inside the heart as opposed to nervous stimulus outside
Initial Stimulus originates in the Sinoatrial node (SA node)
Pacemaker determines heart rate
Wave of excitation across both atria causes them to contract

22. Control of the Heart Sinoventricular node (SV node)
Sends waves of excitation along Purkinje Fibres which collectively make up the Bundle of Hiss. Along septum, radiate upwards
Ventricles contract
Both atria and both ventricles contract at the same time
Systole-contraction of heart
Diastole-Relaxation/filling of the heart

23. Next Seminar
Introduction of valves that Transport the blood through the body.