 per minute

about 120

 Nerves act as  Vagus nerve  Sympathetic nerve

brake and accelerator slows heart rate speeds up heart rate

2

 The intrinsic impulses of the SAN set the heart beat  These timings can be altered through the neural control & hormones.

 Central to the regulation of heart rate is the Cardiac Control Centre in the medulla- made up of 2 components.

Autonomic Nervous System Parasympathetic SLOWER Sympathetic FASTER

Via Vegus Nerve Acetylcholine  adrenaline/noradrenaline

These both act on the SA node to change HR

 Think of a cyclist going down hill.

 Speed of the bike is like the speed of your heart  Brakes- vagus nerve  Pedals- sympathetic nerve  To reduce the speed you use the brakes  To speed up you pedal faster  To go fast downhill you take the brakes off completely (vegus nerve) and pedal faster (sympathetic nerve)

Medulla Exercise - blood CO 2 levels rise Detected by chemoreceptors Decreased vagus impulses to SAN - lets heart beat faster Increased sympathetic impulses to SAN - lets heart beat even faster 5

Medulla Increased vagus Stop exercise – blood pressure falls Detected by baroreceptors Decreased sympathetic impulses to SAN - allows heart rate to slow impulses to SAN - lets heart beat slower 6

Sympathetic system Parasympathetic system

 A.Controlled by medulla/cardiac centre  B. Sympathetic pathway increases heart rate  C. By release of adrenaline/noradrenaline  D. Increase stroke volume/ejection fraction  E. Parasympathetic decreases HR  F. By vagus nerve  G. Production of Acetylcholine  H. (Both) act on sino atrial node/SAN

 Increase in C02  Causes increase in blood acidity, decrease in pH.

 Detected by Chemorecepetors  Sends impulse to medulla – Cardiac control centre  Decreases Vegus simulation  Increase sympathetic pulses  Heart rate increases!

*

Breathing rate= respiratory control centre

 The CCC receives information from lots of different sources in the body.



Mechanoreceptors & Proprioceptors

Extent of movement taking place in the muscles. In movement = in HR.



Chemoreceptors

-Detect changes in pH .



Baroreceptors

-stretch receptor based in arteries and vena cava. Detect increases in blood flow and pressure

 CCC responds to information from these sensory receptors during exercise.

 Stimulate the SA Node via sympathetic nerve.

 This causes heart rate and stroke volume to increase.

 Once exercise stops- stimulation of sympathetic nerve decreases and allows parasympathetic vagus nerve to take over and slow heart rate down.

 Adrenaline and noradrenaline are released during times of stress- ‘butterflies’  Prepares body for impending exercise by increasing heart rate and strength of ventricular contraction.

 Mimicking the action of the sympathetic system  Anticipatory Rise

 Action of another hormone Acetylcholine released by Parasympathetic system that slow the heart rate down

Neural Factors; Proprioceptors & mechanoreceptors need more blood.

in muscles relay info to the brain that amount of movement has increased and muscles will Chemoreceptors detect changes in composition of the blood C02 in aorta and carotid arteries Baroreceptors pressure respond to changes in blood

Hormonal factors; Release of adrenaline and noradrenaline increase heart rate and strength of contraction Release of Acetylcholine reduce the heart rate following exercise to

Intrinsic factors

Increase in temperature less viscous blood flows better

 Describe how the parasympathetic and sympathetic nervous pathways control heart rate during a game.

 Explain how levels of CO2 in blood cause heart rate to increase  How does the cardiac control centre regulate heart rate?

 Stroke Volume blood ejected per beat Not all blood in ventricle is ejected..

 Ejection Fraction amount of blood that leaves the ventricle  Cardiac Output – amount of blood pumped out of a ventricle per minute  Heart rate x stroke volume  5 litres resting male

 Explain the terms stroke volume and cardiac output and the relationship between them (3 marks)

 Amount of blood ejected form the ventricle per beat  Amount of blood ejected from the ventricle per minute  Relationship- SV x HR = Cardiac output

 Subject A heart rate= 80bpm; stroke volume =90mls  Subject B heart rate=110bpm; stroke volume = 100mls  Subject C heart rate160bpm; stroke volume=120mls

 When we exercise this will change...

1) More blood enters the ventricle during diastole (venous return) as it is flowing faster round the body 2) Walls of the ventricle stretch and contract more forcibly.

Starlings law of the heart

The greater the venous return, the greater the strength of contraction

.

How does stroke volume increase during exercise?

 Increased venous return  Greater diastolic filling  Cardiac muscle stretched  Greater strength/ force of contraction  Increased ejection fraction

 Increased exercising heart rate and increased stroke volume have a huge impact on Cardiac Output  Heart rate 200bpm  Stroke volumes 180mls  36 litres per minute  Increase in Cardiac Output (Q) is to supply working muscles with oxygen

What are the effects of exercise on the heart?

 heart rate increases  stroke volume increases  due to Starlings Law  cardiac output increase  because cardiac output= SV x HR