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Slide 1

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CONTROL OF
HEART RATE IN
HUMANS
1.1.13…read more

Slide 2

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THE HUMAN HEART
The heart pumps blood around the
circulatory system. Blood supplies the tissues
with oxygen and nutrients such as glucose,
fatty acids and amino acids.
It also removes waste products, such as
carbon dioxide and urea, from the tissues so
that they do not accumulate and inhibit cell
metabolism.…read more

Slide 3

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HUMAN HEART SUMMARY
Blood supplies Removal of waste
tissues with: substances such
Oxygen as:
Nutrients × Carbon dioxide
Glucose × Urea
Fatty acids
Amino acids…read more

Slide 4

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HOW DOES THE HEART ADAPT TO
SUPPLY MORE OXYGEN AND
GLUCOSE?
1. Activity of heart increases in the number of
beats per minute ­ KNOWN AS HEART RATE
2. The heart can increase the strength of its
contractions
3. It can also increase the volume of blood
pumped per beat (stroke volume)…read more

Slide 5

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CONTROL OF HEART RATE
The rate at which the heart beats is affected by a number of
factors:
The heart muscle is myogenic ­ initiates its own attractions.
The heart contains its own pacemaker- SAN (SINOATRIAL NODE)
which is a region of tissue that can initiate an action potential,
which travels down the excitation over the atria walls, through
the AVN (ATRIOVENTRICULAR NODE) and down the Purkyne
/purkinje fibres to the ventricles, causing them to contact. The
heart is supplied by nerves from the medulla oblongata of the
brain. These nerves connect to the SAN. These do not initiate a
contraction, but they can affect the frequency of the
contractions. Action potenitals sent down the accelerator nerve
(sympathetic) increases the heart rate as in releases adrenaline.
Action potentials sent down the vagus nerve (parasympathetic)
reduces the heart rate as it releases acetyl choline.
The heart muscle responds to the presence of the hormone
adrenaline in the blood.…read more

Slide 6

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INTERACTION BETWEEN CONTROL
MECHANISMS
The various factors that affect heart rate
must interact in a coordinated way to ensure
that the heart beats at the most appropriate
rate.
Under resting conditions the heart rate is
controlled by the SAN. This has a set
frequency, varying from person to person, at
which it initiates waves of excitation. The
frequency of waves is typically 60-80 per
minute. However, the frequency of these
excitation waves can be controlled by the
cardiovascular centre in the medulla
oblongata.…read more

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