Download The Human Heart - SeniorScienceKGS

Body Systems:
The Human Heart
Your heart is an incredibly powerful organ.
It works constantly without ever pausing to
rest. It is made of cardiac muscle, which
only exists in the heart. Unlike other types
of muscle, cardiac muscle never gets tired.
The 4 chambered
Heart…
Your heart is divided into 4
hollow chambers. The upper
two chambers are called atria.
They are joined to two lower
chambers called ventricles.
These are the pumps of your
heart.
One-way valves between the
chambers keep blood flowing
through your heart in the right
direction. As blood flows
through a valve from one
chamber into another the valve
closes, preventing blood
flowing backwards. As the
valves snap shut, they make a
thumping, 'heart beat' noise.
The Heart: A Double pump
•
Blood carries oxygen and many other substances around your body. Oxygen
from your blood reacts with sugar in your cells to make energy. The waste
product of this process, carbon dioxide, is carried away from your cells in your
blood.
•
Your heart is a single organ, but it acts as a double pump. The first pump
carries oxygen-poor blood to your lungs, where it unloads carbon dioxide and
picks up oxygen. It then delivers oxygen-rich blood back to your heart. The
second pump delivers oxygen-rich blood to every part of your body. Blood
needing more oxygen is sent back to the heart to begin the cycle again. In one
day your heart transports all your blood around your body about 1000 times.
•
Your right ventricle pumps blood to your lungs and your left ventricle pumps
blood all around your body. The muscular walls of the left ventricle are thicker
than those of the right ventricle, making it a much more powerful pump. For this
reason, it is easiest to feel your heart beating on the left side of your chest.
•
Click on the link to find more information about the heart and a link to a flash
movie showing a heart beat:
http://www.fda.gov/hearthealth/healthyheart/healthyheart.html
Blood is pumped all around
the body…
The Pacemaker
•
Unlike skeletal muscle cells
that need to be stimulated by
nerve impulses to contract,
cardiac muscle cells can
contract all by themselves.
However, if left to their own
devices, cardiac muscle cells
in different areas of your heart
would beat at different rates.
Muscle cells in your ventricles
would beat more slowly than
those in your atria. Without
some kind of unifying function,
your heart would be an
inefficient, uncoordinated
pump. So, your heart has a tiny
group of cells known as the
sinoatrial node that is
responsible for coordinating
heart beat rate across your
heart. It starts each heartbeat
and sets the heartbeat pace for
the whole heart.
Heart rate
• Without nervous system
control, your heart would beat
around 100 times per minute.
However, when you are relaxed,
your parasympathetic nervous
system sets a resting heart beat
rate of about 70 beats per
minute, (resting heart rate is
usually between 72-80 beats per
minute in women and 64-72
beats per minute in men).
• When you exercise or feel anxious your
heart beats more quickly, increasing the
flow of oxygenated blood to your
muscles. This is triggered by your
sympathetic nervous system. Your heart
rate also increases in response to
hormones like adrenalin.
• On average, your maximum heart rate is
220 beats per minute minus your age.
So a 40 year old would have a maximum
heart rate of 180 beats per minute.
Oxygen supply to your heart
• Although your heart is continually filled
with blood, this blood doesn't provide
your heart with oxygen. The blood
supply that provides oxygen and
nutrients to your heart is provided by
blood vessels that wrap around the
outside of your heart.
As you grow older and depending on
Your diet, the arteries that supply your
Heart with blood may become
blocked, increasing your risk
of heart attack….
Today’s Task..
After reading through this presentation you should be able to complete
questions 1-5 on p126 of your text (reproduced below)
1 Name the major parts of the human circulatory system, and
explain their functions.
2 Why do we need a beating heart?
3 Calculate how many times your heart beats every day.
4 Why do some animals not need a transport system?
5 Find out about the transport system of another animal and
present it as a fully labelled diagram.
Web Links & Bibliography…..
• http://www.tmc.edu/thi/anatomy2.html
• http://www.fda.gov/hearthealth/healthyhear
t/healthyheart.html
• http://www.heartfoundation.com.au/index.c
fm?page=11
The End…