Download The Mammalian Heart

Unit 5
SBI3U
9.3 The Mammalian Heart
AMAZING Human Heart Facts:
 Pumps about 70x per minute, 90 000x per day through 160 000 km of blood vessels!
 Pumps in 2 directions at once without ever mixing the blood!
 Has a life expectancy of around 80 years
 Is about the size of your fist
The Flow of Blood
Watch the narrated animation and fill in the answers to discover how blood moves through the heart.
http://www.medtropolis.com/VBody.asp
Blood first enters the ______________________ through two large veins called the ____________ vena cava
and the _____________ vena cava. The blood entering the right atrium is low in _______________ since it is
returning to the heart after nourishing various body parts with oxygen. The blood then moves from the right
atrium into the _________________________ through a valve called the ___________________ valve. The
valve prevents blood from flowing from the right ventricle back to the right atrium, ensuring a one way
flow. When the blood is in the right ventricle, the heart muscle pumps it the short distance to the lungs.
Blood goes through the __________________________________ to the lungs, getting rid of its carbon dioxide
and acquiring new oxygen, and then returns to the heart. The blood returns to the heart through the
_______________________ leading to the left atrium. When the left atrial wall contracts, the blood is
pushed through the _________________ valve into the left ventricle. The left ventricle contracts and forces
the oxygen-rich blood on its life giving journey throughout the body. The blood goes through the ________,
a large artery with branches that distribute blood to all parts of the body.
Heart Diagram
http://www.smm.org/heart/heart/in-out.htm  LABELS
http://www.smm.org/heart/lessons/lesson6.htm  FUNCTIONS
Part
Function
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2
3.
4.
5.
6.
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8.
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10.
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15.
Trace the passage of OXYGENATED
blood with a red arrow.
Trace the passage of
DEOXYGENATED blood with a blue
arrow.
Control of the Heartbeat
 a bundle of specialized muscle tissue in the wall of the
right atrium stimulates the muscle fibres to contract and
relax rhythmically
 Tissue is called the _______________________________
(S-A node or pacemaker - #1 on diagram)
Recording the Heart Rate
 The S-A node generates an electrical impulse that spreads
over the 2 atria and makes them contract
 The impulse then reaches the ________________________
node (A-V node - #2 on diagram) which causes the
ventricles to contract
The Electrocardiogram
 Change in _______________ produced by electrical
charges can be measured using a device called an _________________________
Electrocardiograph
P wave – small voltage increase that shows the electrical
depolarization that accompanies the contraction of the
atria
QRS complex – shows the depolarization that
accompanies the contraction of the ventricles
T wave – represents the repolarization that precedes the
next firing of the S-A node
Chemical Regulators
1. Noradrenaline
 chemical that makes the S-A node fire ________________________________
 released when there’s an increase in ________________________________ (running to the bus!) or
when you are nervous, angry, excited or in pain
2. Acetylcholine
 chemical that ________________________________of the S-A node
Blood Pressure
 Heart rate and blood pressure will increase in response to an increased demand in oxygen
 Highest pressure in cardiac cycle is generated by contraction of the left ventricle as if forces blood
out of the heart (________________________________)
 Lowest pressure in cardiac cycle is immediately before another contraction of the ventricles
(________________________________)
 Typically measured at an artery in an arm and recorded in mm of Hg
 Written as systolic over diastolic
 Average healthy blood pressure = ________________________________
Blood Pressure Risks
 Elevated blood pressure = __________________
 Conditions that increase the blood ____________________ or reduce the ___________________ of
the arteries can produce hypertension
Ex. __________ = causes blood to retain water therefore increasing the volume of blood the heart
needs to pump
Ex. ___________________ = clogs arteries, reducing their elasticity