Circulation
Biology 11
S. MacInnes
…Interesting Facts
• A heart beats about 100,000 times a day and 35 million times a year.
• In one day, the heart pumps nearly 7200 litres of blood. In a 70-year
lifetime, it pumps about 185 million gallons.
• An aorta is almost the diameter of a garden hose, but it takes ten
capillaries to equal the diameter of a strand of human hair.
• There are 100,000 km of blood vessels in each human!
• In ancient times, the heart was given special importance. The
Chinese considered that happiness originated in the heart, and the
Egyptians considered the heart to be the source of intelligence and
emotion.
• Heart cells can beat on their own without intervention from the brain.
• No cell in your body is further away than 2 cells from a blood vessel
• You have 96,000 km of blood vessels to sustain your 100 trillion cells
• Your heart is no larger than the size of your fist with a mass of about
300 g
• Your heart beats about 70 times a min from the day you are born until
you die…
• If you could stretch out all your blood vessels there is enough to go
around the world twice.
THINK!
• Small unicellular organisms do not need a
circulatory system. Why do larger
organisms need one?
• HINT: Think surface : volume ratio.
The Importance of Circulation
• Unicellular organisms do not need any
specialized system to transport nutrients,
wastes and gases.
• The cells of unicellular and simple
multicellular organisms are never far away
from the organism’s surroundings (from where
nutrients, gases, etc. come from)
• The cells of larger organisms are too far away
for such substances to diffuse to/from all cells.
Therefore, a specialized transport system is
required.
Transport in Animals:
Open vs. Closed Systems
• Most animals have evolved specialized systems to
transport gases, nutrients and metabolic wastes.
These systems in animals have two essential parts:
1.
circulatory fluid (blood)
2.
a pump (heart or other muscular structure)
• Some animals have blood vessels (optional)
– if vessels are present…  closed transport system.
– if absent …………
 an open transport system
Transport in Animals- Open Systems
• Open System
Ex: grasshopper
• not true circulatory systems
• from the action of muscular movements, the blood circulates into open
spaces and surrounding organs. Blood bathes cells directly in order for
transport of nutrients etc.
• openings in the heart allow blood to enter.
• the blood carries mainly food nutrients and metabolic wastes.
• not very efficient: movement of blood is slow and under low pressure.
• in insects, the blood does not carry oxygen. There is a separate tubular
system for this.
• wing movement (muscles) of flying insects speeds up blood flow.
Transport in Animals- Closed Systems
• only closed transport systems  true circulatory systems.
Blood is contained within blood vessels.
• closed systems can be simple or complex.
• efficient.
• ex. An earthworm’s transport system represents the most
basic of true circulatory systems
• muscle movement from locomotion (movement) helps to keep
blood flowing.
• earthworms have five pairs of pumps, “aortic arches” (simple
hearts)
• flow of blood in earthworm:
• pump contracts  blood pumped into a ventral (‘belly’ side)
blood vessel  blood flows into dorsal (‘back’ side) blood
vessel  blood returns to heart
• blood can only move in one direction.
Closed system
Open system
Earthworm’s Five “Hearts”
The Human
Circulatory
System
Purpose of the Circulatory system:
• Transport!
– To bring oxygen and nutrients to the cells
– To take away wastes (For ex: CO2) from the cells
– To facilitate the immune system
Components of The Human Circulatory System
• Heart, blood vessels, blood
...Components of The Human Circulatory System
Blood Vessels
arteries
–
–
–
–
take blood from heart.
not always rich in O2.
size: 25 mm (aorta) to 0.5 mm.
branch into smaller arteries called
arterioles (< 0.5 mm). arterioles
contain ‘smooth’ muscle that
regulates blood pressure.
– ‘elastic’ in nature. they stretch and
‘bulge’ when heart pumps blood
through  feel your pulse!
…Blood Vessels
veins
– take blood to heart
– not always low in O2
– branch into smaller veins called
venules
– the lumens (openings) are larger
than that of arteries but walls
are thinner.
– depend on contraction of
surrounding muscle to move
blood.
– contain valves  prevent
backflow of blood.
Look at
the veins
on this
guy!
Valves in veins prevent backflow...
When the valves of the veins are
leaky… varicose veins!
…Blood Vessels
Capillaries
– tiny blood vessels. about 0.008 mm in
diameter. just wide enough for one red
blood cell to pass through.
– one cell thick; makes exchange of
materials between blood and body cells
easy.
– connect arterioles and venuoles
– the total length of all the capillaries in
your body is 1000’s of kilometres. total
surface area is nearly 6000 m2. why?
– penetrate almost every tissue in the body.
Comparison of Blood Vessels
Blood Vessels of a Fetal Pig
Components of The Human Circulatory System
• The Heart
– two atria (right and left) (singular = atrium)
– two ventricles (right and left)
– Has valves to prevent backflow
Label your diagram!
17
1a
15
2a
7
8b
8a
9a
9b
3
10
11
12
4
13
5
14
10
2b
1b
16
6
20
• very cool heart videos
Circulatory Routes of the Human
Cardiovascular System
• The CV system is a closed, one-way system (blood only flows in one
direction)
• Blood flows in two distinct circuits
• pulmonary circuit
• path of blood:
• right side the heart  lungs (blood picks up O2 and gets rid of CO2)
 left side of heart.
• systemic circuit
• path of blood:
• left side of the heart  tissues in the body to deliver O2, nutrients, get
pick up wastes  right side of heart.
Valves of the Heart
TWO kinds: Atrio-ventricular and Semilunar…
Atrio-Ventricular (AV) Valves
• each is located between an atrium and a ventricle
• when the ventricles contract, these valves prevent blood from flowing
from the ventricles back into the atria
tricuspid valve
– has three ‘cusps’ or flaps that open and close.
– between right atria and right ventricle
bicuspid (mitral) valve
– has two ‘cusps’ or flaps that
open and close.
– (AKA mitral valve)
– between left atria and left
ventricle
...Valves of the Heart
Semilunar Valves
• located in the two major arteries as they leave the heart
• prevent blood flow back into the ventricles
• each have a crescent or half-moon shape
pulmonary valve
– leads to the pulmonary artery
– between right ventricle and pulmonary artery
aortic valve
– leads to the aorta
– between left ventricle and aorta
• Cool fact: Ever listen to your heart beat? It makes a “lub-dub”
sound. As your ventricles contract, your AV valves close
preventing backflow into atria  “lub”. When your ventricles
relax, the semilunar valves close preventing backflow  “dub”
• animation: valves in action
Heart Valve Pics
CV Word Scramble
•
Several structures of the circulatory system are listed below. Unscramble the terms to
describe the flow of blood through the body. Start with "blood from the body". Present
your answer as a flow chart-style graphic organizer.
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Blood from the body
bicuspid valve
Superior vena cava
carbon dioxide
right ventricle
Inferior vena cava
pulmonary valve
Left ventricle
oxygen
body
Left atrium
Pulmonary artery
Tricuspid valve
Pulmonary veins
lungs
Aortic valve
carbon dioxide
Aorta
Right atrium
oxygen
CV Word Scramble Answers!
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Blood from the body
Superior vena cava & Inferior vena cava
Right atrium
Tricuspid valve
right ventricle
pulmonary valve
Pulmonary artery
lungs
Dump carbon dioxide
Pick up oxygen
Pulmonary veins
Left atrium
Bicuspid valve
Left ventricle
Aortic valve
Aorta
body
Pick up carbon dioxide
Dump oxygen
Locating Heart
Sounds with a
Stethoscope
Conduction System of the Heart
• cardiac muscle can contract without
external nerve stimulation (i.e.
messages from the brain). The heart
can continue to beat for a short time
once removed from the body
• the heart’s tempo is set by the
sinoatrial node (SA node); a bundle
of specialized nerves. It is often
referred to as the pacemaker. Its
tempo is set to about 70 bpm (beats
per minute).
• the autonomic (automatic)
nervous system regulates heart
rate but does not initiate
contraction (the SA node
does). It speeds up/slows down
the SA node as needed.
…Conduction System of the Heart
•
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Electrical Impulse in Heart:
SA node initiates cardiac cycle. It sends out
an electrical impulse.
•
electrical impulse spreads over both atria
causing them to contract
•
At the same time, it sends an impulse to the
AV node
•
impulse is slowly spread through AV node and
then to the Bundle of His (atrioventricular
bundle)
impulse spreads through both sides of the
septum
impulse goes to Purkinje Fibres which
stimulate contraction of ventricles!
ECG (Electrocardiogram)
• An ECG can be used to measure the electrical fields
produced within the heart. Doctors can analyze such a
ECG to diagnose heart problems.
P-wave
T-wave
Atrial
contraction
Ventricles
recover
QRS-wave
Ventricular contraction
Regulation of Heart Rate Autonomic
Nervous System (ANS)
• Although the heart can beat without nervous intervention, heart rate
must be regulated by the nervous system as conditions change
• The ANS is comprised of the sympathetic nervous system and the
parasympathetic nervous system
ANS
Sympathetic
nervous system
Stimulated by brain in times of
stress. It makes heart beat
faster. Blood flow increases.
•
Parasympathetic
nervous system
Stimulated by brain in times of
relaxation. It makes heart beat
slower. Blood flow decreases.
Tachycardia When Heart Rate > 100 bpm. This can be caused by exercise
or drugs such as caffeine or nicotine.
Regulation of Blood Flow
• The Autonomic nervous system (ANS) maintains
homeostasis automatically.
• Precapillary sphincter muscles encircle arterioles before
capillary beds. The ANS can regulate blood flow to tissues by
sending a nerve impulse to these muscles causing them to
contract or relax.
• Contraction of precapillary sphincter muscles 
vasoconstriction (less blood flow)
• relaxation of precapillary sphincter muscles  vasodialation
(more blood flow)
What is Blood Pressure?
• Blood pressure is the measure of force against the
blood vessel walls.
• measured in the brachial artery (in upper arm). It is
measured in the units “mm Hg” (millimetres of
mercury).
• Blood pressure has two readings; systole and
diastole.
• systole: blood pressure when the ventricles are contracting.
• diastole: blood pressure when the ventricles are relaxed.
• blood pressure varies with age, health, exercise. A typical resting
bp is 120/80 (read as “120 over 80”)
What is this called?
Sphygmomanometer
Regulation of Blood Pressure
• It is important to regulate blood pressure.
Low blood pressure reduces blood flow.
High blood pressure weakens arteries which
may rupture. Consistently high blood
pressure is called hypertension.
• bp is regulated by renal system (kidneys),
nervous system, and by hormones. Together,
physiological changes are made to raise or
lower blood pressure.
• Special sensors called baroreceptors detect
pressure change in the aorta and carotid
artery (in neck). The baroreceptors send
messages to medulla oblongata to
increase/decrease.
regulation of blood pressure
…Regulation of Blood Pressure
…Regulation of Blood Pressure
• If blood pressure is LOW:
• vasoconstriction:
smooth muscle around the blood vessels contracts,
narrowing the lumen of the vessels ...bp 
• blood volume:
blood volume …blood pressure 
• cardiac output
Heart Rate (beats/min) and Stroke Volume (mL per beat)
increase… blood pressure 
• If blood pressure is HIGH:
• vasodilation: smooth muscle around the blood vessels relaxes.
the blood vessel opens up …bp .
• blood volume:
blood volume …blood pressure 
• cardiac output
Heart Rate and Stoke Volume … blood pressure

measuring blood pressure
…Regulation of Blood Pressure
Cool facts:
•
Some people think a alcoholic drink will
warm you up on a cold day. It actually cools
you down! Alcohol causes vasodilation of
blood vessels in skin. this  blood flow to
skin…heat is lost!
• Alcohol makes some people congested!
Blood vessels in nose dilate  nasal
passages close off.