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…Interesting Facts
Circulation
Biology 11
A. Allen
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 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.
• A heart beats about 100,000 times a day and 35 million times a
year.
• Every minute, the heart pumps our entire supply of blood -about five litres -- through the body.
• In one day, the heart pumps nearly 7200 litres of blood. In a 70year 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.
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- Closed Systems
• only closed transport systems true circulatory systems.
Blood is confined to 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 of locomotion 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.
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Earthworm’s Five “Hearts”
The Human
Circulatory
System
Components of Blood
Components of The Human Circulatory System
• Blood cells come stem cells in bone
marrow.
• Heart, blood vessels, blood
...Components of The Human Circulatory System
...Components of The Human Circulatory System
Blood
functions include;
• transport of life sustaining nutrients, O2 hormones
• transport of wastes such as CO2 and urea.
• protection from disease.
• Clotting.
• maintaining constant body temperature.
• helps with regulation of fluid levels in body.
• general movement of blood through blood vessels:
• heart arteries arterioles capillaries venules veins heart
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!
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…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.
Valves in veins prevent backflow...
Look at
the veins
on this
guy!
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
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Blood Vessels of a Fetal Pig
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)
Label your diagram!
Components of The Human Circulatory System
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1a
• The Heart
– two atria (right and left) (singular = atrium)
– two ventricles (right and left)
– Has valves to prevent backflow
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2a
7
8b
8a
9a
9b
10
10
3
11
12
4
13
5
14
2b
16
6
1b
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.
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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
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Heart Valve Pics
...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
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).
Regulation of Heart Rate Autonomic
Nervous System (ANS)
…Conduction System of the Heart
•
• 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.
•
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
• Electrical Impulse in Heart:
visit:
Stimulated by brain in times of
stress. It makes heart beat
faster. Blood flow increases.
www.wolfminimaze.com/tab02.htm
•
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.
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What is Blood Pressure?
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
• 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 is measured by a device called a
sphygmomanometer.
• 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”)
QRS-wave
Ventricular contraction
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 bp.
…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:
• vasodialation:
• blood volume:
• cardiac output
smooth muscle around the blood vessels relaxes.
the blood vessel opens up …bp ↑.
blood volume ↓…blood pressure ↓
Heart Rate and Stoke Volume ↓… blood pressure
↓
…Regulation of 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.
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