Download Circulatory System

Blood, Heart, and Vascular System
II. The Heart
Size, Shape, Location
of the Heart
• Size of a closed fist
• Shape
– Apex: Blunt rounded
point of cone
– Base: Flat part at
opposite of end of cone
• Located in thoracic
cavity in mediastinum
A. Structure – 4 chambered
double pump organ
1. Atria (2)– receiving chambers
2. Ventricles (2) – delivering chambers
a) Atrioventricular (AV) – found between the atrium and
ventricles
1. Tricuspid (on right)
2. Bicuspid or mitral (on left)
3. Chordae Tendinae (reinforce valves, attached in
ventricles)
b) Semilunar – found between the ventricles and the aorta
1. Aortic
2. Pulmonary
c) Prevent blood from flowing back
heartarteries arterioles


veinsvenules capillaries
The double pump
3. Heart Valves
3. Heart Valves
Function of the Heart Valves
4. Heart Wall Layers
a) The heart is surrounded by the
pericardial cavity. The lining of the
cavity, a serous membrane, is the
Pericardium
b) Epicardium: covers the outer surface of
heart
c) Myocardium: middle layer, muscular
wall of the heart, and responsibility for
heart contracting
d) Endocardium: smooth inner lining of
heart chambers
4. Heart Wall Layers
Continuous with
blood vessels
4. Heart Wall Layers
5. Coronary Vessels – blood vessels
that supply the myocardium
6. Conducting System of Heart –
specialized network of nerves supply the heart
Intrinsic Control of Heartbeat
• The SA (sinoatrial) node, or pacemaker,
initiates the heartbeat and causes the atria
to contract on average every 0.85 seconds.
• The AV (atrioventricular) node conveys the
stimulus and initiates contraction of the
ventricles.
• The signal for the ventricles to contract
travels from the AV node through the
atrioventricular bundle to the smaller
Purkinje fibers.
Extrinsic Control of Heartbeat
• A cardiac control center in the medulla
oblongata speeds up or slows down the
heart rate by way of the autonomic
nervous system branches: parasympathetic
system (slows heart rate) and the
sympathetic system (increases heart rate).
• Hormones epinephrine and norepinephrine
from the adrenal medulla also stimulate
faster heart rate.
Electrocardiogram - (ECG) can trace
conduction
of electrical signals through the heart
• Action potentials through
myocardium during
cardiac cycle produces
electric currents than can
be measured
• Pattern
– P wave
• Atria depolarization
– QRS complex
• Ventricle depolarization
• Atria repolarization
– T wave:
• Ventricle repolarization
Aberrant ECG patterns indicate
damage
B. Functions of the Heart
• Delivery of oxygenated blood to the body’s
tissues and deoxygenated blood to the
lungs
• Generating blood pressure
• Ensuring one-way blood flow
– Heart valves ensure one-way flow
• Regulating blood supply
– Changes in contraction rate and force match
blood delivery to changing metabolic needs
B. Functions of the Heart
1. Contraction (systole) of the ventricles
2. Relaxation (diastole) of the ventricles
3. Cardiac Cycle: The beginning of one
ventricular contraction to the next; a
heartbeat.
a) When the heart beats, the two atria contract
together, then the two ventricles contract;
then the whole heart relaxes.
Cardiac Cycle
Events during Cardiac Cycle
Blood Flow Through Heart
4. Heart Rate: Number of beats
per minute.
a) Average adult heart rate is 80-100 bpm
b) The infant/neonatal rate of heartbeat is
around 130-150 bpm, toddler’s is 100-130
bpm, older child is 90-110 bpm, adolescent
is 80-100 bpm.
c) Tachycardia: Heart rate in excess of 100
bpm
d) Bradycardia: Heart rate less than 60 bpm
5. Heart Sounds
a. Lup - Dub
i. First heart sound or “lub”
– Closure of the Atrioventricular valves and surrounding
fluid vibrations at beginning of ventricular systole
ii. Second heart sound or “dup”
– Results from closure of aortic and pulmonary
semilunar valves at beginning of ventricular diastole,
lasts longer
b. Abnormal heart sounds
– Caused by turbulent blood flow into ventricles and
detected near end of first one-third of diastole
– The result of faulty valves
Coordination of chamber contraction,
relaxation
Location of Heart Valves
Regulation of the Heart
• Intrinsic regulation: Results from normal
functional characteristics, not on neural or
hormonal regulation
• Extrinsic regulation: Involves neural and
hormonal control
– Parasympathetic stimulation
• Supplied by vagus nerve, decreases heart rate, acetylcholine
secreted
– Sympathetic stimulation
• Supplied by cardiac nerves, increases heart rate and force of
contraction, epinephrine and norepinephrine released
Heart Homeostasis
• Effect of blood pressure
– Baroreceptors monitor blood pressure
• Effect of pH, carbon dioxide, oxygen
– Chemoreceptors monitor levels
• Effect of extracellular ion concentration
– Increase or decrease in extracellular K+ decreases heart
rate
• Effect of body temperature
– Heart rate increases when body temperature
increases, heart rate decreases when body
temperature decreases
Effects of Aging on the Heart
• Gradual changes in heart function, minor
under resting condition, more significant
during exercise
• Hypertrophy of left ventricle
• Maximum heart rate decreases
• Increased tendency for valves to function
abnormally and arrhythmias to occur
• Increased oxygen consumption required to
pump same amount of blood
C. Pathologies
• Coronary Artery Disease – Arteriosclerosis or
atherosclerosis of the vessels (plaques) that
supply the myocardium (cannot deliver blood
adequately)
• Congestive Heart Failure – insufficiency of the
ventricles to effectively pump out blood into the
atria. Can result in cardiac arrest.
• Mitral Valve Prolapse – failure of the left
atrioventricular valve, allowing a backflow of
blood into the left atria, creating abnormal heart
sound or a murmur.
C. Pathologies
• Angina pectoris (pain) when body is not receiving
adequate oxygen
• Myocardial Infarction (heart attack) – a blockage
of blood in a coronary blood vessel, resulting in
death of a portion of the myocardium. This is
usually accompanied by chest pain or angina.
• Cardiac Arrest – cessation of all cardiac activity.
No heartbeat.
• Hypertension – high blood pressure; the arterial
pressure is too high; treated with exercise,
dietary changes, and medications.
– Risks: sedentary lifestyle, smoking, obesity, high Na+, high
cholesterol, stress, arteriosclerosis, genetic factors
D. Why is exercise good for the
heart?
• A trained heart is bigger
– pumps blood more efficiently (at a lower rate)
– stroke volume increases (due to stronger
contractions, allowing for lower rate)
• other benefits: higher aerobic capacity
(contributing to efficiency)
• Note that this takes training!
III. Vascular System
The blood, heart, and blood vessels together
make up the Cardiovascular system or
circulatory system.
A. Arteries and veins transport blood to
tissues and allows for exchange of
molecules through capillaries.
1. Arteries – carry blood from the heart to the tissues
a) Carry oxygenated blood (except the pulmonary
arteries carry deoxygenated blood to the lungs)
b) Arteries and arterioles take blood away from the heart.
c) The largest artery is the aorta.
d) The middle layer of an artery wall consists of smooth
muscle that can constrict to regulate blood flow and
blood pressure. (thick muscular walls)
e) Arterioles can constrict or dilate, changing blood
pressure.
f) Aorta to artery to arteriole to capillary
2. Veins – carry blood from the tissues toward the
heart
a) Carry deoxygenated blood (except the pulmonary
veins carry oxygenated blood to the heart)
b) Venules drain blood from capillaries, then join to form
veins that take blood to the heart.
c) Veins have much less smooth muscle and connective
tissue than arteries. (thinner, less muscular walls)
d) Veins often have valves that prevent the backward
flow of blood when closed.
e) Veins carry about 70% of the body’s blood and act as a
reservoir during hemorrhage.
Blood vessels
3. Capillaries – permeable network of vessels
that allow the exchange of materials.
a) Capillaries have walls only one cell thick (one
endothelial layer) to allow exchange of gases and
nutrients with tissue fluid.
b) Capillary beds are present in all regions of the body
but not all capillary beds are open at the same time.
c) Contraction of a sphincter muscle closes off a bed and
blood can flow through an arteriovenous shunt that
bypasses the capillary bed.
Anatomy of a capillary bed
How does this system work?
lungs
pulmonary vein
pulmonary artery
head & arms
aorta
main vein
Right
Left
liver
digestive system
kidneys
legs
Circulatory System
Our circulatory system is a double circulatory system.
This means it has two parts parts.
Lungs
the right side of the
the left side of the
system
system
deals with
deals with
deoxygenated blood.
oxygenated blood.
Body cells
B. Vasodilatation – increase in diameter of a
blood vessel
1) Decreases temperature
C. Vasoconstriction – decrease in diameter of a
blood vessel
1) Increases temperature
D. Blood pressure – the amount of pressure the
blood exerts on the vessel wall
1) Systolic – highest number reading; ventricular
contraction
2) Diastolic – lowest number reading; ventricular
relaxation
Pathologies
• Arteriosclerosis - hardening of the arteries.
• Atherosclerosis - due to a build-up of fatty
material (plaque) along the walls of arteries.
– This fatty material thickens, hardens (forms calcium
deposits), and may eventually block the arteries.
– Slows down or stops blood flow; leads to chest pain
(angina) or heart attack.
– Atherosclerosis is a type of arteriosclerosis. The two
terms are often used to mean the same thing.
Pathologies
• Hypertension
– About 20% of Americans suffer from hypertension (high blood
pressure).
– Hypertension is present when systolic pressure is 140 or greater
or diastolic pressure is 100 or greater; diastolic pressure is
emphasized when medical treatment is considered.
– A genetic predisposition for hypertension occurs in those who
have a gene that codes for angiotensinogen, a powerful
vasoconstrictor.
• Aneurysm - a ballooning of a blood vessel, usually
in the abdominal aorta or arteries leading to the
brain.
Pathologies
• Varicose Veins - develop when the valves of veins
become weak
• Hemorrhoids (piles) - due to varicose veins in the
rectum
• Phlebitis/thombophlebitis - inflammation of a vein
and can lead to a blood clot and possible death if
the clot is dislodged and is carried to a pulmonary
vessel.
Pathologies
• DVT: Deep Vein Thrombosis - a blood clot forms in a
vein that is in the lower leg and thigh.
– The clot can block blood flow and cause swelling and pain. Can
have an embolism, break off and move through the body. An
embolism can get stuck in the brain, lungs, heart, or other area,
leading to severe damage.
• Reynaud's Syndrome - a condition that causes some
areas of your body (fingers, toes, tip of your nose and
ears) to feel numb and cool in response to cold
temperatures or stress.
– Smaller arteries that supply blood to your skin narrow, limiting
blood circulation to affected areas.
– More likely in women and in those people who live in colder
climates.