Download Human Physiology

Topic 6.2 + Option H5
Transport System
IB Biology
Components of Transport System
 Blood
 Heart
 Blood Vessels
Types of Circulation

1) Pulmonary
 heart – lungs – heart

2) Systemic
 heart – body – heart
Types of Circulation

3) Coronary
 blood vessels that supply
heart muscle with oxygen
and nutrients / remove
waste products
Heart Structure

2 sides with different functions:
 right: to receive + pump blood to the lungs
 left: to receive + pump blood to the body


2 types of chambers: atrium + ventricle
4 chambers: 2 atria/2 ventricles


Cardiac muscle: involuntary
Ultimate control:
 Autonomic Nervous System (ANS)
Heart Valves
 Allow blood to flow in only one direction
 Four valves
 Atrioventricular valves – between atria and
ventricles
 Bicuspid valve (left)
 Tricuspid valve (right)
 Semilunar valves between ventricle and
artery
 Pulmonary semilunar valve
 Aortic semilunar valve
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 Aorta
Vessels of the heart
 Leaves left ventricle
 Pulmonary arteries
 Leave right ventricle
 Vena cava
 Enters right atrium
 Pulmonary veins (four)
 Enter left atrium
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 Blood in the heart chambers does not
nourish the myocardium
 The heart has its own nourishing
circulatory system
 Coronary arteries
 Cardiac veins
 Blood empties into the right atrium via
the coronary sinus
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Heart contractions
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The Heart: Cardiac Cycle
 Atria contract simultaneously
 Atria relax, then ventricles contract
 Systole = contraction
 Diastole = relaxation
Cardiac cycle – events of one
complete heart beat
Mid-to-late diastole – blood flows into ventricles
Ventricular systole – blood pressure builds
before ventricle contracts, pushing out blood
Early diastole – atria finish re-filling, ventricular
pressure is low
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Blood

Plasma – fluid
Red blood cells or erythrocytes – produced in the bone marrow of large
bones / transport O2 and CO2

White blood cells (lymphocytes and phagocytes) – produced in the bone
marrow / belong to immune system


Platelets - cell fragments that help blood clotting
(antibodies)
+ HEAT
urea
Blood Vessels

Arteries
 carry blood Away from heart;
strong thick walls; smooth muscle
(elastic); fibrous coat; small lumen
= ↑ pressure

Veins
 carry blood back to heart; large
lumen; thin wall/muscle; ↓ elastic;
valves

Capillaries
 connect arteries and veins; no
valves; pores; no muscle/not elastic
extremely thin (1 cell thick) = fast
exchange
Blood Pressure

Blood applies pressure to the walls

If it is too low - cells might not get enough O2

If it is too high - vessels can rupture (heart attack, stroke)
 Salt can increase blood pressure

Normal blood pressure: 120/80 mm Hg
Coronary Heart Disease
Slow build up of plaque (lipids, cholesterol)
= ATHEROSCLEROSIS
 Arteries become harder, less flexible
 Less space for blood
 Coronary arteries supply O2 to heart cells
 Thrombosis = clot = heart attack = heart
cells die

Factors affecting coronary heart disease
(CHD):

 Age, race, heredity, gender, cholesterol levels, blood
pressure, obesity, diabetes, smoking, sedentary lifestyle,
stress
Heartbeat Control
Myogenic muscle contraction:
Sino-Atrial Node (SA) – specialized cells
generate electrical impulse on their own with
regular frequency (PACEMAKER)
- Impulse spreads to both atria → atria
contract together
- Atrio-Ventricular node (AV) picks up the
impulse in lower right atrium septum and
conduces to the ventricles through fibers

-
Ventricles contract: AV valves close / semilunar valves open (SYSTOLE)
- Contraction stops – ventricles relax
(DIASTOLE)
-
Heartbeat Control
Autonomic Nervous System
and hormones can modify
myogenic rhythm:

Nerves from brain stem
(medulla) have involuntary
control over heart rate = affect SA
node
 Exercise = ↑CO2 / ↓O2 = medulla
oblongata (brainstem) takes over
 Chemoreceptors detect ↑CO2 =
H+ causes decrease in pH
o
Adrenaline targets sino-atrial
node (SAN): stimulant
o
Cardiac Cycle

One whole heartbeat
 Systole = contraction / Diastole = relaxation
 Valves prevent backflow

Sound = valves closing
 1st = atrio-ventricular valves (mitral, tricuspid)
 2nd = semilunar valves (aortic, pulmonary)
Important = valves open and close depending on pressure
inside chambers/blood vessels
 Atria systole = pressure not too great (thin walls, most blood
already moved to ventricles)
 Ventricular systole = pressure great inside both ventricles
