Download Cardiovascular Systems - Seattle Central College

Cardiovascular Systems
Distributing gases (O2 & CO2),
Food nutrients,
Hormones,
Immune cells
Overview
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Types of vascular systems
Distribution of types among Animals
Structures of closed vs. open systems
Structure & function of hearts and vascular
tissues
– Innervation
– Nutrient delivery
– Tissue types
Gastrovascular Cavities
• No specialized exchange area
• No distribution system
– Diffusion is adequate
• Why?
• Td ∝ d2
Circulatory Systems
• Blood, pumps (hearts) with chambers & valves, vessels
• Closed: High BP, blood separate from interstitial fluid
• Open: Low BP, blood & interstitial fluid are same
Arthropods
Molluscs
Annelids
Cephalopods
Vertebrates
Single circulation
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Fishes, sharks
Atria collects
Ventricle pumps
Valves prevent backflow
Exchange @ gill capillaries
& body tissues
Double Circulation systems
• Amphibians allow mixing. Why is this OK?
• Lepidosaurs & Testudinates allow minimal mixing
• Mammals & Archosaurs allow none! Why not?
Archosaurs
Mammalian Circulatory System
• Four chambered heart
with pacemakers
• Thick arteries (away!)
• Thin veins (towards!)
• Capillary beds at lungs,
head, forelimbs,
abdomen, hindlimbs
Anatomy
• Pacemakers: autorhythmic cells in R atrium
• Chambers
– Atria: Right & Left; blood collector
– Ventricles: Right & Left; blood pump
• Vessels: Transport
– Arteries: Pulmonary (lungs), Aorta (body)
– Veins: Vena cava, pulmonary
• Valves: Prevent backflow
– Atrioventricular (AV): tri- & bicuspid
– Semilunar: Pulmonary & aortic
Anatomy & Blood Flow
Valves prevent backflow
• Pressure changes
produce flow
• Backflow is stifled by
semi-lunar valve collapse
• During systole, where is
blood pressure highest?:
– Atria
– ventricles
– arteries
Cardiac cycle produces heart sounds
• Cause = forceful closure of valves by high
pressure blood
• 1st heart sound: lubb
– Beginning of systole; results from closure of AV valve
• 2nd heart sound: dupp
– Beginning of diastole; results from closure of
semilunar valves
Cardiac cycle
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Aorta
Left Ventricle
Left Atria
What is
happening when
the traces cross?
How does coordinated contraction
occur?
• Nodes: pacemakers
– Innervated by neurons
of MO
• Purkinje fibers: signal
propagators
• Intercallated discs of
cardiac muscle
Pacemakers
• Sinoatrial (SA)
– Depolarize atria;
coordinated contraction
follows
• Atrioventricular (AV)
– Depolarize ventricles;
purkinje fibers propagate
AP; coordinated
contraction of ventricles
How is tetanus prevented?
The Plateau phase deafens myocardia
AP differences
• Plateau phase: “long”, slow repolarization
phase allows complete relaxation of
myocardium
– Caused by opening of Ca2+ channels in plasma
membrane
• What does Ca2+ do when those channels open?
• Prevents tetanus
– Safety mechanism
• Without it, what would happen if AP’s arrived too
frequently?
Blood pressure and Velocity
• C.S. Area & Distance from
heart
• As area increases, velocity &
pressure decrease; as area
decreases again, velocity
increases
• As distance increases, pressure
decreases
Structure reveals function
• Arteries
– Thick muscle & elastin
to constrict arteries &
allow stretch & recoil
– Thick, elastic CT to
allow stretch & recoil
and withstand pressure
• Veins
– Large diameter,
thinner-walled, less
elastic
Structure reveals function
Artery layers
Structure reveals function
• Capillaries
– Small diameter
– Single endothelial cell
layer is smooth, flat &
permeable
– Allows smooth flow, rapid
exchange
Mechanism of venous return
• If pressure is low in veins,
how does blood return to
the heart? What is the
driving force?
• Skeletal muscles
• Valves
Capillary bed function
• Blood flow controlled by
sphincter muscles (smooth)
that bind hormones
– NO causes dilation
– Endothelin causes constriction
• Regulates:
– Heat exchange
– Gas exchange (O2 & CO2)
– Nutrient delivery & waste
removal (glucose & lactate)
Multiple effects
• Hormones can have multiple, often antagonistic effects
– bind to different receptors
– Different signal transduction pathways
Mechanisms of Capillary Exchange
1. Diffusion – Concentration gradient
– Avenues of exchange: between endothelial cells,
protein channels, cell membranes, major sinuses
– What factors affect diffusion rates?: short _______,
steep _______, small _______.
2. Filtration – Hydrostatic pressure
– Water and small solutes forced across capillary
wall, leaving large solutes & proteins in blood
Fluid exchange in capillaries
• Blood pressure forces
fluid, small solutes &
gases out of capillaries
• Osmotic pressure (large
solutes) draw fluid back
into capillaries