Transcript Introduction to Circulation BY DR QAZI IMTIAZ RASOOL

Lecture 37
Introduction to Circulation
BY DR QAZI IMTIAZ RASOOL
OBJECTIVES
1. Identify the two divisions of circulation and track the pathway of the blood through
both circulations.
2. Outline the various parts of circulation and identify the differences in structure,
function, pressure and velocity of blood in different vessels.
3. Describe the physiological anatomy of the heart and identify its various specialized
functional parts.
Functions of the Heart
1.
Generating blood pressure
2.
Routing blood: separates pulmonary and systemic circulations
3.
Ensuring one-way blood flow: valves
4.
Regulating blood supply
1.Changes in contraction rate and force match blood delivery to changing
metabolic needs
Circulatory System Function
Move circulatory fluid (blood) around body
1. Gas Transport
2. Nutrient Transport
3. Excretory Product Transport
4. Cell Signal Transport
5. Distribute secretions of endocrine glands,
6. Production/Synthesis
7. Hydraulic Force
8. Heat Conductance
9. Immunity
Overview of the Cardiovascular System
1. Heart- circulates blood through vessels
2. Vascular System /Blood vessels
3.
4.
5.
Arteries- away from heart
Veins- towards heart
Capillaries- location of internal respiration, are tiny, thin-walled blood vessels that
connect arteries to veins and are located in all body tissues.
- in diameter that blood cells pass through in a single file.
3.
Blood- transport medium
Path of Blood
Pulmonary Circuit
Blood flow between the
lungs and heart
Systemic Circuit
Blood flow between the
rest of the body and heart
Supplied by the Right side
of the heart
Supplied by the Left side
of the heart
Pulmonary
circulation
Systemic circulation
/greater circulation /
peripheral circulation.
Venous return
is aided by both structural modifications and functional
adaptations.
1. Structural
-Large lumen
-Valves - present mostly in extremities,
none in ventral body cavity
2. Functional
-Respiratory Pump
-Muscular Pump
-Smooth muscle layer under sympathetic control
Physiological- anatomy
Structure of Blood Vessel Walls
except the smallest consist of three
layers:
1.Tunica intima reduces friction
between the vessel walls and blood;
2. Tunica media controls
vasoconstriction and vasodilation of
the vessel;
3. Tunica externa protects, reinforces,
and anchors the vessel to surrounding
structures
1.Blood flow is the volume of blood flowing
through a vessel,
organ,
or the entire circulation ml/min
(controlled in relation to the tissue need)
2. Blood pressure is the force per unit area
exerted by the blood against a vessel wall (mm
Hg).
(by the tension at the end of the arterioles)
3. Resistance is friction between blood and the
vessel wall,.
Systemic Blood Pressure
Functional Anatomy of the Heart
Chambers
1.
4 chambers
1. 2 Atria
2. 2 Ventricles
2. 2 systems
1. Pulmonary
2. Systemic
Functional Anatomy of the Heart
Cardiac Muscle
1.
Characteristics
1. Striated
2. Short branched cells
3. Uninucleate
4. Intercalated discs
5. T-tubules larger and
over z-discs
Functional Anatomy of the Heart
Valves
1.
Function is to prevent backflow
1. Atrioventricular Valves
1. Prevent backflow to the atria
2. Prolapse is prevented by the chordae tendinae
1. Tensioned by the papillary muscles
2. Semilunar Valves
1. Prevent backflow into ventricles
The Conduction System of the Heart
1.
2.
Conduction pathways
Depolarization spreads
throughout the heart very rapidly
facilitating a coordinated
contraction pattern
3. Intercalated disks
1. Form junctions between
adjacent cardiac muscle fibers
2. Contain a high concentration
of gap junctions for rapid
transmission of the action
potential
Myocardial Physiology
Contractile Cells
1.
2.
Plateau phase prevents summation due to the elongated refractory period
No summation capacity = no tetanus (Which would be fatal)
Myocardial Physiology
Autorhythmic Cells (Pacemaker Cells)
1.
Altering Activity of Pacemaker Cells
1.
Sympathetic activity
1.
NE and E increase If channel activity
1.
2.
Binds to β1 adrenergic receptors which activate cAMP and increase If channel open
time
Causes more rapid pacemaker potential and faster rate of action potentials
Sympathetic Activity Summary:
increased chronotropic effects
heart rate
increased dromotropic effects
conduction of APs
increased inotropic effects
contractility
Myocardial Physiology
Autorhythmic Cells (Pacemaker Cells)
1.
Altering Activity of Pacemaker Cells
1.
Parasympathetic activity
1.
ACh binds to muscarinic receptors
1.
Increases K+ permeability and decreases Ca2+ permeability = hyperpolarizing the
membrane
1. Longer time to threshold = slower rate of action potentials
Parasympathetic Activity
Summary:
decreased chronotropic effects
heart rate
decreased dromotropic effects
 conduction of APs
decreased inotropic effects
 contractility
Aging and the CVS
Changes occur in the blood, heart, and BVs
1. Blood changes – HCT; thrombi and emboli form more easily;
blood pools in leg
2. Heart changes – efficiency and elasticity; atherosclerosis of
coronary vessels; scar tissue forms
3. Blood vessel changes – loss of elasticity; calcium deposits damage
vessel walls
4. Gradual changes in heart function, minor under resting condition,
more significant during exercise
5. Hypertrophy of L ventricle
6. Maximum heart rate decreases
7. tendency for valves to function abnormally and arrhythmias to
occur
8. O2 consumption required to pump same amount of blood