Purpose of Circulatory System

• Transport Nutrients
• Respiratory Gases
• Hormones
• Metabolic Products

...throughout the body.

• Temperature Control

Structural Elements of Circulatory Systems

• Pump (heart)
• Conduits (vessels)
• Transport Medium (blood)

OPEN VS CLOSED ORGANIZATION

Vertebrate Cirulatory Systems

• Deoxygenate blood flows to "gas exchange organ":

1. Gills
2. Lungs

• Systematic:Oxygenated blood flows to the rest of the body
• Increased # of chambers = Increased separation of blood flow to to either "gas exchange organs" or "rest of body"

Human Heart

The human Heart ( 2 pumps in one):

4 Chambers:

• 2 Atria (in)
• 2 Ventricles (out)
• Blood ENTERS atrium, Exits through ventricle
• Right Heart > Lungs (or gills)
• Left Heart > Systematic
• One-way valves: prevent backflow

The Cardiac Cycle

(2 phases)

The cardiac cycle has 2 phases:

1. Systole = ventricles contract
2. Diastole = ventricles relax

Heart sounds (beating) are made by the heart valves opening and closing.

Measuring Blood pressure

• Using a Sphygmomanometer & Stethoscope (to listen)
• Pressure is raised until blood flow stops
• Systolic pressure: the first sound heard after lowering the pressure, it is just below the actual sys. pressure.
• Diastolic pressure: the pressure is further lowered until you hear a second sound, of continous blood flow indicating you are just below the diastolic pressure.

Effective Pumping of Heart

Requires 2 things:

1. Sequential contraction of chambers
2. Coordinated Contractions of muscle cells (within chamber)

...this all depends on the special features of the heart muscle...

Sequential Contraction...

(depend on specialized cells)

Sequential contraction of chambers depends on the specialized cells ( all joined by Gap Junctions) that initiate action potential and contraction:

• Sinoatrial Node: a modified cardiac muscle, the primary pacemaker, initiate's action potentials w/o stimlation (located in rt. atrium)

• Atrioventricular Node: Delays start of ventricular contraction (by ~0.1 seconds)
• "Bundles of His" & "Purkinje" fiber; transmit action potential to Ventricle walls

Heartbeat Coordination

Atrioventricular Node

&

Bundle of His

Atrioventricular Node: is located at the juncition between the atria and the ventricles. Its is stimulated by the depolarization of the atria.

Bundles of His: consists of modified cardiac muscle fibers that do not contract ( are stimulated by a slight delay of ~0.1 sec).