Circulation & Perfusion
99
The coronary sinus just above the aortic valve fills with blood then filling the coronary arteries - the only arteries that fill during diastole
Autonomic Nervous system
Brainstem centers
This causes the myocardial fibers to create a unified contraction strong enough to pump blood out of the heart chambers - this spontaneous rhythm is call automaticity. SA node initiates a rate between 60-100 bpm
Ventrical conduction initiates a slower rate of usually less than 40 bpm but can be lifesaving
Electrical conduction of the heart
- receives and integrates feedback from chemoreceptors & baroreceptors - regulating cardiac function and blood pressure
Sinoatrial (SA) node - the pace maker of the heart - the impulse travels to both atria so they contract as a unit - impulse
Scope of tissue perfusion
Optimal perfusion
Impaired perfusion
No perfusion (tissue death)
Sympathetic fibers through the thoracic level of spinal cord stimulate the heart to beat faster & contract more forcefully
Atrioventricular (AV) node
impulse left & right bundle
of His impulse Purkinje fibers
the ventricles
impulse
Regulation of cardiovascular function
Autonomic Nervous System - regulates cardiovascular function through its influence on heart rate, muscle contractility, and vascular tone
Perfusion a definition
The cardiac cycle= the simultaneous contraction of the two atria followed a fraction of a second later by the contraction of the ventricles
Baroreceptors - located in the heart & blood vessels are sensitive to pressure changes. These receptors in the aortic arch & carotid arteries regulate heart rate & vascular tone
Chemoreceptors - located in the aortic arch & carotid arteries are sensitive to changes in blood pH, O2, & CO2 levels
Tissue perfusion refers to the flow of blood through arteries delivering nutrients and oxygen to cells and removing cellular waste products
Vascular System
- all blood vessels are innervated by sympathetic fibers & maintain a constant baseline state of partial contraction or tone
- maintain bp even when a person is resting or asleep
Parasympathetic fibers innervate the heart through the vagus nerve.
Parasympathetic stimulation causes slowed heart rate - but does not affect contractility
Their main function is to regulate ventilation, also they send information to the vasomotor center in response to low O2.
- Increased stimulation of the sympathetic nervous system varies upon body needs.
- If in fight or flight mode blood is shunted to skeletal muscles
Circulation
Flow of blood throughout the heart and blood vessels