Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
5 Cards in this Set
- Front
- Back
|
What do the circulatory and respiratory system do? |
They work together to supply oxygen and remove carbon dioxide. The respiratory system provides gas exchange The circulatory system transports blood containing gases between lungs and body cells. Maintaining homeostasis is essential as cells will die from oxygen deprivation and buildup of waste. |
|
|
Physiology of Blood Circulation |
As ventricles contract, blood is pumped (creating pressure) into the pulmonary trunk and the aorta. This pressure exerts a force against the walls of the blood vessels through which blood flows. Pressure depends on the volume of blood present, the size of the blood vessel, the rate of blood flow and any resistance to blood flow. Blood pressure maintains a functional and stable movement of blood from the heart, to regions of the body, and back into the heart. A cardiovascular center is located in the medulla oblongata where it receives input from various sensory receptors (proprioceptors, baroreceptors, chemoreceptors) and higher brain centers (cerebral cortex, limbic system). Output from the cardiovascular center is via sympathetic and parasympathetic neurons of the autonomic nervous system. Sympathetic cardiac acceleratory nerves extend out to the sinoatrial node (SA node), atrioventricular node (AV node) and most of the myocardium. These nerves release the neurotransmitter norepinephrine and the rate and force of heart contractions are increased. Parasympathetic cardiac inhibitory nerves terminate in the SA node, AV node, and atrial myocardium. They release acetylcholine which decreases heart rate and has a lesser effect on decreasing the force of contraction. The cardiovascular center also continuously sends impulses to the smooth muscle in blood vessel walls via vasomotor nerves. These are sympathetic neurons that cause vasoconstriction and an increase in blood pressure. Hormones help regulate blood pressure by altering heart function, blood vessel diamete and adjusting total blood volume. In response to sympathetic stimulation, the adrenal medulla releases th hormones epinephrine and norepinephrine. These hormones will increase heart rate and the force of hea contractions, also constricting veins and arterioles. Epinephrine however, will dilate arterioles in skelet and cardiac muscle to increase blood flow during exercise. |
|
|
Electrical Activity of the heart |
*The heart is not dependent on the nervous system for its rhythmic contractions. Rhythm is set by specialized cardiac muscle cells called autorhythmic fibers which are self-excitable. These fibers can spontaneously depolarize and act as pacemakers. They form the cardiac conduction system, a network of specialized cardiac muscle cells that provide a pathway for electrical activity to progress through the heart. Cardiac excitation normally begins at the sinoatrial (SA) node (dominant pacemaker of the heart) which lies in a cellular cluster in the right atrial wall. Impulses originating from this node spread to adjacent myocardial cells and are propagated as a wave of depolarization through preferential atrial pathways. Contraction of the muscular walls of the atria immediately follows atrial depolarization. The atrioventricular (AV) node, located within the lower interatrial septum, relays the impulse from the atria to the ventricles. After the impulse passes through the AV node, it enters the fiber tract known as the AV bundle or bundle of His. This short pathway subdivides into right and left bundle branches. They extend through the interventricular septum toward the apex of the heart. The smallest conductive elements, the Purkinje fibers, are distributed throughout the inner walls of the ventricles, throughout the muscular septum. After being dispersed throughout the entire inner surface of the ventricles, the cardiac impulse moves toward the outer surface of the heart as a generalized wave of depolarization. The ventricles then contract with a wringing sort of action, pushing the blood upward toward the semilunar valves. |
|
|
How is the rhythmic contraction of the heart created? |
Specialized cardiac muscle cells that are self-excitable depolarize and act as pacemakers for the heart. They form a network of cardiac muscle cells that provide a pathway for electrical activity in the heart. |
|
|
What is the pathway of cardiac excitation? |
Excitation begins in the sinoatrial node (the dominant pacemaker) Impulses spread to myocardial cells and a wave of depolarization follows through atrial pathways. Contraction of atria follows after atrial depolarization. Atrioventricular Node relays impulse from atria to ventricles. Enters bundle of his that subdivides into right and left beaches. |
