lab13: circulatory system II and the respiratory system

• The body's cells use oxygen for metabolic reactions that produce ATP from the breakdown of ingested nutrients
• Carbon dioxide is released as a waste product
• The circulatory and respiratory systems cooperate to supply oxygen (O2) and remove carbon dioxide (CO2)
• The respiratory system provides for gas exchange, while the circulatory system transports blood containing gases between the lungs and body cells
• Maintaining homeostasis is essential to prevent cells from dying due to oxygen deprivation and the buildup of waste products
• Blood pressure is crucial for maintaining a functional and stable movement of blood from the heart to various regions of the body and back into the heart
• The cardiovascular center is located in the medulla oblongata and receives input from 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 to the sinoatrial node (SA node), atrioventricular node (AV node), and most of the myocardium, releasing norepinephrine to increase heart rate and force of contractions
• Parasympathetic cardiac inhibitory nerves terminate in the SA node, AV node, and atrial myocardium, releasing acetylcholine to decrease heart rate with a lesser effect on contraction force
• The cardiovascular center sends impulses to smooth muscle in blood vessel walls via vasomotor nerves, causing vasoconstriction and an increase in blood pressure
• Several hormones help regulate blood pressure by altering heart function, blood vessel diameter, and adjusting total blood volume
• In response to sympathetic stimulation, the adrenal medulla releases epinephrine and norepinephrine to increase heart rate, force of contractions, and constrict veins and arterioles
• Epinephrine dilates arterioles in skeletal and cardiac muscle to increase blood flow during exercise
• Hormones affecting blood volume will be discussed in the lab involving the urinary system
• The fundamental rhythm of the heart is set by specialized cardiac muscle cells called autorhythmic fibers
• autorhythmic fibers can spontaneously depolarize and act as pacemakers. They form the cardiac conductionsystem, a network of specialized cardiac muscle cells that provide a pathway for electrical activity toprogress through the heart.
• Cardiac excitation normally begins at the sinoatrial (SA) node in the right atrial wall between the inlets of the inferior and superior vena cava
• Impulses from the SA node spread to adjacent myocardial cells and are propagated as a wave of depolarization through preferential atrial pathways
• Contraction of the atrial walls follows atrial depolarization
• The atrioventricular (AV) node relays the impulse from the atria to the ventricles
• The AV node is located within the lower interatrial septum
• After passing through the AV node, the impulse enters the AV bundle or bundle of His
• The AV bundle subdivides into right and left bundle branches that extend through the interventricular septum toward the apex of the heart
• Purkinje fibers are the smallest conductive elements distributed throughout the inner walls of the ventricles, the muscular septum, and the muscular papillae
• The cardiac impulse moves from the inner surface of the ventricles towards the outer surface as a wave of depolarization
• Electrocardiography is important in diagnosing abnormal cardiac function
• An Electrocardiogram (ECG or EKG) records the electrical changes of the heart
• Electrocardiography views the human body as a volume conductor with the heart seen as a dipole
• Electrodes are placed on the skin surface to record electrical activity initiated at the SA node and transmitted throughout the heart
• The normal ECG consists of a P wave, a QRS complex, and a T wave
• T wave:

  • Represents ventricular repolarization
  • Longer duration and lower amplitude than the QRS complex
  • Inverted T wave is considered abnormal
• P wave:

  • Represents atrial depolarization
  • Average duration is 0.08 seconds
  • Amplitude not greater than 0.3 millivolts
• Abnormalities in ECG waves and time intervals can help detect myocardial infarcts or heart conduction problems
• QRS complex:

  • Represents ventricular depolarization
  • Duration is 0.08 seconds
  • Amplitude of the R wave not over 2.5 millivolts
• Stress testing is used to analyze heart function, especially in individuals with normal ECG patterns under stress
• Epinephrine and acetylcholine were applied to a normal beating frog heart to record heart activity
• epinephrine caused he heart rate to increase and strength of contraction to increase
• Applicati=ion of epinephrine simulated control by the sympathetic part of the autonomic nervous system
• Acetylcholine causes the heart rate to decrease and the strength of contraction to decrease.