Contraction Pathway Gap Junctions SA node Atria Increases in Na+ conductance; causes AP; autorrhythmic Slows transmission of AP Ventricles AV node Bundle of His Purkinje fibers
Heart rate • Frequency of AP created by the SA node • Fires 100x/min on own • Adult heart rate is about 70 bpm. WHY?
Regulated by: • Sympathetic neurons • Parasympathetic neurons • Levels of circulating epinephrine
Autonomic Nervous System Parasympathetic NS Sympathetic NS Fight or Flight Increase HR, BP , contraction strength/rate, decrease systole duration • Rest and Digest • Decrease HR, BP, contraction strength/rate, increase systole duration
SA Node Firing RateAltered by: • Changes in autonomic nerve activity • Sympathetic • Vagal • Circulating hormones • Hyperthyroidism • Hypothyroidism • Serum ion concentration • Hyperkalemia • Hypokalemia • Cellular hypoxia • Usually from ischemia • Drugs
Drugs • Ca 2+ channel blockers • β blockers • Atropine • Nightshade plant (tomato family)
Amphibian Heart • 2 atria 1 ventricle • O2 and deO2 blood separated by conusarteriosis and timing of atrial contractions. • Pressure differences is systemic and pulmonary circuits can allow O2 and deO2 blood to mix via an intercardiac shunt. Helps stabilize O2 content in blood, thermoregulate, and allow the skin to be used as a respiratory organ. • Sinus venosus = SA node in mammals.
Homework • Write a Results, and Discussion for this lab. • Answer ALL questions within the text.
Course Reviews • Please do them ASAP. • Print the confirmation at the end. • 5 extra credit points for completing this!! • Please provide constructive criticism if you have any. I’m always trying to improve my teaching!