Frog Heart Muscle Contraction Pathway SA node Increases in Na+ conductance; causes AP; autorrhythmic Gap Junctions Atria 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: 1. Sympathetic neurons 2. Parasympathetic neurons 3. Levels of circulating epinephrine PNS Sensory neurons Motor neurons Autonomic NS Parasympathetic NS Somatic NS Sympathetic NS Autonomic Nervous System Parasympathetic NS Sympathetic NS • Rest and Digest • Fight or Flight • Decrease HR, BP, • Increase HR, BP , contraction strength/rate, contraction strength/rate, increase systole duration decrease systole duration SA Node Firing Rate Altered by: 1. 2. 3. 4. Changes in autonomic nerve activity – Sympathetic – Vagal Circulating hormones – Hyperthyroidism – Hypothyroidism Serum ion concentration – Hyperkalemia – Hypokalemia Cellular hypoxia – 5. 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 conus arteriosis 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!