Frog Heart Muscle

Contraction Pathway SA node Atria Ventricles AV node Gap Junctions 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

PNS Sensory neurons Motor neurons Autonomic NS Parasympathetic NS Sympathetic NS Somatic NS

Autonomic Nervous System Parasympathetic NS Sympathetic NS Rest and Digest Decrease HR, BP, contraction strength/rate, increase systole duration Fight or Flight Increase HR, BP , contraction strength/rate, decrease systole duration

SA Node Firing Rate Altered 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 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!