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!