CAS BI 315 Chapter Notes - Chapter 6: Ringer'S Solution, Reagent, Sinus Venosus
1 Jul 2018
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Lab 6: Characteristics of Frog Cardiac Muscle
I. Cardiac Muscle
A. Comparison w/ skeletal muscle:
A.1. Different: fibers branch, reunite, and spread in many directions
A.1.a) In skeletal muscle, strength of contraction depends on
number of motor units stimulated (all or none law applies to single
muscle unit)
A.1.b) In cardiac muscle, all or none law states if a muscle fiber
contracts, it contracts maximally for a given starting condition (all
or none applies to the entire heart)
A.1.c) ACh has diff effects:
(A.1.c.1) In cardiac= INHIBITORY (muscarinic receptors)
(A.1.c.2) In skeletal= EXCITATORY (nicotinic receptors)
A.1.d) Diff refractory periods:
(A.1.d.1) Cardiac= LONG ref period
(A.1.d.2) Skeletal= SHORT ref period
A.2. Same: striated
B. Intercalated discs: connect fibers electrically through gap junctions that flow
action potentials to travel easily from cell to cell
C. Syncytium: functional network of connected cardiac cells
D. AV node: electrically connects atria and ventricles
D.1. Stimulation of any single atrial or ventricular fiber results in action
potential over the entire atrial/ventricular mass, causing full contraction of
the heart
E. Heart refractory period: long, summation and tetany cannot occur
F. Heart pumping Regulation:
F.1. Autoregulation in response to volume changes in blood
F.1.a) Frank Starling mechanism:intrinsic ability of heart to
adapt to changing volumes of venous return
F.2. Reflex control by autonomic nervous system
G. GREATER END DIASTOLIC VOL = STRONGER VENTRICLE CONTRACTION
H. All striated muscles: contract with greater force when muscle is stretched
I. Parasympathetic and Sympathetic influence
I.1. Change HR
I.2. Change contraction strength
J. In vertebrates: normally parasymp decreases and symp increases HR and
contraction strength
J.1.Humans normally confine effect to HR and not strength of contraction
K. SA node= PACEMAKER (in frogs called the SV node Sinus venosus)
K.1. Maintains intrinsic HR rate
K.2. Starts the depolarization of the heart
K.3. Located in RA
K.4. Has fastest rate of depolarization, followed by atria and ventricles
II. Procedure
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Document Summary
Different: fibers branch, reunite, and spread in many directions. In skeletal muscle, strength of contraction depends on. A. 1. a) number of motor units stimulated (all or none law applies to single muscle unit) In cardiac muscle, all or none law states if a muscle fiber contracts, it contracts maximally for a given starting condition (all or none applies to the entire heart) Diff refractory periods: (a. 1. d. 1) cardiac= long ref period (a. 1. d. 2) skeletal= short ref period. Intercalated discs: connect fibers electrically through gap junctions that flow action potentials to travel easily from cell to cell: syncytium: functional network of connected cardiac cells, av node: electrically connects atria and ventricles. Stimulation of any single atrial or ventricular fiber results in action potential over the entire atrial/ventricular mass, causing full contraction of the heart: heart refractory period: long, summation and tetany cannot occur, heart pumping regulation: Autoregulation in response to volume changes in blood. F. 2. adapt to changing volumes of venous return.
