Access over 20 million homework & study documents

search

Unit 2 Class Notes 2

Content type
User Generated
Rating
Showing Page:
1/45
Unit II Cardiovascular, Lymphatics & Immune Systems
PP1 Cardiovascular Physiology Part I
Cardiac Muscle
Cardiac muscle fibers are single nucleated and branching.
Fibers within the networks are connected by intercalated discs, which consist of desmosomes and gap junctions
Self-excitatory and electrically coupled
Rate of contractions modulated by autonomic nervous system
innervation is neuroendocrine in nature (i.e. no “motor end plates”)
Features of Cardiac Muscle
Intercalated disks
Junctional complexes joining cells together, with longitudinal and transverse portions
Gap Junctions
Provide ionic continuity so that when one fiber contracts, the next will automatically contract as a syncytium.
Histology of Cardiac Muscle Cells (what are some unique features of cardiac muscle?)
Autorhythmic Cells:
Cardiac muscle cells are autorhythmic cells because they are self-excitable.
They repeatedly generate spontaneous action potentials that then trigger heart contractions.
These cells act as a pacemaker to set the rhythm for the entire heart.
They form the conduction system, the route for propagating action potential through the heart muscle.
Cardiac Action Potential
An impulse in a ventricular contractile fiber is characterized by rapid
Depolarization
Cardiac cell resting membrane potential is -90mv
excitation spreads through gap junctions
fast Na+ channels open for rapid depolarization
Plateau phase
250 msec (only 1msec in neuron)
slow Ca
+2
channels open, let Ca
+2
enter from outside cell and from storage in sarcoplasmic reticulum,
while K
+
channels close
Ca
+2
binds to troponin to allow for actin-myosin cross-bridge formation & tension development
Repolarization

Sign up to view the full document!

lock_open Sign Up
Showing Page:
2/45
Ca
+2
channels close and K
+
channels open & -90mv is restored as potassium leaves the cell
Refractory Period
In General: the period of time which an excitable membrane needs to be ready for a second stimulus once it
returns to its resting state following an excitation.
In Cardiac Muscle:
The refractory period of cardiac muscle is dramatically longer than that of skeletal muscle.
Prevents tetanus from occurring and ensures that each contraction is followed by enough time to allow the
heart chamber to refill with blood before the next contraction.
Physiology of Contraction
1) Rapid depolarization due to Na+ inflow when voltage-gated fast Na+ Channels open
2) Plateau (Maintained depolarization) due to Ca2+ inflow when voltage-gated slow Ca2+ channels open
and K+ outflow when some K+ channels open
3) Repolarization due to closure of Ca2+ channels and K+ outflow when additional voltage-gated K+ channels
open
Action Potential in Cardiac Muscle (https://www.youtube.com/watch?v=v7Q9BrNfIpQ)
Calcium Ion and Cardiac Contraction
Cardiac action potentials cause an increase in Ca
2+
around myofibrils
Ca
2+
enters the cell membranes during the plateau phase
Additional Ca
2+
is released from reserves in the sarcoplasmic reticulum
Heart Chambers and Valves
Structural Differences in heart chambers
The left side of the heart is more muscular than the right side
Functions of valves
AV valves prevent backflow of blood from the ventricles to the atria
Semilunar valves prevent backflow into the ventricles from the pulmonary trunk and aorta
Differences between Left and Right Ventricles
Valves of the Heart
AV Valves
Tricuspid
Bicuspid
Aortic & Pulmonary Valves

Sign up to view the full document!

lock_open Sign Up
Showing Page:
3/45

Sign up to view the full document!

lock_open Sign Up
End of Preview - Want to read all 45 pages?
Access Now
Unformatted Attachment Preview
Unit II Cardiovascular, Lymphatics & Immune Systems PP1 Cardiovascular Physiology Part I Cardiac Muscle Cardiac muscle fibers are single nucleated and branching. Fibers within the networks are connected by intercalated discs, which consist of desmosomes and gap junctions Self-excitatory and electrically coupled Rate of contractions modulated by autonomic nervous system ◦ innervation is neuroendocrine in nature (i.e. no “motor end plates”) Features of Cardiac Muscle Intercalated disks Junctional complexes joining cells together, with longitudinal and transverse portions Gap Junctions Provide ionic continuity so that when one fiber contracts, the next will automatically contract as a syncytium. Histology of Cardiac Muscle Cells (what are some unique features of cardiac muscle?) Autorhythmic Cells: Cardiac muscle cells are autorhythmic cells because they are self-excitable. They repeatedly generate spontaneous action potentials that then trigger heart contractions. These cells act as a pacemaker to set the rhythm for the entire heart. They form the conduction system, the route for propagating action potential through the heart muscle. Cardiac Action Potential An impulse in a ventricular contractile fiber is characterized by rapid Depolarization ◦ Cardiac cell resting membrane potential is -90mv ◦ excitation spreads through gap junctions ◦ fast Na+ channels open for rapid depolarization Plateau phase ◦ 250 msec (only 1msec in neuron) ◦ slow Ca+2 chann ...
Purchase document to see full attachment
User generated content is uploaded by users for the purposes of learning and should be used following Studypool's honor code & terms of service.

Anonymous
Super useful! Studypool never disappoints.

Studypool
4.7
Trustpilot
4.5
Sitejabber
4.4