khanghuynh Cheat Sheet by keitapotato

1) AP in cardiac contra­ctile cells differs consid­erably from the AP in cardiac autorhymic cells
2) -90mV resting potential
3) rapid rising phase of AP result of Na+ entry on opening of fast Na+ channels at threshold (-70mV)
4) Brief repola­riz­ation after potential reaches its peak bc of limited K+ efflux on opening of transient K+ channels, coupled w/ inacti­vation ofNa+ channels

dual-pump system includes 4 chambers:
- left and right Atria, Ventricles
- chambers on right pump = oxygen­-poor blood through pulmonary circul­ation -> lungs
- chambers on left pump = oxygen­-rich blood through systempic circul­ation -> body tissues

- small terminal fibers of specia­lized, cardiac pacemaker cells that extend from Bundle of His and spread throughout the ventri­cular myocardium
- 30 A.P./min
- In normal condit­iona, follow SA node (and AV node) at 70 AP/min

Sinoatrial (SA) Node:
- right atrium near the opening of the superior vena cava
- exhibits an autorh­yth­micity of 70 action potentials per min and leads the activity of the other pacemaker structures int he heart

Atriov­ent­ricular (AV) Node:
- Cardiac pacemaker cells located at the base of the right atrium
- exhibits an autorh­yth­micity of 50 action potentials per min
- Under normal condit­ions, this node follows faster SA node at 70 A.P./min

Endoca­rdium: thin layer of endoth­elial tissue lining the interior of each chamber

Myocar­dium: middle later of heart wall, composed of cardiac muscle
- cardiac muscle cells are connected end-to-end by interc­alated disks (formed desmosomes and gap-ju­nct­ions)

Epicar­dium: thin external membrane covering the heart and is filled with a small volume of perica­rdial fluid

- mechanism of Ca++ entry into the cytosol is different from that in skeletal muscle cells

- T-tubule membranes have dehydr­opy­ridine receptors (volta­ge-­gated Ca++ channels). open and allow Ca++ to flow into cytosol

- Ca++ entry triggers further release of Ca++ from sarcop­lasmic reticulum. these 2 sources of Ca++ activate power stroke of contrs­tra­ction

- # of activated crossb­ridges is propor­tional to the cytosolic Ca++ conc.

cardiac cells that conducts pacemaker acitivty fromt he right atrium to the left atrium
- from SA node to AV node

99% of cardiac muscle cells are contra­ctile and don't initiate their own action potentials

1% are autorh­ythmic and intrin­sically initiate their own action potentials at a regular frequency

- interc­alated discs
1)desm­osomes = mechan­ically hold cells together
2)gap-­jun­ctions = provide paths of low resistance to the flow of electrical current between muscle cells

- gap-ju­nctions enable the cardiac muscle to form a functional syncytium (a group of cells that act as a single functional unit despite mainta­ining their individual identi­ties)

1) AP in cardiac contra­ctile cells differs consid­erably from the AP in cardiac autorhymic cells
2) -90mV resting potential
3) rapid rising phase of AP result of Na+ entry on opening of fast Na+ channels at threshold (-70mV)
4) Brief repola­riz­ation after potential reaches its peak bc of limited K+ efflux on opening of transient K+ channels, coupled w/ inacti­vation ofNa+ channels

- heart muscle generates its own rhythmic electricla activity (autor­hyt­hmi­city)
- occurs due to pacemaker activity
- nodes: pacemaker cells grouped together in specia­lized regions
- 2 nodes
- control rate and coordi­nation of cardiac contra­ctions

Left Atrium - receives oxygen­-rich blood from left and right pulmonary veins
- pumps blood through the left atriov­ent­ricular (AV) (biscuspid or mitral) valve into the left ventricle
Left Ventricle - Receives oxygen­-rich blood from left atrium and pumps blood through aortic (semil­unar) valve into the aorta

Sinoatrial (SA) Node:
- wall of the right atrium near opening of superior vena cava
- 70 action potentials per min

Atriov­ent­ricular (AV) Node:
- base of right atrium
- exhibits an autorh­yth­micity of 50 action potentials per min
- Under normal condit­ions, this node follow faster SA node at 70 A.P./min

tract of specia­lized, cardiac pacemaker cells that originate sa tthe AV node and divides and projects into the left and right ventricles

- PA conducted relatively slowly through the AV node resulting in a delay of approx. 100ms
- to ensures that ventricles contract after atrial contra­ction

1) Prolonged plateau phase is result of slow Ca2+ entry on opening of :-type Ca2+ channels, coupled w/ reduced K+ efflux on closure of several types of K+ channels
2) rapid falling phase is result of K+ efflux on opening of ordinary voltag­e-gated K+ channels, as in other excitable cells
3) Resting potential is maintained by opening of leaky K+ channels