KINESIOL 1YY3 Lecture Notes - Lecture 3: Tricuspid Valve, Atrioventricular Node, Interatrial Septum

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Heart skeleton - fibrous plate of connective tissue
Heart skeleton represented in white excluding the valves
Important because we want to have control over the action potentials that move
through the heart
Insulates the electrical signals that go through the atria and ventricles
Forms a plate that separates the atria from the ventricles
Structural support and an attachment point for the valves
Fibrous rings around the valves
As it contracts it pulls the apex towards the fibrous plate - it's going to twist due to the
orientation of the fibers - twists & rings - allows the blood to pump out more efficiently
Direction of the muscle fibers
Cardiac muscle are elongated but don't run the whole length - attached in
series
Cardiac muscle cells CAN have branch points - extension to a neighboring cell
Not as many myofibrils compares to skeletal muscle
Not multinuclear - 1 to 2 nuclei - located in the center of the cell
Cardiac muscle cell has more space compared to skeletal muscle cell
In order to continuously supply the tissue with energy, there is a lot of
mitochondria - never runs out of ATP
At every Z-disk there is a T- tubule
Myofibrils aren't very dense and less organized
Sarcoplasmic reticulum - doesn't have large regions - rarely comes in contact
with the T- tubules - contraction takes longer than skeletal muscle cells
Intercalated disks - red wavy lines - specialized connections between two
cardiac muscle cells - lots of ridges and waves in these disks - the waves of one
cell fit into the waves of the other cell - wave patterns match
All the cardiac muscle cells are connected to each other at some point - they
use electrical synapses - connected by a gap junction
Gap junction - electrical synapse - allows action potentials from moving from one
cytoplasmic cell to the other cytoplasmic cell
Stops the cells from ripping apart when the myofibrils contract
Desmosome - acts like a stapler - holds the two cells together - anchors one cell to the
next
Intercalated disks
Have less myofibrils - conducting cardiac muscle fibers
Node is a lump/mass of specialized cardiac muscle cells
Arrows represents action potentials moving
Can generate spontaneous action potentials
Master of generating spontaneous action potentials
It does it first and faster than the rest of the conducting cells
Located where the superior vena cava attaches the right atrium
SA node
Located in the interatrial septum,
Action potentials are slowed down - because we want to allow the atria to
completely contract before the ventricle begins to contract - slowing down
AV node
Lecture 3 CVS Heart Physiology
January 11, 2016
1:30 PM
Kinesiology 2YY3 Page 1
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