Download Physiology (L02) Slide#35 : -This slide is only to show you how

Physiology (L02)
Slide#35 :
-This slide is only to show you how organized the myocytes or the cardiac cells
are in the heart tissue, the reason of this organization is because you want the
electrical activity to move down the heart in a very organized manner and you
want the heart to contract in a very organized manner.
-Action potential moves through communication of cells via gap junctions.
Slide#37 : reminding of blood flow, go to slide#20.
-Action potential comes before the mechanical contraction of the heart, so
when the right atrium contracts, there must be an action potential that pushes
the blood forward.
-Contraction of the heart moves in the same direction of the electrical activity.
(electrical activity moves from base to apex of the heart.)
Slide#38:
-SA node is below the superior vena cave, in the right atrium.
-electrical activity moves from atrium to ventricle but NOT through the valves, it
moves through one certain area that is in the middle and called: AV node.
-So, action potential goes through atria, and meets in AV node, then goes to
interventricular septum where the area is divided into left and right ventricles,
it moves down, then it goes back up through the Purkinji fibers.
-Purkinji fibers: are important part of the conduction system and allow the
electrical activity to move quickly, they have a large diameter (means usually
faster due to less resistance.)
Slide#40: back to slide#56 for more details.
-Numbers in this slide show how long it takes action potential to move through
different points of the conduction system.
-in AV node the action potential slows down, in order to allow sufficient time for
completing atrial depolarization and contraction. (full emptying of the atrium)
-since contraction follows the electrical activity, this explains why the
ventricles contract in the bottom upward, because the action potential there
moves from down upward.
- the bottom of the ventricle is depolarized before the top.
Slide#41:
-70ActionPotential/minute = the heart rate 70beat/minute.
-Acetylcholine binds to muscarinic receptors and lowers the heart beating
rate.
Slide#45:
-SA node, AV node and Purkinji fibers can fire an action potential by their own,
but in different rates.
-Rate of heart beat is equal to the action potentials of SA node because it is the
fastest in generating action potentials.
-If the SA node is damaged, and the AV node has to generate its own action
potential, the heart rate will be 40-60beats/minute.
Slide#47:
-Each action potential takes 0.8 of a second, moves gradually from -60 mV to
the threshold that is -40mV.
- This diagram shows the SA node action potential because it lacks the fast Na+
channels, and that leaking of Na+ explains the gradual increasing. If we
changed the actions of that diagram: by affecting voltage gated ion channels,
we indirectly affect the heart rate. If we hyperpolarize (make the tissue more
negative) = we will decrease the heart rate, by increasing the time to get the
threshold.
Slide#48:
-the rate of the transplanted hearts = 100 beats, because there is no
parasympathetic regulation with acetylcholine to decrease the heart rate.
Slide#94:
-Electrical activity comes before the contraction, so what will happen if the
electrical activity is disrupted? –there will be no contraction. When they give a
shock to people with heart attack, they zero all action potentials and starting
the heart again, in order to make the heart activity organized. The purpose is
reorganization of heart activity.
)‫ العرض مش متوفر لجماعة االيفون‬-‫ايش بنعمل؟ بنقيم البطارية وبنرجعها‬، ‫(بالزبط زي لما يعلق الموبايل‬
Slide#52:
-Remember: If we block SA node, AV node will take over, if we block AV node,
Purkinji fibers will take over, if we block Purkinji fibers, there will be a problem
and a shock is needed.
Slide#53:
-The diagram represents the action potential in the ventricles.
-A lot of Ca++ in Plateau phase is responsible of contraction.
-The heart begins to contract in the start of Plateau phase.
Slide#54:
-If Tetrodotoxin is given to a human being , the voltage gated Na+ channels are
blocked. In this way, they discover which channels are responsible for the
firing state of action potential.
Slide#55:
-The diagram represents the action potential in atrium: we have a slow Na+
entry.
Slide#57:
-First shape is the relaxation phase of the heart.
Slide#59: This slide is to show you how the action potential moves across the
heart.
-Action potential moves from: *top to bottom in atria.
*bottom upwards in ventricles.
Slide#60:
-Remember: the SA node alone initiates action potentials which give a 100
beats/minute of the heart, but because of the parasympathetic regulation and
release of acetylcholine, the heart rate is 70 beats/minute.
-When a person has a heart attack, and you do the CPR for him, what is the
appropriate drug to be given? –Epinephrine, because it increases the
contractility of the heart.
Slide#61:
-SA node spreads to excite the working fibers, so the SA node fires and goes
through all the fibers.
Slide#62:
-This diagram is to show you how is our heart innervated with the autonomic
nervous system.
**-Vagi: plural of vagus, and it is a cranial nerve that is associated with the
parasympathetic control of the heart.
-SA node is mostly controlled by the parasympathetic area.
-Sympathetic nerves are highly connected to the left ventricle, so when we do
exercises, usually we have the release of Adrenalin (Epinephrine) which helps
in increasing of heart rate and the contractility by increasing Ca++
concentration.
Slide#63:
-Speeds rate of depolarization = increases the heart rate.
Slide#64:
-Antagonist: is something that prevents something from happening, ex: Na+
channels blockers are called Na+ channels antagonists.
-Agonist: is something that stimulate something to happen.
-Muscarinic receptors are especially for acetylcholine which is responsible for
decreasing the heart rate, so: if the muscarinic receptor is blocked, the heart
rate will increase, whereas if it is stimulated and opened, the heart rate will
decrease.
- Hypoxia or Ischemia: Area of the heart that does not give oxygen, and
becomes very painful __ means that an artery of the heart is blocked.