Lecture 1 Test 4 Flashcards
What muscle is considered a multi nucleated cell?
Skeletal muscle
Cardiac and smooth muscles are connected to their neighbors by
gap junctions
What is a visceral (unitary) smooth muscle? (ex. cardiac cells)
muscles that contract as a unit
cardiac smooth muscles share action potentials through…….
gap junctions
Place where 2 cells meet with each other that has grooves, indentations, jagged edges (one cell fits into the next cell). Allows for more gap junctions (increase surface area)
Intercalated discs
Alternating light and dark bands in cardiac muscles. (alignment of actin/myosin)
Striations
Each cardiac muscle has how many nucleus?
one
Does the sarcomere in a cardiac smooth muscle look the same as skeletal muscles?
Yes
Ex. of cells that “patch” off areas of dead cells
Stem cells but it is a long process
How do you make stem cells work faster?
If you have a lot of money.
Maybe we can figure it out in the future.
What do fibroblasts do?
It lays down scar tissues where heart stem cells can’t fix. (controlled rate)
What is it called when your heart muscles are laying down uncontrolled unnecessary scar tissues?
CHF
What happens when you have a lot of scar tissue in the heart?
Action potentials are unable to run through it and unable to contract.
What drug prevents unnecessary scar tissue deposition?
ACE inhibitor blocks RAAS (Angiotensin II; growth hormone system). Fibroblasts are controlled by Angiotensin II activity.
Considered as a growth hormone/factor.
RAAS: especially angiotensin II
What controls the activity of fibroblasts in the heart?
Angiotensin II
What does people think ACE inhibitors mainly do?
Afterload reducer
In A&P, prevents the growth factor of scar tissue placement
ACE inhibitors/ARBs are not good when pregnant because
It crosses the placenta, the womb uses angiotensin II for the growth factor of a developing fetus for maturation.
Arrangement of heart muscle
Syncytial/syncytium connections
How are the 2 distinct ventricle layers put together?
connected in a cross pattern. (contracts in different direction.)
ex. wringing out water from a towel
How does the heart ventricles pump blood out?
in a wringing motion
Top half of the heart?
L/R atria
Below/bottom half of the heart
L/R ventricle (below the AV node)
What are the vast majority of the heart?
Muscle fibers/tissue
(myofibrils stacked on top of each other)
What’s the difference with muscle tissue and conduction tissue?
Conduction tissue doesn’t produce force.
(doesn’t have myofibrils)
*Better for AP
How can you send out AP quicker in cardiac muscles?
You can’t!!! (If you remove the myofibrils; which it isn’t possible)
1 cell layer thick endothelial of the heart is (deep cardiac muscle area)
Endocardium
bulk of the heart muscle wall
myocardium
Outside of the heart (superficial)
Epicardium
Space filled with fluid and mucus to prevent friction during cardiac contraction
Pericardial space
What symptoms might you have if the pericardial space had a loss of fluid/mucus or inflammation?
Increased friction during contraction and might feel like an MI
Connective tissue (sack) that encloses the heart
pericardium (not very stretchy)
How many layers does the pericardium have?
2 layers
Parietal pericardium (stretchy inner layer)
Fibrous pericardium (stiff outer layer)
Similar to the dura being stiff, leathery but for the heart
Fibrous pericardium
Muscle layer that’s very very (super) deep in the heart wall
Subendocardium
Where does an MI usually occur? why?
Subendocardium because that’s where the pressure are the highest. (wall pressure)
The deeper in the muscle = higher pressure
What happens when there’s high pressure in the chambers
difficult to perfuse, BP can only go so high
Clogged vessels and high wall pressure leads to…
Ischemia
What happens when heart is relaxed?
- The heart is not relaxed to an optimum degree.
- Actin filaments are overlapping the H band, so no H bands seen (under-stretched sarcomeres)
Marker of optimal degree of stretch
If the actin (I band) is stretched
Muscles within the ventricular muscles
Purkinjie fibers
Purpose of the purkinjie fibers?
Does it contract?
-Transmit Action potentials.
-No
Does action potentials occur in the ventricular muscles?
Yes
Difference between purkinjie fibers and ventricular muscles are
- Purkinjie fibers transmit APs; no contraction
- Ventricles transmit APs but they respond with contraction.
Purkinjie fibers Vrm
Ventricular Vrm
- -90 (permeable to Na+ at rest)
- -80 (permeable to Na+ at rest)
Main difference with the heart APs
Plateau phase
Can the heart spontaneously depolarize?
Yes if you give it enough time
Phase 0 has a slight incline due to
increased Na+ permeability at rest
What happens if the heart cell upstream has an AP?
It sends a downstream effect of APs to its neighboring cells
In a normal functioning heart, APs upstream are being produced by a pacemaker at a faster rate
We are unable to fire our own rate of self depolarization in the purkinjie fibers due to it being a really slow process.
What happens if there’s a complete heart block at the AV node?
The ventricles will have a longer time to fire an AP. (approx. 30+ secs)
What procedure will cause a complete HB?
Eye procedures.
- (five and dime)
Eye orbital pressure sensors > CN (V) (trigeminal nerve on the side of the face) > brain stem > vagus nerve (CN X) > prevent action potentials > 0 pulse x 30 secs.
5 phases of Cardiac AP
- Phase 4 (resting Vrm)
- Phase 0 (Fast Na+ influx via gap junctions)
- Phase 1 (end of phase 0, K+ ch closes, fast T-type Ca+ influx)
- Phase 2 (K+ ch closes, slow L type Ca+ influx)
- Phase 3 ( Ca+ ch closes, K+ channel opens)
Fast Na+ channels are
Fast influx for a short period of time
Length of APs for cardiac muscle
200 milliseconds for coordinated syncytium contraction
Neurons and skeletal muscles are…
similar; quick depolarization, and short period
When is K+ permeability depressed during an AP?
Plateau phase
When is Na+ permeability increased during an AP?
Phase 0
Ohm’s law
V = i x R
V = voltage
i = ionic current
R = resistant
