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Skeletal muscle) long cells
Long cells are bundled together in fascicles
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Skeletal muscle) independent (2)
Independently innervates & contracts
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Skeletal muscle) striated
Because of overlapping of thick & thin filaments
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Skeletal muscle) contractile
It can shorten or lengthen
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Skeletal muscle) T-tubule & S.R
Well developed T-tubule & sarcoplasmic reticulum system that is used for communication between nerve & muscle cell innervated by Somatic N.S
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Smooth muscle ) small cells connected by gap junctions
Small cells connected by gap junctions so neighboring cells can communicate with one another
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Smooth muscle ) Non-striated
They are no striated, they have a smooth tecture
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Smooth muscle ) no t-tubules and SR less developed
- No t-tubules & SR less developed
- *they do receive innervation but usually by ANS
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Cardiac muscle) consists of fibers...
Arranged in bundles
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Cardiac muscle) how many planes does cardiac muscle cover?
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Cardiac muscle) what does the contraction do?
Squeezes blood out
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Cardiac muscle) why is it significant that the cardiac muscle covers 3 planes?
It allows the heart to contract in different directions to get the blood out
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Types of cells of cardiac muscle) Contractile cells: description (3)
-short
-branched
-striated
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Types of cells of cardiac muscle) Contractile cells: T-tubules & SR & triads (2)
It has some t-tubules & SR
No triads
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Types of cells of cardiac muscle) Contractile cells: where do the t-tubules arrive?
At the level of the Z-line not at A-I junction (like the skeletal muscle)
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Types of cells of cardiac muscle) Contractile cells: general contraction
- Similar to skeletal muscle
- ***look it up to review ***
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Types of cells of cardiac muscle) Contractile cells: mitochondria
It contains extensive amounts of mitochondria which is important bc you do not want the heart to fatigue at all during exercise or resting
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Types of cells of cardiac muscle) Pacemaker cells: description (3)
-thin
-branched
-non-striated
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Types of cells of cardiac muscle) Pacemaker cells: do these contract?
no
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Communication between cardiac cells) how do they communicate?
All cells are connected by intercalated discs (gap junctions) reinforced by desmosomes
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What do desmosomes do?
Resist torsion to help cells not to pull apart when contractions occur
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Intercalated discs found between (3)
-contractile-contractile
-pacemaker-pacemaker
-contractile-pacemaker
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Side note on the way each skeletal muscle cell is innervated
It is innervates by a particular nerve & receive signal to contract from the specific nerve
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Main function of heart
pump blood
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How does heart pump blood?
Performed by sequential contraction and relaxation of musculature which causes blood to be pushed out of chambers (during contraction) and to fill chambers (during relaxation).
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Excitation contraction coupling: steps (4)
1. Excitation initiated by P.M cells then spreads out
2. Excites contractile cells which will initiate
3. Cross bridge formation & contraction thus
4. Shorten sarcomeres and blood is pumped out
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Cardiac AP) what initiates it?
Pacemaker cells
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Cardiac AP) what's embedded in each pacemaker cells (3)
-leaky Na channels
-fast CA channels
-K channels
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Cardiac AP) Leaky Na channels
- They are always open
- *concentration outside of cell is higher than inside
- **maintained by Na/K ATPase
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Electrical events of pacemaker cells) (5) steps
- 1. Leaky Na channels causes depolarization
- *Na keeps coming in causes depolarization
2. Opening of fast CA channels to depolarize the cell further
- 3. Calcium channels close at peak depolarization
- *at around 0 mV
4. Potassium channels open
5. repolarization to -55-60 mV
***continuous process***
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Electrical events of contractile cells) what 3 channels do contractile cells have embedded in their plasma membrane
-fast Na channels
-slow CA channels
-K channels
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Electrical events of contractile cells) which 2 ions flow through intercalated discs from other cells?
CA and Na
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Electrical events of contractile cells) steps (6)
1. Na leaking in from neighboring cells opens fast Na channels
2. Na channels close rapidly and depolarization causes
- 3. Slow CA channels to open
- *open and close slowly
- **when they open it allows CA to enter the cell & keep cell depolarize so there's enough time for cross bridge to be formed & for contraction of heart muscle to begin
- 4. K permeability decreases
- *short time
5. Increase K and decrease CA permeability
6. Contraction of cell occurs after AP thru cross bridge formation
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Location, sequence of events, PM cells: Sinoatrial node (2)
-70-75 bpm
-sets heart rate of the cell
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Location, sequence of events, PM cells: Atrioventicular node
-50 bpm
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Location, sequence of events, PM cells: where is SA node located
Inside RA
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Location, sequence of events, PM cells: SA node does 70-75 bpm meaning
PM cells depolarize at 70-75 bpi on average
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Location, sequence of events, PM cells: how do SA node pump 70-75 times?
Leaky channels causes depolarization at around this pace every time
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Do SA node & AV node connect?
They do not connect rather they have contractile cells between them which is how they communicate with one another
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Location, sequence of events, PM cells: AV bundle (3)
-connects with AV node
-it beats 30 bpm
-extends to join with L&R bundle branch
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Location, sequence of events, PM cells:L & R bundle branch
These extend down to apex of heart where they begin to divide off into perkinje fibers
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Location, sequence of events, PM cells: Perkinje cells
-extend into inter-ventricular walls of heart & contractile cells
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What happens if SA node is damahged>
AV node would take over
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What's EKG?
Electrokardio graph
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What is EKG
graphic representation of electrical activity of heart
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What are 5 components of EKG
-isoelectric line
-p-wave
-QRS
-t-wave
-ST segment
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ekg) isoelectric line
- Represents point in which cells are at rest
- * -55-60
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ekg) P wave (2)
-atrial depolarization
- occurs in atria b/c SA nose is in there
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ekg) QRS
- Represents depolarization of the ventricles
- *perkinje fibers delivering it to the walls
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ekg) T-wave
- Ventricular repolarization
- *phase in which cell is getting ready for next AP
- **Kicks out K while preventing NA from coming out
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ekg) ST segment
Alteration here signifies abnormal AP conduction
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ekg) where is atrial repolarization
During ventricular are depolarizing so its overridden by it on the graph
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ekg) Arrhythmias: Bradycardia
- Slow heartbeat
- *below 60 bpm
- **athletes usually have a pulse below 60 but considered healthy because their hearts are so efficient
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ekg) Arrhythmias: tachycardia
- Fast heart beat
- *above 100 at rest
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ekg) Arrhythmias: ectopic focus
Particular cell in heart will take over the heartbeat so that cell will dictate the heart pulse by using its own
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ekg) Arrhythmias: PVC (1+2)
Premature ventricular contraction
- -type of ectopic focus
- -spontaneous not regularly
- *too much coffee can precipitate this
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ekg) Arrhythmias: Fibrillation
- Uncoordinated contraction of heart meaning all contractile cells are firing in an uncoordinated way
- *ventricular fibrillation: death
- *atrial fibrillation: can live with it
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ekg) Arrhythmias: heart block (1+3)
Blockage between SA node & AV node due to AV node being damaged so current doesn't travel all the way, heart attack, or genetic problem.
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Normal modification of heart rate) Sympathetic
Increases heart rate
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Normal modification of heart rate) parasympathetic
Decreases heart rate
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Normal modification of heart rate) what would happen if they were removed?
- We would have no discreet control over heart so difficulty functioning well
- *slow heart during run
- *fast heartbeat during sleep
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