Lecture 2 Flashcards
_______________: striated, short, thick, branched cells, one central nucleus surrounded by light-staining mass of ________ (for ATP–> contraction)
cardiomyocytes; glycogen
___________ _______: join cardiomyocytes end to end with three features
1.
2.
3.
intercalated discs
1. Interdigitating folds
2. Mechanical junctions
3. Electrical junctions
Interdigitating folds: _________ & __________ area of contact
interlock; increase
Mechanical junctions
- ______________: broad; actin of the thin myofilaments is anchored to the plasma membrane; cells linked via transmembrane proteins
- __________: punctate
- fascia adherens
- desmosomes
Electrical junction (gap junctions): _____ flow between cells; allows entire myocardium of either two _____ or two _______ to act like single, unified cell
ions; atria; ventricles
Metabolism of Cardiac Muscle
- Cardiac muscle depends almost exclusively on __________ respiration to make ATP
- rich in __________ and __________
- HUGE __________: fills ____% of cell
- aerobic
- myoglobin; glycogen
- mitochondria; 25%
Cardiac muscle is adaptable to different __________ fuels
- ______ _____ (___%)
- ____________ (35%)
- ________, ________, and ________ (5%)
- more vulnerable to __________ deficiency than lack of a specific fuel
- ___________ resistant because it makes little use of _____________ fermentation or oxygen debt mechanisms
organic
- fatty acids (60%)
- glucose (35%)
- ketones, lactate, and AAs (5%)
- oxygen
- fatigue; anaerobic
Conducting System of Heart- ___% of myocardium (too small to appear on ECG alone)
- coordinates the heartbeat
- composed of an internal __________ (__________) and nerve-like conduction pathways (made of modified _________________) through the myocardium
1%
- pacemaker (SA node); cardiomyocytes
The cardiac conduction system:
1. _______ node fires
2. excitation spreads through ________ myocardium
3. _____ node fires
4. Excitation spreads down ______ bundle (left and right)
5. __________ ______ (subendocardial conducting) network distributes excitation through __________ myocardium
- SA
- atrial
- AV
- AV
- purkinje fibers; ventricular
Electrical and Contractile Activity of the heart are ______ the same thing!
NOT
Cycle of events in heart
_________= contraction
_________= relaxation
- can refer to contraction and relaxation of either type of chamber, they usually refer to the action of the ___________
systole
diastole
- ventricles
___________: normal heartbeat triggered by the SA node
- adult at rest is typically ___-___ bpm (_____ tone- ANS) w/o ______ tone the SA node would depolarize ______ bpm
- SA node exhibits ____________________
sinus rhythm
- 70-80; vagal; vagal; 100
- autorhythmicity
Pacemaker Physiology
SA node does not have a stable _____________
- Starts at -60 mV and drifts upward due to slow _____ inflow
-gradual depolarization is called _________ ________
- When it reaches threshold of _____mV, voltage-gated fast ______ and ______ channels open
-Faster depolarization occurs peaking at ___mV
- ______ channels open and ____ leaves the cell
-causing __________
-once ______ channels close, ______ __________ starts over
- When SA node fires, it sets off ___________ (muscle contractions)
resting membrane potential
- Na+
- pacemaker potential
- (-40); Ca2+; Na+
- 0
- K+; K+
- repolarization
- K+; pacemaker potential
- heartbeat
SA node stimulates two ______ to contract almost simulatneously
- it reaches AV node in ____ ms
Signal ______ _____ through AV node
- delays signal ______ ms which allows the _______ time to fill
Signals travel _____ _______ through AV bundle and subendocardial conducting network (Purkinje fibers)
__________ _________ (contraction) progresss up from the apex
atria
- 50 ms
slows down
- 100; ventricles
very quickly
ventricular systole
Electrical behavior of the myocardium
_______________________
1. voltage-gated _____ channels open
2. _____ inflow depolarizes the membrane and triggers the opening of still more _____ channels, creating a positive feedback cycle and a rapidly rising membrane voltage
3. _____ channels close when the cell depolarizes, and the voltage peaks at nearly _____ mV
____________________
4. _____ entering through slow _____ channels prolongs depolarization of membrane, creating a _________ which falls slightly because of some ____ leakage, but most ____ channels remain closed until the end
___________________
5. _____ channels close and ____ is transported out of cell. ____ channels open, and rapid _____ outflow returns membrane to its resting potential
Depolarization
1. Na+
2. Na+; Na+
3. Na+; +30mV
Plateau
4. Ca2+; Ca2+; plateau; K+; K+
Repolarization
5. Ca2+; Ca2+; K+; K+
