Cardiac action potential Flashcards
What are the different types of cardiac fibers?
- Fast response fibers
- Slow response fibers
What is the primary difference between fast and slow response action potentials?
Fast response action potentials are characterized by rapid depolarization, while slow response action potentials have a gradual depolarization.
What is the role of intercalated discs in cardiac muscle?
Intercalated discs allow cardiac muscle to act as a functional syncytium by facilitating mechanical and electrical connections between fibers.
What is autorhythmicity in cardiac muscle?
The ability of cardiac muscle to initiate its own rhythm regularly without extrinsic stimulus.
What are the phases of the action potential of nodal tissues?
- Resting membrane potential (RMP) - phase 4
- Depolarization - phase 0
- Repolarization - phase 3
What is the significance of spontaneous depolarizations in the heart?
To trigger the excitatory wave of the heart.
What is the resting membrane potential (RMP) in fast response action potentials?
-90 mV
Fill in the blank: The SA node is the _______ pace-maker of the heart.
[primary]
What are the three types of pacemakers in the heart?
- Primary pacemaker - SA node
- Secondary pacemaker - AV node
- Tertiary pacemaker - Purkinje fibers
What is the mechanism of cardiac muscle contraction?
Excitation-contraction coupling involving Ca++ influx and interaction between actin and myosin.
What triggers the release of Ca++ ions from the sarcoplasmic reticulum?
Inward Ca++ current from the extracellular fluid.
What is the absolute refractory period (ARP)?
The period during which no new action potential can be triggered, preventing tetanization.
What is the relative refractory period (RRP)?
The period during which a stronger stimulus can excite the heart.
What does the strength of cardiac muscle contraction depend on?
The intracellular Ca++ concentration.
What is the effect of the sympathetic nervous system on heart contractility?
Increases contractile force.
What is the significance of voltage-dependent ion channels?
They are involved in action potential generation and can be pharmacological targets for drug therapies.
Fill in the blank: The _______ is responsible for the initiation of the excitation wave at a regular rhythm.
[SA node]
What is the role of the Ca++ pump in cardiac muscle relaxation?
Pumps Ca++ back into the sarcoplasmic reticulum, reducing intracellular Ca++ concentration.
True or False: Cardiac muscle acts as a true syncytium.
False
What is the effect of antiarrhythmic drugs on action potentials?
They inhibit spontaneous action potential generation, decreasing frequency.
What are the components of the cardiac conductive system?
- SA node
- AV node
- His Bundle
- Bundle Branches
- Purkinje Fibers
What does the term ‘functional syncytium’ refer to in cardiac muscle?
The heart acts as a single unit due to intercalated discs despite the absence of protoplasmic continuity.
What is the significance of the ECG in relation to cardiac action potentials?
It correlates the electrical events of the heart with cardiac action potentials.
What is the normal heart rate range for adults?
60 - 90 beats per minute.
What is the effect of parasympathetic nervous system on heart rate?
Decreases heart rate.
What is CICR in the context of cardiac muscle contraction?
Calcium-induced calcium release from the sarcoplasmic reticulum.
Fill in the blank: The _______ are sites of attachment between cardiac muscle cells.
[intercalated discs]
What is the primary function of contractile fibers in the heart?
Perform the mechanical work of pumping.
What happens during the plateau phase of fast response action potentials?
There is a balance between K+ efflux and Ca++ influx.
