Test 4 Cardio Flashcards
Cardiac myocytes (Cardiac Muscle) have a high number of what? This allows for production of what without fatigue of the muscle?
- High Number of Mitochondria
- Allows continuous high-level aerobic production of Adenosine Tri-Phosphate (ATP)
What structural aspects of Cardiac Muscle allow for Rapid Synchronous spread of action potential between cells?
- Fewer and Larger T-Tubules
- Intercalated Discs
Cardiac muscle relies on what action in order to convert electrical signal to muscle contraction?
Rapid release and re-uptake
of Intracellular Calcium stores
What structure in the heart initiates action potential? What is the intrinsic rate of this structure?
Sinoatrial Node (SA) -60-100bpm
What structure in the heart is responsible for delaying the electrical signal? What is the intrinsic rate of this structure?
Atrioventricular Node (AV) -40-60bpm
Sympathetic Nervous stimulation of the heart will cause what to occur with the heart?
Increase SA Node Rate
Increase Force of Contraction
Parasympathetic Nervous stimulation of the heart will cause what to occur with the heart?
Decrease SA Node Rate
Decrease Force of Contraction
What is defined by; Autonomous process that results in the organized, sequential, contraction and relaxation of the chambers of the heart?
Cardiac Cycle
When looking at an ECG the P-wave represents what?
Atrial Depolarization
What portion of an ECG represents ventricular depolarization?
QRS-Complex
The only repolarization wave to be seen on an ECG is called what? And what portion of the heart is repolarizing?
T-Wave
Ventricular Repolarization
What is the name of the Membrane Channels that Muscle Contraction relies on?
Voltage-Dependent Calcium Channels (VDCCs)
What type of Voltage-Dependent Calcium Channel (VDCC) is the predominant one found in Cardiac cells?
L-Type Channel
What subunit (Protein) of the L-Type Voltage-Dependent Calcium Channel (VDCC) forms the pore?
Alpha1 subunit w/6 trans-membrane Alpha-Helices
Open and Close upon Voltage Changes
What is the function of the Disulfide-linked Alpha2-Gamma subunit of the L-Type VDCC?
- Anchors the Alpha1 subunit to cell membrane
- Augments response to Voltage Changes
What subunit of the L-Type VDCC catalyzes
ATP + GMP –> ADP + GDP?
Beta Subunit (Guanylate Kinase)
What affect does the conversion of GMP to GDP have on the L-Type VDCC?
Regulates Alpha1 subunit (pore) voltage sensitivity
–(i.e. Beta subunit activity allows smaller depolarization’s and channel opening)–
What provides the initial stimulus causing the L-Type VDCC to respond?
Action Potential of SA Node, AV Node, or Purkinje Fibers
How does the L-Type VDCC respond to the action potential from either the SA Node, AV Node, or Purkinje Fibers?
Opens by depolarization of the cell membrane
What affect does Epinephrine (Adrenaline) and Dopamine have on the heart?
Increase Heart Rate
and/or
Increase Stroke Volume
