Cardiovascular system physiology Flashcards
What is a ECG?
Electrocardiogram
A graphic recording of electrical activity
Note: like taking a picture
Cardiac muscle cells
S S B F I
striated, short, branched, fat, interconnected
Gap junctions
used for electrical coupling
FUNCTIONAL SYNCYTIUM
Desmosomes
used for strong cell-cell adhesion; hold heart cells together/ prevent from separating during contractions
Which type of muscle contains pacemaker cells?
Only Cardiac muscle
Is tetanus possible in cardiac muscle?
No. only in skeletal muscle.
What are some similarities with Skeletal and Cardiac muscle?
- Muscle contraction is preceded by depolarization AP
- Excitation-contraction coupling occurs
What are some differences with Skeletal and Cardiac muscle?
- Stimulation: some cardiac muscle cells are SELF-EXCITABLE
2.
Contractile muscle fibers?
these make up the bulk of the heart and are responsible for pumping action
Explain how the Action Potential occurs in cardiac muscle
3 steps:
1. Depolarization
2. Plateau phase
3. Repolarization
Absolute refractory period almost =
muscle twitch»allows heart to fill again
heart needs to be stimulated in how many locations?
only one. The whole organ responds
Explain the activation of contraction in a cardiac muscle
‘drawing’
Does the heart need NS stimulation?
NO. however, rhythim can be altered by the ANS
Coordinated heartbeat is a function of
- Presence of gap junctions
- Intrinsic Cardiac Conduction System
Sa node is called the Pacemaker because
that group of cells depolarizes the fast cells. fastest rate, set the rate at which the heart is beating. sinus rhythm, how fast the heart beats
Pacemaker potentials:
auto-rhythmic cells that have unstable resting membrane potentials due to “funny” sodium that open at negative membrane potentials plus potassium channels that are slow to close
In auto-rhythmic cells what causes APs?
CALCIUM
What causes the influx of Calcium?
What is the sequence of Excitation?
S - Sinoatrial node
A - Atrioventricular (AV) node
A - Atrioventricular (AV) bundle (bundle of His)
R - Right and left bundle branches
Pacemaker of heart is in the right atrial wall. Why?
SA node is fastest, jap junctions, AP to spread fast
Where does depolarization take place in the ventricles?
In the Apex, through the purkinjie fibers
PNS and SNS w/ cardiac
Regulate the rate at which the heart is firing
Vagus nerve
Parasympathetic. Slows down the diastolic rate.
ECG records what?
only voltage (current flow) and time; only shows electrical events
What are the main features of the ECG?
P wave
QRS complex
T wave
P-R interval
S-T segment
Q-T interval
P wave
depolarization of SA node and atria
QRS complex
ventricular depolarization
T wave
ventricular repolarization
P-R interval
beginning of atrial excitation to beginning of ventrical excitation
S-T segment
entire ventricular myocardium depolarization
Q-T interval
beginning of ventricular depolarization through ventricular repolarization
what type of wave is not shown on an ECG?
Atrial repolarization
*Depolarization
Starts the contraction
*Repolarization
Relax
What is bradycardia?
heart beating too slow
What is tachycardia?
heart beating too fast/faster than normal
If you dont have the P wave what does that mean?
Does not have a working SA node
What does it mean if there are two P waves?
2nd degree heart block
Ventricular fibrillation
disorganized electrical activity. APs are happening randomly, disorganized
