Physiology Flashcards
What is the functional unit for Cardiac muscle?
Sacromere
How is the nucleus located in cardiac muscle fibers?
Centrally located
True or False ? The refractory period is long in skeletal muscle but short in Cardiac muscle .
FALSE!!!! It is LONG in Cardiac muscle but short in skeletal muscle.
S for shirt as for skeletal.
What are the structures that make up the Cardiac conduction system ?
- Purkinje System
- Atrioventricular node(AV node)
- Bundle of His
- Internodal Atrial pathways
- Sinoatrial node (SA node )
PABIS
Where is Bachman’s Bundle located?
In the left atrium
What are the two types of Cardiac Muscle cells?
Contractile cells
Auto-rythmic cells
What activates the contractile cells?
A change in the membrane potential
True or False? The action potential in cardiac muscle cells are ________ than that of skeletal muscle and the contraction phase is also _____.
Wider action potential
Longer contraction phase
True or False? In Cardiac muscle cells ,fibers are not anchored at ends which allows for greater sarcomere shortening and lengthening.
TRUE!!
Through what structure does current from autorythmic cells spread to contractile cells?
Through Gap Junctions
True or False? The refractory period is long in skeletal muscle but short in cardiac muscles.
FALSE!! The refractory period is short in skeletal muscle but very LONG in cardiac muscle.
True or False? Cardiac muscle CANNOT sum action potentials or contractions and cannot be tetanized.
TRUE!!
Where are autorhythmic cells found?
Through the conduction system ( SA node, AV node, Bundle of His, Pukrinje fibres)
What is the Pacemaker potential?
It is slow depolarisation due to both OPENING of Na+ channels and the CLOSING of K+ channels.
Where is the SA node located?
At the junction of the superior vena cava with the right atrium.
Fill in the blanks. “ The SA node develops structures from the _____ side of the embryo while the AV node develops structures from the _____ side of the embryo?
SA node- RIGHT
AV node- LEFT
What are the two types of voltage-gated Calcium channels in the heart?
T (for transient) channels and the L (for long-lasting) channels.
Fill in the blanks. “ The Ca2+ current ( due to opening of T channels completes the _________, and the Ca2+ current due to opening of L channels produces _____.
T channels - completes the pacemaker potential
L channels - produces the impulse.
What is the time period for AV-nodal delay?
0.1 seconds
What is the number of action potentials per minute procuced at the SA node?
70-80
What is the number of action potentials per minute produced at the AV node?
40-60
What is the number of action potentials per minute produced at the Purkinje fibres?
20-40
Why does the AV nodal delay take place?
There is a delay in the action potential from reaching the ventricles, in order to allow the atria to empty blood into ventricles before the ventricles contract.
What structure in the heart allows for the AV nodal delay?
Bundle Branches
What happens during the plateau phase?
Sodium channels close and there is a SLOW INFLUX of calcium channels through L- type calcium channels.
What happens during the Absolute refractory period of the myocyte?
The myocyte is unexcitable to stimulation as all sodium channels are inactivated following the open (depolarized) state.
What happens during the relative refractory period of the myocyte?
Stimulation produces a weak action potential that propagates, because some of the Na channels have moved from inactivated to closed, making them able to reopen in response to electrical stimulus.
Where is the AV node located?
The AV node is located in the right posterior portion of the interatrial septum
What causes the P-wave in an ECG?
Atrial depolarisation, initiated by the SA node.
Where does Ventricular depolarisation begin?
At the apex of heart
What causes the QRS complex?
Ventricular depolarisation
Fill in the blanks. “ Ventricular repolarisation begins at apex causing the ______ wave?
T wave
True or False? Unipolar leads are leads I,II and III.
FALSE!! Bipolar leads uses those.
Which Lead uses a third ground (RL) electrode ?
Bipolar leads
What leads are unipolar limb leads?
aVR, aVL , aVF
Which leads are unipolar chest leads?
V1 through to V6
Where is the RA electrode positioned?
It is positioned anywhere on the right arm or below the right clavicle in the midclavicular line.
Which electrode is positioned positioned anywhere on the left leg or left midclavicular line below the last palpable rib?
LL electrode
Where is La electrode positioned?
It is positioned anywhere on the left arm or below
the left clavicle in the midclavicular line
True or False? The RL electrode is ositioned anywhere on the left arm or below the left clavicle in the midclavicular line?
TRUE!!
Where should V1 be placed?
Fourth intercostal space to the RIGHT of the sternum.
Which chest lead is positioned at the Fifth intercostal space at midclavicular line?
V4
Where is V2 located?
Fourth intercostal space to
the Left of the sternum.
Which lead is located between leads V2
and V4?
V3
True or False? V5 is level with V4 at left anterior
axillary line.
TRUE!
Where is V6 located?
Level with V5 at left midaxillary line.
What leads provide an inferior, superior, and lateral views of heart (Frontal Plane)?
I, II, III, aVR, aVL and aVF
What leads provide anterior, and lateral views of heart (Horizontal Plane)?
Include leads V1- V6
What is the normal duration for the PR interval?
0.12-2.0 seconds
What is the difference between bipolar leads and unipolar leads?
Bipolar leads - Record the difference in electrical potential between a positive and negative electrode.
Unipolar Leads- Uses only one positive electrode and a reference point calculated by the ECG machine.
Which leads provide an anterior view of the heart?
V1-V4
Fill in the blanks. “ Leads II, III and aVF provide a what view of the heart ?
Inferior View
What leads provide a view of the entire lateral heart wall?
Leads I, aVL, V5 and V6
What is an artifact?
This is markings on an ECG tracing that are not a product of the heart’s electrical activity.
- Patient movement is among its many causes
- Can mimic life threatening dysrhythmias
Which lead is most often chosen as the Rhythm strip?
Lead II
What is the normal amplitude of a P- wave?
0.05- 0.25mV
What is the normal duration of a P-wave?
0.06-0.10 seconds
What is the normal duration of the PR interval ?
0.12- 0.20 seconds
What is the normal amplitude of the QRS complex?
0.5- 3.0 mV
What is the normal duration for the QRS complex?
0.06- 0.10 seconds
What is the name of the starting point of the ST segment ?
J- point
What does the QT interval measure?
It measures the time and ventricular depolarisation and repolarization.
What is the normal duration of the QT interval?
0.36 - 0.44 seconds
What is the purpose of the U wave?
It measures depolarisation of the papillary muscles/ Purkinje fibres
What is a T-wave Inversion usually an indication of?
Ischaemia
What is the name of the three bundles of atrial fibres that contain Purkinje-typpe of fibres and connect SA node to AV nodes?
The Anterior fibres ( Buchman Bundle)
Middle fibres ( tract of Wenckebach)
Posterior fibres ( Tract of Thorel)
True or False? The bundle of His is found in the left ventricle.
FALSE!! It is found in the Intraventricular septum where it gives off a left bundle brand and continues as a right bundle branch.
Fill in the blanks, In Lead I the electrodes are connected so that an upward deflection is inscribed when the _______ arm becomes ______.
Left arm becomes positive!!!
In Lead II , where are the electrodes placed and what is positive?
On the right arm and left leg
Left leg is positive
In Lead III where are the electrodes placed?
The electrodes are on the left arm and left leg with the leg being positive
What does Einthoven’s law state?
Lead I + Lead III = Lead II
How is the Electrical axis of the heart calculated?
It is the mean QRS vector
Fill in the blanks. “Right axis deviation normally represents _______”
Right ventricular hypertrophy
An inverted T wave can be an indication of what condition?
Ischaemia
Fill in the blanks. “ An elevated ST segment can be an indication of ______.”
Myocardial Infarction
In which degree of heart block does the the atria and ventricle beat independently of each other and is usually treated with an artificial pacemaker?
Third degree AV block ( Complete block)
In which degree of heart block has a progressive lengthening of PR interval until a P wave is not followed by a QRS complex ( dropped) ?
Second degree Av block Morbitz Type I ( Wenckebach )
When the PR interval is fixed and prolonged > .20 seconds it is described as a ?
First degree heart block
Fill in the blanks. _________ is randomly dropped beats without progressive PR prolongation and at risk for degenerating to third-degree block .
Second degree type II ( Morbtz II)
Which degree heart block can be as a result of Lyme disease?
Third degree heart block
Which condition has no discernible P waves?
Atrial fibrillation
True or False? Hypoxia increases intracellular ATP.
FALSE!! It DECREASES intracellular ATP
Why is a inverted T wave usually an indication for Ischaemia?
This is because ischaemic tissue does not depolarise normally .
What are the causes of Myocardial Ischemia?
Atherosclerosis
Vasospasm
Thrombosis and Embolism
Decreased ventricular filling time - tachycardia
Decreased filling pressure in coronary arteries
- severe hypotension or aortic valve disease
Fill in the blanks.” Myocardial injury is usually represented by _____.”
ST elevation
When the Q wave changes it is normally an indication of what condition?
Myocardial infarction
What is the electrical axis of a normal QRS complex?
Between 0 and +90 degrees
The first heart sound S1 is produced by ?
Closure of Mitral and Tricuspid valves
What does the A wave represent?
Atrial contraction
What does the C wave represent?
The c wave is the next upward deflection in pressure, corresponding to con- traction of the right ventricle, causing the tricuspid to bow inward toward the right atrium, transiently increasing pressure.
What does the V wave represent?
I occurs during venous filling (v for “villing”
When is the second heart sound S2 produced?
In isovolumetric ventricular relaxation - ( pulmonary and aortic valve closes)
True or False? In skeletal muscle, ATP is not stored in any appreciable quantity.
TRUE
Fill in the blanks. A rise in metabolism depends on ________.
- The cross- bridge cycling rate of myosin and actin
- Substrate availability
- Accumulation of metabolic byproducts
What percentage of ATP is produced by Aerobic metabolism at rest?
100%
Fill in the blanks. At rest “ 2/3 of fuel is contributed by _____ by ______ while 1/3 of fuel is contributed by ______ by ________.
2/3 - Fats by Beta Oxidation
1/3 - CHO by aerobic glycolysis
True or False? At rest your blood lactate levels are high .
FALSE!! They are low
What is Oxygen Deficit / Debt?
This is the period of exercise during which level of oxygen consumption is below necessary to supply all ATP required.
True or False? Trained individuals have a lower oxygen deficit.
TRUE!!
ATP and creatine phosphate ( CP) is what kind of energy source?
Alactic anaerobic source
Glucose from stored glycogen in the absence of oxygen is what kind of energy source ?
Lactic anaerobic source
Glucose, lipids and proteins in the presence of oxygen is what kind of source?
Aerobic source
How long is Alactic anaerobic sources maintained for?
8-10 seconds
What type of physical activities utilizes Alactic anaerobic sources?
‘Explosive sports’ - weightlifting, jumping , throwing, 100m running , shot put and 50m swimming
What type of physical activities utilises lactic anaerobic sources?
” Short intense sport ( less than 2 mins) Gymnastics, 200 to 1000 m running, 100 to 300 m swimming
What is the recovery time for lactic anaerobic sources?
1 to 2 h
What are the effects of lactic acid on the skeletal muscles?
↓ the rate of ATP hydrolysis
↓ efficiency of glycolytic enzymes
↓Ca2+ binding to troponin
↓ interaction between actin and myosin (muscle fatigue)
Where does lactate change back into pyruvate and by what process ?
In the liver - Gluconeogenesis
Fill in the blanks. During rest , Lactic acid is converted back to _____ and oxidised by _____.
Pyruvic acid and oxidised by skeletal muscles
What is the recovery time for activities that utilised that Aerobic source?
24-48 hours
What type of activities utilises the aerobic source?
Long sports - available after 2-4 mins of exercise
What organs are fuel aerobic sources stored in?
Muscles, Adipose tissue and liver
When is Aerobic respiration used?
After 2-4 minutes of exercise
When is Glycolysis used during exercise ?
After 8-10 seconds
What is Vo2 max?
It is the peak oxygen consumption that is influenced by age, sex and training level of person performing exercise.
What is the name of the plateau in peak oxygen consumption, reached during exercise involving a sufficiently large muscle mass ?
Maximal oxygen consumption
What is maximal oxygen consumption limited by?
The ability to deliver Oxygen to skeletal muscles and muscle oxidative capacity .
During Oxygen Deficit/Debt, What is the primary fuel source initially?
Anaerobic systems
What is Oxygen Deficit?
It is the volume difference between an ideal and real oxygen uptake.
What is Oxygen debt?
It is the extra volume that is needed to store all energetic systems .
True or false? Untrained individuals have a higher oxygen deficit while trained individuals have a lower oxygen deficit.
TRUE!!
What is the unit for VO2 max?
mL/kg/min - VO2 max is measured in milliliters of oxygen used in one minute per kilogram of body weight (mL/kg/min).
What is Cardiac Output?
Cardiac Output is Strove Volume x Heart Rate
CO = SV x HR
What is the unit for Cardia Output?
mL/min
Which leads provide a view of the anterior heart wall?
Leads V3, V4
Which leads provide a view of the septal heart wall?
Leads V1 & V2
Ischemia is represented on an ECG via?
ST depression or T inversion ( because ischemic tissue does not depolarise properly
An ST elevation on ECG can indicate what condition?
Myocardial Injury
Myocardial injury can as a result of ?
Prolonged ischemia
Which wave of an ECG can a myocardial infarct be detected on?
Q wave ( it may get shorter )
Fill in the blanks. “ The left bundle branch divides into _____, _______ &________.”
Septal, Anterior and Posterior fascicles
What is the norm duration of the QRS complex
0.06-0.10 seconds
What happens during a bundle branch block?
It leads to one or both bundle branches failing to conduct impulses, produces delay in depolarisation of the ventricle it supplies .
What are the key characteristics of a bundle branch block?
- Widened QRS complex (0.12 seconds greater in duration)
- ‘M’ shaped chest leads.
What is the ECG readings for a Right Bundle branch block(RBBB)?
wide, tall, notched QRS complex in leads V1 & V2 .
Look for slurred S waves in leads I , V5 & V6.
What are the causes of a right bundle branch block?
- Anterior wall MI
- Coronary artery disease
*Hypertension - Scar Tissue that develops after heart surgery
- Viral or bacterial myocarditis
- Pulmonary embolism
- Drug toxicity
- Congenital defect ( atrial septal defect)
