2/25- Heart Continuation (Exam 2) Flashcards
What is a extended refractory period?
Period of time where new action potential cannot occur
Allows heart to keep the regular steady heart beat without going into fibrillation
What happens with summation and tetanus?
Is impossible to have in heart because it’s already at rest
Can kill you because the heart is a pump that needs to contract and relax fully
What is the nodal system?
Wiring of the heart
What is the fibrous skeleton of heart?
Disc of CT
Goes from one side of heart to other
Separates electrical events between atriums and ventricles as separate ones
Electrical events cannot go through
What is automaticity or autorhymicity?
Ability for cardiac muscle cells to spontaneously depolarize and then contract
What is a Sinoatrial Node (SA Node)?
Pacemaker of the heart
Depolarizes faster
After it depolarizes atriums depolarize then contracts
What is Atrioventricular Node (AV Node)?
Captures depolarization before being lost at the fibrous skeleton
Rapidly transmits depolarization to wires connected to it (atrioventricular bundle)
What is the Atrioventricular bundle or bundle of his?
Wire that passes through fibrous skeleton of heart
Depolarization comes here then sent to right and left bundle branches
What happens to the depolarization after the right and left bundle branches?
Goes to Purkinje Fibers
Then sweeps up ventricles causing them to contract and blood goes through circuit
Then depolarization is lost at fibrous skeleton of heart
What is the Electrocardiogram (EKG or ECG)?
Recording of electrical occurrences
What is a Electrocardiograph?
Machine that records recording
What causes the P wave?
Depolarization of Atriums
What causes the QRS complex?
Depolarization of the ventricles
What causes the T wave?
Ventricular repolarization
Why can’t you see the atriums repolarize in the recording by the EKG?
It happens simultaneously of the QRS complex
What is the Magnitude of Waves?
Direct measure of the voltage (millivolts)
What happens when the magnitude of wave forms is large?
Hypertension (high blood pressure)
Can lead to enlarged heart
What happens when the magnitude of wave forms are smaller?
Cardiac tamponade
What is a lead?
Combos of electrodes
12 different combos (12 angles)
Each lead gives some version of PQRST
What are the first 3 leads of a 12 lead?
Standard leads
- simple 2 electrode combos
- written as Roman numerals (1, 2, 3)
What is the middle 3 leads in a 12 lead?
Augmented leads
- 3 electrode combos
- aVR (right wrist)
- aVL (left wrist)
- aVF (left ankle)
What are the last 6 leads in a 12 lead?
Chest leads or precardial leads
V1- V6
What are the 3 influences how fast a heart beats?
1) rate of pacemaker (SA Node)
2) autonomic innervation
3) atrial reflex or brainbridge reflex
What is the autonomic innervation?
Nervous system
Sympathetic
- nonepinepheine
- increases fire rate of SA Node
Parasympathetic
- hyperpolarize SA Node
- more difficult for action potential to occur so heart slows down
What is Atrial Reflex or Bainbridge Reflex?
Triggered if too much blood from systemic circuit enters the heart from the right atrium at once
Heart speeds up
What is in the medulla oblongata?
Cardiac control centers
What is a cardiac control center?
Controls heart pace when it increases or decreases from normal rate
Have parasympathetic and sympathetic connections to the heart
What are the 2 inputs for the cardiac control centers?
1) Baroreceptors
2) Chemoreceptors
What are Baroreceptors?
Measure blood pressure
Speed of gears affects BP
Raise pressure- sympathetic
Lower pressure- parasympathetic
What are Chemoreceptors?
Blood gases (oxygen and carbon dioxide)
Low O2 and high CO2= faster heart beat (sympathetic)
High O2 and low CO2= lower heart beat (parasympathetic)
Where are Baroreceptors and chemoreceptors found?
Aorta
Carotid Arteries (in neck)
What is cardiac rate?
How fast the heart is beating
Beats per min
Beats/ min
To figure out:
- pulse
- stethoscope
- EKG
What is bradycardia?
Heart rate is too slow
Lower than 60
Lower than 50 feel symptoms
What is tachycardia?
Heart rate is too fast
100 or more
What is End Diastolic Volume (EDV)?
Volume of blood in left ventricle after it is done filling up
What is Stroke Volume (SV)?
How much blood comes out if left ventricle when it contracts a moment later
mL/ beat
What is the ejection fraction?
Comparing Stroke volume to end diastolic volume
What percentage of blood is left in the left ventricle
Never 100%
SV/ EDV x 100
What is cardiac output?
Volume of blood ejected by left ventricle over one minute
SV x cardiac rate = cardiac output
mL/ min
What are 3 things that affect SV?
1) End Diastolic Volume
2) contractility
3) Total Periphereal Resistance
What is contractility?
How hard the ventricle squeezes when if contracts
What is the Total Peripheral Resistance?
Resistance blood meets when trying to squeeze the blood out of the ventricle
Force to push blood out
More force = less blood
Less force = more blood
What is Frank Starling Law of Heart?
When total peripheral resistance is more and less blood is out there is more contractility
In healthy hearts
