2/25- Heart Continuation (Exam 2) Flashcards by Rebecca Charidemou

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

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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

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What is the nodal system?

Wiring of the heart

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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

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What is automaticity or autorhymicity?

Ability for cardiac muscle cells to spontaneously depolarize and then contract

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What is a Sinoatrial Node (SA Node)?

Pacemaker of the heart

Depolarizes faster

After it depolarizes atriums depolarize then contracts

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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)

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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

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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

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What is the Electrocardiogram (EKG or ECG)?

Recording of electrical occurrences

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What is a Electrocardiograph?

Machine that records recording

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What causes the P wave?

Depolarization of Atriums

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What causes the QRS complex?

Depolarization of the ventricles

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What causes the T wave?

Ventricular repolarization

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Why can’t you see the atriums repolarize in the recording by the EKG?

It happens simultaneously of the QRS complex

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What is the Magnitude of Waves?

Direct measure of the voltage (millivolts)

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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