Chapter 20 The Heart Flashcards by fermin chapa

The heart is ______, meaning it can contract without any stimulation of nerves

Auto-rhythmic

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The _____ contains specialized cells in nodes that contain excessive numbers of leaky sodium channels that allow them to slowly drift towards threshold and fire action potentials without any neurotransmitters

Heart

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Cardiac muscle cells, called ________, are connected by specialized proteins that form intercalated discs or gaps

Cardiocytes

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These gap junctions allow an action potential to spread like a wave from one cell directly to another without synapses

Intercalated discs

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Nerves and hormones can alter the cardiac rhythm by increasing or decreasing it, but do not cause the heart to contract.

ACH
Adrenaline

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Natural pacemaker of the heart
Located in the posterior area of the right atrial wall near the opening of the SVC
Generates action potentials faster than the AV node
Sets heart rate @ about 70-80 beats

Sinoatrial node

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The SA node starts an action potential which spreads throughout the two atria, causing them to contract

From the top down

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The _______ is located in the floor of the right atrium near the opening of the coronary sinus

Atrioventricular node

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If the SA node is destroyed due to damage and the atria could not contract, the ventricles would still contract and pump blood, but only about

60 bpm

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The AV node starts the spread of an AP through the

Bundle of his

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The _______ is located in the ventricular septum and carries the action potential from the AV bundle to bundle branches

Atrioventricular Bundle bundle of his

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Basic sequence of events of the conducting system

1. SA node automatically depolarizes and spreads an AP through the atria
2. Atria contract, action potential spreads through the internodal pathway
3. AP reaches av node
4. AV node spreads AP to bundle of his and bundle branches
5. Purkinje Fibers spread through ventricles
6. Ventricles contract, blood is pumped to lungs and system

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Contraction of a chamber

Relaxation of a chamber

Systole

Daistole

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What is the purpose of the fibrous skeleton of the heart ?

Connective tissue wall, stops the AP

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Is a recording of the electrical events of the cardiac cycle

Electrocardiogram ECG

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Atrial depolarization ➡️ atrial systole AV valves are open/SL valves are closed

P wave

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Ventricular depolarization ➡️ ventricular systole

QRS complex

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Ventricles are repolarizing 4 chambers are in diastole

T wave

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From the beginning of the P wave to the next P wave is called ?

Cardiac cycle

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Are not electrically isolated, but have specialized connections called gap junctions intercalated disks that allow an action potential to flow directly from one cardiocyte to the next.

Cardiocytes

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Cardiocyte action potentials are very prolonged and last approximately ______

250-300 milliseconds

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The resting membrane potential for a cardiocyte is

The threshold potential for a cardiocyte is

-90 MV

-75mv

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Steps of cardiocyte AP

Slow depolarization to threshold
Rapid depolarization
Plateau phase
Repolarization

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Leaky sodium channels in nodal cells of the SA node slowly allow NA+ ions to diffuse in and depolarize the cell to threshold

Depolarization to threshold

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Once threshold is reached, voltage gated sodium channels rapidly open and extracellaur NA+ flows into cell causing rapid depolarization to +30 mv

Rapid depolarization

As the cardiocyte reaches +30 mv, sodium channels rapidly close. Potassium channels open, but do so very slowly, allowing potassium to slowly leak out. At the same time, calcium channels in the membrane also open and allow CA to slowly leak into cell to counter balance the outward flow of K+, resulting in the action potential remaining constant near +30mv

Plateau phase

Slowly potassium channels open to repolarization. This closes the CA2+ channels and rapid repolarization occurs .

Repolarization

Beginning of the start of one atrial systole and ending at the start of the next atrial systole

Cardiac cycle

As blood enters the atria the av valves are open as as the ventricles are also in diastole allowing approximately ____ of ventricular filling to occur during atrial diastole.

70%

The atria do not have to contract to get blood into ventricles, atrial systole “tops off” the ventricles, filling that last ______ to get maximum blood flow.

30%

When does blood fill a chamber ?

Blood fills a chamber of the heart during the diastolic phase of the cardiac cycle

What causes blood to flow from one area to another ?

Blood flows from one area to another due to differences in pressure within the blood vessels. Blood pressure is the driving force

When does blood empty from a chamber ?

Empties during the systolic phase

Ventricular diastole

Av valves open SL valves closed

Ventricular systole

AV valves are closed SL valves are open

A period of time during ventricular systole where pressure is rising but is still lower pressure in the aorta

Isovolumteric contraction

When is blood ejected from the left ventricle

When pressure in the left ventricle is greater than the pressure in the aorta

What is elastic rebound

Due to the elasticity the aorta snaps back on itself

Is the process of listening to the sounds of the heart using a stethoscope. The sounds are created by the closing of the AV and SL valves. The sounds are described as Lubb dupp

Auscultation

The first heart sound, the Lubb, is produced by the closure of the _____ valves during ________?

AV Ventricular systole

The second heart sound, the dupp, is produced by the closure of the _____ during ____?

SL Ventricular diastole

What is regurgitation?

Backward flow of blood

What is a heart murmur

Swishing or whispering sound heard due to improper closure of a valve

Complete failure of mitral vale

Mitral valve prolapse

Although the heart is auto rhythmic and can beat without any hormonal or neural stimulation, the rate of the heartbeat must be sped up or slow down to meet the oxygen demand of the bodies tissues

Cardiodynamics

Is the study of the mechanics and abilities of the heart to alter the volume of blood being pumped to tissues to meet these changing demands

Cardiodynamics

The volume of blood pumped by the heart over a period of time

Cardiac output

Volume of blood pump by the heart in one beat

Stroke volume

The number of heartbeats per minute

Heart rate

Is maximum CO - resting CO, or up to around 24 L for a normal individual

Cardiac reserve

The normal heart rate is called the resting heart rate, which is sent by the natural cardiac pacemaker, the SA node . Resting heart rate for the average adult is between

70-80 bpm

The heart is innervated by the nerves of the

ANS

Innvervation is by way of a few cervical and thoracic nerves which from the cardiac plexus

Sympathetic innervation

Sympathetic neurons synapse on the nodes of the heart and release a hormone

Norepinephrine

A few lumbar nerves synapse on the adrenal medulla and cause it to release high levels of _____ into the bloodstream which result in a sympathetic effect for a prolonged period of time

NE is the flight or fight hormone and it will increase heart rate and force contraction therefore increasing SV, which will increase

Cardiac output

Cardio sites of the essay and AV node will increase their permeability to

Cardiocytes of the SA and AV node will increase their permeability to NA+ when ____ is present, causing them to depolarize more rapidly

NE also increases the permeability of Cardiocytes to

CA2+

Ca2+ will increase the force and duration of the contraction, which increases

SV and CO

Parasympathetic innervation is from cranial nerve

Cranial nerve 10 the vagus nerve

The vagus nerve synapses directly on the SA and AV nodes and releases the neurotransmitter

Acetylcholine ACH

The parasympathetic system is a rest and digest system and heart rate decreasing

Cardiac output

In the presence of ACH, Cardiocytes of the SA and AV nodes will increase their permeability to ______, causing them to depolarize more slowly and with less force.

K+ potassium

The ______ of the brain contains the control centers for cardiac function

Medulla

Cardiac acceleratory

ANS = Sympathetic Neurotransmitter = NE Affect on HR = increases

Cardio inhibitory

ANS = PNS Neurotransmitter = ACH Affect on HR = slow

There are __________ in the walls of the atria, carotid arteries, and the aortic artery

Pressure and baroreceptors

The ______ adjusts the heart rate in response to increases in venous return

Atrial reflex

Several hormones can affect heart rate, including

Norepinephrine Epinephrine Thyroid hormone Atrial natriuretic peptide ANP