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Chapter 13 Cardiac Function
Test 3
65
Physiology
Undergraduate 2
03/28/2010

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Cards

Term
3 Components of the Cardiovascular System
Definition

1. Heart Muscle

2. Blood Vessels

3. Blood

Term
Heart Muscle Functions
Definition
Pumps blood
Term
Blood vessels functions
Definition
conduit of blood flow
Term
blood function
Definition
carries gas and nutrients
Term
Where is the heart located?
Definition
Center of thoracic cavity, above diaphragm
Term
Size of heart?
Definition
size of fist, ~300 grams
Term
Pathway of Blood Flow through Heart
Definition
  • The Right Atrium, receives "used blood" from the body. Blood will be pushed through the tricuspid valve to the
  • Right Ventricle, the chamber which will pump to the lungs through the pulmonic valve to the
  • Pulmonary Arteries, providing blood to both lungs. Blood is circulated through the lungs where carbon dioxide is removed and oxygen added. It returns through the Pulmonary Veins, which empty into the
  • Left Atrium, a chamber which will push the Mitral Valve open. Blood then passes into the
Term

  What are the different types of vasculature (vessels)?  What is the function of each and what type of blood does each carry?

Definition

a.    Arteries-away from heart, usually high O2

b.    Veins-toward heart, usually low O2

c.    Capillaries-connecting arteries and veins, substances exchanged with body

*a closed system

Term
Why is blood flow unidirectional?  What features determine this?
Definition

Valves allow blood blow to be unidirectional. (from atria to ventricles and from heart to arteries) A septum separates L&R and allows no blood flow between them

Term

Why does the systemic circuit require more pressure (and resistance) compared to the pulmonary circuit?

Definition
systemic is more extensive and ventricular myocardium is thicker and stronger
Term

What is the direction of blood flow determined by?

 

Definition
gradients and valves
Term
Where do pressure gradients come from?
Definition
muscle contraction
Term
How do valves open/close?
Definition
IRT pressure gradients
Term
What is systole and diastole?
Definition

systole-heart contraction

diastole-heart relaxation

Term
Where do ventricles spend more time?
Definition
diastole
Term

Resting HR?

Heart beats every __sec?

diastole every __sec?

systole every __sec?

Definition

resting HR-72 bpm

heart beat every 0.8 sec

diastole ~ 0.5 sec

systole ~ 0.3 sec

Term
What is a prolapsed heartbeat?
Definition
When the cuspid is being pushed into the left atrium causing blood backflow.
Term
How does myocardium contract during a cardiac cycle?
Definition

Different regions contract at different times during heartbeat.

Both atria contract together, there is a slight pause, then contraction of ventricles.

Term
The Cardiac Pump Cycle
Definition

Phase 1: Ventricle Filling

Phase 2:Isovolumetric Contraction

Phase 3:Ventricular ejection

Phase 4:Isovolumetric relaxation

Term
Phase 1 of Cardiac Pump Cycle
Definition

Ventricle Filling

diastole

atria and ventricles fill, AVs open, SLs close

Lub sound

Term
Phase 2 of cardiac pump cycle
Definition

Isovolumetric contraction

systole

increased pressure, AVs and SLs are closed

Lub sound

Term
Phase 3 of cardiac pump cycle
Definition

ventricular ejection

systole

SLs open, blood ejected into pulmonary artery and aorta

dup sound

Term
phase 4 of cardiac pump cycle
Definition

isovolumetric relaxation

diastole

myocardium relaxes, SLs and AVs closed

Dup sound

Term
How do atrial, ventricular and aortic pressures vary during the cardiac cycle? 
Definition

pressure changes in atria and vent.

ventricles changes pressure most

Term
Aorta facts
Definition
  1. aorta is a pressure reservoir
  2. Aorta diastolic > ventricular diastolic
  3. aorta is elastic and very muscular
  4. blood flow is roughly constant, no spurts
Term
systolic pressure in (mmHg)
Definition
120 mm Hg
Term
diastolic pressure (mmHg)
Definition
80 mmHg
Term
Electrical properties of the heart
Definition
  • no external signals needed for contraction
  • originate from autorhythmic cells
  • contraction is myogenic, not neurogenic
Term
2 types of cells specialized for electrical coordination
Definition
  • make up cardiac conduction system
  • pacemaker cells
  • conduction fibers
Term
pacemaker cells
Definition
initiate APs and establish "autorhythmicity"
Term
Conduction fibers
Definition
transmit APs through the heart
Term
What 2 regions can pacemaker cells be found at?
Definition

sinoatrial node

 

atrioventricular node

 

*both generate APs spontaneously!

Term
What is the sequence of events in conduction of electrical activity through the heart? 
Definition
  1.                                    .    SA node fires, AP passes through atria
  2.                                         AV node transmits AP after slight delay
  3.                                       AV bundle (bundle of His) conducts through ventricular septum to apex.
  4.                                         Right and left bundle branches
  5.                                          Purkinje fibers spread AP upward into ventricular myocardium
Term
How are cardiac myocytes joined?
Definition

By gap junctions and desmosomes.

They are concentrated between myocytes at intercalated discs.

Term
Gap junction
Definition
spread of APs through adjacent cells
Term
desmosomes
Definition
strong protein anchors
Term
What pacemaker depolarizes fastest?
Definition
SA pacemaker
Term
How do pacemakers work?
Definition
  • 1st, SA node depolarizes spontaneously (70 bpm)
  • Then, AV node can depolarize spontaneously (50 bpm), but is pre-emptied by SA node
  • If the SA node fails to fire or there is a conduction block:AV node can initiate AP
  • Last, Purkinje fibers fire at 30 - 40 bpm
Term
Describe the ionic basis pacemaker AP
Definition
There is no resting membrane potential, so APs keep firing spontaneously
Term
Contractile Cell Action Potential Process
Definition

0. Na+ influx through VGSCs

1. Na+ influx stops, Ca2+ influx rises, through VGCCs

2. Ca2+ influx through VGCCs

3. VGCCs shut off, K+ channels open

4. Resting state - K+ permeability

 

*have stable resting potentials

Term
Excitation contraction coupling
Definition
  • influx of Ca2+ from ECF --> Ca2+ release from SR
  • Ca2+ - induced Ca2+ release
  • Actin-myosin interactions (like skeletal muscle)
  • contraction ceases when Ca2+ is removed
Term

What is an ECG?

How does it work?

Definition
An ECG is the measure of heart electrical activity. Synchronized activity generates large amplitude APs which are detected at skin surface. Distinct phases at cardiac cycle correspond to distinct electrical waveforms.
Term
3 Waveforms of an ECG
Definition
  1. P wave-atrial depolarization
  2. QRS complex-ventricular depolarization
  3. T wave-ventricular repolarization
Term
Isoelectric line
Definition
a part of an ECG with no electrical activity
Term

Cardiac Arrhythmias

  1. what is it?
  2. how is it recorded?
  3. does an ecg reveal it?
Definition
  1. abnormal electrical activity
  2. recorded as altered time intervals between waveforms and/or altered waveforms
  3. ECG does not reveal mechanical problems (ie bad valves)
Term
Abnormal SA node firing
Definition

leads to altered heart rate

 

too fast - >100 bpm

too slow - <50 bpm

Term

AV conduction block

(degrees)

Definition

1st degree-AV node fires slow, delayed

2nd degree-AV sometimes doesn't fire

3rd degree-no conduction through AV node, ventricles contract IRT Purkinje fibers discharge (30-40 bpm)

Term
Pre mature atrial contraction
Definition
contraction IRT AP outside of conduction pathway--extra systole
Term
Ventricular fibrilation
Definition

Ventricular myocardium contracts in uncoordinated fashion

(difibrilate)

Term
What is stroke volume?
Definition
the amount of blood ejected from ventricle
Term
End diastolic volume (EDV)
Definition
maximum blood volume in ventricle, just before start of ejection
Term
End Systolic Volume (ESV)
Definition
minimum volume of blood in ventricle, just after ejection
Term
How do you calculate stroke volume?
Definition

SV=EDV-ESV

70=130-60

Term
Ejection Fraction
Definition
indicator of heart pumping efficiency
Term
How do you calculate ejection fraction?
Definition

EF=SV/EDV

TYPICAL: EF=70 mL/130mL = 0.54

Term
What does low ejection fraction indicate?
Definition
Low EF indicates weak ventricle contraction
Term

What does Cardiac Output reveal?

What causes change in CO?

 

Definition

CO reveals an industrious organ!

change in HR or SV changes CO

Term
How do you calculate Cardiac Output?
Definition

CO=HR x SV

CO= 72 bpm x 0.07 L/beat = 5 L/min

Term
What are the two extrinsic control mechanisms for the heart?
Definition
  1. neural control
  2. hormonal control
Term
Neural Control of heart
Definition

*extrinsic

autonomic nervous system, through NTs ACh and NE

Term
Parasympathetic Effects on Heart
Definition
  • Vagus control of nodes
  • cholinergic
  • decreases node firing
  • slow HR
  • mACh
  • ACh
  • SA and AV
Term
Sympathetic effects on Heart
Definition

SA, AV, ventricular myocardium

NE:increases node firing and contraction strength

B1

increases HR and SV

innervate nodes and atrial and ventricular myocardium

 

Term
Hormonal Control of Heart
Definition
Secretion of epinephrine by adrenal medulla increases node firing and ventricular contraction. (action is similar to NE)
Term

Why is it advantageous for the systemic circuit to be arranged in parallel capillary beds?

Definition

If you arrange the vessels in parallel, such that each organ has its own artery, every organ gets its own blood supply and does not have to wait in line, and organs can regulate their own blood flow based on need.

Term
Heart Anatomy
Definition
[image]
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