Chapter 19: Heart

Question 0

Sinoatrial Node

Answer 0

• specialized cardiac muscle cell
• does not control
• job=pacemaker cells
• exhibit autorhythmicity

Question 1

How Action potential travels from SA Node through the heart:

Answer 1

1. Initiated in Sinoatrial node
2. Through gap junctions of cardiac atria
3. Action potential is slowed down by the
   Atrioventricular node
4. Bundle of HIS (AV bundle) & Purkinje fibers all
   have a larger diameter than cardiac muscle
   cells.*Action potential travels faster through the
   fibers than cardiac muscle cells
5. Contraction of the ventricles start at the apex
   of the heart

Question 2

Pacemaker of the heart:

Answer 2

Sinoatrial Node

Question 3

Autorhythmicity

Answer 3

Spontaneously depolarize & depolarize at regular intervels

Create a heart beat every .6 seconds =100 beats per minute

Question 4

Vagal Tone

Answer 4

Slowing of heart rate

Question 5

Normal resting heart rate is:

Answer 5

Constant signal through parasympathetic pathway to slow the heart

Question 6

Resting Membrane Potential

*(Pumps/voltage gated channels)

Answer 6

Na/k pump, Na leak, k leak

1) slow voltage gated Na channels
* open slowly
* narrow channel (Na flows slowly)

2) fast voltage gated calcium channels
3) voltage gated k channel

Question 7

EKG or ECG

Answer 7

Place electrodes on wrist, ankle, chest

Measures the electrical change in heart rate

Question 8

P Wave (pulse)

Answer 8

Atrial Depolarization

Question 9

QRS complex

Answer 9

Due to ventricular depolarization but also atrial repolarization

Question 10

T Wave

Answer 10

Ventricular repolarization

Question 11

PQ Segment

Answer 11

Atrial plateau

Question 12

ST segment

Answer 12

Ventricular plateau

Question 13

Cardiac cycle describes:

Answer 13

Order of events in turn of contraction, relaxation, valves opening/closing, & blood flow

Question 14

Diastole

Answer 14

Relaxation

Question 15

Systole

Answer 15

Contraction

Question 16

Valves open when:

Answer 16

Pressure in preceding (prior) chamber or vessel is greater than pressure in proceeding hollowing chamber or vessel.

Pressure keeps valve open/closed

Question 17

Cardiac cycle-1st stage

Answer 17

Heart completely relaxed after ventricular contraction

• start–> complete diastolic (at rest)
• after ventricular contraction blood flows into the right atrium from vena cavas
• blood flows into the left atrium from pulmonary veins

*left/right AV valves open because ventricles emptied;
pressure in filling atria > just contracted ventricles

• blood is flowing passively into ventricles because of open AV valve (no result of contraction)
• 70% of blood gets into ventricles through passive filling in AV Valve
• semilunar valves: closed because of pressure in ventricles is < the pressure in arteriol trunk (aorta & pulmonary arteries)

Question 18

Step 2: Atrial Systole

Answer 18

• during contraction of the atria (right after AP is Initiated in SA node)
• forcing blood into ventricles (vent almost full) through open AV valves
• semilunar valves still closed
• end of atrial systole; we have maximum amount of blood in ventricles (30% result of atrial contraction)

–most of us have around 130 ml of blood–

Question 19

End Diastolic Volume (EDV)

Answer 19

Maximum amount of blood in ventricles

Question 20

Step 3: Early Ventricular Systole

Answer 20

• Beginning of ventricular contraction-right after AP is initiated in the AV node
• travels into Purkinje fibers
• As soon as ventricles start contracting, some blood enters atria forcing AV valves to shut
• Semilunar valves are closed:
• -> because not generating enough pressure in ventricles to overcome the pressures in the arterial trunk

Isovolumetric Contraction is happening in ventricles

Question 21

Isovolumetric Contraction:

Answer 21

All valves are closed & no movement of blood during early ventricular systole

Question 22

Step 3: Late Ventricular Systole

Answer 22

• contraction of ventricles nearing end
• contracting ventricle created enough force to overcome pressure in arterial trunks
• semilunar valves open causing ventricular ejection
• AV valves remain closed. Pressure in Atria is < than contracting ventricles
• Blood leaves ventricles to the arterial trunks

Question 23

Stroke volume

Answer 23

Amount of blood in ventricular ejection

*about 70 ml

Question 24

End Systolic Volume

Answer 24

Blood left over | SV-EDV=ESV 130 ml-70ml=60 ml

Question 25

Step 4: Early Ventricular Diastole

Answer 25

* After contraction of ventricles,beginning of relaxation of ventricles * AV valves closed * Pressure in atria is < than pressure in ventricles * Semilunar valves closed - -> because pressure outside of semilunar > than that in ventricles

Question 26

Step 5: Late Ventricular Diastole

Answer 26

(Almost like step 1) * After contraction of ventricles * AV valves open. Pressure of the atria > than the pressure in ventricles * semilunar valve closed END OF CARDIAC CYCLE!

Question 27

Cardiac Output is measured by:

Answer 27

How efficient the heart is @ it's job of perfusion. *Perfusion: describes the amount of blood needed in certain areas of the body per minute

Question 28

Cardiac Output is described as:

Answer 28

The amount of blood that is ejected from ventricles per minute

Question 29

Cardiac Output Is determined by:

Answer 29

*SV (stroke volume) x HR (heart rate) Example of a person at rest: HR= 75 beats per min SV= 70 mL per beat 70 mL x 75 beats per min = 5.2 L per minute *CO explains why: - babies need faster resting HR because smaller heart. - Athletes have lower HR, heart more efficient

Question 30

Chronotropic Agents

Answer 30

Anything that affects HR

Question 31

Sympathetic stimulation of nodal cells (SA node):

Answer 31

1)NE releases from the medulla oblongota or adrenal glands 2) Your nodal cells have adrenergic receptors 3) NE binds to adrenergic receptor on nodal cells 4) Activate enzyme called adenylate cyclase 5)Adenylate cyclase speeds up: turning ATP into cAMP 6)cAMP is cofactor for protein kinase c (PKC) 7)PKC adds phosphate to volume gated Ca channels in nodal cells 8)Volume gated Ca channels open---> more Ca inside = faster AP generation

Question 32

Positive Chronotropic Agents:

Answer 32

* speed up HR * NE * caffeine (prevents breakdown of cAMP) *thyroid hormone: increase# of adrenergic receptors on nodal cells *cocaine (prevents breakdown of NE)

Question 33

Parasympathetic innervation:

Answer 33

*decrease rate of autorhymicity of nodal cells (SA nodes) * medulla oblongota during rest releases Ach * Ach binds to volume gated potassium channel * nodal cells even more--hyper polarized

Question 34

Negative Chronotropic Agents:

Answer 34

*Ach *Beta blockers (prevents stimulation of adrenergic receptors)

Question 35

Factors that effect Stroke Volume:

Answer 35

1) Venous Return 2) Inotropic Agents 3) Afterload

Question 36

Venous Return:

Answer 36

Filling of the atria A) Frank-Starling Law: as more blood fills the heart, more & more cross bridges formed during contraction (stronger contraction-->more ventricular ejectory-->longer stroke volume) B) During Exercise: 1.HR increases to improve cardiac output 2.skeletal muscles contracting bringing more blood to the heart C) Lower heart rate: 1. Allows more time to fill atria/ventricles ---more venous return= more stroke volume

Question 37

Frank-Starling law:

Answer 37

Frank-Starling Law: as more blood fills the heart, more & more cross bridges formed during contraction (stronger contraction-->more ventricular ejectory-->longer stroke volume)

Question 38

Inotropic Agents

Answer 38

(Hormones/chemical drugs that affect stroke volume)

Question 39

Positive Inotropic agents:

Answer 39

Increase calcium inside cardiac muscle cells 1) release of NE & E from the sympathetic response

Question 40

Negative inotropic Agents:

Answer 40

Decrease calcium inside cardiac muscle cells 1) electrolyte imbalances 2) some drugs

Question 41

Chronotropic vs. Inotropic cells

Answer 41

Chronotropic = nodal cells Inotropic = cardiac muscle cells

Question 42

Afterload:

Answer 42

Resistance in arteries to incoming blood * age * atherosclerosis