Heart and Blood Vessel Physiology

Question 1

Where is the heart?

Answer 1

In the mediastinum between 3rd and 4th rib

Question 2

What are desmosomes?

Answer 2

Intercolated discs that keep muscle cells together and uniform

Question 3

Why is it important for the heart to have gap junctions?

Answer 3

Ions can pass more quickly from cell to cell, making depolarization faster

Question 4

Why is the left wall of the heart thicker?

Answer 4

It needs to generate greater contractive force for higher pressure in vessels

Question 5

True or False: Blood requires a lot of ATP to move throughout the body

Answer 5

False. Blood requires bo energy to move throughout the body. It follows pressure gradients

Question 6

True or False: The right side of the body and left side pump equal amounts of blood.

Answer 6

True

Question 7

On average, how much blood does the human body contain and how often is it circulated through the body?

Answer 7

5L; once a minute

Question 8

What are the two kinds of myocardial cells?

Answer 8

Contractile (99%) and Autorhythmic

Question 9

Describe autorhythmic cells

Answer 9

1% of myocardial cells
Able to generate APs spontaneously
Found in nodes, bundles, and fibers
Never rest (reach -70mV), go to about -60mV via slow depolarization due to leaky Na+ channels

Question 10

Describe the electrical activity of contractile cells

Answer 10

Rest at -90mV and remain at constant membrane potential for a long time in a plateau phase because voltage-gated Ca2+ channels stay open

Question 11

Are cardiac action potentials voluntary or involuntary?

Answer 11

Involuntary

Question 12

How does the absolute refractory period of the heart compare to skeletal muscles? Why is this significant?

Answer 12

The heart has a relatively long refractory period, which allows it to relax, lower pressure, and allow blood back into it

Question 13

What is the intrinsic conduction system?

Answer 13

Siniatrial Node (SA), 70-75bpm
Atrioventircular Node (AV) 50bpm
AV bundle (intraventricular space) 35bpm
-Goes left to right
Bundle Branches
Purkinje Fibers (30bpm)
Individual fibers can generate their own rhythm as a last resort

Question 14

What is arrhythmia?

Answer 14

An irregular heartbeat

Question 15

What is fibrillation?

Answer 15

Rapid irregular contractions, which are useless for pumping blood

Question 16

What is the pacemaker of the heart?

Answer 16

The Sinoatrial Node

Question 17

What happens if the SA node fails?

Answer 17

Ecoptic focus: the AV takes over and the heart assumes slowed junctional rhythm

Question 18

What happens if the AV node is defective?

Answer 18

Heart block

Question 19

What is tachycardia?

Answer 19

An abnormally fast heartrate (more than 100bpm)

Question 20

What is bradycardia?

Answer 20

An abnormally slow heartrate (less than 60bpm)

Note: This is desirable result of endurance training

Question 21

What’s ectopic focus?

Answer 21

Abnormally excitable areas depolarize faster than the SA node (can lead to accelerated heartrate)

Question 22

What is the difference between systole and diastole?

Answer 22

Systole: Contraction
Diastole: Relaxation

Question 23

When does ventricular filling occur?

Answer 23

Mid to late diastole, when ventricles are relaxes and AV valves are open

Question 24

What is EDV?

Answer 24

End Diastolic Volume: The blood left in the ventricle after diastole, about 20% of capacity

Question 25

When do Ventricular Systole and Atrial Diastole take place?

Answer 25

At the same time.

Question 26

What causes AV valves to close?

Answer 26

Rising ventricular pressure during systole exceeding atrial pressure

Question 27

What is true about valves during the isovolumetric phase?

Answer 27

They are closed

Question 28

What causes the semilunar valves to open?

Answer 28

Ventricular pressure exceeds pressure in the large arteries during "Ejection Phase"

Question 29

What is ESV?

Answer 29

End Systolic Volume - Blood remaining in ventricles at end of ejection phase

Question 30

What causes a dicrotic notch?

Answer 30

Backflow of blood in aorta and pulmonary trunk when SL valves close

Question 31

What are the heart sounds and when do they occur?

Answer 31

Lub - When AV valves close, beginning of systole Dubb - When SL valves close, beginning of diastole

Question 32

What are heart murmurs and what do they indicate?

Answer 32

Abnormal heart sounds -- most often indicate valve problems

Question 33

What is Cardiac Output (CO)?

Answer 33

Heart Rate x Stroke Volume (xxx bpm) x (70mL/beat)

Question 34

What is the cardiac reserve?

Answer 34

The difference between resting and maximal CO

Question 35

What are the effects of the SNS on heartrate?

Answer 35

Hormones & Autonomic Innervation -Emotional or Physical stressors activate -NE causes pacemaker to fire more rapidly -Epinephrine depolarizes autor. cells and increases contractility and HR -Positive cronotropy -Thyroxine enhances effects of NE/Ep

Question 36

What are the effects of the PSNS on Heart Rate

Answer 36

ACh hyperpolarizes pacemaker cells by opening ligand-gated K+ channels Negative cronotropy

Question 37

What is Starling's Law?

Answer 37

The heart will pump out whatever volume is pumped in

Question 38

What are the factors affecting stroke volume?

Answer 38

Preload Contractility Afterload

Question 39

What is "Preload"?

Answer 39

Ventricular stretching during diastole, specifically the degree of stretch of cardiac muscle cells before they contract

Question 40

True or False: At rest cardiac muscles are shorter than optimal length

Answer 40

True

Question 41

What is contractility?

Answer 41

The force produced during contraction at a given preload The contractile strength at a given muscle length independent of muscle stretch and EDV

Question 42

What can increase contractility?

Answer 42

Increased Ca2+ Hormones (thyroxine, glucagon, epinephrine)

Question 43

What can decrease contractility?

Answer 43

Negative intropic agents Acidosis Extracellular K+ Ca2+ blockers

Question 44

What is afterload?

Answer 44

Blood pressure in major arteries which must be overcome to eject blood from heart

Question 45

What effect does hypertension have on Stroke Volume?

Answer 45

Increases afterload, decreasing stoke volume

Question 46

What are the results of increased venous return?

Answer 46

Distended ventricles, therefore increased contraction force, therefore increased Stroke Volume

Question 47

What is the Bainbridge Reflex?

Answer 47

Atrial walls stretch and stimulate SA node and atrial stretch receptors

Question 48

What factors affect heart rate?

Answer 48

Age, Sex, Exercise, Body Temp

Question 49

True or False: The heart can only use glucose as an energy source?

Answer 49

False, it is adaptable to a number of food sources including fatty acids and lactic acid

Question 50

What is Congestive Heart Failure?

Answer 50

A progressive condition where cardiac output is so low that circulation is inadequate for tissue needs

Question 51

What are some possible causes of Congestive Heart Failure?

Answer 51

Coronary Atherosclerosis Persistent Hypertension Multiple Myocardial Infarctions Dilated Cardiomyopathy

Question 52

True or false: arteries have thicker muscle, veins have a wider diameter

Answer 52

True

Question 53

True or False: The wider the diameter if a blood vessel the faster the flow

Answer 53

True

Question 54

Where are the elastic arteries, why are they important?

Answer 54

Nearer to the heart, can expand as heart expels blood, accommodating for pressure changes

Question 55

What is tissue perfusion?

Answer 55

Blood flow. Rate of flow is important to provide proper function: Important for delivery of O2, removal of waste, absorption of nutrients, urine formation

Question 56

True or False: Blood travels at a rate inverse to the total cross-sectional area?

Answer 56

True. (Wider/Bigger = Faster)

Question 57

What is blood flow?

Answer 57

The volume in a vessel organ or system during a given period, measured in ml/min Equivalent to the total cardiac output of the entire vascular system

Question 58

How is blood flow calculated?

Answer 58

Flow Rate = deltaP/R As resistance increases flow rate decreases P - Pressure Gradient R - Vascular Resistance (opposition to flow through a vessel)