Chapter 11 Cardiovascular System, The Heart Part 2

Question 1

Where will blood flow immediately after the right ventricle?

A. Right atria
B. Left atria
C. Aorta
D. Right ventricle

This blood is oxygen-___________.
A. rich
B. poor

Answer 1

B. Left Atria

A. Rich

Question 2

During changes of membrane potentials of SA node cells, what is occurring before threshold?

A. Potassium is leaking into the cells
B. A mechanical stimulus is causing a local potential
C. An action potential is initiated
D. Calcium is leaking into the cells
E. Sodium is leaking to the cells

Answer 2

D. Calcium is leaking into the cells

Question 3

What are the concepts of quantity/volume and pressure?

Answer 3

• For a fixed volume of fluid, pressure depends on the volume of the space it occupies
  
  • Large space = lower pressure
  • Small space = high pressure
  • As the size of the space changes, so does the pressure
  • Think of heart chambers as the space containing a fluid
• Pressure gradient
  
  • Differences in pressure between two pointsLike diffusion, substances flow from high pressure to low pressure
  • As the substances flows, pressure at the first point will decrease and pressure and the second point will increase
  • This is true, as long as the path is not blocked (THINK valves!)

Question 4

What happens to the volume of chambers and what must we consider?

Answer 4

• Volume of chambers change during a heartbeat
• We must also consider pressure in vessels
  
  • Elastic nature of vessels exert pressure on blood inside

Question 5

What is relaxation, contraction, and the cardiac cycle?

Answer 5

• Relaxation  Diastole
  
  • Space of the chamber increases
  • What happens to pressure? A – Increase, B - Decrease
• Contraction  Systole
  
  • Space of the chamber decreases
  • What happens to pressure?
• The Cardiac Cycle
  
  • One complete contraction and relaxation

Question 6

What happens in the Quiescent Period or Phase 1?

Answer 6

• Nothing is going on with the anatomy
• Anatomy - the atria and ventricles are relaxed
• Conduction - SA node cells are depolarizing (via leak cation channels)

Question 7

What happens during the atrial systole or Phase 2?

Answer 7

Anatomy - Atrial contraction, ventribles are relaxed

Conduction - SA node action potential

Question 8

What happens during the ISOvolumentric Contraction or Phase 3?

Answer 8

Anatomy - Atria relax ventricles contract

Conduction - AV node deploarization (bundle of HIS) and Purkinge Fibers

Question 9

What happens during the Ventricular Ejection (phase 4)?

Answer 9

Anatoomy - ventricles are fully contracted

Conduction - AV nodes are depolarizing (Bundle of HIS) and purkinje fibers

Question 10

What happens in Isovolumetric relaxation (Phase 5)?

Answer 10

Anatomy - atria relaxed, ventricles begin to relax

Conduction - repolarization of AVnode, Bundle of HIS, Purkinje

Question 11

Which part of the conduction system is responsible for atrial systole?

A. Purkinje fibers
B. SA node
C. AV node
D. Bundle of His

Answer 11

B. SA node

Question 12

Which part of the conduction system is responsible for maximum ventricle contraction?

A. Purkinje fibers
B. SA node
C. AV node
D. Bundle of His

Answer 12

A. Purkinje fibers

Question 13

How do you get stroke volume?

Answer 13

End Diastolic Volume (EDV) – End Systolic Volume (ESV) =
Stroke Volume

Question 15

What is Cardiac Output and how do you get it?

Answer 15

• Cardiac output (CO) is the amount of blood pumped by the left ventricle in one minute
• Heart rate (beats/minute) X Stroke volume (mL/beat)

–HR x SV = CO

•Example:

–75 beats/minutes x 70 mL/beat = 5,250 mL/minute or 5 liters

–Humans have 4-6 liters total blood volume

–On average, the total blood volume is pumped through the heart per minute

–This is resting cardiac output

–During exercise, CO can be as high as 35 L/minute

Question 16

What is the Cardioacceleratory center and what does it do to affect heart rate?

Answer 16

• Cardioacceleratory center  Increase heart rate
  
  • Collection of cells in the medulla oblongata
• What type of neurons - Visceral motor (Sends info to the Brain/Organ rellated)
• Postganglionic neuron secretes norephinephrine (NE)
  
  • Adrenergic receptors on cells of the SA node bind NE
  • Cause an increase rate of ction potentials of SA node
• Maximum heart rate is 230 beats/minute
  
  • Limit of SA node excitation

Question 17

What is the Cardioinhibitory center and what does it do to affect heart rate?

Answer 17

• Cardioinhibitory center  Decrease heart rate
• Visceral motor neurons of the parasympathetic system
• Postganglionic neuron secretes acetylcholine (ACh)
  
  • Cholinergic receptors on cells of the SA node bind ACh
  • Allow potassium to leave the cell  hyperpolarizing reaction
  • Rate of action potentials decrease
• Normal heart rate is 70 beats/minute
  
  • Without nervous control the heart would beat about 100 beats/minutes

Question 18

What effects stroke volume?

Answer 18

• Preload and afterload
• Preload  Frank-Starling law of the heart
  
  • Stroke volume is proportional to final ventricular volume
  • If more blood is forced into the ventricle (during exercise), the ventricle stretches more
  • Results in a greater contraction
• Afterload  blood pressure in arteries
  
  • Higher blood pressure reduces the stroke volume
  • Hypertrophy of ventricles is indication of high blood pressure

Question 19

What information is integrated in deciding heart rate?

Answer 19

• Sensory input
• Proprioceptors
  
  • Inform brain of changes in physical activity
  • Increases heart rate before metabolic demand
• Baroceptors
  
  • Sense pressure in vessels
  • Pressure to high, lower heart rate
  • Pressure to low, increase heart rate
• Chemoreceptors
  
  • Sensitive to pH of blood
  • Important in respiratory system, but has some affect on heart rate
  • Too much carbon dioxide (waste), increase heart rate to remove