Circulatory System: Quiz 1 Material

Question 1

What is cardiac muscle?

Answer 1

muscle of the heart

Question 2

Name the 4 chambers of the heart.

Answer 2

Right ventricle, left ventricle, right atrium, left atrium

Question 3

What is the interventricular septum? What is it’s purpose?

Answer 3

-separates right and left ventricular chambers
-helps to stimulate chambers to cause contraction
-“muscle” on the sides of the ventricles

Question 4

What is the Myocardium? What regulates it?

Answer 4

-muscle of the heart
-regulated by the autonomic nervous system (ANS)

Question 5

What does the ANS change during ANS regulation of cardiac muscle? Which parts do what?

Answer 5

1. Heart rate; parasymp slows down, symp accelerates
2. Strength of muscle contraction; parasymp weakens only atria, symp strengthens both atria and ventricles

Question 6

What neurotransmitter is released from the Vagus Nerves?

Answer 6

Acetylcholine

Question 7

What neurotransmitter is released from the thoracic spinal nerves?

Answer 7

norepinephrine

Question 8

What are the two types of receptors located on the cardiac muscle?

Answer 8

muscarinic Ach Receptor
adrenergic receptors (beta 1)

Question 9

Describe the cellular structure of cardiac muscle

Answer 9

striations = sarcomeres
single nucleus
branched ends

Question 10

Where are intercalated disks located?

Answer 10

wherever one cardiac cell meets another

Question 11

Describe a Desmosome.

Answer 11

aka spot weld
Found on intercalated disk
used for stability, mechanism of attachment
protein-protein complex that spans cytosol

Question 12

Describe a Gap Junction.

Answer 12

aka electrical synapse
found on intercalated disk
1.5 nm channels
connect cytosol to cytosol so ions and small solutes can move from cell to cell

Question 13

What elements do all three types of muscle have?

Answer 13

sliding filaments and cross bridges, ATP powers the force generation, elevated cytosolic calcium initiates contraction

Question 14

How is Cardiac Muscle like Skeletal Muscle?

Answer 14

has sarcomeres
is striated
has troponin
has t-tubules
utilizes SR calcium

Question 15

How is Cardiac Muscle like Smooth Muscle?

Answer 15

has pacemaker cells
has gap junctions (syncytium)
uses calcium entry from ECF
autonomic/hormones modulate

Question 16

What is the difference between the way Dihyrdopyridine Receptors and Ryanodine receptors act in cardiac muscle vs skeletal muscle?

Answer 16

In cardiac muscle, the DHPR acts as a calcium channel rather than a voltage sensor as it does in skeletal

Question 17

What is the specific name for the calcium exchange that occurs in cardiac muscle?

Answer 17

CICR: calcium induce, calcium release

Question 18

Describe the amplification or “gain” of CICR.

Answer 18

1 calcium in through DHPR (aka trigger calcium)
results in 10 calcium released from SR through RyR

Gain = 10

Question 19

What causes the upstroke of the action potential of a contractile cardiac cell?

Answer 19

current from neighboring cell through gap junction, the rapid opening of voltage-gated sodium channels is responsible for the rapid depolarization phase

Question 20

What causes the prolonged plateau of contractile cardiac cells?

Answer 20

the prolonged plateau of depolarization is due to the slow but prolonged opening of voltage-gated calcium channels, called L-type(long-lasting) calcium channels (DHPRs)

trigger calcium enters through L-type channels

Question 21

What does the prolonged refractory period of cardiac muscle lead to?

Answer 21

prevents tetanus, and allows time for ventricles to fill with blood prior to pumping

Question 22

What is the difference between cardiac muscle and skeletal muscle regarding summation of force?

Answer 22

skeletal muscles CAN summate force
cardiac muscles CANNOT summate force