Lecture 3: Controlling contraction

Question 1

What does it mean for vertebrate hearts to be myogenic?
a) They require nervous system input to function.
b) They generate their own rhythmic contractions.
c) They have a single chamber.
d) They do not contain muscle tissue.

Answer 1

b)

Question 2

How do cardiomyocytes communicate with each other?
a) Through chemical signals only
b) Through gap junctions
c) Through direct nerve connections
d) They do not communicate

Answer 2

b) gap junctions

Question 3

What are desmosomes?
a) Specialized nerve cells
b) Structures that provide electrical insulation
c) Fibers that mechanically connect cardiomyocytes
d) Proteins that facilitate ion transport

Answer 3

c) fibers that connect heart cells together

Question 3

What is the primary function of pacemaker cells in the heart?
a) To generate the highest blood pressure
b) To produce hormones that regulate heart rate
c) To initiate and coordinate heart contractions
d) To provide structural support to the heart

Answer 3

c)

Question 3

In which part of the heart are pacemaker cells found in most other vertebrates?
a) Atrioventricular (AV) node
b) Right ventricle
c) Sinoatrial (SA) node
d) Pulmonary artery

Answer 3

c) SA node

Question 3

Where are pacemaker cells located in fish?
a) In the right atrium
b) In the sinoatrial (SA) node
c) In the sinus venosus
d) In the ventricular myocardium

Answer 3

c) sinus venosus

Question 4

Why is there a delay in depolarization at the AV node?
a) The SA node is not functioning properly.
b) The AV node has fewer gap junctions than the atrial cardiomyocytes
c) due to layer of fibrous connective tissue seperating the atria and ventricles

Answer 4

b)

Question 4

Explain the intiation of depolarization during a heartbeat

Short answer

Answer 4

1. depolarization begins in the SA node and spreads through the atrial muscle
2. depolarization reaches AV node but there is a slight delay b/c we wait for the atria to finish contracting. Ventricles then fill with blood.
3. signal travels down along bundle of HIS and splits into the L and R bundle branches
4. ventricles contract pushing blood out of the heart

Question 5

What does tachycardia refer to?
a) A normal heart rate
b) A heart rate lower than normal
c) A heart rate higher than normal
d) An irregular heart rhythm

Answer 5

c

Question 6

Which of the following describes sinus rhythm?
a) Normal heart rhythm
b) A rapid heart rate
c) A heart rate that is too slow
d) An irregular heart rate

Answer 6

a) normal heart rythm

Question 7

What type of rhythm is indicated by the term “arrhythmia”?
a) Consistent heart rhythm
b) Abnormal heart rhythm
c) Normal heart rate
d) Decreased heart rate

Answer 7

b) abnormal heart rhythm

Question 8

What electrical activity does an ECG record?
a) Only atrial activity
b) Only ventricular activity
c) Both atrial and ventricular activity
d) Blood flow through the heart

Answer 8

c) both

Question 9

What characterizes atrial fibrillation?
a) Presence of P waves
b) Absence of P waves
c) Absence of QRS complexes
d) Regular heart rhythm

Answer 9

b)

Question 10

In which condition is there no QRS complex observed on an ECG?
a) Atrial fibrillation
b) Ventricular fibrillation
c) AV block
d) Normal sinus rhythm

Answer 10

b)

Question 11

What does the absence of P waves indicate?
a) Normal atrial depolarization
b) Disturbed atrial conduction
c) Healthy ventricular function
d) Effective communication between atria and ventricles

Answer 11

b)

Question 12

What happens in ventricular fibrillation?
a) Atrial contraction is regular.
b) The ventricles are unable to contract effectively and dissociated rythmn b/t atria and ventricles
c) The P and QRS complexes are in sync.
d) There is an increase in heart rate.

Answer 12

b)

Question 13

What is a key feature of AV block?
a) Normal heart rhythm
b) Synchronized P waves and QRS complexes
c) Impaired communication between atria and ventricles
d) Increased ventricular rate

Answer 13

c)

Question 14

What is the consequence of dissociated rhythm between ventricles and atria?
a) Effective blood flow
b) Enhanced cardiac output
c) Ineffective pumping of blood
d) Increased oxygen delivery to tissues

Answer 14

c)

Question 15

What effect does the sympathetic nervous system have on heart rate?
a) Decreases heart rate
b) Increases heart rate
c) Has no effect on heart rate
d) Only affects the ventricles

Answer 15

b)

Question 16

What is the role of the parasympathetic nervous system in heart function?
a) Increases force of contraction
b) Decreases heart rate
c) Increases heart rate
d) Stimulates the SA node

Answer 16

b)

Question 17

Which hormone is released from the adrenal glands to increase heart rate?
a) Norepinephrine
b) Cortisol
c) Epinephrine
d) Insulin

Answer 17

c)

Question 18

Which of the following best describes the difference between intrinsic and extrinsic control of the heart?

a) Intrinsic control involves external stimuli, while extrinsic control originates from within the heart.
b) Intrinsic control is regulated by the nervous system, while extrinsic control is regulated by the heart’s pacemaker.
c) Intrinsic control includes the activity of the SA node, while extrinsic control involves the effects of the sympathetic nervous system.
d) Both intrinsic and extrinsic controls are influenced by hormonal signals only.

Answer 18

c)

Question 19

Which of the following involve intrinsic control of the heart ?
a) hormones
b) Nervous system
c) Frank-Starling mechanism
d) Pacemaker cells
e) All of the above
f) c and d
g) a and d

Answer 19

f) C and D

Question 20

Which ion is found in higher concentration inside the pacemaker cells?
a) Sodium (Na+)
b) Calcium (Ca²+)
c) Potassium (K+)
d) Chloride (Cl-)

Answer 20

c)

Question 21

What happens during depolarization of pacemaker cells?
a) The inside of the cell becomes more negative.
b) Positive charges enter the cell, making it less negative.
c) The action potential is completely inhibited.
d) Only potassium ions move out of the cell.

Answer 21

b)

Question 22

What is the initial phase of depolarization in pacemaker cells called?
a) Resting potential
b) Action potential
c) Pacemaker potential
d) Hyperpolarization

Answer 22

c) Pacemaker potential

Question 23

What type of channels primarily allow ions to move in and out of pacemaker cells?
a) Mechanically gated channels
b) Ligand-gated channels
c) Voltage-gated channels
d) Leakage channels

Answer 23

c)