Lecture 4: Contraction and Circulation Flashcards
What causes the pacemaker potential in sinoatrial (SA) node cells to drift upwards toward the threshold?
A) Potassium efflux
B) Sodium influx through “funny” channels
C) Calcium influx
D) Chloride influx
B)
What ion is primarily responsible for the depolarization phase of the action potential in pacemaker cells?
A) Sodium
B) Potassium
C) Calcium
D) Chloride
c) calcium
Which of the following phases is NOT present in the electrical activity of pacemaker cells?
A) Depolarization
B) Repolarization
C) Plateau phase
D) Pacemaker potential
c) Plateau phase
What ion is responsible for the repolarization phase in both pacemaker cells and cardiomyocytes?
A) Sodium
B) Potassium
C) Calcium
D) Chloride
b) potassium
Which type of cells have a stable resting membrane potential of approximately -90 mV?
A) Pacemaker cells
B) Cardiomyocytes
C) Neurons
D) Smooth muscle cells
b) cardiomyocytes
What triggers the action potential in cardiomyocytes?
A) Sodium influx through funny channels
B) Signals from neighboring cells via gap junctions
C) Calcium influx
D) Potassium efflux
b)
What is the primary role of calcium ions during the plateau phase in cardiomyocytes?
A) To cause depolarization
B) To prolong the action potential
C) To repolarize the membrane
D) To initiate the pacemaker potential
B) to prolong the action potential (contraction)
Why is the plateau phase important in cardiomyocytes?
A) It prevents sodium from entering the cell
B) It allows early repolarization
C) It prevents another action potential from happening too quickly, allowing sufficient contraction time
D) It stabilizes the resting membrane potential
c)
Where are “funny” channels located, and what do they do?
Short answer
“Funny” channels are located in pacemaker cells (such as in the sinoatrial node). They allow the slow influx of sodium (Na⁺), causing the membrane potential to drift upwards toward the threshold.
Why does the pacemaker potential drift upward rather than staying flat?
The pacemaker potential drifts upward due to the slow influx of sodium (Na⁺) through “funny” channels, which gradually depolarizes the membrane until it reaches the threshold for an action potential.
Why do unicellular organisms and small metazoans lack circulatory systems?
short answer
Unicellular organisms and small metazoans are small enough that diffusion is sufficient for gas exchange and nutrient distribution, eliminating the need for a circulatory system.
Why can small animals rely on simple gas exchange methods, while larger animals cannot?
Small animals have a high surface-area-to-volume ratio, allowing simple diffusion of gases across their surfaces. Larger animals require bulk flow or convective transport to move fluids and gases efficiently throughout their body.
What is interstitial fluid?
A) Fluid within blood vessels
B) Fluid that surrounds cells in tissues
C) Fluid in the lymphatic system
D) Fluid within the mitochondria
b)
Which of the following describes blood?
A) Fluid that circulates in an open circulatory system
B) Fluid that circulates within vessels of a closed circulatory system
C) Fluid that bathes tissues directly
D) Fluid that contains no large molecules
b)
Why don’t red blood cells leak out of capillaries?
A) Red blood cells are too small
B) Red blood cells are too large to pass through capillary walls
C) Red blood cells diffuse through capillaries but at a slower rate
D) Red blood cells actively move back into the bloodstream
b) RBCs are too large to pass through capillary walls
