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
Why is the composition of lymph different from that of blood?
A) Lymph is produced in the liver, while blood is produced in the heart
B) Lymph lacks red blood cells and large molecules because they are too big to pass through capillary walls
C) Lymph contains more oxygen than blood to supply tissues
D) Lymph is primarily composed of waste products, while blood is mainly nutrients
b)
What is hemolymph?
A) Fluid found in animals with a closed circulatory system and comes into direct contact with tissues
B) A type of fluid that circulates in the brain
C) A fluid in animals with an open circulatory system that contacts both vessels and tissues directly
D) A type of nutrient found in the liver
a)
How does hemolymph differ from blood?
A) Hemolymph only circulates through vessels, while blood contacts tissues
B) Hemolymph can contact both vessels and tissues, while blood is confined to vessels in closed circulatory systems
C) Hemolymph contains red blood cells, while blood does not
D) Hemolymph is oxygenated by the heart, while blood is not
b)
What is the primary difference in respiratory pigments in invertebrates vs vertebrates?
short answer
With invertebrates their respiratory pigments reside in the hemolymph whereas in vertebrates we have them in our RBCs.
What is the primary difference between hemolymph in invertebrates and blood in vertebrates?
A) Hemolymph contains hemocytes, while blood does not
B) Hemolymph contains respiratory pigments, while blood has carrier proteins like albumin and globulins
C) Blood lacks dissolved proteins, while hemolymph has them
D) Hemolymph has clotting proteins, while blood does not
B)
Which of the following is found in both blood and hemolymph?
A) Red blood cells only
B) Hemocytes and dissolved ions
C) Respiratory pigments in both vertebrates and invertebrates
D) Carrier proteins in both vertebrates and invertebrates
b) Hemocytes & dissolved ions
Which organisms have respiratory pigments circulating in their hemolymph instead of red blood cells?
A) Vertebrates
B) Invertebrates
C) Mammals
D) Fish
B) Invertebrates
What is the primary function of erythrocytes?
A) Nutrient transport
B) Waste removal
C) Oxygen transport
D) Hormone distribution
c) oxygen transport
Where are erythrocytes typically found in invertebrates?
A) In the hemolymph
B) In the interstitial fluid (ISF)
C) In the blood vessels
D) In the heart
b) within the ISF
