What is the function of the structure labelled X?

• permits passage of ions between cardiomyocytes

• anchors myosin fibers, similar to M

• connects thick filaments from adjacent

• allows coordinated contraction of adjacent cells

Which of the following statements best describes smooth muscle?

• forms fascicles that shorten unidirectionally

• innervated by somatic moro

• contracts due to myosin and actin interactions

• does not rely on calcium to initiate contraction

Cardiomyocytes obtained from a specific mouse embryo fail to contract following stimulation of cells at the opposite end of a chain. No abnormalities in cytoskeletal fibers are observed. A deficiency of which of the following would best explain this finding?

• gap junctions

• desmos

• adherens junctions

• tight junctions

A 28 year old male returns home from a trip to the tropical rain forests of Brazil complaining of headaches, fever, sensitivity to light and neck stiffness. Clinical examinations revealed encephalitis due to an acquired infection of the West Nile virus. When neural tissue is damaged, which resident neuroglial cell is responsible for phagocytosing cellular debris?

• oligodendrocytes

• ependymal

• microglial

• Purkinje cells

Which of the following best describes the relationship between Schwann cells and peripheral axons?

• one Schwann cell can myelinated mul

• one axon is myelinated by only one Schwann cell

• one Schwann cell engulf many unmyelinated a

• unmyelinated axons lack Schwann cells

The RMP of a myelinated neuron fiber is primarily dependent on the concentration gradient of which of the following ions?

• Ca2+

• K+

• Cl-

• Na+

If a resting myocardial cell membrane was altered to be relatively more permeable to sodium than to potassium or any other ion, then the resting membrane potential would be nearest to which of the following values?

• -96mV

• -70mV

• +52mV

• +134mV

If an experimental drug changed the RMP of a cell from -70mV to -50mV, what effect would this have on the rate of sodium and potassium diffusion across the cell membrane when the membrane is permeable to these electrolytes?

• increase sodium, increase potassium

• increase sodium, decrease potassium

• decrease sodium, increase potassium

• decrease sodium, decrease potassium

Considering the typical K+ concentration gradient across a neuronal membrane at rest, which of the following correctly describes the K+ flux and K+ conductance?

• influx, high conductance

• influx, low conductance

• influx, no conductance

• efflux, high conductance

A 32-year-old patient presents with severe diarrhea for 36 hours. He is dehydrated and hypokalemic. What effect will hypokalemia have on the K+ equilibrium potential and K+ RMP of the neuron?

• more negative Ek, more negative RMP

• more negative Ek, more positive RMP

• more positive Ek, more negative RMP

• more positive Ek, more positive RMP