GIT-12. Which of the following is NOT a feature of smooth muscle cells in the external muscle layers (longitudinal and circumferential) of the intestines? They are connected together by gap junctions. They have spontaneous oscillations of membrane potential that each last for several seconds. They are innervated by both excitatory and inhibitory motor neurons. The motor neurons that excite them have cell bodies located in the spinal cord. They are electrically coupled to their neighbouring smooth muscle cells.
Answer (1)
To answer this question, let's discuss the key features of smooth muscle cells located in the external muscle layers (longitudinal and circumferential) of the intestines.
Connected by Gap Junctions: Smooth muscle cells are indeed connected by gap junctions, which allow ions and signaling molecules to pass directly from one cell to another. This connectivity is crucial for coordinated contractions known as peristalsis.
Spontaneous Oscillations of Membrane Potential: These oscillations, also called slow waves, are characteristic of smooth muscle cells. They help regulate the timing of contractions by providing a rhythmic pattern to the muscle's contractile activity.
Innervated by Both Excitatory and Inhibitory Motor Neurons: Yes, smooth muscle cells receive signals from both types of neurons. This dual innervation allows for greater control over muscle contraction and relaxation.
Motor Neurons Located in the Spinal Cord: This statement is NOT characteristic of the smooth muscle cells of the intestines. Instead, the motor neurons that innervate these muscles are part of the enteric nervous system and are primarily located within the walls of the intestines themselves, rather than having their cell bodies in the spinal cord.
Electrically Coupled to Neighbouring Cells: As with gap junctions, this electrical coupling ensures that the muscle cells work together harmoniously during contractions.
Based on the explanation of these features, the statement 'The motor neurons that excite them have cell bodies located in the spinal cord' is NOT a feature of the smooth muscle cells in the intestinal external muscle layers.
