Answer:
The answer is B: All the muscle cells innervated by a single motor neurorn.
Explanation:
It is called a motor unit, all muscle fibers that are innervated by a motor neuron cell. A motor neuron cell can establish contact with up to 150 muscle fibrils, which when activated causes their simultaneous contraction, therefore, all the muscle fibers of a motor unit contract and relax at the same time.
Answer:
The correct answer is option A- oligodendrocytes.
Explanation:
The insulation property of the neurons (axons) of the nervous system is provided by the fat-containing cells which wrap around the axons.
This wrapped structure is known as the "myelin sheath" in which fat provides the insulation to the neurons which increases the impulse conduction through neurons. The "oligodendrocytes" present in the CNS forms the myelin sheath which provides insulation to the neurons.
Thus, option A- oligodendrocytes are the correct answer.
Answer:
The answer to fill in the blanks, for this statement: The pharynx is the common passageway for food and air that leads into these two inferior structures: the esophagus and the larynx.
Explanation:
The pharynx, even though being a pretty simple structure of a tube that runs from both nose and mouth towards the throat and bifurcates into the esophagus and also the larynx, is one of the few organs that works both for feeding and also breathing. The pharynx is divided into three portions: the nasopharynx (the back of the nasal cavity), oropharynx (the back of the mouth) and the laryngopharynx. Because it is the only tube-like structure that leads both from the nose and from the mouth, it serves as the conducting system for both food and fluids, and air. When it reaches the neck, around the epiglotis, the pharynx transforms into the larynx, through which air passes towards the lungs. On the other side, the pharynx gives way to the esophagus, which is the main conducting system for food and fluids.
