Final answer:
The nervous system consists of afferent fibers, which are sensory pathways carrying signals toward the CNS, and efferent fibers, which are motor pathways that carry signals away from the CNS to muscles or glands. The somatic nervous system is associated with voluntary movements, while the autonomic nervous system manages involuntary actions. The structure of reflex pathways differs between these systems.
Step-by-step explanation:
When discussing the structure of the nervous system, afferent fibers refer to sensory pathways that carry information toward the Central Nervous System (CNS), while efferent fibers are motor pathways that carry information away from the CNS to the rest of the body.
The term 'afferent' implies 'arriving' or 'moving toward,' and includes sensory neurons that carry signals from sensory receptors toward the CNS. In contrast, 'efferent' implies 'exiting' or 'moving away from' and includes motor neurons that transmit signals from the CNS to activate muscles or glands.
The Peripheral Nervous System (PNS) comprises nerves and ganglia outside of the brain and spinal cord. It can be distinguished into the somatic nervous system, which controls voluntary movements through skeletal muscle contractions, and the autonomic nervous system, which regulates involuntary actions targeting cardiac and smooth muscle, as well as glandular tissue.
The somatic and autonomic systems share similar structures for their afferent branches, but differ in their efferent branches. A somatic reflex involves a direct motor neuron connection to the skeletal muscle, whereas an autonomic reflex utilizes a two-step pathway with preganglionic and postganglionic fibers reaching the target effector.