11th Biology Chapter 18

– Neural System

Neurons are specialized cells that detect, receive, and transmit stimuli. Simple in lower invertebrates, neural systems are more developed in insects and vertebrates【4:1†source】.

– Human Neural System

Divided into the central neural system (CNS) and peripheral neural system (PNS). CNS consists of the brain and spinal cord for information processing, while the PNS includes nerves associated with the CNS. It is further divided into afferent and efferent fibers and somatic and autonomic neural systems【4:3†source】.

– Neuron as Structural and Functional Unit

Neurons are composed of a cell body, dendrites, and axon. Neurons can be classified based on the number of axons and dendrites (multipolar, bipolar, unipolar) and the presence of myelin sheath. Myelinated nerve fibers have Schwann cells enveloping the axon, while unmyelinated fibers lack this sheath【4:4†source】.

– Central Neural System

The brain is vital for voluntary movements, bodily balance, involuntary organ function, thermoregulation, hunger, thirst, and more. It is well-protected by the skull and divided into forebrain, midbrain, and hindbrain. The forebrain consists of the cerebrum, thalamus, and hypothalamus, with functions in sensory and motor signaling and hormone secretion【4:3†source】.