Nervous tissue forms the intricate communication network that governs the body’s functions. This specialized tissue is composed of two primary cell types: neurons and glial cells. Neurons are responsible for generating and transmitting electrical signals, facilitating rapid communication throughout the body. Glial cells, while not directly involved in signal transmission, provide essential support to neurons by maintaining their environment, assisting in signal conduction, and offering protection. Together, these cells enable the nervous system to control and coordinate all bodily activities, from conscious thought to involuntary reflexes.
Nervous Tissue in the Central Command Center
The central nervous system (CNS), comprising the brain and spinal cord, contains nervous tissue. Within these structures, nervous tissue is organized into distinct regions: grey matter and white matter. Grey matter primarily consists of neuron cell bodies, their dendrites, axon terminals, and synapses. This tissue is responsible for complex information processing, including thought, emotion, memory, and voluntary movement. In the brain, grey matter forms the outer layers, while in the spinal cord, it creates a butterfly-shaped core.
White matter, in contrast, is composed of bundles of myelinated axons, nerve fibers coated in a fatty insulation that speeds up electrical signal transmission. Its whitish appearance comes from this myelin sheath. White matter’s role is to connect different areas of grey matter and facilitate the rapid relay of nerve signals within the brain and between the brain and the spinal cord. In the brain, white matter is found beneath the grey surface, whereas in the spinal cord, it forms the outer layer surrounding the grey core.
Nervous Tissue Extending Throughout the Body
Beyond the central command center, nervous tissue extends throughout the body as the peripheral nervous system (PNS). This network of nerves branches out from the brain and spinal cord, reaching every limb and organ. The PNS acts as a relay system, carrying information between the CNS and the rest of the body.
The peripheral nervous system includes cranial nerves and spinal nerves. These nerves contain both sensory fibers that transmit information to the CNS and motor fibers that carry commands from the CNS to muscles and glands. Additionally, the PNS contains ganglia, which are clusters of neuron cell bodies located outside the brain and spinal cord. These ganglia serve as relay points, transmitting signals to control various functions, including muscle movement, glandular secretions, and organ activity.
Nervous Tissue in Sensory Organs
Specialized nervous tissue is found in the body’s sensory organs, detecting stimuli from the environment and within the body. These tissues convert external or internal signals into nerve impulses that the brain can interpret.
For vision, the retina in the eye is a light-sensitive layer composed of neurons, which convert light into electrical nerve signals. In the ear, the cochlea contains delicate hair cells that respond to vibrations, transforming them into nerve impulses for hearing. The vestibular apparatus detects head movements for balance.
The skin, a large sensory organ, is equipped with various nerve endings that detect touch, pressure, pain, and temperature. On the tongue, taste buds are clusters of nerve cells that detect chemical compounds. The nasal cavity houses olfactory receptors, which are specialized neurons that bind to odor molecules.