Chapter 6 - Nervous Tissue
Nervous system is specialized for the rapid communication of information from one region of the body to another.
Nervous system is divided anatomically into two major components:
- Central nervous system (CNS) – consists of the brain and spinal cord
- Peripheral nervous system (PNS) – peripheral nerves and ganglia
Nervous system is divided functionally into two major components:
- Somatic nervous system – conscious voluntary movements
- Autonomic nervous system – regulates the functions of internal organs - further divided into two subdivisions:
- Sympathetic nervous system – involved in functions requiring quick responses (i.e., stress, impending danger, and fight or flight response)
- Parasympathetic nervous system – regulates functions that do not require a quick response
Although the CNS will be briefly examined, most of the emphasize will be on the PNS.
The neuron is the structural and functional unit of the nervous system. However, non-neural cells (i.e., glial cells) provide support and protection in the CNS (oligodendrocytes, astrocytes, ependymal cells, and microglia) and the PNS (Schwann cells and satellite cells).
CENTRAL NERVOUS SYSTEM
The central nervous system (CNS) consists of the brain and the spinal cord.
Neurons have considerable variation in their size and shape. Because of the large size of human brains, the smaller rat brain is examined here.
The spinal cord functions primarily in the transmission of nerve signals between the brain and the body.
PERIPHERAL NERVOUS SYSTEM
The peripheral nervous system (PNS) consists of peripheral nerves and ganglia (clusters of nerve cell bodies).
Dorsal Root Ganglion
Dorsal root ganglia are clusters of nerve bodies of sensory neurons located alongside the spinal cord.
Sympathetic ganglia form long chains on either side of the spinal cord. They deliver information about stress, impending danger, and the fight-or-flight response.
Parasympathetic nerves have their nerve cell bodies in small ganglia located within the organ they innervate.
Peripheral nerves contain the axons of both motor neurons and sensory neurons that connect with the spinal cord. They are surrounded by multiple layers of connective tissue.
Sensory Nerve Endings
The nervous system has a variety of specialized receptors. Meissner and Pacinian corpuscles are two that can be readily seen by H&E.