Chapter 11
Nervous System and Nervous Tissue

Functions of the nervous system – The nervous system is the master controlling and communicating system of the body.

Sensory input - gathered information of sensory receptors, used by the Nervous System to monitor changes occurring both inside and outside the body.

Integration - this is when the nervous system processes and interprets sensory output. As well as decides what should be done at each moment.

Motor output - response caused by the Nervous System, by activating Effector Organs (muscles & glands).

Organization of the nervous system

Central nervous system (CNS) – consists of the brain and spinal cord, it is the integrating and command center of the Nervous System. It receives sensory input and dictates a motor response.

Peripheral nervous system (PNS) - part of the Nervous System, outside of the CNS, it consists of nerves (bundles of axons) that extend from the brain and spinal cord. Includes spinal and cranial nerves, the afferent and efferent division.

Sensory (afferent) division – carrying toward, consists of nerve fibers (axons) that convey impulses to the CNS from sensory receptors throughout the body. Somatic afferent fibers conduct impulses from skin, skeletal and joints. Visceral afferent fibers transmit impulses from visceral organs(organs in ventral body cavity).

Motor (efferent) division – carrying away, transmits impulses from the CNS to Effector organs, which are the muscles and glands. These impulses activate muscles to contract and glands to secrete (causes a motor response). Is it also divided into Somatic and Automatic divisions.

Somatic (voluntary) nervous system – conducts impulses from the CNS to skeletal muscles, it is known as the voluntary nervous system because it allows us to consciously control muscle movements.

Autonomic (involuntary) nervous system (ANS) – consists of visceral motor nerve fibers that regulate the activity of smooth muscles, cardiac muscles, and glands. It is also subdivided into parasympathetic and sympathetic.

Sympathetic division – Mobilizes body resources or systems during activity or under stress.

Parasympathetic division - its job is to Conserves energy. Promotes housekeeping functions during rest. Including salivation, urination, digestion, and defecation causing a fight or flight response.

Cells of nervous tissue - Nervous tissue is made up of two principle types of cells: 1. Supporting cells called neuroglia, smaller cells that surround and wrap the more delicate neurons, and 2. Neurons, the excitable nerve cells that transmit electrical signals.

Neuroglia - or simply glial cells. There are 6 types of neuroglia- 4 in the CNS and 2 in the PNS. These cells provide supporting scaffolding for neurons. Some produce chemicals that guide young neurons to the proper connections, and promote neuron health and growth. Others wrap around and insulate neuronal processes to speed up action potential conduction.

Neuroglia of the CNS - Includes astrocytes, microglia, ependymal cells, and Oligodendrocytes. Most glial cells have branching processes and a central cell body. Neuroglia can be distinguished, however, by their much smaller size and by their darker- staining nuclei. They outnumber neurons in the CNS by about 10-1, and make up about half the mass of the brain. Astrocytes - most about and versatile glial cell..

Structure - star shaped that look like branching sea anemones. They are connected together by gap junctions and signal to each other both by taking in calcium and releasing chemical messengers.
Function- (1)support and embrace neurons and anchor them to their nutrient supply line, which is the capillary. The numerous radiating processes cling to the neurons and capillaries. (2)They control the chemical environment around neurons. Pick up (mop), leaked potassium ions and neurotransmitters to help recycle them. (3) They also influence the neuronal