The Nervous System

What are the 5 Basic Function of the Nervous System?

1. Initiation and regulation of movement

2. Regulating the endocrine system

3. Gathering information about internal and external environment

4. Maintain consciousness

5. Generating behaviors in response to survival

What is included in the CNS?

Brain and spinal cord

What is included in the peripheral nervous system (PNS)?

Cranial and spinal nerves going to and from the somatic (bodily) structures

Autonomic Nervous System (ANS)

The portion of the nervous system that coordinates activity of visceral structures (smooth muscle, cardiac muscle, and glands), has elements in both the CNS and PNS

Enteric Nervous System (ENS)

Partially autonomous collection of neurons contained within the walls of the GI tract which controls GI function locally and the activity of which is influenced by the autonomic nervous system, a subcategory of the PNS

Unipolar Neuron

Have one process and are seen only during development

Bipolar Neurons

Have one dendrite and one axon, common in sensory organs

Pseudounipolar Neurons

When neurone have their single dendrite and axon fused so as to give the appearance and function of a single process

Multipolar Neurons

Have a number of dendrites in addition to their single axon, most common type of neuron

Neuroglia/Glia

Supportive cells that can provide functions such as acting as immune cells, phagoctyosing cellular debris after trauma, regulating extracellular fluid environment, providing myelination of axons, etc.

Myelinated Nerve Fibers

Nerve fibers that are surrounded by a white sheath of fatty material (myelin)

Unmyleinated Nerve Fibers

Nerve fibers that are not directly exposed to the extracellular fluid but rather are simply invaginated into the cell membrane of an adjacent glial cell that the cells surrounds the axon

3 Gross Subdivisions of the Brain

Cerebrum, cerebellum, and brainstem

Meninges

Connective tissue coverings of the brain and spinal cord

3 Layers of Membranes Comprising Meninges

Pia mater (delicate inner layer), arachnoid (web-like middle layer filled with fluid that cushions the brain), dura meter (tough outer layer)

Purpose of the PNS

Convey sensory information to the brain and spinal cord to produce movement of muscle and secretion from glands via its motor nerves

Sympathetic Division of the ANS

Prepares the organism to meet a stress by producing a combination of physiological changes that increase available fuel molecules, blood flow to muscle, and cardiac output while simultaneously decreasing digestive processes

Parasympathetic Divison of the ANS

Parasympathetic activity leads to digestion and storage of fuel molecules and acts to bring the organism to a state of rest

Purpose of Myelin

It is a good insulator against ionic flows and can provide fast conduction of nerve impulses

Function of diameter in conduction velocities of axons

Large-diameter axons propagate action potentials at higher velocities than small-diameter axons because large axons have less internal resistance to the flow of current

Synapses

Specialized junctions where information is transmitted between neurons or between a neuron and the cell that it innervates

Electrical Synapses

Gap junctions between cell membranes of adjacent neurons that permit ionic exchange (less prevelant)

Synaptic Transmission

Neurotransmitters released by the pre-synaptic neuron must diffuse across the synaptic cleft to have their effect on post-synaptic cells

Gray Matter

Outsides of brain, inner portion of spinal cord, cerebral cortex, ganglia, etc.

White Matter

Inside of brain and outer part of spinal cord, funiculi, nerves, etc.

White Matter of the Spinal Cord

Can be divided into the dorsal and ventral horn

3 Tracts of the Spinal Column

Dorsal funiculus, lateral funiculus, and ventral funiculus

Function of the Spinal Cord Tracts

Ascending tracts carry sensory information whereas descending tracts carry motor commands