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Cuesta College-Human Anatomy (BIO 205)-Fall 2010-Dr. S. Sachs, Instructor

Central Nervous System

integrates and coordinates incoming and outgoing neural signals and carries our higher learning functions (thinking and learning)

Nucleus

collection of nerve cell bodies in the CNS

Gray Matter

unmyelinated axons, cell bodies, and dendrites; found in horns and commissures of spinal cord; surrounds ventricles, in cortex, in nuclei of brain

White Matter

The portions of the central nervous system that are abundant in axons rather than cell bodies of neurons. The colour derives from the presence of the axon's myelin sheaths

Horns

projections of gray matter toward the outer surface of the spinal cord

Meninges

three layers of connective tissue in which the brain and spinal cord are wrapped
-Pia
-Arachnoid
-Dura Mater

Peripheral Nervous System

-consists of nerve fibers and cell bodies outside the CNS that conduct impulses to or away from the CNS
-Also, organized into nerves that connect the CNS with peripheral structures

Nerve fibers consist of:

a. bundle of nerve fibers outside the CNS (or a "bundle of bundled fibers" or fasicles)
b. the connective tissue coverings that surround and ind the nerve fibers and fascicles together
c. blood vessels (vasa nervorum) that nourish the nerve fibers and their coverings

Types of nerve connective tissue coverings

Endoneurium
Perineurium
Epineurium

Endoneurium

Delicate connective tissue immediately surrounding the neurilemma cells and axons

Perineurium

Layer of dense connective tissue that encloses a fascicle of nerve fibers, providing an effective barrier against penetration of the nerve fibers by foreign substances

Epineurium

a thick connective tissue sheath that surrounds and encloses a bundle of fascicles, forming the outermost covering of the nerve
-includes fatty tissue, blood vessels, and lymphatics

Types of nerves

-Cranial: exit the cranial cavity through the foramina in the cranium
-Spinal: exit the vertebral column through the intervertebral foramina

Spinal Nerve Roots

-Anterior/ventral nerve root
-Posterior/dorsal nerve root
-both nerve roots unite, within or just proximal to the intervertebral foramen, to form a MIXED spinal cord, which then divides into a POSTERIOR/DORSAL RAMUS and an ANTERIOR/VENTRAL RAMUS

Anterior nerve root

Consists of motor (efferent) fibers passing from nerve cell bodies in the anterior horn of spinal cord gray matter to effector organs located peripherally

Posterior nerve root

Consists of sensory (afferent) fibers from cell bodies in the spinal sensory or posterior (dorsal) root ganglion that extend peripherally to sensory endings and centrally to the posterior horn of spinal cord gray matter

Dermatomes

The unilateral area of skin innervated by the sensory fibers of a single spinal nerve

Myotome

The unilateral muscle mass recieving innervation from the fibers conveyed by a single spinal nerve

Types of Somatic Fibers

-general sensory fibers (general somatic afferent [GSA]) fibers: transmit sensations from the body to the CNS
-Somatic motor fibers (general somatic efferent [GSE]): transmit impulses to skeletal (voluntary) muscles

Types of visceral fibers

-visceral sensory fibers/general visceral afferent GVA
-visceral motor fibers/general visceral efferent GVE
--two GVE fibers, synaptic and post synaptic, work together to conduct impulses from the CNS to smooth muscle or glands

Visceral sensory fibers

(general visceral afferent [GSE]): transmits pain or subconscious visceral reflex sensations (blood gas, BP, etc) from hollow organs and blood vessels to the CNS

Visceral motor fibers

(general visceral efferent [GVE] fibers): transmit impulses to smooth muscle and glandular tissue

Somatic Nervous System

-Composed of somatic parts of the CNS and PNS
-Provides sensory and motor innervation to all parts of the body, except the viscera in the body cavities, smooth muscle and glands

Somatic sensor system

-transmits sensations of touch, pain, temperature, and position from sensory receptors

Somatic motor system

-innervates only skeletal muscle, stimulating voluntary and reflexive movement by causing the muscle to contract, actually, as occurs in response to to touching a hot iron

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