General information about the nervous system.

Human Anatomy, 3rd edition Prentice Hall, © 2001 Structure of the Spinal Cord Extends from the foramen magnum to the first or second lumbar vertebra. Ends in the conus medullaris Filum terminale –Extends from conus medullaris to sacral vertebrae Cauda equina –= filum terminale + dorsal & ventral roots from spinal nerves that extend below conus medularis

Human Anatomy, 3rd edition Prentice Hall, © 2001 Coverings of the Spinal Cord 3 layers called meninges Dura mater –Outer layer Arachnoid –Middle layer Pia mater –Adheres tightly to the surface of the spinal cord

Human Anatomy, 3rd edition Prentice Hall, © 2001 Meninges of the Spinal Cord

Human Anatomy, 3rd edition Prentice Hall, © 2001 Meninges of the Spinal Cord

Human Anatomy, 3rd edition Prentice Hall, © 2001 Sectional Anatomy of the Spinal Cord Inner part consists of gray matter –Unmyelinated cell bodies, neuroglia, & dendrites –Organized into “horns” Outer part consists of white matter –Tracts of myelinated fibers –Ascending tracts are sensory –Descending tracts are motor

Human Anatomy, 3rd edition Prentice Hall, © 2001 Example of Ascending Nerve Tracts

Human Anatomy, 3rd edition Prentice Hall, © 2001 Spinal Nerves Connect to the spinal cord via a dorsal and a ventral root Dorsal root is sensory –Contains a dorsal root ganglion Ventral root is motor

Human Anatomy, 3rd edition Prentice Hall, © 2001 Spinal Nerves The roots unite into the spinal nerve Spinal nerves exit through intervertebral foramen Split into branches, or rami. –Dorsal ramus –Ventral ramus –Regions of skin supplied by a spinal nerve = dermatomes (“skin slices”)

Human Anatomy, 3rd edition Prentice Hall, © 2001 Dermatomes

Human Anatomy, 3rd edition Prentice Hall, © 2001 Nerve Plexuses Plexus = “braid” Nerves supplying the limbs form plexuses when they leave the spinal cord –Cervical plexus –Brachial plexus –Lumbosacral plexus Lumbar plexus Sacral plexus

Human Anatomy, 3rd edition Prentice Hall, © 2001 Cervical Plexus Formed by spinal nerves C1 – C5 –Nerves innervate the neck and shoulder region –Phrenic nerve to the diaphragm

Human Anatomy, 3rd edition Prentice Hall, © 2001 Brachial Plexus Formed by spinal nerves C5 – C8 and T1 –Nerves innervate the arm and shoulder Radial nerve Ulnar nerve Median nerve

Human Anatomy, 3rd edition Prentice Hall, © 2001 Brachial Plexus

Human Anatomy, 3rd edition Prentice Hall, © 2001 Lumbosacral Plexus

Human Anatomy, 3rd edition Prentice Hall, © 2001 Lumbar Plexus Formed by spinal nerves T12 and L1 – L4. –Innervates the medial and anterior portions of the thigh and lower abdominal regions –Lateral femoral cutaneous nerve

Human Anatomy, 3rd edition Prentice Hall, © 2001 Sacral Plexus Formed by spinal nerves L4 and L5, and S1 and S2 –Innervates the posterior portion of the hip, thigh, and leg, and the genital region –Sciatic nerve

Human Anatomy, 3rd edition Prentice Hall, © 2001 Sacral Plexus

Human Anatomy, 3rd edition Prentice Hall, © 2001 Spinal Reflexes Reflexes are automatic responses to stimuli Spinal reflexes result from the stimulation of a spinal reflex arc.

Human Anatomy, 3rd edition Prentice Hall, © 2001 Basic Elements of a Reflex Arc

Human Anatomy, 3rd edition Prentice Hall, © 2001 Midbrain Located btwn the diencephalon and the pons. –2 bulging cerebral peduncles on the ventral side. These contain: Descending fibers that go to the cerebellum via the pons Descending pyramidal tracts –Running thru the midbrain is the hollow cerebral aqueduct which connects the 3 rd and 4 th ventricles of the brain. –The roof of the aqueduct ( the tectum) contains the corpora quadrigemina 2 superior colliculi that control reflex movements of the eyes, head and neck in response to visual stimuli 2 inferior colliculi that control reflex movements of the head, neck, and trunk in response to auditory stimuli

Human Anatomy, 3rd edition Prentice Hall, © 2001 Cranial nerves 3&4 (oculomotor and trochlear) exit from the midbrain Midbrain also contains the headquarters of the reticular activating system

Human Anatomy, 3rd edition Prentice Hall, © 2001 Medulla Oblongata Nuclei in the medulla are associated w/ autonomic control, cranial nerves, and motor/sensory relay. Autonomic nuclei: –Cardiovascular centers Cardioinhibitory/cardioaccele ratory centers alter the rate and force of cardiac contractions Vasomotor center alters the tone of vascular smooth muscle –Respiratory rhythmicity centers Receive input from the pons –Additional Centers Emesis, deglutition, coughing, hiccupping, and sneezing

Human Anatomy, 3rd edition Prentice Hall, © 2001 Medulla Oblongata Sensory & motor nuclei of 5 cranial nerves: –Auditory/Vestibular (8), Glossopharyngeal (9), Vagus (10), Accessory (11), and Hypoglossal (12) Relay nuclei –Nucleus gracilis and nucleus cuneatus pass somatic sensory information to the thalamus –Olivary nuclei relay info from the spinal cord, cerebral cortex, and the brainstem to the cerebellar cortex.

Human Anatomy, 3rd edition Prentice Hall, © 2001 Spinal Cord Functions to transmit messages to and from the brain (white matter) and to serve as a reflex center (gray matter). Tube of neural tissue continuous w/ the medulla at the base of the brain and extends about 17” to just below the last rib. (Ends at L1) Majority of the SC has the diameter of your thumb Thicker at the neck and end of the cord (cervical and lumbar enlargements) b/c of the large group of nerves connecting these regions of the cord w/ the arms and legs.

Human Anatomy, 3rd edition Prentice Hall, © 2001 Spinal Cord Surrounded by a single layered dura mater and arachnoid and pia mater. Terminates in cone shaped structure called the conus medullaris. –The filum terminale, a fibrous extension of the pia mater, extends to the posterior surface of the coccyx to anchor the spinal cord. The cord does not extend the entire length of the vertebral column – so a group of nerves leaves the inferior spinal cord and extends downward. It resembles a horses tail and is called the cauda equina.

Human Anatomy, 3rd edition Prentice Hall, © 2001 Cross Sectional Anatomy of the Spinal Cord Flattened from front to back. Anterior median fissure and posterior median sulcus partially divide it into left and right halves. Gray matter is in the core of the cord and surrounded by white matter.

Human Anatomy, 3rd edition Prentice Hall, © 2001 Resembles a butterfly. 2 lateral gray masses connected by the gray commissure. Posterior projections are the posterior or dorsal horns. Anterior projections are the anterior or ventral horns. In the thoracic and lumbar cord, there also exist lateral horns.

Human Anatomy, 3rd edition Prentice Hall, © 2001

Spinal Cord & Spinal Nerves Spinal cord –Truly the pathway between body and mind –Conducts impulses to and from the brain –Carries out spinal reflexes Spinal nerves –31 pairs –All are mixed nerves

Human Anatomy, 3rd edition Prentice Hall, © 2001 Spinal Cord Injuries Can affect sensory perception; motor paralysis Location affects severity of the injury Spinal compression results from squeezing the spinal cord within the vertebral canal Spinal transection is the severing of the spinal cord

Spinal Cord Injuries Quadriplegia Paraplegia