October 8 - Spinal Cord.docx

6 Pages
Unlock Document

Anatomy and Cell Biology
Anatomy and Cell Biology 3319

October 8, 2013 Spinal Cord Pp. 374-379, 360-362, 439-442 The Spinal Cord - Function: - Through the spinal nerves that attach to it, the spinal cord is involved in the sensory and motor innervation of the entire body inferior to the head - Provides a two-way conduction pathway for signals between the body and the brain - It is a major center for reflexes - Runs through the vertebral canal of vertebral column - Spinal cord extends from foramen magnum at the base of the skull’s occipital bone - At inferior end it tapers into the conus medullaris (cone of the spinal cord) - This cone in turn tapers into a long filament of connective tissue, the filum terminale (end terminal)  which attaches to the coccyx inferiorly - 31 pairs of spinal nerves (PNS structures) attach to the spinal cord - Spinal nerves lie in the intervertebral foramina, from which they send lateral branches throughout the body - Divided into groups:  Cervical (8)  Thoracic (12)  Lumbar (5)  Sacral (5)  Coccygeal (1) - In cervical and lumbar regions, nerves to upper and lower limbs arise, the spinal cord shows enlargements called cervical and lumbar enlargements - Cauda equina: nerve roots at the inferior end of vertebral canal (horse’s tail) - Spinal cord forms from neuroectoderm - Its segmented appearance reflects the pattern of the adjacent somites - Spinal cord segment: indicate the region of the spinal cord from which the nerve fibers that form a given spinal nerve emerge  Each spinal cord segment is designated by the spinal nerve that issues from it - Spinal cord does not extend to the end of the spinal column - Spinal cord segments are located superior to where their corresponding spinal nerves emerge through the intervertebral foramina - Spinal cord is wider laterally than anteroposteriorly - Two grooves:  Dorsal (posterior) median sulcus  Ventral (anterior) median fissure – wider one  These 2 grooves run the length of the cord and partly divide it into right and left halves - White matter of the spinal cord - Ascending: most ascending fibers in spinal cord carry sensory info from sensory neurons of body up to the brain - Descending: most descending fiber carry motor instructions from brain to spinal cord, to stimulate contraction of body’s muscles and secretion from glands - Commissural: a commissure is a bundle of axons that crosses from one side of the CNS to the other, and commissural fibers are white- matter fibers that carry info from one side of spinal cord to the other - White matter on each side of spinal cord is divided into 3 funiculi (long ropes):  Dorsal (posterior) funiculus  Ventral (anterior) funiculus  Lateral funiculus  Ventral and lateral funiculi are continuous with each other  Contain many fiber tracts – composed of axons that all have similar destinations and functions - Gray matter of spinal cord and spinal roots - Consists of a mixture of neuron cell bodies, short unmyelinated axons and dendrites and neuroglia - Gray commissure: crossbar of gray matter  Composed of unmyelinated axons that cross from one side of the CNS to the other  Contains the central canal: narrow cavity of spinal cord - The 2 posterior arms of the H are the dorsal (posterior) horns –  Interneuron’s  receive info from sensory neurons whose cell bodies lie outside the spinal cord in dorsal root ganglia and whose axons reach the spinal cord via the dorsal roots - The 2 anterior arms of the H are the ventral (anterior) horns –  Motor neurons  send their axons out of spinal cord via the ventral roots to supply muscles and glands  Ventral horns are largest in the cervical and lumbar segments because they innervate the upper and lower limbs (more skeletal musculature) - Lateral horns: small lateral gray matter columns present in the thoracic and superior lumbar segments - 4 zones of spinal cord gray matter:  Somatic sensory (SS)  Visceral sensory (VS)  Visceral motor (VM)  Somatic motor (SM) - Damage to spinal cord or spinal roots: - Can cause paralysis (loss of motor function) or parasthesia (abnormal or lost sensation) - Severe damage to ventral horn or to ventral motor roots destroys the somatic motor neurons in the region of injury and results in complete, or flaccid paralysis  Because muscles are no longer stimulated by neurons, they shrink and waste away, and spinal reflexes are absent - Damage of only the descending fiber tracts in the white matter of the spinal cord leaves the spinal cord motor neurons and spinal reflexes intact  Muscles remain healthy, but their movements are no longer under voluntary control because their connection to the brain has been lost – spastic paralysis - Protection of the spinal cord - Neural tissue is protected by vertebrae, meninges, and by watery cushion of cerebrospinal fluid - Meninges  Function: (1) cover and protect the CNS, (2) enclose and protect the blood vessels that supply the CNS, and (3) contain the cerebrospinal fluid  Dura Mater (most external)  Leathery “tough mother” – strongest of meninges  Composed of dense fibrous connective tissue and forms a tough protective covering  Spinal dural mater: dura mater around spinal cord  Epidural space: just external to spinal dura; filled with cushioning fat and a network of veins o Anesthetics are often injected here  Arachnoid Mater  Subdural space: space between arachnoid and dura o Contains only a film of fluid o Potential space because it has potential to
More Less

Related notes for Anatomy and Cell Biology 3319

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.