Spinal cord and reflex Flashcards
(27 cards)
The Spinal Cord & Spinal Nerves Functions
-spinal cord reflexes
-integration (summation of inhibitory and excitatory) nerve impulses
-highway for upward and downward travel of sensory and motor information
Spinal Cord Protection
By the vertebral column, meninges, cerebrospinal fluid, and vertebral ligaments.
Dura mater
-outer dense irregular CT tube
-Subdural space filled with interstitial fluid
Arachnoid
-middle spider web of collagen fibers
-Subarachnoid space = CSF
Pia mater
-inner thin layer covers BV
-denticulate ligs hold in place
External Anatomy of Spinal Cord
-Begin at foramen magnum
-Flattened cylinder
-16-18 Inches long & 3/4 inch diameter
-In adult ends at L1/L2
-Growth of cord stops at age 5
Conus medullaris
cone-shaped end of spinal cord
Filum terminale
-thread-like extension of pia mater
-stabilizes spinal cord in canal
Caudae equinae (horse’s tail)
dorsal & ventral roots of lowest spinal nerves
Spinal segment
area of cord from which each pair of spinal nerves arises
Spinal Cord & Spinal Nerves
-Spinal nerves begin as roots
-Dorsal or posterior root is incoming sensory fibers
-dorsal root ganglion (swelling) = cell bodies of sensory nerves
-Ventral or anterior root is outgoing motor neuron (axon)
Gray Matter of the Spinal Cord
-Gray matter is shaped like the letter H or a butterfly
-contains neuron cell bodies, unmyelinated axons & dendrites
-paired dorsal and ventral gray horns
-lateral horns only present in thoracic spinal cord
-gray commissure crosses the midline
-Central canal continuous with 4th ventricle of brain
White Matter of the Spinal Cord
-White matter covers gray matter
-Anterior median fissure deeper than Posterior median sulcus
-Anterior, Lateral and Posterior White Columns contain axons that form ascending & descending tracts
Spinal Reflexes
-Automatic response to change in environment
-Integration center for spinal reflexes is gray matter of spinal cord
-Examples
somatic reflexes result in skeletal muscle contraction
autonomic (visceral) reflexes involve smooth & cardiac muscle and glands.
heart rate, respiration, digestion, urination, etc
Reflex Arc and 5 components
-The ‘wiring’ of a single reflex pathway
-5 components of reflex arc
receptor
sensory neuron
integrating center
motor neuron
effector
Classification of Reflex According to the Development:
Innate
Acquired
Classification of Reflex According to the Response
Somatic reflex
Autonomic (visceral) reflex
Classification of Reflex According to the Complexity of circuit
Monosynaptic reflex
Polysynaptic reflex
Classification of Reflex According to the Processing site
Spinal reflex
Cranial reflex
Somatic Reflex
-Strech reflex
-Tendon Reflex
-Flexor reflex
-Crossed Extensor reflex
-Superficial cord reflex
The Brain Can Alter Spinal Reflexes
-plantar reflex - toes in/downward
-babinski sign- toes outward
Spinal Nerves
-31 Pairs of spinal nerves
-Named & numbered by the cord level of their origin
-8 pairs of cervical nerves (C1 to C8)
-12 pairs of thoracic nerves (T1 to T12)
-5 pairs of lumbar nerves (L1 to L5)
-5 pairs of sacral nerves (S1 to S5)
-1 pair of coccygeal nerves
-Mixed sensory & motor nerves
Connective Tissue Coverings
-Endoneurium = wrapping of each nerve fibers
-Perineurium = surrounds group of nerve fibers forming a fascicle
-Epineurium = covering of entire nerve
dura mater blends into it at intervertebral foramen
Cervical Plexus
-Ventral rami of spinal nerves (C1 to C5)
-Supplies parts of head, neck & shoulders
-Phrenic nerve (C3-C5) keeps diaphragm alive
-Damage to cord above C3 causes respiratory arrest
