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Chapter 12 A&P
Spinal Cord and Spinal Nerves
| Question | Answer |
|---|---|
| What are the functions of the spinal cord? | Major communication link between the brain and PNS inferior to the head; it also mediates the spinal reflexes |
| How long is the spinal cord? | It extends from the FORAMEN MAGNUM of the skull superiorly to the level of the SECOND LUMBAR vertebra |
| What are the four sections of segments in the spinal cord? | CERVICAL, THORACIC, LUMBAR, SACRAL |
| What are the two major enlargements of the spinal cord? | CERVICAL and LUMBOSACRAL |
| What is the conus medullaris? | Cone-like inferior end of the spinal cord |
| What is the cauda equina? | Refer to the nerves passing inferiorly from the lumbosacral enlargement and conus medullaris; resemble a horse's tail |
| What are the three meninges that surrounds the spinal cord and brain? | DURA MATER, ARACHNOID MATER, PIA MATER |
| What is the space between the walls of vertebral canal and the DURA MATER of the spinal cord? | EPIDURAL SPACE |
| What is the DURA MATER? | Most superficial and thickest of the meninges |
| What is the space between the ARACHNOID MATER and DURA MATER? | SUBDURAL SPACE |
| What is the ARACHNOID MATER? | Middle meningeal membrane - thin and wispy |
| What is the space between the ARACHNOID MATER and the PIA MATER? | SUBARACHNOID SPACE |
| What is the PIA MATER? | The innermost meningeal layer - clings tightly to surface of spinal cord and brain |
| What is the filum terminale? | A connective tissue strand that anchors the conus medullaris and thecal sac to the first coccygeal vertebrae, limiting their superior movement |
| Where is the white matter found on a cross section of the spinal cord? | Towards the peripheral (on the outside edge); composed of myelinated axons organized into columns (funiculi) |
| Where is the gray matter found on a cross section of the spinal cord? | Central part; composed of neuron cell bodies, dendrites, unmyelinated axons |
| How is the left and right halves divided in a cross section of the spinal cord? | By the anterior median fissure and posterior median sulcus |
| Which horn of the central gray matter in the spinal cord contains sensory neurons? | POSTERIOR/DORSAL HORN |
| Which horn of the central gray matter in the spinal cord contains somatic motor neurons? | ANTERIOR/VENTRAL HORN |
| Which horn of the central gray matter in the spinal cord contains autonomic motor neurons around a central canal that contains CSF? | LATERAL HORN |
| What is the role of the dorsal root V.S. the ventral root? | The dorsal root conveys SENSORY input into the spinal cord; the ventral root conveys MOTOR output away from the spinal cord |
| Where do spinal nerves originate from? | Each of the 31 spinal nerves originates from the spinal cord by fusion of roots from anterior/ventral horn and posterior/dorsal horn |
| What are reflexes? | Automatic responses WITHOUT CONSCIOUS THOUGHT; HOMEOSTATIC |
| What is a reflex arc? | Basic fundamental unit of the nervous system; the smallest and simplest portion that can receive a stimuli and produce a response |
| What are the five components of a reflex arc? | SENSORY RECEPTOR, SENSORY NEURON, INTERNEURON, MOTOR NEURON, AND EFFECTOR ORGAN |
| What are the two types of reflexes? | AUTONOMIC - respond to internal body changes; SOMATIC - maintain balance and posture or remove the body from painful stimuli |
| Where are reflexes integrated (interpreted)? | Within the brain and spinal cord; higher brain centers can suppress or exaggerate reflexes |
| What happens in a stretch reflex? What kind of reflex is this involving what kind of neurons? What is an example? | Muscle contraction in response to stretching a muscle spindle embedded within a muscle; this is to maintain posture - simplest of the reflexes. MONOSYNAPTIC - there is no interneuron just sensory neurons and motor neurons EX: Patellar (knee-jerk) reflex |
| What happens in the Golgi tendon reflex? | Muscle relaxation in response to intense stretching of the Golgi tendon organ embedded in the tendon of the muscle; this prevents contracting muscles from applying excessive tension to tendons, for protection against muscle or tendon injury |
| What happens in a withdrawal reflex? | Withdrawal of a limb (usually by flexion) in response to a painful stimulus; this is a POLYSNAPTIC - sensory neurons synapse with excitatory interneurons, which in turn synapse with alpha motor neurons |
| What happens in reciprocal innervation? | Causes relaxation of extensor muscles when flexor muscle contracts; reinforces the efficiency of the withdrawal reflex and also involved in stretch reflex |
| What is the crossed extensor reflex? Give an example. | When a withdrawal reflex is initiated in one lower limb, this reflex causes extension of the opposite lower limb. EX: after coming off of a tack your weight shifts to the other limb to help prevent you from falling |
| What are spinal nerves consist of? | Axon, Schwann cells, and connective tissue |
| What are the three CT layers of the spinal nerves? | ENDONEURIUM - surround an individual axon and its Schwann cell sheath; PERINEURIUM - surround groups of axons (nerve fascicles); EPINEURIUM - dense CT that binds fascicles together into a nerve (the outermost layer) |
| What is the make-up of the 31 pairs of spinal nerves? | 8 CERVICAL, 12 THORACIC, 5 LUMBAR, 5 SACRAL PAIRS, 1 COCCYGEAL PAIR |
| Where does the first pair exit? Where does the last four pair exit? And the rest? | First pair - exit vertebral column between skull and atlas; last four pairs - exit via SACRAL FORAMINA; others - exit through INTERVERTERBRAL FORAMINA |
| What are DERMATOMES? Dermatonal map? | Specific cutaneous distributions on spinal nerves; DERAMATONAL MAP - skin area supplied with sensory innervation by spinal nerves |
| Spinal nerves branch to form rami. What does the dorsal rami do? | Supply muscles and skin near the midline of the back |
| What does the ventral rami do? | In the thoracic region forms intercostal nerves, which supply the thorax and upper abdomen; the remaining ventral rami join to form PLEXUSES |
| What is the difference between a rami and a root? | Nerves converge to form roots and roots branches off to form rami |
| Which spinal nerves form the cervical plexus? | Spinal nerves C1-C4; supplies some muscles and the skin of the neck and shoulder |
| Which spinal nerves form the brachial plexus? | Spinal nerves C5-T1; supplies the upper limb (axillary, radial, ulnar, and median nerves) |
| Which spinal nerves form the lumbosacral plexus? | Spinal nerves L1-S4; supplies the lower limbs (femoral, tibial, fibular, sciatic nerves) |
| Which spinal nerves form the coccygeal plexus? | Spinal nerve S5 and coccygeal nerve; supplies the muscles of the pelvic floor and the skin over the coccyx |
Created by:
nnguye42
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