CH. 16 Spinal Cord and Spinal Nerves Flashcards
What are the 5 parts of the spinal cord?
- Cervical part: superiormost region of spinal cord: contains motor neurons whose axons contribute to the cervica; spinal nerves and receives input from sensory neurons through these spinal nerves.
2) Thoracic part: lies inferior to the cervical part; contains neurons for the thoracic spinal nerves
3) Lumbar part: shorter segment of spinal cord that contains neurons for the lumbar spinal nerves
4) Sacral part: lies inferior to the lumbar part and contains the neurons for the sacral spinal nerves
5) Coccygeal part: most inferior tip of the spinal cord
What is the conus medullaris?
marks official end of the spinal cord proper; tapering inferior end of the spinal cord
What is the cauda equina and what strand of pia mater is located within it?
groups of axons inferior to conus medullaris that project inferiorly from the spinal cord;
filum tierminale is thin stand of pia mater that helps anchor the conus medullaris to the coccyx
What are the two longitudional grooves on the external surace of the spinal cord?
posterior median sulcus and anterior median sulcus
What spaces innervate the upper and lower limbs respectively?
cervical enlargement and lumbosacral enlargement
What are the structures that encircle the spinal cord from outermost to innermost?
vertebra, epidural space, dura mater, subdural space, arachnoid mater, subarachnoid space, and pia mater
What are the subdivisions of gray matter in the spinal cord?
1) Anterior horns: left and right anterior masses of gray matter that primarily house cell bodies of somatic motor neurons that innervate skeletal muscle
2) lateral horns: occur in the T1-L2 parts of spinal cord that contain cell bodies of autonomic motor neurons which innervate cardiac muscle, smooth muscle, and glands
3) posterior horns: left and right posterior masses of gray matter that contain axons of sensory neurons and cell bodies of interneurons
4) gray commissure: horizontal bar of gray matter that surround a narrow central canal that primarily contains unmyelinated axons and serves as a communication route between the right and left sides of gray matter
What are the groups of nuclei found in the gray matter of the spinal cord?
1) Sensory nuclei: located in the posterior horns and contain interneuron cell bodies
Somatic sensory nuclei: receive information from sensory receptor, such as pain or pressure receptors in the skin, and
Visceral sensory nuclei: receive information from sensory receptors such as the stretch receptors in the smooth muscle walls of viscera
2) Motor nuclei: anterior and lateral horns contain motor neuron cell bodies that send nerve impulses to muscles and glands
Somatic motor nuclei: in anterior horns innervate skeletal muscle and
Autonomic motor neurons: in lateral horns innervate smooth muscle, cardiac muscle, and glands
What are the 3 regions of white matter located in the spinal cord?
1) Posterior funiculus: lies between the posterior gray horns on the posterior side of the cord and posterior median sulcus
2) Lateral funiculus: white matter region on each lateral side of the spinal cord
3) Anterior funiculus: composed of tracts of white matter that occupy the space on each anterior side of the cord between the anterior gray horns and the anterior median fissure
- anterior funiculi arte interconnected by white commisure
What spinal nerve innervates the deep muscles of the back?
posterior ramus
What nerve innervates the anterior and lateral portions of the trunk, upper limbs, and lower limbs?
anterior ramus
How are nerve plexuses organized?
organized such that axons from each anterior ramus extends to body structures through several different branches; each terminal branch of the plexus houses axons from several different spinal nerves
What are the properties of a reflex?
■ A stimulus is required to initiate a reflex.
■ A rapid response requires that few neurons are involved and
synaptic delay is minimal.
■ A preprogrammed response occurs the same way every time.
■ An involuntary response requires no conscious intent or
preawareness of the reflex activity. Thus, reflexes are usually
not suppressed.
What are the five steps of a simple reflex arc?
1) Stimulus activates sensory receptor: sensory receptors respond to both external and internal stimuli
2) Nerve impulse tracels through sensory neuron to the CNS: sensory neurons conduct impulses from the receptor into the spinal cord
3) Information from nerve impulse is porcessed in integration center by interneurons: complex reflexes may use a number of interneurons with the CNS to integrate and process incoming sensory information and transmit information to a motor neuron - simple reflexes do not involve interneurons
4) Motor neuron transmits nerve impulse to effector: transmitted through anterior root of a motor neuron and then the spinal nerve to the peripheral effector organ
5) Effector responds to nerve impulse from motor neuron: effector is muscle or gland that responds to nerve impulse from motor neuron
What are the two ways in which reflex arcs may be termed?
Ipsilateral: when both receptor and effector organs of the reflex arc are on the same side of the spinal cord
Contralateral: when the sensory impulses from a receptor organ cross over through the spinal cord to activate offector organs in the opposite limb
