Ch. 12 Flashcards
Spinal cord
the major communication link between the brain and the PNS inferior to the head. Integrates incoming info and produces responses
Spinal nerves
Exit the vertebral column through intervertebral and sacral foramina. Each spinal cord is a bundle of axons, schwann cells and connective tissue sheath.
31 pairs
Cervical enlargement
Location where nerve fibers that supply upper limbs enter and leave the spinal cord
Lumbosacral enlargement
in inferior thoracic, lumbar, and superior sacral regions where nerve fibers supplying lower limbs enter or leave the spinal cord.
Conus medullaris
Cone-like region where spinal cord tappers, inferior to the lumbosacral enlargement
Cauda equina
The numerous roots of spinal nevers extending inferiorly from the lumbosacral enlargement and conus medullaris
Meninges
Connective tissue membranes that surround spinal cord and brain
Dura mater
Most superficial and thickest membrane in the meninge of spinal cord. Forms a sac called Thecal sac, which surrounds spinal cord
Epidural space
Space between the walls of the vertebral canal and dura mater of the spinal cord that contains spinal nerve roots, blood vessels, areolar connective tissue and adipose tissue
Epidural anesthesia
often administered to woman in childbirth by injecting anesthetics into the epidural space of the spinal cord
Arachnoid
2nd deepest meningeal membrane. Very thin and wispy
Subdural space
The space between arachnoid mater and the dura mater. Contains a very small amount of serous fluid
Pia Mater
The 3rd deepest meningeal layer. Bound very tightly to the surface of the spinal cord
Denticulate ligaments
Connective tissue septa extending from the lateral sides of the spinal cord to the dura mater
Filum terminale
connective tissue strand that anchors the conus medullaris and the thecal sac to the first coccygeal vertebra, limiting their superior movement
Subarachnoid space
Contains web-like strands of the arachnoid mater, blood vessels and cerebrospinal fluid
Anterior median fissure & posterior median sulcus
deep clefts partially separating the 2 halves of the cord
What are the 3 columns or funiculi in each half of the spinal cord?
Ventral (anterior)
Dorsal (Posterior)
Lateral columns
Each column of the spinal cord is subdivided into …
Tracts or fasicles
The central gray matter is organized into what horns?
Dorsal horn
Ventral horn
Small lateral horns
What are gray and white commissures?
Contain axons that cross from one side of teh spinal cord to the other
What is the central canal?
located in center of the gray commissure, helps circulate CSF associated with the ventricular system
Ventral root
6-8 rootlets combined on the ventral side of spinal cord
Dorsal root
6-8 rootlets combined on the dorsal side of the spinal cord
Dorsal root ganglion?
where Sensory neuron cell bodies are contained
What is a reflex?
automatic response to a stimulus. Occurs without conscious thought
What is a reflex arc?
The neural pathway that controls a reflex
Monosynaptic reflexes
involve simple neuronal pathways in which sensory neurons synapse directly with motor neurons without any interneurons
Polysynaptic reflexes
involve more complex pathways that have multiple synapses with interneurons between the sensory and motor neurons
What is the stretch reflex?
The simplest reflex. A reflex contraction of muscles in response to stretching of that same muscle
Muscle spindle
The sensory receptor of the stretch reflex. 3-10 small specialized skeletal muscle fibers that are contractile only at their ends
Alpha motor neuron
Causes the muscle to contract*
Knee-jerk reflex
When the doctor taps on the patellar ligament and your knee kicks
Gamma motor neurons
Innervate the ends of the muscle spindles
Golgi tendon reflex
Prevents contracting muscles from applying excessive tension to tendons
Golgi tendon organs
The sensory receptors for the golgi tendon reflex
What is the withdrawal reflex?
To remove a limb or another body part from a painful stimulus
Reciprocal innervation
a phenomenon that allows opposing muscles to reinforce the efficiency of the withdrawal reflex
Crossed extensor reflex
Another reflex associated with withdrawal reflex. Occurs on opposite side of the body from the stimulus
Endoneurium
delicate connective tissue layer that surrounds each axon, or nerve fiber
Perineurium
Heavier connective tissue layer that surrounds groups of axons to form nerve fascicles
Epineurium
3rd layer of dense connective tissue that binds the nerve fascicles together to form a nerve
Ramus
A major branch of a spinal cord
Dermatome
is the area of the skin supplied with sensory innervation by a pair of spinal nerves
What is a dorsal rami
innervates most of the deep muscles of the dorsal trunk responsible for moving the vertebral column
Ventral rami
In the thoracic region, form intercoastal nerves which extend along the inferior margin of each rib and innervate the intercoastal muscles and skin over thorax
PLexus
intermingling of nerves
What is the cervical plexus?
relatively small plexus originating from spinal nerves C1-C4
Ansa cervicalis
unusual part of the cervical plexus, a loop between C1 and C3. Nerves to the infrahyoid muscles branch from ansa cervialis
Phrenic nerve
One of the most important derivatives of the cervical plexus. Important for breathing
Brachial plexus
Originates from spinal nerves C5-T1
Axillary nerve
Innervates the deltoid and teres minor muscles. Provides sensory innervation to the shoulder joint and to the skin over part of the shoulder
Radial nerve
Innervates all of the extensor muscles of the upper limb, the supinator muscle and the brachioradialis
Musculocutaneous nerve
provides most motor innervation to the anterior muscles of the arm, as well as cutaneous sensory innervation to part of forearm
Ulnar nerve
Innervates 2 forearm muscles plus most of the intrinsic hand muscles
