click below
click below
Normal Size Small Size show me how
NS intro
Introduction into the nervous system
Question | Answer |
---|---|
Identify the structural components and functional parts of the nervous system | Structure: CNS (brain and spinal cord) and PNS (cranial and spinal nerves); Functional: Somatic nervous (embryonic somites and branchial arches) and visceral nervous (both have motor and sensory); Motor (efferent) and sensory (afferent) |
Describe the basic features of the neuron | Cell body, dendrites, and axon (aka fibers); communicate via synapses using neurotransmitters |
Describe the structure of the typical nerve and its functional fiber types | Composed of 2 rootlets (dorsal sensory root and a ventral motor root). Dorsal ganglia located in the interveterbral foramen and is pseudounipolar. Ventral root carriers motor, ganglia is in ventral horn, and is multipolar. Splits: dorsal and ventral rami |
What are the upper and lower boundaries of the spinal cord | foramen magnum and the intervetebral disc between L1 and L2 |
Define a dermatome | The area of the skin supplied by the dorsal (sensory) root of the spinal nerve |
Define a spinal cord segment | The region of the spinal cord to which a spinal nerve is attached |
Define a somatic nerve plexus | A network of nerve fibers: formed by the ventral ramus (always) of certain spinal nerves. E.g. cervical plexus, brachial plexus, lumbar plexus, sacral plexus. |
Define an autonomic nerve plexus | Network of sympathetic and parasympathetic nerve fibers |
Describe the anatomical reason making the lumbar puncture (spinal tap) possible | Able to withdraw cerebrospinal fluid from the lumbar cistern by inserting a needle a level below L4 (Since the spinal cord terminates at L1/L2, the only thing the needle touches is the cauda equina-->no damage) |
How many spinal nerves are there? | 31 |
How many of each spinal nerve pairs are there? | 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal |
Describe where each of the spinal nerves exit the spinal cord in relation to the vertebrae | C1 exits between occipital bone and atlas; C2-C7 exit immediately above corresponding vertebrae; C8 exits between C7 and T1; all others exit below their respective vertebrae |
Explain why the spinal cord stops at L1/L2 | Spinal cord grows at the same rate as vertebral column up until 3rd month of fetal development. At birth: ends at L3; In adults at L1/L2 |
What is the cauda equina? | The dorsal and ventral roots of the lower lumbar, sacral, and coccygeal spinal nerves that need to descend within the vertebral canal to reach their intervertebral foramina (since their intervetebral disks exit superior to L1/L2) |
Describe the locations of the fusiform enlargements of the spinal cord | Cervical: C5 to T1 (for brachial plexus); Lumbar: L1 to S3 for the (lumbosacral plexus) |
What is the conus medullaris and where is it located? | It is the where the spinal cord ends; located below lumbar enlargement (Near L1 and L2 vertebrae); NOT the same as the termination of the dural sac (near S3) |
What are the meninges? | The protective barrier between bone and soft tissue of the CNS; they include the Dura mater, the arachnoid mater, and the pia mater |
What is the dura mater? | It is the outermost tough fibrous layer of the meninges |
What space separates the spinal dura from the vertebrae? | The epidural space |
What is the dural sac? What meningeal layer is it composed of? | A long tubular sheath within the vertebral canal; formed by the dura mater |
At what vertebral level does the dural sac end? | S2 (where it is attached) |
What is the arachnoid mater? | A delicate membrane held against the inner surface of the dura; lies between the dura and the pia mater; contains cerebrospinal fluid |
What is the arachnoid trabeculae? | Delicate strands of connective tissue that span the subarachnoid space connecting the arachnoid and pia mater |
Where is the pia mater located? | It is the innermost layer of the meninges; it is closely adherent to the neural tissue |
What ligament of the pia mater suspends the spinal cord in the dural sac? | The denticulate ligament (looks like sawtooth) |
What is the filum terminale internum? What is the filum terminale externum (aka...?) | At the apex of the cord, pia mater continues down with the cauda equina to end of the dural sac, pierces it, and attaches to the tip of the coccyx. |
Where does the subarachnoid space lie? | Below the arachnoid mater in the space that encloses the spinal cord and the spinal nerve roots. |
Where is the lumbar cistern? | The enlargement of the subarachnoid space caudal to the conus medullaris containing the cauda equina, extending from L2 to the second segment of the sacrum |