Spinal Cord and Spinal Nerves Flashcards
3 Meninges
Protect the Spinal Cord which is fluid filled
Order of Meninges + Surroundings
1. Epidural Space
2. Dura Mater
3. Arachnoid Mater
4. Subarachnoid Space
5. Pia mater
Dura Mater (Meninge)
Outermost and toughest layer
Surrounded by epidural space
Arachnoid Mater
Interior to the dura mater, Thin, Spider web like extension to the pia mater
Subarachnoid Space
Between the pia mater and the arachnoid mater
Filled with CSF
Provides protective cushion around the spinal cord and brain
Pia Mater (Meninge)
Tightly adheres to the spinal cord and it is delicate
* Continues past end of Spinal cord and becomes the Filum Terminale
Central Canal
- Narrow passageway in the spinal cord that holds the CSF
- Runs through the center of the whole spinal cord and connects to the brain’s ventricles
Termination of the Medulla Oblongata of the Brain
Where the spinal cord begins
Spinal Cord Length
Spinal cord passes through successive vertebral foramina to L1/L2
Conus Medullaris
Cone-shaped termination of the spinal cord found out L1/L2
Filum terminale
The band the pia mater becomes past the end of the spinal cord
Tethers spinal cord to sacrum and coccyx
Denticulate Ligaments
20 paired lateral extensions along the length of the spinal cord formed by the pia mater
- Provide stability
Cervical and Lumbar Enlargements*
Larger than the intervening regions due to the large number of neurons dealing with the innervation of the limbs
Where do the spinal nerve roots emerge from? PNS or CNS?
Emerge from the left and right sides of the spinal cords
- Part of the PNS
Spinal Nerves (31 pairs)
- Cervical, thoracic, lumbar, sacral, coccygeal spinal nerves that serve these regions of the body
Cauda Equina
Bundle of spinal nerve roots as the spinal nerves passes through the vertebral canal to get to diff body parts
Anterior Median Fissure
A large cleft on the ventral side of the spinal cord
- Cuts into white matter along the spinal cord
White Matter
- Myelinated axons that give it its color
Dorsal, Lateral, Ventral Columns
Columns that organize the bundles of axons (tracts) running up and down the spinal cord
Corticospinal Tracts
- Largest Descending Tracts
- Carries info from the cerebral cortex to the motor neurons from the spinal cord
- Ventral column
Spinothalamic Tract
- Ascending Tract
- Neurons carry pain and temperature signals from the spinal cord upward to the thalamus of the brain
Gray Matter
- Shaped like an H/butterflu
- Contains interneurons allowing for communication to and from the brain and other spinal cord regions
Dorsal Horn (SENSORY)
- Gray matter column that contains the cell bodies of neurons that receive sensory information
- Somatic Sensory Region: signals from skin, skeletal muscles, bones (arrive at dorsal-most region)
- Visceral Sensory Region: signals from organs (arrive at central region of dorsal horn)
- contains sensory neurons cell bodies
Ventral Horn (MOTOR)
- Contains cell bodies of motor neurons
Somatic Motor Region: Motor neurons that travel out the spinal cord to skeletal muscles
Lateral Horn (MOTOR)
- Contains cell bodies of motor neurons
Visceral Motor Region: motor neurons that travel to glands and smooth/cardiac muscles
Cervical Vertebrae and Cervical Spinal Nerves
7 Cervical Vertebrae
8 Cervical Spinal Nerves (above vertebra)
* C8 exits above T1 since there is no C8 vertebra
Thoracic Vertebrae and Thoracic Spinal Nerves
12 Thoracic vertebrae and spinal nerves
* Nerves are under vertebra
Lumbar Vertebra and Lumbar Spinal Nerves
5 lumbar vertebra and spinal nerves
* Nerves are under vertebra
Sacrum and Sacral Spinal Nerves
5 sacral vertebrae fuse to form sacrum and 5 sacral spinal nerves
* Nerves are under vertebra
Dermatome
Skin segments that correspond to spinal nerve
- innervated by nerves
- T10 dermatome is innervated by 10th pair of thoracic spinal nerve
Nerve
Organ comprised of neurons, connective tissue, and blood vessels and axons are found within them
Ganglion
Cluster of neuron cell bodies (soma)
Dorsal Root
Contains only sensory neurons entering the dorsal horn of the spinal cord
Dorsal Root Ganglion
Swelling formed by the sensory neurons’ cell bodies
- buldge
Sensory Neurons
- Unipolar/psedounipolar bc they have the cell body in the middle of their length
Ventral Root
Contains only axons of motor neurons and
- cell bodies are in the ventral and lateral horn of the gray matter
Rami
Branches of the spinal nerve
Dorsal Ramus
Contains somatic motor and somatic sensory neurons headed to or from the skin/muscle/bones of the back
Ventral Ramus
Carries somatic motor and somatic sensory neurons to the skin, muscle, and bones of the body wall and limbs
Communicating Ramus
Pair of small branches that carry neurons to the smooth muscle, cardiac muscle, and glands of the body
Sympatheitc Ganglion
Site where neurons from communicating ramus synapse and the location of cell bodies
Sympathetic Chain
Formed from ganglia and connecting branches
- Distribution hub for visceral neurons
Plexus
Formed from largest rami (ventral)
- Group of nerves
- Plexuses: combine somatic motor and sensory neurons from 6 ventral rami to form nerves that contain axons from multiple spinal nerves
Intercostal Nerves
Ventral rami of thoracic spinal nerves continue around the lateral sides of the body as the intercostal nerves
Cervical Plexus
Formed from ventral rami of cervical spinal nerves and innervates many of the neck muscles and diaphragm
Brachial Plexus
Formed from ventral rami of C5-T1 spinal nerves and supplies the upper appendage
Lumbosacral Plexus
Formed from ventral rami of L2-S4 spinal nerves and supplies the lower appendage
Polysynaptic Reflexes
- Involves one or several interneurons (synapse)
- 1st synapse w/ sensory neuron: dorsal horn
- 2nd synapse w/motor neuron: ventral horn
-Withdrawal Reflex: hand on stove
Monosynaptic Reflexes
- sensory neurons synapse directly with the ventral horn’s motor neurons
- Knee jerk
- no interneurons
Descending Pathway
The systems of neurons that bring info from the brain down to the appropriate muscle or gland of the body
*Corticospinal tract
- Upper Motor Neuron: interneuron of CNS that travels in the corticospinal tract and has its cell body in the cerebral cortex and terminal in the ventral horn (originates in primary motor cortex - precentral gyrus)
SYNAPSE AT VENTRAL HORN
- Lower Motor Neuron: Peripheral motor neuron that travels within the spinal nerve and eventually reaches its skeletal muscle target
-Decussation occurs in the medulla
Ascending Pathway
*Spinothalamic tract
Carries pain and temperature information to the cerebral cortex
- 1st order neuron: Sensory (peripheral) neuron extends form the source of the stimulus to the dorsal horn, synapses with interneuorn - 2nd order
-2nd order neuron: interneuron decussates to contralteral side and its axon enters white matter, the axon synapses in thalamus
-3rd order neuron: next interneuron relays the signal up to the cerebral cortex allowing conscious awareness of sensation
SYNAPSES AT DORSAL HORN AND THALAMUS
