Spinal Cord Flashcards
Dura Mater
Outermost and toughest layer
Surrounded by epidural space, fat filled space
Arachnoid mater
Between the subarachnoid mater and dura mater
pia mater
The pia mater tightly adheres to the spinal cord, but between it and the arachnoid mater is a fluid-filled cavity, the subarachnoid space
subarachnoid space
Filled with cerebrospinal fluid (CSF)
provides a protective cushion around the spinal cord and the brain
Between pia mater and arachnoid mater
central canal
a narrow passageway in the spinal cord
allows for the circulation of CSF
Order of spinal cord
Epidural space
Dura Mater
Arachnoid mater
Subarachnoid mater
Pia mater
Where does spinal cord begin?
medulla oblongata of the brain
Where does spinal cord end?
conus medullaris, cone-shaped termination of the spinal cord
Why does the spinal cord does not extend the full length of the vertebral canal in newborns and adults?
Because the vertebral column’s growth outpaces the spinal cord
Filum terminale
This narrow band tethers the spinal cord to the sacrum and coccyx
Extension of pia mater
denticulate ligaments
20 paired lateral extensions of pia mater along the length of the spinal cord
provide further stability for the spinal cord
Cervical enlargement
Lumbar enlargement
Where are spinal Nerves Roots
from the right and left sides of the spinal cord
Where are spinal Nerves Roots
from the right and left sides of the spinal cord
PNS
What are some types of spinal nerves?
cervical, thoracic, lumbar, sacral, and coccygeal spinal nerves
cauda equina
A bundle of conus medullaris, lumbar, sacral, and coccygeal spinal nerves pass through the vertebral canal
What are 3 parts of spinal cords?
central canal, the gray matter, and the white matter.
central canal
CSF-filled
runs through the center of the whole spinal cord and connects to the brain’s ventricles
What type of neurons is in white matter?
myelinated axons
What are the things that are found in the White matter?
anterior median fissure.
dorsal, lateral, and ventral columns.
corticospinal tracts (ventral column)
spinothalamic tract (lateral columm)
Functions of corticospinal tracts
largest descending tracts
carry information from the cerebral cortex down to the motor neurons that originate in the spinal cord
spinothalamic tract
ascending tract
its neurons carry pain and temperature signals from the spinal cord upward to the thalamus of the brain.
Where is the corticospinal tracts?
Within the ventral column
Where is the spinothalamic tract?
Within the lateral column
What are some types of neurons found in the gray matter?
Interneurons
Sensory neuron
Motor Neurons
What are things that are part of the gray matter?
Dorsal horn
Lateral horn
Ventral horn
Dorsal horn
Receive sensory information
Cell body of Interneurons that received sensory information
Somatic sensory region
visceral sensory region
Ventral horn
The cell body of interneurons that receives somatic motor signals
Lateral horn
the cell body of interneurons that receives and send visceral motor signals
How many pairs of spinal nerves innervate the body?
31 pairs of spinal nerves
Where are cervical spinal nerves?
C1-C8
Where is spinal nerves relative to vertebra?
For cervical: C5 spinal nerves exit superior to the C5 vertebra
For the remaining: Vertebra is superior to spinal nerves
only exception: C8 emerges superior to T1. There is no C8 vertebra.
How many thoracic spinal nerves?
12
How many Lumbar spinal nerves
5
How many sacral spinal nerves?
5
What are the nerves comprised of?
Neurons (Axons)
Connective tissue
Blood vessels
Dorsal root
Somatic sensory that are entering the dorsal horn of the spinal cord
Somatic motor that are traveling from the ventral horn
dorsal root ganglion
swelling within the dorsal root
Contains cell body of unipolar (or pseudounipolar neurons
Ventral root
contains only axons of motor neurons
Dorsal Ramus
contains somatic motor and somatic sensory neurons headed to or from the skin, muscle, and 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 rami
a pair of small branches that carry neurons to the smooth muscle, cardiac muscle, and glands of the body.
sympathetic ganglion
sympathetic ganglia are interconnected through vertical branches that run alongside the vertebra.
sympathetic chain
a distribution hub for visceral neuron. Branches throughout send axons to the various visceral targets. Visceral sensory neurons return along the same path.
The visceral motor division of the spinal cord is also known as
Autonomic nervous system (ANS)
Autonomic nervous system (ANS) has 2 divisions which are
- The sympathetic nervous system: preparing the body for action, the “fight or flight response.” These visceral motor neurons begin their path in T1-L2 spinal regions and spinal nerves.
- The parasympathetic nervous system: homeostasis, a state of “resting and digesting.” found in spinal nerves S2-S4 as well as portions of the brainstem and cranial nerves.
Intercostal nerves
Ventral rami of thoracic spinal nerves continue around the lateral sides of the body
cervical plexus
is formed from ventral rami of cervical spinal nerves, and it innervates many of the neck muscles.
brachial plexus
formed from ventral rami of C5-T1 spinal nerves, and it supplies the upper appendage.
lumbosacral plexus
formed from ventral rami of L2-S4 spinal nerves, and it supplies the lower appendage.
How many neurons involved in descending pathway?
2
Upper motor neuron
Lower motor neuron
What is decussation
Cross midsagittal plane to the contralateral side
Upper motor neuron
one neuron travels within the corticospinal tract
Not truly a “motor” neuron, this cell is an interneuron of the CNS that has its cell body in the cerebral cortex and its terminal in the ventral horn of the spinal cord.
Lower motor neuron
the second neuron in the pathway is the lower motor neuron (red arrow)
A true peripheral motor neuron, this neuron travels within the spinal nerve and eventually reaches its skeletal muscle target.
How many neurons are involved in ascending pathway?
3
1st order neuron
2nd order neuron
3rd order neuron
1st order neuron
the sensory (peripheral) neuron extends from the source of the stimulus to the dorsal horn, where it synapses with an interneuonr, the 2nd order neuron.
2nd order neuron
this interneuron decussates (crosses) to the contralateral side, and then its axon enters the white matter. From the white matter, the axon occupies the spinothalamic tract until reaching its synapse in the thalamus.
3rd order neuron
the next interneuron relays the signal up to the cerebral cortex, allowing conscious awareness of sensation.
How could a motor neuron? be stimulated
from an interneuron in a polysnaptic reflex
from an sensory neuron in a monosynaptic reflex
from an upper motor neuron as part of a descending pathway
Withdrawal reflex
Although your brain may be informed of the pain, the withdrawal happens before you know it’s happening
Polysynaptic reflex
The stimulus travels along a sensory neuron that synapses with one (or several) interneurons in the dorsal horn. Several sets of motor neurons are simulated in the muscles of your arm and shoulder that withdraw from the painful stimulus. At least two synapses are present, making this a polysynaptic reflex.
monosynaptic reflexes
he sensory neuron synapses directly with the ventral horn’s motor neurons.
No interneurons are involved in monosynaptic reflexes
