Module 3 - Spinal Cord Flashcards
The cervical enlargement:
-supplies innervation to the upper extremities
-particularly large because there is greater control over the fine musculature of the upper limbs, particularly of the fingers
The spinal cord ends inferiorly at the ______
conus medularis (end of spinal cord)
The spinal cord sits within the ______ foramen while each spinal nerve travels through a(n) ________ foramen
vertebral; intervertebral
The cell bodies of sensory neurons traveling from the periphery to the spinal cord are located in the _________
dorsal root ganglion
Anterior horn
-Motor only
Ventral ramus
carries both sensory and motor information from or to the extremities and anterior trunk.
Dorsal ramus
carries both sensory and motor information from or to the posterior trunk
Posterior horn
-Sensory only
Ventral root
contain only the axons of motor neurons carrying information away from the spinal cord to muscles and glands.
Dorsal column
-Sensory only
Spinal nerve
-Both motor and sensory
Dorsal root
Contain only the axons of sensory neurons carrying information to the CNS from the periphery
The long bundle of nerves extending inferiorly from the spinal cord within the vertebral foramen is called the ____ _______
cauda equina
How many spinal nerves emerge from the cervical?
8 spinal nerves
How many spinal nerves emerge from the thoracic?
12 spinal nerves
How many spinal nerves emerge from the lumbar?
5 spinal nerves
How many spinal nerves emerge from the sacral?
5 spinal nerves
How many spinal nerves emerge from the coccygeal?
1 spinal nerve
Spinal Nerve
-Formed by the merging of the dorsal and ventral roots
-carry both sensory and motor axons
White matter
-Composed of myelinated axons
-the surrounding area of the “butterfly”
-separated into columns
Gray matter
Composed primarily of cell bodies and dendrites
Central canal
Located in the center of the spinal cord and contains cerebrospinal fluid
Lateral horn
Only present in the thoracic region (and less prominently in the very upper lumbar region)
How many bones are in the cervical portion of the vertebral column?
7
How many bones are in the thoracic portion of the vertebral column?
12
How many bones are in the lumbar portion of the vertebral column?
5
How many fused bones make up the sacrum in the vertebral column?
5 fused vertebrae
How many fused bones make up the coccyx in the vertebral column?
3-5 fused vertebrae
Vertebral foramen
canal through which the spinal cord passes
Intervertebral foramen
opening located between adjacent vertebrae for exit of a spinal nerve
How are the spinal nerves numbered?
Superior to inferior positions
The lumbar enlargement:
-will innervate the muscles of the lower extremity
-not as significant in appearance because there is less fine motor control of the lower limbs.
Filum terminale
anchors spinal cord to coccyx
Gray commissure
a thin strip of gray matter that surrounds the central canal of the spinal cord and, along with the anterior white commissure, connects the two halves of the cord.
Posterior spinal artery
-two arteries
-supplies blood to the posterior 1/3 of the spinal cord
Anterior spinal artery
-single artery
-supplies blood to the anterior 2/3 of the spinal cord
Ascending pathways
-carry sensory information up to the brain
-The posterior columns are composed of axons of ascending tracts
Descending pathways
-carry motor commands from the brain.
Most pathways of the spinal cord decussate at some point, meaning they:
-cross to the contralateral side from where they originated
-That means that the right side of the brain is processing incoming or outgoing information from the left side of the body, and the left side of the brain is processing incoming or outgoing information for the right side of the body.
Dorsal column medial lemniscus pathway
mediates fine touch, deep pressure sensation and proprioception
Anterolateral pathway/ALS pathway
Ascending sensory pathway in the spinal cord and brainstem that carries information about pain, temperature, and crude touch
Spinocerebellar pathway
-proprioceptive and muscle sense information
-All information stays ipsilateral
-dorsal carrying information about the action of individual muscles
-ventral portion carrying information about the position of the limb as a whole
Upper motor neuron
-Cell body in either the cerebral cortex or a brainstem nucleus
-excites or inhibits the activity of the lower motor neuron
Lower motor neuron
-Cell body in either the anterior horn of the spinal cord or a brainstem cranial nerve nucleus
-The lower motor neuron is always excitatory –> axon connects directly to skeletal muscle fibers
Corticospinal tract
-largely contralateral; axons cross the midline of the brain stem or spinal cord and synapse on the opposite side of the body.
-Therefore, the right motor cortex of the cerebrum controls muscles on the left side of the body, and vice versa.
What does it mean when something synapses?
A connection formed between the axon of one neuron and the dendrite of another, allowing communication when the electrical signal is converted to a chemical signal
Reflex arc
Rapid, automatic, involuntary reactions of muscles to a stimulus
Ipsilateral
Both the receptor and effector organs are on the same side
Contralateral
sensory impulses from a receptor organ cross over through the spinal cord to activate effector organs on the opposite limb
Monosynaptic reflex
Reflex pathway with only one synapse between the sensory and motor neurons (ex: knee-jerk).
Stretch reflex
the contraction of a muscle in response to stretch of that muscle
Muscle Spindle
Monitors stretch of a muscle and speed of stretch
Polysynaptic reflex
at least one interneuron between sensory neuron and motor neuron
Withdrawal reflex
-would occur with any reflexive response to pain or extreme temperatures
-Interneurons receive the sensory information and stimulate the motor
neurons to direct flexor muscles to contract. Simultaneously, extensor muscles are inhibited so that the traumatized body part may be quickly withdrawn from the harmful stimulation
Golgi tendon reflex
-Monitor tension within the tendons
-Nerve impulses signal interneurons in the spinal cord, which in turn inhibit the actions of the motor neurons
Golgi tendon organs (GTOs)
nerve endings located within tendons near a muscle–tendon junction
