Spinal Cord Gross Anatomy
How many interconnecting neurons form descending tracts? What are their names?
-2
-1st-order neurons (upper motor neurons)
-2nd-order neurons (lower motor neurons)
How many major functional groups are the descending spinal cord tracts divided into?
2; pyramidal and extrapyramidal tracts
Type of pathway that originates in the motor cortex and controls voluntary movement.
Pyramidal (direct) pathways
What is the primary function of the spinal cord?
To perform spinal reflexes
Which respiratory structure is innervated by spinal nerves C3-C5?
The diaphragm
Alpha motor neurons regulate _____ movements, while gamma motor neurons regulate _____ movements. (voluntary/reflexive)
voluntary, reflexive
What is the correct hierarchy of motor activity, from lowest to highest? (cerebellum, motor cortex, basal ganglia, spinal cord, premotor cortex)
Spinal cord, cerebellum, basal ganglia, motor cortex, premotor cortex
What type of skills do our pyramidal pathways regulate?
Fine, skilled actions (speech, writing, pincer grasp, etc.)
What is the correct pathway order of the reflex arc?
sensory input-->interneuron-->motor output; usually ipsilateral in the pathway
A lesion above the C4 nerve will result in:
Complete paralysis of the respirators
Stretch receptors found inside the skeletal muscles, sensitive to changes in muscle length.
Muscle spindles
Fx: sends a command down the spinal cord
1st-order neurons (UMN)
Which tract controls precise, skilled, voluntary movements, especially of the distal limbs and fingers?
Corticospinal tract
What is an example of a monosynaptic (one synapse) reflex?
The knee-jerk reflex; tendon tapping
Which syndrome presents with a loss of muscle power, reduced reflexes, muscular atrophy, and muscle flaccidity?
A LMN syndrome
The ventral horn of the spinal cord regulates _____ information, while the dorsal horn regulates _____ information. (sensory/motor)
motor, sensory
Travels from the spinal cord to the skelatal muscles to innervate; carries commands to the muscles.
2nd-order neurons (LMN)
Examples of this type of pathway include the rubrospinal tract, vestibulospinal tract, and the reticulospinal tract.
Extrapyramidal (indirect) pathways
What type of reflex is the withdrawal/ flexor reflex?
Polysynaptic (multiple synapses)
Bilateral loss of sensorimotor functions below the lesion site; functions above the lesion will be spared.
A complete spinal section
The posterior bundle of nerve fibers that carries sensory input into the spinal cord; all incoming afferent signals must enter through here.
Dorsal root
Originates in the brainstem; responsible for the involuntary, automatic control of muscle tone, balance, posture, and modulation of motor plans.
Extrapyramidal tracts
What is the difference in functioning between the lateral and anterior corticospinal tracts?
-Lateral corticospinal tract: distal limb control (fine, skilled movement)
-Anterior corticospinal tract: axial and trunk control (posture, balance)
Protective reflex; involves ipsilateral limb withdrawal, contralateral limb extension, and fibers that cross to contralateral interneurons
Crossed extensor reflex (e.g., your body engaging contralateral muscles to make sure you don't fall over)
Ipsilateral loss of movement and discriminative touch, and a contralateral loss of pain and temperature (spinothalamic pathways).
A spinal hemisection