Topic 12 - Spinal Cord

begins as a straight line that gets more complex.

How does the development of the nervous system begin?

ectoderm

Where do nerve cells originate from in embryology?

begins as a straight line that gets more complex.

How does the development of the nervous system begin?

ectoderm

Where do nerve cells originate from in embryology?

The cells come together to form the neural groove, which becomes the neural tube, and eventually develops into the CNS.

What forms as the cells come together in the early stages of development?

The neural crest forms around the neural tube and will become parts of the PNS as it separates away.

What is the role of the neural crest in embryology?

the anterior tube becomes the brain and the posterior tube becomes the spinal cord.

What happens around day 25 of embryonic development?

CNS

Spinal cord and Brain

PNS

neural tissue that has left the spinal cord or brain

Visceral

innervates viscera

Somatic

innervates skeletal muscle

cervical enlargement (C4–T1) and the lumbar enlargement (T9–T12)

What are the two enlargements of the spinal cord?

The medullary cone is the tapered end of the spinal cord, located at L2.

What is the medullary cone?

also known as the "horse’s tail," is a bundle of nerve roots below L2

What is the cauda equina?

anchors the spinal cord to the coccyx.

What is the function of the filum terminale?

an opening in the spinal cord connected to the 4th ventricle, filled with cerebrospinal fluid (CSF).

What is the central canal of the spinal cord?

allows decussation (crossing over) to happen in the spinal cord.

What is the function of the gray commissure in the spinal cord?

a groove that separates the right and left sides of the spinal cord.

What is the posterior median sulcus?

a deep groove that separates the right and left sides of the spinal cord.

What is the anterior median fissure?

Signals synapse in the gray matter and travel up or down in the white matter.

Where do signals synapse in the spinal cord, and how do they travel?

contains motor signals that leave the spinal cord.

What is the function of the anterior horn in the spinal cord?

contains sensory signals that enter the spinal cord.

What is the function of the posterior horn in the spinal cord?

The lateral horn contains autonomic signals for the sympathetic nervous system.

What does the lateral horn of the spinal cord handle?

Anterior Funiculus

descending pathway for motor control

Posterior Funiculus

ascending pathway for sensory information

Lateral Funiculus

autonomic pathway for sympathetic system

Spinocerebellar tract

axons leave dorsal root ganglion and go up
the spinal column to the medulla, they synapse with another neuron and cross the midline to go to the thalamus, another synapse to get another neuron to go to the cerebral cortex (touch, proprioception)

Spinothalamic tract

axons leave dorsal horn and synapse in the
spinal cord to cross midline, they synapse the third time in the thalamus (pain and temperature)

spinal cord involvement

Trigeminal pathway acts the same from the face without

upper motor neurons

Primary motor cortex has 2 tracts of

The corticospinal tract synapses with lower motor neurons in the spinal cord and is contralateral. It controls limbs (lateral) and axial muscles (anterior).

What is the corticospinal tract and its function?

The corticobulbar tract synapses with lower motor neurons in the brainstem to control muscles of the head, neck, and face. It involves cranial nerves V, VII, X, XI, and XII.

What is the corticobulbar tract and its function?

There are 31 spinal nerves: C1-C8, T1-T12, L1-L5, S1-S5, and the Coccyx.

How many spinal nerves are there and what are their regions?

All spinal nerves are mixed nerves, meaning they contain both sensory and motor fibers.

What type of nerves are all spinal nerves?

Damage causes paresthesia (abnormal sensations like tingling or numbness).

What happens if the dorsal root or posterior funiculus is damaged?

paralysis

What happens if the ventral root or anterior funiculus is damaged?

causes both sensory and motor deficits.

What occurs if the spinal nerve or spinal cord is damaged?

Intrinsic

born with (blinking, sucking) or Acquired - learned (riding a bike)

Somatic

muscle (stretch reflex) or Visceral – organs (blood pressure)

Monosynaptic

1 synapse (fast) or Polysynaptic – multiple synapses (slower)

Ipsilateral

same side of the body or Contralateral – opposite side of the body

Spinal

decisions from the cord (stretch reflex) or Cranial – decision made in the brain (blinking)

Stretch reflex

muscle contraction in response to stretch

Flexor reflex

quick motion usually due to pain

Crossed-extensor reflex

opposite side reflex often for equilibrium

located in the dorsal root ganglion (unipolar) and send information to the spinal cord or brainstem.

Where are first-order neurons located and what is their function?

mostly located in the dorsal horn and send information to the thalamus.

Where are second-order neurons located and what is their function?

take information from the thalamus to the cerebral cortex.

What is the function of third-order neurons?

Decussation is the crossing of afferent and efferent axons to the opposite sides of the body.

What is decussation in relation to spinal cord neurons?

Upper motor neuron

start of motor signal (pre central gyrus) and
synapse with lower motor neurons. Damage can lead to spacticity (hyperactive reflexes)

Lower motor neurons

starts with the neurons that will synapse
with the effector (muscle, gland) at ventral horn of spinal cord. Damage can lead to coma and neurosyphilis (hypoactive reflexes)