spinal cord and nerves

how many pairs does spinal nerves have

31 pairs

cervical enlargement

Nerve fibers supplying the Upper limbs enter/exit.

lumbosacral enlargment

Nerve fibers supplying the Lower limbs enter/exit.

conus medullaris

tip is the inferior end of the spinal cord; extends to L2.

cauda equina

Horse’s tail; lumbosacral roots

filum terminale

Prolongation of pia mater

dura mater

Superficial layer; thickest; forms that thecal sac surrounding the spinal cord; continuous to dura of brain

arachnoid mater

Middle layer; very thin.

pia mater

Deepest layer; bound tightly to spinal cord’s surface.

reflex arc

an automatic response to a stimulus; unconscious thought.

Monosynaptic Reflexes

without interneurons

polysynaptic reflexes

has interneurons

stretch reflex

reflex contraction of muscles in response to stretching of that same muscle.

three layers of connective tissue:

endoneurium, perineurium, and the epineurium

the endoneurium

(innermost) surrounds each axon, or nerve fiber, and its Schwann cell sheath

perineurium

surrounds groups of axons to form nerve fascicles

epineurium

(outermost) binds the nerve fascicles together to form a nerve

ascending pathways

Carry sensory information to the brain.

descending pathways

Carry motor commands from the brain to the body.

the brain homunculus

portrays the anatomical divisions of the primary motor cortex and the primary somatosensory cortex.

spinal stenosis

spinal cord disorder; Narrowing of the spinal canal compressing nerves; causes pain, numbness, or weakness in the neck or lower back.

encephalitis

Brain inflammation caused by viruses or, less commonly, bacteria; symptoms include fever, coma, and seizures.

meningitis

Inflammation of meninges due to infection; symptoms include stiff neck, headache, fever; severe cases lead to paralysis or death.

rabies

Viral disease from animal bites; affects brain and nerves, causing aggression, paralysis, and death if untreated.

tetanus

Bacterial toxin affects motor neurons, causing rigid muscles ("lockjaw"); can lead to fatal respiratory spasms.

multiple sclerosis

Autoimmune disease damaging nerve sheaths; symptoms include tremors, speech issues, and exaggerated reflexes.

anesthesia

Loss of sensation, either pathological or induced for medical procedures.

neuritis

Inflammation of nerves; can cause motor function loss (motor nerves) or loss of sensation (sensory nerves).

neuralgia

Nerve pain with spasms or stabbing sensations; often due to inflammation or nerve damage.

sciatica

Pain radiating down the back of the leg from the sciatic nerve; often caused by a herniated lumbar disk.

leprosy

Bacterial disease causing skin and nerve damage; leads to disfiguring lesions and tissue death.

herpes

Virus causing painful skin sores (e.g., cold sores, shingles); different forms can attack sensory ganglia

poliomyelitis

Viral CNS infection damaging motor neurons; causes paralysis and muscle atrophy.

diabetic neuropathy

Nerve damage from high blood sugar levels; affects extremities with pain, numbness, and weakness.

charcot-marie-tooth disease

Hereditary disorder causing progressive nerve damage and muscle weakness.

neurofibromatosis

Genetic condition causing benign tumors in nerve tracts and skin growths.

myasthenia gravis

Autoimmune disorder affecting nerve-muscle communication; leads to fatigue and paralysis.