The Somatic Nervous System Flashcards
What are the two subsections of the somatic nervous system?
Motor - regulates voluntary movement via skeletal muscle.
Sensory - transmits general sensation to the CNS.
What are the different types and examples of neurons?
Unipolar - cranial and spinal ganglia.
Bipolar - retinal neurons.
Pseudounipolar - sensory ganglia.
Multipolar - in the CNS.
How are nerves packaged?
Endoneurium - packages nerve fibres into fascicles.
Perineurium - packages groups of fascicles.
Epineurium - packages groups of perineuriums.
What can histology be used to see in nerves?
Axons and fascicles.
Not myelin sheaths.
What spinal plexuses are there?
Cervical - C1-C4.
Brachial - C5-T1.
Lumbosacral - L1-S4.
Coccygeal - S5.
T2-T12 have no plexus.
Describe the sensory and motor fibres in the spinal nerve.
Roots - sensory OR motor.
Spinal nerves and rami - sensory AND motor.
The spinal nerve exits through intervertebral foramen.
What is myelin sheath?
A lipid and protein substance.
Secreted by Schwann cells around some axons.
Increases the velocity of impulse conduction by insulation.
Define dermatome.
An area of skin supplied by a single spinal nerve.
Define myotome.
A part of muscle supplied by a single spinal nerve (one muscle myotome may involve several spinal segments).
What are important dermatomes?
T2 - sternomanubrial joint.
T4 - nipple.
T10 - umbilicus.
L1 - pelvic area.
What are clinical examples of muscle and nerve damage?
Wrist drop - radial nerve palsy affects the posterior arm and forearm muscles.
Foot drop - damage to the nerve that supplies the anterior compartment of the leg.
Winged scapula - damage to the nerve supplying the serratus anterior.
What do dorsal and ventral rami innervate?
Dorsal - posterior trunk.
Ventral - anterolateral trunk and limbs.
Where are there single cutaneous nerves?
The thorax and abdomen.
Describe the effect of dermatome and spinal nerve damage.
Reduced sensitivity.
Adjacent spinal nerves need to be damaged for complete sensation loss.
Damage near the spinal cord tends to affect individual nerve roots.
Describe dermatomes in the limbs.
Follows a different pattern than the trunk.
An overlap in nerve supply between adjacent dermatomes.
