somatic nervous system Flashcards
Nervous system made up of
CNS (brain and spinal cord) and PNS (spinal nerves and cranial nerves)
axons in the CNS are called
tracts
cell bodies in the CNS are called
nuclei
axons in the PNS are called
nerves
cell bodies in the PNS are called
ganglia
Afferent
sensory axons that conduct towards CNS in dorsal root
efferent
motor axons that conduct away from CNS in ventral root
roots vs rami
roots are separated by afferent and efferent while rami are mixed (afferent, efferent) but separated by dorsal and ventral
dorsal rami supply…
the intrinsic muscles of the back (motor) and the skin of the back (sensory)
the ventral rami supply…
extrinsic muscles of the back, ventral muscles and the overlying parts of the dermatome.
the ventral primary and dorsal primary rami also carry…
postganglionic sympathetic axons for blood vessels, smooth muscle cells and glands
upper cervical dorsal rami
C1-suboccipital nerve; only motor. no cutaneous branches thus, there is no C1 dermatome
C2: motor and gives rise to greater occipital nerve which is a cutaneous nerve
C3: cutaneous branch is the lesser occipital nerve
plexus are made of up from the ventral primary rami. Name the plexus
cervical, brachial , thoracic intercostal, lumbar and sacral
cervical plexus
Consists of the ventral rami of C1-C4 spinal nerves. Peripheral nerves emerging from the cervical plexus provide cutaneous innervation to the back of the head, neck, shoulder, and upper thoracic region. They also provide motor innervation to muscles of the anterior neck and the diaphragm.
brachial plexus
Consists of the ventral rami of C5-T1 spinal nerves. Peripheral nerves emerging from the brachial plexus provide cutaneous and motor innervation to the skin and muscles of the upper limb
intercostal plexus
Consist of the ventral rami of T1-T11 spinal nerves that course within the intercostal spaces along the costal groove of their associated rib to innervate the skin and muscles of the intercostal spaces
lumbar plexus
Consists of the ventral rami of T12-L4 spinal nerves. Peripheral nerves emerging from the lumbar plexus provide cutaneous innervation to the skin of the lower abdominal wall, perineum, anterior thigh, and medial thigh. They also provide motor innervation to muscles of the perineum, anterior thigh, and medial thigh.
sacral plexus
Consists of the ventral rami of L4-S3 spinal nerves. Peripheral nerves emerging from the sacral plexus provide cutaneous and motor innervation to the skin and muscles of the lower gluteal region, posterior thigh, posterior leg, and foot.
sensory transduction: the different modalities
touch, pain, temperature, proprioception, vibration
afferent sensory information travels into the DRG and into the CNS (spinal cord) via a
1st order neuron.
how many neurons are there in sensory transduction
3- first order (goes into CNS–into cord). second order goes from cord to thalamus (dessucation occurs in second order in the cord). then third order originates in the thalamus and travels into the cerebral cortex (the humunculus)
neurons of output from motor cortex
upper motor neuron in primary motor cortex (in cerebral cortex) travels down to brainstem where it splits into a cranial nerve and a cortico-spinal tract and ends in the spinal cord. it meets there the lower motor neuron that exits through the ventral root into the spinal nerve.
neurons of output from motor cortex
upper motor neuron in primary motor cortex (in cerebral cortex) travels down to brainstem where it splits into a cranial nerve and a cortico-spinal tract and ends in the spinal cord. it meets there the lower motor neuron that exits through the ventral root into the spinal nerve.
how spinal nerves exit the IVF
CERVICAL : of the 8 cervical spinal nerves, the first 7 emerge superior to their corresponding vertebrae
C 8 spinal nerve emerges between vertebrae C7 & T1
THORACIC : all thoracic spinal nerves exit below their respective vertebrae, but still above their corresponding IVDs
LUMBAR : same as thoracic spinal nerves
the sacral level of the cord is at the
conus medullaris L1-L2
the cauda equina is located in the
lumbar cistern
in the middle of the cauda equina is the
filum terminale (pia mater)
in a newborn the cord (conus medullaris) ends at L3
important to know for anesthesia
layers of the meninges
Dura mater (removable), arachnoid mater(also removable to reveal subarachnoid space that contains CSF), pia mater (unremovable and makes up denticulate ligaments that separate ventral and dorsal roots of the spinal nerves)
best placement for lumbar puncture
below L2, L3-L4 is best (look for iliac crests which should be at the level of L4)
