D3 Introduction to nervous system Flashcards
anatomic divisions
- central nervous system (CNS): brain & spinal cord
- peripheral nervous system (PNS): nerves & ganglia
functional subdivisions
- somatic nervous system
- autonomic nervous system
somatic nervous system
- “outer shell” exposed to world
- conscious perception & control
- body wall & limbs, skeletal muscle only
autonomic nervous system
- “inner guts”; internal functions
- subconscious control
- cardiac muscle, smooth muscle, glands (GI, heart, lungs, etc)
functional classifications of neurons
- motor neurons
- sensory neurons
nerve fibers
- long processes of neurons
- are microscopic
- bundle up to form nerves
nerves
- nerve fibers & connective tissue (bundled up)
- only in the PNS
- most are mixed (sensory & motor fibers)
ganglia
- collection of neuron cell bodies in the PNS
- multipolar & pseudo-unipolar neuron clusters
origin of CNS
- formed form the embryonic neural tube
- cranial 2/3 of neural tube = brain
- caudal 1/3 = spinal cord
- ganglia derived from neural crest cells
3 parts that somites differentiate into in the trunk
1) Dermatomes: dermis of the skin - on the back
2) Myotomes: skeletal muscles
3) Sclerotomes: bones (ribs & vertebrae)
dermatome
an area of skin that is mainly supplied by a single spinal nerve
myotome
group of muscles that a single spinal nerve root innervates
sclerotome
area of a bone innervated from a single spinal segment
motor neurons
- project from the CNS
- multipolar cells in gray matter of spinal cord
- innervate (supply) an effector (eg a muscle or gland)
sensory neurons
- project to CNS
- eg dorsal root ganglion (pseudounipolar) cells
- bring information from the periphery (eg - skin) to the CNS
gray matter in CNS
- contains cell bodies of neurons
- organized into clusters of cells called nuclei
- forms an “H” shape in spinal cord, w/ 2 dorsal (posterior) horns, 2 ventral (anterior horns) and sometimes little bulges in center that are 2 lateral horns
dorsal (posterior) horn in gray matter
concerned w/ sensory processing
ventral (anterior) horn in gray matter
provides motor output (reflex and voluntary control)
lateral horn in gray matter
provides visceral motor (autonomic) output
white matter in CNS
- axons wrapped by fatty myelin
- surrounds the “H-shaped” gray matter
- cell bodies of neurons absent
- contains tracts, w/ many nerve fibers
nerves in CNS
- nerves are found only in the PNS
- there are NO nerves, only tracts, in the CNS
intervertebral foramina
- holes formed between adjacent vertebrae
- space for spinal nerves to leave the vertebral canal
afferent nerve fibers
- “affect = feeling”
- “feel” something, then carry that info (impulses) to the CNS
efferent nerve fibers
- “effect = making something happen”
- carry impulses from CNS to effectors (muscles, glands, etc - structures that perform an action)
somatic afferents
afferent nerve fibers that relay info from the body wall and limbs to the CNS
somatic efferents
efferent nerve fibers that relay info from CNS –> the body wall and limbs
visceral efferents
efferent nerve fibers that relay info from CNS –> smooth muscle, glands, and cardiac muscle
spinal cord segments
8 cervical segments (C-1 to C-8)
12 thoracic segments (T-1 to T-12)
5 lumbar segments (L-1 to L-5)
5 sacral segments (S-1 to S-5)
1 coccygeal segment (Co-1)
cauda equina
- called cauda equina b/c it resembles a “horse’s tail”
- bushy structure within vertebral canal formed by long dorsal and ventral roots gathered together
- dorsal and ventral roots very long below the end of the spinal cord
