Nervous System Flashcards
Central Nervous System (CNS)
brain and spinal cord
Peripheral Nervous System (PNS)
Everything that isn’t brain and spinal cord
Describe function of Spinal Cord
- Localized control - reflex activity (does not get back to brain)
- conduction of impulses to & from higher levels
Neuron
basic functional unit of the nervous system
Nerve
collection of axons located in PNS; will also contain supporting cells (Schwan cells) and CT (endoneurium, perineurium, and epineurium)
Tract
collection of neuronal cell processes traveling within the CNS
Ganglion
collection of neuron cell bodies outside of the CNS
Nucleus
collection of neuron cell bodies within the CNS
“Afferent”
- toward CNS
- sensory
“Efferent’
- away from CNS
- motor
Primary Afferent Neurons
- conduct sensory impulses from periphery into CNS
- pseudounipolar neurons
- come into the dorsal root and then the dorsal gray horn
Final Efferent Neurons
- conduct motor impulses from CNS to effector organ
- aka Lower Motor Neuron (LMN)
- take signal from ventral gray horn out the ventral root
Monosynaptic Patellar Reflex
- simplest kind of reflex
- involves a primary afferent neuron and a lower motor neuron
Interneurons
- relatively short neurons interposed between afferent and efferent neurons
- located entirely within CNS
- May be excitatory or inhibitory
Withdrawal Reflex
- local action
- nothing to do with pain (pain comes later)
Projection Neurons
- Located in CNS
- send axons longer distances than interneurons
- can be an ascending tract to the brain
- can come from the brain down as an Upper Motor Neuron (UMN)
ipsilateral
occurring on the same side of the body
contralateral
occurring on the opposite side of the body
somatic
main body mass
visceral
organs and blood vessels
General Somatic Efferent (GSE)
- multipolar neurons that supply most of the skeletal muscles of the body
- single neuron extends all the way from CNS to muscle fibers involved
General Visceral Efferent (GVE)
- multipolar neurons that supply smooth muscle, cardiac muscle, and glands
- form autonomic nervous system (ANS)
- consist of a 2-neuron chain between CNS and effector organ
General Somatic Afferent (GSA)
- pseudounipolar neurons that carry sensory info from somatic body systems (skin, musculoskeletal system, etc)
- cell bodies are located in sensory ganglia
General Visceral Afferent (GVA)
- pseudounipolar neurons carry sensory info from visceral body systems
- cell bodies located in sensory ganglia
Special Somatic Afferent (SSA)
Bipolar neurons that carry visual and auditory info
Special Visceral Afferent (SVA)
Bipolar and pseudounipolar neurons that carry taste and smell sensations
The epaxial region (area above transverse processes) has what type of spinal nerve branches?
dorsal branches
The hypaxial region (area below transverse processes) has what type of spinal nerve branches?
ventral branches
How many pairs of cervical spinal nerves are there?
8 pairs
How many pairs of thoracic spinal nerves are there?
13 pairs
How many pairs of lumbar spinal nerves are there?
7 pairs
How many pairs of sacral spinal nerves are there?
3 pairs
Describe a withdrawl reflex
- receptor gets signal
- primary afferent neuron picks up signal and takes to dorsal horn
- from dorsal horn, excitatory and inhibitory interneurons send signal to flexor and extensor muscles, respectively
- Flexors flex and Extensors extend and the paw is withdrawn
Basic make up of ALL spinal nerves
Dorsal root (sensory, afferent) and ventral root (motor, efferent) join to form spinal nerve which divides into dorsal branch (motor and sensory), ventral branch (motor and sensory), and communcating branch (ramus communicans)
