Anatomy of the Somatic Nervous System Flashcards
Somatic vs autonomic
- Somatic = voluntary functions
- Autonomic = involuntary functions
3 divisions of autonomic nervous system
- Sympathetic (fight or flight)
- Parasympathetic (rest and digest)
- Enteric (gut)
Components of the peripheral nervous system
- 31 spinal nerve pairs
- 12 cranial nerve pairs
- Ganglia
- Nerve plexuses
- Enteric nervous system
What is a ganglion?
Swelling/bundle of neuronal cell bodies
What is a nerve plexus?
Network of nerves (carrying both afferent and efferent)
Components of a neuron (number of each present)
- Cell body (1)
- Dendrites (many)
- Axon (1)
- Terminal synapses (many)
3 main types of neurones
- Multipolar (efferent) = cell body at dendrite end
- Bipolar (relay or special sense) = cell body in middle of axon
- Pseudo-unipolar (sensory) = cell body branching off axon
Function of glial cells
Create optimum microenvironment for neuronal activity
4 main types of glial cells
- Astrocytes
- Microglia
- Ependymal cells
- Oligodendrocytes
Function of astrocytes
- Contribute to blood-brain barrier
- Provide structural and metabolic support
2 forms of microglia
- Resting (ramified)
- Activated
Function of microglia
- Phagocytosis
- Maintain brain homeostasis
Function of ependymal cells
- Line ventricles
- Synthesise cerebrospinal fluid
Function of oligodendrocytes
- Create myelin sheath around CNS neurones
- Provide metabolic support and electrical insulation
Function of Schwann cells in myelinated and unmyelinated neurones
- Myelinated
> Create myelin sheath around PNS neurones
> Provide metabolic support and electrical insulation - Unmyelinated
> Cells have a more supportive role
What is myelin?
Lipid sheath 0.5-2.5µm thick
Function of myelin sheath
- Increase speed of conduction
- Provide protection
- Structure support
What do the sensations of the SNS provide?
- Awareness of the sensory world around us
- Accurate location of sensations throughout body
What is proprioception?
Awareness of the body position in 3D space
Where are the cell bodies of sensory somatic neurones found?
Dorsal root ganglion
Where are the cell bodies of motor somatic neurones found?
Ventral horn of spinal cord
Where are the cranial nerve nuclei found?
Brainstem
What are the 3 protective layers surrounding axon bundles?
- Endoneurium
- Perineurium
- Epineurium
What does the endoneurium surround?
Axons
What does the perineurium surround?
Bundles of axons (makes fascicles)
What does the epineurium surround?
Bundles of fascicles (makes nerve)
