The PNS Flashcards
What can the peripheral nervous system be split into and what is its function
Sensory (Afferent) and motor (efferent) Motor - autonomic and somatic autonomic - sympathetic and parasympathetic Communication between the CNS and body Movement and involuntary response
How many nerves does the PNS consist of
43 pairs 12 cranial 31 spinal (8 cervical 12 thoracic 5 lumbar 1 sacral 1 coccygeal)
Describe neuropraxia
Reversible conduction block
Demyelination. Axon intact. Endoneurium + connective tissue intact
E.g nerve compression
What distinguishes C1-7 from the other spinal nerves
They arise above their corresponding vertebra and do not always have mixed motor and sensory function
Describe axontomesis
Degeneration below and proximal to lesion. Nerve regrowth possible. Epineurium and perineurium intact
Demyelination. Axon loss. Connective tissue intact
Give differences in structure of the somatic, autonomic and sensory neurones
somatic - one neurone that transmits straight from the CNS to the effector site e.g. skeletal muscle
Autonomic - pre-ganglionic neurone, ganglion, and post ganglionic neurone to effector site e.g. vessels
sensory - one ganglion with a split axon from skin receptor to CNS
Where may sensory information arise from and how does it travel to the brain
conscious and visceral areas 1. periphery 2. dorsal root ganglion 3. brainstem/spinal cord Always stimulatory Uses ACh
Describe neurotmeses
Complete nerve division and disruption, no nerve growth
Demyelination. Axon loss. Connective tissue damaged- damage to epineurium
E.g laceration
What is somatic and visceral
somatic - skin and muscle
visceral - internal organs and glands
What is the somatic nervous system made up of
2 neurons, the upper motor neurone (CNS) and the lower motor neurone (PNS)
What is the role of the somatic nervous system
Efferent nerves
Voluntary control over skeletal muscle
voluntary or automatic
Describe the development of the somatic nervous system
The lower motor neurons originate form the basal plate
Multipolar neuron from the spinal cord innervate muscle fibres
One motor neuron will innervate many muscle fibres
What is the autonomic nervous system made up of
Efferent nerves and ganglia that stimulate effectors outside control e.g. heart rate
Involuntary effectors e.g. heart smooth muscle, glands
What can the autonomic nervous system be split into
Parasympathetic or sympathetic
Describe the autonomic pathway
- Hypothalamus
- Brainstem (parasympathetic) /spinal cord (sympathetic)
- Preganglionic neurone (myelinated)
- Ganglion (unmyelinated)
- Effector organ
Stimulatory or inhibitory
ACh or NA
Describe the somatic pathway
- Primary motor cortex
- Brainstem/ psinal cord
- NMJ
Describe the development of the autonomic nervous system
All derived from neural crest cells
Unmyelinated C fibres
What is a ramus
A division/ branch of a nerve
Motor and sensory nerves that exit form the roots
Describe the basic anatomy of the peripheral nervous system from the spinal cord
Adheres to the spinal cord via rootlets
dorsal (posterior) and ventral (anterior) roots
dorsal root ganglion
dorsal and ventral ramus of the spinal nerve
Which ramus from the spinal cord is the intercostal nerve
Ventral ramus of the spinal nerve
Where are the roots of the splanchnic nerve found
The tip of the sympathetic chain ganglion
What is the difference between ventral and dorsal root
ventral - somatic and autonomic motor neurones (Efferent)
dorsal - somatic and autonomic sensory neurones (afferent), cell bodies in the dorsal root ganglion
What is a spinal nerve
The motor and sensory neurones of that spinal segment
What is the difference between dorsal and ventral rami
ventral - motor and sensory nerves innervating the rest of the body from the neck down
dorsal - motor and sensory nerves innervating the skin and back + deep back muscles
