The peripheral nervous system Flashcards
What is the PNS divided into?
The somatic (voluntary) and autonomic (involuntary) nervous system
How can the autonomic nervous system be divided?
The sympathetic and parasympathetic nervous system
What are autonomic nerves also know as?
Visceral nerves
Visceral afferent carry info. from viscera - sensory
Visceral efferent are sympathetic (innervate viscera and periphery) or parasympathetic (viscera only)
What do the peripheral nerves include?
12 cranial nerves
31 pairs of spinal nerves
How can somatic nerves be divided?
Somatic afferent- sensory neurones
Somatic efferent- motor neurones
What is a dermatome?
An area of skin innervated by a single spinal nerve
What is a myotome?
A group of muscles innervated by a single spinal nerve
What is a ganglion?
A collection of cell bodies outside of the CNS
All afferent Have their cell bodies in spinal ganglia
What is a nucleus?
Collection of cell bodies in the CNS
What is a plexus?
Network of interconnecting nerves
What are the 3 layers of connective tissue in a peripheral nerve?
Epineurium- outermost layer, surrounds nerve
Perineurium- surrounds bundle of neurones (fascicles)
Endoneureum- surrounds neurone
How are peripheral nerves classified?
Based on conduction velocity (A, B or C with A the fastest)
Based on diameter (Roman numerals with I being largest)
Label the following and state what a leision at each letter would cause
V: loss of sensation in dermatome supplied by spinal nerve
W: weakness of muscle supplied by spinal nerve
X: combines effect of V and W
Y: loss of sensation in area supplies by that peripheral nerve
Z: weakness/ paralysis of muscle
What is most often a consequence of strain injury?
Spinal root and spinal nerve damage
E.g. herniated disk
What kind of injury can affect peripheral nerves?
Trauma or disease
What kind of injury can affect the brachial plexus?
Trauma to shoulder joint
How can sensory receptors be classified?
External
Exteroceptors: detect pain, temperature, touch and pressure
Internal
Proprioceptors: detect movement and joint position
Enteroceptors: detect movement through gut and blood pH
What are the different detection sensory receptors and what do they detect?
- Chemoreceptors- molecules binding to receptor
- Photoreceptor- light
- Thermoreceptor- temperature
- Mechanoreceptors- channel opening
- Nociceptors- pain
Where are proprioceptors found?
Found in joints, muscles and interface between muscles and bones in golgi tendon organs
What are different types of proprioceptors and what do they detect?
Muscle spindles: detect changes in muscle length
Golgi tendon organs: detect changes in tension in tendon
Joint receptors: found in joint capsules, detect start and end of movement
What is the neuromuscular junction?
Specialised synspase between motor neurone and muscle fibre
What is a motor unit?
Single motor neurone and al the muscles it innervates
How does a reflex work?
- Muscle spindle activated
- AP sent via afferent nerve towards spinal cord. Signal synapses onto LMN nerve
- LMN becomes active which contracts muscle
At the same time other interneurones inhibit the antagonistic muscle
What is lumbar spinal radiculopathy?
Also known as sciatica
L5 and S1 involved
What are causes of sciatica?
Narrowing of intervertebral formaina where nerve emerges (formainal stenosis)
Compression from herniated disk
Slippage of vertebrae (spondylolisthesis)
Maliganancy (metatstaic bone disease)
Arthritis
Bone growth
Piriformis syndrome (nerves compressed by contraction of piriformis muscle)
What are treatment options for sciatica?
Pain killers
Exercise and stretching
Epidural injection- delivered into caudal part of spine
Decompression surgery/ discectomy
How can you confirm a diagnosis of sciatica?
Straight leg raise test
test stretches the sciatic nerve
