Neuro - PNS Flashcards
Where do we have somatic afferent fibres?
Skin
Skeletal muscle
Joints
Where do we have somatic efferent fibres?
Skeletal muscle
What is a dermatome?
Area of skin that is innervated by a single spinal segment.
What is a myotome?
Group of muscle fibres supplied by a single spinal nerve
Where do sympathetic nerves innervate?
Core and periphery e.g. vasculature and sweat glands
Where do parasympathetic nerves innervate?
Periphery (viscera)
What is a ganglion?
Group of nerve cell bodies outside of the CNS
What is a nucleus?
Group of nerve cell bodies inside the CNS
Where are the cell bodies of all afferent fibres found?
Dorsal root ganglia/spinal ganglia
Where do visceral efferent fibres synapse?
Peripheral ganglia e.g. para or prevertebral fibres
How are peripheral nerves arranged?
Into fasciculi within the spinal nerve, among blood vessels
What is the outermost vascular layer?
Epineurium - covers the spinal nerve
What covers fascicles of peripheral nerves?
Perineurium
What covers neurones (above myelin)?
Endoneurium
What 2 classification systems do we have for peripheral nerves?
Speed
Diameter
What are the parameters for conduction velocity?
A (fastest)
B
C (slowest)
What are the parameters for axonal diameter?
I (biggest diameter)
IV (smallest diameter)
What does a larger diameter give?
Lowest stimulation threshold
What are the two ways we can classify receptors?
Location
Mode of detection
What are the sub categories for receptor location?
Internal
External
What are internal receptors?
Proprioceptors
Enteroreceptors (gut movement or blood pH)
What are external receptors?
Exteroreceptors (pain, temperature, touch, pressure)
What are chemoreceptors?
Detect molecules which bind to the receptor
What are photoreceptors?
Detect light
What are thermoreceptors?
Detect heat
What are mechanoreceptors?
Detect mechanical change e.g. pressure
What are nocireceptors?
Detect tissue damage (pain)
What is the purpose of proprioceptors?
Allows for self orientation and awareness of postitioning
What are the main types of proprioceptors?
Muscle spindle
Golgi tendon organ
Joint receptor
What do muscle spindles detect?
Changes in muscle length
What do Golgi tendon organs detect?
Tension e.g. in a tendon when stretched from flexion/extension
What do joint receptors detect?
Found in joint capsules - detect the start and end of a movement
What is a motor unit?
Smallest functional unit which can produce a force (single motor neurone with all of its muscle fibres)
What is the definition of a reflex?
Involuntary coordinated pattern of muscle contraction and relaxation elicited by peripheral stimuli
What is an example of a monosynaptic reflex?
Patella reflex
What are the steps of a reflex action e.g. the patellar reflex?
- Stretching stimulates sensory receptor
- Sensory neurone activated
- Motor neurone activated in integrating centre
- MN activated
- Effector contracts and relieves stretching
What may we also elicit along with effector muscle contraction?
Inhibition of the antagonist muscle causing the stretching
What sensations are relayed via the visceral sensory system?
Pain
Fullness
Blood pressure
Where do visceral sensory nerves enter the spinal cord?
T1-L2 and CN IX and X
Where do visceral motor nerves leave the spinal cord?
T1-L2
CN III, VII, IX, X
S2-S4
What do visceral afferent neurones innervate?
Core (PSNS+SNS) and wall (SNS only)
What are examples of some of the features controlled by the GVE neurones.
Pupil size
Calibre of airways
Sweat glands
Salivary glands
How do we describe the sympathetic outflow?
Thoracolumbar
How do we describe the parasympathetic outflow?
Craniosacral
What are the 2 ganglia involved with sympathetic outflow?
Prevertebral and paravertebral
Where are paravertebral ganglia located?
In the sympathetic trunks running parallel alongside the spinal cord
Where the prevertebral ganglia located?
There are 3 in the body:
Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
Describe the course of a sympathetic neurone at T5, innervating a structure at the same level?
Pre-ganglionic neurone emerges at T5, travels out via the ventral horn and via the white ramus communicans into the paravertebral ganglion where it will synapse and then the post ganglionic neurone will travel out to the mixed spinal nerve via the gray ramus communicans.
Describe the course of a sympathetic neurone at T5, innervating a structure at the level of C4
Pre-ganglionic neurone will travel out via the ventral horn and white ramus communicans, however may or may not synapse immediately. It will eventually synapse, however must travel up towards the level of C4 where it will then leave via the gray ramus communicans into the mixed spinal nerve
Describe the course of sympathetic neurones travelling to abdominal or pelvic viscera.
The preganglionic neurones will travel out via the white ramus communicans however will not synapse in the paravertebral chains. Instead, they travel as the greater, lesser and least splanchnic nerves and will synapse at one of the prevertebral ganglia before entering the viscera.
