Peripheral Nervous System Flashcards
Somatic afferent nerves convey information from
Skin, skeletal muscle and joints
Somatic afferent nerves convey information to
Skeletal muscles
What is a dermatome
An area of skin that is supplied by single spinal nerve
What is a myotome
Group of muscles innervate by a single spinal nerve
How can myotomes be tested
Most individual muscles of the body are innervate by more than one spinal-cord level so the evaluation of myotomes is usually accompanied by testing movements of joints or muscle groups
How can the dermatome be tested
There is an overlap between the distributions of dermatomes but usually a specific region within each dermatome can be identified as an area supplied by single spinal-cord level
Testing touch in the autonomous zones in a conscious patient can be used to localised lesions in a specific spinal nerve or to a specific level of the spinal-cord
What is the viscera
Thoracic
Abdominal
Pelvic
Where do you sympathetic efferent nerves innervate
Viscera ( organs) and periphery( vascular urge and sweat glands)
Where do parasympathetic nerves innervate
Viscera only
What is a ganglion
A collection of cell bodies outside the central nervous system
What is the nucleus
A collection of cell bodies inside the central nervous system
What is a plexus
A network of interconnecting nerves
All afferent fibres have a cell bodies in the
Spinal ganglia
Visceral efferent fibres synapse in the
Peripheral ganglion
What is an axon covered in
Endoneurium
What does a fascicle consistent of
Many axons
What is the fascicle covered in
Perineurium
Many fascicles form a
Nerve
What is a nerve covered in
Epineurium
What are the two classification system of peripheral nerves
Conduction velocity Axonal diameter( sensory only)
Classification system based on conduction velocity
Uses letters A,B and C with A being fastest
Classification system based on axonal diameter
Uses Roman numerals I- IV with I being the largest diameter
What are Exteroceptors
To text pain touch temperature and pressure
What are proprioceptors
Detect movement and joint position.
They can be found in muscle spindles - detect changes in muscles length
They can be found in golgi tendon organs- detect changes in tension in tendons
They can be found in joint receptors - found in joint capsules and detect start and end of movement
What are enterorepetors
Detect movement through gut and blood pH
What is an example of external sensory receptors
Exteroceptors
What is an example of internal sensory receptors
Proproceptors and enteroceptors
Chemoreceptors
Detect molecules which binds to receptor , for example in olfactory bulb
What are photoreceptors
Detect light in the retina
Was are thermoreceptors
Detect temperature in the skin
What are mechanoreceptors
Mechanical opening of iron channel for example touch receptors in the skin
Nociceptors
Detect tissue damage, interpreted as pain
What is the neuromuscular junction
Specialise junction between a motoneuron and a muscle fibre
What is the motor unit
A single mention your own together with all the muscle fibres that it innervates
What is a ligament
Connects bone to bone
What is the tendon
Muscle to bone
Knee-jerk reflex
When you sweat the patella ligament you got the knee jerk reflex but you’re actually hitting the quadriceps of thigh
What is a reflex action
An involuntary coordinated pattern of muscle contraction and relaxation elicited by peripheral stimuli
Process of the knee jerk reflex
Stretching stimulate sensory receptor (muscle spindle)
Sensory neuron is activated
Within integrating centre of the spinal-cord sensory neuron activates the motoneuron
The motorneuron is activated
Effector which is the same muscle contracts and believes the structuring
The motor neurone to antagonistic muscle is inhibited
What are the exceptions to the rule of adrenaline being release at post ganglionic neurones
Sweat glands and blood vessels which have sympathetic innervation where ACh is the neurotransmitter released
Parasympathetic outflow
Craniosacral ( brainstem cranial nerves 3,7,9,10 and S2-S4 spinal segments)
Sympathetic outflow
Thoracolumbar outflow T1-L2
Visceral sensory
Relays sensory information from the core
Pain , fullness,blood pressure
T1-L2, S2-S4 and cranial nerves 9 and 10
Visceral motor
Outflow to core and body wall
Controls pupils, sweat glands, salivary glands and heart muscle and airways
Thoracolumbar ( T1-L2 ) and craniosacral outflow
Look at anatomy of sympathetic outflow to periphery
Look at anatomy of sympathetic outflow to periphery
White ramps communicants
Called white as the pre ganglionic neurone has a myelin sheath
Grey ramus communicants
Post ganglionic neurone is non myelinated and so when it goes out of the sympathetic chains , it goes via greys ramus communicans
Sympathetic outflow to heart
Comes out of T1-T4 and the collection of nerves that surround the heart is known as the cardiac plexus
Anatomy of sympathetic outflow to the viscera
Thoraccic nerves go into sympathetic chains but no synapse occurs in sympathetic chain. Pre ganglionic nerves travel straight down to the gut in things called sphlancic nerves where they collect and form greater, lesser and least sphlancic nerves. When they get to organs, they synapse in pre aortic Ganglia where you find cell bodies of post ganglionic neurones ( eg. In gut)
Anatomy of parasympathetic outflow to viscera
Have specialised ganglia where pre and post ganglionic nerves synapse, usually in CNS
