Somatic Nervous System Flashcards
Describe the classification of neurons.
Bipolar neuron - 2 long axons coming from the cell body.
Pseudounipolar neuron - Axon extends from cell body and then splits into two.
Multipolar neuron - has dendrites coming from cell body and a long axon.
Anaxonic neuron - has no clear axon.
Describe the functions of the somatic nervous system.
The motor fibres in the somatic nervous system regulate voluntary control (e.g. in skeletal muscle).
The sensory fibres transmit general sensation to the CNS (e.g. pain, touch, temperature, proprioception etc).
Describe the functions of the visceral nervous system.
The motor fibres in the visceral nervous system are responsible for involuntary control (e.g. smooth muscle and glands).
The sensory fibres of the visceral nervous system are responsible for visceral pain, chemoreception and stretch reception.
Describe the difference between dermatomes and myotomes.
A dermatome is an area of skin supplied by a single spinal nerve.
A myotome is a part of a muscle supplied by a single spinal nerve.
Describe the relevance of dermatome and myotome in clinical practice.
These are useful for testing motor or sensory loss.
Can be used for localising spinal cord pathologies and locating where pain is coming from, relating to one specific spinal segment.
Describe the structure of a spinal nerve.
Spinal nerves exit through the intervertebral foramen.
They are part of the peripheral nervous system in terms of location.
The spinal nerve is a mixture of both sensory and motor fibres.
Describe the implications of damage to the roots on the spinal nerve.
Damage to dorsal root causes sensory loss.
Damage to ventral root causes motor loss.
Describe the implications of damage to the spinal nerve (junction where both roots meet).
Damage to the spinal nerve region would cause both sensory and motor loss.
Describe the implications of damage to the rami of the spinal nerve.
Damage to the ventral ramus would cause motor and sensory loss of ANTEROLATERAL TRUNK.
Damage to the dorsal ramus would cause motor and sensory loss of the back.
Describe the components of the somatic reflex arc.
The somatic reflex arc is important for sensory detection, it interprets the sensory input in the CNS and initiates a motor response.
Describe the structure of the somatic reflex arc.
An external stimulus occurs, causing an afferent (sensory) neuron to travel along an axon to the CNS where it synapses with an efferent (motor) neuron that travels back to the effector (e.g. muscle) that initiates a motor action.
Describe the concept of “wrist drop” in relation to the somatic nervous system.
The extensor muscles of the forearms that extend the wrist and elbow are innervated by the Radial Nerve.
With “wrist drop”, this function now ceases and the wrist won’t extend - extensor weakness.
Possible causes:
Damage to lower motor neurons on their peripheral axons - this leads to muscle paralysis or weakness.
Most likely a radial nerve injury.
Describe the concept of “foot drop” in relation to the somatic nervous system.
The foot is not able to dorsiflex, this indicates that the problem is coming from anterior component of leg.
The nerve that innervates this compartment must be damaged. (sciatic N?)
Describe the concept of a “winged scapula” in relation to somatic nervous system.
A winged scapula is caused by damage to the nerve that supplies the serratus anterior.
(long thoracic nerve).
