Spinal cord Flashcards
Be able to describe afferents and efferents to the spinal cord
Afferent: taking information in; sensory system. Dorsal ascending pathways
Efferent: sending information out; motor system. Ventral descending pathways
Spinothalamic dorsal column: pain and temperature
dorsal medial lemiscus: proprioception, fine touch
Be able to describe primary afferent fibers and where the cell bodies are
Single cell that transmits sensory signal to the spinal cord (many located in tract of Lissauer)
Sensory cell bodies are located in the dorsal root ganglion
Type of cell body parallels type of information
Collaterals spread up and down the spinal cord
Be able to describe the relationship of sensory fiber size to conduction velocity and sensory modality and list fiber types in order of velocity
Less diameter = slower conduction velocity
In order of greatest to least conduction velocity:
A-alpha (proprioception)
A-beta (proprioception, superficial touch, deep touch, vibration)
A-delta (pain,cool temp,touch,itch)
C fiber (pain, warm temperature, itch): only fiber thats nonmyelinated
The larger the fiber the less stimulus required to cause an action potential
Be able to identify the gross anatomy of the dorsal and ventral roots
Outside vertebral column left (dorsal) far left-dorsal root ganglion thin area dorsal root, right (ventral) (long leg to short) Middle: tracts to arms and legs: fasciculus gracilis (medial) (legs) fasciculus cuneatus (lateral) (arms)
Be able to identify the gray matter and white matter of the spinal cord and identify why they are different
Gray matter: unmyelinated cell bodies and interneurons. In dorsal and ventral horn
White matter: myelinated axons
The location of grey and white matter is opposite that of the brain, where gray matter is peripheral in the brain but central in the spinal cord
Be able to describe and define the dorsal and ventral horn and identify their differences
Dorsal horn: sensory relay neurons receive sensory information sent to spinal cord
Ventral horn: contains cell bodies of lower motor neurons which innervate muscles
Be able to identify the rostro-caudal level of the spinal cord from cross-sections
Descending: cervical, thoracic, lumbar, sacral
Be able to identify the location of the autonomic nervous system and its subdivisions in the spinal cord
Sympathetic (fight or flight): in thorax where organs are (T1-L3). Short preganglionic (Ach) and postganglionic (Nor)
Parasympathetic (rest and digest): Occular nerve, facial nerve, glossopharyngeal nerve, and vagus nerve. Sacral (S2-S4). Long preganglionic short postganglionic (both ACh)
Be able to define sympathetic afferents in spinal cord and identify their location
All nerves carrying environmental information to the CNS, cell bodies located at thoracic and upper levels of lumbar (L1-3)
Be able to define Lissauer’s tract
Pain fibers on the outer rim of dorsal horn. Neurons (within spinothalamic tract) enter at lateral end of the dorsal horn and terminate at the substantia gelatinosa Modality conveyed: pain, temp, light touch. Instead of immediately synapsing and desiccating, the first order neurons ascend a few sections, this allows certain spinal cord lesions to be bypassed
Be able to describe the motor unit
Includes the motor nerve and the associated muscle fibers innervated with said nerve
Starts in ventral horn of spinal cord. Upper starting point is large motor, lower is small motor. More medial is extensors, lateral flexors
Be able to define motoneuron pool
There is a length of spinal cord taken up my motoneuron pool (collection of motoneurons)
Be able to list and define sensory structures in muscle
Muscle spindle apparatus (2 receptive cells types): length and change of length of muscle. Group 1a (primary)=change in length (dynamic) Group II (secondary)=length (static)
– Golgi Tendon organ: tension of muscle contraction
Gamma fiber modulates tonality of the muscle
Be able to list describe spinal reflexes
Myotatic: knee jerk reflex. Contraction of muscle in response to passive stretching. 2 neuron reflex (tense extensor, inhibit flexor). Withdrawal reflex: automatic withdrawal from pain. Flexors contract and extensors relax. Opposite occurs in other leg to balance.
– Crossed extension reflex: Elicits withdrawal of single joint. Flexors contract, extensors relax. Contralateral (occurs on opposite side of stimulus).
