The Spinal cord Flashcards
Where does the spinal cord originate, travel and terminate?
The spinal cord is travels from the temporal lobe and is continuous with the brainstem. It is located within the vertebral column and terminates at the spinal level of L1/2 vertebrae.
What is the vertebral level?
The level corresponding to which part of the vertebral column you are at e.g. T12.
What is the spinal level?
The level corresponding to which spinal cord you are referring to. This does not always correspond to the vertebral level, e.g. C8 spinal level is at the C7 vertebrae.
What are the 3 main functions of the spinal cord?
- To act as a protective mechanism to facilitate reflexes
- To transmit sensory information from sensory receptors to the primary sensory cortex in the parietal lobe of the cerebral cortex.
- To transmit motor information from the primary motor cortex to effectors such as muscles/glands.
Where are the 2 main enlargements of the spinal cord found?
The cervical enlargement - at C5-T1
The lumbar enlargement - at L1-S3
What is the name of the cone-shaped ending of the spinal cord?
The conus medullaris
What is the filum terminale?
A delicate piece of fibrous tissue travelling from the apex of the conus medullaris
What is the caude equine?
A bundle of spinal nerves consisting of L2-L5 and S1-S5 spinal levels. It occupies the lumbar cistern which is a sub-arachnoid space below the conus medullaris. It innervates the bladder, pelvic organs and the lower body.
Draw out/describe the descending tracts of the cross section of the spinal cord.
Right side starting from top to bottom: Lateral CST Rubrospinal tract Lateral RST Vestibulo spinal tract Medial RST Anterior CST
Draw out/describe the ascendongside of the cross section of the spinal cord.
Left side starting from top to bottom: Gracile tract Cuneate tract Posterior spinocerebellar tract Anterior spinocerebellar tract Spinothalamic tract
What is an upper motor neurone?
A motor nerve fibre travelling from the cerebral cortex to the anterior horn cell of the spinal cord - within the CNS.
What is a lower motor neurone?
e.g. the Alpha MN - a motor nerve fibre travelling from the anterior horn cell of the spinal cord to the muscle/groups of muscle fibres that it innervates - within the PNS.
What is an alpha motor neurone?
A multipolar lower motor neurone travelling from the anterior horn cell of the spinal cord to the skeletal muscle, namely the extrafusal fibres.
Describe the course of a gamma motor neurone and it’s function.
A lower motor neurone that travels from the AHC of the spinal cord to the intrafusal fibres of a muscle spindle to ‘reset’ the fibre and set it’s sensitivity to stretch so that it can continue to transmit somato-sensation to the dorsal horn of the spinal cord. It is involved in muscle tone/posture and balance.
What is a motor unit?
The motor neurone and the muscle fibre/groups of muscle that it innervates. Many motor units are called a motor pool and helps to regulate/coordinate muscle contractions.
What is a myotome?
A muscle/groups of muscles innervated by a single nerve root. e.g. the biceps is innervated by C5/6
What is a dermotome?
An area of skin innervated by a single nerve root. e.g. the dorsal surface of the little toe is innervated by S1.
What is reciprocal innervation?
The process by which an antagonist to a movement lowers the amount of tension produced/relaxes to allow the agonist to contract/cause movement e.g. hamstrings relax/lower tone to allow the quadriceps to cause knee extension.
Describe the simple stretch reflex
A stimulus e.g. patellar hammer on the patellar tendon causes the muscle spindle to stretch, this sends sensory information to the spinal cord via the dorsal root ganglion and synapses with the alpha motor neuron which causes the knee to extend. This is monosynaptic, unilateral and intrasegmental.
What is the role of a reflex?
To act as a protective mechanism e.g. to stop the patellar tendon tearing when stretched.
What is the flexor withdrawal reflex?
A withdrawal of a limb away from a dangerous stimulus to act as a protective mechanism e.g. foot stepping on a pin, the knee will flex to move away. This is intersegmental, polysynaptic and unilateral.
What is the crossed extensor reflex?
This occurs when the flexor withdrawal relfex occurs. e.g. you step on a pin and the knee flexes to move the moot away from the dangerous stimuli. However, if both knees were to flex, you would fall over. Therefore weight bearing occurs on the opposite limb and muscle tone increases to aid balance and posture and prevents you falling over. This is therefore polysynaptic, contralateral and intersegmental.
State the root value for the: Biceps/brachioradialis Triceps Patellar tendon Achilles tendon Plantar surface of the foot (Babinski's sign)
C5/6 C6/7 L2,3,4 S1,2,3 S1,2,3
