spinal cord Flashcards
length of spinal cord
runs through the vertebral canal: foramen magnum to L1-2
how many spinal nerves are there
31 pairs of spinal nerves - all mixed nerves
are they uniform in diameter?
no:
- cervical enlargement
- lumbar enlargement
what is the conus medullaris
tapered inferior end
what is the caudal equina
lumbar and sacral nerve roots
functions of the vertebral column
- solid but flexible protective casing around cord
- intervertebral discs absorb shock
- transmits weight of trunk to lower limbs
- attachment point for ribs and muscles
- allows extension and flexion
what do the inverter discs also allow
allow movement of backwards and forwards
functions of the ligaments
- limits potentially damaging movement of spine
- keeps vertebral column in place
- adds flexibility to vertebral column
functions of meninges
- coat the spinal cord
- contains blood supply and cerebrospinal fluid
- barrier for neurotoxic substances,
cerebrospinal fluid functions
- suspends the brain and spinal cord,
- dense fluid that protects and absorbs shock
- nourishing fluid
segmental organisation of the vertebral column
7 cervical segments 12 thoracic segments 5 lumbar segments 5 sacral segments 1 coccygeal segment
how does the number of back bones change during growth
we are born with 33 bones - as you grow, the sacral and coccygeal bones fuse to form the sacrum and the coccyx
we have 26 bones
what is the function of the back bone curves
facilitate shock absorber
types of curves in the vertebral column
primary curves - thoracic and sacral areas
secondary curves - cervical and lumbar areas
what is the function of the epidural space
a yellowish fatty tissue that cushions the spinal cord and contains the venous plexus
where is the subdural space
below the dura mater
arachnoid mater
the spongiest layer of the spinal meninges
cobweb appearance
where is the subarachnoid space
space below the arachnoid mater which contains CSF
what is the pia mater
the finest layer of the spinal meninges
continuation of brain
what is the spinal nerve formed from
dorsal ventral roots
what does the dorsal cell ganglion contain
cell bodies of primary sensory neurons
layers of spinal meninges
dura mater (S2 level) arachnoid mater (S2 level) pia mater (L2 level)
why can the dura mater move in the vertebral canal
it is not directly attached to it
what is the lingamentum denticulum
a flat membrane formed from pia mater which anchors the pia mater to the arachnoid mater
where does the lingamentum denticulum lie
- along midline between the dorsal and ventral nerve roots
- laterally to adhere to the arachnoid and dura mater
where is the spinal cord suspended
in the middle of the dural sheath
arterial supply of spinal cord
- anterior spinal artery
- posterior spinal arteries
- radicular arteries
they can’t supply all the cords
venous drainage of spinal cord
- anterior and posterior median spinal veins in the midline
- anterolateral and posterolateral paired veins situated near the lines of attachment of the ventral and dorsal roots
- anterior and posterior radicular veins
- internal vertebral venous plexus in the epidural space
- external vertebral venous plexus
all drain in vena cava
circulation of CSF
- CSF is produced by the choroid plexus of each ventricle
- CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. some CSF flows through the central canal of the spinal cord
- CSF flows through the subarachnoid space
- CSF is absorbed into the dural venous sinuses via the arachnoid villi
what does the CSF provide
O2 and glucose
how do meningeal layers prevent bacteria entering brain
they have tight junctions
why is the lumbar puncture performed
to obtain CSF from subarachnoid space
typically midline between:
- L3 and L4 or L4 and L5
- inferior to spinal cord
what is the lumbar cistern
expanded subarachnoid space inferior to spinal cord
what is the centre of the spinal cord formed of
formed of grey matter - neuron bodies
where is the white matter located in the spinal cord
posterior, lateral and anterior column
where does the pia mater enter the spinal cord
anterior median fissure
dorsal (posterior) horn
sensory (afferent) information
I-VI (noxious, proprioceptive- body sense)
ventral (anterior) horn
motor (efferent) information
VIII-IX
lateral horn (T1-L2)
VII and X
the small lateral gray column of the spinal cord as appearing in transverse section containing the intermediolateral cell column.
what is a tract
neuron bundle within CNS
what is a nerve
neuron bundles outside CNS
what do descending tracts deliver
they deliver motor instructions from brain to spinal cord to muscles
groups of descending motor tracts
divided into two groups:
- pyramidal, or corticospinal, tracts (voluntary movements)
- extrapyramidal (indirect pathways) - all other motor tracts - unconscious muscle innervation
types of neurons involved in motor pathways
- upper motor neuron (UMN)
- lower motor neuron (LMN): anterior horn motor neuron - final common pathway to muscles
ascending tracts
- posterior column
- spinothalamic - pain perception
- spinolimbic/spinoreticular
- spinocerebellar
which ascending tracts send impulses to the sensory cortex
posterior column and spinothalamic pathways
which ascending tracts send impulses to the cerebellum
the spinocerebellar tracts - they also do not contribute to sensory perception
what are the ascending tracts composed of
3-neuron chain; 1st order, 2nd order and 3rd order neurons
ascending tract - steps of how impulses are sent to sensory cortex
- pain, temperature and coarse touch cross the midline in the spinal cord
- fine touch, vibration, and proprioception pathways cross the midline in the medulla
- sensory pathways synapse in the thalamus
- sensations are perceived in the primary somatic sensory cortex
spinal cord function
- carry sensory information from the body to the brain
- somesthesis (touch)
- thermosensation (temperature)
- nociception (pain)
- proprioception and kinesthesia (position and movement sense) - carry motor information from the brain to the body
- voluntary movement
- posture
- breathing - reflexes
why are reflexes useful
they increase the speed of reaction
impulses don’t go to the brain - go directly to the spinal cord
divisions of peripheral nervous system
sensory (afferent) division
motor (efferent) division
divisions of sensory division
somatic and visceral sensory
what do somatic sensory division sense
touch, pressure, pain, vibration, temperature
what do visceral sensory division sense
stretch, temperature, chemical change, irritation in viscera, nausea
divisions of motor division
somatic motor system and autonomic nervous system
divisions of autonomic nervous system
sympathetic and parasympathetic
where does the C1 emerge
above atlas - first cervical vertebra
where does the C8 emerge
below C7 vertebra
where do the remaining spinal nerves emerge
inferior to corresponding vertebrae
what are plexuses
branching networks of spinal nerves
what is the dermatome
area innervated by afferent in single spinal nerve
- cervical: upper limb and body
- thoracic: trunk
- lumbar and sacral: lower limb
functions of cervical spinal segment
- breathing
- head and neck movements
- heart rate
- upper limb movements
functions of thoracic spinal segment
- sympathetic tone
- trunk stability
functions of lumbar spinal segment
lower limb movements
functions of sacral spinal segment
bowel and bladder
spinal injuries
paralysis - loss of motor function
paraesthesia - loss on sensation
