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WEEK 6:
Spinal Cord + Basic Reflexes:
| Question | Answer |
|---|---|
| where is grey matter | inside |
| where is white matter | outisde |
| describe the top and bottom position of a transverse spinal cord diagram | dorsal top, ventral bottom |
| where is the central canal | middle of spinal cord |
| grey matter differentiation mainly | dorsal horn + ventral horn |
| dorsal horn | receive sensory information |
| ventral horn | send motor information |
| lateral horn | autonomic - sympathetic |
| lateral horn is found where | thoracic and upper lumbar vertebrae |
| white matter differentiation | posterior funiculus, lateral funiculus, anterior funiculus |
| posterior funiculus | send sensory information |
| lateral funiculus | both motor and sensory information |
| lateral funiculus | receives motor information |
| afferent neurons | towards CNS (sensory) |
| efferent neurons | away CNS (motor) |
| all spinal nerves + many peripheral nerves (eg phrenic nerve) both contain what | afferent + efferent neurons |
| example of nerve that is both afferent and efferent | phrenic nerve |
| sensory ganglia/ dorsal root ganglia (DRG) | cluster of sensory neurons found on the posterior side of the spinal cord |
| dorsal nerve root + dorsal nerve rootlets | rootlets make root, responsible for sending sensory information |
| meninges | three membranes covering spinal cord- dura matter, arachnoid, pia |
| dura mater of meninges | tough outermost layer |
| arachnoid layer of meninges | delicate middle layer |
| pia layer of meninges | membrane surrounding brain + spinal cord, innermost layer |
| subarachnoid space | space between arachnoid + pia, containing blood vessels + cerebrospinal fluid (CSF) |
| where is a lumbar puncture performed | in lumbar region, where spinal cord ending (forming cauda equina) to reduce the risk of a needle damaging the spinal cord |
| cervical vertebrae | 7 |
| thoracic vertebrae | 12 |
| lumbar vertebrae | 5 |
| sacral vertebrae | 5 fused |
| coccyx | 3-4 fused |
| cauda equina | horses tail - bundle of spinal nerves found at the lower end of spinal cord |
| why can you perform a lumbar puncture from under the spinal column | nerves tend to move away so not affected |
| describe growth in vertebral column and spinal cord | vertebral column grows more than spiral cord |
| spinal nerves consist of | 31 pairs of sensory + motor nerves |
| spinal (subarachnoid) spinal drug administration | drug diffuses throughout CNS |
| extradural/epidural spinal drug administration | only acts locally on spinal nerves |
| dorsal columns of ascending white matter consist of | gracile (hindlimb) + cuneate (forelimb) |
| spino-cerebellar columns of ascending white matter consist of | dorsal + ventral |
| spinothalamic columns of ascending white matter consist of | lateral + anterior |
| what does dorsal columns do | fine touch + proprioception (ability to sense own position and actions) |
| what does spino-cerebellar white matter do do | sends sensory information to cerebellum |
| what does spinothalamic white matter do | sends sensory information to thalamus |
| describe decussation in sensory nerves | all sensory nerves cross over (make an X) so if signal enters left side it will be processed in the right side |
| white matter descending tract (7) | lateral corticospinal**, rubrospinal, lateral reticulospinal, vestibulospinal, medial reticulospinal, tectospinal, anterior corticospinal** |
| corticospinal white matter descending tract function ** | controls voluntary movements especially distal part of limbs |
| tectospinal white matter descending tract | mediate reflex movements in response to visual/auditory stimuli |
| reticulospinal white matter descending tract | controls muscle tone (slight contraction of muscle at rest)+ reflex by controlling alpha + gamma motor neuron activity |
| rubrospinal white matter descending tract | controls large muscles of limb |
| vestibulospinal white matter descending tract | balance + posture |
| corticospinal white matter tract consists of | two neurons (upper and lower motor neurons) |
| types of lower motor neurons | alpha + gamma |
| alpha motor neurons function | supply nerves in extrafusal (main) muscle fibres needed for contraction |
| gamma motor neurons function | in spinal cord, supply nerves in intrafusal (small) muscle fibres in muscle spindles |
| where are alpha motor neurons found | neuromuscular junctions (NMJ) as the only connection between CNS and extrafusal muscle fibres |
| compare reflex activity to volitional control | reflexes are a response to stimulus + innate eg pull hand away from fire, BUT, volitional control is controlled by internal desire + learned + conditioned eg open a door |
| types of reflexes | superficial, deep (myotatic), visceral (autonomic) |
| superficial reflex | reflexes caused by skin stimulation eg corneal (blinking) or nasal (sneezing) |
| deep (myotatic) reflex | reflexes triggered by muscle stretch eg patellar (knee jerk) |
| visceral (autonomic) reflex | autonomic reflexes in organs eg micturition (removing urine from bladder) |
| bicep nerve type + vertebral level tested | musclocutaneous, C6 |
| tricep nerve type + vertebral level tested | radial, C7 |
| patellar nerve type + vertebral level tested | femoral, L4 |
| achilles nerve type + vertebral level tested | tibial + sciatic, S1 |
| Babinski's reflex | flexor response + extensor response |
| flexor response of Babinski's reflex | toes curl downward toward plantar surface in normal healthy adults |
| extensor response of Babinski's reflex | toes curl up and out - seen in adults sleeping/ damage in adults, OR babies |
| myotatic reflex pathology | (1-starts by stretching muscle/connecting tendon) (2- detected by afferent fibres + annulospiral stretch receptors in middle of muscle spindles) (3- excite interneurons to synaptically stop antagonist muscle from contracting- reciprocal innervation) |
| reciprocal innervation | contraction of agonist so antagonist relax = smooth coordinated muscle movement |
| crossed extensor reflex | coordination of contralateral muscles eg step on leg so right leg pulls away and left leg stiffens to support body so you don't fall over |
| meningitis | inflammation of meninges (membranes covering the brain + spinal cord) |
| subarachnoid haemorrhage (SAH) | type of stroke involving bleeding into subarachnoid space (space between arachnoid mater + pia mater) |
| example of conditions which require lumbar puncture | subarachnoid haemorrhage (SAH) and meningitis |
| when is lumbar puncture used for subarachnoid haemorrhage (SAH) | when results are negative on CT scan |
| when should a lumbar puncture be performed for subarachnoid haemorrhage (SAH) | 6 hours after onset of bleeding to ensure blood has reached lumbar region |
| lumbar puncture (spinal tap) | collect sample of cerebrospinal fluid (CBF) |
| white matter ascending tracts have what sections? | dorsal columns, spino-cerebellar and spinothalamic |
| how does white matter change down the spinal cord | decreases |
| differences between cervical vertebrae white matter and lumbar vertebrae white matter | cervical has both gracile (hindlimb) and cuneate (upper limb) white matter but lumbar only has gracile (lower limb) white matter |
| how does grey matter change down the spinal cord | increases |
| why does the white matter change down the spinal cord | gracile only used for lower limbs and cuneate used for upper limbs so only the cervical vertebrae need cuneate white matter |
| describe alpha motor neurons | lower motor neuron, multipolar + long axons with Ach at end of synapse |
| describe gamma motor neurons | lower motor neuron, smaller axon diameter, help in muscle tone (slight contraction of muscle at rest) |
| which reflex is commonly tested | deep (myotatic) |
Created by:
kablooey
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