PHYS: Spinal Cord, Neural Communication + Spinal Reflexes Flashcards
where does the spinal cord extend to?
L1/L2 vertebrae
functions of spinal cord
- distribute motor fibres around the body
- connect brain to body
- somatic + autonomic reflexes
- sensory and motor modulation
- processes sensory info before passing on to the brain
divisions of the 31 spinal nerves and their functions
- cervical (C1-C8): autonomic functions e.g. breathing and some hand, wrist and arm movement
- thoracic (T1-T12): sympathetic tone e.g. trunk stability and temp regulation
- lumbar (L1-L5): ejaculation, hip, foot and knee movement
- sacral (S1-S5): penile erection, bowel and bladder activity
- 1 coccygeal
grey and white matter distribution in brain vs spinal cord
- brain: white inside and grey outside
- spinal cord: grey inside and white on outside
what are A, B and C?
- A = central canal (contains CSF)
- B = dorsal (sensory) horn
- C = ventral (motor) horn
what are D, E, F and G?
- D = lateral (visceral) horn
- E = dorsal root ganglion (neuron cell body)
- F = dorsal root
- G = ventral root
what does grey matter contain
- cell bodies (hence grey colour) and therefore nuclei, UNmyelinated axons
- runs length of spinal cord on inside
what does white matter contain
- axons (white due to myelin)
- spinal tracts
what are H, I and J?
- H = lateral column
- I = ventral column
- J = dorsal column
ganglion
connection of neuron cell bodies
what is a spinal tract
- group of nerve fibres in white matter responsible for carrying sensory and motor info to (ascending = sensory) and from (descending = motor) brain
2 types of ascending spinal tracts
- conscious tracts: dorsal column-medial lemniscal pathway (DCML) + anterolateral (spinothalamic) tract
- unconscious tracts: spinocerebellar tract
DCML pathway (conscious ascending)
- dorsal = behind = late = feeling very patient = fine touch, vibration, pressure
- 1st and 2nd order neurons synapse in medulla oblongata and decussate @ nucleus gracilus into medial lemniscus
- 2nd and 3rd order neurons synapse in thalamus and carry info to somatosensory cortex (frontal lobe)
anterolateral (spinothalamic) pathway (conscious ascending)
- anterior = Not That Patient = non-discriminative (crude touch), pressure
- lateral spinothalamic tract: pain and temp
- 1st and 2nd order neurons synapse in dorsal horn (spinal cord) and decussate there
- 2nd and 3rd order neurons synapse in thalamus and carry info to somatosensory cortex (frontal lobe)
spinocerebellar tract (ascending)
- don’t decussate
- innervate arms and legs
- proprioception
two types of descending pathways
- pyramidal (voluntary): motor info from brain to spinal cord + brain stem.
- extrapyramidal (involuntary): motor info from brain stem to spinal cord
2 pyramidal tracts (voluntary)
- corticospinal: supplies body muscles
- corticobulbar: head and neck muscles
4 extrapyramidal tracts (involuntary)
- vestibulospinal and reticulospinal: do not decussate = ipsilateral innervation
- rubrospinal and tectospinal: decussate = contralateral innervation
corticospinal tract
(pyramidal)
- upper motor neuron: brain > medulla oblongata > ventral horn
- lower motor neuron innervates muscles
corticobulbar tract
(pyramidal)
- upper motor neuron: brain > medulla oblongata > terminate at nuclei of cranial nerves
- lower motor neurons innervate face, head and neck muscles
spinal reflex
- automatic, rapid response to stimuli
- bypasses brain
reflex arc
- sensory receptor > sensory neuron > processing unit (spinal cord) > interneuron > motor neuron > effector muscle
reflex latency (delay)
- time taken for afferent pathway ΔTa
- time taken for central processing ΔTc
- time taken for efferent pathway ΔTe
flowchart of spinal tracts
what type of neurons are in the DRG?
- pseudounipolar
- cell body is in the middle of the two arms
Types of glia
- CNS: astroglia, microglia, oligodendroglia
- PNS: satellite cells, schwann cells
Astroglia
Star-shaped cells that provide physical and nutritional support for neurons and clean up brain debris in CNS
Microglia
Digest parts of dead neurons in CNS
Oligodendroglia
Provide myelin insulation to multiple axons in CNS
Satellite cells
Provide physical support to neurons in PNS
Schwann cells
provide myelin insulation to axons in PNS (wrap around axon)
what is found in the dorsal and ventral ramus?
- both sensory and motor neurons
- these are mixed spinal nerves
