Week 4 Flashcards
Where are the origins of autonomic parasympathetic nerves?
Craniosacral
Name the barriers of the CNS
-bony structures (vertebrae protection)
-meninges (dura, arachnoid, pia)
Barriers via external and internal chemical (CSF, blood-brain barrier)
Between which two meningeal layers does blood gill in a hemorrhagic stroke?
Arachnoid and pia
List the vasculature of the spinal cord
- 1 anterior spinal
- 2 posterior spinal
- radicular arteries
How is the spinal cord secured in the middle of the bony vertebrae?
Via arachnoid trabeculae and denticulate ligaments
Describe the organisation of spinal nerves
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
At what level of vertebrates does the spinal cord end?
L1/L2
Do spinal cord segments and corresponding vertebrae align?
NO
Describe the end of the spinal cord with their specific terms
Conus medullaris (termination of spinal cord L1/L2) -> cauda equina -> filum terminale -> subarachnoid space
Brachial movement is innervated by motor neuron tracts extending form which region of the spinal cord?
Cervical
Describe the internal organisation of the spinal cord
White matter tracts surround inner H-shaped grey matter
What does grey matter contain?
Areas containing neuronal cell bodies, dendrites, connecting axons and synapses, supporting glia
What does white matter contain ?
Bundles of axons
Out of how many zones does the rexed laminae consist of?
10
What is the function of laminae 1-6?
Dorsal horn - receives sensory information and is involved in its processing
What is the function of lamina 7?
Intermediate zone - contains cell groups for sensory-motor integration, visceral sensory anf autonomic preganglionic motor nuclei at thoracic and sacral levels
What is the function of lamina 8 and 9?
Ventral horn - containing motor and interneurons and lower motor neurons
What is the function of lamina 10?
Central zone - interneurons, somatosensory and visceral processing
what kind of processing happens in the dorsal horn?
Somatosensory
Describe where the inputs into the dorsal horn go to
C, A-delta -> 1,2
A-beta afferents -> 3,4
Mixed inputs -> 5
Proprioceptive -> 6
Are a-delta fibres afferent or efferent and what type are they?
Afferent, sensory
Are C fibres afferent r efferent and what type are they ?
Afferent, motor+ sensory
Are a-beta fibres afferent or efferent and what type are they ?
Both, sensory and motor
Describe the relation of the dorsal horn to pain
- nociceptive afferents (C+A) input to laminae 1,2,5
- interneuron processing in lamina 2 (substantia gelatinosa) modulates sensitivity to nociceptive stimuli
What neurons are in the lateral horn of the thoracolumbar spinal cord?
Pregagnglionic sympathetic neurons (motor)
What is contained in the ventral horn?
- somatic motor neurons in ventral horn somatotopically arranged
What is innervated by medially located neurons in the ventral horn?
Axial musculature
What is innervated by laterally located neurons in the ventral horn?
Limbs
grey matter summary
Lateral horn - contains preganglionic sympathetic neurons: efferent output to sympathetic ganglia which innervate muscle and glands
Dorsal horn - afferent input from skin and muscle
Ventral horn - contains motor neurons - efferent output to skeletal muscle
Which type of neural fiber receive afferent autonomic input at the dorsal horn
B
Describe the organisation of white matter
- dorsal column
- lateral column
- ventral column
What two tracts are there aiding communication between the spinal cord and the brain?
- ascending
- descending
Where are the ascending tracts in the white matter?
Dorsal columns
What two ascending tracts are there?
- spinocerebellar tracts
- spinothalamic tracts
What kind of info is carried in afferents ascending dorsal columns?
Proprioceptive (limb position, movement and force), discriminative touch
How is proprioceptive and discriminative touch information carried in afferents ascending in the dorsal column brought to the cerebral cortex and conscious perception ?
- mechanoreceptor afferents
- dorsal column nucleus
- ventral posterior nucleus of the thalamus
Whats the pathway called going through the dorsal column?
Medial lemniscus pathway
Describe the spinothalamic tract
- carries information about pain, innocuous temperature
- three neurons bring information to conscious perception
1. Primary afferent synapses in lamina 1,5 of dorsal horn
2. 2nd order spinal projection neuron
3. 3rd order ventral posterior nucleus
Where do descending tracts arise?
Cerebral cortex and brainstem
What do descending tracts do ?
Control movement, muscle tone, spinal refelxes, autonomic functions, sensory transmission
What does the corticospinal tract do?
Movement - prinicpal motor control pathway
What does the rubrospinal tract do?
Upper limb flexor muscles
What does the vestibulospinal tracts do?
Msucle tone
What does the reticulospinal tracts do ?
Voluntary movement, reflexes
Where does the corticospinal tract originate?
- motor cortex - precentral gyrus - and related cortices
Describe the course of motor neurons in the corticospinal tract
- cortical axons travel via posterior limb of internal capsule through ventral part of brainstem
- axons directly synapse on motor neurons and also with interneurons within the ventral horn
Describe the fasciculus gracilis
- from ipsilateral dorsal root ganglia
- large-diameter afferents
- below T6 to ipsilateral nucleus gracilis
- touch and position info from ipsilateral leg
Describe the fasciculus cuneatus
- from ipsilateral dorsal root ganglia
- large diameter afferents
- above T6
- to ipsilateral nuclues cuneatus
- touch and position information from ipsilateral arm
Describe the lateral corticospinal tract
- from contralateral motor cortex to motor neurons and interneurons
- voluntary movement
Describe the spinothalamic tract
- from contralateral posterior horn to thalamus
- pain and temp and some touch info from contralateral half of the body
Columns of white matter recap
ventral column - contains spinothalamic tract
Lateral horn - contains cerebrospinal tract
Dorsal column - contains medial lemniscus (DCML) tract from fasciculus gracilis (arm) and fasciculus cuneatus (leg)
Which ascending tract delivers unconscious proprioception information
Spinocerebellar
