Neurosensory Physiology Flashcards
Middle cranial fossa
Posterior Cranial Fossa
General anatomy of cerebellum
General anatomy of brain stem
How is the spinal chord protected?
- Wall of the vertebra
- Epidural space
- Duramater - thick and strong, dense irregular tissue
- Subdural space - contains interstitial fluid
- Arachnoid mater - Avascular, thin, elastic and cartilage
- Sub arachnoid space - Full of CSF fluid
- Pia mater - blood supply, thin and transparent
• Denticulate ligaments - thickening of pia mater extending to arachnoid and dura mater.
Protects spinal chord against sudden displacement
Oragnisation of nerves
Dorsal root (posterior) - contains sensory neurons from sensory receptors
Dorsal ramus - supplies posterior surface skin such as deep muscles of back
Anterior ventral root - motor axons conduct nerve impulses to effector muscles
Anterior ramus - Supplies anterior, lateral surfaces as well as upper and lower limbs
Protection of nerves
Endonierium - indivisual axons
Fascicles - Perineureum
Outermost layer - Epineurium
Parasympathetic nerve
- Long pre ganglionic fibres
- Ganglion within or adjacent to target organ
- Short post ganglionic fibres
Sympathetic nerve
- Short pre ganglionic nerve
- Synapse in sympathetc chain
- Long post ganglionic neuron straight to effector organ
except for splanchnic nerves
Splanchnic nerve
- Pre ganglionic neuron pass through the sumpathetic chain without synapsing
- Synapse in seperate collateral ganglia
Supplies abdomino visecera with sympathetic innervation
Medulla Oblongata
- Contains all ascending and descending spinal tracts between the spinal chord and brain
- Most inferior part of the brain stem
- Medullary pyramids - left & right, bulges of white matter anteriorly formed by corticospinal tract
- Medullary olive - Just lateral to each pyramid and an oval shaped swelling
- regulates muscle activity by regulating activity of cerebellar neurons
Pons
• Directly above the medulla oblongata
- Ventral region
• Pontine nuclei - white matter tracts between the cortex of one cerebral hemisphere to the opposite
- coordinates and maximises efficency of voluntary motor output
- Dorsal region
• Contains pontine resp centre
Mid brain
ANTERIOR - CEREBRAL PEDUNCLES
-paired bundls of axons from cerebral cortex to spinal chord
MIDDLE - CEREBRAL AQUEDUCT
- passes via the third ventricle to fourth ventricle
POSTERIOR -TECTUM
- • ( 2x) Superior colliculi - reflex centre for visual activity
- • Inferior colliculi (2x) - part of auditory pathways
Dorsal column - Medial leminiscus pathway
• First order neurone
- Signals from T6 above
- Travel in fasiculis cuneatus ( lateral part of dorsal column)
- Synapse in nucleus cuneatus in medulla oblongata
- Signals below T6
- Travel in fasiculus gracilis (medial part of dorsal column)
- Synapse in nucleus gracilis in medulla oblongata
• Second order neurone
- Axons decussate in medulla oblongata
- Travel via contralateral medial leminiscus pathway to synapse thalamus
• Third order neurone
- transmit sensory signals from thalamus to ipsilateral primary sensory cortex via internal capsule
Ascending tracts
Sensory information from peripheral nerves to the cerebral cortex
- Dorsal column medial leminiscus - fine touch, vibration and proprioception
- Anterolateral system
- Anterior spinothalmic tract - crude touch and pressure
- Lateral spinothalmic tract - pain and temperature
The anterolateral system
Anterior spinothalmic tract - crude touch and pressure
Lateral spinothalmic tract -pain and temperature
• First order neuron
- Arise from sensory receptors and synapse at the tip of the dorsal horn at an area known as the substantia gelatinosa
• Second order neuron
- Decussate in the spinal chord
- Crude touch and pressure fibres join the anterior spinothalmic tract // pain and temperature fibres join the lateral spinothalmic tract
- Fibres continue and synapse in the thalamus
• third order neuron
- Travel form the thalamus via the internal capsure to the primary sensory cortex of the brain
Spinocerebellar tract
Tracts that carry unconscious proprioceptive information
Transmit information from the muscle to the cerebellum
- Anterior spinocerebellar tract - lower limb to the cerebellum
- Posterior spinocerebellar tract - from muscles of the lower limb to the ipsilateral cerebellum
- Cuneocerebellar spinocerebellar tract -muscles of upper limbs to the ipsilateral cerebellum
- Rostral Spinocerebellar
Motor tracts can be functionally divided into 2 groups
Pyramidal tracts – These tracts originate in the cerebral cortex, carrying motor fibres to the spinal cord and brain stem.
- They are responsible for the voluntary control of the musculature of the body and face.
Extrapyramidal tracts – These tracts originate in the brain stem, carrying motor fibres to the spinal cord.
- They are responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion
Corticospinal tract
- A pyramidal tract
- The corticospinal tracts begin in the cerebral cortex, from which they receive a range of inputs:
Primary motor cortex
Premotor cortex
Supplementary motor area
- originating from the cortex
- neurones converge, and descend through the internal capsule (a white matter pathway, located between the thalamus and the basal ganglia).
- the neurones pass through the crus cerebri of the midbrain, the pons and into the medulla.
In the most inferior (caudal) part of the medulla, the tract divides into two:
The fibres within the lateral corticospinal tract decussate (cross over to the other side of the CNS). (90% of fibres)
They then descend into the spinal cord, terminating in the ventral horn.
From the ventral horn, the lower motor neurones go on to supply the muscles of the body.
• The anterior corticospinal tract remains ipsilateral, descending into the spinal cord. They then decussate and terminate in the ventral horn of the cervical and upper thoracicsegmental levels.
Corticobulbar tract
The corticobulbar tracts arise from the lateral aspect of the primary motor cortex.
They receive the same inputs as the corticospinal tracts.
The fibres converge and pass through the internal capsule to the brainstem.
The neurones terminate on the motor nuclei of the cranial nerves.
Here, they synapse with lower motor neurones, which carry the motor signals to the muscles of the face and neck.
diencephalon
epithalamus, subthalamus, hypothalamus and thalamus, optic chiasm and optic tract
Thalamus
grey matter
- Filter sensory stimulations
- Decides what travels to the cerebrum
Epithalamus
Has the pineal gland associated with melatonin roduction
Basal ganglia
Refines motor output by directing goal orientated movement and blocking out contradictory movement
