Structure and function of the CNS 2 Flashcards
What does the trigeminal nerve do?
General sensation of the head
What do nuclei cutaneous and gracilis do?
Dorsal columns for proprioception and discriminative touch
What is the decussation of pyramids?
Crossing over of descending corticospinal tract
Function of spinocerebellar tracts
Control of posture and movement coordination
What is found at level of mid-medulla?
- Nucleus of the spinal tract of trigeminal nerve
- Fasciculus and nucleus cuneatus
- Fasciculus and nucleus gracilis
- Pyramid, the pyramidal tract or corticospinal tract
- Spinocerebellar tracts
What do pyramid, pyramidal tract and corticospinal tract do?
Control of voluntary, discrete skilled movements
What is found at the level of the rostral medulla?
- Fourth ventricle
- Dorsal motor nucleus of Vagus
- Hypoglossal nucleus and nerve fibers
- Inferior cerebellar peduncle
- Pyramid
- Inferior olivary nucleus
What does inferior olivary nucleus do?
Receives afferent fibers from motor and sensory cortices of the cerebral hemisphere and red nucleus of midbrain, for control of movement through cerebellum
What is found at the level of the mid pons and trigeminal nerve?
- Middle cerebellar peduncle
- Superior cerebellar peduncle
- Trigeminal nerve
- Fourth ventricle
- Corticospinal fibres
- Reticular formation
What is reticular formation?
Network of neurone in mid pons
What is Pontine and Medullary reticular formatuin?
Respiratory and cardiovascular centers which control respiratory movements and cardiovascular functions
What is the reticular activating system?
Some ascending fibers of the reticular formation act via thalamic nuclei to cause activation of the cerebral cortex and heightened arousal
What is found at the level of the inferior colliculus?
- Crus cerebri (cerebral peduncle)
- Superior cerebellar peduncle
- Trochlear nucleus
- Substantia nigra
- Inferior colliculus - auditory pathway relay station
- Cerebral aqueduct
Function of substantial nigra
Contains pigmented, melanin-containing neurons that synthesise dopamine and is connected with the basal ganglia
What is the inferior colliculus?
Auditory pathway relay station
What can be found at level of the superior colliculus?
- Crus cerebri (cerebral peduncle)
- Substantia nigra
- Red nucleus
- Oculomotor nucleus
- Cerebral aqueduct
- Superior colliculus
What does the cerebral peduncles do?
Attach the cerebrum to brainstem
Function of red nucleus
Involved in motor control and receives fibers from motor cortex of the frontal lobe
Where is oculomotor nucleus found in superior colliculus?
Floor of fourth ventricle
Function of superior colliculus
Relay station for visual pathway
What are the two cerebellar hemispheres separated by?
Midline vermis
What is the cerebellum divided into?
Small anterior and large posterior lobes
What does the posterolateral fissure do?
Separates the cerebellar hemisphere from the flocculonodular lobe
How is the brainstem connected to the cerebellum?
Inferior, middle and superior cerebellar peduncles
Does the cerebellum have sensory function?
No - it is entirely motor
What does the cerebellum do?
Maintenance of equilibrium (balance), influences posture and muscle tone and coordinates movement
What are the 3 subdivisions of the cerebellum?
Archicerebellum
Paleocerebellum
Neocerebellum
What does the archicerebellum do?
Maintenance of balance
What is the archicerebellum made of?
Flocculonodular lobe, fastigi nuclei
What does the paleo cerebellum do?
Muscle tone and posture
What is the paleo-cerebellum made of?
Midline vermis, paravermis with globes and emboli form nuclei
What is the neocerebellum made from?
Cerebellar hemisphere and dentate nuclei
What does the neocerebellum do?
Muscle coordination, trajectory, speed and force of movements
What are the 4 nuclear masses found in the cerebellum?
Dentate nucleus
Emboliform
Fastigial nucleus
Globose nuclei
Symptoms of cerebellar lesions
Incoordination of upper/lower limbs, speech and eyes
Symptoms of a midline lesion
Loss of postural control
Symptoms of unilateral lesion of cerebellar hemisphere
Symptoms on same side of body, unsteady gait
Symptoms of alcohol intoxication/hypothyroidism
Slowness and slurring of speech (dysarthria), incoordination of both arms and staggering, wide-based and unsteady gait (cerebellar ataxia)
What is Charcot’s triad?
Nystagmus, dysarthria and intention tremor
What are the meninges?
3 layers of membranes that cover the brain and spinal cord
What is the outer layer?
Dura mater
How many layers of the dura mater are there around the brain?
2 - endosteal and meningeal bn
How many layers of the dura mater are there around the spinal cord ?
One
What is the middle layer of the meninges?
Arachnoid mater
What separates the dura and arachnoid maters?
Subdural space
What is the inner layer of the meninges?
Pia mater
What separates the Pia from the arachnoid mater?
Subarachnoid space
4 components of the dura mater
Falx cerebri
Tentorium cerebelli
Tentorial notch
Falx cerebelli
What are arachnoid villi?
Arachnoid mater forms processes that project as clumps called granulations into superior sagittal sinus
What do arachnoid granulations do?
Return CSF to venous system
What does the trigeminal nerve supply?
Cranial dura mater of the floor of the anterior, middle and roof of the posterior cranial fossae including the falx cerebri
Which spinal nerves innervate the dura of the floor of the posterior cranial fossa?
C2 and C3
Via Vagus and Hypoglossal nerves
Does the arachnoid mater receive any nerve supply?
No
How is pain from the dura mater perceived?
Headache via spinal or diversion of trigeminal nerve
What are brain ventricles?
Interconnecting chambers filled with CSF
Where is CSF produced?
Choroid plexus (formed by Pia mater)
Characteristics of brain ventricular system
- Paired lateral ventricles (left and right)
- Unpaired third ventricle
- Unpaired fourth ventricle
- Fourth connected to third by cerebral aqueduct
- The ventricular system communicates with the subarachnoid space
- Involved in cerebrospinal fluid drainage from brain and brain stem
How is the fourth ventricle connected to the third?
Cerebral aqueduct
What does the spinal cord do?
Carries sensory, motor and autonomic innervation
Where does the spinal cord terminate caudally in adult and child?
Adult: between L1 and L2
Child: L3
What are the two enlargements of the spinal cord?
Cervical and lumbar
What does the cervical enlargement of the spinal cord do?
Supplies upper limb
What does the lumbar enlargement of the spinal cord do?
Supplies lower limb
Which spinal nerves make up the cervical enlargement of the spinal cord?
C4-T1
Which spinal nerves make up the lumbar enlargement of the spinal cord?
L1-S3
What is the conus medullar is?
Conical termination of spinal cord
What is the filum terminale?
Connective tissue extending from tip of conus medullar is to the dorsal surface of the first coccygeal vertebral
How many pairs of spinal nerves are there?
31 pairs
What are the different types of spinal nerves?
8 cervical, 12 thoracic, 5 lumbar and 5 sacral
What is the cauda equina?
Below termination of spinal cord, nerves descend in the cauda equina before exiting the vertebral column through their respective foramina
Where do thoracic nerves emerge, respective to their corresponding vertebrae?
Below vertebrae
Where do cervical spinal nerves emerge respective to their corresponding vertebrae?
Above vertebrae
What are the two roots of each spinal nerve?
Dorsal and ventral
Do dorsal roots carry afferent or efferent information?
Afferent
Do ventral roots carry afferent or efferent information?
Efferent
How do spinal nerves exit the vertebral column?
Intervertebral foramen
What are the three horns of the grey matter?
Ventral, dorsal and lateral horns
In which area is the lateral horn present?
Thoracic and lumbar segments of spinal cord
What is contained in the lateral horn?
Cell bodies of the preganglionic sympathetic neurons
What is found in the dorsal column of the ascending tract of the spinal cord?
Fasciculus gracilis and fasciculus cuneatus
What does the spinothalamic tract do?
Pain and temperature
What do the spinocerebellar tracts do?
Coordination of movement
Are ascending tracts motor or sensory?
Sensory - come from periphery to CNS
Are descending tracts motor or sensory?
Motor - from brain to periphery
What are the 4 descending tracts?
Ventral corticospinal
Lateral vestibulospinal
Medial longitudinal fasciculus
Lateral corticospinal
Symptoms of unilateral brainstem lesion
Ipsilateral cranial nerve dysfunction, contralateral spastic hemiparesis, hyperreflexia and extensor plantar response
Why are bilateral lesions dangerous?
Destroys vital centers controlling breathing and circulation, leading to coma and death
Causes of bilateral lesions
Occlusion of anterior spinal artery, fractures of spine, compression of spinal cord and nerve roots, prolapsed intervertebral disc
Why re focal lesions dangerous?
Can lead to destruction of functions at segmental levels
How is Brown-Sequard syndrome caused?
Heme-lesion of thoracic spinal cord
