What are the components of the CNS?
Brain and spinal cord
What are the components of the PNS?
12 pairs of cranial nerves
31 pairs of spinal nerves and branches
What makes up the brainstem?
Midbrain, pons and medulla oblongata
What makes up the diencephalon?
Thalamus + hypothalamus
What are the two principal cells of the CNS?
Neurons and glial cells
What are the four major types of glial cells?
Astrocytes, oligodendrocytes, microglia, ependymal cells
What is the function of astrocytes?
Support, maintenance of the BBB and environmental homeostasis
What is the function of oligodendrocytes?
Produce myelin in the CNS
What is the function of microglia cells?
Antigen presentation and phagocytosis
What is the function of ependymal cells?
Ciliated columnar epithelium which lines the ventricles of the brain
What are the lumpy bits of the brain called and what are the indents called?
Gyri (lumps), sulci(indents), fissures (deeper than sulci)
What is the general location of white and grey matter in the brain and the spinal cord ?
Grey matter is mostly outside and white is mostly inside. (BRAIN)
White matter is outside and grey matter is inside. (SPINAL CORD)
What is white and grey matter composed of?
White matter mostly consists of myelinated axons and their support cells
Grey matter mostly consists of neurons, cell processes, synapses and support cells
Describe the location of the frontal lobe of the cerebral hemisphere of the brainin relation to sulci
Anterior to the central sulcus and superior to the lateral sulcus
Describe the location of the parietal lobe of the cerebral hemisphere in relation to sulci
Posterior to the central sulcus, superior to the lateral sulcus and anterior to the parieto-occipitaq sulcus
Describe the location of the occipital lobe of the cerebral hemisphere in relation to sulci
Posterior to the parietal-occipital sulcus
Describe the location of the temporal lobe of the cerebral hemisphere in relation to sulci
Inferior to the lateral sulcus
What is the important role of the insular lobe of the brain?
Plays a role in the patient’s experience of pain
NB this lobe can only be seen when the brain is dissected
What are the three layers of the meninges from superficial to deep?
Dura matter, arachnoid matter, pia matter
What two things make up the arachnoid matter?
Subarachnoid space and CSF fluid
What is the enteric nervous system?
The nervous system of the digestive system - made up of the myenteric plexus and the submucosal plexus
The dural venous sinuses of the brain drain into which vein?
Internal jugular vein
Where are motor neurones in the spinal cord?
Anterior (ventral) horns
Which cell types lines the ventricles of the brain?
Ependymal cells
Which two things make up the lentiform nucleus?
Putamen and globus pallidus
What is the interthalamic adhesion?
The touching point between the two halves of the thalamus
What is the new name given to the spinal cord after it terminates at L2?
Conus medullaris
After the spinal cord terminates at the conus medullaris, it continues as a thin connective tissue cord, what is this called?
The filum terminale - this is anchored to the dorsal of the coccyx
The spinal cord is suspended in the canal by which ligament?
The denticulate ligament
A small central canal extends the length of the spinal cord. Rostrally it is continuous with which structure?
It is continuous with the 4th ventricle of the brian
Caudally it is blind ending
What is present at spinal levels T1 - L2 which isn’t present at other levels?
At T1-L2 there are small lateral horns (aswell as the usual A&P horns) which contain the preganglionic sympathetic neurons (THORACOLUMBAR OUTFLOW)
Describe the arterial supply to the spinal cord
Vertebral arteries give rise to 1 anterior and 2 posterior longitudinal arteries
Segmental arteries
Radicular arteries
Describe the venous drainage of the spinal cord
Longitudinal and segmental veins drain the spinal cord
What is the epidural space?
The space between dura and bone in the spinal canal.
It contains fat and the anterior and posterior epidural venous plexuses.
White matter occupies a smaller proportion of the cord as it descends from cervical to sacral. T/F
True
At which points is the spinal cord largest?
The spinal cord is larger in cervical and lumbar regions
What are the names of the ascending spinal cord tracts?
The dorsal column/ medial lemniscus system (DCML)
Spinothalamic tract
The dorsal column/ medial lemniscus system carries what information?
This is one of the ascending sensory tracts which carries information about fine touch and proprioception
Where do the fibres cross in the dorsal column/medial lemniscus system ascending tract?
The fibres cross over in the medulla
The spinothalamic tract carries what information?
This is one of the ascending sensory tracts which carries information about pain, temperature and deep pressure
Where do the fibres cross in the spinothalamic tract?
The fibres cross segmentally
What are the names of the descending spinal cord tracts?
PYRAMIDAL TRACTS
Corticospinal tract
Corticotubular tract
EXTRAPYRAMIDAL TRACTS
Tectospinal tract
Reticulospinal tract
Vestibulospinal tract
The corticospinal tract is one of the descending motor tracts. What motor functions is it involved in?
Fine and precise movements, especially of the distal limb muscles (e.g digits)
NB corticospinal - starts in the cortex and ends in the spine
Where do most of the fibres cross in the corticospinal descending tract?
Lateral CST - Most of the fibres cross at the decussation of the pyramids (in the medulla)
Ventral CST - fibres cross segmentally (still cross but just at random points)
What is meant by ‘decorticate posturing’ and which pathway is responsible?
Spastic paralysis with hyperFLEXION of the upper limbs
Caused by lack of control of the descending corticospinal tract e.g due to infarct
Which of the descending tracts is thought to mediate reflex head and neck movement due to visual stimuli?
Tectospinal tract
(starts in the tectum(roof of the midbrain) and ends in the spinal cord)
Only serves the cervical regions
Which descending tract receives input from almost all parts of the CNS and has many functions?
The reticulospinal tract
With reference to the reticulospianl tract, what movements do fibres originating in the pons Vs the medulla facilitate?
Fibres originating in pons facilitate extensor movements and inhibit flexor movements, while those originating in the medulla do the opposite.
What is the function of the vestibulospinal tract?
Posture and balance
NB this tract doesn’t cross over - it is ipsilateral
What is ‘decorticate rigidity’? and which pathway is responsible?
HyperEXTENDED spastic paralysis
Caused by lack of control of the vestibulospinal tract E.g due to lesions of the brainstem at the midbrain
What term is used to describe crossing over in the spinal tract?
Decussation
Describe Brown Sequard Syndrome
Brown-Séquard syndrome is caused by damage to one half of the spinal cord
Results in paralysis and loss of proprioception on the SAME SIDE as the injury or lesion and loss of pain and temperature sensation on the OPPOSITE SIDE as the lesion.
What are the three lobes of the cerebellum?
Anterior lobe, posterior lobe, flocculonodular node
*Posterior lobe is the largest
Describe the location of the cerebellum
The cerebellum sits in the posterior cranial fossa and is subtentorial (inferior to the tentorium cerebellum)
How is the cerebellum attached to the brainstem?
The cerebellum is attached to the brainstem via 3 peduncles (stalks) - superior, middle and inferior
Describe the locations of grey and white matter in the cerebellum
Outer grey matter with an inner white matter core. There is also some deep grey matter.
What are the 3 cell layers of the cerebellar cortex from outer to inner?
Molecular layer, purkinje layer, granule cell layer
What are the 3 main functional divisions of the cerebellum and what role do they each play?
Pontocerebellum - planning and carrying out movements (particularly in distal limb movements)
Spinocerebellum - postural control
Vestibulocerebellum - balance
What is cerebellar ataxia?
When the cerebellum becomes inflamed or damaged
E.g due to alcohol intoxication
Affects movement
What are the functions of basal ganglia?
Facilitate purposeful movements
Inhibit unwanted movements
Posture and muscle tone
What are basal ganglia?
Masses of grey matter located near the base of each cerebral hemisphere
What 5 structures make up basal ganglia?
Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra
How do basal ganglia work with the motor cortex to enhance normal movement or suppress unwanted movement?
Direct pathway; enhances outflow from the thalamus
Indirect pathway; inhibits outflow from the thalamus
Unilateral cerebellar lesions affect which side of the body?
IPSILATERAL SIDE
damage to one side of the cerebellum results in impaired function on the same side of the body
Unilateral basal ganglia lesions affect which side of the body?
CONTRALATERAL SIDE
damage to basal ganglia on one side results in impaired function on the opposite side of the body
Lesions of basal ganglia cause what kind of motor signs?
Changes in muscle tone
Dyskinesias (involuntary movements)
Dyskinesias is a term used to describe abnormal/ involuntary movements. Give some examples of types of dyskinesias
Tremor (sinusoidal movements)
Chorea (asymmetrical movements)
Myoclonus (muscle jerks)
Name some disorders associated with basal ganglia
Parkinson’s
Huntington’s chorea
What is the basic pathology behind Parkinson’s disease?
Degeneration of dopaminergic neurons of the substantial nigra
What are the clinical signs of Parkinson’s?
Akinesia, rigidity, resting tremor
What is the basic pathology behind Huntington’s Disease?
Progressie degeneration of the basal ganglia and cerebral cortex
What are the clinical signs of Huntington’s?
Chorea and progressive dementia
What is unique about the optic nerve?
It is myelinated by oligodendrocytes, meaning it is essentially a bit of CNS
Describe the location of the nerve fibres in CN I (olfactory nerve) with relation to the olfactory bulb and tract
The olfactory tract gives rise to the olfactory bulb which sits in the cribriform plate, the nerve fibres dangle down into the nasal cavity
(the nerve fibres are in contact with the outside world - they therefore die off over time)
Which cranial nerves are purely motor?
III, IV, VI, XI, XII
Where does the spinal accessory nerve arise from?
The cervical spinal cord
Which cranial nerves have mixed modalities?
CN V, VII, IX and X
The sensory nucleus of the trigeminal nerve has 3 parts; what are they and what are their functions?
Mesencephalic nucleus - proprioception info from chewing muscles/ teeth/ jaw
Pontine trigeminal nucleus - discriminative touch and vibration
Spinal nucleus - pain and temp
Some brainstem nuclei are shared by more than one CN
The solitary nucleus for taste and sensory info is shared by which nerves?
CN VII, IX and X
Some brainstem nuclei are shared by more than one CN
Superior and inferior salivary nuclei are shared by which nerves?
CN VII and IX
Some brainstem nuclei are shared by more than one CN
Nucleus ambiguus are shared by which nerves?
CN IX and X
Which descending spinal cord tract gives motor input to the cranial nerves?
(CN V, VII, X and XII)
Corticotubular tract
Where do fibres carrying low vs high frequency sound end in the auditory cortex?
Low frequency sound - end in the anterolateral part of the auditory cortex
High frequency sound end in the posteromedial part of the auditory cortex
What is meany by ‘aphasia’?
Inability to use language
Describe what happens when there is damage to Broca’s area of the brain
Difficulty PRODUCING language (comprehension is ok)
Broca’s area of the brain manufactures speech
Describe what happens when there is damage to Wernicke’s area of the brain
Difficulty COMPREHENDING language
Wernicke’s area of the brain interprets speech
Superior to the cochlea input is BILATERAL. T/F
True - this means that any problems with the brainstem etc would cause bilateral hearing loss, whereas problems with the cochlea would cause unilateral hearing loss.
Describe the two types of eye movements
Tracking movements
- E.g following your finger
- smooth movement
Movements of command
- E.g scanning a room of people
- saccadic jumpy movement
What are the three types of fibres in the white matter of the cerebral hemispheres?
Association fibres
(connect cortical sites within the same hemisphere)
Commissural fibres (connect R&L hemispheres)
Projection fibres (connect hemispheres to deeper structures e.f thalamus and brainstem)