Lecture 1 - Topography Flashcards
What are the 3 main parts to the CNS?
Cerebral hemispheres
Brainstem and cerebellum
Spinal cord
What is the main functions of the cerebral hemispheres?
Higher function
Motor and sensory (conscious)
Emotion
Memory
What is the main function of the brainstem and cerebellum?
Communication via cranial nerves
Cerebellum = motor sequencing and coordination
What are the main functions of the spinal cord?
Ascending sensory and descending motor pathways
Spinal reflex arcs
Control of upper and lower limbs
What makes up grey matter?
Cell bodies and dendrites with rich blood supply
What is grey matter called in the PNS?
Ganglion
What is a ganglion?
What is its equivalent in the CNS?
Collection of cell bodies
Grey matter
What is the general function of grey matter/ganglia?
Where computation/processing occurs
What makes up white matter?
Mainly myelinated (+some non myelinated) axons with NO cell bodies
What is the function of white matter?
Act as pathways which connects areas of grey matter together
What is the equivalent of white matter in the PNS?
A nerve/root
How many segments make up the spinal cord?
31 segments
What does each of the 31 spinal cord segments supply?
A Dermatome and myotome on each side
What is a Dermatome?
A region of skin who’s sensation is supplied by a single specific spinal nerve root
What is a myotome?
A group of muscles supplied by a single spinal nerve
Where is the grey and white matter positioned in the brain?
Grey matter peripheral
White matter central
How is the grey and white matter positioned in the spinal cord?
Central core = grey matter
Outer shell = white matter
What is the structure of a spinal nerve?
Made up of a sensory and motor spinal nerve root (it’s mixed)
Which spinal nerve root is the sensory spinal nerve root?
Ventral or dorsal?
Dorsal root
Which spinal nerve root is the motor spinal nerve root?
Ventral or dorsal?
Ventral
Where is the lesion likely to be if a patient suffers a sensory deficit in the L4 Dermatome?
At the L4 dorsal root or spinal nerve
Where is the lesion likely to be if there a sensory deficit across multiple Dermatomes/segments?
Cord lesion
What are the 3 different types of structures of white matter in the spinal cord?
Funiculus
Tract
Fasciculus
What is a funiculus?
Large block of white matter containing multiple distinct pathways which both ascend and descend (sensory and motor so impulses go in both directions)
What is a tract?
White matter pathways that connect 2 distinct regions of grey matter
Which direction do impulses travel in a tract?
Single direction only
What does the spinothalamic tract connect?
Spinal cord dorsal horn to thalamus
What does the corticospinal tract connect?
Cerebral cortex to spinal cord ventral horn
What is a fasciculus?
Subdivision of a tract that supplies a distinct body region
What is the gracile fasciculus?
Subdivision of dorsal column tract supplying lower half of body
What is the cuneate fasciculus?
Subdivision of dorsal column tract supplying upper half of body BUT NOT THE HEAD
How are the cell bodies of spinal cord grey matter arranged?
Cell columns
What is a nucleus?
Collection of functionally related cell bodies
What is a cortex?
Folded sheet of cell bodies/grey matter found on the surface of the brain (cerebral hemispheres and cerebellum)
What is a fibre?
An axon in association with its supporting cells (axon+multiple Schwann cells)
What do association fibre connect?
Cortical regions within a hemisphere (parts on same side)
What do the commisural fibres connect?
Give an example:
The hemispheres
Corpuscle callosum
What are the key functions of the midbrain?
Eye movement (Oculomotor and trochlea)
Reflex response to visual and auditory stimuli
What are some key structures of the midbrain?
Oculomotor nucleus
Edinger-Westphal nucleus
What are the main functions of the pons?
How to remember this?
Feeding
Sleep
Once you’ve had a good feed you want to sleep
What cranial nerve is important in feeding from the pons?
Circuits involving Trigeminal nerve
What part of the pons does the Trigeminal nerve exit from?
Lateral aspect
What is locked in syndrome?
When the corticospinal fibres that travel ventrally from the pons can get damaged from basilar artery occlusion
What structure does the pons sit inferior to?
What is the danger of this?
Fourth ventricle
Can get compressed if the 4th ventricle expands
What regions in the pons are important for sleep?
Reticular formation (grey matter) regions
What are medullary pyramids?
Area of descending motor fibres
Made of white matter , ventral swellings on each side contains corticospinal fibres from the Ipsilateral hemisphere
What part of the brain contains the gracile and cuneate nuclei?
What type of matter are these?
Medulla
Grey matter
What part of the brain contains the improtant nuclei for cardio respiratory homeostasis?
Medulla
What is the substantia nigra?
Grey matter part of the midbrain containing dopaminergic neurones that go to the striatum
What is the Oculomotor nucleus and where is it found?
Grey matter in the midbrain that contains lower motor neurone cell bodies that project through the Oculomotor nerve to all except 2 of the extra ocular muscles
What is the edinger Westphal nucleus and where is it?
Grey matter containing parasympathetic Preganglionic neurones that project to the ciliary ganglion/body in the orbit to cause pupil constriction
What are the names of the dips and bulges on the brain?
Gyri = raised bulge of cerebral cortex
Sulci = valley between adjacent gyri
What is a fissure?
Large groove between adjacent hemispheres
What is the central sulcus? (What does it separate)?
Separates pre central and post central gyri running from the temporal lobe up to the midline
What is the function of the pre central gyrus?
Primary Motor cortex which is anterior to the central sulcus
What is the function of the post central gyrus?
Primary sensory context posterior to the central sulcus
What is the lateral fissure?
Separates temporal lobe from the frontal and parietal lobes
What is the function of the calcarine sulcus?
Key landmark in the visual system
The primary visual cortex surrounds this
Where is the calcarine sulcus located?
What structure surrounds it?
Visual cortex
What visual field is supplied by the visual cortex above the calcarine sulcus?
Contralateral inferior field
What visual field is supplied by the visual cortex below the calcarine sulcus?
Contralateral superior visual field
What is the optic chiasm?
Site where fibres in the visual system cross over
What is the parieto-occipital sulcus?
Sepearates parietal from occipital lobes
What is the uncus and what is its important role?
Part of temporal lobe that can herniate below the tentorium cerebelli compressing the midbrain
Important olfactory role
Occulomotor nerve often damaged
What is the parahippocampal gyrus?
Part of the medial temporal lobe that provides input to the underlying hippocampus
Key cortical region for memory encoding
What is the corpus callosum?
Fibres connecting the 2 cerebral hemispheres
What is the function of the thalamus?
Sensory relay station projecting to sensory cortex
What is the function of the cingulate gyrus?
Cortical area important for emotion and memory
What is the function of the hypothalamus?
Essential centre for homeostasis
What is the fornix?
Major output pathway from the hippocampus
Where is the thalamus and hypothalamus?
Found in the wall of the third ventricle
Thalamus just below corpus callosum
Hypothalamus just below thalamus
What is the tectum?
Where is it found?
Posterior part of the midbrain involves in involuntary responses to auditory and visual stimuli
What/where are the cerebellar tonsils?
Found on the inferior aspect of the cerebellum that can herniate down through the Foramen magnum in cases of raised intracranial pressure which can lead to death due to cardio respiratory compromise through compression of the medulla
What are the hollow cavities in the brain called?
Brain ventricles
What is produced int he ventricles?
CSF
What produces the CSF in the ventricles?
Choroid plexus
How much CSF is made by the choroid plexus per day?
600ml to 700ml
What are the functions of CSF?
Metabolic (glucose and hormones containing)
Mechanical (shock absorption)
What does the CSF circulate through and where does it get reabsorbed?
Ventricular system and subarachnoid space
Reabsorbed at the arachnoid granulations
What sinus do the arachnoid granulations project into?
Superior sagittal sinus
What structure drains CSF from the third ventricle to the fourth ventricle?
Cerebral aqueduct
What drains CSF from the fourth ventricle?
Lateral and median apertures
Where does CSF drain into from the lateral ventricles and interventricular Foramen?
To third ventricle
What occurs as a result of blockage of the ventricular system?
Upstream dilatation and potential damage to structures surrounding the dilated ventricles
Where is the most common site for ventricular system occlusions?
Blockage of cerebral aqueduct
What would be affected by blockage of the cerebral aqueduct?
Dilatation of the lateral and third ventricles but with a normal fourth ventricle
Where is the cingulate gyrus? (Images on last slide)
What is its function?
Image 4
Cortical area important for emotion and memory
Where is the central sulcus located (on images on last slide)?
Where is the primary motor cortex and then the primary sensory cortex?
Image 1
Primary motor cortex = anterior to sulcus (pre central gyrus)
Primary sensory cortex = posterior to sulcus (post central gyrus)
Where is the parieto-occipital sulcus on the images?
What structure surrounds this?
Image 5
Primary visual cortex
Where is the lateral fissure on the images?
Image 8
What is the function of projection fibres?
Connect cerebral hemispheres with the cord/brainstem and vice verse
Around what vertebral level does the spinal cord become the cauda equina?
L1
What is the shape of the grey matter in the spinal cord?
Central butterfly shape
What are the 2 large c shaped ventricles in the cerebrum of the brain?
Lateral ventricles
What is the order of CSF drainage in the brain?
Lateral ventricles
Interventricular Foramen drains them to the 3rd ventricle
3rd ventricle drains into the 4th ventricle via the cerebral aqueduct
4th ventricle drains to the median and lateral apertures which then enters into the subarachnoid space then into the arachnoid granulations in the superior Sagittal sinus into venous blood
What is the term given to dilated brain ventricles?
Hydrocephalus
What is a seizure?
Uncontrolled electrical activity in the cortex of the brain
How do seizures start at one point in the body then end up spreading?
The uncontrolled electrical activity will spread from the area it originated in the homunculus along the homunculus to the next adjacent section therefore affecting the other parts of the body
What is the homunculus and where is it located?
It represents the motor and sensory distribution along the central sulcus part of the cortex of the brain
Why does Alpha Fetoprotein (AFP) in maternal circulation indicate a Fetal anomaly?
AFP should only be found in the fetus
If its found in maternal circulation it shows its somehow leaking out which could indicate a defect like a neural tube defect
Why is gadolinium a good contrast agent for brain tumour MRIs?
It accumulates in tumours since tumours have lots of leaky blood vessels
