Session 1 Flashcards
What are the components of the CNS?
- Cerebral hemisphere
- Brainstem
- Spinal cord
What are the components of the PNS?
- Dorsal and Ventral Roots
- Spinal nerves
- Peripheral nerves
What are the features of the grey matter in the CNS?
- Highly vascular due to computational role
- Grey matter contains axons to communicate with the white matter
- Grey Matter contains axons to communicate with the white matter
- Has no fat (myelin)
- Grey matter is composed of cell bodies and dendrites
What are the features of the white matter in the CNS?
- White matter matter is composed of axons with their supporting cells
- White matter is white due to the presence of fatty myelin
What are the features of the the PNS?
- Has ganglion instead of Grey matter
- Has a Peripheral Nerve which is the equivalent of white matter
How many segments does the spinal cord have and what is their purpose?
- 31 segments
- Each supplies a given dermatome and myotome on each side
- Each segment is connected to a spinal mixed nerve through dorsal sensory and ventral motor roots
What is the spinal cord made of?
- Central core of grey matter
- Outer shell of white matter
How are dermatome and myotomes useful?
They allow localisation of lesions to a given cord segment
What does the fasciculus cuneatus supply?
-Subdivision of dorsal column tract supplying upper half of the body (apart from head)
What does the fasciculus gracilis supply?
-Subdivision of dorsal column tract supplying lower half of the body
What is a tract?
-An anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter. Impulses travel in one direction
What is a fasciculus?
-Subdivision of a tract supplying a distinct region of body
What is a nucleus?
-A collection of functionally related cell bodies
What is the cortex?
-A folded sheet of cells bodies found on the surface of a brain structure. Typically 1-5mm thick
What is a fibre (white matter)?
-A term relating to an axon in association with its supporting cells. Used synonymously with axon
What are Association Fibres?
Association fibres connect cortical regions within the same hemisphere
What are Commisural Fibres?
Commissural fibres connect left and right hemispheres or cord halves
What are Projection Fibres?
Projection fibres connect the cerebral hemispheres with the cord/brainstem and vice versa
What is the purpose of the midbrain?
Eye movements and reflex response to sound and visiion
What is function of the Pons?
- Feeding
- Sleep
What is the purpose of the medulla?
- Cardiovascular centre
- Respiratory centre
- Contains a major motor pathway (medullary pyramids)
What is the central sulcus?
- Sitting in the coronal plane
- Key landmark separating frontal and parietal lobes
- Demarcates the pre-central gyrus and post central gyrus.
- Travels from the lateral sulcus to the midline unimpeded.
What is the pre-central gyrus?
-Contain the primary motor cortex
What is the post-central gyrus?
-Contains the primary sensory cortex
What is the lateral/sylvian fissure?
-Separates temporal from frontal/parietal lobes
What is the parieto-occipital sulcus?
-Seperates the parietal from occipital lobes
What is the calcarine sulcus?
-Primary visual cortex surrounds this
What is the optic chiasm?
-A site where fibres in the visual system cross over
What is the uncus?
-Part of the temporal lobe that can herniate, compressing the midbrain. Important olfactory role
What is a medullary pyramids?
Location of descending motor fibres
What is the parahippocampal gyrus?
Key cortical region for memory encoding
What is the corpus callosum?
Fibres connecting the two cerebral hemispheres
What is the thalamus?
Sensory relay station projecting to sensory cortex
What is the Cingulate gyrus?
Cortical area important for emotion and memory
What is the Hypothalamus?
Essential centre for homeostasis
What is the Fornix?
Major output pathway from the hippocampus
What is the tectum?
Dorsal part of the midbrain involved in involuntary responses to auditory and visual stimuli
What is the cerebellar tonsil?
Part of the cerebellum that can herniate and compress the medulla. Herniation through foramen magnum due to increase in intracranial pressure. Can result in death
What does a sensory deficit in a dermatomal pattern suggest?
-Lesion at the level of the dorsal roots or spinal nerves
What does a sensory deficit across multiples segments suggest?
-A cord lesion
What does a sensory deficit in a homunculus pattern suggest?
-Lesion above the thalamus
What is a funiculus?
-Large block of white matter containing multiple distinct tracts which both ascend and descend. Impulses travels in multiple directions
What does the dorsal funiculus contain?
-Dorsal column tract (ascending)
What does the lateral funiculus contain?
-Contains the lateral corticospinal tract (descending)
What does the ventral funiculus contain?
Ventral corticospinal tract
How are cell bodies of grey matter organised?
-Cell columns within the cord. These regions of grey matter were organised by Rexed into laminae
What are ventricles?
- Cavities that are found within the brain
- Ventricles contain choroid plexus which is highly vascular and makes a total of 600-700ml of CSF per day
What are the functions of CSF?
- Mechanical functions such as providing shock absorption for the brain and rendering it effectively weightless
- Metabolic functions such as containing glucose and maybe even hormones
How does CSF get into venous blood?
- Circulates through ventricular system and subarachnoid space
- Then it is reabsorbed at the arachnoid granulations
- Arachnoid granulations resemble little cauliflowers, projecting into the superior sagittal sinus. CSF cross the wall of granulation and enters the venous blood
How does CSF flow through brain ventricles?
- Most CSF is made in the large lateral ventricles
- From the lateral ventricles to interventricular foramen then into the third ventricle
- CSF drains from the third ventricle to the fourth ventricle via the cerebral aqueduct (in the midbrain)
- The fourth ventricle sits beneath the cerebellum, and CSF can drain from it via the lateral (of Luschka) and median (of Magendie) apertures
- These apertures permit CSF to drain from the ventricular system into the subarachnoid space. There is negligible drainage via the spinal cord central canal
- Once in the subarachnoid space, CSF is reabsorbed in the granulations
What does blockage of part of the ventricular system lead to?
-Upstream dilatation and potential damage to structures surrounded the dilated ventricles.
Which part of the ventricle is commonly occluded and what is the effect of it?
- Cerebral aqueduct maybe due to congenital stenosis or tumour
- Blockage of the Aqueduct would cause dilatation of the lateral and third ventricles but with a normal fourth ventricles
