Nervous System Flashcards
what goes through the optic canal?
the optic nerve and the opthalmic artery
what goes through the carotid canal?
the internal carotid artery
what passes through the foramen magnum?
the spinal cord and vertebral artery
what are the three layers of meninges?
dura mater, arachnoid mater, pia mater
where is the subarachnoid space?
between the arachnoid layer and the pia
What would you normally expect to find in the subarachnoid space?
The subarachnoid space should contain CSF (which you will no longer be able to see) and arteries (that you hopefully will still be able to see; if you’re struggling, ask a demonstrator to show you).
what is the falx cerebri
a vertical sheet in the midline of the skull
what is the tentorium cerebelli
a horizontal sheet called the in the skull
Which parts of the brain does the falx cerebri separate?
The falx cerebri separates the left and right cerebral hemispheres of the brain
Which parts of the brain does the tentorium cerebelli separate?
The tentorium cerebelli separates the occipital lobe (above) from the cerebellum (below)
what are the dural venous sinuses?
The dura mater is formed from two sheets of connective tissues, although in most places it looks like a single layer. In some places, there are channels located between these two sheets which are responsible for venous drainage of the cranium. These are the dural venous sinuses (the veins that drain the brain). Try and identify some of these vascular channels on the bucket head dissection (e.g. the superior sagittal sinus that runs along the top of the falx cerebri).
What is the name given to the large cleft separating the two cerebral hemispheres
Great longitudinal fissure
What type of nerve fibres are most likely to be carried in the corpus callosum (e.g. association, commissural or projection fibres). Why is this?
Commissural: these fibres are responsible for connecting one cerebral hemisphere to the other
What are the three named parts of the brain which make up the brainstem?
Midbrain, pons and medulla oblongata
The thalamus, hypothalamus and pineal gland (epithalamus) are part of which larger brain structure?
Diencephalon
What is the main role of the thalamus?
The thalamus is an important ‘relay station’ for sensory (and some motor) information heading towards the cerebral hemispheres. A lesion of the thalamus (‘thalamic syndrome’) can lead to impairment of a wide range of sensory and motor functions.
On the sections of the brain, identify regions of grey matter and regions of white matter.
What is the cellular basis for the colour difference between these two regions?
White matter is comprised mainly of myelinated axon tracts, whilst grey matter is comprised mainly of cell bodies (with their dendrites) and synapses
What name is collectively given to the 12 pairs of nerves which arise mainly from the brainstem?
Cranial nerves
which lobe holds the primary motor cortex?
frontal lobe
what lobe holds the primary sensory cortex?
parietal lobe
what lobe holds the visual cortex?
occipital lobe
what lobe holds the primary auditory cortex?
temporal lobe
CT vs MRI brain
Note how the skull, therefore, appears very bright/white on the CT, but almost completely black on the MRI.
MRI - T1 ventricles = black skull white, T2 = ventricles white, flair = ventricles black skull black
What is the name given to the specialised structures lining the ventricles that generate cerebrospinal fluid (CSF)?
The choroid plexus (specialised areas of the ependymal cells that line the ventricles)
How does CSF get into the subarachnoid space from the 4th ventricle?
Through one of 3 apertures (two lateral, and one median; also known as the foramen of Luschka and Magendie respectively)
Where is CSF resorbed back into the general circulation?
Via arachnoid granulations (little sponge-like structures) located around the superior sagittal sinus (one of the dural venous sinuses)
Why does the size of the ventral grey horn vary along the spinal cord (most noticeably in cervical and lumbar regions)?
The number of cell bodies present changes – the swellings indicate an increased number of cell bodies of motor neurons required to supply the nerves going to the upper and lower limbs
How many pairs of spinal nerves are there?
31
How many pairs are there in each region of the spinal cord?
Cervical: 8 pairs
Thoracic: 12 pairs
Lumbar: 5 pairs
Sacral: 5 pairs
Coccygeal: 1 pair
Circle of willis
- Anterior cerebral a.
- Anterior communicating a.
- Ophthalmic a.
- Internal carotid a.
- Middle cerebral a.
- Posterior communicating a.
- Posterior cerebral a.
- Superior cerebellar a.
- Basilar a.
- Labyrinthine a.
- Anterior inferior cerebellar a.
- Posterior inferior cerebellar a.
- Vertebral a.
- Anterior spinal a.
Dorsal Columns sense?
(proprioception and discriminative touch)
what is in the dorsal column?
Peripheral receptor – DRG – Fasciculus cuneatus/gracillis – nucleus cuneatus/gracillis – internal arcuate fibres – medial lemniscus – VPL thalamus – internal capsule - corona radiata – post central gyrus
what does the spinothalamic sense?
Pain; Crude Touch; Temperature)
what is in the spinothalamic pathway?
Peripheral receptor – DRG – dorsal horn – ventral white commissure – spinothalamic tract of spinal cord –spinal lemniscus – VPL thalamus – internal capsule - corona radiata – post central gyrus
Where do neurons carrying sensory information for the head and neck synapse?
- Ventroposteriomedial (VPM) nucleus of the thalamus
Where do neurons carrying sensory information from the rest of the body synapse?
- Ventroposteriolateral (VPL) nucleus of the thalamus
What areas of grey matter form the boundaries of the internal capsule on a horizontal section?
- Caudate nucleus, Lentiform nucleus, Thalamus
What areas of grey matter form the boundaries of the internal capsule on a horizontal section?
- Caudate nucleus, Lentiform nucleus, Thalamus
What is the principal arterial blood supply to the sensory cortex receiving information from the lower limb?
- Anterior cerebral artery
What is the principal arterial blood supply to the cortex receiving information from the face?
- Middle cerebral artery
What is a dorsal root ganglion?
A collection of sensory neuron cell bodies outside of the CNS
C2 / C3 dermatome:
Posterior scalp and neck
C6 dermatome:
Anterior arm and thumb
T4 dermatome
Ant/Post thorax at level of 6th rib (approx.) at level of nipples
T10 dermatome:
Ant/Post abdomen at level of umbilicus
L4 dermatome:
Front of knee down to medial aspect of ankle/foot
What type of sensory information is associated with each of these brainstem nuclei?
- mesencephalic nucleus - proprioception
- chief sensory nucleus – touch and pressure
- nucleus of the spinal tract of the trigeminal – pain and temp
Trigeminothalamic fibres will then decussate in the brain stem and travel to the thalamus. Where do these fibres synapse?
- Ventroposteriomedial (VPM) nucleus of the thalamus.
There are 2 principle tracts relating to the spinocerebellar pathway:
dorsal spinocerebellar tract - axons do not decussate (cross)
ventral spinocerebellar tract – axons do decussate (cross)
What type of sensory information do you think is carried in the spinocerebellar tract?
- information about relative stretch in muscles from muscle spindles
- information about the stretch in tendons from tendon organs
- output from joint receptors
- information about pressure on skin and superficial fascia
