NeuroAnatomy (P Felts) Flashcards
What is the CNS composed of?
The brain and spinal cord
What is the PNS composed of?
12 Cranial nerves and 31 pairs of spinal nerves (+ branches)
What are the first 3 swellings of the neural tube called during development?
Prosencephalon
Mesencephalon
Rhombencephalon
PRIMARY VESICLES
The Prosencephalon and Rhombencephalon divide into two further parts. What are these secondary vesicles named?
Prosencephalon = Telencephalon and Diencephalon
Rhombencephalon = Metencephalon and Mylencephalon
What does the mesencephalon become?
It remains as the mesencephalon between the diencephalon and metencephalon
What do each of the secondary vesicles give rise to in a mature brain?
Telencephalon - cerebral hemispheres Diencephalon - Thalamus and Hypothalamus Mesencephalon - Midbrain Metencephalon - Pons & Cerebellum Myelencephalon - Medulla Oblongata
What are the two main types of cell found in the CNS and what are their functions?
Neurons - communication via electrical impulses
Glial cells - “glue” the CNS together as there is no connective tissue for support
What are the 2 main types of neuron and what type of signals usually flow through each?
Multipolar - many dendrites and ONE axon extending into PNS
- MOTOR efferents travel along these
Pseudo-unipolar - cell body found in PNS
- Sensory afferents travel along these
What are the 4 main types of glial cells found in the CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
What are the main functions of each types of glial cell?
Astrocyte - supportive, maintain BBB
Oligodendrocytes - myelination in CNS NOT IN PNS
Microglia - similar to macrophages => Immune monitoring and antigen presentation
Ependymal cells - Ciliated columnar epithalium lining ventricles
Describe how oligodendrocytes myelinate nerve fibres in order to speed up the rate of electrical conduction?
Myelinate sections => leaving small gaps (called nodes of ranvier)
Electrical signals must jump over this gap, which speeds up signal conduction
How do microglia appear in their resting phase compared to a phase where they encounter an insult of infection?
Resting state = short, spiny cell processes
When activated by infection = rounder and more similar to a macrophage
Ependymal cells form a barrier between the CSF and the brain tissue. TRUE or FALSE?
FALSE
CSF can still move outwith ventricles regardless of this layer of epithelium
What are the 2 types of astrocytes and which is found in grey and white matter?
Grey matter - Protoplasmic astrocyte
White Matter - Fibrous astrocyte
What are gyri, sulci and fissures?
Gyri - bulges of cerebral hemispheres
Sulci - indentations (or sunken in parts)
Fissures - DEEP sulci
What is the difference in make up of grey matter and white matter?
Grey Matter = cell bodies of neurons, synapses and support cells
White Matter = axons of neurons, support cells
=> NO CELL BODIES
Roughly speaking where are the grey and white matter found in the brain?
Grey matter covers outside of cerebral hemispheres BUT also makes up important central structures e.g. thalamus
White matter = deep to the grey matter on outside of cerebral hemispheres
Describe the distribution of grey and white matter in the spinal cord?
Grey Matter - H shape (2 anterior horns, 2 posterior horns)
White Matter - Surronds Grey H
What is the function of the central sulcus?
Differentiates regions with different functionalities
e.g. Primary sensory and motor cortexts
Where is the Primary Somatosensory cortex located?
Post-central gyrus
Where is the Primary Somatomotor cortex located?
Pre-central gyrus
What is the corpus callosum?
Large area of white matter carrying material between the RIGHT and LEFT hemispheres of the brain
What is the relevance of the calcarine sulcus?
Marks the location of the primary visual cortex
What is contained in the fornix of the brain and what is its function?
Limbic system found here
Plays a role in memory making
What are the four traditional lobes of the brain?
Frontal
Parietal
Temporal
Occipital
What seperates the frontal and parietal lobes?
The central sulcus
What seperates the frontal and parietal lobe from the temporal lobe?
Lateral sulcus
What seperates the parietal and occipital lobes?
Parieto-occipital sulcus
This is more defined medially than it is on lateral brain
What non-traditional lobe of the brain is found concealed in the cerebral hemispheres, and what is its function?
Insular lobe (insula) - plays a role in patients experience of pain
What 3 layers make up the meninges (superficial to deep)?
- Dura mater.
- Arachnoid mater.
- *Subarachnoid space CSF**
- Pia mater.
Why is it difficult to remove the dura matter from the inner surface of the cranium?
It acts as the periosteum for the inner part of the skull
Describe how the layout of the arachnoid and pia matter create the subarachnoid space
Arachnoid matter = stretched layer over the brain
Whereas pia mater = only 1-2 cells thick, so falls into all the sulci and tightly covers gyri.
=> Space between these 2 layers contains CSF
Why are the lateral ventricles shaped the way they are?
To extend CSF into all traditional lobes of the brain
A blockage in the ventricles or their connections between each other would cause what condition?
Hydrocephalus (back up of CSF being produced)
What could potentially cause a blockage in the ventricular system?
A tumour pressing on the cerebral aqueduct
What other nervous system is often forgotten about in the body?
Enteric (digestive) nervous system
- has its own set of nerve plexuses in gut walls
- influenced by ANS
By which 2 directions is blood supplied to the brain?
- from vertebral arteries
- from internal carotids
What arteries connect the blood supply from vertebral and internal carotid arteries?
posterior communicating arteries
Roughly where do each of the 3 major cerebral arteries supply?
Anterior cerebral a. = medial brain and most of frontal lobe
Middle cerebral a. = lateral brain
Posterior cerebral a. = posterior brain
How is the majority of blood drained from the brain?
dural venous sinuses
- these then drain into the internal jugular vein
Why are there enlargements in the cervical and lumbar regions of the spinal cord?
Increased spinal tissue in these areas to deal with the limbs
At what vertebral level does the spinal cord end, and what is this structure called?
L2
“conus medullaris”
What continues after the conus medullaris in order to connect to the coccyx?
thin connective tissue cord
=> filum terminale
The meninges in the spinal cord are continuous with those in the brain. TRUE/FALSE?
TRUE
however the dura mater in the spinal cord does NOT act as periosteum for the vertebrae. They are seperated by a fat pad known as the epidural space
Describe the distribution of white and grey matter in the spinal cord
“H” of grey matter found centrally (2x anterior horns and 2x posterior horns)
White matter surrounds this
What arteries help to supply blood to the spinal cord?
3 major longitudinal arteries - 2 posterior, 1 anterior
segmental arteries - e.g. intercostal, lumbar
Radicular arteries (travel along ant/post. roots)
Embolic occlusion of any artery supplying the spinal cord can lead to areas of infarction. TRUE/FALSE?
TRUE
How is blood drained from the spinal cord?
anterior and posterior venous plexuses
How do sensory signals travel up to the primary somatosensory cortex using the dorsal column/medial leminiscus system?
3 neuron process up the ascending tracts in CNS:
1st neuron ascends in dorsal column
SYNAPSE at medulla
2nd neuron crosses midline moving from medulla to thalamus then SYNAPSES
3rd neuron stretches from thalamus to corresponding part of post-central gyrus (sensory cortex)
Why is the dorsal column split with a fissure on either side?
To differentiate sensory info coming from lower limb (medial) and upper limb (lateral)
What two main tracts are used for sensory signals ascending the spinal cord?
Dorsal Column/Medial Leminiscus System
Spinothalamic tract
What sensory signals are usually carried up the spinothalamic tracts?
pain
temperature
deep pressure
How do most somatomotor signals from the pre-central gyrus descend the spinal cord?
Via the Lateral or Ventral/Anterior corticospinal tracts
Describe how motor signals reach the spinal cord from the brain
1st neuron extends all the way from pre-central gyrus to level of effect
May cross side at medulla (85%- lateral corticospinal tract) or may continue on same side until desired level (15%- ventral corticospinal tract)
SYNAPSE at desired level
What is the internal capsule and what symptom would be experienced after a stroke in this area of the brain?
- White matter pathway (esp. for corticospinal tract)
- Carries a lot of motor and sensory information
- stroke here can result in a lack of descending control of the corticospinal tract
=> hyperflexion of upper limbs
What is the function of the tectospinal tract and what part of the brain does it involve?
- Input to cervical segments
- from tectum in posterior midbrain, down to spinal cord
- mediates head/neck movement in response to visual stimuli
What is the reticulospinal tract and what movements can it facilitate?
Tract between reticular formation (centre of brainstem) to spinal cord
Fibres in reticular formation in pons do EXTENSOR movements
Fibres in medulla do FLEXOR
What is the vestibulospinal tract responsible for and where does it span from?
- From vestibular nuclei in pons and medulla
- Excites“antigravity” extensor muscles for an impulse response (e.g. after being pushed by someone)
What are the functions of the cerebellum and basal ganglia in motor movement?
- Feedback to Motor cortex via the thalamus
- helps improve and adapt movement the body is making
What are the 3 lobes of the cerebellum?
Anterior
Posterior (largest)
Flocculonodular lobe
The cerebellum is known as a sub-tentorial organ. What does this term mean?
This is because it sits under the tentorium cerebelli
How is the cerebellum attached to the brainstem?
3 Peduncles of white matter
Superior
Middle (largest)
Inferior
The small bulges on the cerebellum are not called “gyri” like those in the cerebrum. What are they referred to as?
Folia
Describe the distribution of grey and white matter seen when the cerebellum is cut
Grey matter towards outside
White matter in “tree” shape in centre
DEEP grey matter visible inside the white matter centre
What are the 3 layers of the cerebellar cortex?
Molecular layer (outer)
Purkinje cell layer (middle)
Granule cell layer (inner)
What can be found in the molecular layer of the cerebellar cortex?
Lots of synapses
How does the purkinje layer communicate with the rest of the brain?
Has giant cell neurons with large axons which extend down to deep nuclei below the granular layer
These nuclei can then communicate with the rest of the brain
What is contained in the granular cell layer that is easily seen on histology?
Lots of neurons
Why does the pons swell anteriorly?
It is receiving/giving a lot of information from/to the cerebellum posteriorly
What is the function of the flocculonodular lobe?
It receives vestibular info which it feeds back to the brainstem
If one side of the cerebrum is affected by disease, normally the contralateral side of the body is affected. Is this the case with the cerebellum?
NO
The cerebellar hemispheres control the ipsilateral side of the body
What does the central vermis in the cerebellum control?
Autonomic movements that we dont think about
Describe the difference in effect a lesion may have depending on where in the cerebellum it is found?
Midline - affects posture control (no paralysis/weak)
Unilateral - ipsilateral affect on body
Bilateral dysfunction- ataxic gait, dysarthria (unclear speech)
What are the main functions of the basal ganglia when providing the motor cortex with feedback?
Facilitate purposeful movement
Inhibit any unwanted movement
What 5 components make up the Basal Ganglia?
Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra
How does the substantia nigra appear in the midbrain?
Looks like a black line
“black substance”
In what condition would the substantia nigra potentially NOT be present?
Parkinsons
Substantia nigra is only present when dopamine is being produced - the black colour comes from a by-product of this reaction
How does the basal ganglia signal to the motor cortex to enhance useful movement?
Direct Pathway:
=> Enhances outflow of thalamus, enhancing the desired movement
How does the basal ganglia signal to the motor cortex to inhibit a certain type of movement?
Indirect Pathway:
=> Inhibits outflow of thalamus
Lesions in the basal ganglia cause what type of symptoms?
CAUSE CONTRALATERAL SYMPTOMS
- changes in muscle tone
- dyskinesias (abnormal, involuntary movements)
e. g. tremor, chorea (rapid, asymmetrical movements of distal limbs) , myoclonus (muscle jerks)
What 2 disorders are associated with the basal ganglia, and how do they present differently?
Parkinson’s
Signs: akinesia, rigidity and resting tremor
Huntington’s:
Signs: chorea and progressive dementia
Why is the optic nerve considered more like the CNS?
- It is myelinated by oligodendrocytes rather than schwann cells
- Extends to back of eye with meninges covering like in the brain
Cranial Nerve 1 has no motor function. TRUE/FALSE?
TRUE
Only sensory
Vesicles on end of neurons pick up smell in olfactory mucosa
Where in the brain is the CN III Oculomotor nucleus found?
In the centre of the midbrain (centre deals with motor)
Why does CN IV exit the brain posteriorly after having crossed the midline?
It curves round the cerebral aqueduct before exiting the contralateral part of posterior brain
Where is the CN VI abducens nucleus located?
At base of midbrain, behind the 4th ventricle
Why do CN III, IV, VI and XII all exit the brain medially?
This is where their nuclei are in the brainstem
The all have motor portions => due to development they are found medially in brainstem
What are the 3 main parts of the trigeminal nucleus?
Spiral nucleus - extends downwards (pain/temp)
Principle nucleus - in middle at entry (touch/vibration)
Mesencephalic - upwards (chewing proprioception)
What does the trigeminal motor nucleus control and where is is located?
- Some muscles of mastication e.g. tensor veli palatini
- located behind principle nucleus
What are the 3 components of the facial nerve, and what nucleus is used to facilitate each?
- Motor (muscles facial expression). = Facial Motor nucleus
- Parasymp. = Spinal Trigeminal Nucleus/ salivatory
- Taste = Solitary nucleus
What are the 4 components of CN IX glossopharyngeal and what nucleus is used to facilitate each?
Taste = Solitary
Small region of somatosensation in ear = Spinal trigeminal nucleus
Parasymp. = Salivatory
Innervation of pharyngeal muscles = Nucleus ambiguus
What are the 4 components of the vagus nerve and what nuclei are used for these?
Parasymp. = Dorsal (motor) Nucleus
Taste = Solitary
Sensation around ear = Spinal trigeminal nucleus
Motor to some pharyngeal muscles = Nucleus Ambiguus
What shape is adopted by the solitary nucleus to provide space for many different Cranial Nerves to associate with it?
V’ shape from upper to lower medulla
What are the 3 tubes which form the spiraling cochlea?
Scala vestibuli, scala media and scala tympani
How many turns does the cochlea make in the ear?
2.5
What organ inside the cochlea is important for sounds interpretation?
Organ of corti
What does the organ of corti sit on top of and how does this help us to hear sound?
Sits on top of basilar membrane (hair cells poke up from here)
Basilar membrane varies in length and stiffness throughout cochlea => makes tip of cochlea more specific for low pitch and base more specific to high pitch
WHat other membrane brushes against the “hair” cells to turn vibrations into electrical impulses?
Tectorial membrane
What carries electrical impulses from the stimulated hair cells to the cochlear nerve?
Spiral ganglion
Describe how input from the spiral ganglion makes it way up to the primary auditory cortex
1st neuron goes from spiral ganglion to ventral and dorsal cochlear nuclei (at inferior cerebellar peduncle of brainstem)
SYNAPSE
2nd neuron ascends BILATERALLY to the superior olivary nucleus
SOME SYNAPSE BUT NOT ALL
2nd/3rd neurons travel upwards to Inferior Colliculus where ALL SYNAPSE
These signals progress up to the medial geniculate nucleus of the thalamus
AND finally to the primary auditory cortex
What two structures that are passed through in the auditory pathway of the brainstem help to localise sound?
Lateral leminiscus (white matter between nuclei) Superior olivary nucleus
They help us tell what time sound arrived at each ear, to orientate what side the sound originated from
Where in the brain is the primary auditory cortext located and how is it organised?
Located superiorly in temporal lobe
Antero-lateral part contains low frequency sounds
Posteromedial part deals with high freq. sounds
The vestibular pathway has more nuclei in the brainstem than the cochlear pathway. TRUE/FALSE?
TRUE
Damage to which specific named areas of the brain can cause “Aphasia” i.e. an inability to use language?
Broca’s area:
- difficulty producing language
- say most important words in a sentence
- no difficulty comprehending language
Wernicke’s area
- difficulty comprehending language
- speak words out of order/ use meaningless words.
Where does the vestibular nuclei connect to?
Thalamus - for conscious movement
CN III, IV and VI - for eyes to adapt to movement
Cerebellum
Lateral vestibular nucleus connects straight to spinal cord
Where in the brain is the primary vestibular cortex located?
THERE IS NO PRIMARY VESTIBULAR CORTEX
Why does the fovea have more acute vision than the rest of the retina?
layers are thinner => light easily hits photoreceptor cells
Where does the optic tract extend back to in the thalamus?
Lateral geniculate nucleus (for sight)
remember the medial geniculate nucleus is for auditory info
Does the primary visual cortex have a large or small association area?
Large
How is the visual cortex arranged at the calcarine sulcus in reference to our visual field?
Lower portion of our visual field is processed in the gyrus ABOVE the calcarine sulcus
Upper portion of our visual field = gyrus BELOW
Central vision = posterior part of these gyri
peripheral vision = anterior part of these gyri
Signals from the upper visual field have to loop around what structure embedded in the cerebral hemispheres?
lateral ventricle
this is called “Meyer’s Loop”
What two areas of the brain control eye movement?
Visual cortex and frontal eye field (motor area in frontal lobe)
What type of eye movement is controlled by the frontal eye field?
“Command” movements (e.g. telling someone to look in a particular direction = jumpy/quick movements)
What type of eye movement is controlled by the visual cortex?
smooth “Tracking” movement
What nucleus is responsible for the bilateral response in the pupillary light reflex?
Edinger-Westphal Nucleus
