Flashcards in Neuroanatomy Deck (53):
What are the components of the midbrain?
What are the components of the hindbrain?
Metencephalon & myelencephalon
What is the difference in composition of grey and white matter?
Grey matter = layers of cell bodies (but no nuclei)
White matter = axons
What is the main difference in imaging between a CT head scan and an MRI head scan?
CT head = ischaemic tissue looks the same as normal tissue
MRI head = distinguishes infarcted tissue from normal tissue
What are the main cells comprising the CNS?
What does it mean to say neuronal networks have emergent properties?
Neuronal networks (neural circuits - connections of neurones) have complex manners not seen in the individual members of the network, inc. consciousness, sensory awareness, thought processes, sensory attention, etc.
Why is there a difference between neural & vertebral levels?
Somites do not travel all the way down the vertebral column, therefore not every vertebral level is next to the corresponding neural level
Contrast the anatomy & disease states of the CNS & PNS.
Covered in meninges Covered in endoneurium,
perineurium, & epineurium
Myelin = oligodendrocytes Myelin = Schwann cells
Adaptable Dependent on CNS
++intracranial pressure nerve compression syndromes
multiple sclerosis demyelinating polyneuropathies e.g.
no capacity to regenerate capacity to regenerate after injury
glia ---> malignant tumours all tumours are benign
neurones ---> benign tumours
Describe the anatomy of the spinal cord.
Continuation of the medulla
Enlargement at cervical level (brachial plexus) and lumbar level (lumbo-sacral plexus)
Central cavity throughout length (central canal)
Ends in conus medullaris
What are the different regions of the cranial base?
ANTERIOR = alveolar arches of maxilla ---> posterior edge of hard palate
MIDDLE = posterior edge of hard palate ---> anterior edge of foramen magnum
POSTERIOR = behind middle area
What is responsible for the internal appearance of the roof of the calvaria?
- imprints of blood vessels
- foramina for emissary veins
- granular pits (where CSF moves from ventricles into venous system)
What are the different components of the telencephalon?
What are sulci? What are gyri? What are the major sulci, gyri, & projections of the brain?
SULCI = grooves or depressions in the brain (major sulci = fissures)
- LONGITUDINAL FISSURE = divides left & right hemispheres
- parietal-occipital sulcus
- calcarine sulcus
GYRI = ridges or elevations in the brain
- precentral gyrus (motor)
- postcentral gyrus (sensory)
- superior temporal gyrus
- cingulate gyrus
- parahippocampal gyrus
FALX CEREBRI & TENTORIUM CEREBELLI = downward projection of meningeal dura mater, divides left & right hemispheres and supra-tentorial & infra-tentorial compartments, secures brain, resists displacement of brain during acceleration/deceleration
TENTORIAL INCISURE = allows passage of midbrain through tentorium cerebelli
What are the components of the forebrain?
Telencephalon & diencephalon
- cerebral cortex
- basal ganglia
What are the different territories of the grey matter of the spinal cord?
Dorsal horn = sensory neurones
Ventral horn = somatic motor neurones
Lateral horn = autonomic motor neurones (bulge caused by autonomic cell bodies)
- only present at T1-L2 (sympathetic) or S2-S4 (parasympathetic)
- more grey matter present at these levels due to brachial & sacral plexuses
- autonomic ganglia are prevertebral and paravertebral
Central part & central canal = interneurones (only within spinal cord)
What is the trigeminal cave?
Cell bodies of trigeminal nerve in dorsal root ganglion
Contrast the effects of the dorsal root or ventral root entrapment.
Dorsal root entrapment ---> pain (no reduced motor function)
note: can treat by removing dorsal root (dorsal root rhizotomy)
Ventral root entrapment ---> reduced motor function (no pain)
What is the spinal cord?
Assembly of neuronal cell bodies and axons of nerves collected as bundles or fibre tracts housed in the vertebral column
What are the functions of neuronal cell bodies?
Neural level of spinal cord:
- local reflexes
- sensory functions of local neuronal segment (dermatome)
- supplying muscles of local neuronal segment (myotome)
Relaying sensory information to the brain via neurones with long axons, collected as fibre bundles which travel together
Define fibre tracts/fasciculi.
Collection of axons with similar origins and destinations which ascend to the cerebral cortex.
What are the functions of the axonal fibres of the spinal cord?
- carry sensory information from the surface of the body and muscles to the brain (ascending tracts)
- carry motor information from the brain to cell bodies of spinal motoneurones (descending tracts)
What are the rexed laminae of grey matter of the spinal cord, and why are they significant?
Divisions of the grey matter of the spinal cord equivalent to one neuronal nucleus.
Cell bodies of neurones with common functions occur in the same lamina
Which rexed laminae do pain fibres terminate in?
Laminae III & IV of the dorsal horn (nucleus proprius)
What is the collective name for the rexed laminae II & III?
What are the different components of the cerebellum? How do they differ in function?
Grey matter cortex and white matter core
- (predictive) error correction and feedback (receives copy of sensory feedback and motor plan; any differences are detected)
- movement planning
- motor learning (particularly in relation to visually guided movements and coordination of muscle activaation)
- input from vestibular system
- involved in balance and eye movements (e.g. vestibulo-ocular reflex)
Superior cerebellar peduncle ---> midbrain
Middle cerebellar peduncle ---> pons
Inferior cerebellar peduncle ---> medulla
What are the different functions of the components of the brain?
Basal ganglia = movement, reward
Hypothalamus = regulating body function
Thalamus = sensory gateway
Amygdala = emotion
Hippocampus = memory
What are the components of the lenticular nucleus?
Globus pallidus (internal & external)
What are the components of the substantia nigra?
What are the different layers of the cortex?
Layers I-VI, then white matter
Inputs to layer I from motor and sensory cortices, thalamus, and brainstem
- from layers V and VI to hippocampus, basal ganglia, cerebellum, and thalamus
- from layers I, II, and III to other cortical association areas
What are the functions of the frontal lobe?
- social conduct
- meaning of language (dominant hemisphere; Broca's area)
- motor cortex + supplementary motor cortex (sequencing movements to perform skilled tasks)
What are the signs and symptoms of frontal lobe lesions?
Personality and behavioural changes e.g.
- abulic (no will)
- laugh/cry inappropriately
- loss of social rules
- loss of empathy
Inability to solve problems
Can't modify behaviour
Perseveration = repetition of a particular response despite absence/cessation of a stimulus
- fail Stroop interference test (naming the colour of written words)
Expressive aphasia = poorly constructed sentences and disjointed speech, but can still understand commands
What are the functions of the parietal lobe?
- reading and writing, abstraction, metaphors, word-finding
- spatial awareness e.g. of self to environment, layout of world
- 2 point discrimination
- fine touch
- joint position sense
What are the signs and symptoms of parietal lobe lesions?
Contralateral neglect syndrome = inability to perceive and attend to objects/body on one side despite visual acuity, somatic sensation, and motor ability remaining intact
e.g. eating one half of a plate of food, shaving/applying makeup to one side of face
What are the functions of the temporal lobe?
Interpretation of language (Wernicke's area)
Recognition of faces and objects
Emotional response (amygdala) e.g. strangers compared to family
What are the signs and symptoms of temporal lobe lesions?
Receptive dysphasia = cannot comprehend and have fluent but unintelligible speech, loss of mathematical skills
Temporal lobe is the most common region affected in epilepsy
---> aura is funny taste/smell, visions, heightened emotions (e.g. fear, ecstasy)
---> recognition deficits (agnosias) e.g. visual/auditory prosopagnosia failure to recognise faces/sounds)
What are the functions of the occipital lobe?
Visual cortex and processing
What are the signs and symptoms associated with occipital lobe lesions?
Lesion of occipital pole ---> loss of central vision
Lesion affecting both lobes ---> cortical blindness (cannot perceive image although eyes are functional; often do not know that they are blind)
Contrast the functions of the dominant and non-dominant hemispheres of the brain (lateralisation).
Dominant (usually left)
- language (spoken/heard, written/read, gestured/seen)
- motor skills (handedness)
Non-dominant (usually right)
- emotion of language e.g. interpretation, meaning behind language
- body awareness
What are the signs and symptoms of a lesion in the corpus callosum?
Connection between hemispheres
Dominant side elicits response from written word without non-dominant side knowing why
e.g. show different instructions on left and right
What areas of the brain are involved when speaking a heard word compared to speaking a written word?
1. Primary auditory area
2. Wernicke's area
3. Broca's area
4. Motor cortex
1. Primary visual cortex
2. Wernicke's area
3. Broca's area
4. Motor cortex
Contrast the terms neural level and vertebral level.
NEURAL LEVEL = refers to the neural tissue at that level (all derived from one somite)
VERTEBRAL LEVEL= refers to vertebrae at the level
Where are the majority of pre-ganglionic parasympathetic neurones found?
Cranial space (vagus nerve)
Lateral horn at S2-S4
What landmark is used when performing a lumbar puncture in adults and in children? Why is this landmark used?
Adults: L3/L4 (supracristal plane - line joining crests of both hips)
- spinal cord tapers off at L2/L3 (conus medullaris) but vertebral canal extends to S2-S3
- "tails" of cauda equina move out of the way when the needle is advanced into the fluid
- conus medullaris is located at L3 in the newborn
Why can a fracture of T12 cause bladder paralysis?
Spinal nerves entering/leaving the foramen of lumbar and sacral vertebrae enter the spinal cord equivalent to the vertebral level T11-L1
T12 vertebral level is equivalent to S2-S4 neural level
What is the carotid sheath? What are the contents of the carotid sheath?
Extension of fascia of neck muscles
- common carotid artery ---> internal carotid artery
- internal jugular vein
- vagus nerve
- glossopharyngeal nerve
- accessory nerve
- hypoglossal nerve
What is the arterial supply of the spinal cord?
Anterior spinal artery supplies the ant. 2/3 of the spinal cord
Left and right posterior spinal arteries supply the pos. 1/3 of the spinal cord
Spinal arteries are derived from the vertebral, intercostal, and lumbar arteries (depending on the level) m
How does the composition of CSF differ from the blood?
Higher pCO2 ---> lower pH
Lower protein content
Lower glucose conc.
Low cholesterol content
Where is CSF produced and reabsorbed?
Produced by choroid plexus of lateral and 4th ventricles and ependymal cells lining the ventricular system
Diffuses, pinocytosis, active transfer into ventricular system
Reabsorbed across arachnoid villi/granulations into venous circulation (superior sagittal sinus) and lymphatics
Describe the flow of CSF.
Lateral and 3rd ventricles ---> foramen of Munro ---> 3rd ventricle ---> cerebral aqueduct ---> 4th ventricle ---> foramina of Magendie ---> subarachnoid space ---> spinal cord and superior sagittal sinus (via arachnoid villi)
CSF moves into superior sagittal sinus when CSF pressure is greater than venous pressure
Flow driven by pressure and by cilia on choroid epithelia
What is the capacity of the ventricles?
What structures pass through the foramen ovale, jugular foramen, carotid canal, and foramen magnum?
FORAMEN OVALE = mandibular nerve (CV3)
JUGULAR FORAMEN = vagus nerve
CAROTID CANAL = internal carotid artery
- spinal cord
- vertebral arteries
- ant. and pos. spinal arteries
- tectorial membranes
- alar ligaments
- spinal component of accessory nerve
What is the importance of the fontanelles and sutures of the neonatal skull during childbirth?
Fontanelles allow deformity of skull during birth to facilitate movement of skull through birth canal and allow for rapid stretching and deformation as brain expands faster than bone can grow