Neuroanatomy Flashcards
What are sulci and gyri?
Sulci are the valleys formed by the folding of the cerebrums lobar surface.
Gyri are the ridges formed.
Primary (major) sulci do not change in their appearance
Secondary (minor sulci) may vary
Where are the primary motor cortex and primary somatosensory cortex located in the brain?
Primary Motor Cortex is located on the precentral gyrus (i.e the ridge of the frontal lobe that forms the central sulcus)
Primary somatosensory cortex is located on the postcentral gyrus (i.e. the ridge of the parietal lobe that forms the central sulcus)
What is the name given to the distribution of body parts in the primary motor and somatosensory cortices?
Homunculus representation
Regarding the lateral sulcus:
a) What is sometimes referred as?
b) Which lobes does it separate?
c) What structure is located within it
a) The lateral sulcus is also referred as the sylvian fissure
b) The lateral sulcus separates the frontal and temporal lobes
c) Deep within the lateral sulcus is the insula. The insula is the primary gustatory cortex
Which structures define the middle frontal gyrus?
The middle frontal gyrus is located between the superior frontal sulcus and the inferior frontal sulcus.
The middle frontal gyrus forms the dorsolateral prefrontal cortex - largely responsible for executive functions of the human brain
Outline the major primary sulci and the functions associated to the with the following key brain regions
- Dorsolateral prefrontal cortex
- Cingulate gyrus
- Orbitofrontal cortex
- Primary auditory cortex
- Inferior parietal lobe
- Primary striate cortex
- Superior frontal sulci and inferior frontal sulci. Form middle frontal gyrus that makes dorsolateral prefrontal cortex. Executive function occurs here
- Cingulate gyrus formed from cingulate sulcus on the medial side of frontal lobe. Motivation is the function here.
- On the inferior side of frontal lobe the olfactory sulcus and orbital sulcus are located. This is around the orbitofrontal cortex where associative learning and decision-making takes place.
- Superior temporal sulcus forms the superior temporal gyrus (on the top of the temporal lobe inferior to the lateral sulci). The primary auditory cortex is located here.
- The inferior parietal lobe is formed from the interparietal sulcus (separates parietal into superior and inferior lobes). Inferior paritetal lobe itself is formed from angular gyrus and supramarginal gyrus. The function is visuospatial attention.
- The primary striate (visual cortex) is located in the medial occipital cortex. The calcarine sulcus forms this.
How can we identify the dominant hemisphere?
The hemisphere contralateral lateral to the dominant hand but not always!
The dominant hemisphere mediates language and speech functions
What scales can be used to dominance?
Annette’s handedness scale
Edinburgh handedness inventory
Note these scales better assess dominance as handedness does not always correlate to dominance. 10% of right handed individuals the right hemisphere is dominant (mostly contralateral). However for L handed individuals 64% the L hemisphere is dominant (ipsilateral). 20% have R hemisphere dominance and 20% have bilateral dominance,
What is the planum temporale?
It is a triangular region on the superior temporal gyrus (note primary auditory cortex) important for language processing.
It is known to be very asymmetric with larger size on L > R hemisphere (in 65% of individuals).
In schizophrenia this asymmetry may be reduced or reversed.
Outline some functional deficits that can occur with L or R or bilateral lesions?
L hemisphere:
- Aphasia
- Right-left disorientation
- Finger agnosia (inability to name, move or identify fingers instructed by examiner)
- Dysgraphia (aphasic)
- Dyscalculia (number alexia)
- Limb apraxia
R hemisphere:
- Visuospatial deficits
- Anosognosia
- Neglect
- Dysgraphia (spatial, neglect)
- Dyscalculia (spatial)
- Constructional apraxia, dressing apraxia
Bilateral: face recognition
Higher level functions usually lateralise to one hemisphere.
Fundamental brain functions are bilateral)
Name some neuroscientist that originally defined the limbic system and what constitutes the Papez circuit?
Papez, Maclean and Broca
Papez circuit:
- Hippocampus -> fornix –> mamillary bodies -> mamilthalamic nucleus -> genu of internal capsule -> cingulate gyrus -> parahippocampal gyrus -> preforant pathway -> back to hippocampus
Regions later added to limbic system:
- Orbitofrontal cortex
- Amygdala
- Septum
- Basal forebrain
- Nucleus accumbens
Name some functions of the limbic system
- Emotional processing
- Coordination of neuroendocrine response (via hypothalamus)
- Coordination of reward processing via nucleus accumbens
Outline the medial temporal structures?
- Hippocampus
- Amygdala
- Enterohinal cortex
- Parahippocampal cortex
Outline the functions of the basal ganglia
- Coordinating movement
- Turning abstract thought into a voluntary response
They are a group of grey matter nuclei that form the largest subcortical structure in the brain
What structures make up the basal ganglia?
- Striatum (caudate nucleus + putamen)
- Pallidum (globus pallidum)
Putamen + Globus Pallidum = Lentiform/Lenticular nucleus
Although the subthalamic nuclei and substantia nigra functionally relate to the basal ganglia they are not structurally included
Name 5 circuits that involve the basal ganglia
Motor circuit
Ocular circuit
Lateral orbitofrontal circuit (social intelligence)
Dorsolateral prefrontal circuit (executive)
Anterior cingulate circuit (motivation)
- basal ganglia receives inputs for these circuits from glutamatergic corticostriatal projections (cerebral inputs from cortex to the striatum)
Outline some disorders associated with basal ganglia changes and if you can what are the changes?
OCD
- Volumetric changes and higher blood flow to the caudate nucleus. Effective treatment reduces metabolism in the caudate nucleus
Tourette’s syndrome
- Strital dopaminergic dysfunction
Huntington chorea
- The striatum (caudate nucleus mainly) degenerates and loss of GABAergic neurons
Wilson Disease
- Copper deposits in the lenticular nuclei (putamen and globus pallidum)
CO poisoning
- Bilateral anoxic damage to the basal ganglia
Hemiballismus
- Subthalamic nucleus damage (infarction)
Parkinsonisms
- Depigmentation of substantia nigra, lewy bodies. Striatum overactivity correlated with bradykinesia changes
Fahr’s disease
- Calcium deposits in basal ganglia. Early onset -> Schizophreniform psychoses and catatonia. Later onset -> dementia and choreathetosis.
What is the function of the thalamus?
Relaying all sensory information (except olfactory) to the cortex. Other information relayed is cerebellar and basal ganglia information
The thalamus also filters appropriate sensory information before it passes on to the cortex
The thalamus is a oval shaped ball of grey matter nuclei in the subcortical region
How do the anterior thalamus and pulvinar help with the function of the thalamus
Anterior thalamus connects information to the hypothalamus and hippocampus to the frontal cortex. Anterior thalamus recieves information from the fornix and mamillothalamic tract and connects it the cingulate gyrus (cortex)
The pulvinar helps with visual attention. Sleep spindles are generated in the reticular nucleus of the thalamus
Outline some functions of the hypothalamus
Regulating physiological processes - sleep, temperature control, eating and drinking
Chemoreceptors in the hypothalamus are triggered by changes in blood glucose, osmolarity or accidity
The hypothalamus coordinates neuroendocrine responses
The ventromedial hypothalamus is the satiety centre the lateral hypothalamus is the feeding centre.
Lesions of the ventromedial hypothalamus lead to obesity and hyperphagia in animals
What is cognitive dysmetria?
Difficulties in coordinating and processing:
- Receiving, processing and relaying information that could cause disrupted cortico-cereballar ciruitry.
- Noted to be present in Schizophrenia
What is the role of the cerebellum?
Preparing motor activity and balance
Cerebellar lesions cause ataxia, intentional tremors, hypotonia, past pointing and pendular knee jerk (knee moves several times after the initial jerk)
What structures make up the brainstem?
Midbrain;
- Super colliculi (conjugate gaze control)
- Inferior colliculi (Auditory source localisation)
- Substantia Nigra
- Periaquedatal matter (vocalisation of threat, freezing and pain suppression)
Pons (beneath cerebellum and superior part of 4th ventricle)
Medulla (inferior part of 4th ventricle and runs alongside spinal cord)
What is appendicular ataxia?
Ataxia of the arm and leg contralateral to the side of the inferior olivary nuclei lesion
These patients fail the finger point test however are different to cerebellar lesions where the ipsilateral side is affected
The inferior cerebellar peduncle communicates motor coordination from connecting fibres to the contralateral cerebellar cortex
How does the structure of the spinal cord differ from the cerebrum?
In the spinal cord grey matter is deep inside forming an H shaped structure
The white matter forms anterior, lateral and dorsal columns
The dorsal column carries proprioreceptive information
The anterior and lateral columns carry ascending spinothalamic tract which carries pressure, touch heat and pain sensations
What does the choroid plexus do?
Secretes protein in the lateral, 3rd and 4th ventricles
Describe the route that CSF travels from the lateral ventricles to the subarachnoid space
Lateral ventricles - 3rd ventricle (inter-ventricular foramen of Monroe)
3rd ventricle - 4th ventricle (aqueduct of Sylvius)
4th ventricle to subarachnoid space (foramen of Magendie (single) and foramen Lushka (two lateral)
How do the pathology of non-communicating and communicating hydrocephalus differ
Non-communicating hydrocephalus commonly occurs through blockage of foramen of Monroe (interventricular)
Communicating hydrocephalus often arises from partial blockage and lack of CSF reabsorption from arachnoid vili
Describe the cranial nerve functions?
I Olfactory Runs on the basal surface of frontal cortex without passing through the thalamus. Formed as an outgrowth of forebrain
II Optic Also an outgrowth of the forebrain. Relays via thalamus (geniculate body)
III Oculomotor Purely motor function. Supplies four of the six ocular muscles
IV Trochlear Purely motor function. Supplies superior oblique (ocular muscle)
V Trigeminal Both sensory and motor. Transmits facial sensation and controls jaw muscles
VI Abducens Purely motor function. Supplies lateral abducens (ocular muscle)
VII Facial Both sensory and motor. Transmits taste sensation and controls facial muscles
VIII Vestibular Transmits auditory sensation. Cochlear Transmits balance sensation
IX Glossopharyngeal Motor control of pharynx; parasympathetic control of the parotid gland; taste from the back of the tongue.
X Vagus Motor control of larynx and pharynx; parasympathetic control of the viscera; visceral sensations.
XI Accessory Motor control of neck muscles
XII Hypoglossal Motor control of tongue muscles
Descries the position of the white matter tracts in the spinal cord and what does each carry
Dorsal - proprioreceptive sensation
Anterior & lateral - ascending spinothalamic tracts (pressure, heat, touch, pain sensations)
White matter tracts are outside the inner grey matter (H shaped)
Descries the position of the white matter tracts in the spinal cord and what does each carry
Dorsal - proprioreceptive sensation
Anterior & lateral - ascending spinothalamic tracts (pressure, heat, touch, pain sensations)
White matter tracts are outside the inner grey matter (H shaped)
What parts of the brain are supplied by the:
- Anterior cerebral
- Middle cerebral
- Posterior cerebral
- Anterior cerebral –> medial and superior strips of lateral cerebral cortex (up to parietal/occipital border)
- Middle cerebral –> lateral aspect of cerebral hemisphere’s including Wernicke’s and Broca’s
- Posterior cerebral artery (basillar) –> inferomedial temporal lobe and occipital lobe
- Pons is supplied by basilar artery
- Medulla is supplied by posterior inferior cerebellar arteries and anterior spinal branches of vertebral arteries
Describe the deficits witnessed in a TIA of carotid system vs TIA of vertebrobasilar system
Carotid (anterior):
- Amaurosis fugax (blockage of retinal artieries)
- Aphasia
- Hemiparesis
- Hemisensory loss
- Hemianopic visual loss
Vertebrobasilar (posterior circulation):
- Dipolpia, vertigo, vomiting
- Choking, dysarthria
- Ataxia
- Alexia without agraphia
- Hemisensory loss
- Hemianopic visual loss
- Transient global amnesia
- Tetraparesis
- Loss of consciousness (rare)
Describe the deficits witnessed in a TIA of carotid system vs TIA of vertebrobasilar system
Carotid (anterior):
- Amaurosis fugax (blockage of retinal artieries)
- Aphasia
- Hemiparesis
- Hemisensory loss
- Hemianopic visual loss
Vertebrobasilar (posterior circulation):
- Dipolpia, vertigo, vomiting
- Choking, dysarthria
- Ataxia
- Alexia without agraphia
- Hemisensory loss
- Hemianopic visual loss
- Transient global amnesia
- Tetraparesis
- Loss of consciousness (rare)
