General anatomy of the brain Flashcards
1
Q
Cerebrum
A
- has 4 major lobes ( frontal, temporal, parietal and occipital lobes)
- lobar surface is heavily folded forming sulci (valleys) and gyri (ridges)
- Primary (major) sulci are more invariant in their appearance than the secondary (minor sulci)
2
Q
Central sulcus
A
-divides frontal lobe from the parietal lobe
3
Q
Precentral gyrus
A
- primary motor cortex
- part of the frontal lobe
- homunculus represents the different parts of the body
4
Q
Post-central gyrus
A
- part of the parietal lobe
- the primary somatosensory cortex with a similar homunculus representation
5
Q
Lateral sulcus
A
- Sylvian fissure
- divides frontal lobe from the temporal lobe
6
Q
Insula
A
- a structure sometimes regarded as the 5th lobe of the cerebrum
- located deep in the Sylvian fissure
- where primary gustatory cortex is found
7
Q
Dorsolateral prefrontal cortex
A
- in between the superior and inferior frontal sulci is the middle frontal gyrus and this has the dorsolateral prefrontal cortex in it
- executive functions of the human brain
8
Q
Cingulate sulcus
A
- on the medial side of the frontal lobe
- the anterior portion of the adjoining cingulate gyrus is considered to be the seat of motivation
9
Q
Orbitofrontal cortex
A
- olfactory and orbital sulci are on the inferior surface of the frontal lobe
- the orbitofrontal cortex is often considered to be the seat of associative learning and decision-making
10
Q
Primary auditory cortex
A
-is in the superior temporal sulcus ( in lateral sulcus)
11
Q
Inferior parietal lobe
A
- made of the angular gyrus and supramarginal gyrus
- is considered to be important for visuospatial attention
- interparietal sulcus separates suiperior and inferior parietal lobes
12
Q
Primary visual (striate) cortex
A
-in the calcarine sulcus in the medial occipital cortex
13
Q
Left temporal cortex
A
language comprehension
14
Q
Right hemisphere
A
language prosody (tonal modulation of speech)
15
Q
Dominant hemisphere
A
- hemisphere contralateral to the dominant hand is the dominant hemisphere
- mediates language and speech functions
- dominance can be tested using Annette’s handedness scale or Edinburgh handedness inventory
- handedness is not always same as dominance
- in 10% right handed people, the right hemisphere is dominant
- left-handed people only 20% are right hemisphere dominant, 64% are left hemisphere dominant and 16% show bilateral dominance
16
Q
Planum temporale
A
- triangular region in the upper surface of the superior temporal gyrus
- important for language learning
- larger on the left than the right hemisphere in 65% brains
- it can be very asymmetrical
- reduced or reversed asymmetry in schizophrenia
17
Q
Left Hemisphere Lesion
A
- aphasia
- right-left disorientation
- finger agnosia
- dysgraphia (aphasic)
- dyscalculia (number alexia)
- limb apraxia
- facial recognition
18
Q
Right Hemisphere lesions
A
- visuospatial deficits
- anosognosia
- finger neglect
- dysgraphia (spatial, neglect)
- dyscalculia (spatial)
- constructional apraxia
- dressing apraxia
- facial recognition
19
Q
Papez circuit
A
Limbic structures involved in emotional processing
hippocampus=> fornix==>mamilliary bodies==>mammillothalamic tract==>anterior thalamic nucleus==>genu of the internal capsule==>cingulate gyrus==> parahippocampal gyrus==> entorhinal cortex==> perforant pathway==>back to hippocampus
20
Q
Limbic system
A
- described by Broca, Papez and Maclean
- after Papez circuit, this was expanded to include amygdala, septum, basal forebrain, nucleus accumbens and orbitofrontal cortex
- involved in mediation of emotional responses, influencing neuroendocrine responses and reward system regulation
- evolutionarily older than the higher cortical centres
21
Q
Medial temporal structures
A
- include the hippocampus, amygdala, entorhinal and parahippocampal cortex
- plays role in memory processes
- few areas where the continuous production of new neurons is noted even in adult life
- amygdala appears crucial for fear conditioning and emotional regulation
22
Q
Basal ganglia
A
- basal ganglia are a group of gray matter nuclei forming the largest subcortical structure in the brain
- they are involved in planning an dprogramming of movement and also have a role in the processes by which an abstract thought is converted into voluntary action
- consists of the striatum (made up of the caudate nucleus and putamen) and pallidum ( globus pallidus)
- putamen and globus pallidus are sometimes called lenticular/ lentiform nucleus
23
Q
Striatum
A
- made of caudate nucleus and putamen
- part of the basal ganglia
24
Q
Lenticular/lentiform nucleus
A
-putamen and globus pallidus
25
Subthalamic nuclei and the substantia nigra
-functionally related to the basal ganglia but are not considered part of the basal ganglia
26
Corticostriatal projection
-basal ganglia receives crucial inputs from the glutamategic corticostriatal projection
27
Circuits involving the basal ganglia
- described by Alexander
- motor circuit
- oculomotor circuit
- dorsolateral prefrontal circuit (executive)
- anterior cingulate circuit (motivation)
- lateral orbitofrontal circuit (social intelligence)
28
OCD
-basal ganglia dysfunction: volumetric changes and higher blood flow to the caudate nuclei. Increased caudate metabolism in untreated subjects reduces after effective treatment
29
Tourette's syndrome
-basal ganglia dysfunction: striatal dopaminergic dysfunction
30
Huntington chorea
-basal ganglia dysfunction: degeneration of the striatum (mainly caudate nucleus) and selective loss of GABAergic neurons
31
Wilson's disease
-basal ganglia dysfunction: copper deposits in the lenticular nuclei
32
CO poisoning
-basal ganglia dysfunction: acute bilateral anoxic damage to basal ganglia
33
Hemiballismus
- basal ganglia dysfunction: subthalamic nucleus damage (especially in infarction)
- flailing limb movements
34
Parkinsonism
- depigmentation of substantia nigra
- Lewy bodies are seen
- Striatal overactivity associated with bradykinesia
35
Fahr's disease
- 'Fahr too much ccalcium in the basal ganglia'
- progressive calcium desposition in the basal ganglia
- early onset cases present with schizophreniform psychoses and caratonia
- later onset cases exhibit dementia and choreoathetosis
36
Thalamus
- large oval mass of grey matter nuclei in the subcortical region, relaying all types of sensory information onto cortex (except olfaction)
- it also relays cerebellar and basal ganglia imputs to the cerebral cortex
- plays a crucial role in the filtering of sensory information in preparation for cortical processing
37
Anterior thalamus
- part of the limbic system
- receives the mamillothalamic tract and fornix and connects to the cingulate cortex
- thus it relays information from hypothalamus and hippocampus onto the frontal cortex
38
Pulvinar
- associated with visual attention
| - sleep spindles are generated in the reticular nucleus f the thalamus
39
Hypothalamus
- regulates physiological functions such as eating, drinking, sleeping and temperature regulation
- hypothalamus has chemoreceptors that respond to variations in glucose levels, osmolarity, acid balance etc
- it plays a major role in neuroendocrine control
40
Ventromedial hypthalamus
- acts as the satiety centre
| - animals with a lesion of the ventromedial hypothalamus hyperphagia and obesity are noted
41
Lateral hypothalamus
-the feeding centre
42
Cerebellum
- important role of preparing a motor plan and predicting balance needed between muscle groups to carry out the intended action smoothly
- cerebellar lesions produce ataxia and coarse intentional tremors along with hypotonia, past pointing and pendular knee jerk
- may have a cognitive role
43
Cognitive dysmetria
- Andreasen
- refers to the difficulty in coordinating and monitoring the process of receiving, processing and expressing information that could result from disrupted cortico-cerebellar circuitry in schizophrenia
44
Brainstem
- midbrain, pons and medulla
| - 9 out of 12 cranial nerves enter or exit the brain from the brainstem
45
Midbrain
-consists of superior (conjugate gaze control) and inferior colliculi (auditory source localisation)
46
Substantia nigra
- also located in the midbrain along with the periaqueducal grey matter
- important role in vocalisation and freezing response to threat and in pain suppression
47
Pons
-positioned beneath the cerebellum and surrounds the upper half of the 4th ventricle
48
Medulla
-surrounds the inferior part of the 4th ventricle and is continuous with the spinal cord
