Cerebrum (Telencephalon) Flashcards
1
Q
What is the largest part of the brain?
A
cerebrum
2
Q
What are the two cerebral hemispheres separated by?
A
by a deep median fissure
- fissura longitudinalis cerebri, which is penetrated by a fold of dura mater - falx cerebri
3
Q
What does the fissura transversa separate?
A
the occipital lobes of hemisphere from the cerebellum
4
Q
What are the two hemispheres connected by?
A
corpus callosum
5
Q
What cavity is inside each hemisphere
A
lateral ventricle
6
Q
What is each hemisphere composed of?
A
basal ganglia and pallium
7
Q
Describe the basal ganglia inside the hemispheres
A
- masses of grey matter
- straited appearance - corpus striatum
- found in the infero-medial region of hemisphere, lateral to the thalamus
8
Q
Describe the pallium
A
represented by an outer layer of grey matter, the cerebral cortex, and adjacent to it, inner layer of white matter
9
Q
What subcortical structures are there by the cerebrum
A
hippocampus, basal ganglia, and olfactory bulb
10
Q
Where does the telencephalon develop from?
A
The prosencephalon or forebrain is the embryonic structure from which the cerebrum develops prenatally
11
Q
What are projection fibers
A
- projection fibers consist of efferent and afferent fibers that link the cortex with the lower/other parts of the brain and with the spinal cord
12
Q
Example of projection fiber and what tracts it is associated with
A
e. g. Corona radiata - white matter sheet of both ascending and descending axons carries most of the neural traffic from and to the cerebral cortex
- corticopontine tract
- the corticobulbar tract
- the corticospinal tract.
13
Q
What are commissural fibers
A
- or transverse fibers
- axons that connect the two hemispheres of the brain
14
Q
What is the Corpus Callosum
A
- It is the largest white matter structure in the human brain
- wide, thick nerve tract, consisting of a flat bundle of commissural fibers
- beneath the cerebral cortex in the brain
- only found in placental mammals
- It spans part of the longitudinal fissure, connecting the left and right cerebral hemispheres, enabling communication between them
15
Q
4 main parts of the Corpus Callosum
A
- four main parts; individual nerve tracts that connect different parts of the hemispheres. These are the rostrum, the genu, the trunk or body, and the splenium
- most fibers travel through CC
16
Q
Forceps minor, major and tapetum
A
- fibers of the CC radiate in the white matter and pass to the various parts of the cortex
- the fibers that curve forward from the genu into the frontal lobes are forceps minor
- those that curve backward from the splenium into occipital lobes are forceps major (or post.)
- the tapetum is the main body of fibers between these two parts
17
Q
What are commissura anterior
A
- commissural fibers
- white matter tract connecting the two temporal lobes of the hemisphere across the midline
- placed in front of the fornix
- key role in pain sensation (sharp, acute), and contains decussating fibers from olfactory tracts
18
Q
What are Commissura fornicis
A
- commissural fiber
- C-shaped
- major output tract of hippocampus
- carries some afferent to it too (from diencephalon and basal ganglia)
19
Q
Commissura posterior
A
- left and right parts of tectum and tegmentum of midbrain
- important in the bilateral pupillary light reflex.
20
Q
What are association fibers
A
- axons that connect (cortical) areas within the same hemisphere
- short fibers lie immediately beneath the grey matter of hemisphere, and connect together adjecent gyri
- Some pass from one wall of the sulcus to the other
21
Q
Long association fibers
A
- The long association fibers connect the more widely separated gyri and are grouped into bundles
22
Q
Fasciculus longitudinalis superior
A
- ass. f.
- frontal lobe to occipital lobe
- ass. f.
23
Q
Fasciculus longitudinalis inferior
A
- ass. f.
occipital to temporal lobe
24
Q
Cingulum
A
- ass. f.
- cingulate gyrus to entorhinal cortex
- ass. f.
25
Fasciculus uncinatus
4.
- ass. f.
frontal lobe to temporal lobe
26
Speech areas
27
Lateralisation of functions
28
Split brain syndrome
- the corpus callosum connecting the two hemispheres of the brain is severed to some degree
dominant hemisphere - mentions the stimulus
nondominant hemisphere - points the stimulus
anomia - can not name stimuli on the left hand
alexia in the left visual field
test - hybrid face
29
Internal Capsule
- white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain
- It carries information past the basal ganglia
- contains both ascending and descending axons, going to and coming from the cerebral cortex
- also separates the caudate nucleus and the putamen in the dorsal striatum, a brain region involved in motor and reward pathways.
- corticospinal tract is a large part of the internal capsule, carrying motor information from the primary motor cortex to the lower motor neurons in the spinal cord
- Above the basal ganglia the corticospinal tract is a part of the corona radiata, below the basal ganglia the tract is called cerebral crus(a part of the cerebral peduncle) and below the pons it is referred to as the corticospinal tract.
30
Structure of Internal Capsule
- consists of three parts and is V-shaped when cut horizontally, in a transverse plane
- the bend in the V is called the genu
the anterior limb or crus anterius is the part in front of the genu, between the head of the caudate nucleus and the lenticular nucleus
- the posterior limb or crus posterius is the part behind the genu, between the thalamus and lenticular nucleus
- the retrolenticular portion is caudal to the lenticular nucleus and carries the optic radiation (from medial part of lateral geniculate nucleus) also known as the geniculocalcarine tract
- the sublenticular portion is beneath the lenticular nucleus and are tracts involved in the auditory pathway from the medial geniculate nucleus to the primary auditory cortex (Brodmann areas 41 and 42)
- thalamolenticular portion - between thalamus and lenticular nucleus
31
Internal Capsule tracts and fibers
32
Tracts on frontal section of cerebrum
33
Basal Ganglia - what it is, what it contains, connections and functions
- masses of grey matter situated within each hemisphere
- include caudate and lentiform nucleus
- substantia nigra and subthalamic nucleus is also present
- strongly interconnected with the cerebral cortex, thalamus, and brainstem, as well as several other brain areas - major relay station
- associated with a variety of functions, including control of voluntary motor movements, procedural learning, habit learning, eye movements, cognition, and emotion.
- surrounded by white matter (internal, external and extrema capsule)
35
Components of the Basal Ganglia
- lentiform nucleus has two parts - lateral (putamen), medial (globus pallidus)
- GP (also called pallidum) is further divides into external (GPe) and internal (GPi)
- putamen and caudate nucleus united by origin, structure, function - known as striatum
36
Corpus Striatum (Neostriatum)
- a nucleus (a cluster of neurons) in the subcortical basal ganglia of the forebrain
- critical component of the motor and reward systems; receives glutamatergic and dopaminergic inputs from different sources
- serves as the primary input to the rest of the basal ganglia.
- coordinates multiple aspects of cognition, including both motor and action planning, decision-making, motivation, reinforcement, and reward perception
- The striatum is made up of the caudate nucleus and the lentiform nucleus
- The lentiform nucleus is made up of the larger putamen, and the smaller globus pallidus.
37
Substantia nigra and Subthalamic nucleus
SN - a basal ganglia structure located in the midbrain that plays an important role in reward and movement
STN - small lens-shaped nucleus in the brainwhere, it is part of the basal ganglia system
38
Division of Striatum
The striatum is a subcortical structure generally divided into the dorsal striatum and ventral striatum
- The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum
- The putamen and caudate nucleus together form the dorsal striatum
39
Caudate nucleus & Putamen
- The caudate works with the putamen to receive the input from cerebral cortex
- Collectively, they can be considered the "entrance" to the basal ganglia.
- Projections from the putamen reach the caudate directly via the caudolenticular grey bridges
40
Striosome
- striosomes (also referred to as the striatal patches) are one of two complementary chemical compartments within the striatum that can be visualized by staining
- 10-20% of total striatal mass
- low acetylcholinesterase (AchE) activity
- high substance P (SP), neurotensin (NT), tyrosine hydroxylase
- high expression of D1 dopamine receptor
- high opiate receptor
41
Matrix
- chemical compartment within striatum
- high acetylcholinesterase (AchE) activity
- high somatostatin (SRIF) activity
- high D2 dopamine receptor
42
What makes the Corpus Striatum
caudate nucleus and lentiform nucleus
43
What makes the lentiform nucleus
putamen and globus pallidus
44
Input portion of basal ganglia
Striatum (caudate nucleus and putamen)
primary input to the rest of the basal ganglia.
45
Connections in Striatum - Afferent
а. Cortex (sensimotor – gyrus paracentralis)
b. Thalamus – nucl. centromedianum, NVL, NVA
c. Substantia nigra
d. Nuclei raphe
46
Connections in Striatum - efferent
a. Pallidum [striopallidal]
b. SN [strionigral]
47
Connections of GP - afferent
а. Striatum (striopallidal fibers)
b. Nucleus subthalamicus (fasciculus subthalamicus)
c. Cerebral cortex
d. Substantia nigra
e. Nuclei raphe
48
Basal ganglia summary of connections
49
Main motor circuit of Basal Ganglia
50
Basal ganglia and pyramidal tract
51
Connections of GP - efferent
a. Common final pathway to thalamus
b. Ansa lenticularis, fasciculus lenticularis, fasciculus subthalamicus
52
Sydenharm's Chorea
Complication of Rheumatic Fever
- Fine, disorganized , and random movements of extremities, face and tongue
- Accompanied by Muscular Hypotonia
- Typical exaggeration of associated movements during voluntary activity
- Usually recovers spontaneously in 1 to 4 months
- pathologic lesion in corpus striatum
56
Lesions of basal ganglia
- Akinesia & bradykinesia - difficulty in initiation and termination of movement
- Rigidity of muscles
- Involutary movements (hyperkinesia) – tremor, tics, balism, chorea, atetosis, distonia
58
Huntington's chorea
- Predominantly autosomal dominantly inherited chronic fatal disease (Gene: chromosome 4)
- Insidious onset: Usually 40-50
- Choreic movements in onset
- Frequently associated with emotional disturbances
- Ultimately, grotesque gait and sever dysarthria, progressive dementia ensues.
- pathologic lesion: CS (caudate) and cerebral cortex
