1) Central Nervous System (CNS): Brain and spinal cord
2) Peripheral Nervous System (PNS): see below
Somatic nervous system
It conveys sensory information (from skin, muscles, bones, joints, eyes and ears) to and from the CNS
It sends motor stimuli from CNS to muscles (voluntary movement)
Autonomic nervous system
It regulates involuntary movement activity
It controls functions such heart rate, blood pressure, kidney function and breathing
It is composed by the sympathetic and the parasympathetic nervous systems
HINDBRAIN consists of:
the MEDULLA contains important nuclei responsible for regulation of breathing and cardiac functions
the PONS contains many ascending and descending fibre tracts and fibres linked to cerebellum
the CEREBELLUM coordinates movements
tegmentum (red nuclei and substantia nigra)
Forebrain - summary
The FOREBRAIN consists of:
Telencephalo, which contains:
Diencephalo, which contains:
Forebrain - Neocortex (in Telencephalo) 1
Fissure: it extends deeply into the brain v Sulcus: it is shallower Gyrus
Hemispheres: Left and right
Lobes: Frontal, Parietal, Occipital, Temporal
It consists of 6 layers of cells, numbered from I to VI starting from the surface.
Two main cell types:
Pyramidal cells: large multipolar neurons – large dendrites and long axon – projection neurons
Stellate (or star-shaped) cells: smaller soma – shorter axon – local information processing
•Size and density of cell bodies varies across layers
For example, in Layer III large pyramidal cells – efferent to other cerebral area; IV layer rich of stellate cells – it receives afferent information from thalamus;
•The thickness of each layer varies across different cortical areas, according to the local function
9 Sensory areas thick layer IV Motor area thick layer V
Forebrain - Neocortex 2: Brodmann's map
The variation of thickness and cell composition of each of the six layers is known as CYTOARCHITECTONICS.
On this basis Korbinian Brodmann developed Brodmann’s map.
Brodmann map consists of 52 areas (BA).
(See diagram and learn main areas)
There is some correspondence between areas defined by cytoarchitectonic method and their function.
Forebrain - Neocortex 3: Fibres
Associative fibres, which connect areas within the same hemisphere:
Superior and inferior longitudinal fasciculi Cinguale fasciculus
Superior and inferior occipital frontal fasciculus
Commissural fibres, which connect same areas in the two hemispheres:
Fibres of projections, which send (efferent) receive (afferent) information between cortex and other structures of the brain
(e.g. mainly thalamus through internal capsula)
Forebrain - Neocortex 4: Primary Sensory and Motor
Primary Sensory and Motor areas mediate elementary sensory or motor functions
Primary somatosensory area
Associative areas Further process of information
Forebrain - Issues
A few important issues about cortical and subcortical areas: (Schmahmann & Pandya, 2008)
- Lesions in basal ganglia and thalamus mimic deficits resulting from cortical lesions
Due to disruption of the interaction of domain-specific subcortical nuclei with the sensorimotor, association cortical areas.
- However there are qualitative differences between the manifestations of lesions in functionally related area of cortical and subcortical areas
Lesion of primary motor cortex hemiparesis
Lesion of putamen slowness in movements
Lesion of thalamus (VL) ataxia
Lesion of cerebellum lack of motor coordination
Subcortcial areas are topographically arranged
Multiple parallel loops between cortical and subcortical areas with no cross-modal communication within subcortical nuclei
Complex behaviour required interaction between different functional domains Cortex in particular associative areas
Forebrain - Basal Ganglia (in Telencephalo) 1
Basal ganglia are a group of subcortical structures.
The main structure are:
Forebrain - Basal Ganglia 2: Function
Basal ganglia receive direct input from cortical areas and limbic system however
They DO NOT project DIRECTLY to the cortex; Cortical projections travel trough the thalamus
The function of basal ganglia is quite complex. They are strongly involved in movement and motor control.
They do NOT initiate movements but they are involved in a loop of modulation with the cortex that is constantly active.
Therefore they are actively involved in monitoring the force to be applied to a task and gross postural adjustments
Main neurotransmitters of Basal ganglia are
GABA, Dopamina and Glutamate
Forebrain - Basal Ganglia 3: Malfunctions
Malfunction or lesion of the basal ganglia:
Parkinson Disease (rhytmical tremor at rest, bradykinesia, muscles rigidity, difficulty in stopping walking once started; difficulty in motor coordination falls)
Reduction of dopamina is mainly due to death of dopaminergic neurons in the substantia nigra. This causes a lack of input (through nigrostriatal path) to putamen
then internal palllidus more activated
then thalamus more hinibeted less activation towards the cortexwhich turns in less movement.
Huntington’s Chorea (jerks, muscle tone poor, possible change in personality, dementia)
Degeneration of striatum
Reduction of GABA neurons and increment of external pallidus activity
which strongly inhibits subthalamic n.then less inhibition of the thalamus more motor activity - involuntary movements)
Ballismus or hemiballismus
(severe involuntary movements of limbs) Lesion of the subthalamic nucleus
Why involuntary movements?
In both Huntington’s Chorea and Ballismus syndromes, the involuntary movements are caused by a abnormal discharges of upper motor neurons that are not adequately inhibited (modulated) by basal ganglia.
Forebrain - Basal Ganglia 4: relationship with cor
Cerebral cortical areas (motor, association, or limbic cortex) project in a topographically arranged manner to basal ganglia.
Sensorimotor and parietal cortices dorsal and mid-sectors of the putamen
Association areas in prefrontal, posterior parietal and superior temporal cortices caudate
Orbital and medial prefrontal cortices and cingulate gyrus ventral nuclei of putamen and caudate
Behavioural-cognitive syndromes (Schmahmann & Pandya, 2008)
Lesions of the:
A) rostral head of caudate impairment of working memory, strategy, formation, flexibility, neglect if right caudate or aphasia if left caudate
B) ventral striatum Behavioural disorders (e.g. disinhibition, irritability, obsessive compulsive disorder)
Forebrain - Thalamus (in Diencephalo) 1
The thalamus has a key role in transforming information to and from the cortex.
It is a large two-lobed structure.
The m***a intermedia is a sort of bridge that connects the two lobes.
The internal medullary lamina divides the medial from the lateral group of nuclei.
External medullary lamina forms the lateral boundary of the thalamus medial to the internal capsule, which contains afferent and efferent nerve fibres p***ing to and from the thalamus to the cerebral cortex
Thalamic nuclei are divided into:
Medial, Lateral and Anterior nuclei
plus the intralaminar nuclei
Each specific nucleus receives connection from the region of the cerebral cortex upon which it projects (usually primary motor and sensory areas)
Receive input from several areas and each nucleus projects to one of the three ***ociation cortex (P-T-O ***. c.; PreF c.; Limbic c.)
Widespread connections also towards other thalamic nuclei and some of these are inhibitory (e.g. reticular formation)
Forebrain - Thalamus 2
Thalamo-cortical projections run through the internal capsule. In the internal capsule there are also the fibers from cortex to
medulla and spinal cord.
The internal capsule continues more laterally and superiorly with the corona radiata, which contains descending axons of the corticospinal tract.
Forebrain - Hypothalamus
The Hypothalamus is a complex structure containing many nuclei and tracts.
It controls the autonomic nervous system and the endocrine system with direct link to the pituitary gland.
- Much of the endocrine system is controlled by hormones produced by cells in the hypothalamus. These hormones (realising – e.g. gonadotropin- releasing hormone) “instruct” the pituitary gland to secrete the specific hormone (e.g. gonadotropic hormone)
- Descending tracts to brain stem to regulate autonomic centres related to cardiovascular and breathing functions
- Integrating emotions and autonomic responses
- Link to centre for “set points” relating to appetite, body temperature -
Biological clock and circadian rhythms
- Link to limbic system
Forebrain - Limbic System (in Telencephalo)
subcallosal gyrus (anterior and inferior continuation of the cingulate gyrus)
Hippocampal formation (hippocampus, dentate gyrus and subiculum)
Amygdala has two important projections to hypothalamus and dorso-medial thalamic nuclei and it receives an important afferent input from the olfactory tract
Emotional processing (e.g. fear) and social behaviour
Bilateral damage of amygdala results in Klüver-Bucy syndrome
CT and MRI neuroimaging
How the brain looks like?
Computed tomography (CT).
Various attenuation intensity of x-rays according to type of tissue. This is computerised into numbers.
Positive numbers (+1,000) are represented white (e.g. bone), negative numbers (-1,000) are represented black (e.g. air)
The brain and related structures in CT
Structure/fluid/space - grey scale
Bone/acute blood - very white
Grey matter - light grey
White matter - medium grey
Cerebrospinal fluid - dark grey to black
Subacute blood - light grey
CT and MRI: MRI
Structure/fluid/space T1 T2
Bone - very black - very black
Air - very black - very black
Grey matter - dark grey - light grey
White matter - light grey - dark grey
Cerebrospinal fluid - very black - very white
Edema - Dark grey - light grey to white
CT and MRI: Advantages
Advantages of CT scan:
- Clearly shows acute and subacute hemorrhages into the meningeal spaces and brain
-Better in showing bone and bone fractures
-Rapid (important for emergency) and cheap
-Advantages of MRI scan:
-Excellent spatial resolution. It better differentiates white and grey matter than CT Scan.
-It clearly shows acute or subacute infarcts or ischemia or brain edema
-No radiation exposition and, at the present, not known harmful effects
A sagittal MRI of a 23-year-old woman is located at, or immediately adjacent to, the midline. Which of the following spaces or structures would be in the image and would indicate a midline plane?
a) Cerebral aqueduct
c) Interventricular fossa