2: Cortical and subcortical structures of the adult healthy brain Flashcards
1.
The nervous system has two different major parts; what are they?
1) Central Nervous System (CNS): Brain and spinal cord
2) Peripheral Nervous System (PNS):
2.
What does the Central Nervous System (CNS) include?
Brain and spinal cord
3.
What are the two key parts to the Peripheral Nervous System (PNS) include?
The PNS is the part of the nervous system that consists of the nerves and ganglia outside of the brain and spinal cord.
The PNS is divided into the somatic nervous system and the autonomic nervous system.
4.
Describe the 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)
- The somatic nervous system (SoNS or voluntary nervous system) is the part of the peripheral nervous system associated with skeletal muscle voluntary control of body movements. The SoNS consists of afferent and efferent nerves.
5.
Describe the 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
6.
Name the different planes used to slice the brain:
What is the coronal plane?
A coronal plane (also known as the frontal plane) is any vertical plane that divides the body or brain into ventral and dorsal (belly and back) sections.
7.
What is a sagittal plane?
A sagittal plane is a vertical plane which passes from anterior(front) to posterior(back), dividing the body into right and left halves.
8
What is the transverse plane?
The transverse plane (also called the horizontalplane, axial plane, or transaxial plane) divides the body into superior (top) and inferior (bottom) parts. It is perpendicular to the coronal and sagittal planes.
9.
List the key brain regions divided into:
Forebrain and Brain stem
Forebrain:
- Neocortex
- Basal Ganglia
- Lateral Ventricles
- Limbic System
- Thalamus,
- Epithalamus
- Hypothalamus
Brainstem:
- Pineal body
- Third Ventricle
- Tectum
- Tegmentum
- Aqueduct of Sylvius
- Pons
- Cerebellum
- Medulla oblongata
- Fourth Ventricle
10.
What does the hindbrain consist 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
11.
What does the midbrain consist of?
MIDBRAIN includes:
- tectum(colliculi)
- tegmentum (red nuclei and substantia nigra)
- cerebral aqueduct
Image on transverse plane.
12.
The forebrain is split into 2 sections:
What are they?
Note - the Limbic system and Cerebral cortex are part of the same overal section!
Telencephalon , which contains:
- Neocortex
- Basal ganglia
- Limbic system
- Olfactory bulb
Diencephalon, which contains:
- Thalamus
- Hypothalamus
13.
Describe the neocortex
- The neocortex is made up of six layers, labelled from the outer in, I to VI.
- In humans, the neocortex is involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning, conscious thought and language.
- It is the most recent part of the cerebral cortex.
Fissure: it extends deeply into the brain
Sulcus: it is shallower Gyrus
14.
What are the 4 lobes of the neocortex?
Lobes in Hemispheres Left and RIght:
- Frontal (more developed in humans)
- Parietal
- Occipital
- Temporal
15.
What are the two main cell types in the neocortex?
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 (away) to other cerebral area; IV layer has many stellate cells – it receives afferent (receive) information from thalamus;
- The thickness of each layer varies across different cortical areas, according to the local function
- Sensory areas > thick layer IV
- Motor area > thick layer V
16.
What is CYTOARCHITECTONICS?
Cytoarchitectonics, is the study of the cellular composition of the body’s tissues under the microscope.
The variation of thickness and cell composition of each of the six layers of neocortex is known as CYTOARCHITECTONICS. On this basis Korbinian Brodmann developed Brodmann’s map.
Neocortex Brodmann map consists of 52 areas (BA).
17.
What Brodmann numbers correspond to:
- Primary motor area (cortex)
- Primary somatosensory area
- Primary Visual area
- Primary auditory area
- Primary motor area (cortex) = Area 4
- Primary somatosensory area = Area 1, 2 & 3
- Primary Visual area = Area 17
- Primary auditory area = Area 22
18
What are associative fibers?
Association fibers are bundles of axons within the brain that unite different parts of the same cerebral hemisphere.
- Arcuate fasciculus
- Uncinate fasciculus
- Superior and inferior longitudinal fasciculi
- Cingulate fasciculus
- Superior and inferior occipital frontal fasciculus
19
What are the Commissural fibres?,
They connect the same areas in the two hemispheres.
- Corpus callosum
- Anterior commissure (used in fMRI scans as landmark)
- Posterior commissure
20.
What are projection fibers?
The projection fibers consist of efferent and afferent fibers uniting the cortex with the lower parts of the brain and with the spinal cord.
They send (efferent) receive (afferent) information between the cortex and other structures of the brain (e.g. mainly thalamus through internal capsula)
21.
Primary ________ and ________ areas mediate ______________________________________
List the 5 key ares:
Primary Sensory and Motor areas mediate elementary sensory or motor functions
- Visual area
- Auditory area
- Primary somatosensory area
- Motor area
- Olfactory area
22.
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
Examples:
Lesion of primary motor cortex -> hemiparesis
Lesion of putaman -> slowness in movements
Lesion of thalamus (VL) -> ataxia
Lesion of cerebellum -> lack of motor coordination
24.
Describe the Basal Ganglia?
Then list the 4 main sections
- Basal ganglia are a group of subcortical structures which are situated at the base of the forebrain.
- 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 The four main structures:
- striatum (larger - putman, caudate nucleus)
- pallidum (globus pallidus larger component of the limbic loop of the basal ganglia)
- substantia nigra (smaller)
- subthalamic nucleus (smaller)
25.
Basal Ganglia:
Describe the Corpus Striathum
In all primates, the striatum is divided by a white matter tract called the internal capsule into two sectors called the caudate nucleus and the putamen.
The lenticular nucleus refers to the putamen together with the globus pallidus.
26.
Does the Basal Ganglia project directly to the cortex?
Draw a simple flow chart showing the direction between:
- Cerebral Cortex
- Thalamus
- Cerebellum
- Spinal Chord
- Basal Ganglia
Basal ganglia receive direct input from cortical areas and limbic system They DO NOT project DIRECTLY to the cortex. Cortical projections travel trough the thalamus.
27.
Main neurotransmitters of Basal ganglia are:
Draw a diagram illustrating their integration into the communication with other brain regions.
- GABA
- Dopamine
- Glutamate
28.
The cortex, thalamus, and the basal ganglia are the three main participants in the circuit created by the basal ganglia. Draw out the direct pathway (less inhibitory)
- Cortex (stimulates) →
- Striatum (Caudate/Putamen) (inhibits) →
- “SNr-GPi” complex (less inhibition of thalamus) →
- Thalamus (stimulates) →
- Cortex (stimulates) →
- Muscles, etc. → (hyperkinetic state)
29.
The cortex, thalamus, and the basal ganglia are the three main participants in the circuit created by the basal ganglia. Draw out the indirect pathway (MORE inhibitory)
- Cortex (stimulates) →
- Striatum (inhibits) →
- GPe (less inhibition of STN) →
- STN (stimulates) →
- “SNr-GPi” complex (inhibits) →
- Thalamus (is stimulating less) →
- Cortex (is stimulating less) →
- Muscles, etc. → (hypokinetic state)
30.
Discuss the difference between the direct and indirect pathways of the Basal Ganglia.
Draw out the full direct and indirect pathway and label it carefully.
These pathways have competing effects on movement and there is often thought to be a balance between these systems that is involved in establishing and regulating tone. In both the direct and indirect pathways, the caudate and putamen represent the first synapse in the system.
The indirect pathway is more inhibitory to motor cortical activity than the direct pathway.
31.
Malfunction or lesion of the basal ganglia.
What brain region is critical?
Parkinson Disease (rhytmical tremor at rest, bradykinesia, muscles rigidity, difficulty in stopping walking once started; difficulty in motor coordination -> falls)
Substantia Nigra.
32.
Parkinsons Disease - discuss the reasons.
- 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 pallidus more activated
- Then thalamus more inhibited
- less activation towards the cortex
- which turns into less movement.
33.
Huntington’s Chorea (jerks, muscle tone poor, possible change in personality, dementia) - what are the reasons?
- 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
37.
The __________ has a key role in transforming information to and from the cortex. It is a large _______________.
The thalamus has a key role in transforming information to and from the cortex. It is a large two-lobbed structure.
38.
What is the bridge that connects the two lobes of the thalaums?
The massa intermedia is a sort of bridge that connects the two lobes.
39.
The______________________ divides the _____ from the __________ group of nuclei.
The internal medullary lamina divides the medial from the lateral group of nuclei.
40.
___________________ forms the lateral boundary of the thalamus medial to the internal capsule, which contains _________________ nerve fibres passing to and from the ________to the _____________.
External medullary lamina forms the lateral boundary of the thalamus medial to the internal capsule, which contains afferent and efferent nerve fibres passing to and from the thalamus to the cerebral cortex
41.
The intralaminar nuclei are collections of neurons in the thalamus name three of the key parts:
- Media
- Lateral
- Anterior nuclei
42.
Describe the nuclei of the thalamus:
- Specific nuclei(Relay Thalamic Nuclei):
- Associative nuclei:
- Non-specific nuclei:
- Specific nuclei: Each specific nucleus receives connection from the region of the cerebral cortex upon which it projects (usually primary motor and sensory areas)
- Associative nuclei: Receive input from several areas and each nucleus projects to one of the three association cortex (P-T-O ass. c.; PreF c.; Limbic c.)
- Non-specific nuclei: Widespread connections also towards other thalamic nuclei and some of these are inhibitory (e.g. reticular formation)
43.
Describe the internal capsule and how it relates to other brain regions.
- 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 (a white matter sheet), which contains descending axons of the corticospinal tract.
- Lymbic System:
Name four areas of the lymbic lobe?
note: the term is ambiguous - some authors differ on what makes up the lymbic lobe.
- parahippocampal gyrus
- cingulate gyrus
- subcallosal gyrus (anterior and inferior continuation of the cingulate gyrus)
- Hippocampal formation (hippocampus, dentate gyrus and subiculum) the hippocampus
45.
Describe the lymbic system?
- The limbic system (or paleomammalian brain) is a complex set of brain structures located on both sides of the thalamus, right under the cerebrum.
46.
Main sources of limbic afferents and efferents.
Major pathways communicate bidirectionally and contain both efferent (away) and afferent (towards) fibers from the hippocampus. Outputs or efferents from the hippocampus pass directly from the subiculum to the entorhinal cortex and amygdala or through the fornix (a C-shaped bundle of nerve fibers) to a variety of anterior structures.
47.
Describe the amygdala
- The 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
48.
Describe the 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.
49.
The __________ controls the ______________________ and the ________________ with a direct link to the pituitary gland.
The hypothalamus controls the autonomic nervous system and the endocrine system with a direct link to the pituitary gland.
- The autonomic nervous system (ANS) is a division of the peripheral nervous system that influences the function ofinternal organs
- The endocrine system is the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things.
50
List 6 functions of the Hypothalamus.
- Much of the endocrine system is controlled by hormones produced by cells in the hypothalamus.
- 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
51.
Neuroimaging in computed tomography (CT):
What does 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
52.
Neuroimaging in MRI:
What does the brain looks like with T1 and T2?
The brain and related structures in MRI
