Basics to know Flashcards
Label these different viewing segments of the brain
Label these orientations of the head
top down- horizontal
plane of face- coronal
side on view- sagittal
Label the areas of the cerebral hemispheres
Label the brain vesicles
Forebrain (telencephalon and diencephalon)
Midbrain (mesencephalon)
Hindbrain (metencephalon and myelencephalon)
What are the folds in the cerebral hemisphere called?
Gyri
and the sulci are the grooves between the folds
Name the 4 major subdivisions of the diencephalon
The four major subdivisions of the diencephalon include the thalamus, hypothalamus, subthalamus, and the epithalamus
What is the central core of the cerebral hemisphere?
The diencephalon
How many ventricles are there in the brain?
There are 4
2 lateral, 3rd and 4th ventricle
Tell me about the organisation of the ventricles
The ventricles are continuous with each other and are filled with CSF
What is the Ventricular size indicative of?
Ventricular size can be indicative of cortical atrophy (neurodegeneration)
Whats associated with ventricular enlargement?
Neurodegenerative diseases
What are ventricles filled with and where is this secreted from?
The ventricles are fluid filled with CSF
CSF is secreted from specialised capillaries called Choroid Plexus
The Choroid plexus line the ventricles
Is ventricular size associated with psychiatric disorders as well as neurodegenerative diseases?
Ventricular size is hard to detect in psychiatric disorders which make them hard to observe. There are slight changes but they are at a very small level
What are the cortical areas subdivided into?
Cortical areas are divided into lobes
Name the lobes of the brain?
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
What are the association cortexes?
Association cortex are the regions of the brain that aren’t assigned any specific function in the brain. This is about 90% of the brain. It is involved in integrating information based on past experience and memory. Taken to frontal lobe which then makes the executive decision
Name the cortexes associated with each of the lobes
- Primary motor cortex
- Primary sensory cortex
- Visual cortex
- Auditory cortex
Are the two hemispheres of the brain equal in size?
There is asymmetry between the cerebral hemispheres
Label these sulci and gyri structures
Whats the Corpus callosum?
A band of fibres that connects the left and right cerebral hemispheres
How do the left and right cerebral hemispheres differ in their specialisations
Left is more specialised for verbal and linguistic tasks and right is for special (simple but what experiment showed)
Tell me about how the lateralisation of the brain varies in patients with schizophrenia
Not the same lateralisation of brain function between left and right in patients with schizophrenia which could explain cognitive function lack
What lobes are the following functional areas in:
- Motor lobe
- Sensory lobe
- Visual lobe
- Occipital lobe
Motor: Frontal lobe
Sensory: Parietal lobe
Auditory: temporal lobe
Visual: occipital lobe
What is the role of the frontal lobe?
- voluntary movement
- expressive language
- managing higher level executive functions i.e., collection of cognitive skills like organisation, self motor, goal setting
Whats the roles of the parietal lobe?
- sensory perception and integration
Whats the roles of the temporal lobe?
- processing affect/ emotions
- language
- certain aspects of visual perception
- the dominant temporal lobe on the left, is involved in understabding language and learning and remembering verbal information
Whats the roles of the occipital lobe?
- Visual processing
- distance and depth perception
- colour determination
- face recognition
- memory formation
Whats the roles of the motor cortex?
This is a region of the cerebral cortex involved in the planning, control and execution of voluntary movements
Classically, the motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately anterior to the central sulcus.
Whats the roles of the sensory cortex?
The sensory area of the brain recieves and processes sensory information
Whats the roles of the Visual cortex?
The primary purpose is to recieve, segment and integrate visual information
The processed information from this cortex is sent to other regions of the brain to be analysed and utilised
What are the roles of the auditory cortex?
This cortex plays a critical role in our ability to perceive sound
What did Roger Sperry recieve his nobel prize for in 1981?
Describe some ideas from this experiments and how that helped come to his conclusion
- Performed ‘split-brain’ experiments in 1959-1968 where he performed different experiments on cats, monkeys and humans with a severed corpus callosum
- He was studying the functional differences between the two brain hemispheres
- In cats and monkeys he found out that if the hemispheres werent connected then they would function independently of one another aka. split brain
- He found that the left hemisphere interpretated language whilst the right could only recognise language but could not interpret it
- chemoaffinity hypothesis: neurons make connections with their targets based on interactions with specific molecular markers
What is the main role of the thalamus?
Its a ‘relay station’ for sensory informaton
What is the relationship between the thalamus and the neocortex?
The thalamus provides all parts of the neocortex with afferents, and, in turn, the thalamus recieves input to the cortex
What is the neocortex?
The neocortex is part of the human brain’s cerebral cortex where higher cognitive functioning is thought to originate from
What loop is the thalamus part of in the orbitofrontal cortex and what does this play a role in?
The cortico-striatal-thalamis loop circuit
This loop is important in controllling the input to the cortex
With sensory information such as touch, where does the thalamus project this sensory information?
The Ventral posterior nuclei relay information regarding touch and perception of bodily position to the primary somatosensory cortex in the cerebral cortex
What is the Reticular activating system?
This is a network of neurons that extends from the medulla —> lower midbrain
It carriers non-specific information about alertness and arousal
Its present in the brain stem
Tell me about axon collaterals
An axon typically develops side brances called axon collaterals
This is so one neuron can send information to several others
Axon –> Axon collaterals –> terminal branches (each has a synaptic terminal on the tip)
What is the basal ganglia involved in?
Extrapyramidal motor control and coordination
Label the structures of the basal ganglia…
Tell me the main roles that the basal ganglia has
- fine tuning of volunary movement
- intitiation of movement
- smooth execution of movement
What two features of the basal ganglia form the striatum and what is its appearance like?
The Caudate and Putamen form the striatum
They have fibre tracks along them which gives them a stripy appearance
Tell me about the appearance of the Substantia Nigra and why it is this way
The Substantia nigra is dark in appearance because it is where melanin is present
Lesions to the subthalamic nuclei can give rise to what condition?
What is the main characteristic of this condition?
Give rise to a condition known as Ballismus
This is where there are explosive movement of the limbs
The degradation of what pathway is involved with Parkinson’s disease?
The degradation of the substantia nigra- striatum pathway (a dopaminergic pathway)
What is the limbic system and what three main structures are involved in this system?
The limbic system is involved in the origins of emotional behaviour
The main structures involved in this pathway are:
- Amygdala
- Hypothalamus
- Hippocampus
Label the limbic system…
What lobe is the amygdala, thalamus and hypothalamus in?
The temporal lobe
What is the hypothalamus involved in?
The origin of emotion
What is the amygdala involved in?
The process of fear and fear conditioning
Also involved in the emotional response to face recognition
Name a diseases that can cause lesions of the amygdala?
What happens in this diseases and what are the effects of this?
Urbach-Wiethe disease
Here calcium is deposited in the amygdala
If this disease occurs early in life, then these patients with bilateral amygdala lesions cannot discriminate emotion in facial expressions, but their ability to identify faces remains
Name three processes that the amygdala is involved in?
Reward
Addiction
Negative reinforcement (which is important in addiction)
What is the reticular formation?
A diffuse ascending network of neurons which regulate arousal
Interconnected nuclei throughout the brain stem
Tell me what the Ascending reticular activating system (ARAS) inputs to?
ARAS inputs to hypothalamus, basoforebrain and thalamus. Important for regulation sensory imput to the cortex
Name the main neurotransmitters involved in the brain
- Noradrenaline
- Dopamine
- 5-HT
- Glutamate
- GABA
Draw noradrenaline
draw dopamine
draw 5-HT
draw glutamate
draw GABA
What type of neurotransmitter is noradrenaline?
A catecholamine
Tell me about the axons that noradrenaline travels along, what is it known as?
Noradrenaline travels along long ascenidng axonal tracts. These are known as the medial forebrain bundle.
Name the monoamines
dopamine, noradrenaline and serotonin
dopamine and noradrenaline are also known as catecholamines
What can monoamines influence hormone secretion from?
The pituitary
Where are the neurons present that synthesise noradrenaline?
The Locus Coeruleus (LC)
What pathways originate at the locus coeruleus?
Virtually all the Nadr efferent pathways originate at the LC
Where is the Locus Coeruleus present?
Tell me about the axons that branch off of this nucleus
This nucleus is in the midbrain and part of the reticular formation which has a role in the arousal, sleep/wake cycle
The axons consist of highly branches, largely unmyelinated axons
The axons innervate the limbic system and limbic areas of the cortex and innervate areas controlling the sensory input which has a key involvement in perception and attentional processes
What type of neurotransmitter is dopamine?
Catecholamine
What nucleus secretes dopamine?
Dopamine is synthesised in nerve cell bodies in the ventral tegmental area (VTA) and is released in the nucleus accumbens and the prefrontal cortex
What are the dopamine pathways?
Mesocortical pathway
Mesolimbic pathway
Nigrostriatal pathway
Tuberoinfundibular pathway
What are the dopamine nuclei?
substantia nigra
ventral tegmental area
arcuate nucleus of the hypothalamus
What main processes are each of the dopamine pathways involved in?
Nigrostriatal pathway: motor control
Mesolimbic and Mesocortical pathway: behaviour
What dopamine pathway is the nucleus accumbens important in?
Mesolimbic
What nuclei is important in the 5-HT pathway?
The Raphe nucleii
What does the Raphe nucleus innervate?
The limbic system and cortex
Tell me how neuronal activity changes in the 5-HT pathway in freely moving animals
in freely moving animals, the level of neuronal activity increases immediately prior to and during periods of activity
Where are the raphe nuclei found?
They are found in the medulla and are part of the reticular formation
Tell me about the cholinergic pathways axonal projections
They have long and short axonal projections
Cholinergic neurotransmission is mediated by what neurotransmitter?
Acetylcholine (ACh)
Tell me the link between the cholinergic pathway and the nucleus of meynert?
The nucleus basallis neurons project the cholinergic axons to the cerebral cortex and the septal cholinergic neurons to the hippocampus
Tell me the neurotransmitters involved in the excitatory and inhibitory transmission in the cholinergic pathways
What do they act on?
Glutamate and GABA
Glutamate is a fast excitatory NT that acts on two classes of receptors: Ligand gates ion channels (ionotropic) and G-protein coupled receptors (metabotropic)
GABA is an inhibitory NT and act on gated chloride channels
They are major transmitters in the CNS and have a ubiquitous distribution
Atrophy of what part of the brain is thought to be part of the pathophysiological cascade in progressive alzheimer’s?
Severe atrophy of the basal forebrain cholinergic system especially of the nucleus basalis of Meynert (NBM) and an ensuing reduction of cholinergic innervation of the cortex are considered part of the pathophysiological cascade in progressive Alzheimer’s disease (AD)
Label these structures of the cholinergic pathway
to revise neurotransmitter pathways, consult the Biochemical Basis of Pharmacology, Cooper Bloom and Roth.
to revise functional neuroanatomy. Brain Biochemistry by Philip Strange gives a simple and readable account.
Copies of both these texts are in the library.
What are the methods for studying CNS disorders?
imaging techniques
Indirect ‘markers’ for changes in neurotransmitter function
Post-mortem studies on human brain
Genetic- linkage analysis
Animal models
Look up the work of Nora Volkow and Victor Ramahchandrah
Tell me the different types of imaging techniques
Tell me their resolutions
- CT (computerised tomography)- X-ray
Spatial resolition several mm
- MRI (magnetic resonance imaging)
Resolution less than 1mm
- fMRI (functional magnetic resonance imaging)
- Diffusion tensor imaging
- PET (positron emission tomography)
- SPECT (single photon positron emission tomography)
- EEG (electroencephalography)
- MEG (magnetoencephalography)
What is fMRI?
What idea is it based upon?
This is a development from MRI
It detects changes in activity levels in the brain
This is based on the fact that Oxyhaemoglobin has different magnetic resonance to deoxyhaemoglobin
What is the basis for fMRI?
- Reveals patterns of actiivty in the intact brain
- Visual stimulation
- Activity utilises oxygen
Tell me about diffusion tensor imaging
Mapping pathways and investigating aberrant connectivity
What do PET and SPECT scans show?
Both of these techniques reveal activity in the intact brain
What is the main advantage of the SPECT scan?
Does not require on site cyclotron
Tell me how the PET/ SPECT scans work?
- first unstable positron emission isotopes are created in a cylcotron e.g. O15 (half-life 2 min)
- when these isotopes are injected, they distribute according to the relative activity of the brain regions (these isotopes bind to specific receptors)
alternately, this technique may be used to estimate receptor levels
Name some non-invasive imaging techniques
EEG and MEG
indirect ‘markers’ are used to detect changes in neurotransmission function. State some fluid which these markers can measure the level of metabolites in…
- Cerebrospinal fluid (CSF)
- Plasma
- Urine
- Platelets
How do markers measuring neurotransmitter function bind to platelets?
They bind using monoamine transporters as markers for depression (looking at 5-HT uptake)
Give an example of a binding used when lookin at post-mortem human brains
Radioligand binding
Radioligand binding is an approach that makes use of a radioactively labeled compound, which binds at the target binding site.
What are the disadvantages of the imaging techniques of looking at post-mortem studies on the human brain
- The protein is labile- may degrade
- Patients may have been taking medication
Tell me about genetic- linkage analysis
- restriction-fragment length polymorphisms RFLPs
- DNA is highly polymorphic (one variant every 100 bp) some of these occur at cleavage sites for restriction endonucleases-
- different sized DNA fragments are compared by electrophoresis
How are restriction-fragment length polymorphisms (RFLPs) inherited and what do they require?
- RFLPs are inherited in a Mendelian manner
- requires family ‘pedigree’ of inheritable disease- easiest to study in ‘genetically isolated’ communities
Mendelian inheritance: The manner by which genes and traits are passed from parents to their children. The modes of Mendelian inheritance are autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. Also known as classical or simple genetics.
What do RFLPs determine?
determines whether inheritance of the disease and the RFLP are linked
Whats the pros and cons to genetic linkage analysis with RFLPs?
- this approach worked well for mapping gene mutation that is responsible for Huntington’s chorea
- less successful for other disorders- these may involve multiple genes or mitochondrial DNA
What are animal models used for?
To mimic neurochemical changes that occur in disease
Tell me what the animal models showed with Parkinsons disease
Parkinson’s disease-
- rat 6-hydroxydopamine lesions of the striatum
- primate MPTP lesions of the striatum
What are the pros and cons of using animal models?
Advantages: drug screening therapy
Disadvantages: not an exact ‘phenocopy’ of the disease
Genetic approaches?…
Mouse
Mice over-expressing mutant Alzheimer’s disease (AD)-related proteins exhibit many of the neuropathological and behavioral features of the human disease. Transgenic animals have been created that express mutations in the amyloid precursor protein (APP), presenilin (PS)1, and PS2, and animals expressing more than one of these mutations.
Invertebrate models of human disease
Summary
These two lectures provide intro for the rest of the course-
- You should be familiar with functional divisions of brain
- Neurotransmitters and pathways
- Methodological approaches
- Following lectures will cover;
Autism spectrum disorders
Depression and anxiety disorders
Psychotomimetic drugs
Schizophrenia
Reward and addiction
