Recap of brain structures and neurotransmitters

neuropsychiatric disorders 

• Biological basis is poorly understood

• Not disorders of a specific brain region à difficult to treat

• Hard to diagnose as the main diagnostic method is through self reporting

• Theories suggesting rather than looking for some specific disorder its more about looking for a continuum of neuropsychiatric disturbance 

ventricles

• 4 Ventricles in the middle of the brain: 2 lateral, a 3^rd and a 4^th ventricle

• Filled with CSF – can be useful to sample as they contain neurotransmitters

•  Ventricles will expand to fill the space when parts of the brain decay/atrophy

cortex 

• Temporal lobes become very active in schizophrenia patients who have hallucinations

• Prefrontal cortex not essential to live Eg: Phinneas Gage

•  Big feedback loop for spatial information, planning and execution of movement

limbic system 

• Number of different nuclei: hippocampus, amygdala and hypothalmus

• Regulation of emotion and behaviour

•  Hippocampus function changes along the longitudinal axis

  • Ventral – more interlinked with amygdala and more associated with anxiety

  • Dorsal – more interlinked with the cortex more important for spatial information

• Amygdala sits at the end of the hippocampus

• Hypothalamus linked with the pituitary

amygdala

• Involved in fear and emotional response to face recognition a can induce sham rage

• Urbach Wiethe disease where calcium deposited in the amygdala and patients with bilateral amygdala lesions cant discriminate emotions in facial expressions

hemispheres 

• Connected by the corpus callosum, made up of many neurons

• The brain functions as a single unit in most people, evidence of lateralisation

• Not essential – can be removed in epileptic patients who have whole brain epilepsy

• However, does have side effects E.g: if a water bottle is perceived on the right side, you could see a water bottle but wouldn’t be able to say it’s a water bottle

• In some patients with reduced hemisphere asymmetry, there's an increased risk for schizophrenia (as the left brain is responsible for linguistic ability, whilst the right side of the brain Is responsible for perception)

• Potentially reduced asymmetry in patients with neuropsychiatric disorders

thalamus

• Sensory information ascending the spinal chord synapse in the thalamus, new neurons ascend up to the cortex

• Reticular activating system is ascending information which is non specific – more a general state of arousal

  • Also has very diffuse innervation

  • Main sensory afferents have projections which form the reticular activating system

• Has a circuit loop which acts as a relay station for sensory info  

  • Provides all parts of the corte with information and in turn takes input from the cortex  

  • Ascending info sent to the thalamus —> cortex —> descending info to the striatum —> thalamus

basal ganglia 

• Middle of the brain

• Causes disorders of movement

• Extrapyramidal motor control causes involuntary movement, control of initiation of movement

• Pyramidal motor control is responsible for voluntary movement

• The caudate and the putamen make up the striatum —> dopaminergic neurons dark in colour so stripy

• Challenges of antipsychotics is not inducing Parkinson’s

catecholamines - Noradrenaline 

• adrenaline

• noradrenaline 

• dopamine 

*Catechol group is a benzene ring with 2 hydroxyl groups on each side

NORADRENALINE 

• Long tracts, small, highly branched, unmyelinated

• Diffuse innervation pattern

• Nadr neurons originate from a single nucleus: locus coerelius (part of the reticular activating system – role in general arousal)

• Have lots of neuromelanin – sometimes appear blue

• Ascending Nadr pass through the medial forebrain bundle, affect hormone secretion

• Innervate limbic regions

• Very specific subgroups of neurons in subregions of LC, might not be as long and barnched as we think they are

catecholamines - Dopamine 

• adrenaline

• noradrenaline 

• dopamine 

DOPAMINE 

• 3 regions in the brain that have dopaminergic neurons, can control behaviour, motor control and hormone secretion

  • Substantia Nigra (part of the basal ganglia): cell bodies in SN and project to the striatum

  • Ventral Tegmetal area: form mesolimbic pathway à innervates nucleus accumbens, involved in reward. Also mesocortical pathway where neurons from VTA innervate the cortex

  • Arcruate nucleus send neurons down to the pituitary

5HT

5HT

• Monoamine – not chatecholamine

• Synthesised in the rafe nuclei – small all located in the region of the midbrain

• Send afferents all over the brain so can affect limbic and cortical areas

• Activity of neuros goes up when animals are aroused as the Rafe nuclei located in the path of the reticular activating system

• Level of activity of nuclei increases immediately prior to and during periods of activity.

Acetylcholine

• 2 main types of neurons

  • One type has long projections – originates from the nucleus Basalis of myenert —> innervate the cortex, linked to cognitive function

  • One has short projections and are interneurons – found round the basal ganglia, control and modulate levels of local information

GABA/Glutamate

• Ubiquitous

• Can't modulate them

• Control information within the brain a drive most of the function, other neurotransmitters that we’ve talked about more modulating the function.