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Brain & Nervous System - Coggle Diagram
Brain & Nervous System
Nervous system
CNS: brain & spinal cord
Spinal cord
- Mostly white matter (myelinated axons)
- Dorsal/back roots = sensory (has ganglion - cluster of cell bodies)
- Ventral/belly roots = muscles
PNS: nerves outside CNS
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Autonomic
- Heart, intestines, other organs; involuntary muscles
Sympathetic: expends energy = fight or flight
- Increased breathing, heart rate
- Decreased digestion
- Central (thoracic & lumbar), chain of ganglia, ganglia linked
- Releases norepinephrine
Parasympathetic: conserves energy = rest & digest
- Increased digestion, sexual arousal
- Decreased heart rate
- Craniosacral, no chain, ganglia not linked (independent)
- Releases acetylcholine
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Brain
Binding problem: how different brain areas produce perception of single object at same time (how senses combined)
Modularisation implications
- Reflects evolutionary past
(built like a renovation)
- Redundancy
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Genes & Brain Dev
Genes & behaviour
- Directly alter chemicals, indirectly alter body/how people react to us
- But behaviour is combination of genes + environment
Embryonic development (macro)
- Small ball of cells
- Homeobox genes give it front/back/L/R
- -> Blastulation: hollow sphere of cells
- -> Gastrulation: outer/middle/inner layers
- -> Embryo (2w) -> neural plate & ectoderm (with mesoderm & endoderm)
- -> Invagination: neural plate -> neural groove, with neural fold either side
- -> neural groove closes -> neural tube (-> CNS) & neural crest (-> PNS)
- -> Distinct hind/mid/forebrain (7w)
- -> Growth from 350g to 1kg at 1y (individual neurons bigger, not more neurons)
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Genes & nervous system
- Genes influence organisation & development of cells
- Chemical instructions to make protein -> proteins required for neurotransmitters
- Part of chromosome (23 pairs) which is composed of DNA - sequence of DNA
- DNA = template for RNA (in nucleus)
- RNA = template for proteins (copies DNA, then leaves nucleus to make protein)
Disorders
Depression
Diagnoses: many & diverse
- Sad, worthless, sleep/weight change, cognitive (motivation, attention, memory, concentration)
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Neurological
Brain correlates
- Less activity in L PFC
- More activity in R PRC
Neurotransmitters
- Low monoamine transmitters - serotonin, norepinephrine, dopmaine
Therapies
Drugs
- Tricyclics: block reuptake of serotonin & norepinephrine/dopamine (blocks transporter that reabsorbs)
- SSRIs/bicyclics: block reuptake of serotonin - less side effects
- MAOIs: block MAO enzyme that breaks down serotonin & norepinephrine - side effects
ECT: electrically induced seizure
- Effective if severe, suicidal
- Sedative & muscle relaxant, then current to induce convlusion
Bipolar
Diagnoses: alternate between depression & mania
- Vs unipolar: alternate between normal & depression
- Mania: restless, grandiosity, rambling, distractible
- Bipolar I: full-fledged manic episodes
- Bipolar II: mild/hypomanic episodes - milder anxiety/agitation
Genetic: linked to many genes (predisposed)
- Larger amygdala
- Dysregulation hypothesis: low MAO = depression, high = mania from physiological instability
Treatment: lithium salts
- Moderates amount of epinephrine
- Works in 80% cases
- Dose important
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Schizophrenia
Diagnoses: deterioriation for 6m+
- Differential diagnosis: not other condition
- Delusions: beliefs; +ve
- Hallucinations: sensory; +ve
- Disorganised speech: rambling/incoherent; +ve
- Disorganised behaviour: bizarre, inappropriate; +ve
- Weak emotional expression, speech, socialisation: flat, no pleasure; -ve
Genetic: predispose
- More likely if biologically related to SZ
Drugs
- Antipsychotics/neuroleptics: reduce dopa; +ve symptoms; side effects - tardive dyskinesia
- Atypical/2nd-gen: increase serotonin, selectively reduce dopa; +ve and -ve; less side effects
- No cure, side effects, mostly +ve symptoms, doesn't help all
Hypotheses
Neurodevelopmental
- Pre/neonatal - brain abnormality/vulnerability
** Smaller frontal/temporal cortex
** Smaller hippocampus
** Larger ventricles
- Late diagnosis: DLPRC develops slowly
Dopamine
- Excess dopamine -> +ve symptoms
** e.g. drugs block dopa -> reduce +ve symptoms
** e.g. drugs increase dopa -> +ve symptoms
** More dopa receptors (use more)
- Also serotonin low -> less I dopa -> dopa higher
Glutamate
- Deficient glutamate - glutamate & dopamine inhibit each other
- e,g. PCP blocks glutamate receptors -> +ve & -ve SZ symptoms
Anxiety
Neurological
- GAD: low GABA
- Panic: low GABA + overly sensitive respiratory control centres
- PTSD: high dopa, brain stem & amygdala, smaller hippocampus
Drugs
- GAD - benzodiazepine: bind to GABA receptors -> increase GABA activity
- Panic - bi/tricyclics: -> increase serotonin -> I respiratory control centres
Diagnoses
- Generalised: constant, less intense
- Panic disorder: brief, intense
- PTSD: traumatic event -> flashbacks, avoidance, heightened reactions