Neurophysiology, Memory & Clinical Applications – Comprehensive Lecture Notes

Autonomic Nervous System (ANS)

  • Two branches constantly balance each other
    • Sympathetic ("fight / flight / freeze / fawn")
    • Primary transmitter: norepinephrine (NE)
    • Functions: focus, concentration, mobilising energy, motivation, immediate survival actions
    • Mnemonic shared: “NE = Focus & Fight/Flight/Freeze/Fawn”
    • Parasympathetic ("rest & digest / repair / fertility")
    • Primary transmitter: acetylcholine (ACh)
    • Functions: rest, tissue repair, digestion, sexual/reproductive processes
  • Contrast: without sympathetic tone we would be “sloths”; without parasympathetic tone we would never recover

Hypothalamus–Pituitary Axis Recap

  • Matching exercise reviewed – remember the lower-case n vs. upper-case H in abbreviations
    • \text{GnRH} \rightarrow FSH \text{ & } LH (gonads)
    • GHRH→Growth Hormone (GH)\text{GHRH} \rightarrow \text{Growth Hormone (GH)}
    • CRH→ACTH\text{CRH} \rightarrow \text{ACTH} (adrenals)
    • TRH→TSH\text{TRH} \rightarrow \text{TSH} (thyroid)
  • Target tissue of hypothalamic hormones = anterior pituitary ("first domino")

Cell Membrane Potential & The Na+/K+Na^+/K^+ Pump

  • Visual mnemonic: "eating depo-Lay’s (sodium) potato chips makes the cell more positive"
  • Baseline conditions
    • Outside: higher Na+Na^+, more positive
    • Inside: higher K+K^+, more negative (≈ −70 mV-70\,\text{mV} resting potential)
  • Pump cycles
    • 3 Na+3\,Na^+ pumped out, 2 K+2\,K^+ pumped in per ATP ⇒\Rightarrow maintains polarity & readiness
    • Depolarisation: Na+Na^+ rushes in ⇒\Rightarrow cell becomes less negative
    • Re-polarisation: K+K^+ flows out restoring negativity
  • Purpose: keeps neuron "armed" for the next impulse; cannot wait to charge up during emergencies

Local vs. Action Potentials

  • Local potentials
    • Start on dendrites, travel toward trigger zone
    • Variable: magnitude depends on ion flow, can fade with distance/time
    • Modulated by neurotransmitters
    • Excitatory (e.g.
      nicotine, cocaine, meth → glutamate, dopamine, serotonin) → speeds activity
    • Inhibitory (e.g.
      alcohol, opiates, fatigue → GABA) → slows activity
  • Action potentials (AP)
    • Initiate at trigger zone, travel one-way to synaptic knob
    • All-or-nothing (analogous to each muscle fibre)
    • Speed boosted by myelination (fat–protein sheath)

Muscle-Fibre vs. Neural Activation Analogy

  • Muscle fibre motor unit = on / off (paper-clip vs. elephant example with light-switch bank)
  • Neural signalling
    • AP = on / off
    • Local potential = graded ("dimmer") until threshold reached

Reflex Arc Refresher

  • Components: Receptor → Afferent neuron → Integrating centre (spinal cord) → Efferent neuron → Effector
    • Somatic reflex = skeletal muscle
    • Autonomic reflex = smooth/cardiac muscle & glands
  • Protective sequence allows withdrawal before conscious identification (e.g.
    tack, Lego, hot stove)

Memory & Neuroplasticity

  • Stages
    • Immediate (milliseconds)
    • Short-term (seconds–hours) – “squirrel!” distraction point
    • Long-term (requires consolidation during sleep & repetition)
  • Brain structures: amygdala, hippocampi, mammillary bodies, thalamus guide storage & emotional tagging
  • Accuracy caveat: memories are reconstructed, often distorted, trauma heavily influences retrieval/blocking
  • Neuroplasticity
    • Brain’s intrinsic ability to form new pathways – “detours” around damage (e.g.
      post-stroke rewiring)
    • Underlies personal change (“growth mindset”): behaviour, habits, emotional patterns are not fixed

Nutrition & Lifestyle for Nervous-System Health

  • Electrolytes
    • Sodium: recommended ≈1500 mg\approx 1500\,\text{mg} vs.
      typical ≈3500 mg\approx 3500\,\text{mg} (excess → BP & fluid issues)
    • Potassium: plentiful in fruits/veg; supplementation only under medical supervision (risk of cardiac arrest)
  • Fats
    • Required for myelination & for breastfeeding individuals’ recovery
    • Emphasis on whole-food balance of saturated & unsaturated fats (avocado ≠ Oreo fat)
  • Magnesium
    • Common deficiency; lecturer uses Mg  L-threonateMg\;L\text{-}threonate nightly (brain-penetrant)
    • Other forms: citrate (useful if constipated), malate, etc.
  • B-vitamins – co-factors for ATP production (cellular energy)
  • Probiotics / healthy flora – gut–brain axis modulates neurotransmitter synthesis
  • Moderation principle: “everything in moderation, even moderation”; perfectionism → burnout/depression

Diagnostic Tools & Emerging Monitoring

  • Lumbar puncture (spinal tap) – analyse cerebrospinal fluid (CSF)
  • Nerve-conduction studies – assess peripheral signalling speed
  • Functional MRI – mapping real-time brain activity; currently expensive but growing
  • Heart-Rate Variability (HRV)
    • Wearables (e.g.
      Oura Ring) offer early insight into autonomic balance & cardiovascular risk

Cerebro- & Neuro-Pathologies (quick chart guide)

  • Stroke (CVA)
    • Types: ischaemic (blockage) vs.
      haemorrhagic (bleed)
    • FAST(+):
    • Face droop
    • Arm weakness / loss of grip or balance
    • Speech slurred / saliva pooling
    • Time to call 911
    • (Some add Eyes / Balance or BE-FAST)
    • Incidence rising <40 yrs; early action improves prognosis dramatically
  • Brain tumours – especially gliomas (from neuroglia)
  • Alzheimer’s disease – progressive memory loss, onset mid-60s+, more common in women
  • Parkinson’s disease (PD)
    • ↓\downarrow dopamine in substantia nigra → overactive basal ganglia
    • Pill-rolling tremor, onset ~55 yrs
  • Multiple Sclerosis (MS)
    • Auto-immune demyelination in CNS, onset 20–40 yrs, relapsing–remitting patterns
  • Additional disorders listed in textbook charts (Ch. 5 & 6) – focus on definition & hallmark signs

Stroke Case Study (Instructor’s Father)

  • Pre-stroke TIAs mislabelled “dehydration” → missed opportunity for prevention
  • Full ischaemic stroke; initial hospital delay in imaging & anticoagulation
  • Complete loss of vision, speech, gait; regained via intensive therapy
    • Felt “brain–leg tingling” as new pathways formed → live demonstration of neuroplasticity
  • Key practical lessons
    • Know FAST; trust gut; call EMS despite patient protest (paramedic scene assessment often free)
    • Encourage paced breathing during event – may preserve oxygenation & calm
    • Support growth mindset & tenacity during rehab but avoid unsafe solo attempts

Integrative Take-Aways

  • ANS balance = simultaneous sympathetic mobilisation & parasympathetic restoration; neurotransmitters NE vs.
    ACh
  • Neuronal readiness relies on Na+/K+Na^+/K^+ gradients (pump = 3:23:2 ratio, ATP-dependent)
  • Action potentials obey the all-or-nothing law; local potentials are graded
  • Memory & behaviour are malleable; neuroplasticity refutes “fixed” identities
  • Nutrition, sleep, stress-management & gut health are foundational interventions before pharmaceuticals
  • Early diagnostic monitoring (HRV, nerve studies, FMRI) can shift healthcare from reactive → preventive
  • Clinical vigilance (FAST) & rapid response save lives and limit disability in cerebrovascular accidents