Graphic

Physiology

Receptor cells – micro environment

Significant receptor cells include;

  • photoreceptors (intrinsically photoreceptive retinal ganglion cell, rods, cones) – light
  • thermoreceptors – heat (internal/external)
  • hydroreceptors – water (internal/external)
  • chemoreceptors – gases and chemicals (internal/external)
  • baroreceptors – pressure (internal/external)
  • osmoreceptors – osmotic pressure (internal)

Hypothalamus

All the above receptor cells innervate the hypothalamus and associated areas as part of the autonomic system; most are G protein-coupled receptors and involve the GPCR pathways – ADRA, ADRB (adrenergic alpha/beta receptors)

  • light – retina to suprachiasmatic nucleus (SCN) part of the hypothalamus via the retinohypothalamic tract
  • heat - cornea to hypothalamus via retinohypothalamic tract, temperature regulation, involves evaporation of lacrimal liquid
  • heat – skin, sweat glands/evaporation, blood thermodynamics via somatosensory system
  • water – cornea/retina to SCN via retinohypothalamic tract, water vapour absorbed by bronchioles in breathing process
  • gases/chemicals – olfactory, gustatory via amygdale of the hypothalamus skin possibly via transient receptor potential channels
  • pressure – internal blood pressure affected by external air pressure on cell walls; baroreceptors situated in many parts of arterial system via somatosensory system, target thalamus
  • osmotic pressure – flow of blood affected by thickness and regulated by vasopressin

Autonomic system

All our vital organs, heart, lungs, digestive system, blood and muscles innervate the hypothalamus. Parasympathetic, sympathetic and enteric systems are all automatic in response to external/internal stimuli balanced by homeostatic mechanism.

Positive/negative feedback

In response to micro environmental external elements of air, heat, light and water the hypothalamus signals all the vital organs. The vital organs respond by signalling the hypothalamus their need for essential nutrients and water to maintain homeostasis.

Essential nutrients

19 elements, 2 fatty acids, 20 amino acids, 13 nucleic acids and carbohydrates Protein hormones of ghrelin and leptin, sugar and fatty acid hormones of insulin and glucagon, water capacity hormones of vasopressin and aldosterone all have a commonality. Ghrelin doesn’t contain tryptophan leptin does, insulin doesn’t contain tryptophan glucagon does, vasopressin doesn’t contain tryptophan aldosterone does. Carbohydrates are balanced by serotonin and melatonin.

Blood-brain barrier (BBB)

There is a distinct dividing line between body and brain, the blood-brain barrier. We consider the brain to be areas containing cerebrospinal fluid; cerebral cortex, cerebellum, central nervous system including the brain stem, 3rd, 4th and lateral ventricles. All other areas can be considered body. The hypothalamus and associated areas are on the body side of the BBB.

Human ability for survival of life occurs on the body side of the BBB and is therefore considered unconscious.