Today's 8-Point Health and Science Blog is about our amazing nerves. The fact you are about to learn about these cells is a testament to how incredible they are...It's your nerves that are allowing you...to learn about your nerves!
1. A nerve (or neuron) is a specialized gland cell. Our bodies' endocrine system consists of gland cells that release hormones (signaling molecules like insulin), stored in special storage vesicles, directly into our blood vessels in an 'uncontrolled' manner. If there are ducts (or tubes) into which these gland cells are secreting (whether they be hormones, enzymes, sweat, or even semen), then the gland would by termed an "exocrine" gland.
2. In order to really control the human body in a 'targeted' fashion, wouldn't it make sense to release signaling molecules into a tiny space directly adjacent to its target blood vessel or cell? The answer...Yes! (smile)...This, in fact, is precisely what a neuron does!
3. The characteristic landmarks of a neuron are its amazing information receiver systems called Dendrites, and its unique, electricity-conducting Axon ("arm") that stretches from the cell body of these specialized gland cells. All of the signaling molecules, also stored in specialized storage vesicles by the way, are shuttled down the axon on a 'highway' of microtubules to the synaptic bulb (aka the pre-synaptic terminus). When stimulated to release the contents of their localized vesicles via an electrical (nerve) impulse (or Action Potential), neurons have the amazing ability to 'target' a change in a nearby cell/tissue and only that cell/tissue...The axon facilitates 'targeted control'!
4. The very tiny interstitial space (inter = between; stitium = tissue layers) into which the signaling molecules are released is called a "synapse" or "synaptic cleft" and the released signaling molecules are generally called "neurotransmitters"...why? Because they transmit information from one neuron to another neuron (or other tissue).
5. In this way, the signaling molecules can quickly diffuse across the synapse to cause a change in another nerve, to stimulate a particular muscle to contract (at the unique Neuro-Muscular Junctions, NMJs), or even, directly or indirectly via the blood stream,...to tell a gland to release its hormones/enzymes/sweat/semen, etc.!
6. Surprise, surprise, the 'master controllers' of our bodies are part nerve, part gland! The Hypothalamus of the brain is all nerve and it, yes, 'has the nerve' (sorry) to tell the entire body what to do! Located smack dab behind the eyes (the safest part of the body when you think of it) and below the thalamus (hence HYPOthalamus), this nerve centre 'tastes' our blood and, as necessary, makes remarkable homeostatic changes occur to keep our bodies under control and in physiological balance.
7. I think of the hypothalamus as the 'unsung hero' of the body, quietly, incessantly secreting hormones (yep, specialized gland cells all right...its neurotransmitters are actually hormones!) directly and in a controlled fashion into our blood and toward the pituitary gland to control many vital body functions like water balance (ADH, released when the hypothalamus finds that our blood doesn't taste 'watery' enough) and child birth (oxytocin, the hormone used to induce labor), both sent down the hypothalamic axons to be released from the posterior half of the pituitary gland (the neurohypophysis). The incredible hypothalamus even acts like a thermostat, raising our body temperature to destroy heat-sensitive bugs (aka, a fever!). All of its other myriad of hormones are have an "R" (for Releasing) or " I" (for Inhibiting) in their names that tell other glands, esp, the nearby anterior pituitary gland (the adenohypophysis, erroneously called the "master gland" in my opinion) to either "turn on" or "turn off" the secretion of other hormones involved in even more vital functions like growth (Human Growth Hormone, HGH), salt balance (the Adrenal Cortex's Adolesterone is released via the Adreno-Cortico Trophic Hormone, ACTH, when the hypothalamus thinks that our blood doesn't taste 'salty' enough), glucose balance (Insulin is released from the pancreas under the behest of the pituitary when the hypothalamus thinks that our blood tastes too 'sweet'), and many, many more.
8. Let's respect the humble nerve cell. Not only is it the source of balance in our bodies, but it is also the basis of memories, thoughts, emotions, movement, sensations of vision, touch, taste, hearing, smell,...too much to list here. Let's "exercise" our brains by subjecting them to various interesting tasks everyday. Let's continually learn, putting aside the digital calculator when we can, and expand our daily experiences. And let's remember that our blood-brain barrier (a subject for another blog perhaps) makes it difficult for fats and proteins to cross over from the blood, except, surprise, surprise at the level of the hypothalamus which needs direct access to the blood. Hence, our brains primarily use glucose, a molecule small enough to cross the blood-brain barrier, for energy!
So, my friends, eat well and *sniiifff* breath well because: Glucose + Oxygen = Carbon Dioxide ("clean" waste) + Water ("clean" waste) + ATP, Adenosine Tri-Phosphate, the 'energy currency' molecule of our bodies and one of the reasons why, after water, we are mostly Phosphate by weight! And did you notice that our bodies normally and naturally use "clean burning fuels"? It's the bacteria that make the methane, hydrogen sulfide, etc....But again, perhaps the subject of another blog. (smile)
Be Good, Be Healthy, Be Happy,
Dr. Sheldon
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An Introduction to Nervous Systems
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The Pituitary (Pituitary (Melmed))
Diagnosis and Management of Pituitary Disorders (Contemporary Endocrinology)
Pituitary Gland (Carolina Biology Readers; 118)
Neurotransmitters and Neuromodulators: Handbook of Receptors and Biological Effects
Balance Your Brain, Balance Your Life: 28 Days to Feeling Better Than You Ever Have
The War of the Soups and the Sparks: The Discovery of Neurotransmitters and the Dispute Over How Nerves Communicate
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