#11 Central Nervous System

Some ability to understand speech, but an inability to produce intelligible words.

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<Central Nervous Sytem Structure & Function>

The central nervous system, consisting of your amazing brain and spinal cord, and the peripheral nervous system, made up of the nerves coming out of that central nervous system.

The central nervous system's main game is integrating the sensory information that the peripheral system collects from all over the body, and responding to it by coordinating both conscious and unconscious activity.

All these sensations, thoughts, and directions process through this two-part system.

It's the brain, of course, that sorts out all that sensory information and gives orders.

It also carries out your most complex functions, like thinking, and feeling, and remembering.

Your spinal cord conducts two-way signal between your brain and the rest of your body, while also governing basic muscle reflexes and patterns that don't need your brain's blessing to work - this is how a chicken can still run around even if the poor thing has been decapitated.

This fulid actually allows your brain to float somewhat in your skull, reducing its weight and letting its slosh around while you and your head are free to move.

Your brain is divided into specialized regions that may, or may not, interact with each other to produce a given action.

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<Brain Development: Neural Tube>

Inside a developing embryo, the central nervous system starts off a humble little neural tube.

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<Brain Development: 3 Primary Vesicles>

We call these chambers the prosencephalon, the mesencephalon, and the rhombencephalon - or forebrain, midbrain, and hindbrain.

These main three chambers start morphing into five secondary sesicles that essentially form the roots of what will become your grown-up brain structures.

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<Brain Development: 5 Seceondary Vesicles>

The prosencephalon divides into two sections - the telencephalon and the diencephalon.

The rhombencephalon forms into another pair, called the metencephalon and the myelencephalon.

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<Brain Development: Major Adult Brain Regions>

The real action starts as these five secondary vesicles start developing into the major adult brain regions that you might be more familiar with - the brainstem, the cerebellum, the diencephalon, also known as the interbrain, and finally the cerebral hemispheres.

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<Brain Development: Cerebellum & Brain Stem>

The least dramtic changes occur in the three most caudal or lower sections: the mesencephalon, the metencephalon, and the myelencephalon.

They go on to form the cerebellum, which mostly helps coordinate muscular activity, and the brainstem, which plays a vital role in relaying information between the body and the higher regions of the brain.

The midbrain also passes that data to regions like the cerebral cortex, which do the actual conscious thinking about the stimuli, like "What is that hing whizzing across the sky?"

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<Brain Development: Reptilian Brain>

This is where you find the thalamus, hypothalamus, epithalamus, and the mammillary bodies, which regulate things like homeostasis, alertness, and reproductive activity.

This area is sometimes called the "reptilian brain" because we share it with some of our less philosophical animal brethren like lizards and fish.

Brain - eat, drink, sleep, mate, stay safe.

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<Brain Development: Cerebral Hemispheres>

During your brain's growth, the telencephalon undergoes the biggest changes of all, as it develops into the most binary part of your brain - the two classic, walnut-looking hemispheres we collectively call the cerebrum, that cover the rest of your brain like a mushroom cap on its stalk.

It's made up of the wrinkled, outer layer of "gray matter" called the cerebral cortex, and the inner squishy layer of "white matter" beneath it.

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<The Brain's Lobes>

A big fissure separates the left and right hemispheres, the two halves communicate, through a series of myelinated axon fibers called the corpus callosum.

And each hemisphere has other, smaller fissures that divide it into lobes - each with a differen set of major functions.

The frontal lobe, for example, governs muscle control and cognitive functions like planning for the future, concentration, and preventing socially unacceptable behaviors.

The temporal lobe helps sort out auditory information, including language.

We could do a whole course on the finger-grained functions and consequences of malfunction in every bit of brain in your gourd, but, well, we can't do that today.