Tuesday, May 29, 2007

The Human Nervous System - PART THREE

The Autonomic Nervous System Divisions

The autonomic nervous system (ANS) houses two major divisions, the parasympathetic and the sympathetic division. At most times, the two divisions are antagonists to each other; if the sympathetic division causes excitation, the parasympathetic division will counter-act with an inhibitory effect. This is not always the situation, however. Because the two divisions may work independently, with some structures innervated by one division, and the two divisions may work synergistically, each contributing to one stage of a complex process. Generally speaking, the parasympathetic division is active in rest states, and the sympathetic division “kicks in” during times of exertion, stress, or emergency.

When you are doing a heavy weight lifting session at the gym your sympathetic division is full effect. It is sending signals to your cardiovascular and respiration center of the pons, leading to increased blood pressure, heart rate, breathing rate and depth of respiration, so blood and oxygen delivered to muscles. All of this happens unconsciously; it is and is an involuntary action. During this time also, your digestive system is somewhat inhibited so all of ones energy can be focused at the task at hand. One will also have an increased mental alertness and a state of euphoria. Also, there is a general elevation of muscle tone, so a person looks tense. Finally, the mobilization of energy stores, through an increased breakdown of glycogen in muscle and liver cells and the release of lipids from adipose tissues.

After the workout or cardio session the activity of the sympathetic nervous system decreases and the parasympathetic division comes into play. When you leave the gym and step out into the bright sun (hopefully) the parasympathetic nervous system will cause a constriction of the pupils to inhibit the amount of light entering the eyes. And while on your way back home or wherever, there is secretion of digestive glands, including of hormones that promote nutrient absorption, so the hard worked muscles can recover properly. There is also a constriction of respiratory passageways and reduction in heart rate and force of contraction. All of this aids in you becoming more relaxed.

Like stated, the parasympathetic nervous system focuses on relaxation, food processing and energy absorption. It ahs been called the anabolic system because stimulation leads to a general increase in the nutrient content of th blood.

Kurt Kuhn - www.FUSIONBodybuilding.com

Monday, May 14, 2007

The Human Nervous System - PART TWO

The Central Nervous System - The Spinal Cord

The spinal cord attaches to the brainstem providing a critical pathway for the flow of information from the skin, joints and muscles to the brain, and vice versa.

In cross sections of the spinal cord there is a H-shaped center of gray matter. The ventral (anterior) and dorsal (posterior) horns describes the sections of this core. The spinal cord core contains primarily three types of neurons: motor neurons, sensory neurons, and interneurons. The motor neurons (efferent) run through the ventral horn to supply skeletal muscle. Sensory (afferent) nerve fibers enter the spinal cord from the periphery by way of the dorsal horn. The white matter, containing the ascending and descending nerve tracts, surround the gray matter within the cord.

As previously mentioned, information going towards the brain is sensory information, such as touch, taste and also pain. So if you are working out and pull a muscle or drop a 45 lb plate on your small toe the nerves will travel up to the brain via afferent nerve fibers of the spinal and the information will be integrated there. Here the response will be traveling via afferent nerve fibers to produce a motor response.

Ascending Nerve Tracts

Ascending nerve tracts in the spinal cord send sensory information coming from peripheral receptors to the brain for processing. There are three neurons that typically make up sensory pathway.

1) The dorsal root ganglion contains the cell body of the first neuron whose axon relays information into the spinal cord.
2) The cell body of the second neuron lies within the spinal cord itself; its axon passes up the spinal cord to the thalamus.
3) The thalamus contains the third neuron's cell body. The axon of the third neuron passes up to the central command center of the cerebral cortex

Descending Nerve Tracts

Axons from the brain move downward through the spinal cord along two major pathways. The lateral or pyramidal tract activates the skeletal muscle (the muscles that you primarily use when working out). The second pathway named ventromedial or extrapyramidal tract, controls posture and muscle tone via the brainstem.

Kurt Kuhn - www.FUSIONBodybuilding.com

Tuesday, May 08, 2007

The Human Nervous System - PART ONE

Divisions of the Nervous System

The human nervous system has two major divisions:

1) The Central Nervous System (CNS) which is made up of the brain and spinal cord.

2) The Peripheral Nervous System (PNS) division that contains nerves that transmit information to and from the CNS.

From there the PNS is divided into the autonomic nervous system (ANS) which controls involuntary information and it conducts impulses from the CNS to cardiac muscle, smooth muscles (ie. digestive system), and glands. The ANS then gets divided into the sympathetic and parasympathetic nervous system which will be discussed later.

The other partition of the PNS is the somatic nervous system which conducts impulses from the CNS to skeletal muscle.

Both of these divisions play an important role to bodybuilders. It allows us to lift heavy ass weights and digest much needed food.

Breakdown of the Nervous System

The Central Nervous System - The Brain

As previously mentioned the CNS is made up of the brain and spinal cord. The CNS is responsible for integrating, processing, and co-ordination sensory input and motor output. It also plays a role of higher functions, such as intelligence, memory, learning and emotion.

The brain is divided into numerous regions which include the brainstem, cerebellum, diencephalon, telencephalon and the limbic system.

The Brainstem

The brainstem is made up of the medulla oblongata (medulla for short), pons and midbrain. The medulla oblongata is important for relaying sensory information to the thalamus and to other brainstem centers. Also, it contains major centers concerned with the regulation of autonomic function, such as heart rate, blood pressure and the digestive activity. Which all play an important role in the world of gym, the medulla can increase our heart rate so much needed oxygen gets delivered to the muscle and adjusting of blood pressure so we don't faint.

The pons relays sensory information to the cerebellum and thalamus. Also, it is contains subconscious somatic and autonomic motor center. Any motor movements that we don't think about will be sent here.


The cerebellum functions by complex feedback circuits that monitors and coordinates other areas of the brain and spinal cord that are involved in motor control.. The cerebellum receives motor output signals from the central command in the cortex. This cerebellum, also obtains sensory information from peripheral receptors in muscles, tendons, joins and skin and from visual, auditory, and vestibular end organs. The cerebellum serves as the major comparing, evaluating, and integrating center for postural adjustments, locomotion, maintenance of equilibrium, perceptions of speed of body movement and other diverse reflex functions related to movement. Movements that are first learned by trail and error, like riding a bicycle or proper form of deadlifts or squats, remain coded as coordinated patterns in the cerebellar memory banks. Essentially, this motor control center ?fine tunes? all forms of muscular activity


The diencephalon is made up of the thalamus and hypothalamus. The thalamus provides the switching and relay centers for both sensory and motor pathways. Ascending sensory information from the spinal cord and cranial nerves (other than olfactory nerves) is processed in the thalamus before the information is relayed to the cerebrum or brain stem. The thalamus also plays an important role in regulating a sleep and wakefulness states and also has a role in controlling arousal, the level of awareness and activity.

The hypothalamus which lies inferior to the thalamus in the cerebrum, controls metabolic and body temperature. It also influences activity of the ANS; it receives regulatory input from the thalamus and responds to the effects of diverse hormones.


The telencephalon contains the two hemispheres of the cerebral cortex which makes up approximately 40% of the total brain weight. It is divided into four lobes; front, temporal; parietal and occipital. Neurons in the cortex provide specialized sensory motor functions. Deep to each cerebral hemisphere and in close association with the thalamus lie the basal ganglia, which play an important role in control of motor movements.


Kurt Kuhn - www.FUSIONBodybuilding.com

Thursday, May 03, 2007

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