The Nervous System

The nervous system is essentially a biological information highway, and is responsible for controlling all the biological processes and movement in the body, and can also receive information and interpret it via electrical signals which are used in this nervous system It consists of the Central Nervous System (CNS), essentially the processing area and the Peripheral Nervous System which detects and sends electrical impulses that are used in the nervous system

The Central Nervous System The Central Nervous System is effectively the center of the nervous system, the part of it that processes the information received from the peripheral nervous system. The CNS consists of the brain and spinal cord. It is responsible for receiving and interpreting signals from the peripheral nervous system and also sends out signals to it, either consciously or unconsciously. This information highway called the nervous system consists of many nerve cells, also known as neurons

Nerve Cell

The Nerve Cell Each neuron consists of a nucleus situated in the cell body, where outgrowths called processes originate from. The main one of these processes is the axon, which is responsible for carrying outgoing messages from the cell. This axon can originate from the CNS and extend all the way to the body's extremities, effectively providing a highway for messages to go to and from the CNS to these body extremities. Dendrites are smaller secondary processes that grow from the cell body and axon. On the end of these dendrites lie the axon terminals, which 'plug' into a cell where the electrical signal from a nerve cell to the target cell can be made. This 'plug' (the axon terminal) connects into a receptor on the target cell and can transmit information between cells

The Way Nerve Cells Communicate The "All-Or-None-Law" applies to nerve cell communication as they use an on / off signal (like an digital signal) so that the message can remain clear and effective from its travel from the CNS to the target cell or vice versa. This is a factor because just like electricity signals, the signal fades out and must be boosted along its journey. But if the message is either 1 or 0 (i.e.) on or off the messages are absolute.

Brain Divisions There are three main components of the brain, namely the brainstem, cerebellum and the forebrain. The Brainstem - The brainstem is the connection between the rest of the brain and the rest of the central nervous system. It is primarily concerned with life support and basic functions such as movement The Cerebellum - Consisting of two hemispheres, the cerebellum is primarily concerned with movement and works in partnership with the brainstem area of the brain and focuses on the well being and functionality of muscles. The structure can be found below the occipital lobe and adjacent to the brainstem The Forebrain - The forebrain lies above the brainstem and cerebellum and is the most advanced in evolutionary terms

The Forebrain The forebrain has many activities that it is responsible for and is divided into many component parts. The Hypothalamus - A section of the brain found next to the thalamus that is involved in many regulatory functions such as osmoregulation and thermoregulation. The hypothalamus has a degree of control over the pituitary gland, another part of the brain situated next to it, and also controls sleeping patterns, eating and drinking and speech. The hypothalamus is also responsible for the secretion of ADH (Anti-Diuretic Hormone) via its neurosecretory cells The Cerebrum - The cerebrum is the largest part of the human brain, and the part responsible for intelligence and creativity, and also involved in memory. The 'grey matter' of the cerebrum is the cerebral cortex, the center that receives information from the thalamus and all the other lower centers in the brain.

The Cerebrum The Cerebral Cortex - Part of the cerebrum, this part of the brain deals with almost all of the higher functions of an intelligent being. It is this part of brain that deals with the masses of information incoming from the periphery nervous system, furiously instructing the brain of what is going on inside its body and the external environment. It is this part that translates our nervous impulses into understandable quantifiable feelings and thoughts. So important is the cerebral cortex that it is sub-divided into 4 parts, explained below Frontal Lobe - Found at the front of the head, near the temples and forehead, the frontal lobe is essential to many of the advanced functions of an evolved brain. It deals with voluntary muscle movements and deals with more intricate matters such as thought and speech Parietal Lobe - Situated behind the frontal lobe, this section deals with spatial awareness in the external environment and acts as a receptor area to deal with signals associated with tough. Temporal Lobe - The temporal lobes are situated in parallel with the ears, they serve the ears by interpreting audio signals received from the auditory canal Occipital Lobe - This is the smallest of the four lobe components of the cerebrum, and is responsible in interpreting nerve signals from the eye at the back of the brain

Cerebral Cortex

Peripheral Nervous System The PNS consists of the nerves and is divided into somatic and autonomic divisions. This means: somatic nervous system ALWAYS receives the stimulus from outside of the organism and ALWAYS controls skeletal muscles; autonomic nervous system ALWAYS receives stimuli from inside of the organism, and its efferents ALWAYS end on smooth muscle, cardiac muscle or glands.

Peripheral Nervous System Somatic nervous system-carries messages between the CNS and the body; consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves Autonomic nervous system- contains the sympathetic (fight or flight response) and parasympathetic (counteracts these actions) nervous systems, which work together to control involuntary body functions.