Understand the language – understand the process

What is it…. The nervous system is an elaborate communication system that has more than 100 billion nerve cells in the brain alone. Memory, learning and language are all a part of the nervous system.

We need a volunteer… In this experiment you are required to say the colour of the word, not what the word says. For example, for the word, RED, if it is blue in color you should say "Blue.“ SAY THE COLOUR NOT THE WORD

Overview Has two divisions: the central nervous system (CNS) and the peripheral nervous system (PNS). CNS is all the nerves of the brain and spinal cord and is the coordinating centre for incoming and outgoing information. The PNS are the nerves that carry information between the organs of the body and the CNS

Somatic and Autonomic PNS can be divided further into the somatic and autonomic nerves. Somatic: controls the skeletal muscle, bones and skin. Autonomic: special motor nerves that control the internal organs of the body. Autonomic can be subdivided into the sympathetic and the parasympathetic.

2 Minute Task Organize the two systems into a flow chart GO

Anatomy of a Nerve Cell Two types: Glial cells: often called neuroglial cells and they are nonconducting cells that are important for the structural support and metabolism of the nerve cells. Neurons: are the functional units of the nervous system, they conduct the nerve impulses.

Specialized nerve cells are categorized into three groups: Sensory neurons: also called afferent neurons, can sense and relay information from the environment to the CNS for processing. Example: photoreceptors, chemoreceptors, thermoreceptors. They are found in clusters called ganglia outside the spinal cord. Interneurons: link neurons within the body, and are found mostly in the brain and spinal cord. They integrate and interpret the sensory information and connect neurons to outgoing motor neurons. Motor Neurons: also known as efferent neurons relay information to the effectors (muscles, organs, glands), which then produce a response.

Sensory Neuron

Motor Neuron

Put the pieces together… Dendrites receive information from the sensory receptors in sensory neurons, or from other nerve cells in the motor neurons. All nerve cells have a body (the soma) and the dendrites conduct impulses toward the cell body. An extension of the cytoplasm, called the axon, projects nerve impulses from the cell body. The axon carries the impulse towards the other neurons or towards the effectors.

Myelin Many axons are covered with a glistening white coat of a fatty protein called the myelin sheath that acts as insulation for the neurons. The myelin sheath is formed by special glial cells called Schwann cells. The areas between the Schwann cells are called the nodes of Ranvier. Electrical impulses jump from node to node, speeding up the movement of nerve impulses. Nerve impulses move a lot faster through myelinated nerves than through non-myelinated nerves.

For each think about WHY… The speed of the impulse along the nerve fiber is also affected by the diameter of the axon. The smaller the diameter, the faster the speed of the nerve impulse. All nerve fibres in the peripheral nervous system have a thin membrane called the neurilemma that surrounds the axon and promotes the regeneration of damaged axons. Myelinated cells in the brain have neurilemma and are said to be white matter due to the appearance of the myelin being white in colour. There are nerves which do not have myelin or neurilemma and are said to be grey matter and these cannot regenerate after injury and damage is usually permanent.

Explain what you think…

Reflex Reflexes are involuntary and usually an unconscious thing. The simplest nerve pathway is called the reflex arc. Most reflexes happen without even using the brain. Reflex arcs have five essential components: the receptor, sensory neuron, interneuron in the spinal cord, the motor neuron, and the effector.