A System for Communication & Regulation of Life Process The Nervous System A System for Communication & Regulation of Life Process

What Does the Nervous System Do?

It Helps Maintain Homeostasis

How?

It brings messages from one place to another. By Using Special Cells

are the basic functional unit of the nervous system. Neurons (Nerve cells) are the basic functional unit of the nervous system.

receive, conduct, and send impulses. Neurons receive, conduct, and send impulses.

A Typical Neuron Cyton Dendrite Terminal Bulbs Terminal Branches Axon

How Do Impulses Start?

They Need a Stimulus

Stimulus (plural = stimuli) a change in the external or internal environment that an organism responds to.

Light, Sound, Pressure, Cold, Hot, etc.. Examples External Light, Sound, Pressure, Cold, Hot, etc..

Chemicals Changes, Temperature Changes, etc... Examples Internal Chemicals Changes, Temperature Changes, etc...

Different Types of Neurons next slide

Inter-neuron Sensory Neuron Motor neuron ???

Parts of the Neuron Explained

The Dendrite Dendrites receive stimuli from sense organs or from other neurons in the form of a neurotransmitter.

Cell Body Cell Body conducts impulses from the dendrites toward the axon

Axon Axon conducts impulses from the cyton toward the terminal branches

Myelin Sheath Myelin Sheath - an arrangement of cells around the axon. It helps protect the axon and speed up impulses.

Terminal Branches Terminal Branches a fork in the axon.

Synaptic Knobs Synaptic Knobs- Releases chemicals called Neurotransmitters, which allow the message to be received by the next neuron, or a muscle, gland, organ etc… Terminal (Synaptic) Knobs

Neurotransmitters Impulse Direction Neurotransmitters Synapse

How Neurotransmitters Work Neurotransmitters diffuse from the end of one neuron to receptors on the next neuron. When they land on the specific receptor they allow gates to open that allow sodium to enter - this ignites the electro-chemical impulse to begin in the the next neuron.

Impulses

What are impulses?

The cell membrane of a neuron conducts electrical signals from on end to another - in one direction.

The inside of a neuron has an overall negative charge, and the outside has an overall positive charge. Outside Neuron Channels Inside neuron

The outside of a neuron has sodium ions (Na+) The outside of a neuron has sodium ions (Na+). The inside has negatively charged proteins.

Neither of these chemicals can pass through the cell membrane Neither of these chemicals can pass through the cell membrane. They are attracted to each other because of their opposite charge.

There are many protein channels along the membrane where sodium (Na+) can enter, but only when the gate is open. Stimuli cause the gates to open

The flow of charge (negatives or positives)across the membrane is electricity. This is why the impulse of a neuron is said to have an electrico-chemical nature.

Steps in making an impulse

Steps in making an impulse A stimulus occurs Either an external (sound, light, etc..) source or an internal source (such as a neurotransmitter).

Steps in making an impulse Gates Open This allows the sodium to enter the cell.

Steps in making an impulse Adjacent Gates Open The opening of one gate cause the next gate to open - like dominos

Steps in making an impulse The Impulse Travels to the End of the Neuron

Steps in making an impulse Neurotransmitters are released when the impulse reaches the Terminal Knobs

The Reflex Arc A special pathway

The Advantage of a Reflex The advantage of a reflex is that we can respond quickly to a stimulus. A reflex pathway does not involve the brain which is an advantage because the reflex is quicker.

Pathway of a Reflex Stimulus Sensory Neuron Sensory Organ Interneuron Effector (Muscle or Gland) Motor Neuron

Diseases of the Nervous System

Cerebral Palsy Results from brain damage, usually at birth. It is a term used to describe a group of diseases that affect the ability to control movement.

Multiple Sclerosis (MS) Results from damage to the Myelin Sheath. Symptoms vary but may include: shaking, blurred vision, slurred speech, and weakness.

Parkinson’s Disease Involves a particular group of brain cells in the brain. Symptoms: Tremors, poor balance, stiffening of the muscles. * The thinking functions is usually OK.

Alzheimer's Disease Degenerative disease of the brain. The person usually loses the ability to remember, think correctly and speak. The condition usually gets worse over time once it starts. It may take years to notice.

Notes This slide presentation is a work in progress. Please feel free to notify the author of any mistakes or suggestion for improvement.