Neurons Answers to the outline are bold, italic, and underlined

Neurons The nervous system is your body’s electrochemical communication system Comprised of your brain, spinal cord, and nerves- all of which are formed from neurons Perform 3 tasks: – Receive information from the other neurons that feed into it – Carry this information down its length – Pass the information on to the next neuron in line

Neurons Very limited in function- their main capability is transmitting an impulse, or firing While neurons come in a variety of shapes and sizes, they all have similar structures

Structure of a Neuron

Dendrite – The branching extensions of a neuron that receive information and conduct impulses toward the cell body

Structure of a Neuron Soma – The cell body of a neuron, which contains the nucleus and other parts that keep the cell healthy

Structure of a Neuron Axon – The extension of a neuron through which neural impulses are sent

Structure of a Neuron

Axon terminals – The endpoint of a neuron where neurotransmitters are stored

Transfer of Information The impulse that occurs when a neuron fires is called an action potential This is followed by a brief recharging period known as a refractory period At that point, a neuron is capable of another firing impulse if stimulated- as it rests and waits to fire again, it exists in a state of resting potential

Action Potential Refractory Period Resting Potential

Transfer of Information All neurons exist under the all-or-nothing principle, which means that each neuron fires with the same intensity no matter what the stimulation is that causes the action potential

Transfer of Information No two neurons are in contact with one another- so the information has to find a way to get from one neuron to the next The fluid-filled gap that exists between the dendrites of one neuron and the axon terminal of another is called the synapse or synaptic gap The information crosses the gap aboard a chemical messenger called neurotransmitters

Neurotransmitters

Transfer of Information The neurotransmitter will cause the receiving neuron to do one of two things: – If it causes the receiving neuron to fire, it creates an excitatory effect – If it causes the receiving neuron to stay at rest, it creates an inhibitory effect

Transfer of Information Receptor cells located in the sensory systems of the body gather information such as sight, smells, and sounds. This information is then sent to the brain and spinal cord by sensory nerves where it is processed by billions of interneurons If an action of a muscle is needed due to the results of that processing, a new signal is sent to that muscle through motor nerves where an action takes place

A Neural Chain

Transfer of Information Certain chemicals can get in the way of this transfer of information: – Antagonists can block the effects of a neurotransmitter (ex. Paralyzing poison darts) – Agonists boost the effects of a neurotransmitter (ex. Black Widow spider venom)