1. The Nervous System

2. Introduction In all animals, except the sponges, responses to stimuli depend on the activities of networks of nerve cell, or neurons. Neurons are specialized cells for transmitting neural signals, which are electrical signals and chemical messages.

3. Parts of the Neuron Dendrites: projections used to conduct electrical messages received from other neural cells to the cell body. Cell Body: Contains lots of ribosomes and RERs to make proteins needed for the neuron; also passes received messages out through the axon.

4. Parts of the Neuron Axon: long projection that conducts electrical messages away from the cell body; connect with other neurons/cells at synapses. Schwann Cells: a form of glial cells that make up the myelin sheath; support and protect the axon.

5. Parts of the Neuron Myelin Sheath: an electrical insulating cover of the axon that speeds up the transmission of electrical signals. Majority of neurons are myelinated. Node of Ranvier: gaps in the myelin sheath that allow for saltatory conduction of an action potential (i.e. the signal jumps from gap to gap)

6. Nervous System In most animals, neurons and the supporting tissue are organized into a nervous system. The nervous system works in conjunction with many of the body’s other systems in order to maintain homeostasis.

7. Nervous System The nervous system contains 2 distinct parts: 1)Central Nervous System (CNS) Contains the nerves in your brain and spinal cord. Has control over the majority of body processes as it controls the peripheral nerves.

8. Nervous System 2) Peripheral Nervous System (PNS): Contains all the nerve cells that are not associated with the CNS. Autonomic division controls all involuntary processes in our bodies. Somatic division controls all voluntary processes in our bodies.

9. Neural Signalling An animal is constantly being bombarded with stimuli. Appropriate response to stimuli depends on neural signalling, which is communication between neurons.

10. Neural Signalling Neural signalling involves four processes: 1)Reception 2)Transmission 3)Integration 4)Action

11. Neural Signalling Reception is the process of detecting stimuli. It is the job of special neurons called sensory neurons (unipolar neurons) or organs like the eyes and ears.

12. Neural Signalling Transmission is the process of sending messages along the nervous system usually to or from the brain. Sensory neurons carry messages to the central nervous system. Afferent neurons are any neurons that carry messages to the CNS. Therefore sensory neurons are afferent neurons.

13. Neural Signalling Integration involves sorting and interpreting messages and determining the appropriate response. Interneurons (bipolar neurons) do this job. Their cell body and axon are located within the CNS.

14. Neural Signalling Action involves the actual response to stimuli by the body’s effectors. Motor neurons (multipolar neurons) do this job. They carry messages away from the CNS to effectors like muscles. Efferent Neurons are any neurons that take messages away from the CNS, therefore motor neurons are efferent neurons.