Organization of the nervous system: The body is innervated by neurons that send information to the brain and carry out commands sent by the brain.
Neurons and Glia: The neuron is a cell that is specially designed for receiving, propagating, and transmitting signals. Glial Cells provide the environment required for neurons to do their job.
In the Central Nervous System: glial cells include - ependymal cells, astrocytes, oligodendrocytes and microglia.
In the peripheral nervous system glial cells include - schwann cells and satellite cells.
Receiving: A neuron communicates with other neurons at synapses, small spaces between terminal branches of one neuron and dendrites of another.
Transmitting: Nodes of Ranvier: the electrical signal jumps from one of these gaps in myelin to the next.
Myelin Sheath: the axon is wrapped in fatty membranes called myelin that increase electrical conductivity, allowing the signal to travel long distances (mm).
Sending: Synapse: the empty space between one neuron’s terminal branches and the next neurons dendrites. Neurotransmitters: molecules released from the terminal branches when the impulse arrives from the axon.
The Action Potential
- Resting Potential: Before the neuron is excited, the inside of the cell has a negative charge and the outside is positively charged.
- Action Potential: When another neuron sends a sufficiently strong signal to the next neuron, the neuron excites to a threshold potential.
Central Nervous System: the CNS includes the brain and spinal cord.
- Brain: the brain is made up of the following regions – Cerebrum, Cerebellum, Hypothalamus and the Brainstem.
- Spinal Cord: Receiving: the PNS receives data (such as sights, sounds) and sends it to the CNS for processing. Sending: the CNS sends commands to the PNS in response to inputs, and the PNS carries them out (e.g. move arm). The spinal cord is the information highway connecting the brain and the rest of the body.
Peripheral Nervous System
Overview: the peripheral nervous system (PNS) includes the nerves, which receive input and directly control the body.
- Sensory Nervous System: The sensory nervous system includes sensory organs, which receive information from the environment, and sends it to the CNS. Each sense organ has unique receptors, which register the signals from the environment.
- Motor Nervous System: The somatic system directly controls voluntary movement. The autonomic system directly controls automatic body functions (involuntary movements).