Intro to the Nervous System Intro to the Nervous System-Crash Course- Resources page

Neurons Neurons are nerve cells that transfer information within the body Neurons use two types of signals to communicate: electrical signals (long-distance) and chemical signals (short-distance)

Neuron Structure and Function Most of a neuron’s organelles are in the cell body Most neurons have dendrites, highly branched extensions that receive signals from other neurons The axon is typically a much longer extension that transmits signals to other cells at synapses The cone-shaped base of an axon is called the axon hillock Most neurons are nourished or insulated by cells called glia

Processing Information Processing of information takes place in simple clusters of neurons called ganglia or a more complex organization of neurons called a brain Nervous systems process information in three stages: sensory input, integration, and motor output

The Nervous System Many animals have a complex nervous system that consists of A central nervous system (CNS) where integration takes place; this includes the brain and a nerve cord A peripheral nervous system (PNS), which carries information into and out of the CNS The neurons of the PNS, when bundled together, form nerves

Central Nervous System (CNS) In vertebrates The CNS is composed of the brain and spinal cord The peripheral nervous system (PNS) is composed of nerves and ganglia Invertebrates usually have a ventral nerve cord while vertebrates have a dorsal spinal cord The spinal cord and brain develop from the embryonic nerve cord The nerve cord gives rise to the central canal and ventricles of the brain

Central Nervous System The spinal cord conveys information from and to the brain The spinal cord also produces reflexes independently of the brain A reflex is the body’s automatic response to a stimulus

Peripheral Nervous System (PNS) The PNS transmits information to and from the CNS and regulates movement and the internal environment In the PNS, afferent neurons transmit information to the CNS and efferent neurons transmit information away from the CNS

Peripheral Nervous System The PNS has two efferent components: the motor system and the autonomic nervous system The motor system carries signals to skeletal muscles and is voluntary The autonomic nervous system regulates smooth and cardiac muscles and is generally involuntary

Autonomic System The sympathetic division regulates arousal and energy generation (“fight-or-flight” response) The parasympathetic division has effects on target organs and promotes calming and a return to “rest and digest” functions The enteric division controls activity of the digestive tract, pancreas, and gallbladder

Nervous Systems in Animals Nervous system organization usually correlates with lifestyle Sessile molluscs (for example, clams and chitons) have simple systems, whereas more complex molluscs (for example, octopuses and squids) have more sophisticated systems

Nervous Systems in Animals The simplest animals with nervous systems, the cnidarians, have neurons arranged in nerve nets A nerve net is a series of interconnected nerve cells More complex animals have nerves

Neurons Video How Neurons Work- Bioflix- Resources Page

Neuron Activity