THE NERVOUS SYSTEM Nerve Cells NERVE CELLS Called

THE NERVOUS SYSTEM Nerve Cells

NERVE CELLS Called “neurons” Three Types Motor Sensory Inter

MOTOR NEURONS Relays messages from brain or spinal cord to muscles and organs

SENSORY NEURONS Relays message from receptors (like in skin) to brain or spinal cord

INTERNEURONS Makes up the brain and spinal cord Relays messages from sensory to motor neurons

PARTS OF A NERVE CELL Cell body Nucleus Dendrites Axon Terminal Fibers Synaptic Endings Myelin Sheath

CELL BODY The largest part of the cell. It holds the general parts of the cell like the nucleus and other organelles needed for the cell to function

NUCLEUS Control Center of the cell Contains most of the cell’s DNA

DENDRITES Large, branching area near cell body Brings information TO cell body Rough Surface Usually many per cell

AXON Branch further from cell body Carries information AWAY from cell body Usually one per cell Smooth Surface

TERMINAL FIBERS Branches of an axon Have synaptic endings which send neurotransmitters from one cell to another

MYELIN SHEATH Insulating fat layer surrounding the axon of a nerve cell. Helps messages travel Faster and stops them From leaking away

WHAT IS A NERVE? A nerve is a discrete bundle of several thousand neuron axons wrapped around each other

HOW DO NERVES TRANSMIT MESSAGES?

ANSWER: Chemicals (transmitting molecules), called neurotransmitters, are sent from axon terminal across synapse (synaptic cleft) to a receptor on a dendrite.