NERVOUS SYSTEM II PP 1016-1024

NEURONS

Axons: extension of cell body Axon terminal: end of the axon Dendrites: receive action potentials (electrical impulse/message) from other neurons Synapse: gap between neurons Myelin sheath: lipid layer around axon (insulator) Schwann cells: produce myelin sheath

SENSORY NEURONS Most people think that we have only five senses but your body maintains homeostasis with more than 25 different types of senses Sensory neurons detect (sense) a stimulus to be processed by the central nervous system Sensory neurons have specific shapes to do their job Some body functions require more than one type of sensory neuron (i.e. balance)

TASTE SMELL

Taste and Smell Chemoreceptors Scent and taste are just chemicals

Vision Photoreceptors 2 types: cones (bright light) and rods (dim light)

Hearing and balance Mechanoreceptors The neurons look like hair and move to the vibration of air (hearing) or movement of fluid (balance)

Pressure and Temperature Mechanoreceptors and thermoreceptors

Tissue damage Pain receptors

NERVE IMPULSES

Think of the impulse as electrical and negative Resting potential: inactive due to “negatively” charged inside as compared to impulse Action potential: transmission of an electrical impulse by making inside more “positive”

When the impulse reaches the end (axon terminal) neurotransmitters are released from the neuron, into the synapse, to receptors in the next cell (dendrite)