The Human Nervous System

Neuron- A Nerve Cell Contains the nucleus and other organelles Cell body Contains the nucleus and other organelles Dendrites Receive stimuli Conduct impulses toward the cell body Axon Carries impulses away from the cell body

Axon Structure Insulating coat of plasma membranes Myelin sheath Insulating coat of plasma membranes Sections of sheath are called “Schwann Cells” Unmyelinated axons carry impulses much slower than myelinated axons Nodes of Ranvier Bare axonal membrane between Schwann cells

The Synapse Synapse The gap between nerve cells Neurotransmitter Chemicals that carry nerve signals across the synapse

Reflex Arc The reflex arc responds to a stimulus without the immediate involvement of the brain

Central Nervous System (CNS) Brain Spinal Cord

Cerebrum Directs voluntary movement Sensory processing Language and communication Learning and memory

Cerebellum Regulates sense of balance Coordinates voluntary muscle movement

Medulla Oblongata Breathing Heart rate Blood pressure Swallowing and digestion

Peripheral Nervous System (in blue)

Peripheral Nervous System Sensory Division Bring information to the CNS Motor Division Carries signals away from the CNS Somatic (voluntary) nervous system controls skeletal muscle action Autonomic nervous system (involuntary) controls organ systems and smooth muscle

Divisions of the Autonomic Nervous System Sympathetic Stress responses (Fight or Flight) Pupils dilate Mouth dries up (saliva decreases) Heart rate increases Blood flow to skeletal muscle increases Parasympathetic Relaxation response Heart rate slows Pupils constrict Stimulates salivation Digestive processes stimulated