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