Unit 3: Biological Bases of Behavior 3.2 The Nervous System

The Nervous System System that regulates the body’s responses to internal and external stimuli Neurons are the building blocks Split into 2 main parts: Central Nervous System Peripheral Nervous System

The Nervous System Central Nervous System (CNS) brain & spinal cord Peripheral Nervous System (PNS) communicates between CNS & all other parts of the body

Central Nervous System Neurons work in groups called neural networks Brain – most neurons here are small & have diff. functions/neurotransmitters Spinal cord – column of nerves in spine transmits messages to/from brain Send sensory info up to the brain Send motor-control info back down These spinal reflexes happen so fast we often don’t feel pain/sensation until after the reaction

Peripheral Nervous System Broken up into 2 parts Somatic Nervous System (SNS) Controls body’s skeletal muscles Voluntary movements Also transmits senses to CNS like temp. and pressure Autonomic Nervous System (ANS) Regulates body’s vital functions – heart beating, breathing, digestion, etc Can sometimes be consciously overridden, but usually operates on it’s own

Peripheral Nervous System ANS is a dual system too Sympathetic Nervous System Expends energy, “fight or flight” Makes heart beat faster, breathing get faster, raises blood pressure Parasympathetic Nervous System Conserves energy by calming you, “rest and digest” Decreases heartbeat, lowers blood pressure, breathing slows Work together to keep body in balance (homeostasis)