Nervous System Function Neurons Base unit that has very simple function – “decide” whether to transmit signal or not Organization Billions of Neurons (estimates of 100 billion) Very complex interconnections Create systems/circuits that can function independently (parallel processing) “Simple decisions” passed to “higher” levels for that add additional information to create generate more complex decisions (hierarchical processing) Very expensive - less than 2% of weight but uses 20% of energy

Neuron Structure Cell Body Dendrites Axon Axon Terminals Nucleus – genetic information Dendrites Receive information Axon Carry information “long” distances Myelin (Multiple Sclerosis) Axon Terminals Transmit information

Neuron - Structure

Neuron Function Electrical Activity Chemical Activity Used to transmit signal within neuron Chemical Activity Used to transmit signal between neurons Synapse – small gap that physically separates neurons Neurotransmitters – special “chemicals” that neurons use to transmit message across the synapse

Neuron - Synapse

Synapse Function Neurotransmitter cycle in Axon Terminals Synthesis Storage Release Inactivation Reuptake Degradation Neural transmission problems if cycle disrupted (e.g., drugs) at any step

Synapse Function

Synapse Function

Nervous System Organization Central Nervous System (CNS) Spinal Cord – simple decisions & information transmission Brain – “complex” decisions Peripheral Nervous System (PNS) Somatic – sensory information & voluntary movement Autonomic Sympathetic – increases support increased physical activity Parasympathetic – increases support decreased physical activity Enteric – gastrointestinal system

Nervous System Organization

Autonomic Nervous System

Spinal Cord 31 segments with pairs (left & right) nerves carrying sensory and efferent information Functions Ascending and descending neural tracts Interneurons responsible for spinal reflexes (relatively simple decisions) Link sensory information (e.g., pain) with motor response (e.g., muscle contraction)

Brain Structure Very Complex General Principles Many different ways of describing brain structures (location, function, etc.) General Principles Layered Lateralized

Brain Neural Systems Brain circuits responsible for brain function E.g., - vision, hearing, movement, reward System could be Localized (vision) or diffuse (arousal) General (vision) or specific (color vision) Broad Divisions Sensory Motor Association

Brain Complex behaviors (fear/defensive learning) depend on many systems Sensory Learning Memory Output Differences in a function (e.g., motivation) might be due to different reasons (e.g., sensory, learning, etc.)