Unit Three: The Biological Bases of Behavior

The body’s two communication systems, the nervous system and the endocrine system, both use chemical messengers to communicate with targets throughout the body How Does the Body Communicate Internally?

Central Nervous System (CNS) Peripheral Nervous System (PNS) Brain Spinal Cord Somatic Nervous System Autonomic Nervous System Sympathetic Nervous System Parasympathetic Nervous System The Nervous System

Figure 3.6 Organization of the human nervous system

Figure 3.7 The central and peripheral nervous systems Central nervous system (CNS) Afferent Nerves = toward the CNS Efferent Nerves = away from the CNS Peripheral nervous system Somatic nervous system Autonomic nervous system (ANS) Sympathetic Parasympathetic

Figure 3.8 The autonomic nervous system (ANS)

Communication in the Nervous System Two Types of Cells in the Nervous System:  Glia  Development: help in forming new synapses  Housekeeping: memory formation  Insulation: structural support and insulation (myelin sheath)  Protection: keeps brain toxin free; chronic pain/psychological disorders  Neurons – cell in the nervous system specialized to receive, process, and/or transmit information to other cells

Figure 3.1 Structure of the neuron Dendrites Soma Axon Terminal buttons

The Neuron Types of Neurons: Sensory neurons (carry messages from sense receptors towards the CNS) Motor neurons (carry messages from CNS toward muscles and glands) Interneurons (From sensory neurons to other interneurons or to motor neurons)

The Neuron

The Structure of a Neuron

The Neural Impulse: Electrochemical Beginnings  Hodgkin & Huxley (1952) - giant squid  Fluids inside and outside neuron  Electrically charged particles (ions)  Neuron at rest – negative charge on inside compared to outside  -70 millivolts – resting potential

The Neural Impulse  Neural impulse – Brief electric surge that carries the neuron’s message  Ions – Charged particles that are moved across the cell membrane

The Neural Impulse: The Action Potential  Stimulation causes cell membrane to open briefly  Positively charged sodium ions flow in  Shift in electrical charge travels along neuron  All – or – none law: Size of the action potential is unaffected by increases in the intensity of stimulation beyond the threshold level

The Neural Impulse: The Resting Potential Polarization of cellular fluid within a neuron, which provides the capacity to produce an action potential

The Neural Impulse: (cont.)  Graded Potentials  Temporal Summation  Spatial Summation

The Refractory Period The neuron can’t fire or will fire with more intense stimulation

Figure 3.2 The neural impulse

The Synapse: Chemicals as Signal Couriers  Synaptic cleft  Presynaptic neuron  Synaptic vesicles  Neurotransmitters  Postsynaptic neuron  Receptor sites

Figure 3.3 The synapse

When a Neurotransmitter Binds: The Postsynaptic Potential  Voltage change at receptor site – postsynaptic potential (PSP)  Not all-or-none  Changes the probability of the postsynaptic neuron firing  Positive voltage shift – excitatory PSP  Negative voltage shift – inhibitory PSP

Figure 3.4 Overview of synaptic transmission

Synaptic Transmission

Signals: From Postsynaptic Potentials to Neural Networks  One neuron; signals from thousands of other neurons  Requires integration of signals  PSPs add up, balance out  Balance between IPSPs and EPSPs  Neural networks  Patterns of neural activity  Interconnected neurons that fire together or sequentially

Signals: From Postsynaptic Potentials to Neural Networks  Synaptic connections  Elimination and creation  Synaptic pruning

Figure 3.5 Synaptic pruning

Neurotransmitters  Chemical messengers that relay neural messages across the synapse  Specific neurotransmitters work at specific synapses  Lock and key mechanism  Agonist – mimics neurotransmitter action  Antagonist – opposes action of a neurotransmitter  15 – 20 neurotransmitters known at present  Interactions between neurotransmitter circuits

Seven Important NeurotransmittersDopamine Serotonin Acetylcholine Glutamine Norepinephrine GABA Endorphins

Neurotransmitters Dopamine Serotonin Acetylcholine Glutamine Norepinephrine GABA Endorphins Normal Function: Produces sensations of pleasure and reward; used by CNS neurons in voluntary movement Problems with Imbalance: Schizophrenia, Parkinson’s disease Substances that Affect: Cocaine, amphetamines, Ritalin, alcohol

Dopamine Serotonin Acetylcholine Glutamine Norepinephrine GABA Endorphins Normal Function: Regulates sleep and dreaming, mood, pain, aggression, appetite and sexual behavior Problems with Imbalance: Depression, certain anxiety disorders, obsessive- compulsive disorder Substances that Affect: Prozac, hallucinogenics (e.g. LSD) Neurotransmitters

Dopamine Serotonin Acetylcholine Glutamine Norepinephrine GABA Endorphins Normal Function: Controls heart rate, sleep, sexual responsiveness, stress, vigilance and appetite Problems with Imbalance: High blood pressure, depression Substances that Affect: Tricyclic antidepressants, beta blockers

Neurotransmitters Dopamine Serotonin Acetylcholine Glutamine Norepinephrine GABA Endorphins Normal Function: Primary transmitter used by neurons carrying messages from CNS; involved in some kinds of learning and memory Problems with Imbalance: Certain muscular disorders, Alzheimer’s disease Substances that Affect: Nicotine, botulism toxin, curare, atropine

Neurotransmitters Dopamine Serotonin Acetylcholine Glutamine Norepinephrine GABA Endorphins Normal Function: Most prevalent inhibitory neurotransmitter in neurons of CNS Problems with Imbalance: Anxiety, epilepsy Substances that Affect: Barbiturates, tranquilizers (e.g. Valium, Librium), alcohol

Neurotransmitters Dopamine Serotonin Acetylcholine Glutamine Norepinephrine GABA Endorphins Normal Function: Primary excitatory neurotransmitter in CNS; involved in learning and memory Problems with Imbalance: Brain damage after stroke Substances that Affect: PCP (“angel dust”)

Neurotransmitters Dopamine Serotonin Acetylcholine Glutamine Norepinephrine GABA Endorphins Normal Function: Pleasurable sensations and control of pain Problems with Imbalance: Lowered levels resulting from opiate addiction Substances that Affect: Opiates: opium, heroin, morphine, methadone