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Unit III: Biological Bases of Behavior Ms. Justice AP Psychology 2014-2015 Unit III - Overview 9 – Biological Psychology & Neurotransmission 10 – The Nervous & Endocrine Systems 11 – Studying the Brain & Older Brain Structures 12 – The Cerebral Cortex 13 – Brain Hemisphere Organization & the Biology of Consciousness 14 – Behavior Genetics: Predicting Individual Differences 15 – Evolutionary Psychology Unit III: Biological Bases of Behavior Module 9 Biological Psychology & Neurotransmission Biology, Behavior, and Mind 9-1 Biology, Behavior, and Mind 9-1 • Phrenology - Franz Gall was correct in his assumptions that different parts of the brain do control different aspects of behavior… but that’s about it • Biological psychology - study the links between biological activity and psychological events Neurons 9-2 Neurons 9-2 The body’s information system is built from billions of interconnected cells called neurons. Hi! I’m a neuron… some of my friends call me “nerve cell” Neuron A nerve cell, or a neuron, consists of many different parts: 9-2 Parts of a Neuron 9-2 Cell Body: Life support center of the neuron. Dendrites: Branching extensions at the cell body. Receive messages from other neurons. Axon: Long single extension of a neuron, covered with myelin [MY-uh-lin] sheath to insulate and speed up messages through neurons. Terminal Branches of axon: Branched endings of an axon that transmit messages to other neurons. Action Potential 9-2 A neural impulse. A brief electrical charge that travels down an axon and is generated by the movement of positively charged atoms in and out of channels in the axon’s membrane. Action Potential 9-2 Threshold 9-2 threshold: the level of stimulation required to trigger a neural impulse Each neuron receives excitatory and inhibitory signals from many neurons. When the excitatory signals minus the inhibitory signals exceed a minimum intensity (threshold) the neuron fires an action potential… or if the excitatory party animals outvote the inhibitory party poopers, the party’s on. How Neurons Communicate 9-3 Synapses 9-3 Synapse [SIN-aps] - a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. This tiny gap is called the synaptic gap or cleft (which is less than a millionth of an inch wide!) Neurotransmitters Neurotransmitters are chemicals released from the sending neuron that travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing it to generate an action potential. 9-3 Reuptake Excess neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake. 9-3 How is a flushing toilet like a neuron firing? 9-3 How is a flushing toilet like a neuron firing? 9-3 •All-or-nothing principle – the toilet either flushes completely or not at all; it doesn’t flush a little or a lot •Direction of impulse – the toilet only flushes one way, the impulse can’t come the other direction (you hope!) •Refractory period – after you flush the toilet, it won’t flush again for a certain period of time, even if you push the handle repeatedly •Threshold – you can push the handle a little bit, but it won’t flush until you push the handle past a certain point (this corresponds to the level of excitatory neurotransmitters that a neuron must absorb before it will fire) •Resting potential –the toilet is waiting to fire, and the water in the tank represents the overall negative charge inside the neuron waiting for depolarization •Action potential – opening the flap in the tank and the water rushing through the pipes How Neurotransmitters Influence Us 9-4 Table 9.1, p. 82 9-4 Agonist versus Antagonists 9-4 Figure 9.6, p. 83