Psychology: Themes and Variations, Sixth Edition, Briefer Version, Wayne Weiten Chapter 3. The Biological Bases of Behavior

Transcription

1 The Biological Bases of Behavior

2 Communication in the Nervous System Hardware: Glia structural support and insulation Neurons communication Soma cell body Dendrites receive Axon transmit away Terminal buttons secrete neurotransmitters Synapse junction where information is transmitted

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4 Animation of Neural Transmission NIH Animation - Neural Transmission

5 Figure 3.1 Psychology: Themes and Variations, Sixth Edition, Briefer Version, Wayne Weiten Figure 3.1 Structure of the neuron. Neurons are the communication links of the nervous system. This diagram highlights the key parts of a neuron, including specialized receptor areas (dendrites), the cell body (soma), the axon fiber along which impulses are transmitted, and the terminal buttons, which release chemical messengers that carry signals to other neurons. Neurons vary considerably in size and shape and are usually densely interconnected.

6 Myelinization Glial cells wrap themselves around axons and this increases the speed of neural conduction

7 Myelinization & neurons

8 The Neural Impulse: The Action Potential The Action Potential All or none law

9 Figure 3.2. Figure 3.2. The neural impulse. The electrochemical properties of the neuron allow it to transmit signals. The electric charge of a neuron can be measured with a pair of electrodes connected to an oscilloscope, as Hodgkin and Huxley showed with a squid axon. Because of its exceptionally thick axons, the squid has frequently been used by scientists studying the neural impulse. (a) At rest, the neuron s voltage hovers around 70 millivolts. (b) When stimulated, there is a brief jump in a neuron s voltage, resulting in a spike on the oscilloscope recording of the neuron s electrical activity. This change in voltage, called an action potential, travels along the axon like a spark traveling along a trail of gunpowder.

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11 The Synapse: Where Neurons Meet Synaptic cleft Presynaptic neuron Synaptic vesicles Neurotransmitters Postsynaptic neuron Receptor sites

12 Figure 3.3 Psychology: Themes and Variations, Sixth Edition, Briefer Version, Wayne Weiten Figure 3.3 The synapse. When a neural impulse reaches an axon s terminal buttons, it triggers the release of chemical messengers called neurotransmitters. The neurotransmitter molecules diffuse across the synaptic cleft and bind to receptor sites on the postsynaptic neuron. A specific neurotransmitter can bind only to receptor sites that its molecular structure will fit into, much like a key must fit a lock.

13 Figure 3.4 Psychology: Themes and Variations, Sixth Edition, Briefer Version, Wayne Weiten Figure 3.4 Overview of synaptic transmission. The main elements in synaptic transmission are summarized here, superimposed on a blowup of the synapse seen in Figure 3.3. The five key processes involved in communication at synapses are (1) synthesis and storage, (2) release, (3) binding, (4) inactivation or removal, and (5) reuptake of neurotransmitters. As you ll see in this chapter and the remainder of the book, the effects of many phenomena such as pain, drug use, and some diseases can be explained in terms of how they alter one or more of these processes (usually at synapses releasing a specific neurotransmitter).

14 Neurotransmitters: Chemical Couriers Neurotransmitters Work in a lock and key fashion Agonist mimics neurotransmitter action Antagonist blocks action of a neurotransmitter

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18 Organization of the Nervous System Central nervous system (CNS) brain and spinal cord Peripheral nervous system nerves that lie outside the central nervous system Somatic nervous system voluntary muscles and sensory receptors Autonomic nervous system (ANS) controls automatic, involuntary functions Sympathetic Go (fight-or-flight) Parasympathetic Stop

19 Figure 3.5 Psychology: Themes and Variations, Sixth Edition, Briefer Version, Wayne Weiten Figure 3.5 Organization of the human nervous system. This overview of the human nervous system shows the relationships of its various parts and systems. The brain is traditionally divided into three regions: the hindbrain, the midbrain, and the forebrain. The reticular formation runs through both the midbrain and the hindbrain on its way up and down the brainstem. These and other parts of the brain are discussed in detail later in the chapter. The peripheral nervous system is made up of the somatic nervous system, which controls voluntary muscles and sensory receptors, and the autonomic nervous system, which controls the involuntary activities of smooth muscles, blood vessels, and glands.

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21 Brain Regions and Functions Hindbrain medulla, pons, and cerebellum Midbrain dopaminergic projections, reticular formation Forebrain thalamus, hypothalamus, limbic system, cerebrum, cerebral cortex

22 The Cerebrum: Two Hemispheres, Four Lobes Cerebral Hemispheres two specialized halves connected by the corpus collosum Four Lobes: Occipital vision Parietal somatosensory Temporal auditory Frontal movement, executive control systems

23 View of the Brain Figure 3.14 The cerebral cortex in humans. The cerebral cortex consists of right and left halves, called cerebral hemispheres. This diagram provides a view of the right hemisphere. Each cerebral hemisphere is divided into four lobes (which are highlighted in the bottom inset): the occipital lobe, the parietal lobe, the temporal lobe, and the frontal lobe. Each lobe has areas that handle particular functions, such as visual processing. The functions of the prefrontal cortex are something of a mystery, but they appear to include working memory and relational reasoning.

24 Brain Overview

25 The Limbic System Saul Kassin, Psychology. Copyright 1995 by Houghton Mifflin Company. Reprinted by permission.

26 Figure 3.12 Figure 3.12 Electrical stimulation of the brain (ESB) in the rat. Olds and Milner (1954) were using an apparatus like that depicted here when they discovered selfstimulation centers, or pleasure centers, in the brain of a rat. In this setup, the wire delivering electrical stimulation is suspended from above so the rat can move freely about the box. When the rat presses the lever, it earns brief electrical stimulation that is sent to a specific spot in the rat s brain where an electrode has been implanted.

27 Figure 3.13 Figure 3.13 The cerebral hemispheres and the corpus callosum. In this drawing the cerebral hemispheres have been pulled apart to reveal the corpus callosum. This band of fibers is the communication bridge between the right and left halves of the human brain. Photo: Wadsworth collection.

28 2 Hemispheres /Corpus Callosum Left hemisphere verbal processing: language, speech, reading, writing Right hemisphere nonverbal processing: spatial, musical, visual recognition

29 Hindbrain Medulla Pons Cerebellum BRAIN STRUCTURES AND FUNCTIONS

30 Figure 3.15 Alzheimer s Disease and Brain Atrophy