Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Your nervous system is a complex communication network in which signals are constantly being received, integrated, and transmitted. The nervous system handles information, just as the circulatory system handles blood. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Terminal Buttons and Synapses Dendrites Soma Myelin Sheath Axon There are two major types of cells in the nervous system: glia and neurons. Neurons are cells that receive, integrate, and transmit information. In the human nervous system, the vast majority are interneurons–neurons that communicate with other neurons. There are also sensory neurons, which receive signals from outside the nervous system, and motor neurons, which carry messages from the nervous system to the muscles that move the body. Terminal Buttons and Synapses Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Soma The soma, or cell body, contains the cell nucleus and much of the chemical machinery common to most cells. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Dendrites The branched structure is called a dendritic tree, and each individual branch is a dendrite. Dendrites are the parts of a neuron that are specialized to receive information Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Axon The long fiber is the axon. Axons are specialized structures that transmit information to other neurons or to muscles or glands. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Myelin Sheath Most human axons are wrapped in a myelin sheath. Myelin is a white, fatty substance that serves as an insulator around the axon and speeds the transmission of signals. In people suffering from multiple sclerosis, some myelin sheaths degenerate, slowing or preventing nerve transmission to certain muscles. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Terminal Buttons and Synapses The axon ends in a cluster of terminal buttons, which are small knobs that secrete chemicals called neurotransmitters. These chemicals serve as messengers that may activate neighboring neurons. The points at which neurons interconnect are called synapses. A synapse is a junction where information is transmitted from one neuron to another. Terminal Buttons and Synapses Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Glia Cells Glia come in a variety of forms. Their main function is to support the neurons by, among other things, supplying them with nutrients and removing waste material. In the human brain, there are about ten glia cells for every neuron. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Inside Electrode Outside Electrode Axon The neuron at rest is a tiny battery, a store of potential energy. Inside and outside the axon are fluids containing electrically charged atoms and molecules called ions. Positively charged sodium and potassium ions and negatively charged chloride ions are the principal molecules involved in the nerve impulse. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Inside Electrode Outside Electrode Axon 50 -50 -100 Milliseconds Millivolts Axon Inside Electrode Outside Electrode When the neuron is not conducting an impulse, it is said to be in a resting state. The cell membrane is polarized–negatively charged on the inside and positively charged on the outside. The charge difference across the membrane can be measured with a pair of microelectrodes connected to an oscilloscope. In a resting neuron, this difference, called the resting potential, is about –70 millivolts. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Click to play animation. Make sure volume is turned up. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Inside Electrode Outside Electrode Axon 50 -50 -100 Milliseconds Millivolts Inside Electrode Outside Electrode When the neuron is stimulated, channels in its cell membrane open, briefly allowing positively charged ions to rush in. For an instant, the neuron’s charge is less negative, or even positive, creating an action potential. An action potential is a very brief shift in the neuron’s electrical charge that travels along an axon. Axon Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Click to play animation. Make sure volume is turned up. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Action Potential No Action Potential OR 50 -50 -100 Milliseconds Millivolts 50 -50 -100 Milliseconds Millivolts OR The size of an action potential is not affected by the strength of the stimulus—a weaker stimulus does not produce a weaker action potential. If the neuron receives a stimulus of sufficient strength, it fires, but if it receives a weaker stimulus, it doesn’t. This is referred to as the “all-or-none law.” Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Terminal Buttons and Synapses Synaptic Cleft The neural impulse is a signal that must be transmitted from a neuron to other cells. This transmission takes place at special junctions called synapses, where terminal buttons release chemical messengers. The two neurons are separated by the synaptic cleft, a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron. Signals have to cross this gap for neurons to communicate. Terminal Buttons and Synapses Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Presynaptic Neuron Postsynaptic Neuron The neuron that sends a signal across the gap is called the presynaptic neuron. Click to continue. The neuron that receives the signal is called the postsynaptic neuron. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Neurotransmitter Molecules Synaptic Vesicles Neurotransmitter Molecules Neurotransmitters are chemicals that transmit information from one neuron to another. Within the buttons, most of these chemicals are stored in small sacs, called synaptic vesicles. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

The neurotransmitters are released when a vesicle fuses with the membrane of the presynaptic cell and its contents spill into the synaptic cleft. After their release, neurotransmitters diffuse across the synaptic cleft to the membrane of the receiving cell. Communication in the Nervous System Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

1 5 Reuptake of neurotransmitters sponged up by the presynaptic neuron Synthesis and storage of neurotransmitter molecules in synaptic vesicles 2 4 Inactivation (by enzymes) or removal (drifting away) of neurotransmitters Release of neurotransmitter molecules into synaptic cleft When a neurotransmitter and a receptor molecule combine, reactions in the cell membrane cause a postsynaptic potential, or PSP - a voltage change at the receptor site on a postsynaptic cell membrane. After producing postsynaptic potentials, some neurotransmitters either become inactivated by enzymes, or drift away. Most neurotransmitters, however, are reabsorbed into the presynaptic neuron through reuptake - a process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane. 3 Binding of neurotransmitters at receptor sites on postsynaptic membrane Communication in the Nervous System Postsynaptic Potentials and Reuptake Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Click to see a video that shows how neural networks work. Most neurons are interlinked in complex chains, pathways, circuits, and networks. Our perceptions, thoughts, and actions depend on patterns of neural activity in elaborate neural networks. Click to see a video that shows how neural networks work. Communication in the Nervous System Postsynaptic Potentials and Reuptake Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Disorders Associated with Dysregulation Neurotransmitters Disorders Associated with Dysregulation Acetylcholine (Ach) Alzheimer’s disease Dopamine (DA) Parkinsonism Schizophrenic disorders Addictive disorders Norepinephrine (NE) Depressive disorders Serotonin Depressive disorders Obsessive-compulsive disorders Eating disorders GABA Anxiety disorders Specific neurotransmitters work at specific kinds of synapses - the study of which has led to interesting findings about how specific neurotransmitters regulate behavior. One example is acetylcholine, which is released by motor neurons controlling skeletal muscles, and contributes to the regulation of attention, arousal, and memory. An inadequate supply of acetylcholine is associated with the memory losses seen in Alzheimer’s patients. Here are a few other examples of neurotransmitters, and how their dysregulation is associated with certain disorders. Glutamate Schizophrenia Endorphins Communication in the Nervous System Postsynaptic Potentials and Reuptake Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

The multitudes of neurons in your nervous system have to work together to keep information flowing effectively. Communication in the Nervous System Postsynaptic Potentials and Reuptake Postsynaptic Potentials and Reuptake Organization of the Nervous System The Brain and Behavior Cerebral Laterality The Endocrine System Heredity and Behavior

Continue on Chapter 3 Part B