Structure and function of Neuron.pptx

SSYA1013 Introduction to Psychology Dr. SANA ANWAR LASHARI Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  Chapter 3 Biological Foundations of Behavior Psychology: An Introduction...

SSYA1013 Introduction to Psychology Dr. SANA ANWAR LASHARI Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  Chapter 3 Biological Foundations of Behavior Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall The term nervous system refers to all neural tissue. This system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system includes the brain (the part of the nervous system that resides in the skull) and the spinal cord. The peripheral nervous system includes the remainder of the neural tissue in the rest of the body. Afferent nerves carry signals from the body to the CNS, whereas efferent nerves carry signals from the CNS to the body. Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  NEURONS  The basic unit of the nervous system is the neuron, a specialized cell that transmits neural impulses or messages to other neurons, glands, and muscles.  The many types of neurons in the nervous system differ markedly in size and appearance, but they all have certain common characteristics Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall Structure of Neuron Neurons hold the secrets of how the brain works. Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall Dendrites Projecting from the cell body, or soma, are a number of short branches called dendrites (from the Greek word dendron, meaning ‘tree’), which receive neural impulses from other neurons. Axon The axon is a slender tube that extends from the soma and transmits these messages to other neurons. Terminal Buttons At its end, the axon divides into a number of tiny branches that end in small swellings called synaptic terminals or terminal buttons. The terminal buttons do not actually touch the adjacent neuron. Synapse There is a slight gap between the terminal button and the cell body or dendrites of the receiving neuron. This junction is called a synapse, and the gap itself is called the synaptic gap Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall Neurotransmitter When a neural impulse travels down the axon and arrives at the terminal buttons, it triggers the secretion of a neurotransmitter. a chemical that diffuses across the synaptic gap and stimulates the next neuron, thereby transmitting the impulse from one neuron to the next. In this way, the post-synaptic (receiving) neuron integrates information from multiple pre-synaptic neurons. Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  Dendrites  Carry information to the cell body from other neurons  Cell Body (Soma)  Contains nucleus that bring information from dendrites to axon  Axon  Carries information to the next cell/neuron  Myelin Sheath  Insulates the axon and speeds up the neural impulse  Synapse  The synapse is the chemical junction between the axon terminals of one neuron and the dendrites of the next. It is a gap where specialized chemical interactions can occur, rather than an actual structure.  Glial Cells  The myelin sheath is not actually part of the neuron. Myelin is produced by glial cells (or simply glia, or “glue” in Greek), which are non-neuronal cells that provide support for the nervous system. Glia function to hold neurons in place (hence their Greek name), supply them with nutrients, provide insulation, and remove pathogens and dead neurons. In the central nervous system, the glial cells that form the myelin sheath are called oligodendrocytes; in the peripheral nervous system, they Psychology: are called Schwann cells. An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall Neurons are classified into three categories, depending on their general function. Sensory neurons transmit impulses received by receptors to the central nervous system. The receptors are specialized cells in the sense organs, muscles, skin, and joints that detect physical or chemical changes and translate these events into impulses that travel along the sensory neurons. Motor neurons carry outgoing signals from the central nervous system to muscles and glands. Interneurons connect sensory (afferent) and motor (efferent) neurons. Interneurons connect sensory (affer-ent) and motor (efferent) neurons. Interneurons are found only in the central nervous system and in the eyes. A nerve is a bundle of elongated axons belonging to hundreds or thousands of neurons. For example, the optic nerve carries the signals from the eye to the brain. A single nerve may contain axons from both sensory and motor neurons. The cell bodies of neurons are generally grouped together throughout the nervous system. Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall In the brain and spinal cord, a group of cell bodies of neurons is referred to as a nucleus (plural: nuclei). A group of neuronal cell bodies found outside the brain and spinal cord is called a ganglion (plural: ganglia). In addition to neurons, the nervous system has a large number of nonneural cells, called glial cells. Glial cells outnumber neurons by 9 to 1 and take up more than half the volume of the brain. The name glia, derived from the Greek word for ‘glue’, suggests one of their functions – namely, to hold neurons in place. In addition, they provide nutrients to the neurons and appear to ‘keep house’ in the brain by gathering and packaging up waste products and taking up dead neurons and foreign substances, thereby maintaining the signaling capacity of neurons. Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  Function of a Neuron  The specialized structure and organization of neurons allows them to transmit signals in the form of electric impulses from the brain to the body and back. Individually, neurons can pass a signal all the way from their own dendrites to their own axon terminals; but at a higher level neurons are organized in long chains, allowing them to pass signals very quickly from one to the other. One neuron’s axon will connect chemically to another neuron’s dendrite at the synapse between them. Electrically charged chemicals flow from the first neuron’s axon to the second neuron’s dendrite, and that signal will then flow from the second neuron’s dendrite, down its axon, across a synapse, into a third neuron’s dendrites, and so on.  This is the basic chain of neural signal transmission, which is how the brain sends signals to the muscles to make them move, and how sensory organs send signals to the brain. It is important that these signals can happen quickly, and they do. Think of how fast you drop a hot potato—before you even realize it is hot. This is because the sense organ (in this case, the skin) sends the signal “This is hot!” to neurons with very long axons that travel up the spine to the brain. If this didn’t happen quickly, people would burn themselves. Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall  Psychology: An Introduction Charles A. Morris & Albert A. Maisto © 2005 Prentice Hall