PSYC 211 - Chapter 2


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CHAPTER 2 – STRUCTURE AND FUNCTIONS OF CELLS Structure and Functions of Cells of the Nervous System Sensory Neurons : a neuron that detects changes in the external or internal environment and sends information about these changes to the central nervous system. Motor Neurons: a neuron located within the central nervous system that controls the contraction of a muscle or the secretion of a gland. Interneuron: a neuron located entirely within the central nervous system. o Lay between sensory neuron and motor neurons. o Local interneuron: form circuits with nearby neurons and analyse small pieces of information. o Relay interneuron: connect circuits of local interneurons in one region of the brain to those in other regions. Though these connections basic brain functions are performed: perceiving, learning, remembering, deciding, and controlling complex behaviours. Nervous system consists of two parts o Central Nervous System (CNS): consists of the parts that are encased in bone: the brain and the spinal cord. o Peripheral Nervous System (PNS): this system is found outside the brain and spinal cord, including nerves that are attached to the brain and spinal cord. PSNS consists of the nerves and most of the sensory organs. Cells of the Nervous System Neurons Neurons are the information processing and information-transmitting elements of the nervous system. Most neurons have: o A cell body or soma Contains the nucleus And other life supporting organelles Shape varies o Dendrites Look like trees Serve as important recipients of messages Messages are transported from the sending cell’s terminal buttons via a synapse to the soma or dendritic membrane of the receiving cell Synapse: a junction between the terminal buttons of the sending neuron and a portion of the dendritic membrane of the receiving neuron. Communication proceeds in one direction only: from the terminal button to the membrane of the other cell o Axon Long, slender tube, that is often covered in a myelin sheath 1
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Carry information from the cell body to the terminal buttons. The basic messages it carries is an action potential An action potential is like a brief pulse, it is always the same size and duration in a given neuron. o Terminal Buttons At the ends of the axons are knobs called terminal buttons. When action potentials reach terminal buttons they release neurotransmitter. Neurotransmitter: a chemical that is released by a terminal button; had an excitatory or inhibitory effect on another neuron. A neuron may receive information from hundreds of other neurons. Multipolar neuron: a neuron with one axon and many dendrites attached to its soma. o
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