Chp 4 Textbook Notes

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Steve Joordens

Chapter 4: Biology of Behaviour human brain = 1.5 kg contains 10 billion 100 billion nerve cells and about as many helper cells ? nerve cells differ in shape, size, and chemicals they produce ? nerve cells organized into modules (clusters of nerve cells that communicate with each other) that are connected through neural circuits to other modules that communicate with each other Peirre Flourens suggested different parts of nervous system were responsible for different functions but conflicting evidence now some functions more spread out Donald Hebb (50 years ago) provided better understanding by showing that nerve cells are organized into larger units functioning could be understood by individual cells and larger networks they comprised Structure of Nervous System: brain controls behaviour, processes and retains information we receive from environment, and regulates bodys physiological processes ? receives information from bodys sensory receptors and is connected with muscles and glands of body nervous system consists of two divisions: ? Central Nervous System brain and spinal cord Spinal cord long, thin collection of nerve cells attached to base of brain and running length of spinal column contains circuits of nerve cells that control some simple reflexes (pulling away from hot) communicates with rest of body through nerves Nerves bundle of nerve fibres that transmit information between CNS and bodys sense organs, muscles, and glands ? attached to spinal cord and base of brain ? Peripheral nervous system cranial and spinal nerves; that part of the nervous system peripheral to brain and spinal cord consists of nerves that connect central nervous system with sense organs, muscles and glands human brain has 3 major parts: brain stem, cerebellum, cerebral hemisphere ? lower part of cerebellum and brain stem projects beneath left cerebral hemisphere upper part is normally hidden (see fig. 4.3) Brain stem most primitive regions of brain, and its functions are basic ones control of physiological functioning and automatic behaviour (amphibians have brain stem and simple cerebellum) Cerebral hemispheres constitute large portion of brain ? contains parts of brain that evolved most recently: involved in behaviours of particular interest to psychology Cerebellum attached to bain of brain, looks like miniature version of cerebral hemispheres ? functions are control and coordination of posture and movement, especially rapid ones brain is encased in skull and spinal cord runs through middle of hollow bones (vertebra: vertebral column) both brain and spinal cord are enclosed in 3 layered set of membrane called meninges float in clear liquid called Cerebrospinal fluid (CSF) ? fills between 2 meninges, providing cushioning Cerebral cortex outer layer of cerebral hemisphere of brain, approximately 3 mm thick ? often referred to as grey matter contains billions of nerve cells (abundant in nerve cell bodies rather than axons) ? where perceptions take place, memories are stored, plans are formulated and executed ? nerve cells in cerebral cortex are connected to other parts of brain by layer of nerve fibres called white Matter shiny white appearance of substance that coats and insulates axons that travel trough area (axons myelin sheath) ? very wrinkled appearance full of bulges separated by grooves bulges gyri grooves fissures they expand amount of surface are of cortex and greatly increase number of nerve cells more complex the brain, larger cortex Peripheral nervous system consists of nerves that connect central nervous system with sense organs, muscles and glands ? nerves carry incoming and outgoing information ? sense organs detect changes in environment and send signals through nerves to central nervous system ? brain sends signals through nerves to muscles (causing behaviour) and glands (producing adjustments in internal physiological processes) Nerves bundles of many thousands of individual fibres all wrapped in tough, protective membrane (look like table clothes) ? nerve fibres transmit message through nerve, from sense organ to brain or from brain to musclegland ? these make up white matter and other axon tracts ? some attached to spinal cord and others to brain Spinal nerves bundle of nerve fibres attached to spinal cord; conveys sensory information from body and carries messages to muscles and glands Cranial nerves 12 pairs, attached to base of brain; conveys sensory information from face and head and carries messages to muscles and glands Cells of Nervous System Neurons nerve cell; consists of cell body with dentrites and an axon whose branches end in terminal bittons that synapse to muscle fibres, gland cells, or other neurons ? elements of nervous system that bring sensory information to brain, store memories, reach decisions, control activity of muscles ? assisted by glia Glial cells cell of central nervous system that provides support for neurons and supplies them with essential chemicals ? during development of brain, some types of glial cells form long fibres that guide developing neurons from place of birth to final resting place ? manufacture chemicals that neurons need to perform tasks and absorb chemicals that might impair neurons functioning ? form protective insulating sheaths around nerve fibres ? serve as brains immune system, protecting it from micro-organisms Three basic parts of neuron: ? Soma cell body; largest part of neuron contains mechanisms that control metabolism and maintenance of cell receives messages from other neurons ? Dentrites treelike part of neuron on which other neurons form synapses transmit information they receive down trunks to soma ? Axon long, thin part of neuron attached to soma; divides into a few or many branches, ending in a terminal button carries message away from soma toward cell with which neuron communicates action potential (brief changes in electrical charge) also referred to as firing of an axon
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