Nervous System Chapter 13 PDF

Chapter 13 Nervous System 1  Nervous System Overview Neurobiology – study of nervous system – Includes neuroanatomy and neurophysiology Nervous system functions include sensory perception (organized and interpreted), integration (combining information), motor planning...

Chapter 13 Nervous System 1  Nervous System Overview Neurobiology – study of nervous system – Includes neuroanatomy and neurophysiology Nervous system functions include sensory perception (organized and interpreted), integration (combining information), motor planning (output) Two main divisions – Central nervous system (CNS) is brain and spinal cord – Peripheral nervous system (PNS) is nerves and ganglia 13-2 Nervous System Overview 13-3  Peripheral Nervous System Sensory Division = from receptors to CNS – Somatic = signals from skin, muscle, bones and joints – Visceral = signals from thoracic and abdominal cavities Motor Division = from CNS to glands and muscles – Somatic = signal to skeletal muscle – Visceral = signal to glands, cardiac and smooth muscle Sympathetic = arouse the body Parasympathetic = energy intake and conservation 13-4  Neurons Nerve cell = neuron Fundamental physiological (Universal) properties 1. Excitability (irritability) – can respond to stimuli 2. Conductivity – can send signals to distant locations quickly 3. Secretion – can release chemical messengers (neurotransmitters) 13-5  Functional Classes of Neurons Sensory (afferent) neurons – detect stimuli Interneurons (association neurons) – receive signals and makes decisions about response Motor (efferent) neurons – send signals to muscles to provide response 13-6  Structure of a Neuron Neurosoma (soma or cell body) control center Nissl bodies contain compartmentalized rough ER Dendrites receive signals Axon sends action potentials – Synaptic knob (terminal button) – ending of axon branch that communicates with another cell 13-7  Neuroglia “glial cells” Outnumber neurons 10 to 1 Support cells – Protect and aid in function Glia means “glue” – Bind neurons together 13-8  Types of Neuroglia 1. CNS glia – Oligodendrocytes - myelinate to assist conduction Octopus-like with as many as 15 arm-like processes Each process spirals around the nerve fiber – Ependymal cells Cuboidal cells that line cavities of brain and spinal cord Secretes and circulates cerebral spinal fluid 13-9  Types of Neuroglia 1. CNS glia continued – Microglia – Small macrophages help in defense and disposal of debris and pathogens – Astrocytes Most abundant with many branches with ‘feet’ and star shaped provide supportive framework, create blood brain barrier provide and nourishment 13-10  Myelination of CNS Analagous to insulation on a wire Oligodendrocytes make fatty white matter of CNS Internodes – fiber segments covered by myelin Nodes of Ranvier – fiber segments with gaps in myelin 13-11  Synapses Meeting point of neuron and other cell Presynaptic neuron to postsynaptic neuron Communication is either – Chemical (neruotransmiters) – Electrical (ions) 13-12  Chemical Synapse Presynaptic neuron releases neurotransmitter to postsynaptic cell Neurotransmitters – messenger molecules – Some are excitatory, some are inhibitory – Acetylcholine (NMJ) – norepinephrine (sympathetic) – glutamate & aspartate (excitatory) – GABA & glycine (inhibitory) – dopamine, serotonin, histamine, >100 13-13  Chemical Synapse, continued Structures at a synapse: Synaptic knob of presynaptic cell Contains synaptic vesicles – packets of neurotransmitters Synaptic cleft Neurotransmitter receptors on postsynaptic cell 13-14  Electrical Synapse Connects Neurons, neuroglia, cardiac and smooth muscle cells Adjacent cells joined by gap junctions Ions diffuse from cell to cell Quick transmission – no delay at release and binding of neurotransmitter No integration or decision-making 13-15