The Nervous System maintains homeostasis and responds to stimuli faster than any other system! Part A. Organization Part B. Neural Tissue Chapter 12 Organization of the Nervous System and Neural Tissue The Nervous System maintains homeostasis and responds to stimuli faster than any other system! Part A. Organization Part B. Neural Tissue

Part I. Structural Organization of the Nervous System Slide 7.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.2

Organization of the Nervous System Slide 7.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Part I. The Central and Peripheral Nervous System Work Together to Maintain Homeostasis Slide 7.3a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.1

Part I. The CNS (brain, spinal cord) Performs Two Basic Functions 1.Integrates, Processes and Coordinates Sensory Information from inside and outside the body 2. It conducts all higher functions: intelligence, learning, memory, and emotion

Part I. The PNS is divided into Two Basic Parts: 1.Sensory Neurons- carry signals from sensory receptors (eye, ear, nose, etc) to CNS. AFFERENT 2. Motor Neurons- carry signals from CNS to muscles and glands EFFERENT

The Motor Division of the PNS is further divided: Slide 7.3c  Somatic Nervous System = voluntary, i.e. skeletal muscles  Autonomic Nervous System = involuntary, i.e. smooth muscle, cardiac muscle, and glands

The Autonomic Nervous System is a Stop and Go System STOP/SLOW Parasympathetic Neurons active during rest and rumination GO-Sympathetic Neurons active for fight or flight response

Part II. Histology of the Nervous System: I. Neurons-transmit nerve impulses Lots of neurons together make up a nerve II. Neuroglia-support neurons

Neurons transmit signals chemically and electrically Slide 7.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  How does their structure enable them to perform this function?  Three Major Parts of Neurons:  Cell body (soma)  Dendrites  Axon

Part II. Neuron Anatomy Slide 7.10  Dendrites – conduct impulses toward the cell body- why so many?  Axons – conduct impulses away from cell body to another neuron, a muscle, or a gland Figure 7.4a

Part II. Dendrites and Axons Terminals Slide 7.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Dendrites- lots of dendritic spines-why?  Axons-Contain fibrils, tubules, vesicles, mitochondria  Axons end in Synaptic Terminals  separated from the next neuron by a gap called Synaptic cleft –  Synapse – junction between nerves

Nerve Fiber Coverings Slide 7.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Axons, especially those in the PNS, are often covered with a white phospholipid material called myelin  Myelin increases the speed of impulse conduction, and insulates and maintains the axon Figure 7.5

Part II. Neuron Anatomy Slide 7.9a  Cell body  Nucleus-DNA  Perikaryon- neurofibrils that extend into dendrites  Large nucleolus- why?  Nissl substance – specialized rough ER-why?  Why don’t most neurons have centrioles? Figure 7.4a

Neurons are covered with Myelin Slide 7.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Schwann cells (PNS) or Oligodendrocytes (CNS)– produce myelin sheaths in jelly-roll like fashion  Nodes of Ranvier – gaps in myelin sheath along the axon Figure 7.5

Part II. Structural Classification of Neurons Slide 7.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Multipolar neurons (most neurons) – many extensions from the cell body Figure 7.8a

Structural Classification of Neurons Slide 7.16c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Unipolar neurons – have a short single process leaving the cell body Figure 7.8c

Structural Classification of Neurons Slide 7.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Bipolar neurons – one axon and one dendrite  Where would you find this type of neuron? Figure 7.8b

Part II. Functional Classification of Neurons: Afferent vs. Efferent Slide 7.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.6

Part III. Neuroglial Cells Support Neurons 1. produce the blood-brain barrier 2. produce the myelin sheath around axons of the CNS 3. carry out phagocytosis 4. line cavities of brain and spinal cord, produce CSF 5. produce myelin around neurons in PNS 6. protect neuron cell bodies

Part III. Neuroglia Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Astrocytes- star-shaped cells  Blood-brain barrier -control chemical environment of brain  Brace neurons Figure 7.3a

Part III. Neuroglia Slide 7.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Oligodendrocytes  Produce myelin around nerve fibers in CNS  Myelin increases the speed of impulse conduction Figure 7.3d

Part III. Neuroglia Slide 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Microglia  Phagocytes-dispose of debris  Ependymal cells  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid Figure 7.3b, c

Part III. Neuroglia Slide 7.7b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Schwann cells  Form myelin sheath in jelly-roll like fashion-PNS  Satellite cells-protect neuron cell bodies Figure 7.3e

Gray matter has NO myelin (why not?) White Matter is Myelinated (why?)