Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings CHAPTER 7 The Nervous System  The master controlling and communicating system of the body  Functions  Sensory input – monitoring stimuli occurring inside and outside the body  Integration – interpretation of sensory input  Motor output – response to stimuli by activating effector organs

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System Figure 11.1

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Organization of the Nervous System  Central nervous system (CNS)  Brain and spinal cord  Integration and command center  Peripheral nervous system (PNS)  Paired spinal and cranial nerves  Carries messages to and from the spinal cord and brain

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Sensory (afferent) division  Sensory afferent fibers – carry impulses from skin, skeletal muscles, and joints to the brain  Visceral afferent fibers – transmit impulses from visceral organs to the brain  Motor (efferent) division  Transmits impulses from the CNS to effector organs Peripheral Nervous System (PNS): Two Functional Divisions

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Somatic nervous system  Conscious control of skeletal muscles  Autonomic nervous system (ANS)  Regulates smooth muscle, cardiac muscle, and glands  Divisions – sympathetic and parasympathetic Motor Division: Two Main Parts

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The two principal cell types of the nervous system are:  Neurons – excitable cells that transmit electrical signals  Supporting cells – cells that surround and wrap neurons Histology of Nerve Tissue

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The supporting cells (neuroglia or glial cells):  Provide a supportive scaffolding for neurons  Segregate and insulate neurons  Promote health and growth  Metabolic activities Supporting Cells: Neuroglia

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Schwann cells– surround fibers of the PNS  Myelinated neurons vs. unmyelinated neurons  Protect the axon  Electrically insulate fibers from one another  Increase the speed of nerve impulse transmission Oligodendrocytes, Schwann Cells, and Satellite Cells

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11.3d, e Oligodendrocytes, Schwann Cells, and Satellite Cells

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Structural units of the nervous system  Composed of a body, axon, and dendrites  Long-lived, amitotic, and have a high metabolic rate  Their plasma membrane functions in:  Electrical signaling  Cell-to-cell signaling during development Neurons (Nerve Cells)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Neurons (Nerve Cells) Figure 11.4b

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cerebral Hemispheres  Contain ridges (gyri) and shallow grooves (sulci)  Contain deep grooves called fissures

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  The three types of functional areas are:  Motor areas – control voluntary movement  Sensory areas – conscious awareness of sensation  Association areas – Special senses area - integrate diverse information Functional Areas of the Cerebral Cortex

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings  Primary sensory area: carry information concerning temp., touch, pressure, pain etc…  The Cerebellum- maintaining balance, regulating and coordinating voluntary movements  Spinal reflexes Primary Motor Cortex Allows conscious control of precise, skilled, voluntary movements Motor function

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Reflex Arc Figure Receptor Sensory neuron Integration center 5 Effector Motor neuron Stimulus Skin Spinal cord (in cross-section) Interneuron

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Association Areas Figure 12.8a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Protection of the Brain  The brain is protected by bone, meninges, and cerebrospinal fluid  Harmful substances are shielded from the brain by the blood-brain barrier

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Meninges  Functions of the meninges  Cover and protect the CNS  Protect blood vessels and enclose venous sinuses  Contain cerebrospinal fluid (CSF)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Peripheral Nervous System  Mixed nerves – carry somatic and autonomic (visceral) impulses  The four types of mixed nerves are:  Somatic afferent and somatic efferent  Visceral afferent and visceral efferent  Peripheral nerves originate from the brain or spinal column

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cranial Nerves Twelve pairs of cranial nerves arise from the brain  31 pairs of spinal nerves  Sympathetic vs. parasympathetic division

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Age-related changes Loss of nerve cellsSkeletal muscle: Recall: postmitotic/ gradual reduction, swelling of axons, loss of myelin around the neurons Loss of a significant number of cerebellar cells  may affect balance and coordination Reduction of brain mass/associated with learning new skills Decline in speed of response, memory, and integration Some increase in neural connection due to establishment of new synapses Decline in intelligence (IQ test) Educated people/ not educated people Memory is affected by age Long-term memory/short-term memory Decrease in rate of conduction Decrease in enzyme function/role of neurotransmitter Problem in transmission of impulses due to reduction of dendrites Accumulation of lipofucins (cross-linked with proteins) The Golgi complex and mitochondria in aging neurons (Nissl bodies) Neurofibrillary tangles and neuritic plaques in hippocampus (associated with memory) and some nerve cells and thus affect metabolism in aging neurons Degenerative changes in Glial cells  interfering with the supply of nutrients Increase in the amount of norepinephrine in the blood with aging/ related to sympathetic system

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Age-related changes Decrease reflex responses Declining Autonomic Responses Insomnia Dementia Alzheimer’s disease Non-Alzheimer dementias Multi-infraction dementia Parkinson’s disease Cerebrovascular accident