Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slides 7.1 – 7.22 Seventh Edition Elaine N. Marieb Chapter 7 The Nervous System Lecture Slides in PowerPoint by Jerry L. Cook

Overview of the Nervous System Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Homeostatsis Endocrine System (uses chemicals, hormones, via the blood stream to effect target cells) Nervous System (uses electrochemical signals via neurons to effect muscles and glands)

Overview of the Nervous System Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nervous System Central Nervous System (CNS) Brain and spinal cord Peripheral Nervous System (PNS) Cranial and spinal nerves

Overview of the Nervous System Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Peripheral Nervous system Sensory (Afferent) Division (conveys impulses from sensory receptors to the CNS) Motor (Efferent) Division (carries impulses from CNS to effector organs, muscles, and glands)

Overview of the Nervous System Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Motor (Efferent) Division Somatic Nervous System (voluntary control) Autonomic Nervous System (involuntary control)

Overview of the Nervous System Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Autonomic Nervous System Sympathetic Division (“fight-or-flight” division) Parasympathetic Division (“resting and digesting” division)

The Central Nervous System Slide 7.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The CNS consists of the brain and the spinal cord.  They interpret incoming sensory input and issue instructions for motor output.

Functions of the Nervous System Slide 7.1a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sensory input – gathering information  To monitor changes occurring inside and outside the body  Changes = stimuli

Functions of the Nervous System Slide 7.1b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Integration  To process and interpret sensory input and decide if action is needed  Motor output  A response to integrated stimuli  The response activates muscles or glands

Nervous Tissue: Support Cells (Neuroglia) Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Neuroglia  support, insulate, and protect the neurons of the CNS.  resemble neurons but are not able to transmit nerve impulses  never lose their ability to divide, whereas neurons do Figure 7.3a

Nervous Tissue: Support Cells (Neuroglia) Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Types of Neuroglia  Astrocytes  Microglial cell  Ependymal cells  Oligodendrocyte Figure 7.3a

Nervous Tissue: Support Cells (Neuroglia) Slide 7.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Astrocytes  Connect neurons to blood capillaries, making an anchor between the two  Protect neurons from harmful substances that might be in the blood  Pick up excess ions and recapture released neurotransmitters Figure 7.3a

Nervous Tissue: Support Cells Slide 7.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Microglia  Phagocytes that dispose of debris  Ependymal cells  Ciliated cells that line the cavities of the brain and spinal cord  Cilia circulates the cerebrospinal fluid, which cushions the CNS Figure 7.3b, c

Nervous Tissue: Support Cells Slide 7.7a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Oligodendrocytes  Produce myelin sheath coverings around nerve fibers, called Schwann cells in the PNS Figure 7.3d

Nervous Tissue: Neurons Slide 7.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurons = nerve cells  Neurons are specialized cells that transmit messages from one part of the body to another  Unlike neuroglia, neurons transmit nerve impulses.

Neuron Anatomy Slide 7.9a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cell body (clusters called nuclei)  Cell processes  Axons  Dendrites  Axonal terminals  Myelin sheath, laid down by oligodendrocytes, which lack a neurilemma Figure 7.4a

The Synapse Slide 7.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurons never touch each other. They are separated by a tiny gap called the synaptic cleft.  The axonal terminal of the motor neuron house vesicles that contain neurotransmitters.

Nerve Impulses Slide 7.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neurons serve two functions:  Irritability (the ability to respond to a stimulus and produce a nerve impulse)  Conductivity (the ability to transmit the impulse to other neurons, muscles, or glands) Figure 7.5

Starting a Nerve Impulse Slide 7.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Depolarization – a stimulus depolarizes the neuron’s membrane  A deploarized membrane allows sodium (Na + ) to flow inside the membrane  The exchange of ions initiates an action potential in the neuron Figure 7.9a–c

The Action Potential Slide 7.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  If the action potential (nerve impulse) starts, it is propagated over the entire axon  Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane  The sodium-potassium pump restores the original configuration  This action requires ATP

Nerve Impulse Propagation Slide 7.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The impulse continues to move toward the cell body  Impulses travel faster when fibers have a myelin sheath Figure 7.9c–e

Continuation of the Nerve Impulse between Neurons Slide 7.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Impulses are able to cross the synapse to another nerve  Neurotransmitter is released from a nerve’s axon terminal  The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter  An action potential is started in the dendrite

How Neurons Communicate at Synapses Slide 7.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.10

Regions of the Brain Slide 7.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cerebral hemispheres  Diencephalon  Brain stem  Cerebellum Figure 7.12

Specialized Area of the Cerebrum Slide 7.32c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.13c

Layers of the Cerebrum Slide 7.33a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Gray matter  Outer layer  Composed mostly of neuron cell bodies Figure 7.13a

Layers of the Cerebrum Slide 7.33b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  White matter  Fiber tracts inside the gray matter  Example: corpus callosum connects hemispheres Figure 7.13a

Layers of the Cerebrum Slide 7.33c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Basal nuclei – internal islands of gray matter Figure 7.13a

Protection of the Central Nervous System Slide 7.44a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Scalp and skin  Skull and vertebral column  Meninges Figure 7.16a

Protection of the Central Nervous System Slide 7.44b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cerebrospinal fluid  Blood brain barrier Figure 7.16a

Meninges Slide 7.45a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Dura mater  Double-layered external covering  Periosteum – attached to surface of the skull  Meningeal layer – outer covering of the brain  Folds inward in several areas

Meninges Slide 7.45b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Arachnoid layer  Middle layer  Web-like  Pia mater  Internal layer  Clings to the surface of the brain

Cerebrospinal Fluid Slide 7.46 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Similar to blood plasma composition  Formed by the choroid plexus  Forms a watery cushion to protect the brain  Circulated in arachnoid space, ventricles, and central canal of the spinal cord

Ventricles and Location of the Cerebrospinal Fluid Slide 7.47b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.17b

Blood Brain Barrier Slide 7.48 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Includes the least permeable capillaries of the body  Excludes many potentially harmful substances  Useless against some substances  Fats and fat soluble molecules  Respiratory gases  Alcohol  Nicotine  Anesthesia

Spinal Cord Slide 7.52 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Extends from the medulla oblongata to the region of T12  Below T12 is the cauda equina (a collection of spinal nerves)  Enlargements occur in the cervical and lumbar regions Figure 7.18

Spinal Cord Anatomy Slide 7.53a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Exterior white mater – conduction tracts Figure 7.19

Spinal Cord Anatomy Slide 7.53b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Internal gray matter - mostly cell bodies  Dorsal (posterior) horns  Anterior (ventral) horns Figure 7.19

Spinal Cord Anatomy Slide 7.53c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Central canal filled with cerebrospinal fluid Figure 7.19

Spinal Cord Anatomy Slide 7.54 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Meninges cover the spinal cord  Nerves leave at the level of each vertebrae  Dorsal root  Associated with the dorsal root ganglia – collections of cell bodies outside the central nervous system  Ventral root

Peripheral Nervous System Slide 7.55 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Nerves and ganglia outside the central nervous system  Nerve = bundle of neuron fibers  Neuron fibers are bundled by connective tissue

Classification of Nerves Slide 7.57 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Mixed nerves – both sensory and motor fibers  Afferent (sensory) nerves – carry impulses toward the CNS  Efferent (motor) nerves – carry impulses away from the CNS

Cranial Nerves Slide 7.58 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  12 pairs of nerves that mostly serve the head and neck  Numbered in order, front to back  Most are mixed nerves, but three are sensory only

Distribution of Cranial Nerves Slide 7.59 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.21

Spinal Nerves Slide 7.63 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs  Spinal nerves are formed by the combination of the ventral and dorsal roots of the spinal cord  Spinal nerves are named for the region from which they arise

Spinal Nerves Slide 7.64 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.22a

Examples of Nerve Distribution Slide 7.66 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.23

Autonomic Nervous System Slide 7.67 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The involuntary branch of the nervous system  Consists of only motor nerves  Divided into two divisions  Sympathetic division  Parasympathetic division

Anatomy of the Sympathetic Division Slide 7.70 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Originates from T 1 through L 2 vertebrae  Norepinephrine and epinephrine are neurotransmitters to the effector organs

Anatomy of the Parasympathetic Division Slide 7.72 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Originates from the brain stem and S 1 through S 4 vertebrae  Always uses acetylcholine as a neurotransmitter

Autonomic Functioning Slide 7.74a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sympathetic – “fight-or-flight”  Response to unusual stimulus  Takes over to increase activities  Remember as the “E” division = exercise, excitement, emergency, and embarrassment

Autonomic Functioning Slide 7.74b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Parasympathetic – housekeeping activites  Conserves energy  Maintains daily necessary body functions  Remember as the “D” division - digestion, defecation, and diuresis

Development Aspects of the Nervous System Slide 7.75b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  No more neurons are formed after birth, but growth and maturation continues for several years  The brain reaches maximum weight as a young adult (about 3 pounds)