© 2015 Pearson Education, Inc.

Functions of the Nervous System
Sensory input—gathering information To monitor changes occurring inside and outside the body Changes  stimuli Integration To process and interpret sensory input and decide whether action is needed © 2015 Pearson Education, Inc.

Functions of the Nervous System
Motor output A response to integrated stimuli The response activates muscles or glands © 2015 Pearson Education, Inc.

Figure 7.1 The nervous system’s functions.
Sensory input Integration Sensory receptor Motor output Brain and spinal cord Effector

Organization of the Nervous System
Nervous system is classified based on: Structures (structural classification) Activities (functional classification) © 2015 Pearson Education, Inc.

Structural Classification of the Nervous System
Central nervous system (CNS) Organs Brain Spinal cord Function Integration; command center Interpret incoming sensory information Issues outgoing instructions © 2015 Pearson Education, Inc.

Structural Classification of the Nervous System
Peripheral nervous system (PNS) Nerves extending from the brain and spinal cord Spinal nerves—carry impulses to and from the spinal cord Cranial nerves—carry impulses to and from the brain Functions Serve as communication lines among sensory organs, the brain and spinal cord, and glands or muscles © 2015 Pearson Education, Inc.

Figure 7.2 Organization of the nervous system.
Central Nervous System (brain and spinal cord) Peripheral Nervous System (cranial and spinal nerves) Sensory (afferent) Motor (efferent) Sense organs Somatic (voluntary) Autonomic (involuntary) Skeletal muscles Cardiac and smooth muscle, glands Parasympathetic Sympathetic

Functional Classification of the Peripheral Nervous System
Sensory (afferent) division Nerve fibers that carry information to the central nervous system Somatic sensory fibers carry information from the skin, skeletal muscles, and joints Visceral sensory fibers carry information from visceral organs Motor (efferent) division Nerve fibers that carry impulses away from the central nervous system organs © 2015 Pearson Education, Inc.

Figure 7.2 Organization of the nervous system.
Central Nervous System (brain and spinal cord) Peripheral Nervous System (cranial and spinal nerves) Sensory (afferent) Motor (efferent) Sense organs Somatic (voluntary) Autonomic (involuntary) Skeletal muscles Cardiac and smooth muscle, glands Parasympathetic Sympathetic

Functional Classification of the Peripheral Nervous System
Motor (efferent) division (continued) Two subdivisions Somatic nervous system  voluntary Consciously controls skeletal muscles Autonomic nervous system  involuntary Automatically controls smooth and cardiac muscles and glands Further divided into the sympathetic and parasympathetic nervous systems © 2015 Pearson Education, Inc.

Nervous Tissue: Support Cells
Support cells in the CNS are grouped together as neuroglia General functions Support Insulate Protect neurons © 2015 Pearson Education, Inc.

Figure 7.3a Supporting (glial) cells of nervous tissue.
Capillary Neuron Astrocyte (a) Astrocytes are the most abundant and versatile neuroglia.

Figure 7.3b Supporting (glial) cells of nervous tissue.
Neuron Microglial cell (b) Microglial cells are phagocytes that defend CNS cells.

Figure 7.3c Supporting (glial) cells of nervous tissue.
Fluid-filled cavity Ependymal cells Brain or spinal cord tissue (c) Ependymal cells line cerebrospinal fluid-filled cavities.

Figure 7.3d Supporting (glial) cells of nervous tissue.
Myelin sheath Process of oligodendrocyte Nerve fibers (d) Oligodendrocytes have processes that form myelin sheaths around CNS nerve fibers.

Figure 7.3e Supporting (glial) cells of nervous tissue.
Satellite cells Cell body of neuron Schwann cells (forming myelin sheath) Nerve fiber (e) Satellite cells and Schwann cells (which form myelin) surround neurons in the PNS.

Nervous Tissue: Neurons
Neurons  nerve cells Cells specialized to transmit messages Major regions of neurons Cell body—nucleus and metabolic center of the cell Processes—fibers that extend from the cell body © 2015 Pearson Education, Inc.

Figure 7.4a Structure of a typical motor neuron.
Dendrite Mitochondrion Cell body Nissl substance Axon hillock Axon Collateral branch Neurofibrils Nucleus One Schwann cell Node of Ranvier Axon terminal Schwann cells, forming the myelin sheath on axon (a)

Figure 7.4b Structure of a typical motor neuron.
Neuron cell body Dendrite (b)

Processes outside the cell body Dendrites—conduct impulses toward the cell body Neurons may have hundreds of dendrites Axons—conduct impulses away from the cell body Neurons have only one axon arising from the cell body at the axon hillock © 2015 Pearson Education, Inc.

Figure 7.4a Structure of a typical motor neuron.
Dendrite Mitochondrion Cell body Nissl substance Axon hillock Axon Collateral branch Neurofibrils Nucleus One Schwann cell Node of Ranvier Axon terminal Schwann cells, forming the myelin sheath on axon (a)

Axons End in axon terminals Axon terminals contain vesicles with neurotransmitters Axon terminals are separated from the next neuron by a gap Synaptic cleft—gap between adjacent neurons Synapse—junction between nerves © 2015 Pearson Education, Inc.

Myelin sheath—whitish, fatty material covering axons Schwann cells—produce myelin sheaths in jelly roll– like fashion around axons (PNS) Nodes of Ranvier—gaps in myelin sheath along the axon Oligodendrocytes—produce myelin sheaths around axons of the CNS Myelin sheaths speed the nerve impulse transmission © 2015 Pearson Education, Inc.

Schwann cell cytoplasm
Figure 7.5 Relationship of Schwann cells to axons in the peripheral nervous system. Schwann cell cytoplasm Schwann cell plasma membrane Axon Schwann cell nucleus (a) (b) Neurilemma Myelin sheath (c)

Neuron Cell Body Location
Most neuron cell bodies are found in the central nervous system Gray matter—cell bodies and unmyelinated fibers Nuclei—clusters of cell bodies within the white matter of the central nervous system Ganglia—collections of cell bodies outside the central nervous system © 2015 Pearson Education, Inc.

Neuron Cell Body Location
Tracts—bundles of nerve fibers in the CNS Nerves—bundles of nerve fibers in the PNS White matter—collections of myelinated fibers (tracts) Gray matter—collections of mostly unmyelinated fibers and cell bodies © 2015 Pearson Education, Inc.

Functional Classification of Neurons
Sensory (afferent) neurons Carry impulses from the sensory receptors to the CNS Cutaneous sense organs Proprioceptors—detect stretch or tension © 2015 Pearson Education, Inc.

Figure 7.6 Neurons classified by function.
Central process (axon) Sensory neuron Spinal cord (central nervous system) Cell body Ganglion Dendrites Peripheral process (axon) Afferent transmission Interneuron (association neuron) Peripheral nervous system Receptors Efferent transmission Motor neuron To effectors (muscles and glands)

Figure 7.7a Types of sensory receptors.
(a) Free nerve endings (pain and temperature receptors)

Figure 7.7b Types of sensory receptors.
(b) Meissner’s corpuscle (touch receptor)

Figure 7.7c Types of sensory receptors.
(c) Lamellar corpuscle (deep pressure receptor)

Figure 7.7d Types of sensory receptors.
(d) Golgi tendon organ (proprioceptor)

Figure 7.7e Types of sensory receptors.
(e) Muscle spindle (proprioceptor)

Functional Classification of Neurons
Motor (efferent) neurons Carry impulses from the central nervous system to viscera, muscles, or glands Interneurons (association neurons) Found in neural pathways in the central nervous system Connect sensory and motor neurons © 2015 Pearson Education, Inc.

Figure 7.6 Neurons classified by function.
Central process (axon) Sensory neuron Spinal cord (central nervous system) Cell body Ganglion Dendrites Peripheral process (axon) Afferent transmission Interneuron (association neuron) Peripheral nervous system Receptors Efferent transmission Motor neuron To effectors (muscles and glands)

Structural Classification of Neurons
Structural classification is based on number of processes extending from the cell body Multipolar neurons—many extensions from the cell body All motor and interneurons are multipolar Most common structure © 2015 Pearson Education, Inc.

Figure 7.8a Classification of neurons on the basis of structure.
Cell body Axon Dendrites (a) Multipolar neuron

Figure 7.8b Classification of neurons on the basis of structure.
Cell body Dendrite Axon (b) Bipolar neuron

Figure 7.8c Classification of neurons on the basis of structure.
Dendrites Cell body Short single process Axon Peripheral process Central process (c) Unipolar neuron

Functional Properties of Neurons
Irritability Ability to respond to a stimulus and convert it to a nerve impulse Conductivity Ability to transmit the impulse to other neurons, muscles, or glands © 2015 Pearson Education, Inc.

Nerve Impulses Resting neuron The plasma membrane at rest is polarized
As long as inside is more negative than outside, the cell stays at rest Fewer positive ions are inside the cell than outside the cell K is the major positive ion inside the cell Na is the major positive ion outside the cell © 2015 Pearson Education, Inc.

Figure 7.9 The nerve impulse.
Slide 2 [Na+] 1 Resting membrane is polarized. In the resting state, the external face of the membrane is slightly positive; its internal face is slightly negative. The chief extracellular ion is sodium (Na+), whereas the chief intracellular ion is potassium (K+). The membrane is relatively impermeable to both ions. [K+]

Nerve Impulses Action potential initiation and generation
A stimulus depolarizes the neuron’s membrane The membrane is now permeable to sodium as sodium channels open A depolarized membrane allows sodium (Na) to flow inside the membrane © 2015 Pearson Education, Inc.

Slide 3 Na+ Stimulus initiates local depolarization. A Stimulus changes the permeability of a local “patch” of the membrane, and sodium ions diffuse rapidly into the cell. This changes the polarity of the membrane (the inside becomes more positive; the outside becomes more negative) at that site. 2 Na+

Nerve Impulses Action potential initiation and generation
A stimulus leads to the movement of ions, which initiates an action potential in the neuron A graded potential (localized depolarization) exists where the inside of the membrane is more positive and the outside is less positive If the stimulus is strong enough and sodium influx great enough, local depolarization activates the neuron to conduct an action potential (nerve impulse) © 2015 Pearson Education, Inc.

Slide 4 Na+ Depolarization and generation of an action potential. If the stimulus is strong enough, depolarization causes membrane polarity to be completely reversed and an action potential is initiated. 3 Na+

Nerve Impulses Propagation of the action potential
If enough sodium enters the cell, the action potential (nerve impulse) starts and is propagated over the entire axon All-or-none response means the nerve impulse either is propagated or is not Fibers with myelin sheaths conduct nerve impulses more quickly © 2015 Pearson Education, Inc.

Slide 5 Propagation of the action potential. Depolarization of the first membrane patch causes permeability changes in the adjacent membrane, and the events described in step are repeated. Thus, the action potential propagates rapidly along the entire length of the membrane. 4 2

Nerve Impulses Repolarization
Potassium ions rush out of the neuron after sodium ions rush in, repolarizing the membrane Repolarization involves restoring the inside of the membrane to a negative charge and the outer surface to a positive charge Until repolarization is complete, a neuron cannot conduct another nerve impulse © 2015 Pearson Education, Inc.

Slide 6 K+ Repolarization. Potassium ions diffuse out of the cell as the membrane permeability changes again, restoring the negative charge on the inside of the membrane and the positive charge on the outside surface. Repolarization occurs in the same direction as depolarization. 5 K+

Nerve Impulses Repolarization
Initial ionic conditions are restored using the sodium- potassium pump This pump, using ATP, restores the original configuration Three sodium ions are ejected from the cell while two potassium ions are returned to the cell © 2015 Pearson Education, Inc.

Slide 7 Cell exterior Na+ Na+ Na+ – K+ pump Na+ 6 Initial ionic conditions restored. The ionic conditions of the resting state are restored later by the activity of the sodium-potassium pump. Three sodium ions are ejected for every two potassium ions carried back into the cell. K+ K+ Diffusion Na+ Diffusion K+ Plasma membrane Cell interior K+ K+

Transmission of a Signal at Synapses
When the action potential reaches the axon terminal, the electrical charge opens calcium channels © 2015 Pearson Education, Inc.

Figure 7.10 How neurons communicate at chemical synapses.
Slide 2 Axon of transmitting neuron Receiving neuron 1 Action potential arrives. Dendrite Vesicles Axon terminal Synaptic cleft

Slide 3 2 Transmitting neuron Vesicle fuses with plasma membrane. Synaptic cleft Ion channels Neurotransmitter molecules Receiving neuron

Slide 4 2 Transmitting neuron Vesicle fuses with plasma membrane. 3 Neurotrans- mitter is released into synaptic cleft. Synaptic cleft Ion channels Neurotransmitter molecules Receiving neuron

Slide 5 2 Transmitting neuron Vesicle fuses with plasma membrane. 4 Neurotrans- mitter binds to receptor on receiving neuron’s membrane. 3 Neurotrans- mitter is released into synaptic cleft. Synaptic cleft Ion channels Neurotransmitter molecules Receiving neuron

Slide 6 Neurotransmitter Receptor Na+ 5 Ion channel opens.

The electrical changes prompted by neurotransmitter binding are brief The neurotransmitter is quickly removed from the synapse by either: Reuptake Enzymatic activity Transmission of an impulse is electrochemical Transmission down neuron is electrical Transmission to next neuron is chemical © 2015 Pearson Education, Inc.

Slide 7 Neurotransmitter is broken down and released. Na+ 6 Ion channel closes.

The Reflex Arc Reflexes are:
Rapid Predictable Involuntary responses to a stimulus Reflexes occur over neural pathways called reflex arcs © 2015 Pearson Education, Inc.

Figure 7.11a Simple reflex arcs.
Stimulus at distal end of neuron Skin Spinal cord (in cross section) 2 Sensory neuron Integration center 3 1 Receptor Interneuron 5 Effector 4 Motor neuron (a) Five basic elements of reflex arc

The Reflex Arc Somatic reflexes Autonomic reflexes
Reflexes that stimulate the skeletal muscles Example: pulling your hand away from a hot object Autonomic reflexes Regulate the activity of smooth muscles, the heart, and glands Example: regulation of smooth muscles, heart and blood pressure, glands, digestive system © 2015 Pearson Education, Inc.

The Reflex Arc Five elements of a reflex:
Sensory receptor—reacts to a stimulus Sensory neuron—carries message to the integration center Integration center (CNS)—processes information and directs motor output Motor neuron—carries message to an effector Effector organ—is the muscle or gland to be stimulated © 2015 Pearson Education, Inc.

Slide 2 Stimulus at distal end of neuron Skin 1 Receptor (a) Five basic elements of reflex arc

Slide 3 Stimulus at distal end of neuron Skin Spinal cord (in cross section) 2 Sensory neuron 1 Receptor Interneuron (a) Five basic elements of reflex arc

Slide 4 Stimulus at distal end of neuron Skin Spinal cord (in cross section) 2 Sensory neuron Integration center 3 1 Receptor Interneuron (a) Five basic elements of reflex arc

Slide 5 Stimulus at distal end of neuron Skin Spinal cord (in cross section) 2 Sensory neuron Integration center 3 1 Receptor Interneuron 4 Motor neuron (a) Five basic elements of reflex arc

Slide 6 Stimulus at distal end of neuron Skin Spinal cord (in cross section) 2 Sensory neuron Integration center 3 1 Receptor Interneuron 5 Effector 4 Motor neuron (a) Five basic elements of reflex arc

Two-Neuron Reflex Arc Two-neuron reflex arcs Simplest type
Example: patellar (knee-jerk) reflex © 2015 Pearson Education, Inc.

Figure 7.11b Simple reflex arcs.
Slide 1 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron 3 4 Motor (efferent) neuron 5 Effector organ (b) Two neuron reflex arc

Slide 2 1 Sensory (stretch) receptor (b) Two neuron reflex arc

Slide 3 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron (b) Two neuron reflex arc

Slide 4 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron 3 (b) Two neuron reflex arc

Slide 5 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron 3 4 Motor (efferent) neuron (b) Two neuron reflex arc

Slide 6 1 Sensory (stretch) receptor 2 Sensory (afferent) neuron 3 4 Motor (efferent) neuron 5 Effector organ (b) Two neuron reflex arc

Three-Neuron Reflex Arc
Three-neuron reflex arcs Consists of five elements: receptor, sensory neuron, interneuron, motor neuron, and effector Example: flexor (withdrawal) reflex © 2015 Pearson Education, Inc.

Figure 7.11c Simple reflex arcs.
Slide 1 1 Sensory receptor 2 Sensory (afferent) neuron 3 Interneuron 4 Motor (efferent) neuron 5 Effector organ (c) Three-neuron reflex arc

Slide 2 1 Sensory receptor (c) Three-neuron reflex arc

Slide 3 1 Sensory receptor 2 Sensory (afferent) neuron (c) Three-neuron reflex arc

Slide 4 1 Sensory receptor 2 Sensory (afferent) neuron 3 Interneuron (c) Three-neuron reflex arc

Slide 5 1 Sensory receptor 2 Sensory (afferent) neuron 3 Interneuron 4 Motor (efferent) neuron (c) Three-neuron reflex arc

Slide 6 1 Sensory receptor 2 Sensory (afferent) neuron 3 Interneuron 4 Motor (efferent) neuron 5 Effector organ (c) Three-neuron reflex arc

Central Nervous System (CNS)
CNS develops from the embryonic neural tube The neural tube becomes the brain and spinal cord The opening of the neural tube becomes the ventricles Four chambers within the brain Filled with cerebrospinal fluid © 2015 Pearson Education, Inc.

Figure 7.12a Development and regions of the human brain.
Cerebral hemisphere Outline of diencephalon Midbrain Cerebellum Brain stem (a) 13 weeks

Figure 7.18a Ventricles and location of the cerebrospinal fluid.
Lateral ventricle Anterior horn Septum pellucidum Interventricular foramen Inferior horn Third ventricle Lateral aperture Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view

Regions of the Brain Cerebral hemispheres (cerebrum) Diencephalon
Brain stem Cerebellum © 2015 Pearson Education, Inc.

Figure 7.12b Development and regions of the human brain.
Cerebral hemisphere Diencephalon Cerebellum Brain stem (b) Adult brain

Table 7.1 Functions of Major Brain Regions (1 of 2)

Table 7.1 Functions of Major Brain Regions (2 of 2)

Regions of the Brain: Cerebrum
Cerebral hemispheres are paired (left & right) superior parts of the brain Includes more than half of the brain mass The surface is made of ridges (gyri) and grooves (sulci) Three main regions of cerebral hemisphere Cortex (gray matter) White matter Basal nuclei (deep pockets of gray matter) © 2015 Pearson Education, Inc.

Figure 7.13a Left lateral view of the brain.
Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Parieto-occipital sulcus (deep) Lateral sulcus Occipital lobe Temporal lobe Cerebellum Pons Medulla oblongata Cerebral cortex (gray matter) Spinal cord Gyrus Sulcus Cerebral white matter Fissure (a deep sulcus) (a)

Figure 7.13b Left lateral view of the brain.
Parietal lobe Left cerebral hemisphere Frontal lobe Occipital lobe Temporal lobe Cephalad Cerebellum Caudal Brain stem (b)

Specialized areas of the cerebrum Primary somatic sensory area Receives impulses from the body’s sensory receptors Pain, temperature, light touch Located in parietal lobe posterior to central sulcus Sensory homunculus is a spatial map Left side of the primary somatic sensory area receives impulses from right side (and vice versa) © 2015 Pearson Education, Inc.

Figure 7.13c Left lateral view of the brain.
Central sulcus Primary motor area Primary somatic sensory area Premotor area Anterior association area Gustatory area (taste) Working memory and judgment Speech/language (outlined by dashes) Posterior association area Problem solving Language comprehension Visual area Broca’s area (motor speech) Olfactory area Auditory area (c)

Figure 7.14 Sensory and motor areas of the cerebral cortex.
Posterior Motor Sensory Anterior Motor map in precentral gyrus Sensory map in postcentral gyrus Shoulder Hip Trunk Neck Head Arm Forearm Trunk Leg Hand Wrist Elbow Arm Hip Knee Elbow Hand Fingers Fingers Knee Thumb Thumb Neck Foot Eye Brow Nose Eye Toes Face Lips Genitals Face Primary motor cortex (precentral gyrus) Primary somatic sensory cortex (postcentral gyrus) Teeth Lips Gums Jaw Jaw Tongue Pharynx Tongue Intra- abdominal Swallowing

Specialized areas of the cerebrum Primary motor area Sends impulses to skeletal muscles Located in frontal lobe Motor neurons form corticospinal (pyramidal) tract, which descends to spinal cord Motor homunculus is a spatial map © 2015 Pearson Education, Inc.

Figure 7.14 Sensory and motor areas of the cerebral cortex.
Posterior Motor Sensory Anterior Motor map in precentral gyrus Sensory map in postcentral gyrus Shoulder Hip Trunk Neck Head Arm Forearm Trunk Leg Hand Wrist Elbow Arm Hip Knee Elbow Hand Fingers Fingers Knee Thumb Thumb Neck Foot Eye Brow Nose Eye Toes Face Lips Genitals Face Primary motor cortex (precentral gyrus) Primary somatic sensory cortex (postcentral gyrus) Teeth Lips Gums Jaw Jaw Tongue Pharynx Tongue Intra- abdominal Swallowing

Layers of the cerebrum Gray matter—outer layer in the cerebral cortex; composed mostly of neuron cell bodies White matter—fiber tracts deep to the gray matter Corpus callosum connects hemispheres Basal nuclei (ganglia)—islands of gray matter buried within the white matter © 2015 Pearson Education, Inc.

Figure 7.13a Left lateral view of the brain.
Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Parieto-occipital sulcus (deep) Lateral sulcus Occipital lobe Temporal lobe Cerebellum Pons Medulla oblongata Cerebral cortex (gray matter) Spinal cord Gyrus Sulcus Cerebral white matter Fissure (a deep sulcus) (a)

Commissural fibers (corpus callosum) Lateral ventricle
Figure 7.15 Frontal section of the brain showing commissural, association, and projection fibers running through the cerebrum and the lower CNS. Longitudinal fissure Association fibers Superior Commissural fibers (corpus callosum) Lateral ventricle Corona radiata Basal nuclei (basal ganglia) Fornix Internal capsule Thalamus Third ventricle Projection fibers Pons Medulla oblongata

Regions of the Brain: Diencephalon
Sits on top of the brain stem Enclosed by the cerebral hemispheres Made of three parts: Thalamus Hypothalamus Epithalamus © 2015 Pearson Education, Inc.

Figure 7.12b Development and regions of the human brain.
Cerebral hemisphere Diencephalon Cerebellum Brain stem (b) Adult brain

Figure 7.16a Diencephalon and brain stem structures.
Cerebral hemisphere Corpus callosum Third ventricle Choroid plexus of third ventricle Occipital lobe of cerebral hemisphere Thalamus (encloses third ventricle) Anterior commissure Pineal gland (part of epithalamus) Hypothalamus Corpora quadrigemina Optic chiasma Cerebral aqueduct Midbrain Pituitary gland Cerebral peduncle Mammillary body Fourth ventricle Pons Choroid plexus Medulla oblongata Cerebellum Spinal cord (a)

Figure 7.16b Diencephalon and brain stem structures.
Radiations to cerebral cortex Auditory impulses Visual impulses Descending motor projections to spinal cord Reticular formation Ascending general sensory tracts (touch, pain, temperature) (b)

Hypothalamus Under the thalamus Important autonomic nervous system center Helps regulate body temperature Controls water balance Regulates metabolism Houses the limbic center for emotions Regulates the nearby pituitary gland Houses mammillary bodies for olfaction (smell) © 2015 Pearson Education, Inc.

Regions of the Brain: Brain Stem
Attaches to the spinal cord Parts of the brain stem Midbrain Pons Medulla oblongata © 2015 Pearson Education, Inc.

Midbrain Composed mostly of tracts of nerve fibers Two bulging fiber tracts, cerebral peduncles, convey ascending and descending impulses Four rounded protrusions, corpora quadrigemina, visual and auditory reflex centers © 2015 Pearson Education, Inc.

Medulla oblongata The lowest part of the brain stem Merges into the spinal cord Includes important fiber tracts Contains important control centers Heart rate control Blood pressure regulation Breathing Swallowing Vomiting © 2015 Pearson Education, Inc.

Reticular formation Diffuse mass of gray matter along the brain stem Involved in motor control of visceral organs Reticular activating system (RAS) Plays a role in awake/sleep cycles and consciousness Filter for incoming sensory information © 2015 Pearson Education, Inc.

Figure 7.16b Diencephalon and brain stem structures.
Radiations to cerebral cortex Auditory impulses Visual impulses Descending motor projections to spinal cord Reticular formation Ascending general sensory tracts (touch, pain, temperature) (b)

Regions of the Brain: Cerebellum
Two hemispheres with convoluted surfaces Controls balance and equilibrium Provides precise timing for skeletal muscle activity and coordination of body movements © 2015 Pearson Education, Inc.

Protection of the Central Nervous System
Scalp and skin Skull and vertebral column Meninges Cerebrospinal fluid (CSF) Blood-brain barrier © 2015 Pearson Education, Inc.

Figure 7.17a Meninges of the brain.
Skin of scalp Periosteum Bone of skull Periosteal Dura mater Meningeal Superior sagittal sinus Arachnoid mater Subdural space Pia mater Arachnoid villus Subarachnoid space Blood vessel Falx cerebri (in longitudinal fissure only) (a)

Meninges Dura mater Tough outermost layer
Double-layered external covering Periosteum—attached to inner surface of the skull Meningeal layer—outer covering of the brain Folds inward in several areas Falx cerebri Tentorium cerebelli © 2015 Pearson Education, Inc.

Meninges Arachnoid layer Pia mater Middle layer
Weblike extensions span the subarachnoid space Arachnoid villi reabsorb cerebrospinal fluid Pia mater Internal layer Clings to the surface of the brain © 2015 Pearson Education, Inc.

Figure 7.17b Meninges of the brain.
Skull Scalp Superior sagittal sinus Occipital lobe Dura mater Tentorium cerebelli Transverse sinus Cerebellum Temporal bone Arachnoid mater over medulla oblongata (b)

Cerebrospinal Fluid (CSF)
Similar to blood plasma composition Formed by the choroid plexus Choroid plexuses–capillaries in the ventricles of the brain Forms a watery cushion to protect the brain Circulated in arachnoid space, ventricles, and central canal of the spinal cord © 2015 Pearson Education, Inc.

Cerebrospinal Fluid (CSF) Pathway of Flow
CSF is produced by the choroid plexus of each ventricle. CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. CSF flows through the subarachnoid space. CSF is absorbed into the dural venous sinuses via the arachnoid villi. © 2015 Pearson Education, Inc.

Figure 7.18a Ventricles and location of the cerebrospinal fluid.
Lateral ventricle Anterior horn Septum pellucidum Interventricular foramen Inferior horn Third ventricle Lateral aperture Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view

Figure 7.18b Ventricles and location of the cerebrospinal fluid.
Lateral ventricle Anterior horn Posterior horn Interventricular foramen Inferior horn Third ventricle Median aperture Cerebral aqueduct Fourth ventricle Lateral aperture Central canal (b) Left lateral view

Figure 7.18c Ventricles and location of the cerebrospinal fluid.
4 Superior sagittal sinus Arachnoid villus Choroid plexus Subarachnoid space Arachnoid mater Corpus callosum Meningeal dura mater Periosteal dura mater 1 Interventricular foramen Right lateral ventricle (deep to cut) Third ventricle 3 Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture CSF is produced by the choroid plexus of each ventricle. 1 Fourth ventricle 2 Median aperture CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. 2 Central canal of spinal cord (c) CSF circulation CSF flows through the subarachnoid space. 3 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi.

Hydrocephalus in a Newborn
CSF accumulates and exerts pressure on the brain if not allowed to drain Possible in an infant because the skull bones have not yet fused In adults, this situation results in brain damage © 2015 Pearson Education, Inc.

Figure 7.19 Hydrocephalus in a newborn.

Blood-Brain Barrier Includes the least permeable capillaries of the body Excludes many potentially harmful substances Useless as a barrier against some substances Fats and fat-soluble molecules Respiratory gases Alcohol Nicotine Anesthesia © 2015 Pearson Education, Inc.

Blood-Brain Barrier Water-soluble items that can travel through barrier: Water Glucose Essential amino acids Items prevented from passing through: Metabolic wastes Most drugs Nonessential amino acids Potassium ions © 2015 Pearson Education, Inc.

Traumatic Brain Injuries
Concussion Slight brain injury No permanent brain damage Contusion Nervous tissue destruction occurs Nervous tissue does not regenerate Cerebral edema Swelling from the inflammatory response May compress and kill brain tissue © 2015 Pearson Education, Inc.

Cerebrovascular Accident (CVA), or Stroke
Results from a ruptured blood vessel supplying a region of the brain Brain tissue supplied with oxygen from that blood source dies Loss of some functions or death may result Hemiplegia—one-sided paralysis Aphasia—damage to speech center in left hemisphere Transient ischemic attack (TIA)—temporary brain ischemia (restriction of blood flow) Warning signs for more serious CVAs © 2015 Pearson Education, Inc.

Alzheimer’s Disease Progressive degenerative brain disease
Mostly seen in the elderly, but may begin in middle age Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons Victims experience memory loss, irritability, confusion, and ultimately, hallucinations and death © 2015 Pearson Education, Inc.

Spinal Cord Extends from the foramen magnum of the skull to the first or second lumbar vertebra Provides a two-way conduction pathway to and from the brain 31 pairs of spinal nerves arise from the spinal cord Ends around vertebra L1 or L2 Cauda equina is a collection of spinal nerves at the inferior end © 2015 Pearson Education, Inc.

Figure 7.20 Anatomy of the spinal cord, posterior view.
Cervical spinal nerves Cervical enlargement C8 Dura and arachnoid mater Thoracic spinal nerves Lumbar enlargement T12 End of spinal cord Lumbar spinal nerves Cauda equina L5 End of meningeal coverings S1 Sacral spinal nerves S5

Spinal Cord Anatomy Internal gray matter is mostly cell bodies
Dorsal (posterior) horns house interneurons Receive information from sensory neurons in the dorsal root Anterior (ventral) horns house motor neurons of the somatic (voluntary) nervous system Send information out ventral root Gray matter surrounds the central canal, which is filled with cerebrospinal fluid © 2015 Pearson Education, Inc.

Spinal Cord Anatomy Exterior white mater—conduction tracts
Dorsal, lateral, ventral columns Sensory (afferent) tracts conduct impulses toward brain Motor (efferent) tracts carry impulses from brain to skeletal muscles © 2015 Pearson Education, Inc.

Figure 7.21 Spinal cord with meninges (three-dimensional view).
White matter Dorsal (posterior) horn of gray matter Dorsal root ganglion Central canal Lateral horn of gray matter Spinal nerve Ventral (anterior) horn of gray matter Dorsal root of spinal nerve Ventral root of spinal nerve Pia mater Arachnoid mater Dura mater

Interneuron carrying sensory information to cerebral cortex
Figure 7.22 Schematic of ascending (sensory) and descending (motor) pathways between the brain and the spinal cord. Interneuron carrying sensory information to cerebral cortex Integration (processing and interpretation of sensory input) occurs Cerebral cortex (gray matter) Interneuron carrying response to motor neurons White matter Thalamus Cerebrum Interneuron carrying response to motor neuron Brain stem Cell body of sensory neuron in sensory ganglion Interneuron carrying sensory information to cerebral cortex Nerve Skin Sensory receptors Cervical spinal cord Muscle White matter Gray matter Motor output Interneuron Motor neuron cell body

Spinal Cord Anatomy Meninges cover the spinal cord
Spinal nerves leave at the level of each vertebra Dorsal root Associated with the dorsal root ganglia—collections of cell bodies outside the central nervous system Ventral root Contains axons © 2015 Pearson Education, Inc.

Peripheral Nervous System (PNS)
PNS consists of nerves and ganglia outside the central nervous system Nerve  bundle of neuron fibers Neuron fibers are bundled by connective tissue © 2015 Pearson Education, Inc.

PNS: Structure of a Nerve
Endoneurium surrounds each fiber Groups of fibers are bound into fascicles by perineurium Fascicles are bound together by epineurium © 2015 Pearson Education, Inc.

Figure 7.23 Structure of a nerve.
Axon Myelin sheath Endoneurium Perineurium Epineurium Fascicle Blood vessels

PNS: Classification of Nerves
Mixed nerves Both sensory and motor fibers Sensory (afferent) nerves Carry impulses toward the CNS Motor (efferent) nerves Carry impulses away from the CNS © 2015 Pearson Education, Inc.

PNS: Cranial Nerves 12 pairs of nerves that mostly serve the head and neck Only the pair of vagus nerves extends to thoracic and abdominal cavities Most are mixed nerves, but three are sensory only: Optic Olfactory Vestibulocochlear © 2015 Pearson Education, Inc.

PNS: Cranial Nerves Mnemonic Device
Oh – Olfactory Oh – Optic Oh – Oculomotor To – Trochlear Touch – Trigeminal And – Abducens Feel – Facial Very – Vestibulocochlear Green – Glossopharyngeal Vegetables – Vagus A – Accessory H – Hypoglossal © 2015 Pearson Education, Inc.

Table 7.2 The Cranial Nerves (1 of 6)

Cervical nerves

Figure 7.24 Distribution of cranial nerves.
III Oculomotor IV Trochlear VI Abducens I Olfactory V Trigeminal V Trigeminal II Optic VII Facial Vestibular branch Cochlear branch VIII Vestibulocochlear X Vagus IX Glossopharyngeal XII Hypoglossal XI Accessory

PNS: Spinal Nerves There is a pair of spinal nerves at the level of each vertebra, for a total of 31 pairs Formed by the combination of the ventral and dorsal roots of the spinal cord Named for the region from which they arise © 2015 Pearson Education, Inc.

Ventral rami form cervical plexus (C1 – C5) Cervical nerves 4 5 6 7
Figure 7.25a Spinal nerves. C1 2 3 Ventral rami form cervical plexus (C1 – C5) Cervical nerves 4 5 6 7 Ventral rami form brachial plexus (C5 – C8; T1) 8 T1 2 3 4 5 Thoracic nerves 6 7 No plexus formed (intercostal nerves) (T1 – T12) 8 9 10 Lumbar nerves 11 12 Sacral nerves L1 2 3 Ventral rami form lumbar plexus (L1 – L4) 4 5 S1 Ventral rami form sacral plexus (L4 – L5; S1 – S4) 2 3 4 (a)

PNS: Anatomy of Spinal Nerves
Spinal nerves divide soon after leaving the spinal cord Ramus—branch of a spinal nerve; contains both motor and sensory fibers Dorsal rami—serve the skin and muscles of the posterior trunk Ventral rami—form a complex of networks (plexus) for the anterior © 2015 Pearson Education, Inc.

Dorsal root Dorsal ramus Dorsal root ganglion Spinal cord
Figure 7.25b Spinal nerves. Dorsal root Dorsal ramus Dorsal root ganglion Spinal cord Ventral ramus Ventral root Spinal nerve (b)

PNS: Spinal Nerve Plexuses
Plexus–networks of nerves serving motor and sensory needs of the limbs Form from ventral rami of spinal nerves in the cervical, lumbar, and sacral regions Four plexuses: Cervical Brachial Lumbar Sacral © 2015 Pearson Education, Inc.

Table 7.3 Spinal Nerves Plexuses (1 of 3)

Musculo- cutaneous nerve
Figure 7.26a Distribution of the major peripheral nerves of the upper and lower limbs. Axillary nerve Humerus Radial nerve Musculo- cutaneous nerve Ulna Radius Ulnar nerve Radial nerve (superficial branch) Median nerve (a) The major nerves of the upper limb

Lateral femoral cutaneous
Figure 7.26b Distribution of the major peripheral nerves of the upper and lower limbs. Femoral Lateral femoral cutaneous Obturator Anterior femoral cutaneous Saphenous (b) Lumbar plexus, anterior view

Posterior femoral cutaneous
Figure 7.26c Distribution of the major peripheral nerves of the upper and lower limbs. Superior gluteal Inferior gluteal Sciatic Posterior femoral cutaneous Common fibular Tibial Sural (cut) Deep fibular Superficial fibular Plantar branches (c) Sacral plexus, posterior view

PNS: Autonomic Nervous System
Motor subdivision of the PNS Consists only of motor nerves Also known as the involuntary nervous system Regulates activities of cardiac and smooth muscles and glands Two subdivisions: Sympathetic division Parasympathetic division © 2015 Pearson Education, Inc.

PNS: Differences Between Somatic and Autonomic Nervous Systems
Somatic Nervous System Autonomic Nervous System Nerves One-neuron system; it originates in the CNS, and axons extend to the skeletal muscles served Two-neuron system consisting of preganglionic and postganglionic neurons Effector organ Skeletal muscle Smooth muscle, cardiac muscle, glands Subdivisions None Sympathetic and parasympathetic Neurotransmitter Acetylcholine Acetylcholine, epinephrine, norepinephrine © 2015 Pearson Education, Inc.

Figure 7.27 Comparison of the somatic and autonomic nervous systems.
Central nervous system Peripheral nervous system Effector organs Acetylcholine Somatic nervous system Skeletal muscle Acetylcholine Norepinephrine Smooth muscle (e.g., in stomach) Sympathetic division Ganglion Acetylcholine Epinephrine and norepinephrine Autonomic nervous system Blood vessel Glands Acetylcholine Para- sympathetic division Cardiac muscle Ganglion KEY: Preganglionic axons (sympathetic) Postganglionic axons (sympathetic) Myelination Preganglionic axons (parasympathetic) Postganglionic axons (parasympathetic)

PNS: Anatomy of the Parasympathetic Division
Preganglionic neurons originate from the craniosacral regions: The cranial nerves III, VII, IX, and X S2 through S4 regions of the spinal cord Because it is the site of preganglionic neuron origination, the parasympathetic division is also known as the craniosacral division Terminal ganglia are at the effector organs Neurotransmitter: acetylcholine © 2015 Pearson Education, Inc.

Figure 7.28 Anatomy of the autonomic nervous system.
Parasympathetic Sympathetic Eye Eye Brain stem Salivary glands Skin Cranial Sympathetic ganglia Salivary glands Heart Cervical Lungs Lungs T1 Heart Stomach Thoracic Stomach Pancreas Liver and gall- bladder Pancreas L1 Liver and gall- bladder Adrenal gland Lumbar Bladder Bladder Sacral nerves (S2–S4) Genitals Genitals

PNS: Anatomy of the Sympathetic Division
Preganglionic neurons originate from T1 through L2 Ganglia are at the sympathetic trunk (near the spinal cord) Short preganglionic neuron and long postganglionic neuron transmit impulse from CNS to the effector Neurotransmitters: norepinephrine and epinephrine (effector organs) © 2015 Pearson Education, Inc.

Figure 7.28 Anatomy of the autonomic nervous system.
Parasympathetic Sympathetic Eye Eye Brain stem Salivary glands Skin Cranial Sympathetic ganglia Salivary glands Heart Cervical Lungs Lungs T1 Heart Stomach Thoracic Stomach Pancreas Liver and gall- bladder Pancreas L1 Liver and gall- bladder Adrenal gland Lumbar Bladder Bladder Sacral nerves (S2–S4) Genitals Genitals

Figure 7.29 Sympathetic pathways.
Lateral horn of gray matter Dorsal ramus of spinal nerve Dorsal root Ventral ramus of spinal nerve Sympathetic trunk (a) To effector: blood vessels, arrector pili muscles, and sweat glands of the skin Spinal nerve (c) (b) Ventral root Gray ramus communicans Sympathetic trunk ganglion Splanchnic nerve White ramus communicans Collateral ganglion (such as the celiac) Visceral effector organ (such as small intestine)

PNS: Autonomic Functioning
Sympathetic—“fight or flight” division Response to unusual stimulus Takes over to increase activities Remember as the “E” division: Exercise Excitement Emergency Embarrassment © 2015 Pearson Education, Inc.

PNS: Autonomic Functioning
Parasympathetic—“housekeeping” activites Conserves energy Maintains daily necessary body functions Remember as the “D” division Digestion Defecation Diuresis © 2015 Pearson Education, Inc.

Table 7.4 Effects of the Sympathetic Divisions of the Autonomic Nervous System (1 of 2)

Table 7.4 Effects of the Sympathetic Divisions of the Autonomic Nervous System (2 of 2)

Developmental Aspects of the Nervous System
The nervous system is formed during the first month of embryonic development Any maternal infection can have extremely harmful effects Oxygen deprivation destroys brain cells The hypothalamus is one of the last areas of the brain to develop © 2015 Pearson Education, Inc.

Premature babies have trouble regulating body temperature because the hypothalamus is one of the last brain areas to mature prenatally. Development of motor control indicates the progressive myelination and maturation of a child’s nervous system. © 2015 Pearson Education, Inc.

Brain growth ends in young adulthood. Neurons die throughout life and are not replaced; thus, brain mass declines with age. Healthy aged people maintain nearly optimal intellectual function. Disease—particularly cardiovascular disease—is the major cause of declining mental function with age. © 2015 Pearson Education, Inc.

© 2015 Pearson Education, Inc.

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