Nerve activates contraction

Nerve activates contraction

Chapter 7 The Nervous System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College 2015 Pearson Education, Inc. Functions of the Nervous System 1. Sensory inputgathering information To monitor changes occurring inside and outside the body Changes stimuli 2. Integration To process and interpret sensory input and decide whether action is needed

2015 Pearson Education, Inc. Functions of the Nervous System 3. Motor output A response to integrated stimuli The response activates muscles or glands 2015 Pearson Education, Inc. Figure 7.1 The nervous systems functions. Sensory input Sensory receptor Motor output Brain and spinal cord

Effector 2015 Pearson Education, Inc. 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 nervescarry impulses to and from the spinal cord Cranial nervescarry 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) Sense

organs Motor (efferent) Somatic (voluntary) Autonomic (involuntary) Skeletal muscles Cardiac and smooth muscle, glands

Parasympathetic 2015 Pearson Education, Inc. 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) Sense

organs Motor (efferent) Somatic (voluntary) Autonomic (involuntary) Skeletal muscles Cardiac and smooth muscle, glands

Parasympathetic 2015 Pearson Education, Inc. 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. Nervous Tissue: Support Cells CNS glial cells: astrocytes Abundant, star-shaped cells

Brace neurons Form barrier between capillaries and neurons Control the chemical environment of the brain 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.

2015 Pearson Education, Inc. Nervous Tissue: Support Cells CNS glial cells: microglia Spiderlike phagocytes Dispose of debris 2015 Pearson Education, Inc. Figure 7.3b Supporting (glial) cells of nervous tissue. Neuron Microglial cell (b) Microglial cells are phagocytes that defend CNS cells.

2015 Pearson Education, Inc. Nervous Tissue: Support Cells CNS glial cells: ependymal cells Line cavities of the brain and spinal cord Cilia assist with circulation of cerebrospinal fluid 2015 Pearson Education, Inc. 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. 2015 Pearson Education, Inc. Nervous Tissue: Support Cells CNS glial cells: oligodendrocytes Wrap around nerve fibers in the central nervous system Produce myelin sheaths 2015 Pearson Education, Inc. 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. 2015 Pearson Education, Inc. Nervous Tissue: Support Cells PNS glial cells Satellite cells Protect neuron cell bodies Schwann cells Form myelin sheath in the peripheral nervous system

2015 Pearson Education, Inc. 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. 2015 Pearson Education, Inc.

Nervous Tissue: Neurons Neurons nerve cells Cells specialized to transmit messages Major regions of neurons Cell bodynucleus and metabolic center of the cell Processesfibers that extend from the cell body 2015 Pearson Education, Inc. Nervous Tissue: Neurons Cell body Nissl bodies Specialized rough endoplasmic reticulum Neurofibrils Intermediate cytoskeleton Maintains cell shape

Nucleus with large nucleolus 2015 Pearson Education, Inc. Figure 7.4a Structure of a typical motor neuron. Mitochondrion Dendrite Cell body Nissl substance Axon hillock Axon Neurofibrils

Nucleus Collateral branch One Schwann cell Axon terminal (a) 2015 Pearson Education, Inc. Node of Ranvier Schwann cells, forming the myelin sheath on axon

Figure 7.4b Structure of a typical motor neuron. Neuron cell body Dendrite (b) 2015 Pearson Education, Inc. Nervous Tissue: Neurons Processes outside the cell body Dendritesconduct impulses toward the cell body Neurons may have hundreds of dendrites Axonsconduct 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. Mitochondrion Dendrite Cell body Nissl substance Axon hillock Axon Neurofibrils

Nucleus Collateral branch One Schwann cell Axon terminal (a) 2015 Pearson Education, Inc. Node of Ranvier Schwann cells, forming the myelin sheath on axon

Nervous Tissue: Neurons Axons End in axon terminals Axon terminals contain vesicles with neurotransmitters Axon terminals are separated from the next neuron by a gap Synaptic cleftgap between adjacent neurons Synapsejunction between nerves 2015 Pearson Education, Inc. Nervous Tissue: Neurons Myelin sheathwhitish, fatty material covering axons Schwann cellsproduce myelin sheaths in jelly roll

like fashion around axons (PNS) Nodes of Ranviergaps in myelin sheath along the axon Oligodendrocytesproduce myelin sheaths around axons of the CNS Myelin sheaths speed the nerve impulse transmission 2015 Pearson Education, Inc. Figure 7.5 Relationship of Schwann cells to axons in the peripheral nervous system. Schwann cell cytoplasm Axon

Schwann cell plasma membrane (a) Schwann cell nucleus (b) Neurilemma Myelin sheath (c) 2015 Pearson Education, Inc.

Neuron Cell Body Location Most neuron cell bodies are found in the central nervous system Gray mattercell bodies and unmyelinated fibers Nucleiclusters of cell bodies within the white matter of the central nervous system Gangliacollections of cell bodies outside the central nervous system 2015 Pearson Education, Inc. Neuron Cell Body Location Tractsbundles of nerve fibers in the CNS Nervesbundles of nerve fibers in the PNS White mattercollections of myelinated fibers (tracts)

Gray mattercollections 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 Proprioceptorsdetect stretch or tension 2015 Pearson Education, Inc. Figure 7.6 Neurons classified by function. Central process (axon)

Sensory Spinal cord Cell neuron (central nervous system) body Ganglion Dendrites Peripheral process (axon) Afferent transmission Interneuron (association neuron)

Peripheral nervous system Receptors Efferent transmission Motor neuron To effectors (muscles and glands) 2015 Pearson Education, Inc. Figure 7.7a Types of sensory receptors. (a) Free nerve endings (pain and temperature receptors) 2015 Pearson Education, Inc.

Figure 7.7b Types of sensory receptors. (b) Meissners corpuscle (touch receptor) 2015 Pearson Education, Inc. Figure 7.7c Types of sensory receptors. (c) Lamellar corpuscle (deep pressure receptor) 2015 Pearson Education, Inc. Figure 7.7d Types of sensory receptors. (d) Golgi tendon organ (proprioceptor)

2015 Pearson Education, Inc. Figure 7.7e Types of sensory receptors. (e) Muscle spindle (proprioceptor) 2015 Pearson Education, Inc. 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 Spinal cord Cell neuron (central nervous system) body Ganglion Dendrites Peripheral

process (axon) Afferent transmission Interneuron (association neuron) Peripheral nervous system Receptors Efferent transmission Motor neuron To effectors (muscles and glands)

2015 Pearson Education, Inc. Structural Classification of Neurons Structural classification is based on number of processes extending from the cell body Multipolar neuronsmany 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 Dendrites

(a) Multipolar neuron 2015 Pearson Education, Inc. Axon Structural Classification of Neurons Bipolar neuronsone axon and one dendrite Located in special sense organs, such as nose and eye Rare in adults 2015 Pearson Education, Inc. Figure 7.8b Classification of neurons on the basis of structure. Cell body

Dendrite (b) Bipolar neuron 2015 Pearson Education, Inc. Axon Structural Classification of Neurons Unipolar neuronshave a short single process leaving the cell body Sensory neurons found in PNS ganglia Conduct impulses both toward and away from the cell body 2015 Pearson Education, Inc. Figure 7.8c Classification of neurons on the basis of structure.

Dendrites Cell body Short single process Axon Peripheral process (c) Unipolar neuron 2015 Pearson Education, Inc. Central process

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+] [K+] 2015 Pearson Education, Inc. 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. Nerve Impulses Action potential initiation and generation A stimulus depolarizes the neurons 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. Figure 7.9 The nerve impulse. Na+

Na+ 2015 Pearson Education, Inc. Slide 3 2 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. 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. Figure 7.9 The nerve impulse. Na+ Na+ 2015 Pearson Education, Inc. Slide 4

3 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. 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.

Figure 7.9 The nerve impulse. Slide 5 4 Propagation of the action potential. Depolarization of the first membrane patch causes permeability changes in the adjacent membrane, and the events described in step 2 are repeated. Thus, the action potential propagates rapidly along the entire length of the membrane. 2015 Pearson Education, Inc. 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. Figure 7.9 The nerve impulse. K+ K+ 2015 Pearson Education, Inc. Slide 6

5 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. Nerve Impulses Repolarization Initial ionic conditions are restored using the sodiumpotassium 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. Figure 7.9 The nerve impulse.

Na+ Na+ Diffusion K+ Diffusion Cell exterior Cell interior 2015 Pearson Education, Inc. Slide 7 Na+

Na+ K+ K+ K+ K+ Na+ K+ pump 6 Initial ionic conditions restored. The ionic conditions of the resting state are restored later by the activity of the Plasma sodium-potassium pump. Three sodium ions are ejected for

membrane every two potassium ions carried back into the cell. 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 Dendrite Axon terminal 2015 Pearson Education, Inc. 1 Action potential arrives. Vesicles Synaptic cleft

Transmission of a Signal at Synapses Calcium, in turn, causes the tiny vesicles containing the neurotransmitter chemical to fuse with the axonal membrane 2015 Pearson Education, Inc. Figure 7.10 How neurons communicate at chemical synapses. Slide 3 2 Vesicle Transmitting neuron fuses with plasma membrane.

Synaptic cleft Ion channels Receiving neuron 2015 Pearson Education, Inc. Neurotransmitter molecules Transmission of a Signal at Synapses The entry of calcium into the axon terminal causes porelike openings to form, releasing the transmitter

2015 Pearson Education, Inc. Figure 7.10 How neurons communicate at chemical synapses. Slide 4 2 Vesicle Transmitting neuron fuses with plasma membrane. 3 Neurotrans- mitter is released into synaptic cleft.

Synaptic cleft Ion channels Receiving neuron 2015 Pearson Education, Inc. Neurotransmitter molecules Transmission of a Signal at Synapses The neurotransmitter molecules diffuse across the synapse and bind to receptors on the membrane of the next neuron

2015 Pearson Education, Inc. Figure 7.10 How neurons communicate at chemical synapses. Slide 5 2 Vesicle Transmitting neuron fuses with plasma membrane. 3 Neurotrans- mitter is released into

synaptic cleft. Synaptic cleft Ion channels Receiving neuron 2015 Pearson Education, Inc. 4 Neurotrans- mitter binds to receptor on receiving neurons

membrane. Neurotransmitter molecules Transmission of a Signal at Synapses If enough neurotransmitter is released, graded potential will be generated Eventually an action potential (nerve impulse) will occur in the neuron beyond the synapse 2015 Pearson Education, Inc. Figure 7.10 How neurons communicate at chemical synapses. Slide 6

Neurotransmitter Receptor Na+ 5 Ion channel opens. 2015 Pearson Education, Inc. Transmission of a Signal at Synapses 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. Figure 7.10 How neurons communicate at chemical synapses. Slide 7 Neurotransmitter is broken down and released. Na+ 6 Ion channel closes. 2015 Pearson Education, Inc.

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 2 1 Receptor 5 Effector (a) Five basic elements of reflex arc 2015 Pearson Education, Inc. Sensory neuron 4

Motor neuron Spinal cord (in cross section) Integration center Interneuron 3 The Reflex Arc Somatic 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: 1. Sensory receptorreacts to a stimulus 2. Sensory neuroncarries message to the integration center 3. Integration center (CNS)processes information and directs motor output 4. Motor neuroncarries message to an effector 5. Effector organis the muscle or gland to be stimulated

2015 Pearson Education, Inc. Figure 7.11a Simple reflex arcs. Slide 6 Stimulus at distal end of neuron Skin 2 1 Receptor 5

Effector (a) Five basic elements of reflex arc 2015 Pearson Education, Inc. Sensory neuron 4 Motor neuron Spinal cord (in cross section) Integration center Interneuron

3 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 2015 Pearson Education, Inc. 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. 1 Slide 1 Sensory receptor 2 Sensory (afferent) neuron 3 4

5 (c) Three-neuron reflex arc 2015 Pearson Education, Inc. Motor (efferent) neuron Effector organ Interneuron 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 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 2015 Pearson Education, Inc. 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 2015 Pearson Education, Inc. Table 7.1 Functions of Major Brain Regions (1 of 2) 2015 Pearson Education, Inc. Table 7.1 Functions of Major Brain Regions (2 of 2)

2015 Pearson Education, Inc. 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 1.Cortex (gray matter) 2.White matter 3.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 Parietal lobe Parieto-occipital sulcus (deep) Frontal lobe Lateral sulcus Occipital lobe Temporal lobe Cerebellum

Pons Cerebral cortex (gray matter) Gyrus Sulcus Fissure (a) (a deep sulcus) 2015 Pearson Education, Inc. Cerebral white matter Medulla oblongata Spinal

cord Regions of the Brain: Cerebrum Lobes of the cerebrum Fissures (deep grooves) divide the cerebrum into lobes Surface lobes of the cerebrum Frontal lobe Parietal lobe Occipital lobe Temporal lobe 2015 Pearson Education, Inc. Figure 7.13b Left lateral view of the brain. Parietal lobe

Left cerebral hemisphere Frontal lobe Occipital lobe Temporal lobe Cephalad Caudal (b) 2015 Pearson Education, Inc. Brain

stem Cerebellum Regions of the Brain: Cerebrum Specialized areas of the cerebrum Primary somatic sensory area Receives impulses from the bodys 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. Primary motor area Premotor area Speech/language (outlined by dashes) Posterior association area Brocas area (motor speech) Olfactory area 2015 Pearson Education, Inc.

Primary somatic sensory area Gustatory area (taste) Anterior association area Working memory and judgment Problem solving Language comprehension (c)

Central sulcus Visual area Auditory area Figure 7.14 Sensory and motor areas of the cerebral cortex. Posterior Tongue Swallowing 2015 Pearson Education, Inc. Primary motor

cortex (precentral gyrus) b Fi ng er s Sensory map in postcentral gyrus Th um

Toes Genitals Face Jaw Knee Foot b Lips Knee

Ne c Bro k w Eye Anterior Hip Trunk s er ng Fi Th

um lder Shou Arm ow Elb st i Wr nd Ha Motor map in precentral gyrus Sensory

Leg Hip Trunk Neck He Armad Elb o Fo w r Ha earm nd Motor Primary somatic sensory cortex

(postcentral gyrus) e Ey se o N e Fac s Lip Teeth Gums Jaw Tongue

Pharynx Intraabdominal Regions of the Brain: Cerebrum Cerebral areas involved in special senses Visual area (occipital lobe) Auditory area (temporal lobe) Olfactory area (temporal lobe) 2015 Pearson Education, Inc. Regions of the Brain: Cerebrum 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. Regions of the Brain: Cerebrum Brocas area Involved in our ability to speak Usually in left hemisphere Other specialized areas Anterior and posterior association areas Speech area 2015 Pearson Education, Inc.

Regions of the Brain: Cerebrum Layers of the cerebrum Gray matterouter layer in the cerebral cortex; composed mostly of neuron cell bodies White matterfiber 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 Parietal lobe Parieto-occipital sulcus (deep) Frontal lobe Lateral sulcus Occipital lobe Temporal lobe Cerebellum Pons Cerebral cortex (gray matter) Gyrus Sulcus

Fissure (a) (a deep sulcus) 2015 Pearson Education, Inc. Cerebral white matter Medulla oblongata Spinal cord Figure 7.15 Frontal section of the brain showing commissural, association, and projection fibers running through the cerebrum and the lower CNS. Longitudinal fissure

Superior Association fibers Lateral ventricle Commissural fibers (corpus callosum) Basal nuclei (basal ganglia) Corona radiata

Fornix Thalamus Internal capsule Third ventricle Pons Medulla oblongata 2015 Pearson Education, Inc. Projection fibers Regions of the Brain: Diencephalon

Sits on top of the brain stem Enclosed by the cerebral hemispheres Made of three parts: 1. Thalamus 2. Hypothalamus 3. Epithalamus 2015 Pearson Education, Inc. Figure 7.12b Development and regions of the human brain. Cerebral hemisphere Diencephalon Cerebellum Brain stem (b) Adult brain

2015 Pearson Education, Inc. 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) Pineal gland

(part of epithalamus) Anterior commissure Hypothalamus Corpora quadrigemina Optic chiasma Cerebral aqueduct Pituitary gland Cerebral peduncle Mammillary body Pons

Medulla oblongata Spinal cord (a) 2015 Pearson Education, Inc. Fourth ventricle Choroid plexus Cerebellum Midbrain Figure 7.16b Diencephalon and brain stem structures. Radiations to cerebral

cortex Visual impulses Reticular formation Ascending general sensory tracts (touch, pain, temperature) (b) 2015 Pearson Education, Inc. Auditory impulses Descending motor projections to spinal cord Regions of the Brain: Diencephalon

Thalamus Surrounds the third ventricle The relay station for sensory impulses Transfers impulses to the correct part of the cortex for localization and interpretation 2015 Pearson Education, Inc. Regions of the Brain: Diencephalon 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: Diencephalon Epithalamus Forms the roof of the third ventricle Houses the pineal body (an endocrine gland) Includes the choroid plexusforms cerebrospinal fluid 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. 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) Pineal gland (part of epithalamus) Anterior commissure Hypothalamus Corpora quadrigemina Optic chiasma Cerebral aqueduct Pituitary gland

Cerebral peduncle Mammillary body Pons Medulla oblongata Spinal cord (a) 2015 Pearson Education, Inc. Fourth ventricle Choroid plexus Cerebellum Midbrain Regions of the Brain: Brain Stem

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. Regions of the Brain: Brain Stem Pons The bulging center part of the brain stem Mostly composed of fiber tracts Includes nuclei involved in the control of breathing 2015 Pearson Education, Inc.

Regions of the Brain: Brain Stem 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. Regions of the Brain: Brain Stem 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 Visual impulses Reticular formation Ascending general sensory tracts (touch, pain, temperature)

(b) 2015 Pearson Education, Inc. Auditory impulses Descending motor projections to spinal cord 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.

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) Pineal gland (part of epithalamus)

Anterior commissure Hypothalamus Corpora quadrigemina Optic chiasma Cerebral aqueduct Pituitary gland Cerebral peduncle Mammillary body Pons Medulla oblongata Spinal cord

(a) 2015 Pearson Education, Inc. Fourth ventricle Choroid plexus Cerebellum Midbrain 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 Superior sagittal sinus Subdural space Subarachnoid space (a) 2015 Pearson Education, Inc.

Periosteal Meningeal Dura mater Arachnoid mater Pia mater Arachnoid villus Blood vessel Falx cerebri (in longitudinal fissure only) Meninges Dura mater

Tough outermost layer Double-layered external covering Periosteumattached to inner surface of the skull Meningeal layerouter covering of the brain Folds inward in several areas Falx cerebri Tentorium cerebelli 2015 Pearson Education, Inc. Meninges Arachnoid layer 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 Occipital lobe Tentorium cerebelli Cerebellum (b)

Arachnoid mater over medulla oblongata 2015 Pearson Education, Inc. Superior sagittal sinus Dura mater Transverse sinus Temporal bone Cerebrospinal Fluid (CSF) Similar to blood plasma composition

Formed by the choroid plexus Choroid plexusescapillaries 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 1. CSF is produced by the choroid plexus of each ventricle. 2. 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.

3. CSF flows through the subarachnoid space. 4. 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 2015 Pearson Education, Inc. Figure 7.18b Ventricles and location of the cerebrospinal fluid.

Lateral ventricle Anterior horn Posterior horn Interventricular foramen Third ventricle Inferior horn Cerebral aqueduct Fourth ventricle Median aperture

Lateral aperture Central canal (b) Left lateral view 2015 Pearson Education, Inc. Figure 7.18c Ventricles and location of the cerebrospinal fluid. 4 Superior sagittal sinus Arachnoid villus Subarachnoid space

Arachnoid mater Meningeal dura mater Choroid plexus Corpus callosum Interventricular foramen Third ventricle Periosteal dura mater 1 Right lateral ventricle (deep to cut) 3

Choroid plexus of fourth ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord (c) CSF circulation 1 CSF is produced by the 2 choroid plexus of each ventricle. 2 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. 3 CSF flows through the subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi. 2015 Pearson Education, Inc. Hydrocephalus in a Newborn

Hydrocephalus 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. 2015 Pearson Education, Inc. 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 Hemiplegiaone-sided paralysis Aphasiadamage 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.

Alzheimers 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 enlargement Cervical spinal nerves C8 Dura and

arachnoid mater Lumbar enlargement Thoracic spinal nerves T12 End of spinal cord Lumbar spinal nerves Cauda equina End of meningeal coverings

2015 Pearson Education, Inc. L5 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 materconduction 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.

Spinal Cord Anatomy Meninges cover the spinal cord Spinal nerves leave at the level of each vertebra Dorsal root Associated with the dorsal root gangliacollections 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 2015 Pearson Education, Inc. 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: 1. Optic 2. Olfactory 3. Vestibulocochlear 2015 Pearson Education, Inc.

Table 7.2 The Cranial Nerves (1 of 6) 2015 Pearson Education, Inc. Table 7.2 The Cranial Nerves (2 of 6) 2015 Pearson Education, Inc. Table 7.2 The Cranial Nerves (3 of 6) 2015 Pearson Education, Inc. Table 7.2 The Cranial Nerves (4 of 6) 2015 Pearson Education, Inc. Table 7.2 The Cranial Nerves (5 of 6)

2015 Pearson Education, Inc. Table 7.2 The Cranial Nerves (6 of 6) Cervical nerves 2015 Pearson Education, Inc. 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 XII Hypoglossal 2015 Pearson Education, Inc.

XI Accessory IX Glossopharyngeal 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. Figure 7.25a Spinal nerves. C1

2 3 Cervical nerves 4 5 6 7 8 1 T 2

Ventral rami form cervical plexus (C1 C5) Ventral rami form brachial plexus (C5 C8; T1) 3 4 Thoracic nerves 5 6 7 8

9 10 Lumbar nerves Sacral nerves 11 No plexus formed (intercostal nerves) (T1 T12) 12

L1 2 3 4 Ventral rami form lumbar plexus (L1 L4) 5 S1 2 (a) 2015 Pearson Education, Inc.

3 4 Ventral rami form sacral plexus (L4 L5; S1 S4) PNS: Anatomy of Spinal Nerves Spinal nerves divide soon after leaving the spinal cord Ramusbranch of a spinal nerve; contains both motor and sensory fibers Dorsal ramiserve the skin and muscles of the posterior trunk Ventral ramiform a complex of networks (plexus) for the anterior

2015 Pearson Education, Inc. Figure 7.25b Spinal nerves. Dorsal root Dorsal root ganglion Spinal cord Ventral root Spinal nerve (b)

2015 Pearson Education, Inc. Dorsal ramus Ventral ramus PNS: Spinal Nerve Plexuses Plexusnetworks 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: 1. 2. 3.

4. Cervical Brachial Lumbar Sacral 2015 Pearson Education, Inc. Table 7.3 Spinal Nerves Plexuses (1 of 3) 2015 Pearson Education, Inc. Figure 7.26a Distribution of the major peripheral nerves of the upper and lower limbs. Axillary nerve

Humerus Radial nerve Musculocutaneous nerve Ulna Radius Ulnar nerve Radial nerve (superficial branch) Median nerve 2015 Pearson Education, Inc. (a) The major nerves

of the upper limb Table 7.3 Spinal Nerves Plexuses (2 of 3) 2015 Pearson Education, Inc. 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 2015 Pearson Education, Inc. Table 7.3 Spinal Nerves Plexuses (3 of 3) 2015 Pearson Education, Inc. 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 2015 Pearson Education, Inc. (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: 1.Sympathetic division 2.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 7.28 Anatomy of the autonomic nervous system. Parasympathetic Sympathetic Eye Brain stem

Salivary glands Heart Skin Cranial Cervical Sympathetic ganglia T1 Pancreas Liver and

gallbladder Heart Stomach Thoracic Pancreas Liver and gallbladder L1 Adrenal gland Lumbar

Bladder Genitals 2015 Pearson Education, Inc. Salivary glands Lungs Lungs Stomach Eye Bladder

Sacral nerves (S2S4) Genitals PNS: Autonomic Functioning Sympatheticfight 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 Parasympathetichousekeeping 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) 2015 Pearson Education, Inc. Table 7.4 Effects of the Sympathetic Divisions of the Autonomic Nervous System (2 of 2)

2015 Pearson Education, Inc. 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. Developmental Aspects of the Nervous System

Severe congenital brain diseases include: Cerebral palsy Anencephaly Hydrocephalus Spina bifida 2015 Pearson Education, Inc. Developmental Aspects of the Nervous System 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 childs nervous system.

2015 Pearson Education, Inc. Developmental Aspects of the Nervous System 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. Diseaseparticularly cardiovascular diseaseis the major cause of declining mental function with age. 2015 Pearson Education, Inc.

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