Essentials of Human Anatomy & Physiology - Chapter 7 PDF

Essentials of Human Anatomy & Physiology Thirteenth Edition Global Edition Chapter 7 The Nervous System Lecture Presentation by...

Essentials of Human Anatomy & Physiology Thirteenth Edition Global Edition Chapter 7 The Nervous System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functions of the Nervous System 1. Sensory input—gathering information – Sensory receptors monitor changes, called stimuli, occurring inside and outside the body 2. Integration – Nervous system processes and interprets sensory input and decides whether action is needed 3. Motor output – A response, or effect, activates muscles or glands Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.1 The Nervous System’s Functions Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Concept Link 1 These three overlapping nervous system functions are very similar to a feedback loop (Chapter 1, p. 41). Recall that in a feedback loop, a receptor receives sensory input, which it sends to the brain (control center) for processing (integration); the brain then analyzes the information and determines the appropriate output, which leads to a motor response. Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Organization of the Nervous System Nervous system classifications – Structural classification is based on the structures of the nervous system ▪ Central nervous system ▪ Peripheral nervous system – Functional classification is based on the activities of the nervous system ▪ Sensory (afferent) division ▪ Motor (efferent) division Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.2 Organization of the Nervous System Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Structural Classification (1 of 2) Central nervous system (CNS) – Organs ▪ Brain ▪ Spinal cord – Function ▪ Integration; command center ▪ Interprets incoming sensory information ▪ Issues outgoing instructions Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Structural Classification (2 of 2) 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 Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Classification (1 of 2) Sensory (afferent) division – Nerve fibers that carry information to the central nervous system ▪ Somatic sensory (afferent) fibers carry information from the skin, skeletal muscles, and joints ▪ Visceral sensory (afferent) fibers carry information from visceral organs Motor (efferent) division – Nerve fibers that carry impulses away from the central nervous system organs to effector organs (muscles and glands) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Classification (2 of 2) Motor (efferent) division – Two subdivisions ▪ Somatic nervous system = voluntary – Consciously (voluntarily) controls skeletal muscles ▪ Autonomic nervous system = involuntary – Automatically controls smooth and cardiac muscles and glands – Further divided into the sympathetic and parasympathetic nervous systems Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Structure and Function Nervous tissue is composed of two types of cells – Neurons – Supporting cells collectively called neuroglia Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Support Cells (1 of 7) Support cells in the CNS are grouped together as neuroglia General functions – Support – Insulate – Protect neurons Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Support Cells (2 of 7) Nervous tissue is made up of two principal cell types – Supporting cells (called neuroglia, or glial cells, or glia) ▪ Resemble neurons ▪ Unable to conduct nerve impulses ▪ Never lose the ability to divide – Neurons Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Support Cells (3 of 7) CNS glial cells: astrocytes – Abundant, star-shaped cells – Brace and anchor neurons to blood capillaries – Determine permeability and exchanges between blood capillaries and neurons – Protect neurons from harmful substances in blood – Control the chemical environment of the brain Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.3a Support Cells (Neuroglia) of Nervous Tissue Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Support Cells (4 of 7) CNS glial cells: microglia – Spiderlike phagocytes – Monitor health of nearby neurons – Dispose of debris Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.3b Support Cells (Neuroglia) of Nervous Tissue Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Support Cells (5 of 7) CNS glial cells: ependymal cells – Line cavities of the brain and spinal cord – Cilia assist with circulation of cerebrospinal fluid Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.3c Support Cells (Neuroglia) of Nervous Tissue Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Support Cells (6 of 7) CNS glial cells: oligodendrocytes – Wrap around nerve fibers in the central nervous system – Produce myelin sheaths Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.3d Support Cells (Neuroglia) of Nervous Tissue Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Support Cells (7 of 7) PNS glial cells – Schwann cells ▪ Form myelin sheath around nerve fibers in the PNS – Satellite cells ▪ Protect and cushion neuron cell bodies Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.3e Support Cells (Neuroglia) of Nervous Tissue Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (1 of 30) Neurons = nerve cells – Cells specialized to transmit messages (nerve impulses) – Major regions of all neurons ▪ Cell body—nucleus and metabolic center of the cell ▪ Processes—fibers that extend from the cell body Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (2 of 30) Cell body is the metabolic center of the neuron – Nucleus with large nucleolus – Nissl bodies ▪ Rough endoplasmic reticulum – Neurofibrils ▪ Intermediate filaments that maintain cell shape Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.4a Structure of a Typical Motor Neuron Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.4b Structure of a Typical Motor Neuron Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (3 of 30) Processes (fibers) – 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 ▪ End in axon terminals, which contain vesicles with neurotransmitters ▪ Axon terminals are separated from the next neuron by a gap Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (4 of 30) Processes (fibers) – Synaptic cleft—gap between axon terminals and the next neuron – Synapse—functional junction between nerves where a nerve impulse is transmitted Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (5 of 30) Myelin sheaths – Myelin is a white, fatty material covering axons – Protects and insulates fibers – Speeds nerve impulse transmission Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (6 of 30) Myelin sheaths – Schwann cells—wrap axons in a jelly roll–like fashion (PNS) to form the myelin sheath ▪ Neurilemma—part of the Schwann cell external to the myelin sheath ▪ Nodes of Ranvier—gaps in myelin sheath along the axon – Oligodendrocytes—produce myelin sheaths around axons of the CNS ▪ Lack a neurilemma (plays a role in fiber regeneration) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.5 Relationship of Schwann Cells to Axons in the Peripheral Nervous System Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (7 of 30) Terminology – Nuclei—clusters of cell bodies in the CNS – Ganglia—collections of cell bodies outside the CNS in the PNS – 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—mostly unmyelinated fibers and cell bodies Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (8 of 30) Functional classification – Sensory (afferent) neurons ▪ Carry impulses from the sensory receptors to the CNS ▪ Receptors include: – Cutaneous sense organs in skin detect pain, temperature, touch, pressure – Proprioceptors in muscles and tendons detect stretch Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.6 Neurons Classified by Function (1 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.7a Types of Sensory Receptors Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.7b Types of Sensory Receptors Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.7c Types of Sensory Receptors Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.7d Types of Sensory Receptors Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.7e Types of Sensory Receptors Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (9 of 30) Functional classification – Motor (efferent) neurons ▪ Carry impulses from the central nervous system to viscera and/or muscles and glands – Interneurons (association neurons) ▪ Cell bodies located in the CNS ▪ Connect sensory and motor neurons Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.6 Neurons Classified by Function (2 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (10 of 30) Structural classification – 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 structural type Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.8a Classification of Neurons on the Basis of Structure Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (11 of 30) Structural classification – Bipolar neurons—one axon and one dendrite ▪ Located in special sense organs, such as nose and eye ▪ Rare in adults Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.8b Classification of Neurons on the Basis of Structure Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (12 of 30) Structural classification – Unipolar neurons—have a short single process leaving the cell body ▪ Sensory neurons found in PNS ganglia ▪ Conduct impulses both toward and away from the cell body Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.8c Classification of Neurons on the Basis of Structure Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (13 of 30) 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 Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (14 of 30) Electrical conditions of a resting neuron’s membrane – The plasma membrane at rest is inactive (polarized) – Fewer positive ions are inside the neuron’s plasma membrane than outside ▪ K  is the major positive ion inside the cell ▪ Na is the major positive ion outside the cell – The polarized membrane is more permeable to K  than to Na  – As long as the inside of the membrane is more negative (fewer positive ions) than the outside, the cell remains inactive Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.9 The Nerve Impulse (1 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (15 of 30) Action potential initiation and generation – A stimulus changes the permeability of the neuron’s membrane to sodium ions – Sodium channels now open, and sodium (Na+) diffuses into the neuron – The inward rush of sodium ions changes the polarity at that site and is called depolarization Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.9 The Nerve Impulse (2 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (16 of 30) Action potential initiation and generation (continued) – 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) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.9 The Nerve Impulse (3 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (17 of 30) 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 Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.9 The Nerve Impulse (4 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (18 of 30) Repolarization – Membrane permeability changes again—becoming impermeable to sodium ions and permeable to potassium ions – Potassium ions rapidly diffuse out of the neuron, repolarizing the membrane – Repolarization involves restoring the inside of the membrane to a negative charge and the outer surface to a positive charge Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.9 The Nerve Impulse (5 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (19 of 30) Repolarization – Initial conditions of sodium and potassium ions 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 – Until repolarization is complete, a neuron cannot conduct another nerve impulse Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.9 The Nerve Impulse (6 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (20 of 30) Transmission of the signal at synapses – Step 1: When the action potential reaches the axon terminal, the electrical charge opens calcium channels Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.10 How Neurons Communicate at Chemical Synapses (1 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (21 of 30) Transmission of the signal at synapses – Step 2: Calcium, in turn, causes the tiny vesicles containing the neurotransmitter chemical to fuse with the axonal membrane Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.10 How Neurons Communicate at Chemical Synapses (2 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (22 of 30) Transmission of the signal at synapses – Step 3: The entry of calcium into the axon terminal causes porelike openings to form, releasing the neurotransmitter into the synaptic cleft Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.10 How Neurons Communicate at Chemical Synapses (3 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (23 of 30) Transmission of the signal at synapses – Step 4: The neurotransmitter molecules diffuse across the synaptic cleft and bind to receptors on the membrane of the next neuron Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.10 How Neurons Communicate at Chemical Synapses (4 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (24 of 30) Transmission of the signal at synapses – Step 5: If enough neurotransmitter is released, a graded potential will be generated ▪ Eventually an action potential (nerve impulse) will occur in the neuron beyond the synapse Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.10 How Neurons Communicate at Chemical Synapses (5 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (25 of 30) Transmission of the signal at synapses – Step 6: The electrical changes prompted by neurotransmitter binding are brief – The neurotransmitter is quickly removed from the synapse either by reuptake or by enzymatic activity – Transmission of an impulse is electrochemical ▪ Transmission down neuron is electrical ▪ Transmission to next neuron is chemical Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.10 How Neurons Communicate at Chemical Synapses (6 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. BioFlix: How Synapses Work https://mediaplayer.pearsoncmg.com/assets/8ReRzSHzRzMAKz6fJ_q8NYX_wzmjadCv Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (26 of 30) Reflexes – Rapid, predictable, and involuntary responses to stimuli – Occur over neural pathways called reflex arcs – Two types of reflexes ▪ Somatic reflexes ▪ Autonomic reflexes Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11a Simple Reflex Arcs (1 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (27 of 30) Somatic reflexes – Reflexes that stimulate the skeletal muscles – Involuntary, although skeletal muscle is normally under voluntary control – 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 Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (28 of 30) Five elements of a reflex arc 1. Sensory receptor—reacts to a stimulus 2. Sensory neuron—carries message to the integration center 3. Integration center (CNS)—processes information and directs motor output 4. Motor neuron—carries message to an effector 5. Effector organ—is the muscle or gland to be stimulated Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11a Simple Reflex Arcs (2 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11a Simple Reflex Arcs (3 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11a Simple Reflex Arcs (4 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11a Simple Reflex Arcs (5 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11a Simple Reflex Arcs (6 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (29 of 30) Two-neuron reflex arcs – Simplest type – Example: patellar (knee-jerk) reflex Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11b Simple Reflex Arcs (1 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11b Simple Reflex Arcs (2 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11b Simple Reflex Arcs (3 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11b Simple Reflex Arcs (4 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11b Simple Reflex Arcs (5 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11b Simple Reflex Arcs (6 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Nervous Tissue: Neurons (30 of 30) Three-neuron reflex arcs – Consists of five elements: receptor, sensory neuron, interneuron, motor neuron, and effector – Example: flexor (withdrawal) reflex Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11c Simple Reflex Arcs (1 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11c Simple Reflex Arcs (2 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11c Simple Reflex Arcs (3 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11c Simple Reflex Arcs (4 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11c Simple Reflex Arcs (5 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.11c Simple Reflex Arcs (6 of 6) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Central Nervous System (CNS) Functional anatomy of the brain – Brain regions ▪ Cerebral hemispheres ▪ Diencephalon ▪ Brain stem ▪ Cerebellum Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (1 of 18) Cerebral hemispheres are paired (left and right) superior parts of the brain – Include more than half of the brain mass – The surface is made of ridges (gyri) and grooves (sulci) – Fissures are deeper grooves – Lobes are named for the cranial bones that lie over them Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (2 of 18) Three main regions of cerebral hemisphere 1. Cortex is superficial gray matter 2. White matter 3. Basal nuclei are deep pockets of gray matter Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.12a Development and Regions of the Human Brain Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.12b Development and Regions of the Human Brain (1 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.13ab Left Lateral View of the Brain Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.1 Functions of Major Brain Regions (1 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.1 Functions of Major Brain Regions (2 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (3 of 18) Cerebral cortex – Primary somatic sensory area ▪ Located in parietal lobe posterior to central sulcus ▪ Receives impulses from the body’s sensory receptors – Pain, temperature, light touch (except for special senses) ▪ Sensory homunculus is a spatial map ▪ Left side of the primary somatic sensory area receives impulses from right side (and vice versa) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.13c Left Lateral View of the Brain (1 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.14 Sensory and Motor Areas of the Cerebral Cortex (1 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (4 of 18) Cerebral areas involved in special senses – Visual area (occipital lobe) – Auditory area (temporal lobe) – Olfactory area (temporal lobe) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (5 of 18) Cerebral cortex – Primary motor area ▪ Located anterior to the central sulcus in the frontal lobe ▪ Allows us to consciously move skeletal muscles ▪ Motor neurons form pyramidal (corticospinal) tract, which descends to spinal cord ▪ Motor homunculus is a spatial map Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.13a Left Lateral View of the Brain (1 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.14 Sensory and Motor Areas of the Cerebral Cortex (2 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (6 of 18) Cerebral cortex – Broca’s area (motor speech area) ▪ Involved in our ability to speak ▪ Usually in left hemisphere at the base of the precentral gyrus – Other specialized areas ▪ Anterior association area (frontal lobe) ▪ Posterior association area (posterior cortex) ▪ Speech area (for sounding out words) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.13c Left Lateral View of the Brain (2 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (7 of 18) Cerebral white matter – Composed of fiber tracts deep to the gray matter ▪ Corpus callosum connects hemispheres ▪ Tracts, such as the corpus callosum, are known as commissures ▪ Association fiber tracts connect areas within a hemisphere ▪ Projection fiber tracts connect the cerebrum with lower CNS centers Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.13a Left Lateral View of the Brain (2 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.15 Frontal Section (Facing Posteriorly) of the Brain Showing Commissural, Association, and Projection Fibers Running Through the Cerebrum and the Lower CNS Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (8 of 18) Basal nuclei – “Islands” of gray matter buried deep within the white matter of the cerebrum – Regulate voluntary motor activities by modifying instructions sent to skeletal muscles by the primary motor cortex Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (9 of 18) Diencephalon (interbrain) – Sits on top of the brain stem – Enclosed by the cerebral hemispheres – Includes three structures 1. Thalamus 2. Hypothalamus 3. Epithalamus Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.12b Development and Regions of the Human Brain (2 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.16a Diencephalon and Brain Stem Structures (1 of 3) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.16b Diencephalon and Brain Stem Structures (1 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (10 of 18) Diencephalon: thalamus – Encloses the third ventricle – Relay station for sensory impulses passing upward to the cerebral cortex Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (11 of 18) Diencephalon: hypothalamus – Makes up the floor of the diencephalon – Important autonomic nervous system center ▪ Regulates body temperature, water balance, metabolism – Houses the limbic center for emotions – Regulates the nearby pituitary gland – Houses mammillary bodies ▪ Reflex centers for olfaction (smell) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (12 of 18) Diencephalon: epithalamus – Forms the roof of the third ventricle – Houses the pineal body (an endocrine gland) – Includes the choroid plexus—forms cerebrospinal fluid Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (13 of 18) Brain stem – Provides pathway for ascending and descending tracts – Produce programmed behaviors key for survival – Includes three structures 1. Midbrain 2. Pons 3. Medulla oblongata Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.16a Diencephalon and Brain Stem Structures (2 of 3) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (14 of 18) Brain stem: midbrain – Extends from the mammillary bodies to the pons inferiorly – Cerebral aqueduct (tiny canal) connects the third and fourth ventricles – Two bulging fiber tracts, cerebral peduncles, convey ascending and descending impulses – Four rounded protrusions, corpora quadrigemina, are visual and auditory reflex centers Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (15 of 18) Brain stem: pons – The rounded structure protruding just below the midbrain – Mostly composed of fiber tracts – Includes nuclei involved in the control of breathing Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (16 of 18) Brain stem: medulla oblongata – The most inferior part of the brain stem that merges into the spinal cord – Includes important fiber tracts – Contains important centers that control: ▪ Heart rate ▪ Blood pressure ▪ Breathing ▪ Swallowing ▪ Vomiting – Fourth ventricle lies posterior to pons and medulla Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (17 of 18) 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 Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.16b Diencephalon and Brain Stem Structures (2 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Functional Anatomy of the Brain (18 of 18) Cerebrum – Two hemispheres with convoluted surfaces – Outer cortex of gray matter and inner region of white matter – Controls balance – Provides precise timing for skeletal muscle activity and coordination of body movements – Fibers connect to the cerebellum from the inner ear, eye, proprioceptors of skeletal muscles and more Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.16a Diencephalon and Brain Stem Structures (3 of 3) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Protection of the Central Nervous System (1 of 6) In addition to bony protection of the brain and spinal cord, the central nervous system is also protected by: – Meninges – Cerebrospinal fluid (CSF) – Blood-brain barrier Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Protection of the Central Nervous System (2 of 6) Meninges – Dura mater ▪ Outermost leathery layer ▪ Double-layered external covering – Periosteal layer—attached to inner surface of the skull – Meningeal layer—outer covering of the brain ▪ Folds inward in several areas – Falx cerebri – Tentorium cerebelli Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Protection of the Central Nervous System (3 of 6) Meninges – Arachnoid layer ▪ Middle layer ▪ Weblike extensions span the subarachnoid space to attach it to the pia mater ▪ Subarachnoid space is filled with cerebrospinal fluid ▪ Arachnoid granulations protrude through the dura mater and absorb cerebrospinal fluid into venous blood – Pia mater ▪ Internal layer ▪ Clings to the surface of the brain and spinal cord Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.17a Meninges of the Brain Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.17b Meninges of the Brain Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Protection of the Central Nervous System (4 of 6) Cerebrospinal fluid – Similar to blood plasma in composition – Formed continually by the choroid plexuses ▪ Choroid plexuses—capillaries in the ventricles of the brain – CSF forms a watery cushion to protect the brain and spinal cord – Circulated in the arachnoid space, ventricles, and central canal of the spinal cord Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Protection of the Central Nervous System (5 of 6) Cerebrospinal fluid circulation 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 Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.18a Ventricles and Location of the Cerebrospinal Fluid Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.18b Ventricles and Location of the Cerebrospinal Fluid Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.18c Ventricles and Location of the Cerebrospinal Fluid Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Protection of the Central Nervous System (6 of 6) Blood-brain barrier – Includes the least permeable capillaries of the body – Allows water, glucose, and amino acids to pass through the capillary walls – Excludes many potentially harmful substances from entering the brain, such as wastes – Useless as a barrier against some substances Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Brain Dysfunctions (1 of 2) Traumatic brain injuries – Concussion ▪ Slight brain injury ▪ Typically little permanent brain damage occurs – Contusion ▪ Marked nervous tissue destruction occurs ▪ Coma may occur – Death may occur after head blows due to: ▪ Intracranial hemorrhage ▪ Cerebral edema Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Brain Dysfunctions (2 of 2) Cerebrovascular accident (CVA), or stroke – Results when blood circulation to a brain area is blocked and brain tissue 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) – Numbness, temporary paralysis, impaired speech Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Spinal Cord (1 of 3) 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 Protected by vertebrae and meninges 31 pairs of spinal nerves arise from the spinal cord – Cauda equina is a collection of spinal nerves at the inferior end Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.19 Anatomy of the Spinal Cord, Posterior View Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Spinal Cord (2 of 3) Gray matter of the spinal cord and spinal roots – Internal gray matter is mostly cell bodies – Posterior (dorsal) horns house interneurons ▪ Receive information from sensory neurons in the dorsal root; cell bodies housed in dorsal root ganglion – Ventral (anterior) horns house motor neurons of the somatic (voluntary) nervous system ▪ Send motor information out ventral root – Gray matter surrounds the central canal, which is filled with cerebrospinal fluid Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Spinal Cord (3 of 3) White matter of the spinal cord – Composed of myelinated fiber tracts – Three regions: dorsal, lateral, ventral columns – Sensory (afferent) tracts conduct impulses toward brain – Motor (efferent) tracts carry impulses from brain to skeletal muscles Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.20 Spinal Cord With Meninges (Three-Dimensional, Anterior View) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.21 Schematic of Ascending (Sensory) and Descending (Motor) Pathways Between the Brain and the Spinal Cord Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Peripheral Nervous System (PNS) PNS consists of nerves and ganglia outside the CNS Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Structure of a Nerve (1 of 2) Nerves are bundles of neuron fibers found outside the CNS Protective connective tissue coverings – Endoneurium is a connective tissue sheath that surrounds each fiber – Perineurium wraps groups of fibers bound into a fascicle – Epineurium binds groups of fascicles Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.22 Structure of a Nerve Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Concept Link 2 The terms for the connective tissue coverings of a nerve should seem familiar: We discussed similar structures in the muscle chapter (Figure 6.1, p. 201). Names of muscle structures include the root word mys, whereas the root word neuro tells you that the structure relates to a nerve. For example, the endomysium covers one individual muscle fiber, whereas the endoneurium covers one individual neuron fiber. Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Structure of a Nerve (2 of 2) Mixed nerves – Contain both sensory and motor fibers Sensory (afferent) nerves – Carry impulses toward the CNS Motor (efferent) nerves – Carry impulses away from the CNS Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Cranial Nerves 12 pairs of nerves serve mostly the head and neck Only the pair of vagus nerves extends to thoracic and abdominal cavities Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Cranial Nerves Mnemonic Device Oh – Olfactory Oh – Optic Oh – Oculomotor To – Trochlear Touch – Trigeminal And – Abducens Feel – Facial Very – Vestibulocochlear Good – Glossopharyngeal Velvet – Vagus At – Accessory Home – Hypoglossal Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.23 Distribution of Cranial Nerves Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.2 The Cranial Nerves (1 of 6) Name/number Origin/course Function Test I. Olfactory One. Fibers arise from Purely sensory; carries Subject is asked to sniff olfactory receptors in impulses for the sense and identify aromatic the nasal mucosa and of smell substances, such as oil synapse with the of cloves or vanilla olfactory bulbs (which, in turn, send fibers to the olfactory cortex) II. Optic Two. Fibers arise from the Purely sensory; carries Vision and visual field retina of the eye and impulses for vision are tested with an eye form the optic nerve. chart and by testing the The two optic nerves point at which the form the optic chiasma subject first sees an by partial crossover of object (finger) moving fibers; the fibers into the visual field; eye continue to the optic interior is viewed with cortex as the optic an ophthalmoscope tracts Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.2 The Cranial Nerves (2 of 6) Name/number Origin/course Function Test III. Oculomotor Three. Fibers run from the Supplies motor fibers to Pupils are examined for midbrain to the eye four of the six muscles size, shape, and size (superior, inferior, and equality; pupillary reflex medial rectus, and is tested with a penlight inferior oblique) that (pupils should constrict direct the eyeball; to when illuminated); eye the eyelid; and to the convergence is tested, internal eye muscles as is the ability to follow controlling lens shape moving objects and pupil size IV. Four. Trochlear Fibers run from the Supplies motor fibers Tested in common with midbrain to the eye for one external eye cranial nerve III for the muscle (superior ability to follow moving oblique) objects Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.2 The Cranial Nerves (3 of 6) Name/number Origin/course Function Test V. Trigeminal Five. Fibers emerge from the Conducts sensory Sensations of pain, pons and form three impulses from the skin touch, and temperature divisions that run to the of the face and mucosa are tested with a safety face of the nose and mouth; pin and hot and cold also contains motor objects; corneal reflex fibers that activate the tested with a wisp of chewing muscles cotton; motor branch tested by asking the subject to open mouth against resistance and move jaw from side to side VI. Six. Abducens Fibers leave the pons Supplies motor fibers to Tested in common with and run to the eye the lateral rectus cranial nerve III for the muscle, which rolls the ability to move each eye laterally eye laterally Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.2 The Cranial Nerves (4 of 6) Name/number Origin/course Function Test VII. Facial Seven. Fibers leave the pons Activates the muscles Anterior two-thirds of and run to the face of facial expression and tongue is tested for the lacrimal and ability to taste sweet, salivary glands; carries salty, sour, and bitter sensory impulses from substances; subject is the taste buds of asked to close eyes, anterior tongue smile, whistle, etc.; tearing of eyes is tested with ammonia fumes VIII. Vestibulocochlear Eight. Fibers run from the Purely sensory; Hearing is checked by equilibrium and hearing vestibular branch air and bone receptors of the inner transmits impulses for conduction, using a ear to the brain stem the sense of balance, tuning fork and cochlear branch transmits impulses for the sense of hearing Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.2 The Cranial Nerves (5 of 6) Name/number Origin/course Function Test IX. Glossopharyngeal Nine. Fibers emerge from the Supplies motor fibers to the Gag and swallowing medulla and run to the pharynx (throat) that reflexes are checked; throat promote swallowing and subject is asked to speak saliva production; carries and cough; posterior sensory impulses from tongue may be tested for taste buds of the posterior taste tongue and from pressure receptors of the carotid artery X. Vagus Ten. Fibers emerge from the Fibers carry sensory Tested in common with medulla and descend into impulses from and motor cranial nerve IX because nine the thorax and abdominal impulses to the pharynx, they both serve muscles of cavity larynx, and the abdominal the throat and thoracic viscera; most motor fibers are parasympathetic fibers that promote digestive activity and help regulate heart activity Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.2 The Cranial Nerves (6 of 6) Name/number Origin/course Function Test XI. Accessory Eleven. Fibers arise from the Mostly motor fibers that Sternocleidomastoid superior spinal cord activate the and trapezius muscles (C1 – C5 ) * and travel to C sub 1 to C sub 5, asterisk sternocleidomastoid are checked for muscles of the neck and trapezius muscles strength by asking the and back subject to rotate head and shrug shoulders against resistance XII. Hypoglossal Twelve. Fibers run from the Motor fibers control Subject is asked to medulla to the tongue tongue movements; stick out tongue, and sensory fibers carry any position impulses from the abnormalities are noted tongue *Until recently, it was thought that the accessory nerves also received a contribution from cranial rootlets, but it has now been determined that in almost all people, these cranial rootlets are instead part of the vagus nerves. This raises an interesting question: Should the accessory nerves still be considered cranial nerves? Some anatomists say yes because they pass through the cranium. Other anatomists say no because they don’t arise from the brain. Stay tuned! Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Spinal Nerves (1 of 3) Spinal nerves – 31 pairs – Formed by the joining of the ventral and dorsal roots of the spinal cord – Named for the region of the spinal cord from which they arise Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.24a Spinal Nerves Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Spinal Nerves (2 of 3) Spinal nerves divide soon after leaving the spinal cord into a dorsal ramus and a ventral ramus – 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 (T1 – T12 ) —form the intercostal nerves that supply muscles and skin of the ribs and trunk – Ventral rami (except T1 – T12 ) —form a complex of networks (plexus) for the anterior Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.24b Spinal Nerves Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Spinal Nerves (3 of 3) 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 1. Cervical 2. Brachial 3. Lumbar 4. Sacral Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.3 Spinal Nerve Plexuses (1 of 3) Origin (from ventral Important Result of damage to Plexus rami) nerves Body areas served plexus or its nerves C1 – C5 C sub 1 to C sub 5, asterisk Cervical Phrenic Diaphragm; skin and Respiratory paralysis (and muscles of shoulder and death if not treated neck promptly) C5 – C8 and T1 C sub 5 to C sub 8 and T sub 1 Brachial Axillary Deltoid muscle and skin of Paralysis and atrophy of shoulder; muscles and skin deltoid muscle of superior thorax Brachial C sub 5 to C sub 8 and T sub 1 Radial Triceps and extensor Wristdrop—inability to muscles of the forearm; extend hand at wrist skin of posterior upper limb Brachial C sub 5 to C sub 8 and T sub 1 Median Flexor muscles and some Decreased ability to flex and muscles of hand; skin abduct hand and flex and of lateral two-thirds of abduct thumb and index anterior hand and posterior finger—therefore, inability to of fingers 2 and 3 pick up small objects Brachial C sub 5 to C sub 8 and T sub 1 Musculocutane Flexor muscles of arm; skin Decreased ability to flex ous of lateral forearm forearm at elbow Brachial C sub 5 to C sub 8 and T sub 1 Ulnar Some flexor muscles of Clawhand—inability to forearm; wrist and many spread fingers apart hand muscles; skin of hand Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.25a Distribution of the Major Peripheral Nerves of the Upper and Lower Limbs Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.3 Spinal Nerve Plexuses (2 of 3) Origin (from ventral Result of damage to Plexus rami) Important nerves Body areas served plexus or its nerves L1 – L 4 L sub 1 to L sub 4 Lumbar Femoral (including Lower abdomen, Inability to extend leg lateral and anterior anterior and medial and flex hip; loss of cutaneous branches) thigh muscles (hip cutaneous sensation flexors and knee extensors), and skin of anteromedial leg and thigh Lumbar L sub 1 to L sub 4 Obturator Adductor muscles of Inability to adduct medial thigh and thigh small hip muscles; skin of medial thigh and hip joint Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.25b Distribution of the Major Peripheral Nerves of the Upper and Lower Limbs Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.3 Spinal Nerve Plexuses (3 of 3) Origin (from Body areas Result of damage to Plexus ventral rami) Important nerves served plexus or its nerves L 4 – L5 and S1 – S3 L sub 4 to L sub 5 and S sub 1 to S sub 3 Sacral Sciatic (largest nerve in body; Lower trunk and Inability to extend hip splits to common fibular and posterior surface of and flex knee; sciatica tibial nerves just above knee) thigh (hip extensors and knee flexors) Common fibular (superficial and deep branches) Lateral aspect of Footdrop—inability to leg and foot dorsiflex foot Tibial (including sural and plantar branches) Posterior aspect of Inability to plantar flex leg and foot and invert foot; shuffling gait Sacral L sub 4 to L sub 5 and S sub 1 to S sub 3 Superior and inferior gluteal Gluteus muscles of Inability to extend hip hip (maximus) or abduct and medially rotate thigh (medius) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.25c Distribution of the Major Peripheral Nerves of the Upper and Lower Limbs Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Autonomic Nervous System Motor subdivision of the PNS – Consists only of motor nerves – Controls the body automatically (and is also known as the involuntary nervous system) – Regulates cardiac and smooth muscles and glands – Two subdivisions ▪ Somatic nervous system ▪ Autonomic nervous system Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Somatic and Autonomic Nervous Systems Compared Somatic nervous system – Motor neuron cell bodies originate inside the CNS – Axons extends to skeletal muscles that are served Autonomic nervous system – Chain of two motor neurons ▪ Preganglionic neuron is in the brain or spinal cord ▪ Postganglionic neuron extends to the organ – Has two arms ▪ Sympathetic division ▪ Parasympathetic division Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.26 Comparison of the Somatic and Autonomic Nervous Systems Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Anatomy of the Parasympathetic Division Parasympathetic division is also known as the craniosacral division Preganglionic neurons originate in: – Cranial nerves III, VII, IX, and X – S2 through S 4 regions of the spinal cord Preganglionic neurons synapse with terminal ganglia; from there, postganglionic axons extend to organs that are served Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.27 Anatomy of the Autonomic Nervous System (1 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Anatomy of the Sympathetic Division (1 of 2) Sympathetic division is also known as the thoracolumbar division Preganglionic neurons originate from T1 through L 2 – Axons pass through a ramus communicans to enter a sympathetic trunk ganglion – Sympathetic trunk, or chain, lies near the spinal cord Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Anatomy of the Sympathetic Division (2 of 2) After synapsing at the ganglion, the axon may synapse with a second neuron at the same or different level Or, the preganglionic neuron may pass through the ganglion without synapsing and form part of the splanchnic nerves – Splanchnic nerves travel to the collateral ganglion – Collateral ganglia serve the abdominal and pelvic organs Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.27 Anatomy of the Autonomic Nervous System (2 of 2) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Figure 7.28 Sympathetic Pathways Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Autonomic Functioning (1 of 4) Body organs served by the autonomic nervous system receive fibers from both divisions – Exceptions: blood vessels, structures of the skin, some glands, and the adrenal medulla – These exceptions receive only sympathetic fibers Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Autonomic Functioning (2 of 4) When body divisions serve the same organ, they cause antagonistic effects due to different neurotransmitters – Parasympathetic (cholinergic) fibers release acetylcholine – Sympathetic postganglionic (adrenergic) fibers release norepinephrine – Preganglionic axons of both divisions release acetycholine Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Autonomic Functioning (3 of 4) Sympathetic—“fight or flight” division – Response to unusual stimulus when emotionally or physically stressed or threatened – Takes over to increase activities – Remember as the “E” division ▪ Exercise ▪ Excitement ▪ Emergency ▪ Embarrassment Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Autonomic Functioning (4 of 4) Parasympathetic—“housekeeping” activites – “Rest-and-digest” system – Conserves energy – Maintains daily necessary body functions – Remember as the “D” division ▪ Digestion ▪ Defecation ▪ Diuresis Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.4 Effects of the Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System (1 of 2) Target organ/system Parasympathetic effects Sympathetic effects Adipose tissue No effect Stimulates fat breakdown Adrenal medulla No effect Stimulates medulla cells to secrete epinephrine and norepinephrine Arrector pili muscles attached to No effect Stimulates; produces “goose bumps” hair follicles Blood vessels No effect on most blood vessels Constricts blood vessels in viscera and skin (dilates those in skeletal muscle and heart); increases blood pressure Cellular metabolism No effect Increases metabolic rate; increases blood sugar levels; stimulates fat breakdown Digestive system Increases smooth muscle mobility Decreases activity of digestive system (peristalsis) and amount of secretion and constricts digestive system by digestive system glands; relaxes sphincters (for example, anal sphincter) sphincters Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Table 7.4 Effects of the Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System (2 of 2) Target organ/system Parasympathetic effects Sympathetic effects Eye (ciliary muscle) Stimulates to increase bulging of lens Inhibits; decreases bulging of lens; for close vision prepares for distant vision Eye (iris) Stimulates constrictor muscles; Stimulates dilator muscles; dilates constricts pupils pupils Glands—salivary, lacrimal, gastric Stimulates; increases production of Inhibits; result is dry mouth and dry saliva, tears, and gastric juice eyes Heart Decreases rate; slows and steadies Increases rate and force of heartbeat Kidneys No effect Decreases urine output Liver No effect Causes glucose to be released to blood Lungs Constricts bronchioles Dilates bronchioles Penis Causes erection due to vasodilation Causes ejaculation (emission of semen) Sweat glands of skin No effect Stimulates to produce perspiration Urinary bladder/urethra Relaxes sphincters (allows voiding) Constricts sphincters (prevents voiding) Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Developmental Aspects of the Nervous System (1 of 5) The nervous system is formed during the first month of embryonic development Infections and other exposures can have harmful effects during pregnancy – German measles (rubella) – Smoking – Radiation – Drugs Oxygen deprivation destroys brain cells The hypothalamus is one of the last areas of the brain to develop Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Developmental Aspects of the Nervous System (2 of 5) Severe congenital brain diseases include: – Cerebral palsy – Anencephaly – Hydrocephalus – Spina bifida Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Developmental Aspects of the Nervous System (3 of 5) 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 Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Developmental Aspects of the Nervous System (4 of 5) Brain growth ends in young adulthood. Neurons die throughout life and are not replaced; thus, brain mass declines with age Orthostatic hypotension is low blood pressure due to changes in body position Healthy aged people maintain nearly optimal intellectual function Copyright © 2022 Pearson Education, Ltd. All Rights Reserved. Developmental Aspects of the Nervous System (5 of 5) Disease—particularly cardiovascular disease—is the major cause of declining mental function with age – Arteriosclerosis is decreased elasticity of blood vessels – Decline in oxygen leads to senility ▪ Forgetfulness, irritability, difficulty concentrating and thinking clearly, confusion Copyright © 2022 Pearson Education, Ltd. All Rights Reserved.