Lecture Medical assisting: Administrative and clinical procedures with anatomy and physiology (4e) – Chapter 25

CHAPTER 25 The Nervous System © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-2 Learning Outcomes 25.1 Explain the difference between the central nervous system and the peripheral nervous system 25.2 Describe the functions of the nervous system 25.3 Describe the structure of a neuron 25.4 Describe the function of a nerve impulse and how a nerve impulse is created © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-3 Learning Outcomes (cont.) 25.5 Describe the structure and function of a synapse 25.6 Describe the function of the blood-brain barrier 25.7 Describe the structure and functions of meninges 25.8 Describe the structure and functions of the spinal cord © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-4 Learning Outcomes (cont.) 25.9 Describe the location and function of cerebrospinal fluid 25.10 Define reflex and list the parts of a reflex arc 25.11 List the major divisions of the brain and give the general functions of each 25.12 Explain the functions of the cranial and spinal nerves © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-5 Learning Outcomes (cont.) 25.13 Describe the differences between the somatic nervous system and autonomic nervous system 25.14 Explain the two divisions of the autonomic nervous system 25.15 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-6 Introduction • Highly complex system of two parts – Central nervous system (CNS) – Peripheral nervous system (PNS) • Controls all other organ systems and is important for maintaining balance within those systems Disorders Disorders are are numerous numerous and and often often difficult difficult to to diagnose diagnose and and treat treat © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-7 General Functions of the NS • CNS – Brain – Spinal cord • PNS – Peripheral nerves – Two sections • Somatic nervous system (SNS) – Skeletal or voluntary muscles • Autonomic nervous system (ANS) – Automatic functions © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-8 General Functions (cont.) • Three types of neurons – Afferent or sensory nerves • Sensory information from environment or inside body to CNS for interpretation – Efferent or motor nerves • Impulses from CNS to PNS to allow for movement or action – Interneurons • Interpretive neurons between afferent and efferent nerves in the CNS © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-9 Apply Your Knowledge Match the following: ANSWER: B Somatic nervous system _ A Motor nerves C Autonomic nervous system B Governs skeletal or voluntary _ muscles A Afferent nerves _ systems E C Governs respiratory and GI _ D Efferent nerves _ Interneurons D Go-betweens or interpreters E Sensory nerves © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-10 Neuron Structure • Functional cells of NS • Transmit electrochemical messages called nerve impulses to – Other neurons – Effectors (muscles or glands) © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-62 Common Diseases and Disorders (cont.) Disease/Disorder Description Brain tumors and cancers Abnormal growths Can be primary or secondary tumors Most common – gliomas Epilepsy and seizures Occurs as a result of bursts of electrical signals that disrupt normal brain functioning Guillain-Barré Syndrome Body’s immune system attacks the PNS © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-63 Common Diseases and Disorders (cont.) Disease/Disorder Description Headaches Tension Migraines Cluster Episodic or chronic With aura/without aura Form of migraines; occurs in groups Meningitis Inflammation of meninges Multiple sclerosis (MS) Chronic disease of CNS Myelin is destroyed © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-64 Common Diseases and Disorders (cont.) Disease/Disorder Description Neuralgias Disorders causing nerve pain Parkinson’s disease Progressive and degenerative motor system disorder Sciatica Damage to sciatic nerve Stroke Brain cells die because of an inadequate blood flow; “brain attack” © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-65 Apply Your Knowledge True or false: Bravo! ANSWER: T Alzheimer’s disease is a progressive degenerative disease _ of the brain F Epilepsy is due to degenerative neurons in the spinal cord _ and brain Due to a burst of electrical signals that disrupt brain function F Neuralgias are motor system disorders _ They are group of disorders referred to as nerve pain T Stroke occurs when brain cells die because of inadequate _ blood flow © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-66 In Summary 25.1 The central nervous system is composed of the brain and spinal cord The peripheral nervous system consists of the peripheral nerves located throughout the body The peripheral nervous system is further divided into two distinct systems: the somatic and autonomic nervous systems 25.2 There are three separate types of neurons to carry out the functions of the nervous system The afferent (sensory) nerves, the efferent (motor) nerves, and the interpretive interneurons that act as “interpreters” between the afferent and efferent nerves © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-67 In Summary (cont.) 25.3 All neurons are composed of a cell body, the shorter and more numerous dendrites that receive information for the cell body, and the longer axons that bring an impulse from the cell body to the dendrite of the next neuron 25.4 The function of a nerve impulse is the sending of information either from the CNS to the PNS or vice versa At rest, a neuron is said to be in a polarized state, and when it responds to stimuli, depolarization takes place Repolarization occurs after the electrical current (impulse) has passed © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-68 In Summary (cont.) 25.5 A synapse is the space between the axon of one neuron and the dendrite of the next At the end of each axon is the synaptic knob, which contains vesicles that produce neurotransmitters These are released by the synaptic bulb to allow impulse transmission to continue to the next neuron 25.6 The blood-brain barrier is a layer of tightly woven capillaries that protects the delicate tissues of the CNS This barrier prevents certain substances, such as various waste products and drugs, from easily crossing this barrier and entering the brain tissues © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-69 In Summary (cont.) 25.7 The meninges, a triple-layered membrane protecting the brain and spinal cord, are composed of the following layers: The tough outer layer is the dura mater The space between the cranium and the dura mater is called the epidural space Below the dura mater is the subdural space The middle layer is the arachnoid, and below it is the subarachnoid space, which contains cerebrospinal fluid (CSF) The innermost layer is the pia mater © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-70 In Summary (cont.) 25.8 The spinal cord is continuous with the brain and consists of 31 spinal segments: cervical sacral 12 thoracic coccygeal lumbar The basic function of the spinal cord is to carry sensory information from the body to the brain and motor information from the brain to the muscles and glands of the body © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-71 In Summary (cont.) 25.9 Cerebrospinal fluid (CSF) is located within the subarachnoid space of the brain and within the central canal of the spinal cord It cushions the brain and spinal cord 25.10 A reflex is a predictable automatic response to a stimulus A typical reflex flows as follows: Sensory receptors send information (impulse) to the interneurons, which in turn send the information on to the effectors of the motor neurons, producing a response © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-72 In Summary (cont.) 25.11 The cerebrum is the largest part of the brain and is divided into two hemispheres subdivided into four lobes: frontal, parietal, temporal and occipital The diencephalon contains the thalamus and hypothalamus The brain stem consists of three parts: the midbrain, pons, and medulla oblongata The cerebellum is the final area of the brain © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-73 In Summary (cont.) 25.12 Twelve cranial nerves carry sensory information: OlfactoryOptic Trochlear Facial Glossopharyngeal Oculomotor Trigeminal Vagus Accessory Abducens Vestibulocochlear Hypoglossal There are 31 pairs of spinal nerves, each except C1 innervating a dermatome Refer to Figure 25.8 for a map of the spinal nerves © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-74 In Summary (cont.) 25.13 The somatic nervous system connects the CNS to the skin and skeletal muscle (voluntary functions) The autonomic nervous system connects the CNS to the internal organs (involuntary functions) 25.14 The autonomic nervous system is divided into the sympathetic system, which prepares the body for “fight or flight” (stressful) situations, and the parasympathetic system, which is the body’s everyday “resting” system for normal situations © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-75 In Summary (cont.) 25.15 There are many and varied diseases and disorders related to the nervous system The signs, symptoms, and treatments of these diseases are as varied as the diseases themselves Many of the more common diseases are included in the Pathophysiology section at the end of this chapter © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25-76 End of Chapter 25 Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.” ~ Dr Ralph Gerard © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed [...].. .25- 11 Neuron Structure (cont.) • Neurons lose their ability to divide – If destroyed, not replaced • Neuralgia – Support cells for neurons that can divide – Astrocytes – anchor blood vessels to nerves – Microglia – act as phagocytes – Oligodendrocytes – assist with production of myelin sheath © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 12 Neuron Structure... rights reserv ed 25- 29 Brain • Four sections – Cerebrum – Diencephalon – Brain stem – Cerebellum © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 30 Cerebrum • • Largest section Two cerebral hemispheres – Connected by a thick bundle of nerve fibers called the corpus callosum – Longitudinal fissure between hemispheres • Sulci – grooves on surface • Gyri or convolutions – bumps of brain... rights reserv ed 25- 31 Cerebrum (cont.) • Lobes – Frontal • Motor areas for voluntary body movements Frontal Parietal – Parietal • Somatosensory – interprets sensations – Temporal • Auditory – interprets sounds – Occipital Temporal Occipital • Interprets what a person sees © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 32 Cerebrum (cont.) • Cortex – Outer layer – gray matter • Contains... 75% of all neurons – Inner layer – white matter – Functions • Ventricles – Interconnected cavities within the brain – Filled with CSF • Interpret sensory information • Initiate body movements • Stores memories and creates emotions © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 33 Diencephalon • Between the cerebral hemispheres superior to the brain stem • Thalamus – Relay station... Subarachnoid space • Between arachnoid mater and pia mater • Contains cerebrospinal fluid (CSF) • Cushions CNS © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 22 Spinal Cord • Slender structure continuous with the brain • Descends into the vertebral canal and ends around the level of the first or second lumbar vertebra • 31 spinal segments: – – – – – 8 cervical segments 12 thoracic segments... cord – Dura mater • Tough outer layer – Arachnoid mater • Middle layer (web-like) – Pia mater • Innermost and most delicate • Directly on top of brain and spinal cord • Holds blood vessels on the surface of these structures © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 21 Central Nervous System (cont.) – Epidural space • Above dura mater – Subdural space • Below dura mater – Subarachnoid... interpretation • Hypothalamus – Maintains homeostasis by regulating vital activities Brain © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 34 Brain Stem • • Connects the cerebrum to the spinal cord Midbrain – – • Just beneath diencephalon Controls both visual and auditory reflexes Pons – – – Rounded bulge on underside of brain stem Between midbrain and medulla oblongata Regulates... • Medulla oblongata – Inferior portion of brain stem – Directly connected to spinal cord – Controls many vital activities, such as heart rate, blood pressure, and breathing Brain © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 35 Cerebellum • Location – Inferior to the occipital lobes of the cerebrum – Posterior to the pons and medulla oblongata • Coordinates – Complex skeletal muscle... ed 25- 25 Spinal Cord (cont.) • White matter – Outer tissue – Contains myelinated axons – Divisions are called columns (funiculi) • Columns contain groups of axons called nerve tracts Spinal Cord/Nerve © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 27 Spinal Cord (cont.) • One function of the spinal cord is to carry sensory information to and from the brain • Ascending tracts – Carry... coccygeal segment © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 23 Spinal Cord (cont.) © 2011 T he McGraw -Hill Com panie s, Inc A ll rights reserv ed 25- 24 Spinal Cord (cont.) • Gray matter – Inner tissue with darker color – Contains neuron cell bodies and their dendrites – Divisions are called horns – Central canal runs down the entire length of the spinal cord through Spinal Cord/Nerve