The learning objectives for this chapter include: Explain the difference between the central nervous system and the peripheral nervous system, describe the functions of the nervous system, describe the structure of a neuron, describe the function of a nerve impulse and how a nerve impulse is created,...
CHAPTER 30 The Nervous System 30-2 Learning Outcomes (cont.) 30.1 Describe the general functions of the nervous system 30.2 Summarize the structure of a neuron 30.3 Explain the function of nerve impulses and the role of synapses in their transmission 30.4 Describe the structures and functions of the central nervous system 30-3 Learning Outcomes (cont.) 30.5 Compare the structures and functions of the somatic and autonomic nervous systems in the peripheral nervous system 30.6 Recognize common tests that are performed to determine neurologic disorders 30.7 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the nervous system 30-4 Introduction • Highly complex system • Controls and helps to maintain balance in all other organ systems Disorders are numerous and often difficult to diagnose and treat 30-5 General Functions of the Nervous System • Central Nervous System (CNS) – Brain – Spinal cord • Peripheral Nervous System (PNS) – Peripheral nerves – Somatic nervous system (SNS) – Autonomic nervous system (ANS) 30-6 General Functions of the Nervous System (cont.) • Afferent nerves ~ sensory information • Efferent nerves ~ impulses that allow for movement or action • Interneurons – interpreters between afferent and efferent nerves 30-7 Apply Your Knowledge Match the following: ANSWER: B Somatic nervous system _ A Motor nerves C Autonomic nervous system B Governs skeletal or voluntary _ muscles E Afferent nerves _ systems A C Governs respiratory and GI _ D Efferent nerves _ Interneurons D Go-betweens or interpreters E Sensory nerves 30-8 Neuron Structure • Functional cells of NS • Transmit nerve impulses to – Other neurons – Effectors • Cannot divide • Neuroglia – Support cells for neurons – Astrocytes – Microglia – Oligodendrocytes 30-9 Neuron Structure (cont.) • Neurons – Cell body • Nucleus and organelles • Generates proteins and energy – Nerve fibers ~ extend from cell body 30-10 Neuron Structure (cont.) • Axons – One per neuron – Send nerve impulses away from the cell body • Dendrites – One or more per neuron – Receive nerve impulses for the neuron Common Diseases and Disorders of the Nervous System • Brain and spinal cord injuries – Causes • Motor vehicle accidents • Sports and recreational accidents • Violence – Children and teens at highest risk – Most are preventable 30-46 Common Diseases and Disorders of the Nervous System (cont.) Disease/Disorder Description Alzheimer’s disease Progressive, degenerative disease of the brain Amyotrophic lateral sclerosis (ALS) Degeneration of neurons in the spinal cord and brain; Lou Gehrig’s disease; fatal 30-47 Common Diseases and Disorders of the Nervous System (cont.) Disease/Disorder Description Bell’s palsy Weak or paralyzed facial muscles Brain tumors and cancers Abnormal growths Can be primary or secondary tumors; most common – gliomas 30-48 Common Diseases and Disorders of the Nervous System (cont.) Disease/Disorder Description 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; sudden and unexpected onset 30-49 Common Diseases and Disorders of the Nervous System (cont.) Disease/Disorder Description Headaches Tension Episodic or chronic Migraines Most severe form of headache Cluster Severe form of migraines; attacks occur in groups 30-50 Common Diseases and Disorders of the Nervous System (cont.) Disease/Disorder Description Meningitis Inflammation of meninges Multiple sclerosis (MS) Chronic disease of CNS; myelin is destroyed Neuralgias Disorders causing nerve pain 30-51 Common Diseases and Disorders of the Nervous System (cont.) Disease/Disorder Description Progressive and degenerative Parkinson’s disease motor system disorder Sciatica Stroke Damage to sciatic nerve Brain cells die because of an inadequate blood flow; “brain attack” 30-52 30-53 Apply Your Knowledge True or false: ANSWER: Bravo! 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 30-54 In Summary 30.1 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 Three types of neurons carry out the functions of the nervous system: the afferent (sensory) nerves detect sensation or other stimuli from the body or environment and bring it to the CNS for interpretation, the efferent (motor) nerves produce movement or other functions at the direction of the CNS, and the interpretive interneurons act as “interpreters” between the afferent and efferent nerves 30-55 In Summary (cont.) 30.2 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 function to bring impulses from the cell body to the dendrite of the next neuron 30-56 In Summary (cont.) 30.3 Nerve impulses send information either from the CNS to the PNS or vice versa 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 30-57 In Summary (cont.) 30.4 The brain consists of the cerebrum, diencephalon, brain stem, and cerebellum Other structures include the blood-brain barrier and the meninges The spinal cord consists of 31 spinal segments The basic function of the spinal cord is to carry sensory information to the brain and motor information to the muscles and glands of the body Cerebrospinal fluid (CSF) is located within the subarachnoid space and the central canal of the spinal cord It cushions the brain and spinal cord 30-58 In Summary (cont.) 30.5 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) 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 30-59 In Summary (cont.) 30.6 Tests commonly used to determine neurologic disorders include tests of the reflexes and cranial nerves, as well as diagnostic procedures such as lumbar puncture, MRI, PET, cerebral angiography, CT scan, EEG, and X-ray 30.7 Many types of diseases and disorders are 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 30-60 End of Chapter 30 Activity of the nervous system improves the capacity for activity, just as exercising a muscle makes it stronger.” ~ Dr Ralph Gerard ... synapses in their transmission 30. 4 Describe the structures and functions of the central nervous system 30- 3 Learning Outcomes (cont.) 30. 5 Compare the structures and functions of the somatic and autonomic.. .30- 2 Learning Outcomes (cont.) 30. 1 Describe the general functions of the nervous system 30. 2 Summarize the structure of a neuron 30. 3 Explain the function of nerve impulses and the role... diagnose and treat 30- 5 General Functions of the Nervous System • Central Nervous System (CNS) – Brain – Spinal cord • Peripheral Nervous System (PNS) – Peripheral nerves – Somatic nervous system