Abstract
The nervous system (NS) is comprised of nerve cells (neurons), which transfer and process information, and neuroglia (or glial cells), which provide the supportive framework neurons need to function effectively. There are two divisions of the nervous system: central (CNS) and peripheral (PNS). The CNS consists of the brain and spinal cord and forms an intricate network of specialised cells that are responsible for coordinating all bodily functions. The PNS delivers sensory information from peripheral sensory tissues and systems to the CNS and carries motor commands from the CNS to peripheral tissues. This chapter discusses 15 diseases that directly affect the nervous system mostly caused by mutations in a single gene, with others having more complex modes of inheritance. They include Alzheimer's Disease, epilepsy, essential tremor, familial Mediterranean fever, Friedreich's ataxia, Huntington's disease, maple syrup syndrome, Menkes disease, narcolepsy, Parkinson's Disease, phenylketonuria, Refsum disease, spinal muscular atrophy, tangier disease, and spinocerebellar ataxia.
TopChapter Outline
18.1 Overview of the Nervous System
18.2 Alzheimer’s Disease
18.3 Epilepsy
18.4 Essential Tumor
18.5 Familial Mediterranean Fever
18.6 Friedreich’s Ataxia
18.7 Huntington’s Disease
18.8 Maple Syrup Urine Disease
18.9 Menkes Disease
18.10 Narcolepsy
18.11 Parkinson’s Disease
18.12 Phenylketonuria
18.13 Refsum Disease
18.14 Spinal Muscular Atrophy
18.15 Tangier Disease
18.16 Spinocerebellar Ataxia
Chapter Summary
TopLearning Outcomes
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Identify each genetic disorder affecting each system
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Outline the symptoms of each disorder
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Explain the genetic basis of each disorder
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Summarize the current therapies available to treat each disorder
Top18.1 Overview Of The Nervous System
The nervous system (NS) is comprised of nerve cells (neurons) which transfer and process information; and neuroglia (or glial cells) which, twenty times more numerous, provide the supportive framework neurons need to function effectively. There are two divisions of the nervous system: central (CNS) and peripheral (PNS) (Figure 1). The CNS consists of the brain and spinal cord and forms an intricate network of specialised cells that are responsible for coordinating all bodily functions. It is the seat of higher functions like intelligence, memory, learning and emotions and also integrates, processes, and coordinates sensory data and motor commands. The PNS is all neural tissue outside the CNS and delivers sensory information from peripheral sensory tissues and systems like eyes to the CNS. It also carries our motor commands from the CNS to peripheral tissues. Sensory information in the PNS comes from sensory receptors in the eyes, nose, ears, mouth and also from receptors in the skin, muscles, and joints. Motor command information is delivered via the somatic NS which controls voluntary and involuntary skeletal muscle contractions; and the visceral or autonomic NS which controls smooth muscle, cardiac muscles and glandular activity (without conscious control). There several diseases that directly affect the NS with a genetic component—some are due to a mutation in a single gene, while others have more complex modes of inheritance.
Figure 1. The central and peripheral nervous systems in humans
Key Terms in this Chapter
Proteopathy: Diseases involving the disruption of cell function as a result of the production of abnormal proteins.
Leukoencephalopathy: Neurological disorders of white matter in the brain.
Plasmapheresis: Removal of plasma from a patient’s blood.
Psychosis: Disorders of mental illnesses that result in abnormal thinking, perceptions, behaviour, and emotions.
Cataplexy: A condition characterized by sudden and uncontrollable voluntary muscle weakness caused by strong emotion or laughter and often results in physical collapse while conscious.
Lewy Body Disease: One of the most common causes of dementia which results from the abnormal accumulation of alpha-synuclein in the brain.
Dystonia: A neurological disorder marked by involuntary muscle contractions.
Kinetic Tremor: A rhythmic, involuntary movement of a body part that is associated with voluntary movements.
Erythropoiesis: Production of red blood cells which is initiated by the decreasing levels of oxygen which cause erythropoietin hormone production in the kidneys.
Dysarthria: A speech disorder characterized by poor articulation of speech.
Cerebral Amyloid Angiopathy: A condition caused by a build-up of amyloid on the walls of the arteries in the brain which can lead to a brain haemorrhage and dementia.
Hepatosplenomegaly: Abnormal enlargement of both the spleen and liver.
Argyrophilic Grain Disease: A neurodegenerative disease marked by the presence of argyrophilic grains.
Astrogliosis: A chemical reaction involving an increase of astrocytes due to damage after CNS injuries.
Pathognomic: A characteristic that is indicative of a particular disease.
Lipopheresis: Removal of low-density lipoprotein cholesterol from a patient’s blood.
Proteolisis: The process of breaking down proteins into smaller polypeptides or into amino acids.
Dysdiachokinesia: The inability to perform quick, alternating movements.
Cholinesterase Inhibitors: A class of drugs that prevent the breakdown of acetylcholine.
Dysphasia: A condition in which the ability to produce and understand language is affected.
Apheresis: A medical procedure in which an individual component is removed from a patient's blood using an apparatus that separates the components and returns the remaining blood into the patient.
Antipsychotics Drugs: A group of drugs used to treat mental health conditions.
Dysmetria: A condition that occurs as a result the development of lesions in the cerebellum which then affects coordinated movement, thought processing, and behaviour.
Ataxia: A neurological condition involving the loss of voluntary muscle movement.
Hyperphenylalaninaemia: Abnormally elevated levels of plasma phenylalanine.