1. Explain the different structures and functions of the two main types of cells in the nervous system.
There are two types of cells found in the nervous system, neurons and neuroglia. The neuron is the functional cell that transmits impulses of the nervous system. These consist of three parts, the cell body, the axon, and dendrites. The cell body is the structure that contains the nucleus and the cytoplasm. The axon is a projection from the cell body that conducts impulses away from the cell body. The dendrites are tree-like structures that conduct impulses toward the cell body. A synapse, or space between two nerves, conducts impulses between the axon of one neuron and the dendrites of another neuron.
Neuroglia is the connective tissue of the nervous system. Neuroglia protect the nervous system and do not conduct impulses. There are three types of neuroglia. Astrocytes, the largest and most numerous cells which form the blood-brain barrier. Microglia, cells that engulf debris and waste to protect nerve tissue. Oligodendrocytes are cells that act as insulation and help to speed impulse conduction.
2. Describe the structures and functions of the peripheral nervous system (PNS). Be sure to include the nerves associated with the PNS, and contrast the functions of the somatic and autonomic nervous systems.
The peripheral nervous system is the set of nerves that communicates sensory and motor impulses between the central nervous system and the rest of the body. Made up of nerves, cordlike bundles that transmit impulses, and ganglia, a mass of nerve cell bodies outside the central nervous system, the peripheral nervous system commands organs to respond to impulses sent by the central nervous system.
The peripheral nervous system is divided into two categories, The somatic nervous system, controls skeletal muscles, and the autonomic nervous system, controls the involuntary muscles and glands. The autonomic nervous system has two nerve types, sympathetic (regulate involuntary functions) and parasympathetic nerves, counter the sympathetic nerves when needed.
3. Name the two primary components of the central nervous system (CNS). Describe the protective membranes associated with CNS. Differentiate between afferent and efferent nerve structure and function.
The central nervous system is made up of the brain and the spinal cord. There is bone (cranium), connective tissue (meninges), and cerebrospinal fluid to protect the brain and the spinal cord. Meninges are made up of the dura mater (outer layer), the arachnoid membrane, and the pia mater (the inner layer that is tightly bound to the brain and spinal cord). The space immediately outside the dura mater is called the epidural space and contains a layer of fat and connective tissue. Between the dura mater and the arachnoid membrane is a fluid filled space called the subdural space. Between the arachnoid membrane and the pia mater, there is a space called the subarachnoid space, which is filled with cerebrospinal fluid. This fluid is a protective shock absorbing layer. The central nervous system sends and receives impulses through the peripheral nervous system. Afferent nerves (sensory nerves) carry impulses from the body to the central nervous system, while efferent nerves (motor nerves) carry impulses to the muscles and glands.
4. Name and give a brief description of the structures of the brain. Include the functions of these structures.
The cerebrum, controls consciousness, memory, sensations, emotions, and voluntary movements, is the largest and uppermost portion of the brain. The cerebellum, attached to the brain stem, is responsible for maintaining muscle tone and coordinating normal movement and keeping balance. The diencephalon, is located between the cerebrum and the midbrain, contains several structures, the thalamus (receives sensory stimulus and relays it to the cerebral cortex), the hypothalamus (controls body temperature, sleep, and appetite), and the pineal gland (regulates the body’s clock by producing melatonin). The brain stem serves as a connection between the brain and the spinal cord, and controls breathing, blood pressure and heart rate.
5. Choose 10 pathological conditions affecting the nervous system; describe each including diagnosis and treatment, if applicable.
1. Alzheimer’s disease is a progressive and debilitating deterioration of intellectual functions. Usually beginning as memory loss, this disease progresses to loss of mental, emotional and even physical functions. There are no clinical tests for indentifying this disease, however a series of tests can help to diagnose a patient. There are medications to improve memory, antidepressants and tranquilizers are used to treat symptoms, however there is no cure.
2. Amyotrophic lateral sclerosis (ALS) is a severe weakening and loss of muscle. The symptoms usually begin with hands and progress to shoulders, upper arms, and legs. The loss of motor neurons in the brain stem and spinal cord cause a lack of electrical stimulation to the muscles. Patients with ALS will most likely suffer loss of speech, temperature control, verbal communication, and respiratory control. ALS has not cure, treatment focuses on keeping the patient and their family comfortable. Typical life expectancy after diagnosis is three to five years, but varies depending on the patient.
3. Carpal tunnel syndrome is caused by a compression of the median nerve in the arm. Repitious overuse of fingers, hands and wrists is the typical cause of inflammation that causes the compression. Patients can manage the pain by medications such as anti-inflammatory medications, splints, and physical therapy. Surgical therapy is needed when pain cannot be managed otherwise.
4. Migraine headaches are recurring, pulsating, vascular headaches usually beginning on one side of the head. Some people describe a visual interference (flashing light sensation) before the headache begins. Pain levels can increase and cause symptoms such as nausea and fatigue. Migraines are most common in females with a family history and can be triggered by stress. Migraines can last hours to days. Medications to prevent migraines can be used as well as medications to reduce symptoms once a migraine has set in.
5. Herniated disk is a rupture of the vertebral disk into the spinal cord or nerve roots. Herniations can be cause by trauma or by straining. Diagnosis is usually made with help of a CT scan, MRI, or myelogram. Surgical intervention is used only if treatments such as rest, heat applications, and anti-inflammatory medications do not work.
6. Multiple sclerosis (MS) is a degenerative inflammatory disease that interrupts the flow of nerve impulses to the central nervous system. Symptoms include poor balance and coordination, numbness or weakness of the extremities, urinary incontinence, facial pain or numbness, difficulty chewing and swallowing, fatigue, and muscular atrophy. Symptoms cause a greater risk for complications such as seizures, dementia, blindness, and infections. There is no cure for MS, the goal of medication therapy is to relieve symptoms and slow progression.
7. Narcolepsy is characterized by sudden attacks of sleep. The attacks can occur at any time and can last from minutes to hours. A polysomnogram may be performed to evaluate and diagnose narcolepsy. Medications can be used to treat this disorder.
8. Reye’s syndrome is acute brain encephalopathy accompanied by infiltration of the internal organs by fatty tissue, which allows viral infections. The syndrome is often seen in children between the ages of five and eleven, and is often fatal. Symptoms normally follow a pattern and are seen in stages. Symptoms include: sudden, unstoppable vomiting with confusion and lethargy; irritability; hyperactive reflexes; delirium; and hyperventilation; consciousness that progresses to a coma; sluggish pupillary response; periods of absent breathing, with fixed, dilated pupils; continued loss of cerebral function; seizures; loss of deep tendon reflexes; and respiratory arrest. Treatment, typically includes relief of intracranial pressure, and monitoring consciousness levels, and prognosis is directly related to the stage of symptoms when the diagnosis is made. Some patients require respiratory support and/or dialysis. This syndrome has been shown to be related to aspirin use.
9. Paraplegia is paralysis of the lower extremities, usually caused by injury of the thoracic or lumbar spinal cord. Injuries to the spinal cord result in loss of sensory and motor control below the injury. There is no cure for paraplegia, and patients often have problems with loss of bladder, bowel and sexual control.
10. Quadriplegia, like paraplegia is loss of sensory and motor control below the level of injury. Typically injuries that cause quadriplegia happen between the fifth and seventh cervical vertebrae. The higher the injury, the more debilitating the injuries. Paralysis of the lower extremities is accompanied by partial to full paralysis of the upper extremities, and sometimes cardiovascular complications, inability to regulate body temperature and perspire. Diagnosis is made with the help of x-rays, CT scans, and MRI scans. Emergency treatment to stabilize the injuries is crucial to prevent further damage. There is no cure for quadriplegia.
