MED TERM Chapter 10 - Lecture notes Neurology PDF

Preview

Summary

completed lecture notes on neurology...

Description

MEDICAL TERMINOLOGY: Chapter 10 Neurology

Objectives of Chapter 10: 1. Identify structures of the nervous system. 2. Describe the process of nerve transmission. 3. Describe common nervous system diseases, laboratory and diagnostic procedures, medical and surgical procedures, and drugs. 4. Form the plural and adjective forms of nouns related to neurology. 5. Give the meanings of word parts and abbreviations related to neurology. 6. Divide neurology words and build neurology words. 7. Spell and pronounce neurology words. 8. Research sound-alike and other neurology words. 9. Analyze the medical content and meaning of neurology reports

Anatomy and Physiology The nervous system is a body system that is found in every part of the body from the head to the tips of the fingers and toes. The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system. The central nervous system contains the brain and the spinal cord. The -peripheral nervous system contains the cranial nerves and the spinal nerves. The peripheral nervous system can be divided into the autonomic nervous system (which includes the parasympathetic and sympathetic divisions) and the somatic nervous system.

Anatomy of the Central Nervous System Brain The brain is the largest part of the central nervous system. It is located within the bony cranium and fills the cranial cavity. The brain consists of the cerebrum (and its lobes), the thalamus, hypothalamus, ventricles, brainstem, and cerebellum. The brain is surrounded by the meninges, three layers of membranes.

Cerebrum The largest and most obvious part of the brain is the cerebrum. The cerebrum is divided into lobes. Each lobe has the same name as the cranial bone that is above it. The lobes of the cerebrum have the following functions: 1. Frontal Lobe o Originates conscious thought and intelligence o Predicts future events and the benefits or consequences of actions o Coordinates and analyzes information coming from other lobes of the cerebrum o Exerts conscious, voluntary control over the skeletal muscles o Coordinates the muscles of the mouth, lips, tongue, pharynx, and larynx to produce speech. This is done in the speech center, which is only in the left frontal lobe. o Analyzes sensory information about taste. This information comes from taste receptors in the tongue and throat and is analyzed by the gustatory cortex of the frontal lobe. 2. Parietal Lobe o Analyzes sensory information about touch, temperature, vibration, and pain. This information comes from receptors in the skin, joints, and muscles and is analyzed by the somatosensory area of the parietal lobe. 3. Temporal Lobe o Analyzes sensory information about hearing. This information comes from receptors in the cochlea of the inner ear and is analyzed by the auditory cortex of the temporal lobe. (The auditory cortex of the right temporal lobe analyzes

sensory information from the left ear, and the auditory cortex of the left temporal lobe analyzes sensory information from the right ear.) o Analyzes sensory information about smells. This information comes from olfactory receptors in the nose and is analyzed by the olfactory cortex of the temporal lobe. 4. Occipital Lobe o Analyzes sensory information about vision. This information comes from receptors in the retina of the eye and is analyzed by the visual cortex of the occipital lobe. (The visual cortex of the right occipital lobe analyzes sensory information from some parts of both eyes, and the visual cortex of the left occipital lobe analyzes sensory information from the other parts of both eyes, and this gives three-dimensional vision.) There is a very deep, anterior-to-posterior fissure in the superior surface of the cerebrum. It divides the cerebrum into right and left halves. Each half of the cerebrum is a hemisphere. The only connection between the right and left hemispheres is the corpus callosum . This connecting band of neurons deep within the brain allows the two hemispheres to communicate with each other and coordinate their activities. The hemisphere on one side of the brain receives sensory information from the other side of the body and sends motor commands to that side. In general, the right hemisphere of the cerebrum plays an important role in recognizing faces, patterns, and three-dimensional structures. The right hemisphere also analyzes the emotional content of words but not the actual words. The left hemisphere of the cerebrum performs -mathematical and logical reasoning, problem-solving, and it -coordinates the recall of memories. It is important in language skills and processing language. The surface of the cerebrum has elevated folds (gyri) and narrow grooves (sulci). The cerebral cortex or gray matter is the outermost layer of tissue that follows the curves of the gyri and sulci. The gray matter is composed of the cell bodies of neurons. Beneath it, the white matter of the cerebrum is composed of the axons of neurons. Most of these axons are covered by a fatty, white insulating layer of myelin. Myelin increases the speed of an electrical impulse along the neuron and gives the white color to the white matter of the cerebrum.

Thalamus The thalamus is located near the center of the cerebrum. Its two lobes form the walls of the third ventricle. The thalamus acts as a relay station, receiving sensory information (sight, hearing, taste, smell, and touch) from the cranial nerves and the spinal nerves. The thalamus sends this to (1) the midbrain (that generates motor commands if the sensory information suggests an immediate danger) and (2) the cerebrum (that analyzes sensory information, compares it with memories, and uses it to plan future actions). The thalamus is also part of the limbic system that deals with emotions.

Hypothalamus The hypothalamus, as its name indicates, is located below the thalamus. It forms the floor and part of the walls of the third ventricle, and it has a stalk of blood vessels and nerves that connects it to the

pituitary gland. The hypothalamus functions as part of both the endocrine system and the nervous system. As part of the endocrine system, the hypothalamus produces hormones that control the functions of the anterior pituitary gland; it also produces other hormones that are stored in, and released by, the posterior pituitary gland. As part of the nervous system, the hypothalamus coordinates the activities of the pons and medulla oblongata, which control the heart rate, blood pressure, and respiratory rate. The hypothalamus also regulates body temperature and sensations of hunger and thirst. The hypothalamus also plays a role in emotions and sexual drive.

Ventricles The ventricles are four interconnected cavities within the brain. The largest of these are the lateral ventricles, two C-shaped cavities, one in each hemisphere in the cerebrum. The third ventricle, a small central cavity, lies between the two lobes of the thalamus. The fourth ventricle is a long, narrow cavity that connects to the spinal cavity. The ependymal cells that line the ventricles produce cerebrospinal fluid (CSF), a clear fluid that cushions and protects the brain and contains glucose and other nutrients. Cerebrospinal fluid flows through the ventricles, into the spinal cavity, then back toward the brain, and through the subarachnoid space in the meninges where it is absorbed into the blood of large veins.

Brainstem The brainstem is a column of tissue that begins in the center of the brain and continues inferiorly until it meets the spinal cord. It is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is the most superior part of the brainstem. It keeps the mind conscious. It coordinates immediate reflex responses to things you see or hear (such as a child suddenly crossing in front of your car or a very loud noise). It maintains muscle tone and the position of the extremities so that you do not have to consciously think about them. It contains the substantia nigra, a gray-to-black pigmented area that produces the neurotransmitter dopamine that regulates muscle tone. The pons is the next part of the brainstem. It relays nerve impulses from the spinal cord to the midbrain, hypothalamus, thalamus, and cerebrum. The medulla oblongata is the most inferior part of the brainstem. It contains the respiratory centers that automatically set the respiratory rate and other centers that control the heart rate. (In the medulla oblongata, nerve tracts cross, and nerve impulses from the right side of the body are relayed to the left side of the cerebrum, and vice versa.) Cerebellum The cerebellum is the separate, rounded section of the brain that is inferior and posterior to the cerebrum. The cerebellum receives sensory information about muscle tone and the position of the body and uses this to help maintain balance. It receives information from the cerebrum about motor

commands and makes minor adjustments to coordinate those movements, especially intricate movements such as typing or skiing.

Meninges The brain is surrounded by the meninges , three separate membrane layers. The outermost membrane (beneath the bony cranium) is the dura mater , a tough, fibrous layer that protects the brain. The second layer is the -arachnoid. Beneath the arachnoid is the subarachnoid space, which is filled with cerebrospinal fluid and contains large, branching fibers that connect the arachnoid to the pia mater beneath it. The innermost layer is the pia mater, a thin, delicate membrane next to the brain; it contains a spider-weblike network of small blood vessels. Spinal Cord The spinal cord is part of the central nervous system. The spinal cord is a long, narrow column of neural tissue within the spinal cavity (or spinal canal). At its superior end, the spinal cord joins the medulla oblongata of the brain. The spinal cord extends to the level of the second lumbar vertebra in the vertebral column. There, at its inferior end, the spinal cord becomes a group of nerve roots known as the cauda equina. The spinal cord is protected because it is within the central opening (foramen) of each bony vertebra. The spinal cord is also protected and nourished by the meninges, which continue in an uninterrupted fashion from the brain down the spinal cavity. A narrow canal at the center of the spinal cord is lined with ependymal cells that also produce cerebrospinal fluid. There is one difference between the meninges around the brain and those around the spinal cord; between the dura mater and the bony vertebrae is the epidural space, an area that is unique to the spinal cord. This space is filled with fatty tissue and blood vessels. The gray matter of the spinal cord is composed of the cell bodies of neurons in the spinal cord and spinal nerves. The white matter of the spinal cord is composed of the axons of neurons bundled together as an ascending tract that carries sensory information from a sensory spinal nerve to the brain or as a descending tract that carries motor commands from the brain to a motor spinal nerve connected to a muscle.

Anatomy of the Peripheral Nervous System Cranial Nerves The cranial nerves are part of the peripheral nervous system. There are 12 pairs of cranial nerves. Each pair consists of a cranial nerve to the right side of the body and a cranial nerve to the left side of the body. Each pair of cranial nerves has a name that reflects its location or function. Some cranial nerves receive sensory information from the body (visual images, sounds, smells, tastes, touch, pressure, vibration, temperature, pain, or position). Other cranial nerves send motor commands from the brain to voluntary muscles (to move the face, head, and neck) or to involuntary muscles (to slow the heart rate, to cause peristalsis in the digestive tract, to cause the bronchioles to constrict, to cause the lacrimal or salivary glands to secrete tears or saliva). Some cranial nerves carry both sensory and motor

nerve impulses. Cranial Nerve I Olfactory Nerve

Type of Nerve Sensory

Function Smell Receives sensory information about smells from olfactory receptors in the nose

II Optic Nerve

III Oculomotor Nerve

Sensory

Vision

Motor

Receives sensory information about light, dark, and color from rods and cones in the retina of the eye Eye movement Sends motor commands to the extraocular muscles to move the eye.

IV Trochlear Nerve

V Trigeminal Nerve

Motor

Sends motor commands to move the eyelid and to muscles of the iris to increase or decrease the diameter of the pupil. Eye movement

Sensory

Sends motor commands to the extraocular muscles to move the eye Facial sensation Receives sensory information about touch, temperature, vibration, and pain from the skin of the face, the eyes, the nasal cavity, oral cavity,

Location Begins at receptors in the nose Goes to the olfactory bulb (and on to the olfactory cortex) in the temporal lobe Begins at receptors in the retina Goes to the optic chiasm in the brain

Begins in the midbrain (of the brainstem) Goes to four of the six extraocular muscles around the eye Goes to the eyelid Goes to the iris

Begins in the midbrain (of the brainstem) Goes to one of the six extraocular muscles around the eye Begins at receptors in the skin and mucous membranes of those areas Goes to the pons (of the brainstem)

V Trigeminal Nerve (contd.)

Motor

gums, teeth, tongue, and palate Chewing Sends motor commands to move the muscles for chewing

VI Abducens Nerve

VII Facial Nerve

VII Facial Nerve

Motor

Eye movement

Sensory

Sends motor commands to the extraocular muscles to move the eye Taste

Motor

Receives sensory information about taste (sweet, sour, bitter, etc.) from taste receptors in the front of the tongue Facial movement, Tears and saliva Sends motor commands to move the facial muscles. Contracts the lacrimal glands to secrete tears.

VIII Vestibulocochlear Nerve

Sensory

Contracts the submandibular and sublingual salivary glands to secrete saliva. Hearing and balance Receives sensory information about sounds from the cochlea (in the inner ear). Receives sensory information from the

Begins in the pons (of the brainstem) Goes to the lower jaw (mandibular branch of the nerve) Begins in the pons (of the brainstem) Goes to one of the six extraocular muscles around the eye Begins at receptors in the tongue Goes to the pons (of the brainstem)

Begins in the pons (of the brainstem) Goes to the facial muscles Goes to the muscles in the lacrimal glands Goes to the muscles in the submandibular and sublingual salivary glands

Begins at receptors in the vestibule (entrance to the cochlea) and in the semicircular canals in the inner ear Goes to the pons and medulla oblongata (of the brainstem)

IX Glossopharyngeal Nerve

Sensory

semicircular canals to keep the balance of the body. Taste Receives sensory information about taste (sweet, sour, bitter, etc.) from taste receptors at the back of the tongue, palate, and pharynx.

IX Glossopharyngeal Nerve

Motor

Receives sensory information about the blood pressure and oxygen/carbon dioxide levels in arterial blood from pressure receptors in the carotid artery. Swallowing Sends motor commands to move the muscles involved in swallowing.

Begins at receptors in the tongue, palate, and pharynx Begins at receptors in the carotid artery Goes to the medulla oblongata (of the brainstem)

Begins in the medulla oblongata (of the brainstem) Goes to muscles in the pharynx and parotid gland

Saliva

X Vagus Nerve

Sensory

Contracts the parotid gland to secrete saliva. Taste Receives sensory information about taste (sweet, sour, bitter, etc.) from taste receptors in the soft palate and pharynx. Ear, chest, and abdomen sensation Receives sensory information about touch, temperature, vibration, and pain

Begins at receptors in the soft palate and pharynx Begins at receptors in the skin and smooth muscles Goes to the medulla oblongata (of the brainstem)

XI Accessory Nerve

Motor

from receptors in the ear, diaphragm, and organs in the thoracic cavity and abdominopelvic cavity. Swallowing Sends motor commands to move the muscles involved in swallowing.

Begins in the medulla oblongata (of the brainstem) Goes to muscles in the pharynx, larynx, neck, and upper back

Vocal cord and neck movement

XII Hypoglossal Nerve

Motor

Moves the vocal cords. Moves the muscles of the neck and upper back. Tongue movement Sends motor commands to move the tongue

Begins in the medulla oblongata (of the brainstem) Goes to the muscles of the tongue

Spinal Nerves The spinal nerves are part of the peripheral nervous system because they are found in the periphery of the body (those parts away from the center). There are 31 pairs of spinal nerves that originate at regular intervals along the spinal cord. Each pair consists of a spinal nerve to the right side of the body and a spinal nerve to the left side of the body. Each pair of spinal nerves is named according to the vertebra next to it. Each spinal nerve has two different groups of nerve roots that connect it to the spinal cord: dorsal nerve roots and ventral nerve roots. The posterior or dorsal nerve roots receive sensory information (touch, pressure, vibration, temperature, pain, and body position) from the skin. Each dorsal nerve root receives sensory information from a specific area of the skin known as a dermatome. Dermatomes are important in the diagnosis of nerve injuries because they correlate a specific spinal nerve and its dermatome to an area of the skin where there is loss of sensation or movement. The dorsal nerve roots also receive sensory information from the muscles and joints. Dorsal nerve roots and their spinal nerve are an afferent nerve because they carry nerve impulses from the body to the spinal cord.

The anterior or ventral nerve roots carry motor commands from the spinal cord to skeletal muscles and involuntary smooth muscles within organs, glands, and other structures. Ventral nerve roots and their spinal nerve are an efferent nerve because they carry nerve impulses from the spinal cord to the body. A reflex is a rapid, involuntary muscle reaction that is controlled by the spinal cord. The spinal cord reacts immediately to certain types of sensory information (sudden pain or when a physician uses a percussion hammer to tap on a tendon that stretches a muscle). For example, accidentally placing your hand on a hot stove causes you to pull your hand away, even before your brain understands what is wrong. Sensory information from a spinal nerve in the hand reached the spinal cord, and the spinal cord immediately sent a motor command to muscles to make you move your hand. This circuit is known as a reflex arc. Later, the sensory information is analyzed by the brain, and you say “Ouch.” Autonomic Nervous System The autonomic nervous system controls the contractions of involuntary cardiac muscle in the heart, as well as smooth muscles around organs, glands, and other structures. The autonomic nervous system can be further broken down into two divisions: the parasympathetic division and the sympathetic division. The parasympathetic division is active when the body is sleeping, resting, eating, or doing light activity (so-called “rest and digest” activities). The neurotransmitter of the parasympathetic division is acetylcholine. The action of the parasympathetic division and acetylcholine is to: 1. 2. 3. 4. 5. 6.

Decrease the heart rate, blood pressure, and metabolic rate Increase or decrease the diameter of the pupils in response to...