THE NERVOUS SYSTEM Humans have a complex nervous system with a brain, which is large in proportion to our body size. The nervous system performs three basic functions: 1. 2. 3. It receives, stores and analyses information from sense organs such as the eyes and ears, making us aware of our environment. It controls the physiological activities of the body systems and maintains constant conditions (homeostasis) within the body. It controls our muscles, enabling us to move and speak. The structure of the nervous system The nervous system can be classified into two major divisions – CNS and PNS, and one minor division – ANS. 1. Central Nervous System (CNS) – consists of the brain and spinal cord 2. Peripheral Nervous System (PNS) – is composed of 12 pairs of cranial nerves and 31 pairs of spinal nerves which connect the CNS with sense organs, muscles and glands. Functions of these nerves are mainly voluntary. Peripheral nerves carry impulses to the brain and spinal cord from receptors in the skin, eye, ear and nose and are called afferent (sensory) nerves (af- is a prefix that means towards, ferent means carry). Those that carry impulses from the CNS to organs that produce responses such as, muscles and glands are called efferent (motor) nerves, (ef- means away, ferent means carry). 3. Autonomic Nervous System (ANS) – this describes certain peripheral nerves that send impulses to internal organs and glands. It consists of involuntary or automatic nerves. Neur is the word root for the nervous system and a nerve, neuro is the combining form. It is the most complex of all the body systems. Word root Neur Combing form Meaning Neur/o nerve Neurons are the basic structural units of the nervous system. They are specialised cells, for the transmission of nerve impulses. There are three basic types of neuron sensory, motor and connector Activity 1 Write the meaning of: 1. neurology __________________________________________________ 2. neuropathy __________________________________________________ 3. neurohistology __________________________________________________ 4. polyneuritis __________________________________________________ 5. neurospasm __________________________________________________ THE NERVOUS SYSTEM Page 1 of 6 Plex Combining form Plex/o Cephal Cephal/o Head Encephal Encephal/o Brain Cerebr Cerebr/o The cerebral hemispheres or cerebrum of the brain Word root Meaning Network of nerves Activity 2 Write the meaning of; 1. Cephalalgia __________________________________________________ 2. Cephalocele __________________________________________________ 3. Hydrocephalus __________________________________________________ 4. Anencephalic 5. Electroencephalograph ____________________________________________ __________________________________________________ Build words which mean; 1. X-ray picture of the head ___________________________________________ 2. Pertaining to a very small head ______________________________________ 3. Tumour of a nerve ________________________________________________ 4. Hardening of a nerve ______________________________________________ 5. A specialist who studies nerves and their disorders ______________________ Disorders within blood vessels of the cerebrum can result in a stroke or apoplexy. Reduction of blood flow (ischaemia) within the cerebrum causes cells to die due to lack of oxygen and nutrients. As cells in this area control movements of many parts of the body, paralysis of limbs and loss of speech are common symptoms of a CVA. The severity of symptoms depends of the area of brain tissue damaged. Sometimes there is recovery and the patient is left with slight paralysis. The cerebral cortex The outer layer of the cerebrum is known as the cerebral cortex. It is extensively folded into fissures, giving it a large surface area. This part of the brain contains motor and sensory areas and is the site of consciousness and intelligence. Word root Combining form Meaning Ventricul Ventricul/o Ventricle Crani Crani/o Bones of the skull (cranium) Gangli Gangli/o, ganglion Swelling – knot of nerve body THE NERVOUS SYSTEM Page 2 of 6 Mening Mening/o, mening/i Membrane Radicul Radicul/o Spinal nerve roots Myel Myel/o Marrow Pleg -plegia Paralysis Aesthesi Aesthesi/o Narc Narc/o Alges Algesi/o, -algesia Perception of sensation Stupor – abnormally deep sleep induced by a drug Sense of pain Rachi Rachi/o Spine Activity 3 Write the meaning of; 1. Postganglionic ___________________________________________________ 2. Meningioma _____________________________________________________ 3. Epidural 4. Subdural haematoma ______________________________________________ ______________________________________________________ Build words which mean; 1. Incision into the skull ______________________________________________ 2. Condition of softening of the skull ____________________________________ 3. Inflammation of the meninges _______________________________________ SPINAL CORD The spinal cord (myel is the word root, myel/o the combining form) extends from the medulla oblongata to the second lumbar vertebra (the bony portion of the spine). It carries all of the nerves that affect the limbs and the lower parts of the body; it is the pathway for impulses going to and from the brain. The spinal cord is composed of an inner section of grey matter (poli/o is the combining form meaning grey matter of the brain or spinal cord) and an outer section of white matter. MENINGES The meninges are three layers of tissue that surround the brain and spinal cord; 1. The dura mater is the outermost membrane, it is tough and thick and it contains channels for blood to enter the brain tissue. The subdural space is below the dura membrane, it contains many blood vessels. 2. The arachnoid membrane is the second layer around the brain and spinal cord. The space is called the subarachnoid space which contains cerebrospinal fluid (CSF). THE NERVOUS SYSTEM Page 3 of 6 3. The third layer which is closest to the brain and spinal cord is the pia mater. It has a rich supply of blood vessels. Rachiocentesis is performed to obtain a sample of cerebrospinal fluid (CSF) from the subarachnoid space in the lumbar region of the spinal cord. This procedure is commonly known as a lumbar puncture or spinal tap. Damage to the brain or spinal cord can result in loss of movement in varying degrees, and to different parts of the body. There can be paralysis of limbs, paralysis of right or left side of the body, or paralysis of various activities such as speech. The term paraesthesia is used to mean any abnormal sensations, such as ‘pins and needles’. Activity 4 Write the meaning of: 1. Quadriplegia _____________________________________________________ 2. Hemiplegia ______________________________________________________ 3. Paraplegia ______________________________________________________ 4. Anaesthesia _____________________________________________________ 5. Anaesthetic _____________________________________________________ 6. Anaesthesiology __________________________________________________ 7. Anaesthesiologist _________________________________________________ 8. Analgesia ______________________________________________________ 9. Analgesic ______________________________________________________ 10. Narcosis ______________________________________________________ BRAIN ‘Encephal’ is the word root for the brain, (en- is a prefix that means in / within, cephal is the root for head- within the head is the brain) Parts Combining form Cerebrum cerebr/o Cerebellum cerebell/o Thalamus thalam/o Hypothalamus (hypomeans below) is situated below the thalamus Brain stem consists of the pons, and medulla oblongata THE NERVOUS SYSTEM Function/Description The cerebrum is the largest part of the brain and has many functions:all thought; judgement; memory; association; discrimination; sensation The cerebellum coordinates voluntary movement The thalamus is a large grey mass that acts as a relay centre for body sensations, pain The hypothalamus contains neurons that control body temperature, sleep, appetite and emotions such as fear and pleasure The brain stem is the connection of nerve fibre tracts. The medulla oblongata is where nerve fibres cross over and contains centres to regulate heat, blood vessels and the respiratory system Page 4 of 6 COMMON CONDITIONS OF THE BRAIN Condition Alzheimer’s disease Palsy Bell’s palsy Cerebral palsy Parkinson’s disease Multiple sclerosis (ms) Epilepsy Meaning Brain disorder marked by deterioration of mental capacity (dementia), resulting in degeneration of neurons and neurofibrillary tangles in the cerebral cortex unilateral (uni- is a prefix which means one) facial paralysis, due to disorder of the facial nerve, aetiology unknown, but recovery is usually complete partial paralysis and lack of muscular coordination due to damage to the cerebrum during birth Degeneration of the nerves in the brain, leads to tremors, weakness of muscles and slowness of movement One of the leading causes of neurological disability, and a chronic disease. The conduction of nerve impulses through the axon is prevented leading to paraesthesia, muscle weakness, unsteady gait and paralysis Chronic disorder characterised by recurrent seizures and/or fitting activity. Seizures and/or fitting are often symptoms of brain disease conditions, such as tumours, meningitis, vascular disease or tissue scarring from a head injury. Terms and Word Parts: cephal/o encephal/o cerebell/o cerebr/o chord/o hemilamin/o -lexia lumbar mening/o meninges myel/o narc/o neur/o occipit/o -paresis -plegia plexus synapse head brain cerebellum (reflex centre for the control of skeletal muscles (largest part of the hindbrain) cerebrum (largest and uppermost part of the brain - controls higher brain functions) a cord half lamino /thin plate / part of vertebral arch condition of speech / words pertaining to the lower back or loin meninges three membranes that surround the brain and spinal cord. outer –dura mater, then arachnoid mater then pia mater spinal cord or bone marrow numbness, stupor nerves occiput, posterior region of the skull weakness, slight paralysis paralysis a network of vessels or nerves membrane-to-membrane contact of the nerve cell with another nerve cell THE NERVOUS SYSTEM Page 5 of 6 Abbreviations: CAT or CT Scan CNS EEG MRI (Magnetic Resonance Imaging) Computerised Axial Tomography - for the examination of the soft tissues of the body. Ionising x-rays are beamed through the patient at multiple angles, and a computer synthesises the information. Central Nervous System Electroencephalogram. (brainwave recording) X-rays or a contrast medium are not used. Uses movement of hydrogen nuclei (present in water and living tissue) to a larger magnetic field. Conditions and Terms: anaesthesia loss of sensation resulting from medication analgesia loss or reduction of pain sensation cerebrospinal pertaining to the brain and spinal cord encephalitis inflammation of the brain hemiparesis weakness on one side (half) of the body hemiplegia paralysis on one side (half) of the body hydrocephalus excessive amount of cerebrospinal fluid within the skull lumbar pertaining to the lower back or loin puncture of the lumbar area of the spinal canal for removal of cerebrospinal fluid especially for diagnostic purposes or the introduction of medication complete or partial loss of controlled movement pain that radiates along the sciatic nerve, usually affects buttocks, thigh, and foot sensation that one or one's surroundings are spinning lumbar puncture paralysis sciatica vertigo TRAUMATIC DISORDERS Cerebral Contusion bruising of the brain Subdural Haematoma Sub prefix meaning below dur word root for dura -al suffix meaning pertaining to Haemat word root for blood -oma suffix meaning tumour/swelling Epidural Haematoma Epi prefix meaning above/upon dur word root for dura -al suffix meaning pertaining to Haemat word root for blood -oma suffix meaning tumour/swelling THE NERVOUS SYSTEM Page 6 of 6