chapter 12 nervous system , notes
peripheral nervous system
contains the 12 pairs of cranial nerves and 31 pairs of spinal nerves. nerve: group or bundle of axon fibers located outside of CNS that carries messages between the CNS and various body parts. nerve root: the point at which the cranial and spinal nerves are attached to the CNS. afferent neurons/sensory neurons: carry sensory information from a sensory receptor to the CNS efferet neurons/motor neurons: carry activity instructions from the CNS to muscles or glands in the body. ganglion: the nerve cell bodies of the neurons that form the nerve are grouped in this knot like mass. nerves of this system are subdivided: autonomic nervous system (ANS) and somatic nerves.
autonomic nervous system
control of involuntary or unconscious body functions. may increase of decrease the activity of the smooth muscle found in viscera and blood vessels, cardiac muscle, and glands. divided into two branches: sympathetic branch and parasympathetic branch sympathetic nerves: control the "fight or flight" reaction during times of stress. increase heart rate, dilate airways, increase blood pressure, inhibit digestion, stimulate production of adrenaline. parasympathetic nerves: the "rest and digest" reaction. cause heart rate to slow, lower blood pressure, stimulate digestion.
function of the nervous system
it coordinates and controls body functions. it receives sensory input, makes decisions and then orders body responses. the organs of this system : brain (coordinates body functions) spinal cord (transmits messages to and from the brain) , nerves (transmit messages to and from the central nervous system)
spinal cord
provides a pathway for impulses traveling to and from the brain. extends from medulla oblongata to the second lumbar vertebra within the vertebral column. spinal cavity/vertebral canal: the 33 vertebrae of the backbone that line up to form continuous canal for spinal cord. central canal: the center of spinal cord where cerebrospinal fluid flows. inner core or spinal cord: consists of cell bodies and dendrites of peripheral nerves. is gray matter. outer portion: myelinated white matter. ascending tracts: carry sensory information up to the brain. descending tracts: carry motor commands down from the brain to a peripheral nerve.
somatic nerves
serve the skin and skeletal muscles, involved with conscious and voluntary activities of the body. the sensory receptors in the dermis layer of the skin use somatic nerves to send their information. these nerves also carry motor commands to skeletal muscles.
nervous system subdivision
the nervous system can be subdivided into the central nervous system (CNS) and the peripheral nervous system (PNS). CNS - brain and spinal cord. the nerves of the PNS are cranial and spinal nerves. sensory nerves carry info to the CNS, motor nerves carry commands away from it.
meninges
three layers of connective tissue membranes surrounding the brain and spinal cord. from external to internal: dura mater: (tough mother) forms tough fibrous sac around nervous system. subdural space: space between dura mater and arachnoid layers arachnoid layer: (spiderlike) thin, delicate layer attached to the pia mater by weblike filaments. subarachnoid space: space between the arachnoid layer and the pia mater. contains cerebrospinal fluid that cushions the brain from the outside. pia mater: (soft mother) innermost layer, applied directly to the surface of brain and spinal cord.
brain
alzheimer's disease : chronic, organic mental disorder consisting of dementia, which is more prevalent in adults over 65 years old. involves progressive disorientation, apathy, speech and gait disturbances, and loss of memory. named for alois alzheimer astrocytoma : tumor of the brain or spinal cord composed of astrocytes, one type of neuroglial cells. brain tumor: intracranial mass, either benign or malignant. a benign tumor of the brain can still be fatal since it will grow and cause pressure on normal brain tissue. cerebellitis : inflammation of the cerebellum cerebral aneurysm : localized abnormal dilation of a blood vessel, usually an artery; the result of a congenital defect or weakness in the wall of the vessel. a ruptured aneurysm is a common cause of a hemorrhagic cerebrovascular accident. cerebral contusion : bruising of the brain from a blow or impact. cerebral palsy (CP) : nonprogressive brain damage resulting from a defect, trauma, or oxygen deprivation at the time of birth cerebrovascular accident (CVA) : development of an infarct due to loss in the blood supply to an area of the brain. blood flow can be interrupted by a ruptured blood vessel (hemorrhage) , a floating clot (embolus), a stationary clot (thrombosis) , or compression. the extent of damage depends on the size and location of the infarct and often includes dysphasia and hemiplegia. commonly called a ''stroke'' concussion : injury to the brain resulting from the brain being shaken inside the skull from a blow or impact. symptoms vary and may include headache, blurred vision, nausea or vomiting , dizziness, and balance problems. also called mild traumatic brain injury (TBI) encephalitis : inflammation of the brain epilepsy : recurrent disorder of the brain in which seizures and loss of consciousness occur as a result of uncontrolled electrical activity of the neurons in the brain hydrocephalus : accumulation of cerebrospinal fluid within the ventricles of the brain, causing the head to enlarge. it is treated by creating a shunt for the fluid to leave the brain. if left untreated, it may lead to seizures and mental retardation. migraine : specific type of headache characterized by severe head pain, sensitivity to light, dizziness, and nausea. parkinson's disease : chronic disorder of the nervous system with fine tremors, muscular weakness, rigidity, and a shuffling gait. named sir james parkinson reye syndrome : combination of symptoms recognized by RDK reye that includes acute encephalopathy and damage to various organs, especially the liver. this occurs in children under 15 who have had a viral infection and also associated with taking aspirin. transient ischemic attack (TIA) : temporary interference with blood supply to the brain, causing neurological symptoms such as dizziness, numbness, and hemiparesis . may eventually lead to full blown stroke.
nervous tissue
ALL portions of the nervous system are composed of nervous tissue. nervous tissue is made up of two types of cells , neurons and neuroglial cells. neurons: individual nerve cells. conduct electrical impulses in response to stimuli. basic parts are the dendrites, nerve cell body and axon. dendrites: branched projections that received impulses. cell body: nucleus and other organelles. axon: projection from cell body that conducts the electrical impulse to its destination. synapse: the point at which the axon of one neuron meets the dendrite of the next neuron. synaptic cleft: gap between two neurons neurotransmitter: chemical messenger. myelin: fatty substance that acts as insulation for many axons so that they conduct electrical impulses faster.
signs and symptoms
absence seizure : type of seizure that lasts only a few seconds to half a minute, characterized by loss of awareness and an adsence of activity. also called petit mal seizure. analgesia : absence of pain anesthesia : lack of feeling or sensation aphasia : inability to communicate verbally or in writing due to damage of the speech or language centers in the brain ataxia : lack of muscle coordination aura : sensations, such as seeing colors or smelling an unusual odor, that occurs just prior to an epileptic seizure or migraine headache. cephalalgia : headache coma : profound unconsciousness resulting from an illness or injury conscious : condition of being awake and aware of surroundings convulsion : severe involuntary muscle contractions and relaxations. these have a variety of causes, such as epilepsy, fever, and toxic conditions. delirium : abnormal mental state characterized by confusion, disorientation, and agitation dementia : progressive impairment of intellectual function that interferes with performing activities of daily living. patients have little awareness of their condition. found in disorders such as alzheimer's . dysphasia : difficulty communicating verbally or in writing due to damage of the speech or language centers in the brain. focal seizure : localized seizure often affecting one limb. hemiparesis : weakness or loss of motion of one side of the body hemiplegia : paralysis on only one side of the body hyperesthesia : abnormally heightened sense of feeling, sense of pain, or sensitivity to touch monoparesis : muscle weakness in one limb monoplegia : paralysis of one limb neuralgia : nerve pain palsy : temporary or permanent loss of the ability to control movement paralysis : temporary or permanent of function or voluntary movement paraplegia : paralysis of the lower portion of the body and both legs paresthesia : abnormal sensations such as burning or tingling. quadriplegia : paralysis of all four limbs seizure : sudden, uncontrollable onset of symptoms, such as in an epileptic seizure semiconscious : state of being aware of surroundings and responding to stimuli only part of the time syncope : fainting tonic-clonic seizure : type of severe epileptic seizure characterized by a loss of consciousness and convulsions. the seizure alternates between strong continuous muscle spasms (tonic) and rhythmic muscle contraction and relaxation (clonic). it is also called a grand mal seizure. tremor : involuntary repetitive alternating movement of a part of the body unconscious : state of being unaware of surroundings, with the inability to respond to stimuli
combining forms
alges/o : sense of pain angi/o : vessel arteri/o: artery astr/o : star cephal/o : head cerebell/o : cerebellum cerebr/o : cerebrum clon/o : rapid contraction and relaxing cyt/o : cell dur/o : dura mater electr/o : electricity encephal/o : brain esthes/o : sensation, feeling gli/o : glue hemat/o : blood isch/o : to hold back later/o : side lumb/o : low back medull/o : medulla oblongata mening/o : meninges meningi/o : meninges my/o : muscle myel/o: spinal cord neur/o : nerve poli/o : gray matter pont/o : pons radicul/o : nerve root scler/o : hard spin/o : spine thalam/o : thalamus thec/o : sheath tom/o : to cut ton/o : muscle tone vascul/o : blood vessel ventricul/o : ventricle
spinal cord
amyotrophic lateral sclerosis (ALS) : disease with muscular weakness and atrophy due to degeneration of motor neurons of the spinal cord. also called lou gehrig's disease, after the yankees player who died. meningocele : congenital condition in which the meninges protrude through an opening in the vertebral column. myelitis : inflammation of the spinal cord myelomeningocele : congenital condition in which the meninges and spinal cord protrude through an opening in the vertebral column. poliomyelitis : viral inflammation of the gray matter of the spinal cord. results in varying degrees of paralysis, may be mild and reversible or severe and permanent. spina bifida : congenital defect in the walls of the spinal canal in which the laminae of the vertebra do not meet or close. spinal cord injury (SCI) : damage to the spinal cord as a result of trauma. may be bruised or severed.
medical specialties
anesthesiology : branch of medicine specializing in all aspects of anesthesia, including for surgical procedures, resuscitation measures, and the management of acute and chronic pain. neurology : concerned with diagnosis and treatment of diseases and conditions of the nervous system. neurosurgery : concerned with treating conditions and diseases of the nervous systems by surgical means.
nerves
bell's palsy : one sided facial paralysis due to inflammation of the facial nerve, probably viral in nature. the patient cannot control salivation, tearing of the eyes, or expression, but most will recover. guillain-barre syndrome : disease of the nervous system in which nerves lose their myelin covering. may be caused by autoimmune reaction. characterized by loss of sensation and/or muscle control starting in the legs. symptoms then move toward the trunk and may even result in paralysis of the diaphragm multiple sclerosis : inflammatory disease of the CNS in which there is extreme weakness and numbness due to loss of myelin insulation from nerves. myasthenia gravis : disease with severe muscular weakness and fatigue due to insufficient neurotransmitter at a synapse.
brain
four sections to the brain: cerebrum, cerebellum, diencephalon (thalamus, hypothalamus), brain stem (midbrain, pons, medulla oblongata) cerebrum: largest section. processes thoughts, judgement, memory, problem solving and language. cerebral cortex: outer layer of cerebrum. composed of folds of gray matter. gyri: elevated portions of the cerebrum, or convolutions. sulci: fissures, or valleys that separate the gyri. cerebral hemispheres: left and right halves of the cerebrum. each hemisphere has four lobes. frontal lobe: motor function, personality, and speech. (anterior) parietal lobe: receives and interprets nerve impulses from sensory receptors and interprets language.(superior) occipital lobe: vision (posterior) temporal lobe: hearing and smell (lateral) diencephalon : below the cerebrum, contains the thalamus and hypothalamus. thalamus: composed of gray matter, center for relaying impulses from eyes, ears and skin to the cerebrum, pain perception. hypothalamus: controls body temperature, appetite, sleep, sexual desire, and emotions. also controls autonomic nervous system, cardiovascular system, digestive system and release of hormones from pituitary gland. cerebellum: second largest portion. located beneath the posterior part of cerebrum. aids in coordinating voluntary body movements and maintaining balance and equilibrium. refines the muscular movements that is initiated in the cerebrum. brain stem: composed of midbrain, pons, and medulla oblongata. midbrain: pathway for impulses to be conducted between the brain and spinal cord. pons(bridge): connects the cerebellum to the rest of the brain. medulla oblongata: most inferior positioned portion of brain. connets brain to spinal cord. contains the centers that control respiration, heart rate, temperature, and blood pressure. the site where nerve tracts cross from one side of brain to control functions and movement on the other side of the body. left side of controls the right side. vice versa. ventricles: four interconnected cavities (one in each cerebral hemisphere, one in thalamus, one in front of cerebellum) cerebrospinal fluid (CSF): watery, clear fluid that protects the brain and spinal cord from shock or sudden motion.
CNS (central nervous system)
gray matter: unsheathed or uncovered cell bodies and dendrites. white matter: myelinated nerve fibers. tracts: bundles of nerve fibers interconnecting different parts of the CNS. meninges: three membranes that encase and protect the CNS.
