Nervous System at a Glance Functions of Nervous System Coordinates and controls body function Receives sensory input Makes decisions Orders body responses Organs of Nervous System Nerves- transmits messages to & from the CNS Spinal cord- transmits messages to & from the brain Brain- coordinates all body functions

Medical Terminology: A Living Language, Fourth Edition Bonnie F. Fremgen and Suzanne S. Frucht Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Anatomy and Physiology of Nervous System Coordinates all activity of body Receives information from both external and internal sensory receptors Uses that information to adjust activity of muscles and glands to match needs of body Nervous system is divided into: Central nervous system (CNS) BRAIN and SPINAL CORD Peripheral nervous system (PNS) CRANIAL NERVES and SPINAL NERVES

Nervous Tissue Nervous system composed of two types of cells Neurons Neuroglial cells Individual nerve cells Conduct electrical impulses Neurons have three basic parts: Dendrites – highly branched projections that receive impulses Nerve cell body – contains nucleus & organelles Axon – conducts electrical impulse to destination

Figure 12.1A – The structure of a neuron. Medical Terminology: A Living Language, Fourth Edition Bonnie F. Fremgen and Suzanne S. Frucht Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Figure 12.1A – The structure of a neuron.

Medical Terminology: A Living Language, Fourth Edition Bonnie F. Fremgen and Suzanne S. Frucht Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Figure 12.1B – Photomicrograph of typical neuron showing the nerve cell body, nucleus, and dendrites.

Nervous Tissue (Neuron cont.) Synapse Point where axon of one neuron meets dendrite of second neuron Synaptic cleft Gap between two neurons in a synapse Electrical impulse cannot cross Neurotransmitter Chemical released by axon Crosses gap to stimulate dendrite of second neuron

Nervous Tissue Neuroglial cells Variety of cells found in nervous tissue Each has different support function for neurons Some neuroglial cells produce myelin, a fatty substance that acts as insulation for many axons Neuroglial cells DO NOT conduct electrical impulses

Medical Terminology: A Living Language, Fourth Edition Bonnie F. Fremgen and Suzanne S. Frucht Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved. Figure 12.2 – Electronmicrograph illustrating an axon (red) wrapped in its myelin sheath (blue).

Central Nervous System Combination of the brain and spinal cord Function Receives impulses from all over body Processes this information Responds with action Bundles of nerve fibers interconnecting different parts of CNS are called tracts

CNS Consists of both gray and white matter Gray matter Comprised of unsheathed or uncovered cell bodies and dendrites White matter Myelinated nerve fibers

The Brain One of the largest organs in body It is center for: Thoughts Memory Judgment Emotion

The Brain Four main sections: Cerebrum Cerebellum Diencephalon Brain stem

Cerebrum Largest section Upper portion Processes: Thoughts Judgment Memory Association skills Ability to discriminate between items

Cerebrum Cerebral cortex Gyri Sulci Outer layer of cerebrum Composed of folds of gray matter Gyri Elevated portions of the cerebrum, or convolutions Sulci Fissures, or valleys, between gyri

Lobes of Cerebrum Subdivided into left and right halves called cerebral hemispheres Each hemisphere has four lobes: Frontal lobe Parietal lobe Occipital lobe Temporal lobe

Lobes of Cerebrum Frontal lobe Parietal lobe Most anterior lobe Controls motor function, personality, and speech Parietal lobe Most superior portion Receives & interprets nerve impulses Interprets language

Lobes of Cerebrum Occipital lobe Temporal lobe Most posterior Controls vision Temporal lobe lateral portion Controls hearing and smell

Diencephalon Located inferior to cerebrum but superior & anterior to midbrain Contains two of most critical areas of brain: Thalamus Hypothalamus

Diencephalon Thalamus Hypothalamus Center for relaying impulses from eyes, ears, and skin to cerebrum Controls perception of pain Hypothalamus Controls body temperature, appetite, sleep, sexual desire, and emotions Controls autonomic nervous system, cardiovascular system, gastrointestinal system, and release of hormones from pituitary gland

Cerebellum Second largest portion of brain Located beneath posterior part of cerebrum Aids in: Coordinating voluntary body movements - Refines muscular movements initiated in cerebrum Maintaining balance and equilibrium

Brain Stem Has three components: Midbrain Pons Medulla oblongata

Brain Stem Midbrain Pons Medulla oblongata Acts as pathway for impulses between brain and spinal cord Pons Means bridge Connects cerebellum to rest of brain Medulla oblongata Most inferior portion of brain Connects brain to spinal cord

Brain Ventricles Cavities containing cerebrospinal fluid (CSF) Watery, clear fluid Provides shock protection for CNS Locations: One in each cerebral hemisphere One in thalamus One in front of cerebellum

Spinal Cord Extends from medulla oblongata to second lumbar vertebra Within vertebral column 33 vertebrae of back bone line up to form spinal cavity or vertebral canal

Spinal Cord Protected by cerebrospinal fluid Flows through central canal down through spinal cord Outer portion of spinal cord is myelinated white matter Ascending tracts carry sensory information up to brain Descending tracts carry motor commands down from brain to peripheral nerves

Medical Terminology: A Living Language, Fourth Edition Bonnie F. Fremgen and Suzanne S. Frucht Copyright ©2009 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

Meninges Protective membrane sac that encases entire CNS Consists of three layers: Dura mater Arachnoid layer Pia mater

Meninges Dura mater Means tough mother Outermost, tough, fibrous sac around CNS Subdural space Empty space between dura mater and arachnoid layer

Meninges Arachnoid layer Means spider-like Thin, delicate layer attached to pia mater by web-like filaments Subarachnoid space Between arachnoid layer and pia mater Contains cerebrospinal fluid

Meninges Pia mater Means soft mother Innermost membrane layer Applied directly to surface of brain

Peripheral Nervous System (PNS) Consists of: 12 pairs of cranial nerves 31 pairs of spinal nerves Cranial nerves Arise from brain Spinal nerves Split off from spinal cord One pair (left and right) exit between each pair of vertebrae

Nerves Nerve root A nerve: Point where nerve is attached to CNS Is a bundle of axon fibers located outside CNS Carries messages between CNS and various parts of body Nerve root Point where nerve is attached to CNS Names of most nerves reflect: Organ the nerve serves &/OR Portion of body the nerve is traveling through

Table 12.1 Cranial Nerves I Olfactory II Optic Oculomotor IV Trochlear sense of smell II Optic sense of sight Oculomotor controls eye muscles and pupil of eye IV Trochlear controls oblique muscles of eye V Trigeminal facial sensation and controls muscles for chewing VI Abducens controls eyeball muscles to turn eye to side

Table 12.1 Cranial Nerves VII Facial VIII Vestibulocochlear IX controls facial muscles for expression, salivation, and taste on two-thirds of tongue (anterior) VIII Vestibulocochlear sense of equilibrium and hearing IX Glossopharyngeal sensation from pharynx and taste on one-third of tongue X Vagus supplies most organs in abdominal and thoracic cavities XI Accessory controls neck and shoulder muscles XII Hypoglossal controls tongue muscles

Neurons Each nerve can carry information both to and from CNS But any individual neuron can carry information in only one direction Either an: Afferent neuron Efferent neuron

Neurons Afferent neurons Efferent neurons Also called sensory neurons Carry sensory information from sensory receptor to CNS Efferent neurons Also called motor neurons Carry activity instructions from CNS to muscles or glands

Divisions of PNS Nerves of PNS are subdivided into two divisions Autonomic nervous system (ANS) Somatic nerves Each division serves different area of body

1. Autonomic Nervous System (ANS) Control of involuntary or unconscious bodily functions It may increase or decrease the activity of: Smooth muscle found in viscera and blood vessels Cardiac muscle of heart Glands ANS divided into 2 branches: Sympathetic branch Parasympathetic branch

Parasympathetic branch Stimulates body in times of stress and crisis Increases heart rate, dilates airways, increases blood pressure, inhibits digestion, and stimulates production of adrenaline Parasympathetic branch Serves as counterbalance for sympathetic nerves Causes heart rate to slow down, lowers blood pressure, and stimulates digestion

2. Somatic Nerves Mainly involved with conscious and voluntary activities of body Serve skin and skeletal muscles Carry information from sensory receptors of skin Such as touch, temperature, pressure, and pain Carry motor commands to skeletal muscles