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Nervous System Suzanne D'Anna 1 Nervous System master control system master communicating center nerve tissue develops from embryonic ectoderm Suzanne D'Anna 2 Role of the Nervous System monitors changes - (sensory function) processes and interprets information - (integrative) elicits responses - (motor) Suzanne D'Anna 3 Nervous System Organization anatomical organization - central nervous system (CNS) - peripheral nervous system (PNS) functional organization - sensory - integrative - motor Suzanne D'Anna 4 Central Nervous System (CNS) brain - cerebrum - diencephalon four principal parts - brain stem - cerebellum spinal cord - continuation of brain stem - continues from base of skull to the 1st lumbar vertebra Suzanne D'Anna 5 diencephalon cerebrum pituitary gland brain midbrain stem pons medulla oblongat Suzanne D'Anna a cerebellum spinal cord 6 Peripheral Nervous System (PNS) cranial nerves - 12 pairs - emerge from the brain spinal nerves - 31 pairs - emerge from the spinal cord Suzanne D'Anna 7 Functional Organization sensory - gathers information that occurs within internal and external environment integrative - analyzes sensory information - decides necessary responses motor - carries instructions (nerve impulses) to muscles and glands (effectors) Suzanne D'Anna 8 Basic Types of Functional Neurons Suzanne D'Anna 9 Sensory Neurons afferent neurons - carry information from various body parts to the brain or spinal cord (input) Motor Neurons efferent neurons - carry instructions from the CNS to muscles and glands (output) Suzanne D'Anna 10 Interneurons or Connecting Neurons analyze information determine appropriate response located in the CNS Suzanne D'Anna 11 Peripheral Nervous System (subdivisions) somatic nervous system (soma = body) - voluntary - sensations are consciously perceived autonomic nervous system (auto = self) - involuntary and automatic - sensations are usually not consciously perceived Suzanne D'Anna 12 Somatic Nervous System (SNS) sensory neurons - carry impulses to the CNS from receptors for general and special senses (touch, pressure, vibration, temperature, pain, proprioception, smell, taste, vision,hearing and equilibrium) motor neurons - carry impulses away from CNS only to skeletal muscles Suzanne D'Anna 13 Autonomic Nervous System (ANS) sensory neurons - carry impulses to the CNS from visceral receptors (internal organs) motor neurons - carry impulses from CNS to smooth muscle, cardiac muscle, and glands Suzanne D'Anna 14 Motor Division of Autonomic Nervous System Two principal divisions work together, i.e., impulses of one division activate an organ, while impulses from the other division inhibit the organ sympathetic parasympathetic Suzanne D'Anna 15 Sympathetic prepares the body for energyexpending, stressful, or emergency situations Parasympathetic active under normal ordinary, restful conditions counterbalances effects of sympathetic division restores body to resting state Suzanne D'Anna 16 Protection and Coverings of the Brain bones of cranium cerebrospinal fluid connective tissue membranes called meninges vertebral column Suzanne D'Anna 17 Cranium frontal sphenoid ethmoid occipital parietal temporal Suzanne D'Anna 18 Cerebrospinal Fluid (CSF) formed by filtration and secretion from networks of capillaries - choroid plexuses located in the (4) ventricles of the brain form blood-brain barrier clear, colorless liquid contains glucose, proteins, lactic acid, urea, cations, anions, and lymphocytes Suzanne D'Anna 19 Cerebrospinal Fluid (cont.) acts as shock-absorbing medium protects brain from banging against inner walls of cranium is a medium for exchange of nutrients and waste products between blood and nervous tissue Suzanne D'Anna 20 Cerebrospinal Fluid (cont.) significant changes in composition can indicate disease conditions - meningitis - tumors - multiple sclerosis if drainage of CSF is obstructed, excessive pressure on the brain will cause hydrocephalus Suzanne D'Anna 21 Blood-Brain Barrier permits certain substances to enter the fluid but prohibits others protects the brain from harmful substances formed by tightly adherent cell connections Suzanne D'Anna 22 Meninges protective membranes delicate envelop brain and spinal cord Three connective tissue membranes: - dura mater - arachnoid - pia mater Suzanne D'Anna 23 Dura Mater outermost layer leathery next to bony inner surface of cranium separated from arachnoid by subdural space which is fluid filled Suzanne D'Anna 24 Arachnoid middle layer looks like a cobweb Two components: - layer next to the subdural space - system of supporting fibers (trabeculae) forming web-like structure between arachnoid and pia mater Suzanne D'Anna 25 Arachnoid (cont.) in some areas, arachnoid material perforates dura mater forming protrusions called arachnoid villa Functions: - reabsorption of CSF into blood Suzanne D'Anna 26 Pia Mater innermost thin layer of loose connective tissue transparent contains many blood vessels between pia mater and nerve tissue is a thin layer of neuroglial processes firmly attached to pia mater Suzanne D'Anna 27 Meningitis inflammation of meninges serious threat to brain bacterial and viral meningitis can spread to nervous tissue of CNS Suzanne D'Anna 28 Regions of the Brain cerebrum (cerebral hemisphere ) diencephalon brain stem cerebellum Suzanne D'Anna 29 Cerebrum (cerebral hemisphere) largest, obscures most of brain stem looks like mushroom cap made up of 2 deeply grooved hemispheres - left and right Surface is covered by: - grooves - fissures or sulci - ridges - gyri or convolutions which serve as landmarks Suzanne D'Anna 30 Cerebrum (con’t) concerned with higher brain functions Contains centers for: - interpreting sensory impulses - initiating voluntary muscular movements stores information of memory utilizes information in reasoning processes functions in determining a person’s intelligence and personality Suzanne D'Anna 31 Left Hemisphere More important for: - right-hand control - spoken and written language - numerical and scientific skills - reasoning Suzanne D'Anna 32 Right Hemisphere More important for: - left-hand control - musical and artistic awareness - space and pattern perception - insight and imagination Suzanne D'Anna 33 Lobes each hemisphere is subdivided into 4 lobes named for cranial bone that covers them more precisely defined by surface landmarks, i.e., sulci and fissures Suzanne D'Anna 34 Lobes (cont.) parietal lobe occipital lobe temporal lobe frontal lobe Suzanne D'Anna 35 White Matter underlying the cortex whitish appearance is due to fatty component of myelin consists of myelinated axons extending in three principal directions - association fibers - commissural fibers - projection fibers Suzanne D'Anna 36 Association Fibers connect and transmit impulses between gyri in the same hemispheres Suzanne D'Anna 37 Commissural Fibers transmit impulses from the gyri in one cerebral hemisphere to corresponding gyri in the opposite hemisphere Suzanne D'Anna 38 Three Important Commissural Fibers corpus callosum (corpus = mass or body) - great commissure of the brain between the cerebral hemispheres anterior commissure posterior commissure Suzanne D'Anna 39 Projection Fibers form descending and ascending tracts tracts transmit impulses from cerebrum and other parts of brain to spinal cord tracts transmit impulses from spinal cord to brain Suzanne D'Anna 40 Gray Matter made primarily of densely packed neuron cell bodies basal ganglia - paired masses of gray matter - found in cerebral hemispheres cerebral cortex - layer of gray matter approx. 3 mm thick - has 6 distinct layers - divided into 3 areas based on function Suzanne D'Anna 41 Cerebral Hemisphere outer layer of gray matter is cerebral cortex - made up of lobes composed of dendrites and cell body neurons - interior is composed of white matter (nerve fibers arranged in bundles called tracts) Suzanne D'Anna 42 Functions of Cerebral Cortex divided into three main areas based on function - sensory area - motor area - association area Suzanne D'Anna 43 Sensory Areas Function in interpreting impulses, located in several lobes of cerebrum - general sensory area - primary visual area - primary auditory area - primary gustatory area - primary olfactory area Suzanne D'Anna 44 Sensory Areas primary gustatory primary auditory Suzanne D'Anna general sensory primary visual 45 General Sensory Area Receives impulses from: - the skin - muscles - internal organs localizes precisely where sensations originate located on the postcentral gryus on the occipital lobe Suzanne D'Anna 46 Primary Visual Area receives input from the eyes Interprets: - shape - color - movement located on the occipital lobes Suzanne D'Anna 47 Primary Auditory Area (cont.) receives input from internal ear (cochlea) Interprets: - pitch - rhythm located on the temporal lobes Suzanne D'Anna 48 Primary Gustatory Area receives input from taste buds Interprets: - sensations related to taste (sweet, sour, salty, bitter) located at base of postcentral gryus on parietal lobes Suzanne D'Anna 49 Primary Olfactory Area receives input from olfactory bulbs Interprets: - sensations related to smell located on temporal lobes Suzanne D'Anna 50 Motor Areas All located on frontal lobes, control actions of specific muscles or groups of muscles - primary motor area - motor speech area Suzanne D'Anna 51 Motor Areas primary motor motor speech (Broca’s) Suzanne D'Anna 52 Primary Motor Area controls muscles in specific parts of body located on precentral gyrus of frontal lobe The translation of thoughts into speech involves the motor speech area Suzanne D'Anna 53 Motor Speech Area (Broca’s Area) Coordinates complex muscular actions of the: - mouth - tongue - larynx located at junction of temporal, parietal, and occipital lobes in only one cerebral hemisphere (usually left) Suzanne D'Anna 54 Association Areas Concerned with: - personality - intelligence - emotions - reasoning - problem solving - creativity judgment Suzanne D'Anna 55 Association Areas (cont.) somatosensory association area visual association area auditory associations area (Wernick’s area) gnostic area premotor area frontal eye field Suzanne D'Anna 56 Association Areas promotor somatosensory gnostic visual frontal eye field Suzanne D'Anna auditory 57 Somatosensory Association Area integrates and interprets sensations Determines: - shape and texture of an object - orientation of one object to another as they are felt - sense relation of one body part to another stores memories, so present sensations can be compared to previous experiences Suzanne D'Anna 58 Visual Association Area relates present to past visual experiences by recognizing and evaluating what is seen located in occipital lobe Suzanne D'Anna 59 Auditory Associations Area (Wernick’s area) interprets meaning of speech determines type of sound - speech, music, and noise also interprets meaning of speech by translating words into thoughts located inferior to primary auditory area in temporal lobe Suzanne D'Anna 60 Gnostic Area (gnosis = knowledge) (NOS-tik) integrates sensory interpretations from the association areas and impulses from other areas so that a common thought can be formed - sends signals to other parts of the brain to cause appropriate response Suzanne D'Anna 61 Premotor Area anterior to primary motor area neurons from this area communicate with primary motor cortex, sensory associations areas in the parietal lobe, the basal ganglia, and the thalamus concerned with learned motor activities of complex and sequential nature such as writing or playing the piano Suzanne D'Anna 62 Frontal Eye Field in frontal cortex controls voluntary scanning movements of the eyes such as searching for a word on a page of text or dictionary Suzanne D'Anna 63 Diencephalon consists primarily of the thalamus and the hypothalamus sits on top of brain stem Suzanne D'Anna 64 Thalamus oval structure consists of paired masses of gray matter (1 inch long) organized into nuclei form lateral walls of third ventricle right and left halves are joined by bridge of gray matter called intermediate mass principal relay station allows crude recognition of sensations; pain, temperature, or pressure Suzanne D'Anna 65 Hypothalamus under thalamus single most important region of brain for maintaining homeostasis Regulates: - temperature, hunger, thirst, smell, fear, rage, sexual behavior, endocrine rhythms, and posterior and anterior pituitary secretions Suzanne D'Anna 66 Brain Stem Three parts: - midbrain - pons - medulla oblongata three inches long Suzanne D'Anna 67 Midbrain mesencephalon (meso = middle, enkephalos = brain) extends from pons to diencephalon about one inch involved with visual and auditory stimuli Suzanne D'Anna 68 Pons (pons = bridge) directly above medulla anterior to cerebellum about one inch long consists of white matter with regions of gray matter (nuclei) scattered throughout bridge connecting spinal cord with brain via transverse and longitudinal fibers helps to control respiration Suzanne D'Anna 69 Medulla Oblongata merges with spinal cord contains all ascending and descending tracts that connect spinal cord and various parts of brain contains centers that control heart rate, blood pressure, breathing, swallowing and vomiting Suzanne D'Anna 70 Cerebellum looks like a cauliflower located behind the pons and below occipital lobes of cerebrum controls subconscious skeletal muscle contractions required for smooth, coordinated movements and equilibrium “automatic pilot” second largest part of brain Suzanne D'Anna 71 Spinal Cord continuation of brain stem extends from large opening in base of cranium (foramen magnum) down to upper region of the lower back (1st lumbar vertebra) cylindrically shaped approximately 17 inches long 1 inch in diameter Suzanne D'Anna 72 Spinal Cord (cont.) Surrounded and protected by: - meninges - cerebrospinal fluid - a layer of fatty tissue - the vertebra no possibility of spinal cord injury below L4; ideal site for removal of cerebral spinal fluid Suzanne D'Anna 73