Chapter 12,13: Intro to Nervous System and CNS, The Brain
Chapter 12,13: Intro to Nervous System and CNS, The Brain BIOL 103 - 54
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Date Created: 10/30/15
Unit 31 Intro to Nervous System and CNS Nervous system master controlling and communicating system of the body o Composed mostly of nervous tissue 0 Consists of the brain spinal cord nerves and ganglia 0 Two types of cells 0 Neuron o Glial cell 0 Functions basic and overlapping o Sensory collects information I Receptors monitor stimuli in external and internal environments 0 Integrative processes evaluates and interprets determines a response 0 Motor response I Effectors cells that receive impulses o Muscles and glands Structural and Functional Divisions of the Nervous System Nervous system organization I Anatomic components Description Structural Divisions Central nervous system Brain amp spinal cord Integration and control CNS center Peripheral nervous system Spinal amp cranial nerves Sends and receives PNS information from CNS Functional Divisions Sensory nervous system o Somatic sensory 0 Skin skeletal muscles 0 Convey impulses from and joints skin skeletal muscles and joints to CNS 0 Visceral organ sensory o Visceral organs 0 Convey impulses from visceral organ to CNS Motor nervous system o Somatic motor SNS o Skeletal muscles 0 Sends voluntary signals to skeletal muscles 0 Autonomic motor 0 Heart smooth 0 Sends involuntary ANS muscles and glands commands to heart cardiac muscle smooth muscle and glands Cells neurons glial cells 0 Glial cells 0 In the CNS I Astrocytes anchor neurons to nearby vessels support and brace neurons controls chemical environment 0 quotastroquot means star and astrocytes have projections in all directions like a star I Microglia eats the bad guys or invaders in the nervous system defensive cells phagocytes I Ependymal line the central cavities of brain and spinal cord produce CSF cerebrospinal fluid have cilia to help circulate CSF I Oligodendrocytes branched cells that wrap around axons of neurons myelination o In the PNS I Schwann cells surround axons of neurons produce myelin sheaths 20 30 layers myelination I Satellite cells surrounds and insulates neuron bodies 0 Myelin o A fat 0 Protects and insulates the axons I Increases the nerve impulse 0 Multiple Sclerosis o Demyelinating disease breaks open Schwann cells 0 Loss of coordination o Slower responses 0 This is why Neuron 0 Characteristics Excitability responsiveness to stimuli responds immediately Conductivity transmission of electrical charge the ability to travel Secretion release of chemical to allow transmission of signal Amitotic nondividing Longliving OOOO 0 Anatomy of neuron 0 Body soma I Includes the nucleus typical organelles and a plasma membrane 39 Nucei CNS I Ganglia PNS I Takes an impulse away from the cell body I Axon hillock triangular region of soma where the axon attaches to the ceHbody I Axon terminal terminal branches on the distal end of axons and their collateral branches 0 Dendrite receives input and brings information into the cell body 0 Myelin o Neuron classification 0 Structuralclassification I Unipolar has one axon extended from soma axon splits into two processes central and peripheral processes I Bipolar has one axon and one dendrite extended from soma one in each direction I Multipolar has many dendrites most common types has one axon extended from soma 0 Functional classification based on direction the signal travels relative to the central nervous system I Sensory afferent conduct sensory input from somatic sensory and visceral sensory receptors to CNS most are unipolar I Motor efferent conduct motor output from CNS to somatic and visceral effectors mostly multipolar I Interneuron receive process and integrate information from many other neurons generally multipolar NERVE a bundle of parallel axons in the PNS 0 Anatomy of a nerve o Epineurium thick layer of dense irregular connective tissue that encloses entire nerve o Perineurium layer of dense irregular connective tissue that wraps fascicle small bundle of axons in the nerve o Endoneurium delicate layer of areolar connective tissue that wraps an individual axon separates and electrically insulates each axon 0 Structural classification of nerves based on CNS component from which the nerve extends o Cranial extend from the brain 0 Spinal extend from the spinal cord 0 Functional classification of nerves 0 Sensory contain sensory neurons ending signals to CNS 0 Motor contain motor neurons sending signals from CNS 0 Mixed nerves contain both sensory and motor neurons I Most named nerves are in this category I Individual axons in these nerves transmit only one type of information Unit 32 The Brain 0 Terms 0 Nerve bundle of axons found only in PNS o Tract bundle of axons found only in CNS white matter 0 Ganglion bundle of cell bodies found only in PNS o Nucleus bundle of cell bodies found only in CNS gray matter 0 Innervation to supply an organ or other body part with nerves for movement and sensation 0 Protection of CNS 0 The skull and vertebrae o Meninges o Cerebrospinal fluid CSF SCALP o w Skin Connective tissue Aponeurosis Loose areolar tissue Eeriosteum o Meninges 3 layers of connective tissue Cover and protect the CNS 0 Enclose and protect the vessels supplying the brain 0 Contain and circulate the cerebrospinal fluid CSF o w I Dura Mater first layer 0 Strongest 0 Has two layers of dense connective tissue that are fused together except to enclose the Dural sinus o Falx Cerebri separates cerebrum o Falx Cerebelli separates cerebellum o Tentorium Cerebelli the tent over the cerebellum separates occipital and temporal lobes of cerebellum I Arachnoid Mater second layer 0 Has subdural space potential space between dura and arachnoid mater 0 Has subarachnoid space filled with CSF contains the blood vessels that supply the brain 0 Has arachnoid villi allows CSF to pass into the Dural blood sinuses act as one way valves I Pia Mater third layer 0 Delicate connective tissue 0 Clings tightly to the surface of the brian o Considered part of brain outermost part 0 Dural sinuses o Pathway I Superior Sagittal sinus 9 L amp R Transverse sinuses 9 Sigmoid sinus 9 becomes the Internal Jugular Vein o Cerebrospinal fluid a clear colorless fluid Fluidform of protection for the spinal cord Allows the brain to weigh quite as much Stabilizes CNS environment Formed by choroid plexus Continuously formed and reabsorbed Pathway to CSF I Choroid plexus of ventricles 9 lateral ventricles 9 third ventricle 9 fourth ventricle 00000 9 subarachnoid space 9 central canal of spinal cord 0 Excess CSF flows into arachnoid villi and drains into Dural venous sinuses BRAIN o Consists of billions of neurons and glial cells 0 Different regions are specialized for different functions 0 Four major regions 0 Cerebrum main chunk o Diencephalon small region inside brain 0 Brainstem goes from diencephalon to cerebellum o Cerebellum inferior to occipital lobe o Forebrain Cerebral hemispheres Diencephalon o Cerebrum I 83 of brain mass I Cerebral Hemispheres 0 White matter tracts connect the hemispheres 0 Two hemispheres Controls muscles on the opposite side of the body Right interprets what we see and touch tactile sensation involved in nonverbal memory sound and smell 0 Left language interpretation reading and writing I Three regions outer cortex inner white matter and basal nuclei 0 Has five lobes o Frontal two parietal occipital and two temporal lobes I Diencephalon thalamus and hypothalamus 0 Provides relays and switching centers for sensory motor visceral pathways acts as a relay center such as a 4x4 in track where runners pass the baton to each other 0 Pineal gland 0 Collection of nuclei bundles 0 Gateway to cerebral cortex 0 Responsible for melatonin o Thalamus o Nuclei bundles 0 Gateway to cerebral cortex o Receives and relays signals 0 Hypothalamus 0 Control of autonomic nervous system I Influences heart rate blood pressure digestive activities respiration Controls endocrine system Emotional behaviorresponses Regulates hunger and thirst circadian rhythms and body temperature 0000 Pituitary gland I Endoc ne I Hormone secretion 0 Mammillary bodies I Cerebral Cortex 0 Process voluntary behaviors and sensations o Enables us to 0 Be aware of ourselves and our sensations 0 Communicate o Fissures Gyri and Sulci in Cerebral Hemispheres o Fissures I Transverse fissure separate cerebrum and cerebellum I Longitudinal fissure separates cerebral hemispheres o Sulci grooves on the surface of the cerebral hemispheres I Separates frontal and parietal lobes I Bordered by two gyri I Lateral sulcus separates temporal lobe from parietal and frontal lobes 0 EM twisted ridges between sulci 0 Functional Parts of the Cerebrum 0 Motor Areas housed within frontal lobes I Primary motor cortex somatic motor area 0 Located in precentral gyrus 0 Controls skeletal muscle activity on opposite side of body I Premotor cortex somatic motor association area 0 Located anterior to primary cortex 0 Coordinates learned skilled activities 0 Motor speech area Broca s area I Speech production I Controls muscular movements for vocalization and breathing regulation I Linked to Wernicke s area 0 Production of written and spoken language 0 Sensory areas I Primary somatosensory cortex 0 Postcentral gyrus o Receives somatic sensory information from receptors proprioceptors touch pressure pain temperature receptors I Primary visual cortex 0 Occipital lobe I Primary auditory cortex 0 Temporal lobe o MIDBRAIN proximal brainstem 0 Features I Corpora quadrigemina four bodies 0 Has a large nuclei 0 Responsible for auditory and visual processing 0 Has two superior and two inferior colliculi I Cerebral peduncles small foot process 0 Tracts connect midbrain to brainstem I Cerebral aquaduct o A channel through the midbrain o Connects third ventricle to fourth ventricle o HINDBRAIN distal brainstem cerebellum o Medulla oblongata I Most inferior part of the brain I Continuous with the spinal cord I Has two pyramids o Ventral side of medulla o Tracts that carry motor output I Has cranial nerves not spinal nerves 0 Pons I Bridge between midbrain and medulla oblongata I Helps to regulate breathing based off of what nerves come off of it o Cerebellum 11 of bran mass I Helps to coordinate body movement and cognition I Contains an arbor vitae internal white matter I Contains cortex outer gray matter SPINAL CORD part of CNS 0 Runs through the vertebral canal vertebral foramen 0 Has one layer of dura mater 0 Features 0 Conus medullaris the inferior end of the spinal cord 0 Cauda equine collection of nerve roots 0 Filum terminale long filament of connective tissue attaches to coccyx inferiorly o Cervical and lumbar enlargements where nerves for upper and lower limbs arise 0 Two deep grooves run the length of the cord o Posterior dorsal medial sulcus o Anterior ventral median fissure 0 Central Canal narrow central opening in spinal cord 0 Gray matter and nerve roots 0 Anterior ventral horns contain cell bodies of motor neurons More motor 0 Posterior dorsal horns consist of interneuron cell bodies More sensory o 31 pairs of spinal nerves Connected by dorsal and ventral roots PNS structures Intervertebral foramen 0 Structural Components of the CNS 0 Cranial nerves Part of PNS originating from brain Number with Roman numerals according to their position 0 Begin most anteriorly CN I Olfactory 0 Controls sense of smell sensory CN II Optic 0 Controls sense of vision sensory CN III Oculomotor 0 Controls muscles that move eye lift eyelid change pupil diameter motor CN IV Trochlear 0 Controls superior oblique eye muscle motor CN V Trigeminal 0 Controls somatic sensation from face and chewing movements sensory and motor CN VI Abducens 0 Controls lateral rectus muscle that abducts eye motor CN VII Facial 0 Controls muscles of facial expression and provides signals for taste from tongue motor and sensory CN VIII Vestibulocochlear 0 Controls senses of hearing and equilibrium sensory CN IX Glossopharyngeal 0 Controls taste and touch from tongue control of pharynx muscle sensory and motor CN X Vagus 0 Control visceral sensation parasympathetic nerve to many organs of the body sensory and slightly motor CN XI Spinal Accessory 0 Controls muscles of neck and pharynx motor I CN XII Hypoglossal 0 Controls tongue muscles motor