Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Nervous system Ch. 9 The basics Divide in 2 areas Central Nervous system Brain & spinal cord Peripheral Nervous system Motor & sensory nerves outside the spinal cord. Nervous Tissue Cell Types Neuroglial cells( glial cells) -non-conducting -support neurons Produce myelin “insulation” act as phagocytes out number neurons 10:1 Aid in circulation of CSF Types Astrocyte: framework for brain/connects vessles Ependymal cells: circulate CSF Microglial: wandering cells/phagocytosis Oligodendrocyte: CNS myelin sheath Schwann cells: PNS myelin sheath Structures Neurons functional & Structural units of the N.S. 1. Cell Body aka: Soma Contains: Cytoplasm Cell membrane nucleus neurofibrils ( thin threads extend into axon) nissl bodies “spots” 2. Dendrites 3. Axon Highly branched Receives & conducts impulses towards cell body single uniform cylindrical fiber connected at axonal hillock to body carries impulse away from body end has a synaptic Knob that communicates to other nerves/tissues across the synaptic cleft. axons Axons may be: 1. Myelinated Myelin Sheath gives protective covering made of _schwann cells increases speed of nerve impulse impulse jumps gaps: nodes of Ranvier “White matter” brain exterior spinal cord PNS neurons 2.Unmylenated “grey matter” brain & spinal cord Structure cont. Neurilemma -thin outer layer of Myelin sheath Portion of Schwann cell that has most of the cytoplasm& nuclei -role in repair -most brain & spinal cord neurons lack this Structural Classification of Neurons 1. Unipolar Neurons Single process extending from body 2 branches function as a single axon peripheral process-dendrites central process- enters CNS may form groups called ganglia located outside the CNS Structural Classification of Neurons 2. Bipolar Neuron cell body has 2 processes 1 axon & 1 dendrite found in specialized parts of ears, nose & eyes Structural Classification of Neurons 3. Multipolar Neurons cell body has many processes (dendrites) only 1 axon most common in brain & spinal cord Functional Classification of Neurons Sensory Neurons aka: afferent 1. transmit impulses from receptors toward CNS Most are unipolar Peripheral Nervous system (PNS) 2. Interneurons Aka:association links neurons to direct incoming sensory information most abundant located in brain & spinal cord ( CNS) multipolar Functional Classification of Neurons 3. Motor Neurons Aka: effectors transmit impulses away from the CNS to effector multipolar speed up or slow down muscle action voluntary or involuntary control PNS How they work together Sensory neuron CNS Sensory receptor signal Interneuron PNS In spinal cord Motor neuron Muscle “effector” How they work together How it works http://highered.mcgrawhill.com/sites/0072437316/student_view0/ chapter45/animations.html Nerve Impulse & Transmission 1. Nerve transmission a. b. Slower than electrical current ( .5-120 m/s vs. 3x105 km/s) Self propagating electrochemical current Nerve Impulse & Transmission 2. Cell membrane (Axon) a. b. c. d. Electrically charged –polarized Polarization due to unequal distribution of +/- ions across membrane Inside more negatively charged Causes electrical gradient or potential difference Nerve Impulse & Transmission 3. Ions a. Intracellular Phosphates & sulfates (anions or – ions) Potassium( K+) cation membrane very permeable to K+ K+ diffuses out of cell b. extracellular Sodium ( Na+) membrane slightly permeable to Na+ diffuses into cell c. ion pumps (Na-K) move ions in and out of cell Nerve Impulse & Transmission 4. Resting or membrane potential a. b. c. Nerve that is resting-is not being stimulated K+ leaves faster than Na+ enters causing slight + charge outside of cell. ATP used to actively transport + ions back into cell to maintain concentration gradient. http://bcs.whfreeman.com/thelifewire/content/chp44/4401s.swf Nerve Impulse & Transmission 5. Action Potential or Nerve Impulse a. Cell membrane becomes depolarized by stimulus b. Stimulus= depolarization c. stimulus must reach threshold to create impulse d. axons only part capable of A.P. e. electrical current flows short distance triggering adjacent membrane to continue impulse Nerve Impulse & Transmission 6. How it works a. b. c. d. Threshold stimulus received by neuron Na+ flows inward = depolarizing membrane Causing K+= to flow outward= repolarizing membrane Chain reaction continues down axon carrying impulse http://outreach.mcb.harvard.edu/animations/actionpotential.swf Nerve Impulse & Transmission 7. Refractory period a. b. After impulse when threshold stimulus cannot trigger another impulse: 1/2500 second= Absolute refractory membrane is returning to resting potential= relative refractory can be stimulated with high intensity stimulus c. limits # of A.P. that can be generated=usually 100 impulses/s Nerve Impulse & Transmission 8. All-or – None a. Neuron responds completely b. Stronger impulse= more impulses /second not a stronger impulse Nerve Impulse & Transmission 9. Speed of impulse a. Unmyelinated axons Impulse carried through entire membrane surface b. Myelinated axons A.P only occurs at Nodes Appears to jump= faster impulse Saltitory conduction c. diameter of axon diameter= speed thick myelinated skeletal motor nerve= 120m/s thin umyelinated skin sensory nerve= .5 m/s http://www.blackwellpublishing.com/matthews/actionp.html Mylenation and diameter determine speed of conduction Nerve Impulse & Transmission 10.The Synapse a. Ca+ enters Presynaptic neuron causing it to releases neurotransmitter into the synaptic cleft b. Neurotransmitter will either excite or inhibit the Postsynaptic neuron or effector http://www.bishopstopford.com/faculties/science/arthur/synapse.swf http://bcs.whfreeman.com/thelifewire/content/chp44/4403s.swf Reflexes simple automatic responses to stimuli from inside or outside the body (involve CNS & PNS) simplest type of nerve pathway carry out involuntary responses breathing heart rate blood pressure digestion swallowing sneezing blinking coughing vomiting…… maintain homeostasis Types Monosynaptic = 1 synapse Simple or stretch reflex 1 sensory + 1 motor neuron involved Patellar reflex: helps with upright posture types ouch Withdrawal reflex protective reflex involving 3 neurons sensory, interneuron, & motor neurons Interneuron initiates withdrawal then sends impulse to brain for interpretation PNS CNS Figure 09.20 Reflex animation http://www.sumanasinc.com/webcontent/ animations/content/reflexarcs2.html http://bcs.whfreeman.com/thelifewire/con tent/chp46/46020.html Menengies (membranes) 3 Layers that cover the CNS protection & contain Cerebrospinal fluid (CSF) Dura mater: outer most layer - Tough, white, dense connective tissue - Many blood vessels & nerves Arachnoid mater: Thin web like membrane Lacks blood vessels Subarachnoid space: contain CSF Pia Mater: very thin & has many nerves/vessels Nourish CNS Attached to surface of brain & cord Figure 09.21 Cerebrospinal fluid Made in the ventricles (cavities) of brain 500mL secreted daily, only 140mL in NS, continually reabsorbed into blood clear, somewhat viscid nourish & protect CNS maintain stable ionic concentrations sensory feedback about internal environment. Spinal cord Spinal Cord Structure Part of CNS foramen magnum to L1&L2 31 pair of spinal nerves ends at cauda equina (horses tail) & filum terminale (coccyx) Cervical enlargement: nerves to arms Lumbar enlargement: nerves to legs Spinal cord Function: 1. Conducting nerve impulses 2. Center for spinal reflexes 1. Somatic reflexes: skeletal muscle Patellar & Withdrawal 2. Visceral reflexes: stimulate or inhibit visceral organs breathing, heart rate… Grey matter: unmyelinated fibers ( H) Posterior horns: sensory Anterior horns: motor White matter: myelinated fibers Anterior, posterior & lateral form nerve tracts Grey Commissure: connects horns at center of cord Central canal: within the grey commissure & contains CSF Two tracts: Ascending tracts: sensory information to brain Descending tracts: motor impulses to muscle/glands The brain Complete lab 27 & 29 Brain Structure Cerebrum largest part 2 hemispheres connected by corpus callosum & seperated by falx cerebri convolutions-gyri Shallow = sulcus divide brain into 4 Lobes Frontal Lobe: voluntary skeletal muscle, higher intellectual processes, concentration Broca’s Area: motor speech area Parietal lobe: Temp. touch, pressure pain of skin, understand speech, word expression of thought & feelings Temporal Lobe: hearing, interpretation of sensory info, music patterns Occipital lobe: vision, combine visual and sensory information Deep =fissure -Longitudinal Fissure = Left & right sides -Transverse Fissure = cerebrum & cerebellum Association Areas Association areas Hemisphere Dominance 90 % population Left side Dominant( Right handed) language related activities: reading, writing, verbal , analytical & computations Non-dominant: non verbal functions, spacial orientation, music interpretation, visual, emotional and intuition Corpus callosum allows Hemi’s to communicate/coordinate Diencephalon: located between cerebral hemi’s & above midbrain Contains Thalamus & hypothalamus Attaches Pineal & pituitary glands Mammilary body Optic chiasma/tracts infandibulum Brain Stem Connects brain to cord Mostly Grey matter 3 parts Midbrain, pons medulla Oblongata Mid Brain ( reflex center) Between diencephalon & pons Visual center: moves eyes when head turns Auditory center: moves head to hear sound Red nucleus: communicates w/ cerebellum & cord to coordinate posture Pons( relay station) -rounded bulge underside of brain stem-bridges cerebrum & cerebellum -relay impulses from medulla/cerebrum -relay sensory impulses to higher brain centers -assist in regulation, depth & rate of breathing Medulla Oblongata (vital reflexes) -enlargement of spinal cord at foramen Magnum -All ascending & descending tracts pass through -injury usually Fatal Visceral reflex center Cardiac center: Heart Rate Vasomotor Canter: Blood Pressure Respiratory center: rate, rhythm & depth -non-vital reflexes -Coughing - vomiting -Swallowing - Sneezing Cerebellum“ hind Brain” Mostly white matter w/ grey matter cortex Tree like structure posterior to brain stem, inferior to Cerebrum Proprioception Center -position of body, actual & desired - coordination of skeletal muscle pattern Closed brain injury Figure 09.27b Figure 09.34 Cranial Nerves Considered part of Peripheral nervous system 12 pair Name & Roman Numeral Originate form Brain stem Motor, sensory & mixed Cranial Nerves Cranial nerves Nerve function S Sense of smell II. Optic S Sense of sight III. Oculomotor B Movement of eye (pupil), IV. Trochlear B Eye movement V. Trigeminal B Face sensation, chewing VI. Abducens B Eye movement VII. Facial B Taste, facial expression, tear/salivary glands VIII. Vestibulocochlear S Hearing/equilibrium IX. Glossopharyngeal B Taste, pharynx, throat sensation X. Vagus B Speech, swallowing, HR, peristalsis & visceral sensation XI. Accessory M Speech, swallowing, head/shoulder movement XII> Hypoglossal M Tongue movement I. Olfactory receptor type (auditory) S= sensory, M= motor B= both mnemonics Nerve nerve name nerve type I.Olfactory on some II. Optic old say III. Oculomotor olympus’ betroth IV. Trochlear towering beauty V. Trigeminal top but VI. Abducens a big VII. Facial fin brother VIII. Vestibulocochlear and says (auditory) IX. Glossopharyngeal german better X. Vagus viewed bet XI. Accessory a marry hop money XII. Hypoglossal Cranial nerve injury Spinal Nerves 31 pair, all mixed Anterior (motor) & Posterior ( sensory) roots join outside spinal column. Named for location 8 cervical, 12 thoracic, 5 lumbar, 5 sacral & 1 coccygeal. Peripheral Nervous System Consists of cranial & spinal nerves 2 major divisions Somatic (voluntary) system Autonomic( involuntary) system PNS Somatic autonomic Somatic N.S. Receptors Sensory nerves Afferent fibers Take messages to CNS/brain Motor Nerves Efferent fibers Impulses to muscles/glands ( effectors) Mixed nerves Contain both motor & sensory fibers Autonomic NS Controls homeostasis Divided into 2 divisions Works as antagonistic system autonomic sympathetic parasympathetic Sympathetic division AKA thoracolumbar division Activates adrenaline responses “ fight or flight” ( pain/fear/anger) Pupil dilation Heart rate circulation to limbs respiration… Parasympathetic division AKA Craniosacral division Deactivates sympathetic responses Returns system to “normal” Pupil constriction Decrease, HR, respiration…. Nervous system CNS Brain Spinal cord somatic “voluntary” Cranial & spinal nerves Motor, sensory , both Sympathetic PNS Peripheral nerves Cranial & spinal nerves autonomic “involuntary” Maintains homeostasis Antagonist system parasympathetic “speeds up” “slows down”=parachute Fight or flight Deactivates sympathetic division Pain/fear/anger Thoracolumbar division Returns system to “normal” Craniosacral division