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Divisions of the Nervous System • Central Nervous System • brain • spinal cord • Peripheral Nervous System • peripheral nerves • cranial nerves • spinal nerves 10-1 CNS PNS Divisions of Peripheral Nervous System Sensory Division • picks up sensory information and delivers it to the CNS Motor Division • carries information to muscles and glands Divisions of the Motor Division • Somatic – carries information to skeletal muscle • Autonomic – carries information to smooth muscle, cardiac muscle, and glands 10-4 Divisions Nervous System 10-5 Functions of Nervous System Sensory Function • sensory receptors gather information • information is carried to the CNS Integrative Function • sensory information used to create • sensations • memory • thoughts • decisions Motor Function • decisions are acted upon • impulses are carried to effectors 10-6 sensory input motor input sensory receptor effector integration Types of Neuroglial Cells Schwann Cells • peripheral nervous system • myelinating cell Oligodendrocytes • CNS • myelinating cell Microglia • CNS • phagocytic cell Astrocytes • CNS • scar tissue • mop up excess ions, etc • induce synapse formation • connect neurons to blood vessels Ependyma • CNS • ciliated • line central canal of spinal cord • line ventricles of brain 10-11 Types of Neuroglial Cells 10-12 Neuron Structure 10-7 Regeneration of A Nerve Axon 10-13 dendrite cell body Myelin sheath axon Synapse Na+ Outside cell -70mV K+ Inside cell Myelination of Axons White Matter • contains myelinated axons Gray Matter • contains unmyelinated structures • cell bodies, dendrites 10-8 Schwann Cells Axon Nodes of Ranvier Classification of Neurons Bipolar • two processes • eyes, ears, nose Unipolar • one process • ganglia Multipolar • many processes • most neurons of CNS Classification of Neurons Sensory Neurons • afferent • carry impulse to CNS • most are unipolar • some are bipolar Interneurons • link neurons • multipolar • in CNS Motor Neurons • multipolar • carry impulses away from CNS • carry impulses to effectors 10-10 Resting Membrane Potential • inside is negative relative to the outside • polarized membrane • due to distribution of ions • Na+/K+ pump 10-14 Potential Changes • at rest membrane is polarized • threshold stimulus reached • sodium channels open and membrane depolarizes • potassium leaves cytoplasm and membrane repolarizes 10-15 Local Potential Changes • occur on membranes of dendrites and cell bodies • caused by various stimuli • chemicals • temperature changes • mechanical forces • if membrane potential becomes more negative, it has hyperpolarized • if membrane potential becomes more positive, it has depolarized • graded • summation can lead to threshold stimulus that starts an action potential 10-16 Action Potentials • nerve impulse • occur on axons • all-or-none • refractory period • absolute - time when threshold stimulus does not start another action potential • relative – time when stronger threshold stimulus can start another action potential 10-17 Action Potentials 10-18 Impulse Conduction 10-19 Ca2+ Presynaptic neuron Postsynaptic membrane Synaptic vesicles containing neurotransmitters The Synapse Nerve impulses pass from neuron to neuron at synapses 10-21 Synaptic Transmission Neurotransmitters are released when impulse reaches synaptic knob 10-22 Synaptic Potentials EPSP • excitatory postsynaptic potential • graded • depolarizes membrane of postsynaptic neuron • action potential of postsynaptic neuron becomes more likely IPSP • inhibitory postsynaptic potential • graded • hyperpolarizes membrane of postsynaptic neuron • action potential of postsynaptic neuron becomes less likely 10-23 Summation of EPSPs and IPSPs • EPSPs and IPSPs are added together in a process called summation • More EPSPs lead to greater probability of action potential 10-24 Impulse Processing Neuronal Pools • groups of interneurons that make synaptic connections with each other • interneurons work together to perform a common function • each pool receives input from other neurons • each pool generates output to other neurons 10-26 Convergence • neuron receives input from several neurons • incoming impulses represent information from different types of sensory receptors • allows nervous system to collect, process, and respond to information • makes it possible for a neuron to sum impulses from different sources 10-27 Divergence • one neuron sends impulses to several neurons • can amplify an impulse • impulse from a single neuron in CNS may be amplified to activate enough motor units needed for muscle contraction 10-28 • • • • • • • • • • • • Acetylcholine- slows heart rate; PNS Glutamate- most prevalent neurotransmitter in the brain Aspartate- in CNS GABA- inhibitory neurotransmitter Glycine- inhibitory neurotransmitter Norepinephrine- awakening from deep sleep tyrosine Epinephrine- increase heart rate Dopamine- movement of skeletal muscles Seratonin- sensory perception, temp regulation, mood, sleep Nitric oxide- may play a role in memory and learning Enkephalin- inhibit pain impulses by suppressing release of substance P Substance P- enhances perception of pain brain Coverings of the BrainMeninges skin skull dura mater arachnoid layer pia mater cerebral cortex Menenges: 1.Covers and protects CNS 2.Protects blood vessels and encloses venus sinuses 3.Contains CSF 4.Forms partition within the skull Cerebruspinal Fluid Brain Ventricles CSF Spinal Cord Rt. Ventricle Lf. Ventricle Anterior View Saggital View CSF • 150 ml in adult • contains: glucose, proteins,lactic acid, urea, cations, anions, WBC Functions: 1.Reduces wt. of brain by 97% 2.Prevents head injury 3.Supplies brain with nutrition 4.Transports hormones along ventricular channels Cerebrum Involved with higher brain functions. Processes sensory information. Initiates motor functions. Integrates information. Brain has 2 Hemispheres • Left & Right sides are separate • Corpus Callosum : major pathway between hemispheres • Some functions are ‘lateralized’ – language on left – math, music on right • Lateralization is never 100% Corpus Callosum Right Hemisphere Left Hemisphere Right-Left Specialization of the Cerebrum left side • language development • mathematical & learning capabilities • sequential thought processes right side • visual spatial skills • musical and artistic activities • intuitive abilities Corpus Callosum • Major ( but not only) pathway Medial surface of right hemisphere between sides • Connects comparable structures on each side • Permits data received on one side to be processed in both hemispheres • Aids motor coordination of left and right side Corpus Callosum Cerebrum Cross-Section cerebral cortex white matter corpus callosum basal ganglia ventricles Corpus Callosum • What happens when the corpus callosum is cut? • Sensory inputs are still crossed • Motor outputs are still crossed • Hemispheres can’t exchange data Each hemisphere is divided into 4 lobes Frontal Parietal Occipital Temporal Occipital Lobe Frontal Lobe Parietal Lobe The Cerebrum Temporal Lobe Brainstem The Brain Cerebellum cerebrum corpus callosum thalamus Pineal gland hypothalamus cerebellum pituitary pons spinal cord medulla oblongata Motor, Sensory & Association Cortex Frontal Lobe • Contains primary motor cortex No direct sensory input Important planning and sequencing areas Broca’s area for speech Prefrontal area for working memory Frontal Lobe Working Broca’s Memory Area Motor Cortex Frontal Lobe Disorders • Broca’s area – productive aphasia • Prefrontal area – lose track of ongoing context – fail to inhibit inappropriate responses • Often measured with the Wisconsin Card Sorting Task Parietal Lobe • Inputs from multiple senses contains primary somatosensory cortex borders visual & auditory cortex Outputs to Frontal lobe hand-eye coordination eye movements attention Somatosensory Parietal Cortex Lobe Temporal Lobe Contains primary auditory cortex • Inputs are auditory, visual patterns – speech recognition – face recognition – word recognition – memory formation • Outputs to limbic System, basal Ganglia, and brainstem Auditory Cortex Temporal Lobe Occipital Lobe • Input from Optic nerve • Contains primary visual cortex – most is on surface inside central fissure • Outputs to parietal and temporal lobes Occipital Lobe Visual Lobe Stages of Sleep The Limbic System The Limbic System Thalamus Relay center for sensory tracts from the spinal cord to the cerebrum. Contains centers for sensation of pain, temperature, and touch. Involved with emotions and alerting or arousal mechanisms. Midbrain and Thalamus Function Hypothalamus Regulates: • autonomic control center- blood pressure, rate and force of heart contraction, center for emotional response and behavior • body temperature • water balance and thirst • sleep/wake cycles • appetite • sexual arousal • control of endocrine functioning: Acts on the pituitary gland through the release of neurosecretions. Sensory Information sent to opposite hemisphere • Principle is Contralateral Organization • Sensory data crosses over in pathways leading to the cortex • Visual Crossover Left visual Right visual field field Optic nerves – left visual field to right hemisphere – right field to left • Other senses similar Left Visual Corpus Right Visual Cortex Callosum Cortex Midbrain Contains ascending and descending tracts to the cerebrum and thalamus. Reflex center for eye muscles. Also involved with processing visual and auditory information (connects head movements with visual and auditory stimuli). Pons Connects the two halves of the cerebellum. Regulates breathing. Medulla Oblongata • Composed of nerve tracts to and from the brain (these tracts cross over left to right and right to left) • May be regarded as an extension of the spinal cord • Almost all of the cranial nerves arise from this region Medulla Oblongata Contains control centers for many subconscious activities • Respiratory rate • Heart rate • Arteriole constriction • Swallowing • Hiccupping • Coughing • Sneezing Contralateral Motor Control • Movements controled Motor Cortex by motor area • Right hemisphere controls left side of body • Left hemisphere controls right side • Motor nerves cross sides in spinal cord Somatosensory Cortex Cerebellum Controls and coordinates muscular activity. Important in equilibrium, posture and movement. Traumatic Brain Injuries • Concussion • Contusion • Subdural or subarachnoid hemorrhage • Contrecoup injury • Punch Drunk Syndrome Cerebrovascular Accidents (CVAs) • • • • • Ischemia Thrombus Embolism Arteriosclerosis Stroke Stroke Degenerative brain diseases • • • • • • • Alzheimer’s Down’s Parkinson’s Huntington’s Chorea MS Epilepsy Schizophrenia PET Scans F-Dopa deficiency Peripheral Nervous System cranial nerves - 12 pr spinal nerves31 pr Cranial Nerves Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Accessory Hypoglossal Cranial Nerves On Old Olympus Towering Tops A Fat Voracious German Viewed A Hop 1. 2. 3. 4. 5. Olfactory- smell Optic- vision Oculomotor- 4 of the 6 extrinsic eye muscles Trochlear- extrinsic eye muscles Trigeminal- sensory fibers to the face and motor fibers to the chewing muscles 6. Abducens- controls eye muscles that turn the eye laterally 7. Facial- facial expression 8. Vestibulocochlear- hearing and balance 9. Glosopharyngeal- tongue and pharynx 10.Vagus- from medulla- acetylcholine slows heart & breathing 11.Accessory- accessory part of vagus nerve 12.Hypoglossal- moves muscles under tongue Peripheral Nervous System Peripheral Nervous System Skeletal (Somatic) Autonomic Sympathetic Parasympathetic The Spinal Cord The Spinal Cord white matter dorsal root ventral root spinal nerves grey matter pia mater arachnoid dura mater Nerve Pathways into the Spinal Cord sensory pathway motor pathway The Spinal Cord vertebra spinal cord spinal nerve interneuron motor neuron Spinal Reflex Arc sensory neuron motor neuron stretch receptor patellar ligament Spinal Nerves cervical cervical nerves thoracic thoracic nerves cauda equina lumbar nerves sacral nerves coccygeal nerves Peripheral Nervous System • 3 kinds of neurons connect CNS to the body – sensory – motor – interneurons • Motor - CNS to muscles and organs • Sensory - sensory receptors to CNS • Interneurons: Connections Within CNS Brain Spinal Cord Nerves Somatic System • Nerves to/from spinal cord – control muscle movements – somatosensory inputs Brain Sensory Neuron • Both Voluntary and reflex movements • Skeletal Reflexes Skin receptors – simplest is spinal reflex arc Motor Neuron Interneuron Muscle Autonomic System • Two divisions: – sympathetic – Parasympatheitic • Control involuntary functions – – – – – heartbeat blood pressure respiration perspiration digestion • Can be influenced by thought and emotion Sympathetic Division neurotransmitter is norepinephrine, fight or flight E = exercise, excitement, emergency, and embarrassment Parasympathetic Division neurotransmitter is acetylcholine D = digestion, deification, diuresis (urinating) Summary of autonomic differences Autonomic nervous system controls physiological arousal Sympathetic division (arousing) Pupils dilate Decreases Parasympathetic division (calming) EYES Pupils contract SALVATION Increases Perspires SKIN Dries Increases RESPERATION Decreases Accelerates HEART Slows Inhibits DIGESTION Activates Secrete stress hormones ADRENAL GLANDS Decrease secretion of stress hormones 1. 2. 3. 4. 5. 6. 7. 8. 9. INQUIRY What voltage is the threshold potential? Describe depolarization, repolarization and hyperpolarization. What layer of tissue adheres most tightly to the brain? CFS stands for-------. What does it do? What does the thalamus do? Where is dark matter located in the spinal cord? What disease is characterized by myelin sheath degeneration? A thrombus that moves to a new site is called ----.