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Functions of the Nervous System Sensory senses stimuli from both within the body and from the external environment The NERVOUS System Integrative analyzes, interprets, and stores information about the stimuli it has receives from the sensory portion of the nervous system Motor responds to stimuli by some type of action muscular contraction glandular secretion Divisions of the Nervous System Nervous System Schematic Central Nervous System (CNS) Peripheral Nervous System (PNS) Somatic Nervous System (SNS) Autonomic Nervous System (ANS) Sympathetic Division Parasympathetic Division Nervous System Schematic Nervous System Schematic 1 1 The Central Nervous System Consists of the brain and the spinal cord Sorts incoming sensory information Generates thoughts and emotions Forms and stores memories Stimulates muscle contractions Stimulates glandular secretions The Peripheral Nervous System Connects sensory receptors, muscles, and glands in the peripheral parts of the body to the central nervous system Consists of cranial and spinal nerves Afferent Neurons (Sensory) conduct nerve impulses from sensory receptors toward the CNS Efferent Neurons (Motor) conduct nerve impulses from the CNS to muscles and glands Consists of the somatic and autonomic systems The Somatic Nervous System The Autonomic Nervous System Made up of sensory neurons that convey information from the cutaneous and special sense receptors in the head, body wall, and extremities to the CNS Contains sensory neurons mainly from the viscera that convey information to the CNS Also contains the motor neurons from the CNS that conduct impulses to the skeletal muscles Unconscious control Contains the efferent neurons that conduct impulses to smooth muscle, cardiac muscle, and glands Divisions include: Sympathetic nervous system Parasympathetic nervous system Sympathetic Division Sympathetic Division— “Fight or Flight” Cope with stress or emergency situations Increase in heart rate, blood glucose levels, breathing rate Pupils dilate Increased blood flow to muscles, lungs, heart Reduced digestive activity due to decreased blood flow to visceral organs Parasympathetic Division Parasympathetic Division— “Rest and Relaxation” Helps body return to homeostasis Decrease in heart rate, breathing rate, and blood glucose levels Reduced blood flow to skeletal muscle Increased digestive activity due to increased blood flow to visceral organs 2 2 Activity Directions: Choose the responses that best correspond to the descriptions provided in the following statements. Insert the appropriate letter in the answer blanks. A. Autonomic Nervous System C. Peripheral Nervous System B. Central Nervous System D. Somatic Nervous System ________________1. Nervous System subdivision that is composed of the brain and spinal cord. ________________2. Subdivision of the PNS that controls voluntary activities. Neurons The nerve cells responsible for the special functions of the nervous system sensing remembering thinking controlling muscle activity controlling glandular secretions Synapse - the functional relay points between two neurons or between a neuron and an effector organ Neuromuscular Junction Neuroglandular Junction ________________3. Nervous system subdivision that is composed of the cranial and spinal nerves. ________________4. Subdivision of the PNS that regulates the activity of the heart and smooth muscle (involuntary). Parts of A Neuron Neuron Cell Body (Soma or Perikaryon) nucleus, cytoplasm, organelles of a neuron Dendrites - tapered, highly branched processes protruding from the cell body usually very short AFFERENT FUNCTION Axons - long, thin, cylindrical process usually myelinated EFFERENT FUNCTION Neurons Neuroglia Nervous system cells that support, nurture and protect the neurons Types of Neuroglia found in the CNS Astrocytes Oligodendrocytes Microglia Ependymal Cells Types of Neuroglia found in the PNS Neurolemmocytes (Schwann Cells) 3 3 Neuroglia of the CNS Astrocytes Star-shaped cells with many processes Participate in metabolism of neurotransmitters Maintain K+ balance for generation of nervous impulses Participate in brain development Help form the blood brain barrier Provide a link between neurons and blood vessels Astrocyte Oligodendrocytes Small cells with few processes Form a supporting network around the neurons by twining around neurons and producing a lipid and protein wrapping around the neurons (myelin sheath) Microglia Small phagocytic cells that protect the central nervous system by engulfing and invading microbes Clears away debris from dead cells Ependymal Cells Neuroglia cells that line the brain ventricles Line the central canal of the spinal cord Helps form and circulate cerebral spinal fluid Help form the blood-CSF barrier (different from the blood-brain barrier) 4 4 Ependymal Cells Neuroglia of the PNS Schwann Cells - Neurolemmocytes Cells responsible for producing the myelin sheaths around the PNS neurons Schwann Cell (Neurolemmocyte) Neuroglia Overview Myelination Myelination The process of developing or producing a Myelin Sheath Insulates the axon of a neuron Increases the speed of nerve impulse conduction CNS - oligodendrocytes PNS - neurolemmocytes (Schwann Cells) Diseases such as Tay-Sachs disease and Multiple Sclerosis involve destruction of the myelin sheaths around the nerve 5 5 Unmyelinated Axon Myelinated Axon Activity Activity Match the anatomical terms that best correspond to the following statements. Place the correct letter in the answer blanks. Match the anatomical terms that best correspond to the following statements. Place the correct letter in the answer blanks. A. Axon A. Axon D. Myelin Sheath B. Axon Bulb E. Cell Body D. Myelin Sheath B. Axon Bulb E. Cell Body C. Dendrite C. Dendrite __________1. Releases neurotransmitters ____B_____1. Releases neurotransmitters __________2. Directs messages toward the cell body ____C_____2. Directs messages toward the cell body __________3. Increases the speed of the message ____D_____3. Increases the speed of the message __________4. Location of the nucleus ____E_____4. Location of the nucleus __________5. Long extension that takes messages to the target ____A_____5. Long extension that takes messages to the target Transmission of Nerve Impulses Nerve Impulse: An electrical event due to movement of ions across a membrane Neurophysiology The transmission of nerve (electrical) impulses from nervous tissue to other nervous tissue, organs, glands, and muscles. Also called an action potential Lasts about 1 msec (1/1000 of a second) Dependent upon diameter of the axon larger diameter axons - 0.4 msec (1/2500 sec) 2500 impulses per second smaller diameter axons - 4 msec (1/250 sec) 250 impulses per second 6 6 All or None Principle Neuron Membrane Potential If depolarization reaches a threshold, an action potential (impulse) is conducted Each action potential (impulse) is conducted at maximum strength unless there are toxic materials within the cell or the membrane has been disrupted Neuron Action Potential Action Potential Resting phase (polarization) The axon is not actively conducting nerve impulses. Sodium is the ion found in the greatest concentration in the extracellular fluid. Potassium is the ion found in the greatest concentration in the intracellular fluid. The outside charge of the polarized membrane is positive while the inside charge of the polarized membrane is negative. Depolarization phase As the action potential propagates down the length of the axon, the sodium channels open in the axon membrane. Sodium, which is found in greater concentration in the extracellular fluid, rushes through the protein channels creating a negative charge in the extracellular fluid and a positive charge in the intracellular fluid. Repolarization phase Just split seconds after the opening of the sodium channels, the potassium channels in the axon membrane open. Since potassium is found in greater concentration within the cell, potassium ions rush outward. This flow of positively charged ions restores the positive charge outside of the cell and the negative charge inside of the cell. Refractory period During this period of time, no nerve impulses (action potentials) can be sent. The sodium-potassium pump (using ATP) functions to restore the ion concentration of the polarized cell by pumping sodium ions out of the cell and bringing potassium ions into the cell. Neuron Impulse Neuron Action Potential 7 7 Types of Impulse Conduction Nerve Conduction Continuous Conduction - step by step depolarization of each sequential, adjacent area of of the nerve cell membrane typical of unmyelinated nerve fibers type of action potential in muscle fibers Saltatory Conduction - the jumping of an action potential across specialized neurofibril nodes along the axon Nodes of Ranvier Nerve Conduction—Myelinated Axon Transmission of Nerve Impulses at Synapses Most nervous conduction is from neuron to neuron (interneurons - 90%) Types of Synapses Axon to dendrite Axon to soma Axon to axon Two ways to transmit impulses across a synapse Electrical Synapses Chemical Synapses Reflexes Fast, predictable, automatic responses to changes in the environment that help maintain homeostasis Somatic Reflexes - involve skeletal muscles Visceral (Autonomic) Reflexes - involve responses of smooth muscles, the heart, and glands Involve the spinal nerves The Reflex Arc A response by the body involving only the body segment being affected and the spinal cord Brain does not have to be involved Receptor - the distal end of a sensory neuron (dendrite) Responds to a specific stimulus a change in internal or external environment Triggers a nerve impulse 8 8 Receptor - the distal end of a sensory neuron (dendrite) Responds to a specific stimulus a change in internal or external environment The Reflex Arc Triggers a nerve impulse Sensory Neuron - the neuron located in the gray matter of the spinal cord conducts impulses from the receptor to the spinal cord Integrating Center - a region within the CNS (spinal cord or brain) that interprets the information from the sensory neuron and initiates an appropriate response Motor Neurons - the neurons arising from the integrating center that relay a nerve impulse to the part of the body that will respond to the stimulus Effector - the part of the body that responds to the motor nerve impulse (usually a muscle or a gland) Effector - skeletal muscle - somatic reflex Effector - cardiac, smooth muscle, or gland -visceral reflex Reflex Arc Examples Tendon Reflex Stretch Reflex - results in the contraction of a muscle if it has been stretched suddenly Tendon Reflex - results in the contraction of a muscle when a tendon is stretched suddenly Flexor (Withdrawal) Reflex - sudden contraction and removal of a body segment as a result of a pain stimulus Withdrawal Reflex Also called the Flexor/Withdrawal Reflex Spinal Nerves Also called nerve roots Branch off the spinal cord and pass out through the vertebral foramen Carry information from the spinal cord to the rest of the body, and from the body back up to the brain. Four main groups of spinal nerves, which exit different levels of the spinal cord: Cervical Nerves "C" : (nerves in the neck) supply movement and feeling to the arms, neck and upper trunk. Also control breathing. Thoracic Nerves "T" : (nerves in the upper back) supply the trunk and abdomen. Lumbar Nerves "L" : (nerves in the lower back) supply the legs, the bladder, bowel and sexual organs Sacral Nerves "S" : (nerves in the lower back) supply the legs, the bladder, bowel and sexual organs 9 9 Spinal Nerves The BRAIN The BRAIN One of the largest organs in the body Controls all mental functions Component of the CNS Composed of over 100 billion neurons Comprises 2-3% of body weight Utilizes over 20% of body’s energy Brain Video Major Divisions of the BRAIN CEREBRUM - occupies most of the cranium and is divided into right and left halves called hemispheres CEREBELLUM - the posterior-inferior portion of the brain BRAIN STEM - consists of the medulla oblongata, the pons, and the midbrain it is continuous with the spinal cord DIENCEPHALON - located above the brainstem, composed primarily of the: Thalamus Hypothalamus 10 10 The Brain Ventricles Cavities within the brain Lateral ventricles (2) - located within each hemisphere in the cerebrum Third ventricle - a vertical slit between the lateral ventricles and inferior to the right and left halves of the thalamus Fourth ventricle - space between the brainstem and the cerebellum Ventricles of the Brain Choroid Plexus Network of capillaries in the walls of the ventricles Formation of CSF by the choroid plexus is facilitated by the very high rates of blood flow to the choroid plexus Covered with ependymal cells that form the cerebrospinal fluid In the choroid plexus the ependymal cells are, in contrast to elsewhere in the brain, tightly bound by tight junctions That means, these ependymal cells are so close together they form the bloodCSF barrier (different than the bloodbrain barrier). Selectively permeable barrier White cells are capillary endothelial cells Blood-CSF vs Blood-Brain Barriers Blue cells are ependymal cells The structure of cell layers in the choroid plexus/BCB (blood-CSF barrier) is shown in the top of the figure. The structure of cell layers elsewhere in the brain/BBB (blood-brain barrier) is shown in the lower part of the figure. 11 11 Gray and White Matter Gray and White Matter White Matter - the aggregation of myelinated processes from many neurons Visible upon freshly dissected brain or spinal tissue White color is due to myelination Gray Matter - unmyelinated nerve cell bodies, axons, dendrites, ganglia, and axon terminals Appears gray because of lack of myelin Protection and Coverings of the Brain Protected by the cranial bones and the cranial meninges Dura Mater - outer layer Arachnoid - middle layer Pia Mater - inner layer Also protected by cerebrospinal fluid fluid that nourishes and protects the brain and spinal cord continuously circulates through the subarachnoid space around the brain and throughout the cavities within the brain Meninges Spinal Cord Protective Coverings Dura Mater Arachnoid Pia Mater Meninges of the Brain Connective tissue covering found around the brain and spinal cord Three layered membrane Dura Mater - outer most layer dense irregular connective tissue Arachnoid - middle layer spider web arrangement of collagen fibers Pia Mater - inner most meninges very delicate layer of thin tissue 12 12 Cerebrospinal Fluid Mechanical Protection Serves as a shock absorbing medium Buoys the brain so it literally floats within the cranial cavity Chemical Protection Provides an optimal chemical environment for neural signaling Flow of CerebroSpinal Fluid Circulation Acts as a medium for exchange of nutrients and waste products between the blood and nervous tissue Blood Supply to the Brain Flow of CerebroSpinal Fluid One of the most metabolically active organs in the body Makes up only 2-3% of body weight but uses about 20% of available O2 at rest Well supplied with O2 and nutrients Only nutritional source for brain metabolic activity is glucose Capillaries in the brain are much less leaky than other capillaries in the body and form a blood brain barrier The Brain Stem The Medulla Oblongata Most inferior portion of the brain stem The most inferior portion of the brain Connects the brain stem to the spinal cord Connects the brain to the spinal cord Respiratory Center Composed of Three Areas The Medulla Oblongata The Pons The Midbrain Adjusts rhythm and depth of breathing Cardiovascular Center Regulates heart rate and contraction force Influences vasoconstriction and vasodilation Also controls coughing, vomiting, swallowing, and hiccupping 13 13 The Medulla Oblongata The Medulla Oblongata The Pons The Midbrain Lies superior to the medulla oblongata Superior to the pons Together with the respiratory center in the medulla helps control respiration Connects the brain stem to the diencephalon Pons and Midbrain The Diencephalon Area of the brain containing the: Thalamus Hypothalamus 14 14 The Thalamus Oval structure that makes up 80% of the diencephalon Comprised of a pair of oval masses (mostly gray matter) Principle relay station between the various sections of the brain The Hypothalamus A small portion of the diencephalon located below the thalamus One of the main regulators of homeostasis in the body Lacks a blood brain barrier Partially protected by the sella turcica of the sphenoid bone Functions of the Hypothalamus Hypothalamus Coordinates nervous system and endocrine system activities to maintain homeostasis Thirst, Hunger, Satiety Sleep Patterns and Waking States Temperature regulation Sex Drive, Maturation, Aggression, and Rage Influences movement of food through the Gastrointestinal Tract production and secretion of hormones that control other Endocrine Glands 15 15 The Cerebrum Largest division of the brain The Cerebrum Occupies most of the cranium Accounts for 85% of brain mass Divided into right and left hemispheres Longitudinal Fissure Corpus Callosum Connects the two hemispheres Cerebral cortex - the outer surface area of the cerebrum Composed mainly of gray matter Contains billions of neurons Terms associated with the Cerebrum Lobes of the Cerebrum Gyri A series of folds in the cortex that increase surface area Sulci A groove or furrow that separates the gyri of the brain Named after the bones that cover them Frontal Lobe Parietal Lobe Temporal Lobe Occipital Lobe 16 16 A Note about the Cerebral Cortex Frontal Lobe Motor Areas Controls movement of voluntary skeletal muscles The cerebral cortex is the most highly developed part of the human brain and is responsible for thinking, perceiving, producing and understanding language It is also the most recent structure in the history of brain evolution Association Areas Carry on high level intellectual processing Problem Solving Reasoning Planning Concentration Memory Behavior Emotions Expressions Broca’s area One of the main areas responsible for speech production Parietal Lobe Sensory Areas Interprets sensations from the skin such as: touch temperature pressure pain Association Areas Understanding of speech Using words to express thoughts and feelings Temporal Lobe Sensory Areas Hearing and balance Association Areas Interpret sensory experiences Memory of visual scenes - music - smells and other complex sensory patterns Wernicke’s Area region of the brain where spoken language is understood (speech comprehension) Occipital Lobe Sensory Areas Visual processing and interpretation Association Areas Combines visual images with sensory experience 17 17 Left Brain vs Right Brain Right side of brain controls left side of body Left side of brain controls right side of body New research at the U of U indicates left and right brain attributes aren’t as clear cut as once thought A little rap to help you remember… The occipital lobe controls your sight. Why it does, we don’t know why. The temporal lobe controls how you hear, like the clucking of a chicken or the stomping of a deer. The parietal lobe processes what you touch whatever you can squeeze or grab or clutch. The Cerebellum Second largest portion of the brain Occupies the inferior and posterior aspects of the cranial cavity Processes sensory information Balance Coordination Maintains postural equilibrium The frontal lobe helps you think and memorize so you can process what you need right before your eyes. These are the lobes of the brain and now you know them so call up all your friends and don’t forget to show em’ WORD! 18 18 Cerebellum and Brainstem Nervous System Disorders and Homeostatic Imbalances Alzheimer’s Disease (AD) Alzheimer’s vs. Dementia Disabling neurological disorder that effects about 11% of the population Dementia is not a disease itself, it is the symptoms 6th leading cause of death in the U.S. It is the only cause of death among the top 10 in America without a way to prevent it, cure it or even slow its progression. A chronic, organic, mental disorder, a form of presenile dementia due to atrophy of neurons of the frontal and occipital lobes AD patients usually die from complications due to being bedridden language difficulty, loss of recent memory poor judgment Alzheimer’s accounts for 60-70% of dementia cases Other types of dementia include: Vascular dementia Parkinson's disease dementia with Lewy Bodies Frontotemporal dementia. 19 19 Amyotrophic Lateral Sclerosis (ALS) Also known as Lou Gehrig’s Disease A relatively rare neurological disorder A syndrome marked by muscular weakness and atrophy with spasticity and hyperflexion due to degeneration of the motor neurons of the spinal cord, medulla, and cortex A degenerative disease No known cure Cerebral Palsy (CP) A group of motor disorders due to loss of muscle control Caused by damage to the motor areas of the brain during fetal development, birth, or infancy About 70% of CP individuals are somewhat mentally retarded due to the inability to hear well or speak fluently Not a progressive disease but the symptoms are irreversible Bacterial Meningitis Infection of the meninges by the bacterium Haemophilus Influenzae Usually affects children under age 5 Symptoms include severe headaches and fever Can lead to brain damage and even death if not treated Epilepsy Short, recurrent, periodic, attacks of motor, sensory, or psychological malfunction Characterized by seizures which can result in involuntary skeletal muscle contraction, loss of muscle control, inability to sense light, noise, and smell, and loss of consciousness Most epileptic seizures are idiopathic Multiple Sclerosis (MS) Parkinson’s Disease (PD) The progressive destruction of the myelin sheaths of neurons of the CNS A chronic nervous disease characterized by a fine, slowly spreading tremor, muscle weakness and rigidity, and a peculiar gait The sheaths deteriorates to scleroses Usually affects people over 60 hardened scars or plaques “short circuits” nerve transmission Cause is unknown May be a type of an autoimmune disease No known cure Progressive loss of function with intermittent periods of remission Cause is unknown but a toxic environmental factor is suspected Chemical basis of the disease appears to be too little dopamine and too much Ach Treatment includes increasing levels of dopamine and decreasing Ach Difficult because dopamine does not cross the blood brain barrier Usually can be controlled with drug therapy GABA - gamma aminobutyric acid Attempting to transplant fetal nervous tissue into the damaged area of the brain of some Parkinson’s Disease patients 20 20 Cerebral Vascular Accident (CVA) - Stroke The most common brain disorder Characterized by slurred speech, loss of or blurred vision, dizziness, weakness, paralysis of a limb or hemiplegia, coma, and death Risk Factors for Stroke hypertension heart disease smoking diabetes Ischemic CVA - due to lack of blood supply to a particular area of the brain atherosclerosis Hemorrhagic CVA - due to the rupture of a blood vessel in the brain obesity Symptoms of a Stroke hyperlipidemia excessive alcohol intake Is it a stroke? Sudden numbness, tingling, weakness, or loss of movement in your face, arm, or leg, especially on only one side of your body (facial drooping) Sudden vision changes. Sudden trouble speaking. Sudden confusion or trouble understanding simple statements. Sudden problems with walking or balance. A sudden, severe headache that is different from past headaches. Reye’s Syndrome Acute childhood illness that causes fatty infiltration of the liver and brain, encephalopathy, and increased intracranial pressure Almost always follows within 1 to 3 days of an acute viral infection, flu, or chicken pox Common in infants and children. The incidence often arises during flu outbreaks May be linked to aspirin use Symptoms include vomiting, mood changes, confusion, tachycardia, and tachypnea Hydrocephalus Excessive accumulation of cerebrospinal fluid within the ventricles of the brain. Occurs most often in newborns The head is enlarged and the brain may be compressed causing brain damage Early detection and surgical intervention improves the prognosis Complications of the surgery include infection of the shunt. Treatment involves treating the symptoms 21 21 Hydrocephalus Spina Bifida Congenital defect where the neural arch fails to unit Usually involves the lumbar vertebrae Symptoms may be mild to severe usually results in paralysis partial or complete loss of bladder control absence of reflexes Can be diagnosed during pregnancy by sonography, amniocentesis, blood tests Spina Bifida Spina Bifida Spina Bifida Spina Bifida 22 22 Headaches Headaches Most commonly begins as a patient complaint, but is usually a symptom of an underlying disorder Ninety percent are caused by vascular problems or muscle contractions Tension headaches mild, dull pressure without other accompanying symptoms Cluster headaches severe pain (sometimes described as “stabbing” pain) behind one eye, and may be accompanied by redness and nasal congestion Sinus headaches pain and pressure behind the brow and cheek bones Migraines pounding headache, nausea, vomiting, and light sensitivity Concussion Most common head injury resulting from a blow to the head – a blow hard enough to jostle the brain and make it hit against the skull causing temporary neural dysfunction. Precipitating causes include a fall to the ground, a punch to the head, automobile accidents and child abuse Most victims recover within 24 to 48 hours after the injury Symptoms a loss of consciousness vomiting possible amnesia dizziness headache Lethargy Treatment Monitoring vital signs, mental status, level of consciousness, and pupil size Whiplash Whiplash Results from a sharp hyperextension and flexion of the neck that damages the muscles, ligaments, disks and nerve tissue Common after rear-end automobile accidents. Padded headrests and shoulder harnesses reduce the risk of this type of injury. Symptoms can include: pain in the interior and posterior neck dizziness headache neck rigidity numbness in the arms Treatment includes: immobilizing the neck at the scene of the accident ruling out spinal cord injury analgesics warm compresses a cervical collar possible physical therapy Spinal Cord Injury (SCI) Commonly referred to as a broken neck Involves injury to the spinal cord The more superior the injury, the more permanent damage results to the patient Causes of the injury include: motor vehicle accidents falls sporting injuries (football, skiing) diving into shallow water gunshot wounds. Paralysis of the body may occur Paraplegia: lower half of the body is paralyzed Quadriplegia: body from the neck down is paralyzed Treatment: maintaining vital functions and rehabilitation to maintain the use of muscles. 23 23 Depression This is a sad mood, which may be a primary disorder, a response to a disease process or a drug reaction. Causes include: Genetic Familial Biochemical Physical and physiological processes The person may have feelings of helplessness, anger, hopelessness, low self-esteem, and pessimism Other symptoms include weight loss or weight gain, sleep disturbance, depressed mood most of the day, energy loss, fatigue, difficulty thinking or concentrating Treatment may involve: Psychotherapy drug therapy Counseling Light therapy 24 24