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Pages: Chp 9; 229-245 Chp 11; 277-288 . Chp 12; 289-319 .

Chp 9: Nervous tissue chp 11: autonomic nervous system chp 12: somatic senses and special senses. Pages: Chp 9; 229-245 Chp 11; 277-288 . Chp 12; 289-319 . Chapter 9: Nervous Tissue Learning Objectives.

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Pages: Chp 9; 229-245 Chp 11; 277-288 . Chp 12; 289-319 .

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  1. Chp9: Nervous tissuechp 11: autonomic nervous systemchp 12: somatic senses and special senses Pages: Chp 9; 229-245 Chp 11; 277-288. Chp 12; 289-319.

  2. Chapter 9: Nervous TissueLearning Objectives • Describe the organization of the nervous system. • Compare the structure and functions of neuroglia and neurons. • Describe how a nerve impulse is generated and conducted.

  3. Structures of the Nervous System

  4. Functions of the Nervous System • Sensory functions _ (AFFECTORS) Sensory receptors_ detect stimuli inside and outside the body. - Sensory or afferent neurons carry information from cranial to spinal nerves into brain and spinal cord or visa versa • Integrative functions _(LIKE A CONTROL CENTER) Process sensory information by analyzing and storing some of it and by making decisions for appropriate responses - Interneurons; have short axons that connect with neurons in brain, spinal cord, and ganglion; are majority neurons in the body

  5. Functions…continued • Motor functions _(EFFECTORS) Respond the integrative decisions - Motor of efferent neurons carry information from brain toward spinal cord or out of brain to spinal cord into cranial or spinal nerves

  6. Organization of the Nervous System

  7. Enteric Nervous System (ENS) • nnGet a copy of checkpoint questions 1-3, complete them and hand them in… • b Get a copy of checkpoint questions 1-3, complete them and hand them in…

  8. HISTOLOGY OF NERVOUS TISSUE • Two types of cells • Neurons • unique functions of the nervous system; sensing, thinking, remembering, controlling muscle activity, and regulating glandular secretions • Neuroglia • support, nourish, and protect neurons and maintain homeostasis in the intestinal fluid that baths neurons

  9. Neurons • Three parts: • Cell Body • nucleus surrounded by cytoplasm; includes RER, lysosomes, mitochondria, Golgi • synthesizes cellular molecules needed for a neuron’s operation Processes or extensions: • Dendrites (“little trees”) • multiple per single axon • combined with cell body receiving and input parts of a neuron • short, tapering, and highly branched, tree-branch array emerging from cell body • Axons_ • conducts nerve impulses toward another neuron, muscle fiber, or gland cell • long, thin, cylindrical projection that joins cell body at a cone-shaped elevation

  10. nn

  11. Neuroglia • Smaller than neurons • 5-50 times more numerous • ”glue” that holds nervous tissue together • do not generate or conduct nerve impulses • can multiply and divide in mature nervous system • in case of injury or disease multiply to fill in spaces formerly occupied by neurons • Gliomas: brain tumors derived from glia called gliomas; very malignant and grow rapidly

  12. Myelination • Myelin sheath, many-layered covering composed of lipids and protein, surround the axons of most of our neurons. • Two Functions: (1) insulates the axon (2) increases the speed of nerve impulse conduction The amount of myelin increases from birth to maturity

  13. Gray and White Matter • White matter: myelinated and unmyelinated axons of many neurons which is white in color; also has blood vessels • Gray matter: neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia white is grayish pink in color; also has blood vessels

  14. ACTION POTENTIALS • AKA  nerve impulses • Two features of plasma membrane needed for action potentials in muscle fibers and in neurons • existence of resting membrane potential • presence of specific types of ion channels • Membrane potentialdifference in the amount of electrical charge inside and outside plasma membrane. • membrane that has potential is polarized • Resting membrane potential  voltage difference between the inside and outside of a plasma membrane when not responding to a stimulus, in muscle fibers and neurons • voltage created by flow of ions

  15. Ion Channels • Two types of ion channels: • Leakage channels allow small but steady stream of ions to leak across the membrane • Gated channels  open and close on command Voltage-gated channels are used to generate and conduct action potentials; open in response to a change in membrane potential

  16. Resting Membrane Potential

  17. Generation of Action Potential • Action potential (AP) or impulse generates rapidly occurring events that decrease and increase the membrane potential and eventually restore it to its resting state • Ability of muscle fibers and neurons to convert stimuli into action potential is called electrical excitability. • Stimulus in cell’s environment changes resting membrane potential; if stimulus causes cell to depolarize to a critical level; called a threshold (about -55mV) then an action potential arises • Two main phases: • Depolarizing phase- rapidly occurring events that decrease and eventually reverse polarization of membrane, makes inside more positive than outside; Na+ ions move into cell • Repolarizing phase- membrane polarization is restored to resting state; Na+ ions move back out cell restoring charge to original state

  18. All-or-None Principle

  19. Depolarizing phase Repolarizing phase Reversal of polarization Threshold 7.Resting membrane potential Stimulus 6After-hyperpolarizing phase

  20. Conduction of Nerve Impulses • Also called propagation • Way cells communicate information from one part of body to another • Nerve impulses travel from where they arise, usually axon hillock, along axon to axon terminal • Positive feedback process

  21. Continuous & Saltatory Conduction • Continuous conduction • Step-by-step process; impulses travel a short distance in 10 milliseconds • Occurs in unmyelinated axons (muscle fibers) • Have smallest diameter • Saltatory conduction • Impulses leap from one node of Ranvier to the next • Occurs in myelinated axons • Have largest diameter

  22. Synaptic Transmission • How synapses neurons communicate with other neurons or with effectors through a series of events • neuron sending the signal is called the presynaptic neuron • neuron receiving the signal called the postsynaptic neuron • A synaptic cleft separates the presynaptic and postsynaptic neurons Neurotransmitters Different neurotransmitters are found in synaptic vesicles. These different neurotransmitters have different effects.

  23. Postsynaptic: Deactivating Neurotransmitters • Essential neurotransmitters are removed in order to restore normal synaptic function • Three ways: • Diffuse away from synaptic cleft (out of reach of receptors) • Destroyed by enzymes • Actively transported back into neuron (reuptake)

  24. Chapter 11 Learning Objectives • Autonomic Nervous System • Outline the main structural and functional differences between the somatic and autonomic nervous systems. • Identify the structural features of the autonomic nervous system. • Discuss the functions of the sympathetic and parasympathetic divisions of the autonomic nervous system.

  25. COMPARISON OF SOMATIC AND AUTONOMIC NERVOUS SYSTEMS Somatic nervous system (SNS; consciously perceived) • includes both sensory and motor neurons. • Somatic sensory neurons convey input form receptors for the special senses: • Vision, hearing, taste, smell, and equilibrium • Also receptors for somatic senses of: • Pain, temperature, touch, and proprioceptive sensations • Sensory motor neurons synapse with skeletal muscle and produce conscious, voluntary movements. • Skeletal muscles also generate breathing movements.

  26. COMPARISON OF SNS AND ANS…continued Autonomic Nervous System (ANS; cannot be consciously suppressed or altered) • Autonomic sensory neurons are associated with sensory receptors that monitor internal conditions. • blood CO2levels • degree of stretching in walls of internal organs or blood vessels • Autonomic motor neurons regulate cardiac and smooth muscles, and glands. • Comparison of somatic and autonomic motor neurons • Somatic motor neurons extend from CNS to skeletal muscle fibers that it stimulates. • Autonomic motor pathways consist of two motor neurons. • Preganglionic neuron • Has cell body in CNS • Postganglioninc neuron • Lies entirely in PNS • Autonomic also has two main branches: • sympathetic division • parasympathetic division

  27. FUNCTIONS OF THE AUTONOMIC NERVOUS SYSTEM • ANS Neurotransmitters

  28. Activities of the ANS Sympathetic Activities—“Fight or Flight” • “E” situations that could bring on stress: • Exercise, excitement, emergency, or embarrassment • List examples of “Fight or Flight” responses: • pupils of eyes dilate • heart rate, force of heart contraction, and blood pressure increase • airways dilate, faster movement of air into and out of lungs • reduce blood flow in vessels of nonessential organs; slowing urine formation and digestive activities during exercise • blood vessels supply organs involved in exercise or fighting off danger dilate, allowing greater blood flow through these tissues • liver cells break down glycogen to glucose, adipose cells break down triglycerides to fatty acids and glycerol, providing molecules used by body cells for ATP production • release of glucose by liver increases blood glucose level • processes not essential for meeting stressful situation are inhibited

  29. Activities of the ANS…continued Parasympathetic Activities—“Rest and Digest” • Supports body functions that conserve and restore body energy during times of rest and recovery • SLUDD: salivation, lacrimation, urination, digestion, and defecation

  30. Chapter 12 Learning Objectives • Sensations • Define a sensation and describe the conditions necessary for a sensation to occur. • List and describe the somatic sensations. • Define proprioception and describe the structure of proprioceptive receptors. • Describe the receptors for olfaction and the olfactory pathway to the brain. • Describe the receptors for gustation and the gustatory pathway to the brain. • Describe the receptors for vision and the visual pathways to the brain. • Describe the mechanism involved in vision. • Describe the receptors for hearing and equilibrium, and their pathways to the brain.

  31. OVERVIEW OF SENSATIONS Definition of a Sensation • Must meet four conditions: • stimulus or change in environment, activate certain sensory neurons • form of light, heat, pressure, mechanical energy, or chemical energy • sensory receptor must convert stimulus to electrical signal which produces one or more nerve impulses if it is large enough • nerve impulses must be conducted along a neural pathway from sensory receptor to brain • region of brain must receive and integrate nerve impulses into a sensation Characteristics of Sensations • Perceptions: conscious sensation • “eyes see” ; specialized sensory neurons integrated in cerebral cortex where they are interpreted • Adaptation: a decrease in strength of a sensation due to prolonged stimulus which may lead to perceptions fading or disappearing even though stimulus persists

  32. Types of Sensory Receptors • Review Table 12.1, page 291 for test • Free nerve endings • Encapsulated nerve endings • Mechanoreceptors • Thermoreceptors • Nociceptors • Photoreceptors • Chemoreceptors

  33. SOMATIC SENSES Tactile Sensations (Mechanoreceptors) Touch, pressure, vibration -- Detected by encapsulated nerve endings Itch, and tickle -- Detected by free nerve endings

  34. SOMATIC SENSES…continued • Touch • rapidly adapting touch receptors: • Corpuscles of touch (Meissner corpulses)_ • Hair root plexuses_ • slowly adapting touch receptors: • Type I cutaneous mechanoreceptors (Merkel disks) • Type II cutaneous mechanoreceptors (Ruffini corpulses) • Pressure and Vibration • pressure is a sustained sensation felt over a larger area than touch • Pressure receptors:: Type I mechanoreceptors and lamellated (pacinian) corpulses • lower frequency vibrations: corpulses of touch • higher frequency vibrations: lamellated corpulses • Itch and tickle • Itch sensations stimulated by stimulation of free nerve endings by certain chemicals like bradykinin, often a result of local inflammatory response Can you tickle yourself? Why or why not? Impulses are conducted to and from cerebellum when you are moving your fingers and touching yourself does not occur when someone else tickles you

  35. Sensory receptors in the skin and subcutaneous layer Go to page 292 and try labeling… a. Meissner corpuscles (Corpuscles of touch) b. Pacinian corpuscles (Lamellated corpuscles) c. Ruffini corpuscles (Type II cutaneous mechanoreceptors) d. Merkel Disks (Type I cutaneous mechanoreceptors) e. Hair Root Plexuses f. Free nerve Endings

  36. Thermal Sensations (Thermoreceptors) • Thermoreceptors: free nerve endings • Thermal sensations: coldness and warmth • Temperatures between 10 and 40C (50-105F) • activate cold receptors • located in the epidermis • Temperatures between 32 and 48C (90- 118F) • activate warm receptors • located in the dermis • Below 10C and above 48C stimulate • nociceptors • produce painful sensations

  37. Painful Sensations (Nociceptors) • Nociceptors: free nerve endings • Found in almost every tissue of body except brain • Five stimuli that can cause pain • excessive stimulus of sensory receptors • bright light in your eyes • excessive stretching of structure • prolonged muscle contractions • hold weight for a long time • inadequate blood flow to organ • certain chemical substances • Referred pain: pain felt in skin above or located near but not in organ • Fast pain: within 0.1 seconds of stimulus; acute, sharp, or prickling pain; localized not in deep tissue • Slow pain: begins a second or more after stimulus is applied; chronic burning, aching, throbbing; skin deep tissue and internal organs

  38. Proprioceptive Sensations (Proprioceptors) • Inform you consciously and unconsciously of • degree to which your muscles are contracted • amount of tension present in your tendons • positions of your joints • orientation of your head • Receptors for these sensations called: • Proprioreceptors and are located in: • skeletal muscles, tendons, in and around synovial joints, and in inner ear • They adapt slowly and only slightly • Kinesthesia: perception of body movements, allows you to walk, type, or dress without using your eyes

  39. SPECIAL SENSES OLFACTION: SENSE OF SMELL (Chemoreceptors) • CHARACTERISTICS OF RECEPTORS: • first-order neuron of olfactory pathway • tips are protected by olfactory hairs • stimulated by odorants; inhaled chemicals • cells live about a month and then replaced

  40. GUSTATION: SENSE OF TASTE (Chemoreceptors) • CHARACTERISTICS OF RECEPTORS: • chemicals known as tastants stimulate them • electrical signal stimulate release of neurotransmitter molecules that bind to gustatory receptors on dendrites of taste buds’ first-order neurons • respond to any one of five primary tastes: sweet, sour, bitter, salty, or umami (savory, glutamate detection) • 1. bitter • 2. salty • 3. sour • 4. sweet

  41. VISION (Photoreceptors) • Retina is the beginning of visual pathway • Three layers: • photoreceptor layer, bipolar cell layer, and ganglion cell layer • Two types of cells in photoreceptor layer: • rods (allow us to see shades of gray in dim light, like moonlight) • cones (stimulated by brighter light- highly acute, color vision) • Stimulation of photoreceptors • photopigment absorbs light ; undergo change in structure to adjust to amount of light available • rods photopigment is rhodopsin

  42. HEARING AND EQUILIBRIUM (Mechanoreceptors) • Ear three principle regions: the outer ear, the middle ear, and the inner ear. • Physiology of Hearing (1) auricle directs sound waves into external auditory canal (2) sound waves strike eardrum; produce vibrations, eardrum vibrates in response (3) central area of eardrum connects to malleus that also starts to vibrate, vibration moves from malleus to incus to stapes (4) stapes moves back and forth, pushes the oval window in and out (5) movement of oval window sets up fluid pressure waves in cochlea (6) pressure waves move eventually to membrane covering the round window causing it to bulge into the middle ear (7) pressure waves deform walls internal structures pushing membranes back and forth, creating pressure waves inside cochlear duct (8) pressure causes basilar membrane to vibrate, moving hair cells of the spiral organ release neurotransmitter molecules; sensory neurons generate nerve impulses along nerve and sound is received and interpreted

  43. Physiology of Equilibrium • Static equilibrium • maintenance of the position of the body relative to the force of gravity; maintains posture and balance by providing sensory information on the position of the head • Dynamic equilibrium • maintenance of body position in response to sudden movements such as rotation, acceleration, and deceleration; reestablish balance to disturbed equilibrium by regulating sensitivity of hair cells in the ear

  44. Extra CREDIT OPPORTUNITY • Up to 10 points • Compare and contrast how different medications like analgesics, anesthetics, anesthesia, and opiates treat pain. • Typed 1-2 pages with at least two MLA cited references. • Due by: 1/2 or 1/3 when I see you again • Will not be accepted late unless absent when due…

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