Chapter 50Concept 50.1 Sensory receptors transduce stimulus energy and trsmit signals to the CNSAll stimuli represent forms of energySensation involves converting energy into a change in the membrane potential of sensory receptors.-Sensory pathwaysSensory pathways have four basic functions in common1) Sensory Reception2) Transduction3) Transmission4) Integration-Sensory reception and transductionSensations and perceptions begin with sensory reception, detection of stimuli by sensory receptorSensory Receptors: Interact directly with stimuli, both inside and outside the body.Sensory transduction: is the conversion of stimulus energy into a change in the membrane potential of a sensory receptorThis change in membrane potential is called receptor potential (graded potentials; their magnitude carries with the strength of the stimulus)-TransmissionAfter energy has been transduced into a receptor potential, some sensory cells generate the transmission of action potentials to the CNSSome sensory receptors are specialized cells that regulate neuronsSpecialized sensory cells include those used for vision, taste, and hearing.Sensory neurons produce action potentials and their axons extend into the CNSThe response of a sensory receptor varies with intensity of stimuliIf the receptor is a neuron, a large receptor potential results in more frequent action potentials.Used in smell, pain, touch, pressure, and body position receptorsif the receptor is not a neuron but a specialized sensory receptor cell, a larger receptor potential causes more neurotransmitters to be released.May alter action potential frequency of the sensory neuron that is communicating with the sensory cell.-PerceptionPerceptions: Are the brains construction of stimuliStimuli travel as action potentials along dedicated neural pathwaysBrain distinguishes stimuli from different receptors-Types of Sensory receptors1) Mechanoreceptors: Sense physical deformation caused by stimuli, such as pressure, stretch, motion, and sound.Touch relies on mechanoreceptorsKnee jerk response is triggered by the vertebrate stretch receptor, detects muscle movement2) Chemoreceptors: transmit info about the total solute concentration of a solution.Smell and TasteSpecific chemoreceptors respond to individual kinds of moleculesWhen a stimulus molecule binds to a chemoreceptor, it becomes more or less permeable to ions, changing membrane potential.3) Electromagnetic Receptors: detect light, electricity, and magnetismPhotoreceptors: detect light4) Thermoreceptors: respond to heat or cold, help regulate body temp by signaling surface and core body temp.5) Pain receptors or Nociceptors: is a class of naked dendrites in the epidermisRespond to excessive hear, pressure, or chemicals released form damaged or inflamed tissue-Concept 50.2: Mechanoreceptors responsible for hearing and equilibrium, detect moving fluid or settling particlesHair Cells: detect setting particles or moving fluid.-HearingVibrating objects create percussion waves in the air that cause the tympanic membrane (Ear Drum) to vibrate3 bones of the middle ear transmit the vibrations of moving air to the oval window on the cochleaVibrations create pressure waves in the fluid in the cochlea stimulate the movement of hair cells in the ear.-EquilibriumSeveral organs of the inner ear detect body movement, position, and balanceUtricle and saccule contain granules called otoliths that allow us to perceive position relative to gravity or linear movement3 semicircular canals: contain fluid and can detect angular movement in any directionMovement of body causes the otoliths or fluid to lag behind, causingmovement of hair cells, which can then send a signal to the brain.-Concept 50.3: Visual receptors in diverse animals depend on light absorbing pigmentProcessing of visual info beings in the retina2 photoreceptors1) Rods: Lowlight, perceive shades of gray2) Cones: Bright light, perceive color (Red, Blue, Yellow)-Concept 50.4: Sense of taste and smell rely on similar sets of sensory receptorsin animalsGustation: Taste: Dependent on detection of chemicals called tastantsOlfaction: Smell: Dependent on detection of odorant molecules-Taste in MammalsTaste buds: receptor cells for taste are modified epithelial cells 5 Tastes: Sour, Salty, Bitter, Sweet, and Umami-Smell in HumansOlfactory receptor cells are neurons that line the inner portion of the nasal cavity. -Concept 50.5: They physical interaction of protein filaments is reguired for muscle functionMuscle activity is a response to input from the nervous systemmotor output occurs (efferent) neurons that are connected to:1) Skeletal muscles2) Smooth muscles (found in internal organs/blood vessels)3) Cardiac muscle4) GlandsAction of muscle is always to contract-Concept 50.6: Skeletal system transforms muscle contraction into locomotionSkeletal muscles are attached in antagonistic pairs, actions are coordinatedby nervous systemVertebrate Skeletal MuscleVertebrate skeletal muscle moves bones and the body and is characterized by a hierarchy of smaller and smaller unitsA skeletal muscle consists of a bundle of long fibers, each a single cell, running parallel to the length of the muscle.Each muscle fiber is itself a bundle of smaller myofibrils arranged longitudinallyMyofibrils are composed of 2 types of myofilaments1) Thin Filaments: consist of 2 strands of actin and 2 strands of a regulatory protein2) Thick filaments: staggered arrays of myosin molecules Skeletal muscle is also called striated muscle because of the regular arrangement of myofilaments creates a pattern of light and dark bandsThe functional unit of a muscle is called a sarcomere and is bordered by Z linesThin filaments are anchored to the ends of the sarcomere at the Z lineThick filaments are anchored to the middle of the sarcomere at the M line.-Sliding filament model of muscle contractionSliding Filament model: filaments slide past each other longitudinally, producing more overlap between thin and thick filamentsSliding filaments rely on interaction between actin and myosinHead of myosin molecule bind to an actin filament, forming a cross bridge and pulling the thin filament toward the center of the sarcomereMuscle contraction requires repeated cycles of binding and releaseATP supports sustained muscle
View Full Document
Unlocking...