CHAPTER 49 SENSORY AND MOTOR MECHANISMS INTRO TO

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CHAPTER 49 SENSORY AND MOTOR MECHANISMS

CHAPTER 49 SENSORY AND MOTOR MECHANISMS

INTRO TO SENSORY RECEPTION • AN ANIMAL’S INTERACTION WITH ITS ENVIRONMENT DEPENDS ON THE

INTRO TO SENSORY RECEPTION • AN ANIMAL’S INTERACTION WITH ITS ENVIRONMENT DEPENDS ON THE PROCESSING OF SENSORY INFO AND THE GENERATION OF MOTOR OUTPUT • SENSORY RECEPTORS RECEIVE INFO FROM THE ENVIRONMENT – ACTION POTENTIALS THAT REACH THE BRAIN VIA SENSORY NEURONS ARE TERMED SENSATIONS – INTERPRETATION OF A SENSATION LEADS TO THE PERCEPTION OF THE STIMULUS (SMELLS, SOUNDS) • MOTOR EFFECTORS CARRY OUT THE MOVEMENT IN RESPONSE TO THE SENSOR INFO

SENSORY RECEPTORS • SENSORY RECEPTION = ABILITY OF A CELL TO DETECT THE ENERGY

SENSORY RECEPTORS • SENSORY RECEPTION = ABILITY OF A CELL TO DETECT THE ENERGY OF A STIMULUS • SENSORY RECEPTORS = STRUCTURES THAT TRANSMIT INFO ABOUT CHANGES IN AN ANIMAL’S INTERNAL AND EXTERNAL ENVIRONMENT • THEY ARE USUALLY MODIFIED NEURONS OR EPITHELIAL CELLS OCCURRING SINGLY OR WITHIN GROUPS IN SENSORY ORGANS – EXTERORECEPTORS DETECT EXTERNAL STIMULI, SUCH AS HEAT, PRESSURE, LIGHT, CHEMICALS – INTERORECEPTORS DETECT INTERNAL STIMULI, SUCH AS BLOOD PRESSURE AND BODY POSITION • SPECIALIZED TO CONVERT STIMULI ENERGY INTO CHANGES IN MEMBRANE POTENTIALS AND THEN TRANSMIT SIGNALS TO THE N. S. • ALL RECEPTORS CELLS HAVE THE SAME 4 FUNCTIONS: TRANSDUCTION, AMPLIFICATION, TRANSMISSION, INTEGRATION

SENSORY TRANSDUCTION • SENSORY TRANSDUCTION IS THE CONVERSION OF STIMULUS ENERGY INTO A CHANGE

SENSORY TRANSDUCTION • SENSORY TRANSDUCTION IS THE CONVERSION OF STIMULUS ENERGY INTO A CHANGE IN THE MEMBRANE POTENTIAL OF A RECEPTOR CELL • STIMULUS ENERGY CHANGES MEMBRANE PERMIABILITY OF THE RECEPTOR CELL (VIA OPENING OR CLOSING ION CHANNEL GATES, OR INCREASING ION FLOW BY STRETCHING THE RECEPTOR CELL MEMBRANE) AND RESULTS IN A GRADED CHANGED IN MEMBRANE POTENTIAL CALLED RECEPTOR POTENTIAL

AMPLIFICATION • AMPLIFICATION OF STIMULUS ENERGY THAT IS TOO WEAK TO BE CARRIED INTO

AMPLIFICATION • AMPLIFICATION OF STIMULUS ENERGY THAT IS TOO WEAK TO BE CARRIED INTO THE N. S. OFTEN OCCURS • MAY TAKE PLACE IN ACCESSORY STRUCTURES OR BE A PART OF THE TRANDUCTION PROCESS

TRANSMISSION • TRANSMISSION OF A SENSATION TO THE CNS OCCURS IN 2 WAYS: •

TRANSMISSION • TRANSMISSION OF A SENSATION TO THE CNS OCCURS IN 2 WAYS: • 1) THE RECEPTOR CELL DOUBLES AS A SENSORY NEURON (E. G. PAIN CELLS). IN THIS CASE, THE INTENSITY OF THE RECEPTOR POTENTIAL WILL EFFECT THE FREQUENCY OF ACTION POTENTIALS THAT CONVEY SENSATIONS TO THE CNS • 2) THE RECEPTOR CELL TRANSMITS CHEMICAL SIGNALS (NEUROTRANSMITTERS) ACROSS A SYNAPSE TO A SECOND SENSORY NEURON. IN THIS CASE THE RECEPTOR POTENTIAL AFFECTS THE AMT OF NEUROTRANSMITTER THAT IS RELEASED, WHICH IN TURN INFLUENCES THE FREQUENCY OF ACTION POTENTIAL GENERATED BY THE SENSORY NEURON

INTEGRATION • RECEPTOR SIGNALS ARE INTEGRATED THROUGH SUMMATION OF GRADED POTENTIALS • SENSORY ADAPTATION

INTEGRATION • RECEPTOR SIGNALS ARE INTEGRATED THROUGH SUMMATION OF GRADED POTENTIALS • SENSORY ADAPTATION IS A DECREASE IN SENSITIVITY DURING CONTINUED STIMULATION; A TYPE OF INTEGRATION THAT RESULTS IN SELECTIVE INFO BEING SENT TO THE CNS • THE THRESHOLD FOR TRANSDUCTION BY RECEPTOR CELLS VARIES WITH CONDITIONS RESULTING IN A CHANGE IN RECEPTOR SENSITIVITY • SENSORY INFO INTEGRATION OCCURS AT ALL LEVELS IN THE N. S.

CATEGORIES OF SENSORY RECEPTORS • RECEPTORS CAN BE GROUPED INTO 5 TYPES DEPENDING ON

CATEGORIES OF SENSORY RECEPTORS • RECEPTORS CAN BE GROUPED INTO 5 TYPES DEPENDING ON THE TYPE OF ENERGY THEY DETECT • 1) MECHANORECEPTORS ARE STIMULATED BY PHYSICAL DEFORMATION CAUSED BY PRESSURE, TOUCH, STRETCH, MOTION, SOUND- ALL FORMS OF MECHANICAL ENERGY – BENDING OF THE PLASMA MEMEBRANE INCREASES ITS PERMEABILITY TO NA+ AND K+ RESULTING IN A RECEPTOR POTENTIAL – IN THE HUMAN SKIN, PACINIAN CORPUSCLES DEEP IN THE SKIN RESPOND TO STRONG PRESSURE, WHILE MEISSNER’S CORPUSCLES AND MERKEL’S DISCS, CLOSER TO THE SURFACE, DETECT LIGHT TOUCH – MUSCLE SPINDLES ARE STRETCH RECEPTORS ( A TYPE IF INTERORECEPTOR) THAT MONITOR THE LENGTH OF SKELETAL MUSCLES, AS IN THE REFLEX ARC – HAIR CELLS DETECT MOTION

SENSORY RECEPTORS IN THE SKIN

SENSORY RECEPTORS IN THE SKIN

2) NOCICEPTORS • NOCICEPTORS ARE A CLASS OF NAKED DENDRITES THAT FUNCTION AS PAIN

2) NOCICEPTORS • NOCICEPTORS ARE A CLASS OF NAKED DENDRITES THAT FUNCTION AS PAIN RECEPTORS • DIFFERENT GROUPS RESPOND TO EXCESS HEAT, PRESSURE, OR SPECIFIC CHEMICALS RELEASED FROM DAMAGED OR INFLAMED TISSUE • PROSTAGLANDINS INCREASE PAIN BY LOWERING RECEPTOR THRESHOLDS; ASPIRIN AND IBUPROFEN REDUCE PAIN BY INHIBITING PROSTAGLANDIN SYNTHESIS

3) THERMORECEPTORS • THERMORECEPTORS RESPOND TO HEAT OR COLD AND HELP REGULATE BODY TEMPERATURE

3) THERMORECEPTORS • THERMORECEPTORS RESPOND TO HEAT OR COLD AND HELP REGULATE BODY TEMPERATURE • THERE IS STILL DEBATE ABOUT THE IDENTITY OF THERMORECEPTORS IN THE MAMMALIAN SKIN. MAY BE TWO RECEPTORS CONSISTING OF ENCAPSULATED, BRANCHED DENDRITES OR THE NAKED DENDRITES OF CERTAIN SENSORY NEURONS • THE INTEROTHERMORECEPTORS IN THE HYPOTHALAMUS FUNCTION AS THE PRIMARY TEMP. CONTROL OF THE MAMMALIAN BODY

4) CHEMORECEPTORS • CHEMORECEPTORS INCLUDE GENERAL RECEPTORS THAT SENSE TOTAL SOLUTE CONCENTRATION (E. G.

4) CHEMORECEPTORS • CHEMORECEPTORS INCLUDE GENERAL RECEPTORS THAT SENSE TOTAL SOLUTE CONCENTRATION (E. G. OSMORECEPTORS OF THE MAMMALIAN BRAIN), RECEPTORS THAT RESPOND TO INDIVIDUAL MOLECULES, AND THOSE THAT RESPOND TO CATEGORIES OF RELATED CHEMICALS (E. G. GUSTATORY AND OLFACTORY RECEPTORS)

5) ELECTROMAGNETIC RECEPTORS • ELECTROMAGNETIC RECEPTORS RESPOND TO ELECTROMAGNETIC RADIATION SUCH AS LIGHT (PHOTORECEPTORS),

5) ELECTROMAGNETIC RECEPTORS • ELECTROMAGNETIC RECEPTORS RESPOND TO ELECTROMAGNETIC RADIATION SUCH AS LIGHT (PHOTORECEPTORS), ELECTRICITY, AND MAGNETIC FIELDS (MAGNETORECEPTORS) • A GREAT VARIETY OF LIGHT DETECTORS HAS EVOLVED IN ANIMALS, FROM SIMPLE CLUSTERS OF CELLS TO COMPLEX ORGANS • MOLECULAR EVIDENCE INDICATES THAT MOST, IF NOT ALL, PHOTORECEPTORS IN ANIMALS MAY BE HOMOLOGOUS

PHOTORECEPTORS • A BROAD ARRAY OF PHOTORECEPTORS HAS EVOLVED AMONG INVERTEBRATES • THE EYE

PHOTORECEPTORS • A BROAD ARRAY OF PHOTORECEPTORS HAS EVOLVED AMONG INVERTEBRATES • THE EYE CUP OF PLANARIANS IS A SIMPLE LIGHT RECEPTOR THAT REPONDS TO LIGHT INTENSITY AND DIRECTION WITHOUT FORMING AN IMAGE – AN OPENING ON ONE SIDE OF THE CUP EMITS LIGHT TO ENTER; THE OPENING TO ONE CUP FACES LEFT SLIGHTLY FORWARD, THE OTHER CUP OPENS RIGHT AND SLIGHTLY FORWARD – LIGHT ENTERS THE OPENING AND STIMULATES PHOTORECPETORS THAT CONTAIN LIGHTABSORBING PIGMENTS – PLANARIA MOVE AWAY FROM LIGHT SOURCES TO AVOID PREDATORS – THE BRAIN COORDINATES AND INTERPRATES NERVE IMPULSES AND MOVEMENTS

EYE CUP OF PLANARIAN

EYE CUP OF PLANARIAN

INVERTEBRATE EYES • 2 TYPES OF IMAGE-FORMING EYES HAVE EVOLVED IN INVERTABRATES: • 1)

INVERTEBRATE EYES • 2 TYPES OF IMAGE-FORMING EYES HAVE EVOLVED IN INVERTABRATES: • 1) COMPOUND EYE - CONTAINS THOUSANDS OF LIGHT DETECTORS CALLED OMMATIDIA, EACH WITH ITS OWN CORNEA AND LENS – FOUND IN INSECTS, CRUSTACEANS AND SOME POLYCHAETE WORMS – RESULTS IN A MOSAIC IMAGE – MORE ACUTE AT DETECTING MOVEMENT PARTLY DUE TO RAPID RECOVERY OF PHOTORECEPTORS • 2) SINGLE-LENS EYE- ONE LENS FOCUSES LIGHT ONTO THE RETINA, WHICH CONSISTS OF A BILAYER OF PHOTOSENSITIVE RECEPTOR CELLS – FOUND IN SOME JELLIES, POLYCHAETES, SPIDERS AND MANY MOLLUSKS

COMPOUND EYES

COMPOUND EYES

VERTEBRATE EYESSINGLE LENS • THE PARTS OF THE VERTEBRATE EYE ARE STRUCTURALLY AND FUNCTIONALLY

VERTEBRATE EYESSINGLE LENS • THE PARTS OF THE VERTEBRATE EYE ARE STRUCTURALLY AND FUNCTIONALLY DIVERSE • CONSISTS OF A TOUGH OUTER LAYER OF CONNETIVE TISSUE, THE SCLERA, AND A THIN INNER PIGMENTED LAYER, THE CHOROID. • A THIN LAYER OF CELLS, THE CONJUNCTIVA, COVERS THE SCLERA AND KEEPS THE EYES MOIST • THE CORNEA IS LOCATED IN FRONT AND IS A TRANSPARENT AREA OF THE SCLERA; IT ALLOWS LIGHT TO ENTER THE EYE AND ACTS AS A FIXED LENS

VERTEBRATE EYE

VERTEBRATE EYE

 • THE ANTERIOR CHOROID FORMS THE IRIS, WHICH REGULATES THE AMOUNT OF LIGHT

• THE ANTERIOR CHOROID FORMS THE IRIS, WHICH REGULATES THE AMOUNT OF LIGHT ENTERING THE PUPIL. THE IRIS IS PIGMENTED AND GIVES THE EYE COLOR; THE PUPIL IS THE HOLE IN THE CENTER OF THE IRIS • THE RETINA IS THE INNERMOST LAYER OF THE EYEBALL; IT CONTAINS PHOTORECEPTOR CELLS WHICH TRANSMIT SIGNALS FROM THE OPTIC DISC, WHERE THE OPTIC NERVE ATTACHES TO THE EYE – THE LENS AND CILIARY BODY DIVIDE THE EYE INTO 2 CHAMBERS; A SMALL CHAMBER BTW. THE LENS AND THE CORNEA AND A LARGE CHAMBER WITHIN THE EYEBALL – THE CILIARY BODY PRODUCES AQUAEOUS HUMOR THAT FILLS THE CAVITY BTW. THE LENS AND CORNEA – VITREOUS HUMOR FILLS THE CAVITY BEHIND THE LENS AND COMPRISES MOST OF THE EYE’S VOLUME – BOTH AQUEOUS HUMOR AND VITREOUS HUMOR HELP TO FOCUS LIGHT ONTO THE RETINA

THE LENS • THE LENS IS A TRANSPARENT, PROTEIN DISC THAT FOCUSES AN IMAGE

THE LENS • THE LENS IS A TRANSPARENT, PROTEIN DISC THAT FOCUSES AN IMAGE ONTO THE RETINA BY CHANGING THE SHAPE (ACCOMMODATION) • IS NEARLY SPHERICAL WHEN FOCUSING ON NEAR OBJECTS AND FLAT WHEN FOCUSING AT A DISTANCE • CONTROLLED BY THE CILIARY MUSCLE

FOCUSING THE MAMMALIAN EYE

FOCUSING THE MAMMALIAN EYE

PHOTORECEPTORS OF THE EYE • THE PHOTORECEPTORS OF THE EYE ARE ROD CELLS AND

PHOTORECEPTORS OF THE EYE • THE PHOTORECEPTORS OF THE EYE ARE ROD CELLS AND CONE CELLS – THEIR RELATIVE NUMBERS IN THE RETINA ARE PARTLY CORRELATED WITH WHETHER AN ANIMAL IS DIURNAL OR NOCTURNAL • ROD CELLS ARE SENSITIVE TO LIGHT BUT DO NOT DISTINGUISH COLORS – FOUND IN GREATEST DENSITY AT PERIPHERAL REGIONS OF THE RETINA; COMPLETELY ABSENT FROM THE FOVEA (CENTER OF VISUAL FIELD) • CONE CELLS ARE RESPONSIBLE FOR DAYTIME COLOR VISION – MOST DENSE AT THE FOVEA

PHOTORECEPTORS IN THE EYE

PHOTORECEPTORS IN THE EYE

LOOK AT THE FOVEA

LOOK AT THE FOVEA

RHODOPSIN • THIS LIGHT ABSORBING PIGMENT OPERATES VIA SIGNAL TRANSDUCTION • CELLS IN THE

RHODOPSIN • THIS LIGHT ABSORBING PIGMENT OPERATES VIA SIGNAL TRANSDUCTION • CELLS IN THE RETINA TRANSDUCE STIMULI (CAUSED BY THE LENS FOCUSING A LIGHT IMAGE ONTO THE RETINA) INTO ACTION POTENTIALS • EACH ROD CELL OR CONE CELL HAS AN OUTER SEGMENT WITH A STACK OF FOLDED MEMBRANES IN WHICH VISUAL PIGMENTS ARE EMBEDDED – THE VISUAL PIGMENTS CONSISTS OF LIGHTABSORBING RETINAL, WHICH IS MADE FROM VITAMIN A, BONDED TO A MEMBRANE PROTEIN OPSIN

LOOK AT VISUAL PIGMENTS

LOOK AT VISUAL PIGMENTS

RODS • RODS CONTAIN THEIR OWN TYPE OF OPSIN, AND WHEN COMBINED WITH RETINAL,

RODS • RODS CONTAIN THEIR OWN TYPE OF OPSIN, AND WHEN COMBINED WITH RETINAL, MAKES UP RHODOPSIN – WHEN RHODOPSIN ABSORBS LIGHT, ITS RETINAL COMPONENT CHANGES SHAPE. THIS TRIGGERS A CHAIN OF METABOLIC EVENTS THAT HYPERPOLARIZES THE PHOTORECEPTOR CELL MEMBRANE; THUS, A DECREASE IN CHEMICAL SIGNAL TO THE CELLS WITH WHICH PHOTORECEPTORS SYNAPSE SERVES AS THE MESSAGE – LIGHT-INDUCED CHANGE IN RETINAL IS REFERRED AS “BLEACHING” OF RHODOPSIN; IN BRIGHT LIGHT, RODS BECOME UNRESPONSIVE AND THE CONES TAKE OVER – IN THE DARK, ENZYMES CONVERT RETINAL BACK TO ITS ORIGINAL FORM

THE EFFECT OF LIGHT

THE EFFECT OF LIGHT

COLOR VISION • COLOR VISION INVOLVES MORE COMPLEX SIGNAL PROCESSING THAN THE RHODOPSIN MECHANISM

COLOR VISION • COLOR VISION INVOLVES MORE COMPLEX SIGNAL PROCESSING THAN THE RHODOPSIN MECHANISM IN RODS – COLOR VISION RESULTS FROM THE PRESENCE OF 3 SUBCLASSES OF CONES: RED CONES, GREEN CONES, AND BLUE CONES, EACH WITH ITS OWN TYPE OF OPSIN ASSOCIATED WITH THE RETINAL FORMING VISUAL PIGMENTS (PHOTOPSINS)

THE RETINA • THE RETINA ASSISTS THE CEREBRAL CORTEX IN PROCESSING VISUAL INFO •

THE RETINA • THE RETINA ASSISTS THE CEREBRAL CORTEX IN PROCESSING VISUAL INFO • INTEGRATION OF VISUAL INFO BEGINS AT THE RETINA • ROD AND CONE CELL AXONS SYNAPSE WITH NEURONS CALLED BIPOLAR CELLS, WHICH IN TURN SYNAPSE WITH GANGLION CELLS • HORIZONTAL CELLS AND AMACRINE CELLS ARE NEURONS IN THE RETINA THAT HELP INTERGRATE THE INFO, AFTER WHICH THE GANGLION CELL AXONS CONVEY ACTION POTENTIALS ALONG THE OPTIC NERVE TO THE BRAIN

 • ROD AND CONE CELL SIGNALS MAY FOLLOW VERTICAL OR LATERAL PATHWAYS –

• ROD AND CONE CELL SIGNALS MAY FOLLOW VERTICAL OR LATERAL PATHWAYS – VERTICAL PATHWAYS INVOLVE INFO PASSING DIRECTLY FROM RECEPTOR CELLS TO BIPOLAR CELLS TO GANGLION CELLS – LATERAL PATHWAYS INVOLVE: HORIZONTAL CELLS CARRYING SIGNALS FROM ONE ROD OR CONE TO OTHER RECEPTOR CELLS AND SEVERAL BIPOLAR CELLS; AMARCRINE CELLS SPREAD THE SIGNALS FROM ONE BIPOLAR CELL TO SEVERAL GANGLION CELLS • HORIZONTAL CELLS, STIMULATED BY ROD OR CONE CELLS, STIMULATE NEARBY RECEPTORS BUT INHIBIT MORE DISTANT RECEPTORS AND NON-ILLUMINATED BIPOLAR CELLS, THUS SHARPENING IMAGE EDGES AND ENHANCING CONTRAST (LATERAL INHIBITION) – OCCURS AT ALL LEVELS OF VISUAL PROCESSING

THE RETINA

THE RETINA

OPTIC NERVES • OPTIC NERVES FROM EACH EYE MEET AT THE OPTIC CHIASM •

OPTIC NERVES • OPTIC NERVES FROM EACH EYE MEET AT THE OPTIC CHIASM • THE OPTIC CHIASM HAS NERVE TRACTS ARRANGED SO THAT WHAT IS VIEWED IN THE LEFT FIELD OF VIEW IS TRANSMITTED TO THE RIGHT SIDE OF THE BRAIN AND VICE VERSA • GANGLION AXONS USUALLY CONTINUE THROUGH THE LATERAL GENICULATE NUCLEI OF THE THALAMUS, AND THESE NEURONS CONTINUE BACK TO THE PRIMARY VISUAL CORTEX IN THE OCCIPITAL LOBE OF THE CEREBRM • ADDITIONAL NEURONS CARRY INFORMATION TO MORE SOPHISTICATED VISUAL PROCESSING CNETERS IN THE CORTEX

VISUAL CENTERS

VISUAL CENTERS

HEARING & EQUILIBRIUM • HEARING AND EQUILIBRIUM ARE RELATED IN MOST ANIMALS AND INVOLVE

HEARING & EQUILIBRIUM • HEARING AND EQUILIBRIUM ARE RELATED IN MOST ANIMALS AND INVOLVE MECHANORECEPTORS • THE MAMMALIAN HEARING ORGAN IS WITHIN THE INNER EAR • SOUND WAVES ARE COLLECTED BY THE OUTER EAR (THE EXTERNAL PINNA AND THE AUDITORY CANAL) AND ARE CHANNELED TO THE TYMPANIC MEMBRANE OF THE MIDDLE EAR

THE EAR

THE EAR

SOUND WAVES • SOUND WAVES CAUSED THE TYMPANIC MEMBRANE TO VIBRATE AT THE SAME

SOUND WAVES • SOUND WAVES CAUSED THE TYMPANIC MEMBRANE TO VIBRATE AT THE SAME FREQUENCY; THE TYMPANIC MEMBRANE TRANSMITS THE WAVES TO THREE SMALL BONES - THE MALLEUS, INCUS, STAPES - WHICH AMPLIFY AND TRANSMIT THE MECHANICAL MOVEMENTS OF THE MEMBRANE TO THE OVAL WINDOW, A MEMBRANE OF THE COCHLEA SURFACE – THE MIDDLE EAR OPENS INTO THE EUSTACHIAN TUBE, A CHANNEL TO THE PHARYNX TO AID IN PRESSURE EQUALIZATION ON BOTH SIDES OF THE TYMPANIC MEMBRANE – OVAL WINDOW VIBRATIONS PRODUCE PRESSURE WAVES IN THE FLUID (ENDOLYMPH) IN THE COILED COCHLEA OF THE INNER EAR

PRESSURE WAVES • PRESSURE WAVES VIBRATE THE BASILAR MEMBRANE (FORMS THE FLOOR OF THE

PRESSURE WAVES • PRESSURE WAVES VIBRATE THE BASILAR MEMBRANE (FORMS THE FLOOR OF THE COCHLEAR DUCT) AND THE ATTACHED ORGAN OF CORTI, WHICH CONTAINS RECEPTOR HAIR CELLS • THE BENDING OF THE HAIR CELLS AGAINST THE TECTORIAL MEMBRANE DEPOLARIZES THE HAIR CELLS ANC CAUSES THEM TO RELEASE A NEUROTRANSMITTER THAT TRIGGERS AN ACTION POTENTIAL IN A SENSORY NEURON, WHICH THEN CARRIES SENSATIONS TO THE BRAIN THROUGH THE AUDITORY NERVE • THE PRESSURE WAVE CONTINUES THROUGH THE TYMPANIC CANAL AND IS DISSIPATED AS IT STRIKES THE ROUND WINDOW

VOLUME • VOLUME IS DETERMINED BY THE AMPLITUDE OF THE SOUND WAVE; PITCH IS

VOLUME • VOLUME IS DETERMINED BY THE AMPLITUDE OF THE SOUND WAVE; PITCH IS A FUNCTION OF SOUND WAVE FREQUENCY • THE GREATER THE AMPLITUTDE OF A SOUND, THE MORE VIBROUS THE VIBRATIONS; THIS RESULTS IN MORE BVENDING OF THE HAIR CELLS AND MORE ACTION POTENTIALS • DIIFERENT SOUND FREQUENCIES AFFECT DIFFERENT AREAS OF THE BASILAR MEMBRANE, THUS SOME RECEPTORS SEND MORE ACTION POTENTIALS THAN OTHERS

SENSATIONS OF THE EAR

SENSATIONS OF THE EAR

THE INNER EAR • SEVERAL ORGANS IN THE INNER EAR DETECT BODY POSITION AND

THE INNER EAR • SEVERAL ORGANS IN THE INNER EAR DETECT BODY POSITION AND BALANCE • BEHIND THE OVAL WINDOW IS A VESTIBULE THAT CONTAINS 2 CHAMBERS, THE UTRICLE AND THE SACCULE • THE UTRICLE OPENS INTO 3 SEMICIRCULAR CANALS

ORGANS OF EQUILIBRIUM

ORGANS OF EQUILIBRIUM

EQUILIBRIUM CON’T • HAIR CELLS IN THE UTRICLE AND SACCULE RESPOND TO CHANGES IN

EQUILIBRIUM CON’T • HAIR CELLS IN THE UTRICLE AND SACCULE RESPOND TO CHANGES IN HEAD POSITION WITH RESPECT TO GRAVITY AND MOVEMENT IN ONE DIRECTION • HAIR CELLS ARE ARRANGED IN CLUSTUERS WITH THEIR HAIRS PROJECTING INTO A GELATINOUS MATERIAL CONTAINING NUMEROUS OTOLITHS (SMALL CALCIUM CARBONTE PARTICLES) • THE OTOLITHS ARE HEAVIER THAN ENDOLYMPH IN THE SACCULE AND UTRICLE; GRAVITY PULLS THEM DOWN ON THE HAIRS OF THE RECEPTOR CELLS, THUS CAUSING A CONSTANT SERIES OF ACTION POTENTIALS INDICATING POSITION OF THE HEAD • SEMICIRCULAR CANALS DETECT ROTATION OF THE HEAD DUE TO ENDOLYMPH MOVEMENT AGAINST THE HAIR CELLS

FISH • THE INNER EAR OF A FISH HAS NO EARDRUM, DOES NOT OPEN

FISH • THE INNER EAR OF A FISH HAS NO EARDRUM, DOES NOT OPEN TO THE OUTSIDE OF THE BODY, AND HAS NO COCHLEA, BUT A SACCULE, UTRICLE, AND SEMICIRCULAR CANAL ARE PRESENT • SOUND WAVES ARE CONDUCTED THRU THE SKELETON OF THE HEAD TO THE INNER EAR. THIS SETS OTOLITHS IN MOTION, STIMULATING THE HAIR CELLS • SOME FISH HAVE A WEBERAIN APARATUS, A SERIES OF 3 BONES WHICH CONDUCTS VIBRATIONS FROM THE SWIM BLADDER TO THE INNER NEAR • FISH CAN HEAR HIGHER FREQUENCIES DUE TO THEIR INNER EARS • IN TERRESTRIAL AMPHIBIANS, REPTILES AND BIRDS, SOUND IS CONDUCTED FROM THE TYMPANIC MEMBRANE TO THE INNER EAR BY A SINGLE BONE, THE STAPES

LATERAL LINE SYSTEM • FISH AND AQUATIC AMPHIBS HAVE A LATERAL LINE SYSTEM RUNNING

LATERAL LINE SYSTEM • FISH AND AQUATIC AMPHIBS HAVE A LATERAL LINE SYSTEM RUNNING ALONG BOTH SIDES OF THE BODY – MECHANORECEPTORS CALLED NEUROMASTS CONTAIN HAIR CELL CLUSTERS WHOSE HAIRS ARE EMBEDDED IN A GELATINOUS CAP, THE CAPULA – WATER ENTERS THE SYSTEM THRU NUMEROUS PORES ON THE ANIMAL’S SURFACE AND FLOWS ALONG THE TUBE PAST THE NEUROMASTS – PRESSURE OF MOVING WATER BENDS THE CUPULA CAUSING AN ACTION POTENTIAL IN THE HAIR CELLS – THIS PROVIDES INFO ABOUT THE BODY’S MOVEMENT, DIRECTION, AND VELOCITY OF WATER CURRENTS, AND MOVEMENTS OR VIBRATIONS CAUSED BY PREDATORS AND PREY

LATERAL LINE SYSTEM • FISH AND AQUATIC AMPHIBS HAVE A LATERAL LINE SYSTEM RUNNING

LATERAL LINE SYSTEM • FISH AND AQUATIC AMPHIBS HAVE A LATERAL LINE SYSTEM RUNNING ALONG BOTH SIDES OF THE BODY – MECHANORECEPTORS CALLED NEUROMASTS CONTAIN HAIR CELL CLUSTERS WHOSE HAIRS ARE EMBEDDED IN A GELATINOUS CAP, THE CAPULA – WATER ENTERS THE SYSTEM THRU NUMEROUS PORES ON THE ANIMAL’S SURFACE AND FLOWS ALONG THE TUBE PAST THE NEUROMASTS – PRESSURE OF MOVING WATER BENDS THE CUPULA CAUSING AN ACTION POTENTIAL IN THE HAIR CELLS – THIS PROVIDES INFO ABOUT THE BODY’S MOVEMENT, DIRECTION, AND VELOCITY OF WATER CURRENTS, AND MOVEMENTS OR VIBRATIONS CAUSED BY PREDATORS AND PREY

THE LATERAL LINE SYSTEM

THE LATERAL LINE SYSTEM

INVERTEBRATES • MOST INVERTS HAVE MECHANORECPEPTORS CALLED STATOCYSTS THAT FUNCTION IN THEIR SENSE OF

INVERTEBRATES • MOST INVERTS HAVE MECHANORECPEPTORS CALLED STATOCYSTS THAT FUNCTION IN THEIR SENSE OF EQUILIBRIUM • GRAVITY CAUSES STATOLITHS (DENSE GRANULES) TO SETTLE TO THE LOW POINT IN A CHAMBER, STIMULATING HAIR CELLS IN THAT LOCATION • STATOCYSTS ARE LOCATED ALONG THE BELL FRINGE OF MANY JELLIES AND AT THE ANTENNULE BASES IN LOBSTERS AND CRAYFISH • MANY INSECTS ALSO HAVE “EARS, ” LOCATED ON THEIR LEGS, CONSISTING OF A TYMPANIC MEMBRANE STRETCHED OVER AN INTERNAL AIR CHAMBER CONTAINING RECEPTOR CELLS THAT SEND NERVE IMPULSES TO THE BRAIN

STATOCYST

STATOCYST

CHEMORECEPTION • ANIMALS RELY ON CHEMORECEPTION FOR MANY PURPOSES, INCLUDING LOCATING FOOD AND MATES,

CHEMORECEPTION • ANIMALS RELY ON CHEMORECEPTION FOR MANY PURPOSES, INCLUDING LOCATING FOOD AND MATES, RECOGNIZING TERRITORIES, AND TO ASSIST WITH NAVIGATION • TASTE AND SMELL: – THE PERCEPTIONS OF TASTE AND SMELL DEPEND ON CHEMORECEPTORS THAT DETECT SPECIFIC CHEMICALS IN THE ENVIRONMENT – INSECTS HAVE TASTE RECEPTORS WITHIN SENSORY HAIRS CALLED SENSILLAE ON THE FEET AND MOUTHPARTS; OLFACTORY SENSILLAE ARE USUALYL LOCATED ON THE ANTENNAE – SEVERAL CHEMORECEPTOR CELLS, EACH RESPONDING TO A PARTICULAR CHEMICAL, ARE LOCATED ON EACH TASTING HAIR; INTEGRATING IMPULSES FROM THE DIFFERENT RECEPTORS PERMITS

TASTE RECEPTORS

TASTE RECEPTORS

TASTE BUDS • IN HUMANS AND OTHER MAMMALS, RECEPTOR CELLS FOR TASTE ARE ORGANIZED

TASTE BUDS • IN HUMANS AND OTHER MAMMALS, RECEPTOR CELLS FOR TASTE ARE ORGANIZED INTO TASTE BUDS SCATTERED IN SEVERAL AREAS OF THE TONGUE AND MOUTH • SWEET, SOUR, SALT, AND BITTER ARE DETECTED IN DISTINCT REGIONS OF THE TONGUE • THESE TASTES ARE ASSOCIATED WITH SPECIFIC MOLECULAR SHAPES AND CHARGES THAT BIND TO SEPARATE RECEPTOR MOLECULES

OLFACTOR RECEPTOR CELLS • IN HUMANS, OLFACTORY RECEPTOR CELLS LINE THE UPPER NASAL CAVITY

OLFACTOR RECEPTOR CELLS • IN HUMANS, OLFACTORY RECEPTOR CELLS LINE THE UPPER NASAL CAVITY AND SEND IMPULSES ALONG THEIR AXONS DIRECTLY TO THE OLFACTORY BULB OF THE BRAIN • RECEPTIVE ENDS OF THE CELLS CONTAIN CILIA THAT EXTEND INTO THE COATING LAYER OF MUCUS LINING THE NASAL CAVITY • SPECIFIC RECEPTOR RESPOND TO CERTAIN ODOROUS MOLECULES BY DEPOLARIZING • THE OLFACTORY SENSE RESPONDS TO AIRBORNE CHEMICALS • TASTE AND OLFACTION HAVE DIFFERENT RECEPTORS BUT INTERACT

MOVEMENT & LOCOMOTION • MOVEMENT IS A HALLMARK OF ANIMALS. TO CATCH FOOD, AN

MOVEMENT & LOCOMOTION • MOVEMENT IS A HALLMARK OF ANIMALS. TO CATCH FOOD, AN ANIMAL MUST MOVE THRU THE ENVIRONMENT OR MOVE THE SURROUNDING MEDIUM (WATER OR AIR) PAST ITSELF. WHILE SOME ANIMALS ARE SESSILE, MOST ARE MOBILE AND RELY ON LOCOMOTION TO ACQUIRE FOOD OR TO ESCAPE FROM BECOMING FOOD AND TO LOCATE MATES

LOCOMOTION REQUIRES ENERGY • DIFFERENT MODES OF TRANSPORTATION (RUNNING, FLYING, SWIMMING) HAVE EVOLVED ALONG

LOCOMOTION REQUIRES ENERGY • DIFFERENT MODES OF TRANSPORTATION (RUNNING, FLYING, SWIMMING) HAVE EVOLVED ALONG WITH ADAPTATIONS OF ANIMALS TO OVERCOME THE DIFFICULTIES ASSOCIATED WITH EACH TYPE OF LOCOMOTION • AT THE CELLULAR LEVEL, ALL MOVEMENTS ARE BASED ON THE CONTRACTILE SYSTEMS OF MICROFILAMENTS AND MICROTUBULES

SWIMMING • SWIMIMING ANIMALS MUST OVERCOME RESISTANCE; THUS, MANY ARE FUSIFORM IN BODY SHAPE

SWIMMING • SWIMIMING ANIMALS MUST OVERCOME RESISTANCE; THUS, MANY ARE FUSIFORM IN BODY SHAPE • ANIMALS SWIM IN DIVERSE WAYS

LOCOMOTION ON LAND • A WALKING OR RUNNING LAND ANIMAL MUST SUPPORT ITSELF AND

LOCOMOTION ON LAND • A WALKING OR RUNNING LAND ANIMAL MUST SUPPORT ITSELF AND MOVE AGAINST GRAVITY – INERTIA MUST BE OVERCOME WITH EACH STEP; LEG MUSCLES ACCELERATE A LEG FROM A STANDING START • ANIMALS THAT HOP GENERATE A LOT OF POWER IN THEIR HIND LEGS BY MOMENTARILY STORING ENERGY IN THEIR TENDONS • MAINTAINING BALANCE IS ALSO ESSENTIAL FOR RUNNING, WALKING, OR HOPPING – BIPEDAL ANIMALS KEEP PART OF AT LEAST ONE FOOT ON THE GROUND WHEN WALKING – WHEN RUNNING, MOMENTUM MORE THAN FOOT CONTACT KEEPS THE BODY UPRIGHT • CRAWLING ANIMALS MUST EXERT CONSIDERABLE

FLYING • FLYING ANIMALS DO NOT USE A SKELETON FOR SUPPORT DURING MOTION, AND

FLYING • FLYING ANIMALS DO NOT USE A SKELETON FOR SUPPORT DURING MOTION, AND MUST ALMOST COMPLETELY OVERCOME GRAVITY TO BECOME AIRBORNE • WINGS MUST PROVIDE ENOUGH LIFT TO OVERCOME GRAVITY; THE KEY IS IN THE SHAPE OF THE WINGS

SKELETONS • SKELETONS FUNCTION IN SUPPORT, PROTECTION, AND MOVEMENT • HELP MAINTAIN SHAPE OF

SKELETONS • SKELETONS FUNCTION IN SUPPORT, PROTECTION, AND MOVEMENT • HELP MAINTAIN SHAPE OF AQUATIC ANIMALS • HARD SKELETONS PROTECT SOFT BODY TISSUDES • SKELETONS PROVIDE A FIRM ATTACHMENT AGAINST WHICH MUSCLES CAN WORK DURING MOVEMENT

HYDROSTATIC SKELETONS • HYDROSTATIC SKELETONS CONSISTS OF FLUID HELD UNDER PRESSURE IN A CLOSED

HYDROSTATIC SKELETONS • HYDROSTATIC SKELETONS CONSISTS OF FLUID HELD UNDER PRESSURE IN A CLOSED BODY COMPARTMENT • FOUND IN MOST CNIDARIANS, FLATWORMS, NEMATODES, AND ANNELIDS • CONTROL FORM AND MOVEMENT BY USING MUSCLES TO CHANGE THE SHAPE OF FLUID-FILLED COMPARTMENTS • PROVIDE NO PROTECTION AND COULD NOT SUPPORT A LARGE LAND ANIMAL • THE HYDROSTATIC SKELETON OF EARTHWORMS AND OTHER ANNELIDS ALLOWS FOR THE RHYTHMIC LOCOMOTION (PERISTALSIS) THESE ANIMALS ARE KNOWN FOR

PERISTALSIS AND LOCOMTION

PERISTALSIS AND LOCOMTION

EXOSKELETONS • EXOSKELETONS ARE HARD ENCASEMENTS DEPOSITED ON THE SURFACE OF AN ANIMAL •

EXOSKELETONS • EXOSKELETONS ARE HARD ENCASEMENTS DEPOSITED ON THE SURFACE OF AN ANIMAL • MOLLUSKS ARE SHED (MOLTED) AS THE ANIMALS GROW

ENDOSKELETONS • ENDOSKELETONS ARE HARD SUPPORTING ELEMENTS BURIED WITHING THE SOFT TISSUES OF AN

ENDOSKELETONS • ENDOSKELETONS ARE HARD SUPPORTING ELEMENTS BURIED WITHING THE SOFT TISSUES OF AN ANIMAL • SPONGES POSSES HARD SPICULES OF INORGANIC MATERIAL OR SOFTER PROTEIN FIBERS • ECHINODERMS HAVE OSSSICLES COMPOSED OF MAGNESIUM CARBONATE AND CALCIUM CARBONATE FORMING HARD PLATES BENEATH THE SKIN • CHORDATES HAVE CARTIILAGE AND/OR BONE SKELETONS DIVIDED INTO SEVERAL AREAS

VERTEBRATES • THE VERTEBRATE FRAME IS DIVIDED INTO AN AXIAL SKELETON ( THE SKULL

VERTEBRATES • THE VERTEBRATE FRAME IS DIVIDED INTO AN AXIAL SKELETON ( THE SKULL , VERTEBRAL COLUMN, AND RIB CAGE), AND AN APPENDICULAR SKELETON (LIMB BONES, PECTORAL AND PELVIC GIRDLES) • BONES OF THE VERTEBRATE ACT IN SUPPORT AND AS LEVERS WHEN THEIR ATTACHED MUSCLES CONTRACT

THE HUMAN SKELETON

THE HUMAN SKELETON

MUSCLES • ANIMAL MOVEMENT IS BASED ON CONTRACTION OF MUSCLES WORKING AGAINST SOME KIND

MUSCLES • ANIMAL MOVEMENT IS BASED ON CONTRACTION OF MUSCLES WORKING AGAINST SOME KIND OF SKELETON • MUSCLES ALWAYS CONTRACT ACTIVELY; THEY CAN EXTEND ONLY PASSIVELY • ABILITY TO MOVE A BODY PART IN OPPOSITE DIRECTIONS REQUIRES THAT MUSCLES BE ATTACHED TO THE SKELETON IN ANTAGONISTIC PAIRS

ANTAGONISTIC PAIRS

ANTAGONISTIC PAIRS

SKELETAL MUSCLE • SKELETAL MUSCLE IS BUNDLES OF LONG FIBERS RUNNING THE LENGTH OF

SKELETAL MUSCLE • SKELETAL MUSCLE IS BUNDLES OF LONG FIBERS RUNNING THE LENGTH OF THE MUSCLE; ATTACHED TO BONES AND RESPONSIBLE FOR THEIR MOVEMENT

MUSCLE STRUCTURE

MUSCLE STRUCTURE

MUSCLE FIBERS • EACH FIBER IS A SINGLE CELL WITH MANY NUCLEI; CONSISTS OF

MUSCLE FIBERS • EACH FIBER IS A SINGLE CELL WITH MANY NUCLEI; CONSISTS OF BUNDLES OF SMALLER MYOFIBRILS ARRANGED LONGITUDINALLY • TWO KINDS OF MYOFILAMENTS ARE FOUND IN EACH MYOFIBRIL • 1) THIN FILAMENTS CONSISTS OF 2 STRANDS OF ACTIN AND ONE STRAND OF REGULATORY PROTEIN COILED TOGETHER • 2) THICK FIILAMENTS ARE STAGGERED ARRAYS OF MYOSIN MOLECULES

SARCOMERES • SARCOMERES ARE THE UNIT OF ORGANIZATION OF SKELETAL MUSCLE • Z LINES

SARCOMERES • SARCOMERES ARE THE UNIT OF ORGANIZATION OF SKELETAL MUSCLE • Z LINES ARE THE BORDERS OF THE SARCOMERE; ALIGNED IN ADJACENT MYOFIBRILS • I BANDS AREAS NEAR THE EDGE OF THE SARCOMERE CONTAINING ONLY THIN FILAMENTS • A BANDS ARE REGIONS WHERE THICK AND THIN FILAMENTS OVERLAP AND CORRESPOND TO THE LENGTH OF THE THICK FILAMENTS • H ZONES AREAS IN THE CENTER OF THE A BANDS CONTAING ONLY THICK FILAMENTS

MUSCLE CONTRACTION • MUSCLE CONTRACTION REDUCES THE LENGTH OF EACH SARCOMERE • THIS BEHAVIOR

MUSCLE CONTRACTION • MUSCLE CONTRACTION REDUCES THE LENGTH OF EACH SARCOMERE • THIS BEHAVIOR IS EXPLAINED BY THE SLIDING FILAMENT MODEL – THIN FILAMENTS RATCHET ACROSS THICK FILAMENTS TO PULL THE Z LINES TOGETHER AND SHORTEN THE SARCOMERE; THE MYOFILAMENTS THEMSELVES DO NOT CONTRACT – MYOSIN MOLECULES ON THICK FILAMENTS ATTACH TO ACTIN ON THE THIN FILAMENT TO FORM A CROSSBRIDGE. IT THEN BENDS INWARD, PULLING THE THIN FILAMENT TOWARD THE CENTER OF THE SARCOMERE, BREAKS THE CROSS-BRIDGE, AND FORMS A NEW CROSS-BRIDGE FURTHER DOWN

SLIDING FILAMENT MODEL

SLIDING FILAMENT MODEL

CROSS-BRIDGE FORMATIOIN • ENERGY FOR CROSS-BRIDGE FORMATION COMES FROM THE HYDROLYSIS OF ATP BY

CROSS-BRIDGE FORMATIOIN • ENERGY FOR CROSS-BRIDGE FORMATION COMES FROM THE HYDROLYSIS OF ATP BY THE HEAD REGION OF MYOSIN • MUSCLES STORE ONLY ENOUGH ATP FOR A FEW CONTRACTIONS. MOST OF THE ENERGY IS STORED AS PHOSPHAGENS • CREATINE PHOSPHATE, THE PHOSPHAGEN OF VERTEBRATES, CAN PROVIDE A PHOSPHATE GROUP TO ADP TO MAKE THE ATP AS NEEDED

CROSS-BRIDGE FORMATION

CROSS-BRIDGE FORMATION

MOTOR NEURONS • SKELETAL MUSCLES CONTRACT WHEN STIMULATED BY MOTOR NEURONS – AN ACTION

MOTOR NEURONS • SKELETAL MUSCLES CONTRACT WHEN STIMULATED BY MOTOR NEURONS – AN ACTION POTENTIAL IN THE MOTOR NEURON INNERVATING THE MUSCLE CELL CAUSES THE AXON TO RELEASED A NEUROTRANSMITTER ( E. G. ACETYLCHOLINE) – BINDING ON THE NEUROTRANSMITTER TO THE MUSCLE CELL TRIGGERS AN ACTION POTENTIAL IN THE MUSCLE CELL – THE ACTION POTENTIAL OF THE MUSCLE CELL CAUSES CONTRACTION

CALCIUM IONS • IN A MUSCLE AT REST, MYOSIN-BINDING SITES ON THE ACTIN ARE

CALCIUM IONS • IN A MUSCLE AT REST, MYOSIN-BINDING SITES ON THE ACTIN ARE BLOCKED BY THE REGULATORY PROTEIN STRAND (TROPOMYOSIN) IN THE THIN FILAMENT AND BY THE TROPONIN COMPLEX LOCATED AT EACH BINDING SITE. A CONTRACTION CYCLE IS AS FOLLOWS: – THE WAVE OF DEPOLARIZATION SPREADS RAPIDLY IN THE MUSCLE VIA INFOLDINGS IN THE MUSCLE CELL PLASMA MEMBRANE (TRANSVERSE OR T TUBULES) – THE SARCOPLAMSIC RETICULUM (THE SPECIALIZED E. R. OF THE MUSCLE CELLS) MEMBRANE BECOMES DEPOLARIZED AND RELEASES ITS STORE OF Ca 2+ – THE CALCIUM IONS BINDS TO TROPONIN, CAUSING THE THIN FILAMENT TO CHANGE SHAPE AND EXPOSE THE MYOSIN-BINDING SITES; THE MUSCLE CAN THEN CONTRACT

 • THE CONTRACTION IS TERMINATED AS CALCIUM IS PUMPED OUT OF THE CYTOPLASM

• THE CONTRACTION IS TERMINATED AS CALCIUM IS PUMPED OUT OF THE CYTOPLASM BY THE SARCOPLASMIC RETICULUM; AS THE CALCIUM CONCENTRATIONN FALLS, THE TROPOMYOSIN-TROPONIN COMPLEX AGAIN BLOCKS THE MYOSIN-BINDING SITES

VIDEO: MUSCLE CONTRACTION

VIDEO: MUSCLE CONTRACTION

DIVERSE BODY MOVEMENTS • GRADED CONTRACTIONS OF SKELETAL MUSCLES ARE DUE TO SUMMATION OF

DIVERSE BODY MOVEMENTS • GRADED CONTRACTIONS OF SKELETAL MUSCLES ARE DUE TO SUMMATION OF MULTIPLE MOTOR UNIT ACTIVITY (RECRUITMENT) AND WAVE SUMMATION • MOTOR NEURONS USUALLY DELIVER THEIR STIMULI RAPIDLY, RESULTING IN SMOOTH CONTRACTION TYPICAL OF TETANUS (SUSTAINED CONTRACTION) RATHER THAN THE JERKY ACTIONS OF MUSCLE TWITCHES • A MOTOR UNIT CONSISTS OF A SINGLE MOTOR NEURON AND ALL THE MUSCLE FIBERS IT CONTROLS; ALL FIBERS IN THE MOTOR UNIT CONTRACT AS A GROUP WHEN THE MOTOR NEURON FIRES • AS MORE MOTOR NEURONS ARE RECRUITED BY THE BRAIN, TENSION IN THE MUCLE PROGRESSIVELY INCREASES

FAST AND SLOW MUSCLE FIBERS • DURATION OF MUSCLE CONTRACTION IS CONTROLLED BY HOW

FAST AND SLOW MUSCLE FIBERS • DURATION OF MUSCLE CONTRACTION IS CONTROLLED BY HOW LONG THE CA 2+ CONCENTRATION IN THE CYTOPLASM REMAINS ELEVATED • SLOW MUSCLE FIBERS HAVE LONGERLASTING TWITCHES BECAUSE THEY HAVE LESS SARCOPLASMIC RETICULUM; THUS, CA 2+ REMAINS IN THE CYTOPLASM LONGER – HAVE MANY MITOCHONDRIA, A RICH BLOOD SUPPLY, AND THE OXYGEN-STORING PROTEIN MYOGLOBIN – USED TO MAINTAIN POSTURE SINCE THEY CAN SUSTAIN LONG CONTRACTIONS

 • FAST MUSCLE FIBERS HAVE SHORT DURATION TWITCHES AND ARE USED IN FAST

• FAST MUSCLE FIBERS HAVE SHORT DURATION TWITCHES AND ARE USED IN FAST MUSCLES FOR RAPID, POWERFUL CONTRACTIONS – SOME ARE ABLE TO SUSTAIN LONG PERIODS OF REPEATED CONTRACTIONS WITHOUT FATIGUING

CARDIAC MUSCLE • FOUND ONLY IN THE HEART • IS STRIATED • MUSCLE CELLS

CARDIAC MUSCLE • FOUND ONLY IN THE HEART • IS STRIATED • MUSCLE CELLS ARE BRANCHED, AND THE JUNCTION BTW. CELLS CONTAIN INTERCALATED DISCS THAT ELECTRICALLY COUPLE ALL HEART MUSCLE CELLS, ALLOWING COORDINATED ACTION • CELLS CAN ALSO GENERATE THEIR OWN ACTION POTENTIALS

SMOOTH MUSCLES • LACK STRIATIONS CONTAIN LESS MYOSIN • THEY GENERATE LESS TENSION, BUT

SMOOTH MUSCLES • LACK STRIATIONS CONTAIN LESS MYOSIN • THEY GENERATE LESS TENSION, BUT CAN CONTRACT OVER A GREAT RANGE OF LENGTHS • DO NOT HAVE A TRANSVERSE TUBULE SYSTEM OR A WELL DEVELOPED SARCOPLASMIC RETICULUM; CALCIUM IONS MUST ENTER THE CYTOPLASM THRU THE PLASMA MEMBRANE DURING AN ACTION POTENTIAL • CONTRACTIONS ARE RELATIVELY SLOW BUT THERE IS GREATER RANGE OF CONTROL • THEY ARE FOUND MAINLY IN THE WALLS OF BLOOD VESSELS AND DIGESTIVE TRACT ORGANS

INVERTEBRATE MUSCLES • INVERTS HAVE MUSCLES SIMILAR TO THE SKELETAL AND SMOOTH MUSCLES OF

INVERTEBRATE MUSCLES • INVERTS HAVE MUSCLES SIMILAR TO THE SKELETAL AND SMOOTH MUSCLES OF VERTEBRATES, BUT WITH SOME INTERESTING ADAPTATIONS: – ARTHROPOD SKELETAL MUSCLES ARE VERY SIMILAR TO VERTEBRATE SKELETAL MUSCLE – INSECT WINGS ACTUALLY BEAT FASTER THAN ACTION POTENTIALS ARRIVE FROM THE CNS SINCE THE FLIGHT MUSCLES ARE CAPABLE OF INDEPENDENT, RHYTHMIC CONTRACTIONS – THE THICK FILAMENTS OF MUSCLES IN CLAMS WHICH HOLD THE SHELL CLOSED CONTAIN PARAMYOSIN; THIS UNIQUE PROTEIN ALLOWS THE MUSCLES TO STAY IN A FIXED STATE OF CONTRACTION FOR UP TO A MONTH