I.Sensory Systems II.Skeletal Muscles A. Structure B. Contraction C. Nerve Input III.Skeletal Systems IV.Preparation for final Lecture 15 – Ch.50: Muscular & Sensory

What is a Sensory Receptor? Specialized cells that signals when stimulated Receptors named after stimuli they respond to: 1) Thermoreceptors: Heat / Cold 2) Mechanoreceptors: Motion; pressure; gravity 3) Photoreceptors: Light (photons) 4) Chemoreceptors: airborne/waterborne molecules 5) Nociceptors: Pain (chemical release) Sensory Input

Sound: Sensory Input Sound waves are vibrations in fluid (air, water)

Sound: Ear: Sound  Electrical Signal 1) Sound wave enters ear (auditory canal) 3) Vibration passes to middle ear bones 2) Tympanic membrane vibrates Sensory Input Outer earMiddle earInner ear bones of middle ear auditory canal vestibular system (detects head movement and gravity) auditory nerve to brain to pharynx tympanic membrane cochlea auditory tube (Eustachian tube) 4) Inner ear (cochlea) converts vibrations to electrical signal

5 Sound: Sensory Input 5) Inside the cochlea, hair cells are between the basilar and tectorial membranes – vibrations cause the basilar membrane to vibrate, bending hairs against the tectorial membrane.

Two parts of sound are volume and pitch – which is detected by the basilar membrane? 1.Both volume and pitch 2.Volume only 3.Pitch only 4.Neither

Vision: Eye: Light  Electrical Signal Sensory Input Some animals only sense light/dark Many arthropods have a compound eye, where many images are pieced together into a visual mosaic Compound eyes

Vision: Eye placement changes vision: Forward-facing: many carnivores that need depth perception Widely spaced: herbivores - allows better predator detection Sensory Input

Vision: Eye: Light  Electrical Signal Sensory Input Mammals: collects & focuses light waves; transmits signal to brain 1) Light enters via cornea (transparent covering), through the pupil (opening in center of iris) 2) The iris is a pigmented ring of muscle that controls light entry 3) Light is focused on the retina (sheet of photoreceptors) by the lens (transparent surface)

Vision: Sensory Input 4) Muscles attached to lens contract to change the lens shape and focus image on the fovea for any visual distance retina Close object, lens fattens to focus on retina. Distant object, lens thins to focus on retina.

Vision: Sensory Input Abnormally long eyeball: the image is focused in front of the retina: nearsightedness Abnormally short eyeball: the image is focused behind the retina: farsightedness

Vision: Eye: Light  Electrical Signal Rods: Dim-light vision (many but scattered) Cones: Color vision (Red/green/blue) 5) Light on the retina triggers receptors; optic nerve excited Sensory Input fovea blind spot The blind spot is where the optic nerve connects to eyeball No photoreceptors, so images disappear

Which animals would see better at night? 1.Those with more rods 2.Those with more cones 3.Those with larger irises 4.Those with longer eyeballs

Odor/Taste: 1) Chemicals enter nasal cavity; bind to receptors (olfactory epithelium) 2) Olfactory bulb (in brain) excited Nose / Tongue: Chemical  Electrical Signal Sensory Input olfactory dendrites olfactory epithelium nasal cavity air with odor molecules olfactory structure of brain bone nasal cavity olfactory receptors mucus layer

Odor/Taste: 1) Dissolved chemicals enter taste buds on tongue (via taste pore) 2) Chemicals bind with receptors; stimulate nerves Five primary tastes: Sweet / Salt / Bitter / Sour / Umami Olfaction enhances taste Nose / Tongue: Chemical  Electrical Signal Sensory Input The human tongue papillae taste receptor cells Taste bud nerve fibers to brain microvilli taste pore

Which is a correct statement about chemoreceptors? 1.Individual chemoreceptors detect specific tastes 2.Individual chemoreceptors detect specific odors 3.Individual chemoreceptors are specific to both taste and odor 4.Each chemoreceptor can detect more than one taste/odor

Pain is a specialized Chemical Sense: 1) Damaged cells spill chemicals 2) Nociceptors detect tissue damage Sensory Input

18 Self-Check SensationType(s) of receptor; Description of sense Touch Sound Sight Taste Smell Pain

Some senses are unfamiliar to humans

Other Senses: Echolocation: Animal emits pulse - interprets returning signal Electrolocation: Animal produces electrical field; interpret distortion in field Sensory Input Magnetic Field Detection: Animals detect and orient based on earth’s magnetic field

Muscular and skeletal systems Muscles power movement by contracting Bones provide framework for muscles

Muscle Tissue (Muscle = “little mouse”): Exerts force by contracting Chemical energy (ATP) Mechanical Energy Transformation Muscles Movement due to actin microfilaments and myosin strands Slide past one another, change cell shape

connective tissue tendon (to bone) Skeletal muscle Muscle fiber (muscle cell) Myofibril (contains thin and thick filaments) bundle of muscle cells nerve and blood vessels Skeletal Muscles Humans > 700 unique skeletal muscles Muscle connected to bones by tendons

Cross section of fiber muscle fiber T tubules plasma membrane myofibril sarcoplasmic reticulum Skeletal Muscles - Each muscle cell runs length of muscle - Multinucleate - Made up of myofibrils Contractile cylinders of actin and myosin - Each myofibril surrounded by sarcoplasmic reticulum - Fluid with high calcium levels - T-tubules in plasma membrane relay signals

Myofibril myofibril sarcomere thick filament thin filament Z lines Skeletal Muscles Myofibrils of “thick” and “thin” filaments. Each filament is made of protein strands. Filaments arranged in sarcomeres Separated by Z-lines of fibrous protein

Thick and thin filaments tropomyosin thin filament thick filament (myosin) myosin heads accessory proteins troponin actin Skeletal Muscles Thick filaments: made mostly of myosin, have small moveable “heads” Thin filaments: primarily actin, have points to which the myosin heads temporarily attach

binding sites thick filament thin filament ATP ADP myosin head Skeletal Muscles Each actin subunit has binding site for myosin head Contraction exposes binding sites, allowing filaments to bind to one another Myosin heads then repeatedly bend, pull, release, and reattach (using ATP-energy)

Sliding filaments shorten each sarcomere Skeletal Muscles

Neuromuscular junctions between axons and fibers All or nothing response: Skeletal muscle excited All sarcomeres respond Skeletal Muscles postsynaptic membrane axon of motor neuron synaptic terminal synaptic vesicles

Strength of Muscle Contraction  # of Fibers Stimulated Motor Unit: A single motor neuron and all the muscle fibers innervated by it Skeletal Muscles

How do you strengthen a muscle contraction? 1.Engage more muscle fibers 2.Contract each sarcomere further 3.Contract more sarcomeres in a muscle fiber 4.Activate additional myofibrils

Action potential travels through T-channels and opens Ca++ channels in sarcoplasmic reticulum These ions allow binding of thin and thick fibers Ca++ is pumped back out after action potential ends Unless you’re dead Skeletal Muscles

You cannot add muscle fibers You can add more myofibrils Skeletal Muscles muscle Muscle fiber (muscle cell) Myofibril bundle of muscle cells

Hydrostatic skeleton Fluid provides support Muscles contract and move fluid Skeletal System

Exoskeleton Hard shells cover outside of body Muscles contract and move frame at joints Skeletal System

Endoskeleton Internal framework - least common skeleton type Muscles contract and move frame at joints Skeletal System

Movement of bones Joints are where two bones meet Lubricated by cartilage Attached by ligaments Muscles are attached to bone on either side of the joint Attached by tendons Ligaments Origin - attachment to still bone Insertion - attachment to moving bone Vertebrate Skeletons

Things To Do After Lecture 15… Reading and Preparation: 1.Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. 2.Ch. 50 Self-Quiz: #2, 3, 4 (correct answers in back of book) 3.Read chapter 50, focus on material covered in lecture (terms, concepts, and figures!) 4.Prepare for final exam!!! “HOMEWORK” (NOT COLLECTED – but things to think about for studying): 1.Describe the types of sensory information processed by humans – which receptors are responsible for each type? 2.What is the problem in the eye of someone who is near-sighted versus someone who is far-sighted? How do corrective lens fix the problem? 3.Explain how a muscle contracts – include the units down to the sarcomere and their place in a muscle fiber.