I. Sensory Systems A. Sound B. Sight C. Taste/Smell II. Skeletal Muscles A. Structure B. Contraction C. Nerve Input III.Prep for final Lecture 15 – Ch.50: Sensory & Muscular

What is a Sensory Receptor? Specialized neurons that signal when stimulated Receptors named after stimuli they respond to: 1) Thermoreceptors: heat & cold 2) Mechanoreceptors: pressure/touch, stretch, motion, sound 3) Electromagnetic Receptors: light, electricity, magnetism 4) Chemoreceptors: osmolarity, gustation, olfaction 5) Nociceptors: pain – thermal, chemical, mechanical 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 4) Inner ear (cochlea) converts vibrations to electrical signal Outer ear Middle ear Inner ear Skull bone Semicircular canals Auditory nerve to brain Cochlea Eustachian tube Tympanic membrane Auditory canal

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. Cochlear duct Bone Auditory nerve Organ of Corti Tectorial membrane Basilar membrane Hair cells Axons of sensory neurons To auditory nerve Vestibular canal Tympanic canal

Sound: Sensory Input 6) The basilar membrane varies in stiffness along its length – different regions vibrate in response to different frequencies. Tympanic membrane Cochlea Stapes (a) Point A A A 10 Tympanic canal Basilar membrane Point B B B 20 Point C C C 30 Vestibular canal Axons of sensory neurons (b) Distance from oval window (mm) 6,000 Hz 1,000 Hz 100 Hz Relative motion of basilar membrane What category of sensory receptors detect sound?

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

Vision: Sensory Input 1) Light enters via cornea (transparent covering), through pupil (opening in center of iris - pigmented ring of muscle that controls light entry) 2) Light focused by lens on retina (sheet of photoreceptors) Sclera Cornea Iris Pupil Aqueous humor Lens Vitreous humor Central artery and vein of the retina Optic nerve Fovea Retina Neurons Photoreceptors Rod Cone Optic nerve fibers Pigmented epithelium

Vision: Sensory Input 3) 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. The blind spot is where the optic nerve connects to eyeball No photoreceptors, so images disappear

Vision: 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 Rod Synaptic terminal Cell body Outer segment Disks Cone Rod CYTOSOL INSIDE OF DISK Retinal Opsin Rhodopsin:

Odor/Taste: 1) Dissolved chemicals enter taste buds on tongue (via taste pore) 2) Chemicals bind with receptors; stimulate nerves 3) Tastants bind one of five types of receptor cells: Olfaction enhances taste Nose / Tongue: Chemical  Electrical Signal Sensory Input Papillae Papilla Taste buds (a) Tongue Key Sweet Salty Sour Bitter Umami Taste bud Sensory neuron Sensory receptor cells Food molecules Taste pore (b) Taste buds

Odor/Taste: 1) Chemicals enter nasal cavity; bind to receptors 2) Humans can detect more than 1000 different odorants due to different receptors Sensory Input Odorants Brain Nasal cavity Receptors for different odorants Plasma membrane Odorants potentials Action Bone Epithelial cell Chemo- receptor Cilia Mucus

13 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

Skeletal Muscles Humans have > 700 unique skeletal muscles Each muscle has multiple fibers – each fiber many muscle cells Muscle Bundle of muscle fibers Nuclei Single muscle fiber (cell) Plasma membrane Myofibril Z lines Sarcomere Each muscle cell runs length of muscle - Multinucleate - Filled with myofibrils of contractile units = sarcomeres

Skeletal Muscles Myofibrils of “thick” (myosin) and “thin” filaments (actin). Each filament is made of protein strands. Filaments arranged in sarcomeres Separated by Z-lines of fibrous protein Z lines Sarcomere TEM 0.5  m Z line M line Sarcomere Z line Thick filaments (myosin) Thin filaments (actin)

Skeletal Muscles Each myofibril surrounded by sarcoplasmic reticulum - Fluid with high calcium levels - T-tubules in plasma membrane relay signals Synaptic terminal Axon of motor neuron T tubule Sarcoplasmic reticulum (SR) Myofibril Plasma membrane of muscle fiber Sarcomere Ca 2  released from SR Mitochondrion

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

Action potential travels through T-tubules and opens Ca 2+ channels in sarcoplasmic reticulum Ca 2+ allows binding of thin and thick fibers Ca 2+ is pumped back out after action potential ends Skeletal Muscles

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

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

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: #1, 2, 3, 4, 5 (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.