Sensory and Motor Mechanisms

Chapter 50 Sensory and Motor Mechanisms PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Key concepts 1. Sensory mechanisms convert various stimuli into neural codes. 2. Motor mechanisms exert action by skeletons and muscles. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 50-1 Can a moth evade a bat in the dark?

Fig. 50-2 Membrane potential (mv) Membrane potential (mv) Membrane potential (mv) Membrane potential (mv) Response of a crayfish stretch receptor to bending Slight bend: weak stimulus 50 70 Weak receptor potential Dendrites Stretch receptor Action potentials 0 70 0 1 2 3 4 5 6 7 Time (sec) Brain perceives slight bend. 1 2 3 Axon 4 Brain Large bend: strong stimulus 1 Reception Muscle 50 70 Strong receptor potential 0 70 0 Action potentials 1 2 3 4 5 6 7 Time (sec) Brain perceives large bend. 2 Transduction 3 Transmission 4 Perception

slowly more quickly very rapidly Some of Adrian s first recordings from a very small number of nerve fibers in the sensory nerves of cat s toe (1926). Adrian s Laws: 1. The nerve impulse (action potential) is all-or-none 2. The strength of stimulus is coded by the firing frequency

Sensory adaptation is a decrease in responsiveness to continued stimulation

Perception Perceptions are the brain s construction of stimuli Stimuli from different sensory receptors travel as action potentials along different neural pathways ( label line ) Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Types of Sensory Receptors Based on energy transduced, sensory receptors fall into five categories: Mechanoreceptors Chemoreceptors Electromagnetic receptors Thermoreceptors Pain receptors Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 50-3 Heat Sensory receptors in human skin Gentle touch Pain Cold Hair Epidermis Dermis Hypodermis Nerve Connective tissue Hair movement Strong pressure

Fig. 50-4 0.1 mm

Fig. 50-5 Eye Infrared receptor (a) Rattlesnake (b) Beluga whales

Fig. 50-6 Ciliated receptor cells Cilia Statolith Sensory axons

Fig. 50-7 Many arthropods sense sounds with body hairs that vibrate or with localized ears consisting of a tympanic membrane and receptor cells Tympanic membrane 1 mm

Fig. 50-8 Outer ear Middle ear Inner ear The structure of the human ear Skull bone Incus Stapes Semicircular canals Malleus Auditory nerve to brain Cochlear duct Bone Auditory nerve Vestibular canal Pinna Auditory canal Tympanic membrane Oval window Round window Cochlea Eustachian tube Tympanic canal Organ of Corti Hair cells Tectorial membrane Hair cell bundle from a bullfrog; the longest cilia shown are about 8 µm (SEM). Basilar membrane Axons of sensory neurons To auditory nerve

Fig. 50-9 Signal Membrane potential (mv) Signal Membrane potential (mv) Signal Membrane potential (mv) Sensory reception by hair cells Hairs of hair cell Neurotransmitter at synapse Sensory neuron More neurotransmitter 50 50 Receptor potential 70 70 Less neurotransmitter 50 70 Action potentials 0 0 0 70 70 70 0 1 2 3 4 5 6 7 Time (sec) 0 1 2 3 4 5 6 7 Time (sec) 0 1 2 3 4 5 6 7 Time (sec) (a) No bending of hairs (b) Bending of hairs in one direction (c) Bending of hairs in other direction

Fig. 50-10 Transduction in the cochlea Axons of sensory neurons Oval window Vestibular canal Apex Flexible end of basilar membrane Apex Basilar membrane 500 Hz (low pitch) 1 khz 2 khz Stapes { Vibration 4 khz Base Round window Tympanic canal Fluid (perilymph) Basilar membrane Base (stiff) 16 khz (high pitch) 8 khz

Fig. 50-11 Semicircular canals Flow of fluid Vestibular nerve Cupula Hairs Hair cells Vestibule Utricle Axons Body movement Saccule The utricle and saccule contain granules called otoliths that allow us to detect gravity and linear movement Three semicircular canals contain fluid and allow us to detect angular acceleration such as the turning of the head

Fig. 50-12 The lateral line system in a fish Lateral line Surrounding water Scale Lateral line canal Epidermis Opening of lateral line canal Cupula Segmental muscles Fish body wall Lateral nerve Sensory hairs Hair cell Supporting cell Axon

Taste in Mammals There are five taste perceptions: sweet, sour, salty, bitter, and umami (elicited by glutamate) Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 50-13 Sugar molecule Sweet receptor Tongue G protein Taste pore Sugar molecule SENSORY RECEPTOR CELL Phospholipase C Taste bud Sensory receptor cells PIP 2 Sensory neuron Nucleus IP 3 (second messenger) IP 3 -gated calcium channel Sodium channel Sensory transduction by a sweet receptor ER Ca 2+ (second messenger) Na +

Fig. 50-14 Relative consumption (%) How do mammals detect different tastes? RESULTS 80 60 40 20 0.1 1 10 Concentration of PBDG (mm); log scale PBDG receptor expression in cells for sweet taste No PBDG receptor gene PBDG receptor expression in cells for bitter taste

Fig. 50-15 Smell in humans Brain Action potentials Odorants Nasal cavity Olfactory bulb Bone Odorant receptors Plasma membrane Epithelial cell Chemoreceptor Cilia Odorants Mucus

Fig. 50-16 Ocelli and orientation behavior of a planarian Ocellus Light Photoreceptor Visual pigment Ocellus Nerve to brain Screening pigment

Fig. 50-17 2 mm (a) Fly eyes Cornea Crystalline cone Lens Rhabdom Axons Photoreceptor (b) Ommatidia Ommatidium

Fig. 50-18 Ciliary body Sclera Choroid Retina Suspensory ligament Fovea (center of visual field) Cornea Iris Pupil Optic nerve Aqueous humor Lens Vitreous humor Optic disk (blind spot) Central artery and vein of the retina

Fig. 50-19 Focusing in the mammalian eye Ciliary muscles contract. Suspensory ligaments relax. Choroid Retina Ciliary muscles relax. Suspensory ligaments pull against lens. Lens becomes thicker and rounder. (a) Near vision (accommodation) Lens becomes flatter. (b) Distance vision

Fig. 50-20 Activation of rhodopsin by light Rod Outer segment Disks INSIDE OF DISK cis isomer Light Enzymes Cell body CYTOSOL Synaptic terminal Rhodopsin Retinal Opsin trans isomer

Membrane potential (mv) Fig. 50-21 Receptor potential production in a rod cell Light Inactive rhodopsin Active rhodopsin Transducin INSIDE OF DISK Disk membrane Phosphodiesterase GMP CYTOSOL cgmp EXTRACELLULAR FLUID Plasma membrane Sodium channel Na + 0 Dark Light 40 70 Time Hyperpolarization Na +

Fig. 50-22 Dark Responses Light Responses Rhodopsin inactive Rhodopsin active Na + channels open Na + channels closed Rod depolarized Rod hyperpolarized Glutamate released No glutamate released Bipolar cell either depolarized or hyperpolarized Bipolar cell either hyperpolarized or depolarized

Fig. 50-23 Retina Neurons Retina Photoreceptors Cone Rod Choroid Light Optic nerve To brain Light Ganglion cell Optic nerve axons Amacrine cell Bipolar cell Horizontal cell Pigmented epithelium

Fig. 50-24 Right visual field Right eye Optic chiasm Left eye Left visual field Optic nerve Lateral geniculate nucleus Primary visual cortex

Evolution of Visual Perception Photoreceptors in diverse animals likely originated in the earliest bilateral animals Melanopsin, a pigment in ganglion cells, may play a role in circadian rhythms in humans Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 50-25 Muscle The structure of skeletal muscle Bundle of muscle fibers Nuclei Single muscle fiber (cell) Plasma membrane Myofibril Z lines Sarcomere TEM M line 0.5 µm Thick filaments (myosin) Thin filaments (actin) Z line Sarcomere Z line

Fig. 50-26 According to the sliding-filament model, filaments slide past each other longitudinally, producing more overlap between thin and thick filaments Z Sarcomere M Z 0.5 µm Relaxed muscle Contracting muscle Fully contracted muscle Contracted Sarcomere

Fig. 50-27-4 Thin filaments Thick filament Myosin-actin interactions underlying muscle fiber contraction ATP ATP Myosin head (lowenergy configuration Thin filament Thick filament Thin filament moves toward center of sarcomere. Actin Myosin binding sites Myosin head (lowenergy configuration ADP P i Myosin head (highenergy configuration ADP + P i ADP P i Cross-bridge

Fig. 50-28 Tropomyosin Actin Troponin complex Ca 2+ -binding sites (a) Myosin-binding sites blocked Ca 2+ Myosinbinding site (b) Myosin-binding sites exposed

Fig. 50-29 Synaptic terminal Motor neuron axon T tubule Sarcoplasmic reticulum (SR) Myofibril Plasma membrane of muscle fiber Sarcomere Synaptic terminal of motor neuron Mitochondrion Ca 2+ released from SR Synaptic cleft T Tubule Plasma membrane ACh SR Ca 2+ ATPase pump Ca 2+ ATP CYTOSOL Ca 2+ ADP P i

Fig. 50-30 Spinal cord Motor unit 1 Motor unit 2 Synaptic terminals Nerve Motor neuron cell body Motor neuron axon Muscle Muscle fibers Tendon

Fig. 50-31 Tension Summation of twitches Tetanus Summation of two twitches Single twitch Action potential Pair of action potentials Time Series of action potentials at high frequency

Oxidative fibers rely on aerobic respiration to generate ATP Glycolytic fibers use glycolysis as their primary source of ATP Glycolytic fibers have less myoglobin than oxidative fibers, and tire more easily In poultry and fish, light meat is composed of glycolytic fibers, while dark meat is composed of oxidative fibers Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 50-32 Human Grasshopper Biceps contracts Extensor muscle relaxes Tibia flexes Triceps relaxes Forearm flexes Flexor muscle contracts Biceps relaxes Extensor muscle contracts Tibia extends Triceps contracts Forearm extends Flexor muscle relaxes

Types of Skeletal Systems The three main types of skeletons are: Hydrostatic skeletons (lack hard parts) Exoskeletons (external hard parts) Endoskeletons (internal hard parts) Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 50-33 Longitudinal muscle relaxed (extended) Circular muscle contracted Circular muscle relaxed Longitudinal muscle contracted Crawling by peristalsis Bristles Head end Head end Head end

Fig. 50-34 Skull Examples of joints Head of humerus Scapula 1 Shoulder girdle Clavicle Scapula Sternum Rib Humerus Vertebra 2 3 1 Ball-and-socket joint Radius Ulna Pelvic girdle Humerus Carpals Phalanges Metacarpals Femur Patella Ulna 2 Hinge joint Tibia Fibula Tarsals Metatarsals Phalanges 3 Ulna Pivot joint Radius

Fig. 50-35 Energy-efficient locomotion on land

Fig. 50-36 Measuring energy usage during flight

Energy cost (cal/kg m) Fig. 50-37 RESULTS Animals specialized for swimming expend less energy per meter traveled than equivalently sized animals specialized for flying or running 10 2 Flying Running 10 1 10 1 Swimming 10 3 1 10 3 10 6 Body mass (g)

You should now be able to: 1. Distinguish between the following pairs of terms: sensation and perception; sensory transduction and receptor potential; tastants and odorants; rod and cone cells; oxidative and glycolytic muscle fibers; slow-twitch and fast-twitch muscle fibers; endoskeleton and exoskeleton 2. List the five categories of sensory receptors and explain the energy transduced by each type Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3. Explain the role of mechanoreceptors in hearing and balance 4. Give the function of each structure using a diagram of the human ear 5. Explain the basis of the sensory discrimination of human smell 6. Identify and give the function of each structure using a diagram of the vertebrate eye Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

7. Identify the components of a skeletal muscle cell using a diagram 8. Explain the sliding-filament model of muscle contraction 9. Explain how a skeleton combines with an antagonistic muscle arrangement to provide a mechanism for movement Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings