1. What is the function of:▪ Cone cells?▪ Rod cells?

2. The perceived pitch of a sound is dependent on… ?

3. What is the difference between perception and sensation?

1. What is the function of:▪ Cone cells? Color▪ Rod cells? Light

2. The perceived pitch of a sound is dependent on… ?wavelength (λ)

1. What is the difference between perception and sensation?

Chapter 50Campbell Biology – 9th Edition

The location and function of several types of sensory receptors

How skeletal muscles contractCellular events that lead to muscle

contraction

Mechanoreceptors: physical stimuli – pressure, touch, stretch, motion, sound

Thermoreceptors: detect heat/coldChemoreceptors: transmit solute conc.

info – taste (gustatory), smell (olfactory)Electromagnetic receptors: detect

EM energy – light (photoreceptors), electricity, magnetism

Pain receptors: respond to excess heat, pressure, chemicals

This rattlesnake and other pit vipers have a pair of infrared receptors, one between each eye and nostril. The organs are sensitive enough to detect the infrared radiation emitted by a warm mouse a meter away.

Eye

Infraredreceptor

Some migrating animals, such as these beluga whales, apparently sense Earth’s magnetic field and use the information, along with other cues, for orientation.

ReceptionReception: receptor detects a stimulus SensationSensation = action potentials reach

brain via sensory neurons

PerceptionPerception: information processed in brain

Outer earMiddle

ear Inner ear

Pinna Auditorycanal

Tympanicmembrane

Eustachiantube

Middleear

Stapes

Incus

Malleus

Skull bones

Semicircular canals

Auditory nerve,to brain

Tympanicmembrane

Ovalwindow Round

window

Cochlea

Eustachian tube

Auditory nerve

Tympaniccanal

Cochlea duct

Organ of Corti

Vestibularcanal

Bone

To auditorynerve

Axons ofsensory neurons

Basilarmembrane

Hair cells

Tectorialmembrane

Semicircular canals

Flowof endolymph

Vestibular nerve

Nerve fibersVestibule

Utricle

Saccule

Ampulla

Flowof endolymph

Cupula

Body movement

Hairs

Haircell

Cornea

Ciliary body

Suspensoryligament

Iris

Pupil

Aqueoushumor

Lens

Vitreous humor

Central artery andvein of the retina

Optic disk(blind spot)

Fovea (centerof visual field)

Opticnerve

RetinaChoroidSclera

Compound eyes: several thousand ommatidia (light detectors) with its own lens; insects & crustaceans

Vertebrates: Rods: sense light Cones: color vision Rhodopsin: light-

absorbing pigment that triggers signal transduction pathway that leads to sight

Retina

Optic nerve

Tobrain

Cone

Photoreceptors

Retina

RodNeurons

Pigmentedepithelium

Bipolarcell

Amacrinecell Horizontal

cellOpticnervefibers

Ganglioncell

Hydrostatic: fluid held under pressure in closed body compartment Hydra, nematodes, annelids

Exoskeletons: hard encasements on surface of animal Insects, mollusks, crustaceans

Endoskeleton: hard supporting elements buried within soft tissues Human bony skeleton

Shouldergirdle

Scapula

Clavicle

Sternum

SkullAppendicularskeleton

Axial skeleton

Key

Rib

Humerus

Vertebra

Radius

Examplesof joints

Fibula

Ulna

Tibia

Pelvicgirdle

Carpals

Phalanges

Metacarpals

Femur

Patella

TarsalsMetatarsalsPhalanges

Ulna

Pivot joints allow us to rotate our forearm at the elbow and to move our head from side to side.

Ulna

Hinge joints, such as between the humerus and the head of the ulna, restrict movement to a single plane.

Humerus

Ball-and-socket joints, where the humerus contacts the shoulder girdle and where the femur contacts the pelvic girdle, enable us to rotate our arms and legs and move them in several planes.

Head ofhumerus

Scapula

Radius

Bicepscontracts

Human

Tricepsrelaxes

Forearmflexes

Bicepsrelaxes

Tricepscontracts

Forearmextends

Extensormusclerelaxes

Flexormusclecontracts

Grasshopper

Extensormusclecontracts

Flexormusclerelaxes

Tibiaextends

Tibiaflexes

Muscles always contractMuscles work in antagonistic pairs

to move parts of body

Bundle ofmuscle fibers

Single muscle fiber(cell)

Plasma membrane

Nuclei

Muscle

Myofibril

Dark band

Sarcomere

Z lineLightband

I bandTEM

A band I band0.5 µm

M lineThick filaments(myosin)

SarcomereH zoneZ line

Thin filaments(actin)

Z line

Attached to bones by tendons

Types of muscle: smooth (internal organs) cardiac (heart) Skeletal (striated)

1 long fiber = single muscle cell Each muscle fiber =

bundle of myofibrils, composed of:▪ Actin: thin filaments▪ Myosin: thick filaments

Sarcomere

0.5 µm

Z HA

Relaxed muscle fiber

I

Contracting muscle fiber

Fully contracted muscle fiber

Z lines – border I band – thin actin filaments A band – thick myosin

filaments

Sarcomere

0.5 µm

Z HA

Relaxed muscle fiber

I

Contracting muscle fiber

Fully contracted muscle fiber

1. Sarcomere relaxed: actin & myosin overlap

2. Contracting: Muscle fiber stimulated by

motor neuronmotor neuron Length of sarcomere is

reduced Actin slides over myosin

3. Fully contracted: actin & myosin completely overlap

Sliding-filament model: thick & thin filaments slide past each other to increase overlap

(Note: Filaments do NOT shorten!)

Ca2+ releasedfrom sarcoplasmicreticulum

MitochondrionMotorneuron axon

Synapticterminal

T tubule

Sarcoplasmicreticulum

Myofibril

Plasma membraneof muscle fiber

Sarcomere

Ca2+CYTOSOL

Ca2+

SR

PLASMAMEMBRANET TUBULESynaptic cleft

Synaptic terminalof motor neuron

ACh

Myosin-binding sites blocked.

Myosin-binding sites exposed.

Tropomyosin Ca2+-binding sitesActin Troponin complex

Myosin-binding site

Ca2+

Thin filaments

Thick filament

Thin filament

Thick filament

Myosin head (low-energyconfiguration)

Cross-bridgebinding site

Myosin head (high-energy configuration)

Actin

Cross-bridge

Myosin head (low-energy configuration)

Thin filament movestoward center of sacomere.

Hydrolysis of ATPHydrolysis of ATP by myosin by myosin cross-bridge formed cross-bridge formed thin thin filament pulled toward center of sarcomerefilament pulled toward center of sarcomere

Speed of muscle contraction:Speed of muscle contraction:•Fast fibers – brief, rapid, powerful contractions•Slow fibers – sustain long contractions (posture)

ALS (Lou Gehrig’s disease): degeneration of motor neurons, muscle fibers atrophy

Botulism: block release of acetylcholine, paralyzes muscles

Myasthenia gravis: autoimmune disorder, produce antibodies to acetylcholine

Calcium deficiency: muscle spasms and cramps

Rigor mortis (after death): no ATP to break actin/myosin bonds; sustained muscle contraction until breakdown (decomposition)