Lecture AP Biology Chapter 50 Sensory and motor mechanisms

This chapter 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; slowtwitch and fasttwitch muscle fibers; endoskeleton and exoskeleton.

1 What is the function of:

dependent on… ?

perception and sensation?

1 What is the function of:

dependent on… ?

wavelength (λ)

perception and sensation?

Chapter 50

Campbell Biology – 9 th Edition

 The location and function of several types of sensory receptors

contraction

 Mechanoreceptors: physical stimuli –

pressure, touch, stretch, motion, sound

 Thermoreceptors: detect heat/cold

 Chemoreceptors: 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

Infrared receptor

Some migrating animals, such as these beluga whales, apparently sense Earth’s magnetic field and use the

information, along with other cues, for orientation

 Reception : receptor detects a

stimulus

brain via sensory neurons

in brain

Outer ear Middle ear Inner ear

Pinna Auditory

canal

Tympanic membrane Eustachian tube

Middle ear

Stapes Incus Malleus

Skull bones Semicircular canals

Auditory nerve,

to brain

Tympanic membrane

Oval window Round

window

Cochlea

Eustachian tube

Auditory nerve

Tympanic canal Cochlea duct

Organ of Corti

Vestibular canal Bone

To auditory nerve

Axons of sensory neurons

Basilar

membrane

Hair cells

Tectorial membrane

(blind spot)

Fovea (center

of visual field)

Optic nerve

Retina Choroid

Sclera

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

To brain

Cone Photoreceptors Retina

Rod Neurons

Pigmented epithelium

Bipolar cell

Amacrine cell Horizontal

cell Optic

nerve fibers Ganglion cell

 Hydrostatic : fluid held under

pressure in closed body compartment

 Hydra, nematodes, annelids

surface of animal

 Insects, mollusks, crustaceans

elements buried within soft tissues

 Human bony skeleton

Head of humerus Scapula

Radius

Biceps contracts Human

Triceps

relaxes

Forearm flexes

Biceps relaxes

Triceps

contracts

Forearm extends

Extensor muscle relaxes

Flexor muscle contracts Grasshopper

Extensor muscle contracts

Flexor muscle relaxes

Tibia extends

Tibia flexes

to move parts of body

Bundle of muscle fibers Single muscle fiber (cell)

Plasma membrane

Nuclei Muscle

I band

TEM

A band I band 0.5 µm

M line Thick filaments

(myosin)

Sarcomere H zone

Z line

Thin filaments (actin)

 Each muscle fiber = bundle

of myofibrils, composed of:

0.5 µm

A Relaxed muscle fiber

I

Contracting muscle fiber

Fully contracted muscle fiber

 Z lines – border

 I band – thin actin filaments

 A band – thick myosin filaments

0.5 µm

A Relaxed muscle fiber

I

Contracting muscle fiber

Fully contracted muscle fiber

1 Sarcomere relaxed: actin &

myosin overlap

2 Contracting:

 Muscle fiber stimulated by

motor 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!)

Ca 2+ released from sarcoplasmic reticulum

T TUBULE Synaptic cleft

Synaptic terminal

of motor neuron

ACh

Myosin-binding sites blocked.

Myosin-binding sites exposed.

Tropomyosin Ca2+-binding sites

Myosin-binding site

Ca2+

Thin filaments

Thick filament

Thin filament

Thick filament

Myosin head (low-energy configuration)

Cross-bridge binding site

Myosin head energy configuration) Actin

Hydrolysis of ATP by myosin  cross-bridge formed  thin

filament pulled toward center of sarcomere

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

paralyzes muscles

produce antibodies to acetylcholine

cramps

break actin/myosin bonds; sustained muscle contraction until breakdown (decomposition)