Lecture AP Biology Chapter 50 Sensory and motor mechanisms

1.

What is the function of:
▪
▪

Cone cells?
Rod cells?

1.

The perceived pitch of a sound is dependent
on… ?

2.

What is the difference between perception
and sensation?


1.

What is the function of:
▪
▪

Cone cells? Color
Rod cells? Light

The perceived pitch of a sound is dependent
on… ?

wavelength (λ)
1. What is the difference between perception
and sensation?
1.


Chapter 50

Campbell Biology – 9th Edition


The location and function of several types of
sensory receptors
 How skeletal muscles contract
 Cellular events that lead to muscle
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


Eye
Infrared
receptor

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.

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:
Reception receptor detects a stimulus
 Sensation = action potentials reach brain
via sensory neurons



Perception:
Perception information processed in brain


Middle
ear
Inner ear

Outer ear

Stapes
Middle
ear

Incus

Semicircular canals
Skull bones
Auditory nerve,
to brain

Malleus

Pinna

Tympanic
Auditory membrane
canal
Eustachian

tube

Tympanic
membrane

Oval
window

Cochlea
Round
window

Eustachian tube
Tectorial
membrane
Hair cells
Bone
Cochlea duct
Vestibular
canal

Basilar
membrane

Axons of
To auditory
sensory neurons nerve

Auditory
nerve

Tympanic
canal
Organ of Corti


Semicircular canals

Ampulla
Flow
of endolymph
Flow
of endolymph
Vestibular nerve
Cupula
Hairs
Hair
cell

Vestibule
Utricle
Saccule

Nerve fibers
Body movement


Sclera

Choroid

Retina

Ciliary body
Fovea (center
of visual field)

Suspensory
ligament
Cornea
Iris

Optic
nerve

Pupil
Aqueous
humor
Lens
Vitreous humor

Central artery and
vein of the retina
Optic disk
(blind spot)


Retina
Optic nerve

To
brain

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
Photoreceptors

Neurons

Amacrine
cell
Optic
nerve Ganglion
fibers cell

Cone Rod

Horizontal
cell

Bipolar
cell

Pigmented
epithelium




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


Key
Axial skeleton
Appendicular

skeleton

Shoulder
girdle
Sternum
Rib
Humerus
Vertebra
Radius
Ulna

Skull

Examples
of joints

Head of
humerus
Scapula

Clavicle
Scapula
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.

Humerus

Pelvic

girdle
Carpals

Ulna
Phalanges
Metacarpals
Femur

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

Patella

Tibia
Fibula
Ulna

Tarsals
Metatarsals
Phalanges

Radius

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





Muscles always contract
Muscles work in antagonistic pairs to move
parts of body
Human

Grasshopper
Extensor
muscle
relaxes

Biceps
contracts

Biceps
relaxes

Triceps
contracts

Flexor
muscle
contracts

Forearm
flexes

Triceps
relaxes

Tibia
flexes

Extensor
muscle
contracts

Forearm
extends

Tibia
extends

Flexor
muscle
relaxes


Muscle

Bundle of
muscle fibers
Single muscle fiber
(cell)

Attached to bones by tendons
Nuclei
 Types of muscle:
Plasma membrane
Myofibril

 smooth (internal organs)
Light
Z line
band Dark band
 cardiac (heart)
Sarcomere
 Skeletal (striated)
 1 long fiber = single muscle cell
 Each muscle fiber = bundle of
TEM
0.5 µm
I band
A band
I band
myofibrils, composed of:
M line
Thick filaments
(myosin)
▪ Actin: thin filaments
Thin filaments
(actin)
▪ Myosin: thick filaments
Z line
H zone
Z line


Sarcomere

0.5 µm

Z

H
A
Sarcomere
Relaxed muscle fiber

Contracting muscle fiber

Fully contracted muscle fiber

I





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


0.5 µm

1.
Z

H

A
Sarcomere
Relaxed muscle fiber

I

2.

1.
Contracting muscle fiber

Fully contracted muscle fiber

Sarcomere relaxed: actin & myosin
overlap
Contracting:
 Muscle fiber stimulated by motor
neuron
 Length of sarcomere is reduced
 Actin slides over myosin
Fully contracted: actin & myosin
completely overlap

Sliding-filament model: thick & thin
filaments slide past each other to
increase overlap
(Note: Filaments do NOT shorten!)


Motor

neuron axon

Mitochondrion

Synaptic
terminal
T tubule

Sarcoplasmic
reticulum
Myofibril

Plasma membrane
of muscle fiber

Ca2+ released
from sarcoplasmic
reticulum
Sarcomere


Synaptic terminal
of motor neuron
Synaptic cleft

T TUBULE

PLASMA
MEMBRANE
SR

ACh

Ca2+

CYTOSOL

Ca2+


Tropomyosin

Ca2+-binding sites

Actin

Troponin complex

Myosin-binding sites blocked.
Ca2+

Myosinbinding site

Myosin-binding sites exposed.


Hydrolysis of ATP by myosin  cross-bridge formed  thin
filament pulled toward center of sarcomere
Thick filament
Thin filaments

Thin filament
Myosin head (low-energy
configuration)
Thick
filament
Thin filament moves
toward center of sacomere.

Actin

Myosin head (lowenergy configuration)

Cross-bridge
binding site

Myosin head (highenergy configuration)

Cross-bridge


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)