1. Eyes, Ears & …..
Sensory and Motor Mechanisms

2. Sensory Receptors
Mechanoreceptors: stimulated by physical stimuli (i.e. pressure, touch, stretch, motion, sound).
Thermoreceptors: detect hot or cold, maintain body temperature
Chemoreceptors: transmit information on solute concentration in a solution (taste, smell)
Electromagnetic receptors: detect forms of electromagnetic energy (i.e. visible light, electricity, magnetism).
Pain receptors: respond to excess heat, pressure, or chemicals released from damaged or inflamed tissues.

3. Regions of Mammalian Ear
1. Outer Ear: external pinna and auditory canal. Collects sounds and direct them to tympanic membrane (eardrum).
2. Middle Ear: vibrations are conducted through three small bones (malleus – hammer, incus – anvil, stapes – stirrup) and through oval window. Eustachian tube allows air pressure to be equalized between outer and middle ear.
3. Inner Ear: consists of fluid-containing channels lined by membrane situated in bone.
Cochlea – involved in hearing
Organ of Corti – snail shaped structure (here hair cell sound receptors are distorted from vibrations of sound waves)
Semicircular canals – three fluid filled chambers located at right angles to each other, our sense of equilibrium and balance.

4. HowOldAreYourEars? CanYouTrustYourEars? Middle ear Outer ear Inner ear
Fig. 50-8a
Middle ear
Outer ear
Inner ear
Skull bone
Stapes
Semicircular canals
Incus
Malleus
Auditory nerve to brain
Figure 50.8 The structure of the human ear
Cochlea
Oval window
Eustachian tube
Pinna
Auditory canal
Round window
Tympanic membrane
HowOldAreYourEars?
CanYouTrustYourEars?

5. Vision Main parts of the vertebrate eye:
Compound eyes: several thousand light detectors each with own lens (insects and crustaceans)
Single-lens eyes: vertebrates and some invertebrates
Main parts of the vertebrate eye:
The sclera: white outer layer, including cornea (front and transparent)
The choroid: layer of pigmented cells inside sclera
The retina: innermost, contains photoreceptors – rods and cones
Rods – light-sensitive but don’t distinguish colors
Cones – distinguish colors but are not as sensitive to light
The iris: regulates the size of the pupil (hole at the center)
The lens: focuses light on the retina
The optic disk: a blind spot in the retina where the optic nerve attaches to the eye

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

7. Vertebrate Skeletal Muscle
Contract/relax: antagonistic pairs w/skeleton
Muscles: bundle of….
Muscle fibers: single cell w/ many nuclei consisting of….
Myofibrils: longitudinal bundles composed of….
Myofilaments:
Thin~ 2 strands of actin protein and a regulatory protein
Thick~ myosin protein
Sarcomere: repeating unit of muscle tissue, composed of….
Z lines~sarcomere border
I band~only actin protein
A band~actin & myosin protein overlap
H zone~central sarcomere; only myosin

8. Sliding-filament model
Theory of muscle contraction
Sarcomere length reduced
Z line length becomes shorter
Actin and myosin slide past each other (overlap increases)

9. Actin-myosin interaction
1- Myosin head hydrolyzes ATP to ADP and inorganic phosphate (Pi); termed the “high energy configuration”
2- Myosin head binds to actin; termed a “cross bridge”
3- Releasing ADP and (Pi), myosin relaxes sliding actin; “low energy configuration”
4- Binding of new ATP releases myosin head
Creatine phosphate~ supplier of phosphate to ADP

10. Muscle contraction regulation, I
Relaxation: tropomyosin blocks myosin binding sites on actin
Contraction: calcium binds to toponin complex; tropomyosin changes shape, exposing myosin binding sites

11. Muscle contraction regulation, II
Calcium (Ca+)~ concentration regulated by the….
Sarcoplasmic reticulum~ a specialized endoplasmic reticulum
Stimulated by action potential in a motor neuron
T (transverse) tubules~ travel channels in plasma membrane for action potential
Ca+ then binds to troponin

12. Muscle contraction