1. Sensory and Motor Mechanisms
Samaneh Bolourchi, Jennifer Tszeng & Athena Zeng

2. Introduction: Sensory Pathways
Sensory receptors transduce stimulus energy & transmit signals to CNS (central nervous system)
Reception: detection via exteroreceptors or interoreceptors
Transduction: stimulus energy converted into ∆ in membrane potential of sensory receptor (receptor potential)
Amplification: stimulus energy strengthens in cells in pathways
Adaptation: decrease in responsiveness
Transmission: action potentials transmitted to the CNS
Perception: constructions formed in brain (ie color, smell, sounds)

3. Introduction: Types of Receptors
Sensory receptors are specialized neurons or epithelial cells that exist singly or in groups with other cell types in sensory organs, such as eyes or ears.
Mechanoreceptors sense physical deformation cause by forms of mechanical energy such as pressure, touch, etc.
Chemoreceptors respond to chemical stimuli.
Electromagnetic receptors respond to various forms of electromagnetic energy such as visible light, electricity, and magnetism.
Thermoreceptors respond to heat or cold and help regulate body temperature by signaling surface and body core temperature.
Pain receptors, or nociceptors, are a class of naked dendrites in the epidermis.

4. Mechanoreceptors Detect mechanical energy
typically consist of ion channels linked to external cell structures (ie hairs) & internal structures (ie cytoskeleton)
Bending/stretching plasma membrane changes permeability to sodium & potassium ions
Type of mechanoreceptor varies greatly between organisms
Crustaceans - vertebrate stretch receptors
Mammals - dendrites of sensory neurons

5. Introduction: Sound & Balance
Ear receives vibrations of moving air and converts into what the mind perceives as sound
Also detects body movement, position & balance
Structures vary between organisms
Terrestrial vertebrates: inner ear is main organ of hearing & equilibrium
Fish/Amphibians: lack certain parts but also contain homologous structures
Invertebrates - statocysts

6. Sound in Humans: Structure of Human Ear
Outer ear
Pinna
Tympanic membrane
Middle ear
Malleus, incus, stapes
Oval window
Eustachian tube
Inner ear
Fluid-filled chambers ie semicircular canals & cochlea

7. Sensory Reception: Hair Cells
Rod-shaped hairs in corti
Vibration of basilar membrane bends hairs against surrounding fluid & tectorial membrane
Bundle direction affects reception
Activates mechanoreceptors
1093; base explanation on 1094; use 1094 diagram

8. Balance in Humans: Utricle & Saccule

9. Sound & Balance: Variation in Organisms
Terrestrial vertebrates: ear has = main organ of hearing & equilibrium
Fish/Amphibians - similar to mammalian ears; lack several structures
Frogs/toads - single middle bone (stapes)
Frogs: small side pocket in saccule - basis for evolution of mammalian cochlea
Birds - cochlea; single middle bone (stapes)

10. Sound & Balance: Fish/Amphibians
lateral line system
have ears outside of body; no eardrum or cochlea; air-filled swim bladder also vibrates in response to sound

11. Sound & Balance in Invertebrates

12. Thermoreceptors Detect heat Located in skin and anterior hypothalamus
Mammals contain a range of thermoreceptor types for particular temperature ranges
Receptor proteins open a calcium channel upon binding certain products
At least five different types of thermoreceptors belong to the transient receptor potential (TRP) family of channel proteins

13. Pain Receptors Nociceptors detect noxious conditions
Essential - stimulus prompts defensive reaction
Animals also produce chemicals to enhance pain perception

14. Touch Receptors usually on skin
Humans contain naked dendrites to detect noxious thermal, mechanical & chemical stimuli
Epidermis, dermis, hypodermis *
structure of connective tissue & location of receptors dramatically affect the type of mechanical energy that best stimulates them

15. Human Integumentary System
Heat
Light touch
Pain
Cold
Hair
Nerve
Connective tissue
Hair movement
Strong pressure
Dermis
Epidermis

16. Chemoreceptors The most sensitive chemoreceptors
are on sensory hairs of
the male silkworm which
detect sex pheromones.
0.1 mm

17. Gustation
In mammals, taste receptors are located in taste buds, most of which are on the surface of the tongue
Each taste receptor responds to a wide array of chemicals, but is most responsive to a particular type of substance.
It is the pattern of taste receptor response that determines perceived flavor.
Transduction in taste receptors occurs by several mechanisms.

19. Olfaction
In mammals, olfactory receptors line the upper portion of the nasal cavity.
The receptive ends of the cells contain cilia that extend into the layer of mucus coating the nasal cavity.
Each olfactory receptor cell expresses only one or a few odorant receptor genes.

21. Electromagnetic Receptors
Respond to various forms of electromagnetic energy such as visible light, electricity, and magnetism.
Photoreceptors detect energy in form of light
Examples:
Snakes—body heat of prey.
Fish—electric currents—prey.
Animals—earths magnetic field. (birds)

22. Types of Eyes the simplest is the eye cup of planarians
In invertebrates, there are compound eyes and single-lens eyes:
Compound: in crustaceans , insects, etc. (have several thousand facets called ommatidia)
Single-lens: jellies, spiders, etc (single lens that focuses light)
In vertebrates
Evolved independently and differ from the single-lens eyes of invertebrates

23. Eye Structure

24. Sensory Transduction
The human retina contains two types of photoreceptors
Rods are sensitive to light but do not distinguish colors
Cones distinguish colors but are not as sensitive
Each rod or cone in the vertebrate retina contains visual pigments consisting of light-absorbing molecules called retinal bonded to membrane proteins called opsin
Rhodopsin (retinal + opsin) is the visual pigment of rods.
Absorption of light by retinal triggers a signal transduction pathway!

25. Signal Transduction cont.
EXTRACELLULAR FLUID
Membrane potential (mV)
– 40
– 70
Dark Light
– Hyper- polarization
Time
Na+
cGMP
CYTOSOL
GMP
Plasma membrane
INSIDE OF DISK
PDE
Active rhodopsin
Light
Inactive rhodopsin
Transducin
Disk membrane
2 Active rhodopsin in turn activates a G protein called transducin.
3 Transducin activates the enzyme phos-phodiesterae(PDE).
4 Activated PDE detaches cyclic guanosine monophosphate (cGMP) from Na+ channels in the plasma membrane by hydrolyzing cGMP to GMP.
5 The Na+ channels close when cGMP detaches. The membrane’s permeability to Na+ decreases, and the rod hyperpolarizes.
1 Light isomerizes retinal, which activates rhodopsin.

26. Signal Transduction (cont.)
Three other types of neurons contribute to information processing in the retina
Ganglion cells, horizontal cells, and amacrine cells
Signals from rods and cones travel from bipolar cells to ganglion cells, which then transmit info to brain by optic nerve (axon of ganglion)
Horizontal cells and amacrine cells function in neural pathways that integrate visual info before sent to brain.
Lateral inhibition causes a greater contrast b/n light and dark (as the horizontal cells inhibit more distant photoreceptors) and this enhances the image, and sharpens its edges.

27. Synaptic activity of rod cells in light and dark
Dark Responses
Rhodopsin inactive
Na+ channels open
Rod depolarized
Glutamate
released
Bipolar cell either
depolarized or
hyperpolarized,
depending on
glutamate receptors
Light Responses
Rhodopsin active
Na+ channels closed
Rod hyperpolarized
No glutamate
hyperpolarized or
depolarized, depending on glutamate receptors

28. Evolution of Visual Perception
All photoreceptors contain similar pigment molecules that absorb light (despite diversity)
Genetic underpinnings of all photoreceptors evolved in the earliest bilateral animals.

29. Vertebrate Skeletal Muscle
Myofibrils consist of:
Thin filaments: two strands of actin
and two strands of a regulatory protein
Thick filaments: staggered arrays
of myosin molecules
Striated Muscle: regular arrangement
of filaments create light/dark band pattern
Sarcomere: basic contractile unit
between Z- lines

32. Types of Muscle Skeletal Muscle Voluntary movements Attatched to bones
Cardiac muscle is similar to skeletal muscle
with striations.
Smooth muscle
lacks striations
lines walls of blood vessels and digestive system organs.

33. Skeletal Systems Support, protection, and movement
Hydrostatic Skeleton – consists of fluid held under pressure in a closed body compartment. Form and movement are controlled by changing the shape of this compartment.
Examples: Flatworms, Nematodes, Annelids, Jellyfish
Exoskeleton – encasement deposited on the surface of an animal. -> chitinous or made from calcium salts, etc.
Examples: Insects, Crustaceans, Mollusks
Endoskeleton – Interior skeleton within muscles and skin. Act as levers when the muscles contract to allow the organism to move.
Examples: Mammals, Birds, Reptiles, Fish, Sponges

34. Locomotion Requires energy to overcome friction & gravity
Swim: friction is major issue; gravity is minor
Land: requires self-support & movement against gravity
Flight: requires wings developed enough to lift & overcome gravity

35. Diseases: Color Blindness
Color-Blindness: due to alterations in the genes for one or more photopsin proteins.
There are different types:
No color vision deficiencies.
with protanopia.
with deuteranopia.
with tritanopia.

36. Diseases (Cont.) \ALS, amyotrophic lateral sclerosis, or Lou Gehrig’s
Myasthenia gravis

37. Bibliography Pictures:
Information:
"color blindness." Encyclopedia Britannica Encyclopedia Britannica Online. 09 Apr <
A. Campbell, Neil, and Jane B. Reece. Biology. San Francisco: Pearson Education, Inc., 05 Jan. 2009
"mechanoreceptor." Encyclopedia Britannica Encyclopedia Britannica Online. 09 Apr <
"inner ear." Encyclopedia Britannica Encyclopedia Britannica Online. 09 Apr <
Helfman G., Collette B., & Facey D.: The Diversity of Fishes, Blackwell Publishing, p 3, 1997, ISBN
Bejan, Adrian; Marden, James H. (2006), "Constructing Animal Locomotion from New Thermodynamics Theory", American Scientist 94 (4): 342–349