1. Figure 49.0 Bat locating a moth

2. Sensory Transduction Amplification Transmission Integration
Sensory receptors transduce stimulus energy and transmit signals to the nervous system.
Four Basic Processes Must Occur For You To Sense The Environment
Sensory Transduction
Amplification
Transmission
Integration
Sensory Transduction:
The stimulus must be changed into an action potential of the receptor cell
The stimulus could be a stretch receptor and increase ion flow or a neurotransmitter binding to a receptor.
That is, a change in permeability to sodium ions.
Amplification
Usually accomplished by additional structures associated with a complex organ.
Eye: struck by photons of light and this must be amplified 100,000 times.
Transmission
To the CNS
Pain “receptors” are actually sensory neurons as opposed to a receptor.
Integration
Sensory Adaptation: where the body decreases its responsiveness during continued stimulation.
Sensitivity of receptors: the threshold is different for each receptor
Some receptors can change sensitivity and become hypersensitive
Integration within the CNS

3. Figure 49.2 Sensory transduction by a taste receptor

4. Umm, Umm, Good. . . Taste Receptors
Taste buds are not as localized on the tongue like we once thought.
But a sweet, bitter, sour, salty, molecule binds to its particular receptor.
Signal is amplified and sets off a Signal Transduction Pathway
Potassium ion channels will be closed by the action of second messengers
Sodium moves into the cell causing depolarization.
This causes calcium ion uptake into the receptor (like at the end of the presynaptic neuron)
Neurotransmitters are released that stimulate a sensory neuron and subsequent action potential.

5. Figure 49.3 Sensory receptors in human skin

6. Figure 49.4 Mechanoreception by a hair cell

7. Figure Specialized electromagnetic receptors: Rattle snake with infrared receptors, beluga whale pod
Infrared receptors: sense infrared radiation given off by prey (mouse or jogger’s ankle)

8. Figure 49.7 Eye cups and orientation behavior of a planarian
Side with no screening pigment
Side with no screening pigment
Eye Cups of Planarian
Provides info about light intensity and direction but no image
Light enters the eye cup and enters on side where there is no screening pigment.
Brain compares the rate of stimulation on each side and turns animal to minimize the impulses so the animal turns away from light and reaches the shaded region.

9. Figure 49.8 Compound eyes Image Forming
Found in insects and crustaceans
Consists of lots of ommatidia
Each ommatidia has its own lens to focus light
Differences in light intensity produce a mosaic image.
Detects movement

10. Figure 49.8x1 SEM of compound eye

11. Figure 49.8x2 Insect vision: A black-eyed Susan (Rudbeckia hirta) as humans see it and in ultraviolet light as visible to an insect

12. Figure 49.9 Structure of the Vertebrate Eye
Forms the cornea
Forms the iris
Highest Conc. Of Cones
Single Lens Eyes: squid, octopus, mollusks, humans.
lens focuses light on the retina
light enters through the pupil as allowed by an adjustable iris, passes through the lens and hits the retina
Glaucoma or increased pressure : blockage of the ducts that drain the aqueous humor; can lead to blindness by compressing the retina
Aqueous Humor: help to focus light on retina
Vitreous humor: helps to focus light on retina.
Retina: ;contains the rod and cone cells
More rod cells than cone cells
Rods: do not distinguish color; more sensitive to light
Cones: takes more light to stimulate the cones; sees the color
Fish, amphibians, reptiles, birds have strong color vision.
Most mammals are nocturnal therefore have more rods
No photoreceptors: “blind spot”

13. Figure 49.10 Focusing in the mammalian eye
When ciliary muscles contract, the suspensory ligaments relax and allow the lens to “round.”

14. The Biochemistry of Sight
Rods are responsible for noncolor dim light; cones are responsible for color vision in bright light.
Rod photoreceptor: made up of outer and inner segments, cell body, synaptic region where the nerve impulse is passed to a retinal nerve cell.
Outer Segment: made up of stacks of discs containing rhodopsin molecules. The rhodopsin contains a molecule called retinal and opsin that can actually exist in two forms.
Light hits retinal; retinal changes shape, separates from opsin and the opsin now has a different shape. The retinal changes color from purple to yellow.
This is “bleaching” of the rhodopsin

15. Transducin then activates an enzyme that breaks down cGMP.
The Biochemistry of Sight (cont’d)
This change in the rhodopsin activates a G protein (related to cGMP) called transducin.
Transducin then activates an enzyme that breaks down cGMP.
The low levels of cGMP cause sodium ion channels to close which hyperpolarizes the rod cell and changes the amount of neurotransmitter it releases (it decreases)
In the dark, there is plenty of cGMP and it is bound to sodium channels, keeping them open so it already has a relatively depolarized resting potential. Sodium ions are continually entering the outer segment of the cell. The neurotransmitter, glutamate is released.
Glutamate stimulates the bipolar cells in the retina.

16. Biochemistry of Vision (cont’d)
Glutamate binds to receptors on the bipolar cells and stimulates some and inhibits others depending on the receptor type.
Once again, when light flashes, you’ll have a decrease in cGMP, the sodium channels close and hyperpolarization occurs which decreases glutamate levels and this excites or inhibits bipolar cells depending on the receptor type.

17. Night Vision
Night vision is not very sharp. You can have trouble seeing an object even when looking straight at it because the image is being directed to an area where there are lots of cones- the fovea.
Looking a little to the side, has the image falling on a rod-rich area of the retina and the image is much sharper.

18. Figure 49.11 Photoreceptors in the vertebrate retina
Rhodopsin: a transmembrane protein

19. Figure 49.12 Effect of light on retinal

20. Figure 49.13 From light reception to receptor potential: A rod cell’s signal-transduction pathway

21. Figure 49.14 The effect of light on synapses between rod cells and bipolar cells

22. Color Vision
3 kinds of cone cells, each with slightly different types of opsin molecules.
Each cone type absorbs different wavelengths: blue, red and green
Intermediate wavelengths of light excite different classes of these cones in different proportions.

23. Figure 49.15 The vertebrate retina

24. Visual Processing: There are several layers of cells
Rods and cones synapse with bipolar cells
Bipolar cells synapse with ganglion cells
It is the ganglion cells that carry the impulses to the optic nerve and then to the brain.
Horizontal and amacrine cells carry information laterally and integrate it before passing it along to the ganglion cells.
Lateral Inhibition: this is the adjustment of the horizontal cells to sharpen edges of an image.

25. Impulses in optic nerves from left and right eye cross at optic chiasm at the base of cerebral cortex BUT:
Optic nerve branches from left field of vision of left eye and the optic nerve branches from left field of vision of right eye pass to the right side of brain.
Optic nerve branches from right field of vision of right eye and branches from right field of vision of left eye pass to left side of brain.
All impulses go to the visual cortex at the occipital lobe of cerebrum

26. Figure 49.16 Neural pathways for vision

27. Figure 49.15x Photoreceptor cells

28. Figure 49.17 Structure and function of the human ear

29. The Hearing Organ Is Within The Inner Ear
Sound waves travel through the auditory canal to the ear drum (tympanic membrane)
Tympanic membrane separates the outer ear (pinna and aud. Canal) from middle ear
Middle Ear: malleus (hammer), incus (anvil), stapes (stirrup)
From the the 3 bones, the vibrations pass to a membrane, the oval window.
Middle ear also contains the Eustachian tube: connects the mouth (pharynx) with the middle ear to equalize pressure on both sides of the middle ear.

30. Figure 49.17 Structure and function of the human ear

31. Sound waves vibrate tympanic membrane
3. Inner ear consists:
Cochlea
Fluids
Organ of Corti
And the process is:
Sound waves vibrate tympanic membrane
Vibes are transferred through the bones of middle ear to oval window
Oval window contacts the cochlea which contains 3 canals
Vestibular canal and tympanic canal which both contain fluid called perilymph
Cochlear duct which contains endolymph

32. Figure 49.17 Structure and function of the human ear

33. (cont’d)
Floor of the organ of Corti is the actual “hearing” structure. Components are:
Basilar Membrane which forms the floor of the organ of Corti upon which various cell types are attached.
Hair Cells which will pick up the vibrations from the cochlear fluid and move against the:
Tectorial Membrane
Vibes are carried into fluid of vestibular canal and into the tympanic canal.

34. Figure 49.17 Structure and function of the human ear

35. Basilar Membrane picks up vibrations, transfers them to hair cells which brush against the tectorial membrane causing depolarization of hair cells, neurotransmitter release and an action potential in the sensory neuron going to the auditory nerve.

36. Figure 49.17 Structure and function of the human ear

37. Determination of Volume and Pitch
Volume is determined by the amount of vibration traveling through the perilymph and endolymph. This produces more bending of the hair cells and more action potentials.
Pitch can be differentiated because the basilar membrane has an uneven thickness along its length.
As the endolymph causes the basilar membrane to vibrate
Within the basilar membrane are fibers of various lengths that vibrate at a length’s specific frequency thus producing vibrations at specific points of the basilar membrane.
At the specific point of basilar membrane are specific hair cells that get vibrated and stimulate specific sensory cells which send messages to specific auditory areas of the cerebral cortex.

38. Figure 49.18 How the cochlea distinguishes pitch

39. Perception of Balance
3 semicircular canals are oriented in various planes and each has an ampulla at its base.
Within the ampulla is a gelatinous material called the cupula with its projecting hair cells.
When the head rotates the endolymph in the canals stimulates hair cells. If head’s rotation is at constant speed, the firing of the hair cells is minimalized. But if you are rotating and then stop suddenly, the endolymph “sloshes” around, stimulates hair cells with no time for adjustment and you may feel dizzy.
Saccule and Utricle with their accompanying hair cells inform us of head’s position of up, down or sideways. Otoliths rest on hair cells and will shift in response to movement, bending hair cells.

40. Figure 49.19 Organs of balance in the inner ear

41. Figure 49.20 The lateral line system in a fish
Fish possess an inner ear containing a utricle, saccule and semicircular canals.
There is no eardrum so vibrations from water travel through skeleton of head to the inner ears which stimulate otoliths and hair cells.
Swim bladder, which is filled with air, vibrates with sound and transfers vibes to inner ear. Swim bladders are found in most bony fish (not sharks)
Lateral Line System is made up of receptors (neuromasts) in sensory pits that detect water current via the stimulation of hair cells.

42. Figure 49.21 The statocyst of an invertebrate
Hair cells or cilia surround a chamber containing statoliths (grains of sand). Statoliths are present in jellies’ bells, crayfish antennae.

43. Figure An insect ear

44. Figure 49.x2 Salmon follow their noses home

45. Figure 49.23 The mechanism of taste in a blowfly

46. Figure 49.23x Sensillae (hairs) on the foot of an insect

47. Figure 49.24 Olfaction in humans

48. Figure 49.25 The cost of transport

49. Figure 49.x3 Swimming

50. Figure 49.x4 Locomotion on land

51. Figure 49.x5 Flying

52. Figure 49.26 Energy-efficient locomotion on land

53. Figure 49.27 Peristaltic locomotion in an earthworm

54. Figure 49.28a The human skeleton

55. Figure 49.28b The human skeleton

56. Figure 49.30 The cooperation of muscles and skeletons in movement

57. Figure 49.31 The structure of skeletal muscle
Myofibrils are made up of:
1) actin or thin filaments
2) myosin or thick filaments
I Band: where only the actin filaments are located.
A Band: where the overlap of actin and myosin filaments is located.

58. Figure 49.31x1 Skeletal muscle (Voluntary)
Skeletal muscles are multinucleated and striated.

59. Figure 49.31x2 Muscle tissue

60. Figure 49.32 The sliding-filament model of muscle contraction
Sarcomere shortens during muscle contraction or distance from Z line to Z line decreases.

61. Figure One hypothesis for how myosin-actin interactions generate the force for muscle contraction (Layer 1)
ATP is bound to myosin head
We call this the low energy position or the state when no contraction is occurring.
ATP has to be hydrolyzed for contraction to proceed: ATP  ADP + Pi

62. Figure One hypothesis for how myosin-actin interactions generate the force for muscle contraction (Layer 2)
4. ATP has now been hydrolyzed
5. We now say the myosin head is energized or in a high energy state
6. In this high energy state it can now bind to the action filaments. This binding occurs in special locations on the actin filaments.

63. Figure One hypothesis for how myosin-actin interactions generate the force for muscle contraction (Layer 3)

64. Figure One hypothesis for how myosin-actin interactions generate the force for muscle contraction (Layer 4)

65. Figure 49.34 Hypothetical mechanism for the control of muscle contraction
Muscle Contraction Animation Another Animation

66. The Interaction of Actin and Myosin
Prior to contraction, the myosin binding sites are covered by a protein called tropomyosin.
Upon nerve impulse stimulation (by acetylcholine) of a muscle cell, an action potential travels through the muscle cell via the Transverse or T-tubules to the sarcoplasmic reticulum. Calcium ions are released from the sarcoplasmic reticulum.
Action potential travels through Transverse or T-tubules through the muscle (not muscle cell). Recall that a muscle is made up of thousands of muscle cells.
Calcium ions will bind to a protein called troponin
The Ca-troponin complex will pull or move the tropomyosin off of the binding sites for myosin.
Now the myosin binds to action and slides it forward, thus muscle contraction occurs.

67. Figure 49.35 The roles of the muscle fiber’s sarcoplasmic reticulum and T tubules in contraction

68. Figure 49.36 Review of skeletal muscle contraction

69. Motor Units
Definition: a motor unit is a motor neuron and all the muscle cells (fibers) it innervates.
If one neuron innervates lots of muscle fibers you have “gross” control (a large motor unit) but if one neuron innervates very few fibers you have very precise control of small group of fibers (a small motor unit).
As you are required to lift more and more weight, your body recruits more motor units and therefore more muscle fibers.

70. Figure 49.38 Motor units in a vertebrate muscle

71. Fast and Slow Twitch Muscle Fibers
Fast Twitch Fibers
Anaerobic, so few mitochondria
Lots of sarcoplasmic reticulum to remove calcium for fast contractions
Slow Twitch Fibers
Aerobic, so lots of mitochondria
Few sarcoplasmic reticulum so calcium remains in muscle fibers for sustained contractions.
Contain myoglobin producing the “dark” meat.

72. Other Types of Muscle Tissue
Cardiac Muscle
It’s striated (contains actin and myosin)
Contains intercalated disks: located between cardiac cells to pass on the electrical signals from one cell to all others throughout the heart
Does not require a motor neuron for stimulation. The plasma membrane can generate its own depolarizations, producing an action potential and therefore cardiac muscle cell contraction
Action potential lasts longer

73. Other Types of Muscle Tissue (cont’d)
Smooth Muscle Tissue (involuntary)
Found mainly in digestive system (stomach, esophagus, intestine) and the blood vessels.
Lacks the striations but contains the actin and myosin. It is just that the action and myosin are not arranged in such a way to produce the striations.
Lacks T tubules and a well-developed sarcoplasmic reticulum. Calcium ions enter the cells through the plasma membrane and this is much slower so the contractions in smooth muscle are slow.
Long, slow sustained contractions
Each muscle cell has a nucleus

74. Invertebrate Muscle Tissue
Vertebrates and invertebrates have similar skeletal muscle cells and smooth muscle cells.
Insect Flight Muscles: these muscles can contract faster than the action potentials can arrive
One action potential can generate 50 “wing beats.”

75. Figure 49.38x Motor units in a vertebrate muscle

76. Figure 49.29 Posture helps support large land vertebrates, such as bears, deer, moose, and cheetahs

77. Figure 49.37 Temporal summation of muscle cell contractions

78. Figure Chemoreceptors in an insect: Female silk moth Bombyx mori releasing pheromones; SEM of male Bombyx mori antenna

79. Figure 49.x1 Chemoreceptors: Snake tongue

80. Figure 49.6bx Beluga whale pod