AP Biology, Chapter 49
Sensory and Motor Mechanisms

SUMMARY
INTRODUCTION

INTRODUCTION TO SENSORY RECEPTION
	Introduction
	Sensory receptors transducer stimulus energy and transmit signals to the nervous 
	system
	Sensory receptors are categorized by the type of energy they transducer
		1. What stimuli can cause the generation of a neuronal action potential? 
a. Light on an eye receptor
b. Sound vibrations on a ear receptor
c. Pressure on a cutaneous receptor
d. Neurotransmitters from other neurons

PHOTORECEPTORS
	Introduction
	A broad array of photoreceptors has evolved among invertebrates
	Vertebrates have single-lens eyes
		2. Name the eye tunics and note the major functions of each.
			a. Sclera
				i. Thick, white sclera protects
				ii. Anterior sclera or cornea refracts and is sensitive
			b. Black choroid reduces light scattering
			c. Retina contains rod and cone photoreceptors
		3. Describe the anatomical source of the apparent lateral blind spot in our field of vision. 
a. Optic nerve exits through the retina at the optic disk
		4. Explain the difference in rod and cone function and arrangement across the retina.
a. Rods sense gray in dim light at the periphery
b. Cones sense colors and detail at the center
		5. Explain the physical basis of the focusing function of the eye.
			a. Cornea, humors, and lens refract
			b. Refraction is the bending of light as it passes between substances of different 
			density
			c. Curved lenses gather and organize light
	The light-absorbing pigment rhodopsin operates via signal transduction
		6. Compare and contrast the structures of rods and cones.
			a. Similarities
				i. Both are short sensory neurons stuck tip down into the choroid
				ii. Retinal <--> Vitamin A
			b. Differences
				i. Cell shape
				ii. Opsins
	The retina assists the cerebral cortex in processing visual information
		7. Contrast the visual pathways carried by the optic nerves and optic tracts.
			a. Optic nerves carry pathways from individual eyes
			b. Optic tracts carry half-and-half

HEARING AND EQUILIBRIUM
	Introduction
	The mammalian hearing organ is within the inner ear
		8. Identify the structures of the external and middle ear in mammals and list the 				functions of each.
			a. External ear
				i. Pinna; collects sound waves
				ii. Cerumen; earwax protects and inhibits bacterial growth
				iii. Tympanic membrane; transmits vibrations to the ossicles
			b. Middle ear
				i. Auditory or eustachian tube; equalizes pressure across the tympanic 					membrane
				ii. Ossicles; transmit vibrations from the tympanic membrane to the inner 
				ear 
	The inner ear also contains the organs of equilibrium
		9. Identify the structures of the external and middle ear in mammals and list the 				functions of each.
			a. Cochlea; coiled, tapered space containing the mechanoreceptors for hearing
			b. Vestibule; contains the mechanoreceptors for static equilibrium
			c. Semicircular canals; contains the mechanoreceptors for dynamic equilibrium
	A lateral line system and inner ear detect pressure waves in most fishes and aquatic 
	amphibians
	Many invertebrates have gravity sensors and are sound-sensitive
		10. Distinguish the senses of static and dynamic equilibrium.
			a. Static equilibrium senses the direction of the pull of gravity
			b. Dynamic senses the direction of motion on three axes
		11. Compare and contrast the sensation mechanisms for static and dynamic equilibrium. 
			a. Both utilize hair cells embedded in a gelatinous matrix
			b. Static sensation registers the gravitational pull on otoliths
			c. Dynamic sensation registers the angular or rotary motion of the fluid in the 				semicircular canals 

CHEMORECEPTION - TASTE AND SMELL
	Introduction
	Perceptions of taste and smell are usually interrelated
		12. Contrast the varieties of mammalian taste and olfactory receptors.
			a. Five types for taste: sweet, sour, bitter, salty, beefy
			b. Much more variety for olfactory
		13. Contrast the structures and functions of lingual papillae.
			a. Filiform: small, widely-distributed, conical scrapers
			b. Fungiform: medium, scattered, rounded, with taste buds
			c. Circumvallate: large (3mm) with taste buds
		14. Identify the chemical specificities of the five major taste buds.
			a. Sweet: sugars, saccharine, some amino acids, -OH?
			b. Sour: H+
			c. Bitter: alkaloids
			d. Salty: metal ions
			e. Umami: glutamate

MOVEMENT AND LOCOMOTION
	Introduction
	Locomotion requires energy to overcome friction and gravity
	Skeletons support and protect the animal body and are essential to movement
15. List and describe five important functions of bone.
a. Support and anchor soft organs;  legs act as pillars 
b. Protection of brain, heart, lungs, blood vessels, nerves 
c. Movement: skeletal muscles attach and pull as on levers 
d. Mineral storage:  Ca, P, K, Na, S, Mg, Cu in matrix 
e. Blood cell formation in red bone marrow
16. Compare the heft, function and security of limb attachment of the human pectoral and pelvic girdles.
a. Pectoral:  light, flexible for manipulation, easily dislocated 
b. Pelvic:  massive, support weight, more secure
17. Describe two functions of joints.
a. Hold bones together 
b. Allow movement

	Muscles move skeletal parts by contracting
18. List four important functions of muscle tissue.
a. Producing Movement 
b. Maintaining Posture 
c. Stabilizing Joints 
d. Generating Heat
	19. Why do muscle fibers appear striated?
	a. Contain many myofibrils with their dark A bands and light I bands aligned
	20. Define the A band and I band in terms of thick and thin filaments. 
	a. A band = thick filaments with thin filaments overlapping at each end 
	b. I band = thin filaments
	Interactions between myosin and actin underlie muscle contractions
	21. Contrast myosin and actin.
	a. Myosin is in the thick, actin in the thin 
	b. Myosin heads stick out and pull the thin filaments to the center of the 	sarcomere during contraction
	Calcium ions and regulatory proteins control muscle contraction
		22. Describe the readiness of the resting muscle fiber.
a. Resting membrane potential established
b. Ca2+ stored in SR 
c. Myosin heads are pulled back
23. How does the motor neuron initiate an action potential on the sarcolemma? 
	a. Releases acetylcholine (ACh) 
	b. ACh binds to receptors and Na channels open
	c. Na entering changes the voltage, opens more sodium channels 
	d. K channels open in response, voltage returns to normal 
	e. Wave of voltage change = action potential
24. How does the action potential start the contraction?
	a. Causes the release of Ca from the SR 
	b. Ca binds to tropomyosin on the thin filament 
	c. Opens up places for myosin heads to attach and pull
		25. Order the cyclic events in the myosin-actin interaction.
			a. Cross bridge attachment
			b. Power stroke
			c. ATP binding and cross bridge detachment
			d. Hydrolysis of ATP and cocking of the myosin head
	Diverse body movements require variation in muscle activity