Nervous Systems and Sense Organs

Question 1

What are neurons (2)?

Answer 1

functional units of nervous systems

cells that are specialized for high-velocity impulse conduction

Question 2

How is an impulse generated?

Answer 2

impulse is generated (internal or external) within a true nervous system results from a stimulation imposed on the nervous elements

Question 3

What are neuropils?

Answer 3

dense networks of interwoven nerve fibers and their branches and synapses, usually with glial filaments (brains)

Question 4

What is a ganglion?

Answer 4

network of cells forming a nerve center

Question 5

What is a stimulus received by?

Answer 5

receptor/ sense organ

Question 6

How is a stimulus sent and processed? (3)

Answer 6

organ generates an impulse that is conducted along a sensory nerve/ afferent nerve through a series of adjacent neurons to a coordinating center

information is then processed and a response is made

motor nerve/ efferent nerve conducts an impulse from the center to an effector/ muscle where response occurs

Question 7

What is common in all nervous system?

Answer 7

depolarization along the length of each neuron and the neurotransmitter between gaps

Question 8

How is information interpreted within the system for appropriate response? (3)

Answer 8

Each sense receptor has a threshold

nature of receptor

The nervous system is “wired” so that signals coming from a specific type of sense organ are always interpreted in a specific way.

Question 9

What is the threshold?

Answer 9

the minimum strength a stimulus must have to trigger a signal. Different receptors have different thresholds based on how they’re built or how they work.

ex- low threshold for light will respond to light

Question 10

How are receptors constructed?

Answer 10

receptors are constructed to permit only certain stimuli to reach impulse-generating cells

ex- light-sensitive cells in eyes are located beneath the eye surface, where stimuli other than light would not reach

Question 11

Example of the wiring of a nervous system

Answer 11

ex-signals from the eye’s light receptors (photoreceptors) are always understood by the brain as light, no matter what actually caused the signal.

Question 12

What is taxis (2)?

Answer 12

movement related response in response to a stimuli

positive or negative (moving towards or away from light)

Question 13

What does the sense organ type and location depend on?

Answer 13

complexity, mode of life, and body plan of an animal

Question 14

What are mechanoreceptors?

Answer 14

responds to mechanical stimuli like touch, vibrations, and pressure

Question 15

What are nonmechanical stimuli

Answer 15

chemical, light, temperature

Question 16

What is magnetic stimuli seen in?

Answer 16

butterflies to migrate using earth’s magnetic field

Question 17

What are tactile receptors, and what do they depend on?

Answer 17

derived from modified epithelial cells with sensory neurons

depends on structure of body wall

Question 18

What do tactile receptors depend on? (2)

Answer 18

involve projections from the body surface, such as bristles, spines, setae, and tubercles

objects moves these receptors, deforming them, activating neurons

Question 19

How is response integrated in tactile receptors, and an example?

Answer 19

often integrated with other sorts of sensory input

can be combined with chemical recognition of kin

Question 20

What is thigmotaxis?

Answer 20

response to touch

Question 21

What is vibration sensors common in?

Answer 21

tube-dwellers and crustacean predators/ spiders

Question 22

What is trichobothria?

Answer 22

tactile setae in spider appendages that sense airborne vibrations of prey (wing beats)

Question 23

What are georeceptors, and what do they do?

Answer 23

response to pull of gravity

provides orientation to animal

Question 24

What are statocysts? (2)

Answer 24

fluid-filled chamber containing a statolith (solid granule)

lined with touch-sensitive epithelium with hairs containing neurons

Question 25

How do open and closed statolith differ?

Answer 25

statolith can be a sand grain from the environment most are made by the organism itself

Question 26

How does inertia affect the statolith (2)?

Answer 26

resting inertia of the statolith in the fluid causes movement by the animals to change pattern of stimulation of the sensory epithelium when stationary, statolith provides information about orientation to gravity

Question 27

What do georeceptors do in crustaceans?

Answer 27

flow of fluid can provide information about its acceleration relative to its environment

Question 28

When are georeceptors used, and two examples?

Answer 28

used when sensory reception is inadequate burrowing inverts must rely on georeceptors when light is unavailable planktonic animals face orientation issues in deep water or night time

Question 29

How do aquatic insects detect gravity?

Answer 29

detect gravity by using air bubbles trapped in passageways

Question 30

What are proprioreceptors (2)?

Answer 30

responds to mechanically induced changes caused by stretching, compression, bending, and tension gives information about body parts movement and their position

Question 31

What are proprioreceptors associated with, and two examples?

Answer 31

neurons are associated with parts of the body that is being affected associated with appendage joints and body extensor muscles in arthropods specialized muscle cells, elastic connective tissue fibers, joint membranes, that stimulate attached neurons as they are stretched

Question 32

What are phonoreceptors, and what are they found in?

Answer 32

sensitivity to sound annelids and arthropods

Question 33

What are tympanic organs, what do they do, and what groups have them?

Answer 33

tough but flexible layer covering internal air sac that allows it to vibrate when struck by sound stimulates attached sensory neurons crickets, grasshoppers, and cicadas

Question 34

What are slit sense organs?

Answer 34

organs in arachnids that sense sound

Question 35

What are organs of Tomosvary?

Answer 35

myriapod organs that is sensitive to sound

Question 36

What are baroreceptors, and what kind of structures are they?

Answer 36

sensitivity to pressure changes no structures identified

Question 37

What are baroreceptors seen in, and example?

Answer 37

seen in pelagic invertebrates like medusae, ctenophores, cephalopods, and copepods migration in response to water pressure changes

Question 38

What are chemoreceptors, and how do they work (2)?

Answer 38

no sensory structure but irritability of protoplasm itself chemicals in high concentration can induce response chemicals stimulate sensory neurons by contact (diffusing in solution across epithelium)

Question 39

What are aquatic chemoreceptors found in, what do they do (2)?

Answer 39

found in pits or depression where cilia circulates water leaks amino acid into environment through skin/gills/ excretion provides body odor to identify one another

Question 40

What kind of chemoreceptors do arthropods have?

Answer 40

hallow setae/ projections

Question 41

What are photoreceptors (3)?

Answer 41

sensitivity to light possesses light-sensitive pigments absorbs photons to stimulate neurons

Question 42

What groups have photoreceptors?

Answer 42

cnidaria, molluscs, annelids, arthropods, and chordates have evolved eyes for image formation

Question 43

How are different photoreceptors similar (2)

Answer 43

all light receptors are similar in structure photoreceptor protein groups in metazoans - opsins, cryptochromes, and possibly LITE-1

Question 44

What groups have well-developed eyes, and how do they differ?

Answer 44

arthropods, molluscs, polychaetes can range from light perception to image formation

Question 45

What are eyespots?

Answer 45

simplest photoreceptors of unicellular structure

Question 46

Types of multicellular photoreceptors

Answer 46

ocelli/ simple eyes compound eyes complex eyes

Question 47

What are direct ocelli, and how do they differ from inverted ones?

Answer 47

light-sensitive cells facing outwards inverted eyes are common in flatworms and nemerteans - light enters cups is reflected onto the cells to give info on light direction

Question 48

What are compound eyes, and how do they work?

Answer 48

arthropod eyes made of units of ommatidia each ommatidium has its own nerve tract to a large optic nerve and has its own discrete field of vision visual fields overlap, to detect movement

Question 49

What are complex eyes, and how are they structured (3)?

Answer 49

cephalopods)- image formation covered by a cornea light entering is controlled by the iris lens is held by ciliated muscles and focuses light on the retina

Question 50

How do vertebrate and invertebrate complex eyes differ?

Answer 50

vertebrate eyes have inverted retinal layers focus by changing shape of lens inverts moves lns back and forth and compresses the eyeball

Question 51

What are ciliary eyes, and what groups have them?

Answer 51

photoreceptor units derived from or with celia (cnidaria, echinoderms, and chordates)

Question 52

What are rhabdomeric eyes, and what groups have them?

Answer 52

photoreceptor derived from microvilli/ microtubules (flatworms, annelids, arthropods, molluscs)

Question 53

How did photreceptors evolve?

Answer 53

all photoreceptor is homologous through Pax-6 gene (eye development)

Question 54

How did blindness evolve (2)?

Answer 54

blindness can evolve through selective advantage (less energy to make eye) or degredation/ reduction degrades due to disappearing or for photo-stimulation in dark areas

Question 55

What are thermoreceptors, and examples (2)?

Answer 55

can either be physiological response or organs insects, crustaceans, and horseshoe crabs can sense thermal variation leeches can heat-sense to find host

Question 56

What are independent effectors, and examples?

Answer 56

specialized sensory response structures that receive info from the environment and elicits a response without the nervous system nematocysts and colloblasts