Nervous systems Flashcards
What makes up the nervous system?
CNS and PNS
CNS = brain and nerve chord
PNS = sense organs and receptors
what are neuroid cells?
no neurons or discrte sense organs
contractile cells - myocyctes
- grouped concentrially around pores and major canals
- no synapses, many microtubules and filaments in cytoplasm., mechanical stimulation between adjacent cells.
Porifera
What are nerve nets/ diffuse networks?
Neurons arranged in networks, and synapse with each other - receive stimulus from all directions.
Cnidarians and Ctenophores.
what are Ganglia / Brain and multiple nerve chords? in the simplest form.
CNS 1
Plathelminthes.
Anteriorly - the concentration of nerve tissue forming ganglia (nerve bundle), with optic nerves, and auricles.
> contributed to the development of bilateral symmetry and forward movement.m
Multiple nerve cords running along the length - ladder-like nervous system
Brain and reduced number of nerve chords?
CNS 2
2 subdivisions
- protostome plan
- deuterostome plan
Protostome Plan - brain and reduced neeve chords?
CNS 2
Dorsal brain with ventral nerve chords = probs evolved from ladder-like systems.
Segmented taxa - Annelid and Arthropoda, with segmented ganglia. Increase functioning.
Non-segmented taxa - molluscs, additional ganglia scattered around body, cephalopods have fused ganglia to form a large brain, allows for associative learning.
polychetes are above ground and very active - more developed brain.
look at examples in slides lecture 1 NS slide 6
Deuterostome plan: Brain and nerve chord?
CNS 2
Echinoderms, have a central nerve ring and radial nerve chords
Chordates, have a brain (ganglia) with dorsal nerve chord, simple and somtime very reduced. - nerve chord and anterior swelling, neural gland and small cereba; ganglion.
Diffuse networks arw advantagous for radially symmetrical/ floating animals
Distinction between ganglia and brains is subjective - often depends on size and concentration of nerve tissue.
Size and complexity of brain is linked ot life style.
slide 8
What is PNS?
Tactile touch receptors.
- hair like or birstle strucutres
- linked to snesory nerves
- usaully all over the body but concentrated, on organs of feeding, moving anfd anterior.
- sesillia in arthropoda, hairs, bristles, pores or slits.
What are chemoreceptors?
used to find food, detect chemicals.
Speciallised cells with a receptor process extending through the cuticle or epidermal cells
- sensory nerve fibres extend from base of cell
- hollow, thin bristles with permable cuticle or pores (arhtropoda)
may be scatteredover whole body but concentrated at anterior.
Some unique receptors?
Rheoreceptors in Plathelminthes - detecting water movement
Proprioreceptors in Arhtropoda- stretch receptors, linked ot jointed appendages.
Vision and photoreceptors?
Eyes:
– “Photoreceptor shielded on one side by nearby
pigment which allows the detection of the
direction of a source of light”
* Can be single cell
– “an organ that can produce an image, however
crude, and not simply detect light.”
Orientation, navigation, predator avoidance, finding mates and prey, improved competitive ability diverification of sighted taxa.
interrelatedness between levels of acticvity and quality of vision.
What are pigment cells?
light sensitive, absorb light energy.
colour vision depends on different pigements.
from the retina.
What are photorecptors?
cilia or microvilli - dailiy break down and formation.
What is refraction?
beding of light waves.
occurs in the:
- cornea (treestrial)
- cornea and lens (aquatic)
What does the sharpness of the image depend on?
Refractive index fluid in eyes vs air or water.
Shape of the lens. [ flat, less refraction or round, more refraction ]
Distance between the lens and retina.
Mirrors in aquatic spp. ares of little light.
Vision can be split into 8 type according how light is bent.
Chambered eyes - light is bet by the lens, mirrors - reflect the light onto the retina.
Compound eyes
shadows, refraction and reflection.
How does vision in the sea work?
Change in visual scene with increasing depth has influenced evolution of vision in the sea.
Most light occurs in photic zone, but availability not consistent.
– Decreases with increase in depth
– Dark habitats (under rocks etc.)
– Most animals, including very active spp that rely on good
eyesight, occur in photic zone
- Most variable eye types are found among animals in photic zone.
- In deep environments, animals either have very large eyes or are blind
Simple pit eye
vision in water
Inactive speices live in the dark - no lens, cornea, can detect light direction and intensity.
Plathelminthes, Annelid, Gastropoda
Complex camera-type eye
vision in the sea
Active swimmers and predators.
Have an iris - controls light
cornea - modified cuticle section
true lens does most of the focusing = light detection and intensity, percieve images, discriminitae by size, shape and orientation.
Annelid, Cephalopod, Cnidaria
Single chambered eye with a single mirror?
Vision in the sea
actively swimming bivalvia
images are foremed using a concave mirror.
scallops
Basic compound eye
visionin the sea
sessile/ sedentary animals.
Each receptor is sheilded from neighbour by simple pigmne tube.
Burglar alarm eyes.
Clams
Chiton eyes
Vision in sea
refracting and reflecting superposition compound eye
in areas of poor light quality
krill, shrimp, lobsters
Apposition compound eyes
vision in sea
where there is lots of light
used for navigation - C and sea stars
Hyperiid amphipods (Warrant et al 2004)
– Shallow water, extended field of view
* small eye, similarly sized ommatidia (35 mm)
– 200 m depth, dim downwelling light
* larger eyes, dorsal ommatidia (122 mm) > ventral ommatidia (60mm)
– 400 m, even dimmer downwelling light
* very large eyes, split into dorsal (146 mm ommatidia) & ventral (80 mm ommatidia) eyes
Crustaceans and sea stars.
complex camera-type eye
vioson on land
gastropods - inactive darker environments
lens and cornea
chelicerates - cornea does most of the focusing, up to 8 eyes.
molluscs
refraction superposition and apposition compound eyes?
vision on land
moths - arthropods adapted to dim conditions
dinural insects and many crustaceans
What is hearing?
the response to sound vibrations by mean sof a specail organ for which such virbrations are most effective stimulus.
What is sound?
acoustic energy transferred via particle motion and sound pressure.
What does hearing involve?
dectection of either particle motion or sound pressure or both.
Animals mainly rely on - particle motion in water and vibrations in air particles
What are important sound detecting organs?
statocysts
Mechanorecpetors
Chordotonal or tympanal organs
Cephalopods and decapods.
What are statocycts?
statolith in fluid and hair cells, reacts to particle motion, oreintation and detecting gravitational fields.
What are mechanoreceptors?
setae on surface of body cuticle.
Sensitive to movement in water and air
sensitivity to different frequncies depends on length of hairs.
Aquatic and terrestrial arthropods
What are chordotonal or tymponal organs?
stretch receptors associated woith joints og flexible appendages
receptors cells are embedded in muscle, internal projections of exoskeleton or connective tissue that are connected to CNS.
Respond to vibraions transmited by water through exoskeleton from substrate and air
Aquatic and terrestrial arthropods.
How does insects hear?
Tympanal ears
- evolved independtantly up to 20 groups
- used for predator avoidance
- on wings, legs annd mouth aprts ect.
- Long ranges.
no obvioius pattern in taxonomic distribution of ears.
Set up of tympanal ears?
- thin cuticular membrane, vibrated by the change in pressure as the waves hit the membrane.
- over air filled cavity, for effective detection og pressure changes.
- chordotonal organs with scolopodia, converts mechanical signal to neural siganls.
What the chordotonal organ made up of?
Mutliple scolopidia each composed of scolopale cells, attachemnt cells, acessory cells, and sensory neurons.
How do insects hear without tympanal organs?
Non-tympanal hearing organs on antennae of mosquitos, fruit flies and honey bees.
Johnsons organs
Scolopodia with stretch receptors.
Detect stimulus-induced movement of ends of antennea
Resond to particle velocity
Why is sound important?
- Communication between conspecifics
- esacping predators and finding prey
- Aggression
- Navigation
What are the effects of moise pollution?
Terrestrial invertebrates/insects
– ‘Noisy’ insects modify call frequency to avoid masking
– Mating success inhibited in spp that use vibratory noises in courtship
Marine invertebrates
– Statocyst damage affecting hearing and navigation in giant squid & other cephalopods & jellyfish
– Increased burrowing by clams (may limit feeding)
– Interrupted feeding and reduced predator avoidance in crabs (may lead to starvation and increased susceptibility to predation)
