Organization of nervous system 2 Flashcards
flatworm (planarian) nervous system
nerve nets; longitudinal nerve cords; brain present, but other ganglia lacking; sensory structures
flatworm (planarian) sensory structures
pigment-cup type eyes; sensory cells on head responds to touch, temperature, light and water chemistry
flatworm (planarian) behaviour
active predators and scavengers; wrap body around prey or impale prey with modified penis; regenerative ability; learning; sexual reproduction
flatworm’s pharynx
located in middle of ventral side; mouth at tip; extends into food, begins digestion externally
differentiate food types (leaves vs stems) through trial and error
earthworms (annelids)
example of annelid learning
show habituation to a stimulus such as light and touch
Annelid nervous system
CNS; PNS; sensory structures
Annelid CNS
brain; pair of ventral nerve cords; giant fibres; subesophageal ganglion
Annelid PNS
on average 3 or 4 pairs of lateral nerves/ganglion
annelid brain
dorsal, anterior; involved in correlation of movement with external conditions
annelid paait of ventral nerve cords
in most annelids, two cords fused; typically on ganglionic swelling/segment
PNS
peripheral nervous system
annelid sensory structures
dispersed photo- and chemoreceptors; mechanoreceptors; statocysts; eyes may be present
annelid eye capabilities (when present)
determine light intensity and light source; some capable of image formation
arthropod behaviour in a nut shell
primarily innate behaviour with many reflex actions and stero-typed stimulus-bound behaviour yet capable of complex behaviours
Examples of arthropod behaviour
predation, migration, courtship strategies, sociality
capable of classical conditioning to positive and negative stimuli
arthropods
tool construction and use, self-medication, farming
arthropods
arthropod nervous system
CNS; PNS; sensory structures
arthropod CNS
dorsal, anterior brain; ventral nerve cord with ganglia; may have medial and lateral giant fibres; subesophageal ganglion
arthropod PNS
on average 2-4 pairs of lateral nerves/ganglion
arthropod sensory sturctures
simple and compound eyes; auditory system; chemoreceptors; mechanoreceptors; gravitational organs
greater diversity of receptors than vertebrates
arthropods e.g. humidity receptors, strain receptors, osmotic receptors
show reflex behaviour, simple conditioning, habituation, learning, and in some, reasoning
molluscs
can learn a T-maze and remember is for a month
snails
greatest cephalization of all invertebrates
cephalopods
mollusc nervous system
specialization of ganglia, including brain regions (lobes); reduction of nerve cords
organism repeatedly and at regular intervals exposed to stimulus of constant strength –> responds less and less vigourously and eventually not at all
habituation
dishabituation
immediate recovery of response upon delivery of a strong stimulus of a different type
characteristics of habituation
spontaneous recovery; dishabituation
learning
change in behaviour due to experience
gill-withdrawal reflex (Aplysia)
stimulus –> sensory neuron –> transmitter release –> motor neuron –> gill withdrawal
gill-withdrawal reflex habituation
repeated stimulus –> sensory neuron –> decreased transmitter release –> motor neuron –> decreased or no withdrawal
gill-withdrawal reflex dishabituation
serotonin –> sensory neuron –> increased transmitter release
Mediterranean octopus
observational learning; associative learning and long-term memory
observational learning in Mediterranean octopus
some octopods can open jar, other can’t; octopus that can’t open jar will learn how by observing con-specific that can
associative learning and long-term memory in Mediterranean octopus
provide food reward or negative stimulus during presentation of human faces; after 6 months, octopus remembers event and shows predictive response to each image
Mollusc CNS (tendency towards)
fusion; reduction of ventral nerve cords; subdivision of ganglia into lobes; specialized ganglia; increased brain volume
Mollusc sense organs
eyes (highly developed in cephalopods); chemoreceptors; mechanoreceptors
mollusc chemoreceptors
general chemical receptors; chemotactile receptors; distance chemoreceptors (olfaction)
mollusc mechanoreceptors
statocysts; touch and pressure receptors; lateral line analogue in some cephalopods
