Neurones & Hormones Flashcards
What did Ludwig von Bertalanffy do?
developed a “systems theory” through the analysis of population change
How are vertebrate and invertebrate nervous and hormonal systems different?
invertebrates often have a single control system, whereas vertebrates have evolved separate system with linking points such as the pituitary and pineal glands
Which organisms have a neuroid system?
simple marine metazoans, e.g. the porifera
Describe a neuroid system
no defined nervous system and lacking neurones, but there is evidence of conduction of electrical impulses
What is epithelial conduction
where the whole epithelium acts as a single receptor organ, found in the hydromedusa and urochordata
Where are nerve nets found?
characteristic of cnidaria, but found on the nerve cord of other phyla, such as in molluscan foot and echinoderm arms
Describe the arrangement of nerve nets in anthozoa and schyphozoa
linked with symmetrical (bi-directional) chemical synapses.
How is the nerve net arranged in the hydrozoa
with direct electrical coupling (like a circuit)
Describe the basic structure of an invertebrate CNS
a pair of cerebro-pleural ganglia (CPG) connected to paired, solid nerve cords, usually ventral.
Describe the structure of the CNS in a vertebrate chordate
a single ganglionic structure connected to a dorsal, hollow neural tube.
Name the 3 main types of unmyelinated neurone
monopolar (CNS to effectors), bipolar (peripheral sense cells) and multipolar (CPG to stretch receptors)
What is the equation for the speed of conduction in unmyelinated neurones?
speed of conduction = square root of axonal diameter
Give an example of an organism with a giant axon
Loligo squid is the best known example, also found in insects and polychaetes
Give 2 ways in which myelination speeds rate of conduction
action potential jumps between nodes of ranvier, and there is less space for ions to leak out
What are the 2 major classes of neurotransmitter?
cholinergic (acetylcholine) and adrenergic (nor-adrenaline, octapamine and various neuropeptides) transmitters
How do neurones prevent prolonged depolarisation in the post-synaptic neurone?
enzymes such as cholinesterase released into the cleft immediately after transmitter release.
What is integration?
an impulse travelling down a neurone may reach a synapse which has several post-synaptic neurones.
Describe the neurohormonal system in polychaetes
hormonal substances produced in the neurosectory cells in the CPS that are carried to target sites by neurosecretory axons
Describe the neurohormonal system in molluscs
similar means to polychaetes - with hormonal substances carried by neurosecretory axons
How did the antifouling agent TBT effect gastropod populations?
TBT caused them to die by mimicking the neurohormone responsible for penile morphogenesis
Describe the neurohormonal system of crustaceans
neuro-secretary system similar to those of annelids and molluscs but also have true endocrine organs, the X-organ and sinus gland.
How is spawning induced in echinoderms by an endocrine cascade mechanism?
extracts of radial nerves injected into the body cavity containing a gonad stimulating hormone, that causes the release of meiosis-inducing substanc, that induces the production of maturation-promoting factor.
Name the two main aspects of reproduction associated with pheromones
co-ordination of spawning aggregations and larval site-selection and metamorphosis
