Neurones & Hormones

Question 1

What did Ludwig von Bertalanffy do?

Answer 1

developed a “systems theory” through the analysis of population change

Question 2

How are vertebrate and invertebrate nervous and hormonal systems different?

Answer 2

invertebrates often have a single control system, whereas vertebrates have evolved separate system with linking points such as the pituitary and pineal glands

Question 3

Which organisms have a neuroid system?

Answer 3

simple marine metazoans, e.g. the porifera

Question 4

Describe a neuroid system

Answer 4

no defined nervous system and lacking neurones, but there is evidence of conduction of electrical impulses

Question 5

What is epithelial conduction

Answer 5

where the whole epithelium acts as a single receptor organ, found in the hydromedusa and urochordata

Question 6

Where are nerve nets found?

Answer 6

characteristic of cnidaria, but found on the nerve cord of other phyla, such as in molluscan foot and echinoderm arms

Question 7

Describe the arrangement of nerve nets in anthozoa and schyphozoa

Answer 7

linked with symmetrical (bi-directional) chemical synapses.

Question 8

How is the nerve net arranged in the hydrozoa

Answer 8

with direct electrical coupling (like a circuit)

Question 9

Describe the basic structure of an invertebrate CNS

Answer 9

a pair of cerebro-pleural ganglia (CPG) connected to paired, solid nerve cords, usually ventral.

Question 10

Describe the structure of the CNS in a vertebrate chordate

Answer 10

a single ganglionic structure connected to a dorsal, hollow neural tube.

Question 11

Name the 3 main types of unmyelinated neurone

Answer 11

monopolar (CNS to effectors), bipolar (peripheral sense cells) and multipolar (CPG to stretch receptors)

Question 12

What is the equation for the speed of conduction in unmyelinated neurones?

Answer 12

speed of conduction = square root of axonal diameter

Question 13

Give an example of an organism with a giant axon

Answer 13

Loligo squid is the best known example, also found in insects and polychaetes

Question 14

Give 2 ways in which myelination speeds rate of conduction

Answer 14

action potential jumps between nodes of ranvier, and there is less space for ions to leak out

Question 15

What are the 2 major classes of neurotransmitter?

Answer 15

cholinergic (acetylcholine) and adrenergic (nor-adrenaline, octapamine and various neuropeptides) transmitters

Question 16

How do neurones prevent prolonged depolarisation in the post-synaptic neurone?

Answer 16

enzymes such as cholinesterase released into the cleft immediately after transmitter release.

Question 17

What is integration?

Answer 17

an impulse travelling down a neurone may reach a synapse which has several post-synaptic neurones.

Question 18

Describe the neurohormonal system in polychaetes

Answer 18

hormonal substances produced in the neurosectory cells in the CPS that are carried to target sites by neurosecretory axons

Question 19

Describe the neurohormonal system in molluscs

Answer 19

similar means to polychaetes - with hormonal substances carried by neurosecretory axons

Question 20

How did the antifouling agent TBT effect gastropod populations?

Answer 20

TBT caused them to die by mimicking the neurohormone responsible for penile morphogenesis

Question 21

Describe the neurohormonal system of crustaceans

Answer 21

neuro-secretary system similar to those of annelids and molluscs but also have true endocrine organs, the X-organ and sinus gland.

Question 22

How is spawning induced in echinoderms by an endocrine cascade mechanism?

Answer 22

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.

Question 23

Name the two main aspects of reproduction associated with pheromones

Answer 23

co-ordination of spawning aggregations and larval site-selection and metamorphosis