Nervous system

Question 1

Cell types

Answer 1

neurons are electronically excitable cells that can't divide
Glial cells (neuroglia) provide support and developmental functions. Can divide

Question 2

Neurons

Answer 2

cell body (soma) contains organelles and is site of protein synthesis
Dendrites are highly branched and receive nerve input
Axon propagates nerve impulse to another neuron, muscle or gland

Question 3

nerve cell stimulation

Answer 3

Signals depolarise membrane
membrane potential (-70mV) increases beyond threshold potential (-55mV) which triggers action potential
Some signals hyperpolarise membrane

Question 4

Action potentials

Answer 4

Stimulus produces all or none signal

Impulses jump between nodes of Ranvier in myelinated axons

Signal intensity determined by frequency of impulses

Short refractory period afterwards

Question 5

Synapses

Answer 5

Action potential causes Ca2+ influx which causes fusion of vesicles with pre-synaptic membrane

Effect can be excitatory or inhibitory

Catabolism degrades transmitter or it is taken up back

Question 6

Fly invertebrate model

Answer 6

Drosophila melanogaster
Easy to grow and has short life cycle
complex social, sexual and learning behaviours

Question 7

Forward and reverse genetics

Answer 7

Forward genetics is altering genotype by random mutagenesis to determine how it affects the phenotype. Identifies gene responsible for phenotype

Reverse genetics is altering specific gene (site-directed mutagenesis, RNAi silencing) to determine role in the phenotype.

Question 8

Invertebrate and vertebrate nervous systems

Answer 8

Both have central and peripheral systems
All vertebrates and some invertebrates have brains
Invertebrates have fewer but larger neurons
Vertebrate neuronal axons surrounded by myelin sheaths
Invertebrate CNS often built around digestive tract

Question 9

Caenorhabditis elegans

Answer 9

Transparent roundworm. Invertebrate model
Less than 1000 cells
302 neurons
Genes knocked down by RNAi