BBB tutorial THREE:

21 April Glasgow Caledonian University

Snippets from discussions

In this tutorial we concentrated on the essentials of neuronal functioning, focussing on the kinds of membrane potentials which characterise the nerve cell and the ways in which neurons inter-communicate.

I forgot to mention the following two items of information-

1. The date of the June tutorial in Glasgow has been changed from 16^th to 30^th June.
2. The tutorial notes are now being collated on my home-grown web site at www.David.Curtis.care4free.net - but then you probably know that already if you're reading this on your web browser!!!

We worked our way through the Revision exercise on Chapter 3 of Book 2, which had been introduced in Tutorial Two, with the usual digressions to cover some points in a little more detail. The latter included the following:-

1. The generalised structure of the cell membrane.
2. The relative concentrations of the important ions (sodium, potassium, chloride, organic) involved in nerve cell membrane potentials (Fig. 3.4, p. 49 of Book 2).
3. The action potential: its dependence on the opening and closing of voltage-gated channels for sodium and potassium.
4. Graded potentials (either synaptic or sensory receptor) may depolarise the membrane - if reaches threshold then action potential (also called a 'spike') occurs. The spike is an all-or-none event. The various kinds of nerve cell membrane potentials may cause initiation of others.
5. Speed of conduction is faster in larger diameter axons, but even faster if axon is myelinated - because the signal 'leaps' from one node of Ranvier to the next (saltatory conduction). Myelin evolved only in the vertebrates.
6. 'Classical' chemical synapse is described in Book 2, but there is a great diversity of types of synapse . Broadly speaking, the major distinction is between electrical and chemical synapses (p.73 of Bk.2).
7. Synapses may be excitatory (EPSP = depolarisation) or inhibitory (IPSP = hyperpolarisation). Summation (temporal and/or spatial) may occur as the integration of all the inputs to a neuron. Different patterns of interacting neurons provide for information processing in the nervous system.
8. The interactions of neurons can give rise to patterns of impulses, e.g. the central pattern generator (CPG) of locusts (Fig.7.26 of Book2). This CPG then interacts with sensory inputs in the control of the flight muscles (Fig. 7.28 of Bk.2)

STUDY HINT 
to cope with the complexity of the vertebrate nervous system (especially human):

1. Start off with the basic divisions of the nervous system.
2. Add in the major functional (and anatomical) regions of the CNS and PNS.
3. Remember that our CNS develops as a mid-dorsal fold in the embryo, which sinks in to form a tube; at the front end this tube broadens and folds to become the brain while the rest is the spinal cord. The main components of the brain develop in the three divisions of the brain (fore-, mid- and hind-brain), as shown in Fig. 8.5 of Bk.2.
4. Then look at Fig. 8.32 of Bk. 2, showing the flow of information through the mammalian CNS. This just puts in a little more detail compared to step 2 above. Note the functionally pivotal role of the hypothalamus.
5. More details on the hypothalamus are shown in Figs. 10.3 and 10.4 as well as Table 10.1 of Bk. 2., summarising the different inputs and outputs to this extremely important part of the brain.

Revision

Back to BBB home file