Exciting cells: fundamentals of neurobiology

Aims

This course aims to:

• introduce you to the basic principles of how electrical signals are generated and propagated in the body
• introduce you to the mechanisms and purpose of synapses between excitable cells
• introduce some of the key historical experiments which have led to our understanding of these things

Course content

The University of Cambridge has long been instrumental in shaping what we know about the function of excitable cells, several Nobel Prizes in this area having been awarded to Cambridge researchers. In this short course, Professor Matt Mason from the Department of Physiology, Development & Neuroscience will draw on this rich history to explain how nerve, muscle and other excitable cells work. 

We shall begin with the fundamental topic of electrochemical gradients, which drive ions across membranes. Electrochemical gradients arise from an imbalance between electrical and concentration-based forces, and we shall explore where these come from and how we could calculate an ion’s ‘equilibrium potential’, at which point forces are balanced. If an ion is maintained away from that point, we can harness its tendency to cross a membrane in a particular direction, a principle which is central to cellular physiology in all organisms. Excitable cells such as sensory receptor cells, neurons and muscle cells are special in that they can exploit electrochemical gradients to develop and propagate electrical signals – a phenomenon ultimately underlying everything that humanity has ever accomplished! Professor Mason will explain how these cells work from basic principles, going on to explore how nerve cells intercommunicate, activate muscles, make decisions and transduce information from the environment into the electrical signals that our brains can understand. The four lectures will be supported by an experimental class in which you will be able to stimulate and record electrical signals from your own arm and measure the conduction velocity of your ulnar nerve. 

This course represents an introduction to the fundamentals of neurobiology, at a level equivalent to what we teach first-year undergraduate science students here in Cambridge. It will be suitable for those who have a scientific background but who have not studied neurobiology, or those who would like to consolidate what they have learned elsewhere. 

What to expect on this course

This course will be taught in the form of four lectures plus one experimental practical class. Although the lectures will follow a traditional, podium-based format, Professor Mason likes to make his lectures as interactive as possible, so expect questions to be asked of the audience! There will be plenty of opportunity to ask individual questions too, as we go along. The experimental practical class, involving the stimulation of your own ulnar nerve at the elbow, will be held in the Department of Physiology, Development & Neuroscience on the Downing Site, University of Cambridge. Being based on material that we deliver our first-year undergraduates here in Cambridge, the course will be quite fast-paced and will assume knowledge of science to an A-level standard.

Course sessions

1. Electrochemical gradients and resting potentials: A proper understanding of how nerves use electrical signalling requires that we first consider the basics. In this session, we shall explore the nature of the driving forces on ions which might make them tend to cross a membrane in one direction or another. We shall explore the concepts of electrochemical gradients, Nernst equilibrium potentials and, bringing this all together, where the resting membrane potential of a cell really comes from – avoiding common misconceptions about the role of the sodium pump! We shall see how electrochemical gradients are put to use not just for electrical signalling by excitable cells, but for driving secondary active transport processes in all living cells.

    

2. Action potentials: Now that we understand why there is an electrochemical gradient for sodium ions causing them to want to enter a nerve cell, we can now explore how the cell harnesses this in order to propagate the electrical signals called action potentials. Action potentials are the means by which nerve cells can send information long distances around the body, at velocities which can exceed 100 metres/second! We will look at how the experiments of Nobel Laureates from the University of Cambridge, including the famous work on squid giant axons by Alan Hodgkin and Andrew Huxley, contributed to our current understanding of how nerves work.

    

3. Synapses: Nerve cells must communicate with other cells in order to pass on their messages, often through chemical synapses. We shall examine the neuromuscular junction, between a nerve fibre and a skeletal muscle cell, as an example of how and why this chemical communication takes place, and look at how it can be disrupted by poisons such as botox. The more complicated synapses between neurons within the brain and spinal cord allow for decision-making, and we shall investigate how this process works too.

    

4. Ulnar nerve practical class: We will be stimulating and recording electrical signals from our own arms. We will stimulate our ulnar nerves with small electrical shocks (generating a strange sensation, which isn’t painful!) and record the compound action potentials elicited in the muscles of our hand. We can use this simple experiment to explore properties of nerve stimulation, conduction velocity and neuromuscular transmission which we have examined in the first three lectures.

    

5. Sensory receptors: Electrical signals in nerve fibres are not normally initiated through the application of an external electrical shock, as performed in yesterday’s class! They can originate in sensory receptors, located around the body – but how? In today’s final lecture, we will see how external environmental stimuli can be translated by sensory receptors, directly or indirectly, into electrical signals. We will look at examples including the eye, the ear and some of the receptors in the skin.

Learning outcomes

As a result of the course, you will gain a greater understanding of the subject and you should be able to:

• gain a deeper understanding of the fundamental processes underlying the electrical signalling properties of excitable cells
• appreciate how we use excitable cells within the body for the purposes of sensation and communication
• appreciate how biological experimentation, combined with an understanding of some basic physics and chemistry, has shed light on the function of excitable cells, focusing on the particular contributions of Nobel Laureates who have worked in Cambridge

Required reading

There is no required reading as the course is self-contained. However, you would certainly benefit from reading the Ashcroft book in the list below, prior to attending the course.

Ashcroft, Frances, The Spark of Life: Electricity in the Human Body (London: Penguin Books, 2012)