Nervous and hormonal control (Edexcel Int. A-level Biology)

This lesson describes how the nervous system allows effectors to respond to stimuli and also describes hormonal control in animals. The PowerPoint and accompanying resources have been primarily designed to cover points 8.2 & 8.13 of the Edexcel International A-level Biology specification but it can also be used as a revision lesson as there are numerous prior knowledge checks of muscle contraction, protein structure and the control of gene expression.

The lesson begins by challenging the students to recall that a control system contains sensory receptors, a coordination centre and effectors. Sensory receptors are covered in detail later in the topic when some key examples are considered as well as those in the retina, but time is taken now to describe how these structures act like transducers, converting one form of energy into electrical energy and the Pacinian corpuscle is used as an example. The students will learn that the communication between the receptors and the coordination centre and the effectors is by cell signalling and that the effectors can be muscles which contract or glands that release chemicals. The next part of the lesson looks at the differing responses from the nervous and hormonal systems and discusses how this can be governed by the need for a rapid response or more of a long term effect. In terms of nervous control, the students are challenged on their recall of the sliding filament theory of muscle contraction as covered in topic 7. Moving forwards, the students will learn that hormones can be either peptide or steroid hormones and their action at a target cell differs based on their form. Students are tested on their knowledge of protein structure by a series of exam-style questions on insulin and glucagon. They are reminded that steroid hormones can pass directly through the cell membrane and their knowledge of the control of gene expression by transcription factors is tested through a task involving oestrogen and the ER receptor. The lesson concludes by reminding students that the control of heart rate, as covered in topic 7, is a coordinated response that involves both nervous and hormonal control.