Use of apparatus and techniques: (ii) physiological functions

The idea

Physiological functions are the normal jobs that cells, tissues, organs and organ systems carry out to keep an organism alive and functioning. Examples include gas exchange across a respiratory surface, absorption of nutrients in the gut, filtration and reabsorption in the kidney, conduction of impulses along neurones and contraction of muscle. When you investigate a physiological function practically, you link structure to the process: for instance, measuring heart or ventilation rate, or observing the effect of a variable on a living tissue. Interpret results in terms of the function being performed, not just the numbers recorded. Recognise that functions depend on transport, exchange and control, and that a change in one factor, such as temperature or substrate concentration, can alter the rate of the function.

What earns the marks

• Defines physiological function as the normal role carried out by a cell, tissue, organ or system that maintains life processes.
• Gives accurate examples such as gas exchange, absorption, filtration and reabsorption, nervous conduction or muscle contraction, correctly matched to the structure performing them.
• Links observed measurements or changes to the function being carried out, explaining the biological reason rather than only reporting data.
• Recognises that physiological functions depend on exchange, transport and control, and that changing a factor such as temperature or concentration can alter the rate of the function.

Common mistakes and how to put them right

• Learners describe anatomy only, naming structures without stating what they do.

  Put it right: State the function each structure performs and how it maintains life processes.

• Learners report measurements without interpretation.

  Put it right: Explain what the data show about the physiological function being carried out.

• Learners assume a function occurs at a constant rate regardless of conditions.

  Put it right: Recognise that factors such as temperature or substrate concentration can change the rate of the function.

• Learners use vague terms such as 'works properly'.

  Put it right: Use precise physiological vocabulary, for example gas exchange, reabsorption or conduction.

Exam tips

• Match each named structure to a specific function rather than listing organs alone.
• When interpreting data, state the trend and then explain the physiological reason for it.
• Use precise terminology such as exchange, transport, reabsorption and control to describe functions.