Practise Edexcel IGCSE Biology practical contexts by choosing distance and time measurements needed to calculate nerve impulse speed.
A teacher uses this method to estimate the speed of a nerve impulse.
- students stand in a circle and hold hands
- student A in the circle starts a timer and at the same time squeezes the hand of student B on his left
- when student B feels his hand being squeezed, he immediately squeezes the hand of the student on his left
- this process continues around the circle of students until student A feels his hand being squeezed and he stops the timer
Explain what other measurements the teacher would need to make in order to calculate the speed of a nerve impulse.
An explanation that makes reference to two of the following points
- measure the distance (from hand to spinal cord and or brain to other hand)
- for each student / all students in ring
- measure time taken (for student A to feel hand being squeezed / eq)
- divide distance by time
ignore count number of students
allow 'how long it took'
exp