11.9 The brain and our senses
- The order of making a response: Sense organ Stimulus Brain Muscle Response message
p.116 response muscle brain sense organ stimulus
- The functions of different parts of body in making a response: Body part Function detect stimuli in the environment sense organs nerves carry messages to brain interprets messages, gives sensations brain make a response muscles
interprets messages received Functions of the brain p.116 interprets messages received Sensory function (感覺功能) gives sensations Motor function (運動功能) decides what to do sends messages along nerves
Sensory function Motor function response muscles brain sense organ stimulus
Reaction time (反應時間) - The time taken for our body to react to p.118 - The time taken for our body to react to a stimulus. - different among individuals. Sense organ Stimulus Brain Muscle Response message
Experiment Centre 11.9 p.118 Who reacts faster?
> Taking alcohol and drugs increases it. - The following factors can affect reaction time: > Training shortens it. > Tiredness increases it. > Taking alcohol and drugs increases it. p.119
- The brain consists of three main parts. Cerebellum (小腦) Cerebrum (大腦) Medulla (延腦) Different parts of the brain do different jobs.
- Top view of the brain: > Divided into two hemispheres. > Highly folded to increase surface area for accommodating more cells.
- Longitudinal section cerebrum at the back of brain cerebellum medulla at the bottom of brain, linking to spinal cord
action controlled by thinking Function of cerebrum p.120 - related to intelligence, memory and thought. (隨意動作). - controls voluntary action action controlled by thinking E.g. talk, shake hands...
Do you know ? Function of cerebellum - controls balance. - controls muscle coordination. E.g. walk, run... Do you know ? If the cerebellum is damaged, what will be the result?
Not controlled by thinking Function of medulla (不隨意動作) - controls involuntary action Not controlled by thinking E.g. heartbeat, breathing
Do you know ? The brain is about 1/50 of the total body weight, but it uses 1/5 of the body’s energy.
Activity Corner M 1 a Are the darker lines parallel? Is the brain always correct? b Use a ruler to check you answer. What do you find?
b Use a pencil to trace its path. 2 a Is it a spiral? b Use a pencil to trace its path. What do you find?
3 a Which column of the grey bars is darker? b Hide away the black bars. Are all the grey bars in the same shade?
4 How many legs does this elephant have? Sometimes the brain interprets messages incorrectly. This results in illusions.