A.2: The human brain

Essential idea: The parts of the brain specialize in different functions.

Nature of science: 

Use models as representations of the real world—the sensory homunculus and motor homunculus are models of the relative space human body parts occupy on the somatosensory cortex and the motor cortex. (1.10)

Understandings:

• The anterior part of the neural tube expands to form the brain.

• Different parts of the brain have specific roles.

• The autonomic nervous system controls involuntary processes in the body using centres located mainly in the brain stem.

• The cerebral cortex forms a larger proportion of the brain and is more highly developed in humans than other animals.

• The human cerebral cortex has become enlarged principally by an increase in total area with extensive folding to accommodate it within the cranium.

• The cerebral hemispheres are responsible for higher order functions.

• The left cerebral hemisphere receives sensory input from sensory receptors in the right side of the body and the right side of the visual field in both eyes and vice versa for the right hemisphere.

• The left cerebral hemisphere controls muscle contraction in the right side of the body and vice versa for the right hemisphere.

• Brain metabolism requires large energy inputs.

Applications and skills:

• Application: Visual cortex, Broca’s area, nucleus accumbens as areas of the brain with specific functions.

• Application: Swallowing, breathing and heart rate as examples of activities coordinated by the medulla.

• Application: Use of the pupil reflex to evaluate brain damage.

• Application: Use of animal experiments, autopsy, lesions and fMRI to identify the role of different brain parts.

• Skill: Identification of parts of the brain in a photograph, diagram or scan of the brain.

• Skill: Analysis of correlations between body size and brain size in different animals.

Guidance:

• Image of the brain should include the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemispheres.

• Although specific functions can be attributed to certain areas, brain imagery shows that some activities are spread in many areas and that the brain can even reorganize itself following a disturbance such as a stroke.