The Brain

1. The Brain Thalamus Cerebrum Corpus callosum Hypothalamus Pituitary gland Cerebellum Medulla

2. The Different Regions of the Brain • The medulla controls heart rate, breathing, peristalsis, and reflexes such as sneezing. • The hypothalamus controls temperature and water homeostasis. Also controlling the release of hormones by the pituitary gland. • The thalamus is a relay station, integrating sensory input and channelling it to the sensory areas of the cerebrum. • The cerebellum co-ordinates muscle movement and so controls balance, posture and movement.

3. The Cerebral Hemispheres  The upper part of the brain, the cerebrum is responsible for all voluntary activities, it is connected to the nervous system.  The cerebrum is divided down the middle by a deep cleft into two cerebral hemispheres connected by the nerve fibres of the corpus callosum  The inside contains fluid and only the outer few mm of the cerebral hemispheres contains neurones and this is called the cerebral cortex.  The cortex is highly folded providing a large surface area.

4. The Cerebral Cortex Functions of the cortex are localised into discrete areas: Sensory Areas- these receive impulses via sensory neurones from receptors that detect the stimuli reaching the body. The skin has more receptors in some parts of the body than others. Motor areas send impulses to skeletal muscles along nerve fibres passing down the brain stem and spinal cord. As with the sensory areas the part of the body is represented by an area of the motor cortex.  Association areas make decisions and send impulses through the motor areas.

5. Motor and Sensory Areas  The main motor area controls the main skeletal muscles of the body and the main sensory area receives input from the various skin receptors all over the body.  The areas are duplicated onto the two cerebral hemispheres, which control opposite sides of the body.  Therefore, those situated on the left cerebral hemisphere are linked to the right side of the body and vice versa.  The regions of the body with many sensory neurones have correspondingly large areas of the cortex linked to them. For example, the lips occupy a larger region of the sensory cortex than the shoulder, because they have more sensory neurones.

6. Association Areas Theses are involved in advanced kills such as visual recognition , language understanding, speech and memory retrieval.  The frontal lobes are particularly large in humans, they are thought to responsible for higher functions such as abstract thought, personality and emotion.  The association areas are not duplicated in the two hemispheres. The right hemisphere has association area for face recognition, spatial skills and musical sense. The left hemisphere has association areas for speech language and language mathematical logical and analytical

7. Visual Processing  The visual sensory area is at the back of the brain and receives sensory input from the optic nerve.  Neurones from the left half of the retinas of both eyes go to the visual sensory area in the left hemisphere and likewise for the right half of the retina.  Therefore the two hemispheres see slightly different images from opposite sides of the visual field, these differences help judge distance.