International A Level Biology / Coordination in animals and plants
The regions of the human brain revision notes
Edexcel International A Level Biology (YBI11), chapter 24: Coordination in animals and plants, specification point 8.14, 8.10. Free lesson.
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The nervous system is divided into the central nervous system and the peripheral nervous system. Knowing where the brain’s main regions are and what each controls helps you explain how the body responds and stays regulated.
How the nervous system is divided
The central nervous system (CNS) is the brain and spinal cord. The peripheral nervous system (PNS) is every neurone outside them. The CNS processes information and coordinates responses, while the PNS carries impulses between the CNS and the rest of the body. The CNS contains mostly relay neurones, which pass impulses between neurones. The PNS contains sensory neurones and motor neurones. Sensory neurones carry impulses from receptors into the CNS. Motor neurones carry impulses from the CNS to effectors, which are muscles and glands.
Where the CNS and PNS are found
The brain lies inside the skull, and the spinal cord runs down inside the backbone. Nerves reach out from the CNS to the rest of the body and form the PNS. A receptor starts a sensory impulse, while an effector responds to a motor impulse. For example, receptors in the skin of a fingertip send impulses towards the CNS. A leg muscle is an effector. It responds to impulses carried away from the CNS by motor neurones.
How to find five brain regions
On a section through the brain, the front is on the left. Use the pons as a landmark, then find the medulla oblongata below it at the bottom of the brain stem, where the spinal cord begins. The cerebral hemispheres are the large, folded upper part. The left and right halves together make the cerebrum. The hypothalamus is near the middle, just above the pituitary gland. The pituitary gland hangs below the hypothalamus on a short stalk. The cerebellum is at the back, underneath the cerebral hemispheres. It is folded more finely. The pons is a bulge at the front of the…
What each brain region controls
Learn each region’s location alongside its function. This helps you choose the correct region when explaining a response or body process. The cerebral hemispheres control conscious thought, including memory, language, reasoning and deciding to move. Sensory areas receive impulses from receptors; motor areas send impulses to skeletal muscles. The hypothalamus helps keep conditions steady. It contains the thermoregulatory centre for body temperature and osmoreceptors for water balance. It makes ADH and controls the pituitary gland. The pituitary gland secretes hormones, many of which…
Keep the medulla and cerebellum separate
The medulla and cerebellum are close together, so their functions are easy to swap. The medulla controls automatic functions such as heart rate and ventilation; the cerebellum coordinates movement and balance. If the hypothalamus is damaged, body temperature may not be kept steady because its thermoregulatory centre is there. Water balance may also be upset. Less ADH means less water is reabsorbed, so a large volume of dilute urine is produced.