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The Brain

Human Biology (Year 12) - Nervous System

Ben Whitten

What is the brain?

The brain is a highly specialised and complex organ whose role in the nervous system is that of a central receiver, analyser, coordinator, storer and initiator of nerve impulses. The brain also has the unique function of memory. There are some key coomponents of the brain which you need to know, including:

  • The medulla oblongata

  • The cerebrum

  • The cerebellum

  • The hypothalamus

What is the medulla oblongata? The medulla oblongata is a continuation of the spinal cord; it joins the brain to the spinal cord. The medulla's role in the brain is to coordinate a number of different activities, however there are three which you need to have an awareness of.

  1. Cardiac centre: regulates the rate and force of heartbeat

  2. Respiratory centre: controls the rate and depth of breathing

  3. Vasomotor centre: regulates the diameter of blood vessels

What is the cerebrum? Structure The cerebrum is the largest part of the brain. It consists of an outer layer of grey matter called the cerebral cortex. The cerebral cortex is folded into patterns that greatly increase its surface area; in the way the cerebral cortex contains 70% of all of the neurons found in the CNS. Folding of the brain produces rounded ridges called convolutions (or gyri). The convolutions are separated by shallow down folds called sulci (singular sulcis), or deep down folds called fissures. The longest, deepest fissure is the longitudinal fissure that separate the brain into the left and right cerebral hemispheres. Function The cerebral cortex is involved in higher order functions such as thinking, reasoning, learning, memory, intelligence and a sense of responsibility. It is also concerned with the perception of the senses and the initiation of control over voluntary muscle contraction. The cerebral cortex can be divided into three main functional areas.

  1. Sensory areas: interprets impulses from receptors

  2. Motor areas: controls muscular movements

  3. Association areas: interprets information from the senses to initiate a response/make it useful

What is the cerebellum? The cerebellum is the second largest part of the brain, lying at the rear part of the brain. It consists of an outer layer of grey matter and an inner layer of white matter. The cerebellum has control over posture, balance, and fine coordination of voluntary muscle movements. To carry out these functions, the cerebellum receives information from the inner ear (for posture and balance) and from stretch receptors in the skeletal muscle. Without the cerebellum, we could still move but the movements would be jerky and uncontrolled. What is the hypothalamus? The hypothalamus lies in the middle of the brain and cannot be seen from the outside. The hypothalamus controls many body acitivites, mostly concerned by homeostasis; regulation of body temperature, metabolism, thirst and response to fear and anger (autonomic nervous system). The hypothalamus also has a role in the coordination of parts of the endocrine system acting through the pituitary gland. It regulates metabolism, growth, reproduction and responses to stress.

What are the other components of the brain?

  • Pons: Coordinates and transmits information between the cerebral cortex, cerebellum and spinal cord

  • Pituitary gland: Master gland, controls other endocrine glands by producing hormones

  • Corpus callosum: Band of nerve fibres that lies underneath the cerebrum, connecting the left and right hemispheres

  • Spinal cord: Provides a pathway for communication between muscles, glands and the brain; and integration of autonomic, protective reflexes

  • Thalamus: Acts as a relay station; all sensory information passes through the thalamus before going to the cerebral cortex (cerebellum)

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