We readily associate the mind and the brain with intelligence because we use our brains to learn new facts and to draw conclusions. However, the brain is much more than a tool for thinking – it is the command center of the body, and in this role, it strongly influences our health and well-being.
The brain sits at the center of the labyrinthine empire of the senses, keeping us in touch with the outside world through sight, sound, smell, and touch. At the same time, it constantly monitors the environment inside the body, sending instructions through the nervous system to keep body systems working properly. Every experience we have – from hunger to heartbreak, from pleasure to pain, from excitement to illness – is mediated through the brain and its nervous system. This chapter explores the brain-body connections that make this possible, revealing the routes through which the brain exerts its control over the body.
Inside The Control Centre
The brain is the control center of the nervous system, a network that stretches to the tips of the toes and into every organ of the body. This system allows continuous, two-way communication between brain and body: anything that occurs in one inevitably affects the other.
The brain exists primarily to support the body, just like any other organ, such as the liver or the heart. This primary function is often obscured, however, by the brain’s dazzling capacity to generate something that at first glance seems to be quite removed from the body – the conscious mind. Yet even consciousness depends on and serves the body. Sights, sounds, sensations, thoughts, and emotions are the consciously experienced elements of a vast and mainly unconscious system that keeps the body functioning and enables us to adapt to our environment. While each part of the brain has a specific function, none works alone.
Divisions of the brain
The structure of the brain reflects ·its evolution: The oldest part – the limbic system – lies deep inside the brain, while the most recently evolved areas form the grey, wrinkled surface known as the cerebral cortex, the outer layer of the cerebrum. The cerebral cortex in each hemisphere is made up of four lobes, with each lobe divided into hundreds of smaller areas. Some of these areas receive information from the sense organs and transform it into conscious perceptions. The body is continuously monitored by several cortical areas, which receive and convey information via the spinal cord and peripheral nerves. The somatosensory cortex, for example, functions as a ‘body map ‘ that corresponds to various parts of the body. Other cortical areas generate thoughts and language and turn the bodily changes that underlie emotion into feelings.
The limbic system lies deep within the brain. This primitive part of the brain contains several distinct structures, including the thalamus, the hippocampus, the amygdala, and the hypothalamus. These structures ensure that we react appropriately to any stimuli, such as thirst or a fast-approaching object, that we need to avoid. The limbic system also governs activities that are concerned with self-preservation, such as responding to danger and the expression of emotion.
Beneath the limbic system in the brain stem, where the areas that regulate basic bodily functions, such as heart rate and breathing, are located, parts of the brain stem also stimulate emotion, attention, and consciousness. Attached to the brain stem is the cerebellum – a miniature version of the whole brain – which mainly controls movement and coordination.
A look inside the brain
The Cerebrum
- Anterior Cingulate Interior: A switches attention either outwards to what is happening outside the body or inwards to thoughts and feelings.
- Prefrontal Cortex: This supports higher human faculties such as planning, creativity, and the inhibition of urges.
- Motor Cortex: Movement instructions are sent from here to every part of the body
- Somatosensory Cortex: Nerves from every part of the body converge here, bringing sensory information. Each part of the body has its own ‘slice’ of this cortical area.
- Corpus Callosum: A band of tissue that links the two cerebral hemispheres.
The Limbic System
- Amygdala: Tastes incoming sensory information for threatening content, sending ‘fight or flight’ messages to the body and alerting areas of the cortex connected with fear, anger, and sadness.
- Hypothalamus: Registers and controls temperature, libido, hunger, and aggression via endocrine (hormone-producing) glands throughout the body.
- Thalamus: Relays sensory information to the appropriate part of the cortex. It also directs attention and modulates levels of awareness.
- Hippocampus: Lays down memories. It stores personal and important memories and shunts others to permanent storage places in the cortex.
The Brain Stem and Cerebellum
- Pons: Links the medulla with the thalamus. Nerve tracts linking the spinal cord and the cerebral cortex pass through here.
- Medulla: Extension of the spinal cord, forming the lowest part of the brain stem. Regulates heart beat rate, breathing, and blood pressure.
- Cerebellum: Literally the ‘little brain.’ Controls physical coordination, balance, and eye movements.
