Control and Coordination · Lesson 4 of 11
Human Brain
“Meet the body's control room, balance coach and automatic maintenance crew.”
- Differentiate the central and peripheral nervous systems. - Explain how the brain receives, integrates and sends information. - Describe the functions of the fore-brain, mid-brain and hind-brain. - Relate the medulla to involuntary actions. - Relate the cerebellum to posture, balance and precision. - Classify familiar actions as voluntary, involuntary or reflex.
Writing a sentence seems simple, yet it requires the brain to recall words, decide their order, guide the eyes, control the small muscles of the fingers and adjust pressure on the page. At the same time, breathing and heartbeat continue without deliberate attention. The human brain coordinates these very different activities through specialised regions working together.
Central Nervous System
The brain and spinal cord together, responsible for receiving information, integrating it and coordinating responses.
The spinal cord carries information between much of the body and the brain and also participates in reflex actions. The brain is the principal coordinating centre. It receives sensory information, combines information from different sources, compares it with stored experience and produces instructions for appropriate responses.
Peripheral Nervous System
The nerves outside the brain and spinal cord that connect the central nervous system with receptors, muscles, glands and other body structures.
Cranial nerves arise from the brain, while spinal nerves arise from the spinal cord. Together these pathways carry sensory information inward and motor instructions outward. The central and peripheral systems are therefore not competing systems: the peripheral nerves provide communication routes, while the central system performs major integration and coordination.
| System | Main structures | Main role |
|---|---|---|
| Central nervous system | Brain and spinal cord | Integration, decision-making and coordination |
| Peripheral nervous system | Cranial and spinal nerves | Communication between the central system and the rest of the body |
Voluntary Actions
Writing, talking, moving a chair and clapping after a performance are voluntary actions because they are initiated after deciding what to do. The brain prepares motor instructions and sends them through nerves to voluntary muscles. Sensory feedback then helps correct the action. For example, vision and touch help the brain adjust the grip and movement needed to pick up a pencil.
Fore-brain
The fore-brain is the main thinking region. Different areas receive impulses related to sight, hearing, smell and other sensations. Association areas combine these signals with one another and with information already stored in memory. This produces an interpretation rather than a collection of unrelated sensations. After a decision is made, motor areas send instructions that control voluntary muscles.
The fore-brain also contains centres associated with internal sensations. Feeling full after eating is not simply seeing food disappear from a plate; internal information is processed by a centre associated with hunger and satiety. The hypothalamus, located at the base of the fore-brain, is important in such internal regulation and in controlling the release of several hormones.
Mid-brain And Hind-brain
Many actions occur without conscious planning. The mid-brain and hind-brain contain centres involved in involuntary control and automatic coordination. These regions help the body continue essential activities while conscious attention is directed elsewhere.
Medulla
The medulla, part of the hind-brain, regulates involuntary actions including blood pressure, salivation and vomiting. These activities must be adjusted continuously, yet it would be inefficient and dangerous to depend on remembering to perform them.
Cerebellum
The cerebellum makes voluntary movements precise and helps maintain posture and balance. Walking in a straight line, riding a bicycle and picking up a pencil all require continuous comparison between intended and actual movement. The cerebellum helps adjust the timing and strength of muscle contractions so the movement remains smooth.
Problem
Classify writing, heartbeat and hand withdrawal from heat.
- 1.Writing is voluntary because it begins with conscious choice.
- 2.Heartbeat is involuntary because it continues without conscious instruction.
- 3.Withdrawal from heat is a reflex because it is a rapid automatic response to a specific stimulus.
Problem
A person can think clearly but has difficulty maintaining balance and performing precise hand movements. Which brain region is most likely affected?
- 1.Clear thinking suggests major fore-brain functions remain active.
- 2.Balance and precision are characteristic functions of the cerebellum.
- 3.The pattern therefore points most strongly to impaired cerebellar function.
Problem
A person sees a ball and decides to catch it. Trace the major information flow.
- 1.Visual receptors generate sensory information.
- 2.Peripheral nerves carry signals towards the central nervous system.
- 3.The fore-brain interprets the moving object and decides to act.
- 4.Motor areas send instructions through peripheral motor nerves.
- 5.Arm and hand muscles contract, while the cerebellum helps refine timing, posture and precision.
The brain does not perform only thinking. Different parts help regulate heartbeat, salivation, vomiting, posture, balance and precise movement. Likewise, the spinal cord is not merely a cable; it also forms important reflex connections.
Quiz
What constitutes the central nervous system?
Which brain region is the main thinking part?
Which structure is especially important for balance and precision?
Which action is controlled by the medulla?
What is the main role of peripheral nerves?
Practice Problems
- Differentiate the central and peripheral nervous systems. Model answer: The central system consists of the brain and spinal cord and performs integration; the peripheral system consists of nerves that carry information between the central system and the rest of the body.
- Explain how the fore-brain turns sensation into action. Model answer: Sensory areas receive impulses, association areas interpret them with stored information, a decision is made, and motor areas send instructions to voluntary muscles.
- Why can a person breathe while concentrating on reading? Model answer: Breathing is largely regulated by involuntary control centres, so it continues without constant conscious attention.
- A cyclist can move the legs but repeatedly loses balance. Identify the likely coordinating region involved. Model answer: The cerebellum is strongly implicated because it maintains balance and refines voluntary movement.
- Explain why damage to a peripheral motor nerve can prevent movement even if the brain decides to move. Model answer: The decision is produced centrally, but the motor instruction must travel through the peripheral nerve. Damage interrupts communication with the muscle.
Key Takeaways
• The brain and spinal cord form the central nervous system. • Cranial and spinal nerves form communication pathways of the peripheral nervous system. • The fore-brain interprets sensations, uses memory, makes decisions and directs voluntary movement. • The medulla helps control involuntary activities such as blood pressure, salivation and vomiting. • The cerebellum maintains posture and balance and improves the precision of voluntary actions. • Voluntary, involuntary and reflex actions involve different patterns of control but all depend on coordination.