Coordination and Response in Humans
The body coordinates its actions through two systems working side by side: the nervous system, which sends fast electrical impulses along neurones to produce an immediate, short-lived response, and the endocrine system, which releases chemical hormones into the blood to produce a slower, longer-lasting and often more widespread response. This chapter covers the structure of neurones, how information crosses the synapse, the difference between voluntary and involuntary actions, the main hormones and the glands that release them, and what happens when either system malfunctions.
The reflex arc and the comparison between nervous and hormonal coordination are two of the most frequently examined ideas in this chapter, often appearing as a labelling diagram, a comparison table, or a short-answer question asking a student to trace the pathway of an impulse from stimulus to response. Getting the order of the five parts of a reflex arc exactly right, in the correct direction, is one of the easiest ways to secure full marks on this topic.
Both coordination systems can also malfunction, and this chapter includes two health issues as examples: a nervous system disorder such as stroke or Parkinson's disease, in which neurones in the brain are damaged or lost, and an endocrine disorder such as diabetes mellitus, in which the body produces too little insulin or its cells stop responding properly to the insulin available, causing blood glucose levels to rise dangerously high.
Learning the healthy pathway thoroughly before studying the disorder makes the disorder far easier to explain, because most exam answers on a health issue simply ask which specific part of the normal system has stopped working correctly and what effect that has on the body's ability to coordinate and respond.
One-hour paid trial · Same-day reply
Content standards in this chapter
- 12.1 Coordination and Response: Nervous and Endocrine Systems
- 12.2 The Human Nervous System
- 12.3 Neurones and the Synapse
- 12.4 Voluntary and Involuntary Actions
- 12.5 Health Issues Related to the Nervous System
- 12.6 Endocrine System
- 12.7 Health Issues Related to Endocrine System
Key concepts
- Nervous system
- The nervous system is made up of the central nervous system, the brain and spinal cord, where most information is processed and decisions are made, and the peripheral nervous system, the network of nerves that carries electrical impulses between the central nervous system and every receptor and effector in the body.
- Neurones
- Sensory neurones carry impulses from a receptor towards the central nervous system, motor neurones carry impulses away from the central nervous system to an effector such as a muscle or gland, and relay neurones inside the brain or spinal cord connect the two, allowing impulses to be processed or redirected.
- Synapse
- A synapse is a tiny gap between the end of one neurone and the start of the next. When an impulse arrives, it triggers the release of a chemical neurotransmitter that diffuses across the gap and binds to receptors on the next neurone, generating a new impulse and ensuring signals travel in one direction only.
- Reflex arc
- A reflex arc is a fast, automatic, involuntary pathway that does not require conscious thought: a stimulus is detected by a receptor, carried by a sensory neurone to a relay neurone in the spinal cord, passed to a motor neurone, and finally reaches an effector, which responds within a fraction of a second.
- Voluntary vs involuntary actions
- A voluntary action, such as picking up a pen, is consciously decided and controlled by the brain, involves the cerebrum, and can be started, changed or stopped at will. An involuntary action, such as a reflex or the beating of the heart, happens automatically without conscious control and usually protects the body or maintains an internal process.
- Endocrine system
- The endocrine system is a collection of glands that release hormones directly into the bloodstream rather than through a duct. Each hormone travels throughout the body but only affects target cells that carry the matching receptor, producing effects that develop more slowly than a nerve impulse but often last for a much longer time.
- Main hormones and glands
- Four glands and their hormones are frequently examined: the pituitary gland releases growth hormone controlling body growth, the thyroid gland releases thyroxine controlling metabolic rate, the pancreas releases insulin and glucagon controlling blood glucose level, and the adrenal glands release adrenaline that prepares the body for a stressful or dangerous situation.
- Negative feedback and homeostasis
- Hormone levels are usually regulated by negative feedback: when a condition such as blood glucose level rises or falls away from normal, a gland releases a hormone that pushes it back towards normal, and once normal is restored the gland reduces hormone release again. This feedback loop is central to how the endocrine system maintains a stable internal environment.
- Health issues of the nervous system
- Damage to the nervous system disrupts coordination: a stroke occurs when blood supply to part of the brain is interrupted, killing the neurones in that region and impairing the function they controlled, while Parkinson's disease develops when neurones that produce a chemical needed for smooth movement gradually die, causing tremors and slow, stiff movement.
- Health issues of the endocrine system
- Diabetes mellitus develops when the body produces too little insulin or when body cells stop responding normally to the insulin that is present, so glucose is not taken up from the blood into cells efficiently and blood glucose level rises above the normal range, which can damage blood vessels and organs over time.
How this chapter is examined
SPM Biology is assessed over three papers. Paper 1 has 40 objective questions (40 marks) in 1 hour 15 minutes; Paper 2 carries 100 marks across Sections A, B and C in 2 hours 30 minutes; Paper 3 is the practical, testing science process skills. Content from this chapter can appear in any of them, so lessons drill recall for Paper 1 and structured answers for Paper 2.
Common exam angles
- Tracing the reflex arc from stimulus to response, naming each of the five parts in the correct order.
- Comparing nervous and hormonal coordination in a table, covering speed, duration, and how the signal travels.
- Matching a hormone to its gland and effect, including at least one example of negative feedback.
- Explaining how a hormone disorder such as diabetes arises from too little insulin or reduced sensitivity to insulin.
- Explaining how a nervous system disorder such as stroke or Parkinson's disease disrupts a normal action.
- Interpreting or labelling a diagram of a neurone, a synapse, or the reflex arc.
Common mistakes
What students write: Saying an impulse crosses the synapse electrically.
What earns the mark: Across a synapse the impulse is carried by a chemical neurotransmitter released from one neurone and detected by the next, not directly by electricity, which is why the impulse can only travel in one direction across it.
What students write: Writing that reflexes are controlled by conscious thought.
What earns the mark: Reflexes are automatic and bypass the need for the brain to decide, using the spinal cord as the processing centre instead, so they protect the body far faster than a conscious response could.
What students write: Confusing sensory and motor neurones.
What earns the mark: Sensory neurones carry impulses towards the central nervous system from a receptor; motor neurones carry impulses away from the central nervous system to an effector, and reversing this direction is a very common exam slip.
What students write: Saying hormones give fast, short responses.
What earns the mark: Hormones give slower, longer-lasting and often more widespread responses because they travel in the blood to reach cells all over the body; nerves give fast, short and precisely targeted responses instead.
What students write: Saying hormones and nerve impulses work by the same mechanism.
What earns the mark: Nerve impulses travel electrically along a fixed pathway to one specific effector, while hormones are chemical messengers carried non-specifically in the blood and can only affect cells that have the matching receptor.
What students write: Believing insulin and glucagon do the same job in the body.
What earns the mark: Insulin and glucagon are antagonistic hormones: insulin lowers blood glucose level by encouraging cells to take up glucose, while glucagon raises blood glucose level by encouraging the liver to release stored glucose.
What students write: Assuming the nervous and endocrine systems work completely independently of each other.
What earns the mark: The two systems interact closely, for example, part of the brain controls the release of growth hormone and other hormones from the pituitary gland, linking nervous and hormonal coordination together.
What students write: Saying diabetes means a person's pancreas has stopped working entirely.
What earns the mark: Diabetes occurs when the body produces too little insulin or its cells respond poorly to it, not necessarily because the pancreas has stopped functioning completely.
Study this chapter
Processes in this chapter
Structures in this chapter
Frequently asked questions
What is a reflex arc?
How is nervous coordination different from hormonal coordination?
What happens at a synapse?
What is diabetes and how does it connect to the endocrine system?
How are the nervous system and the endocrine system connected?
Source:SRC-DSKP-EN, SRC-FORMAT
Related
One-hour paid trial · Same-day reply