How do the nervous and endocrine systems control and coordinate the body?
The nervous system with the CNS and the three types of neuron and the reflex arc, the endocrine system using hormones and target tissues with receptors, and the control of blood glucose by insulin and glucagon from the pancreas.
An SQA National 5 Biology answer on control and communication, covering the nervous system with the CNS and the three types of neuron and the reflex arc, the endocrine system using hormones and target tissues, and the control of blood glucose by insulin and glucagon from the pancreas.
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What this dot point is asking
The SQA wants you to describe how the body is controlled by two systems: the fast nervous system (the CNS, the three types of neuron, and the reflex arc) and the slower endocrine system (hormones, target tissues and receptors). You also need to explain how blood glucose is kept steady by insulin and glucagon from the pancreas.
The nervous system
There are three types of neuron, each with a clear job:
A motor neuron has a myelin sheath around its axon, which increases the speed at which the impulse travels.
The reflex arc
A reflex is a rapid, automatic response that protects the body from harm, such as pulling your hand off a hot surface before you have even thought about it.
The endocrine system
The second control system is slower but longer-lasting. It uses chemicals instead of impulses.
Because only target tissues have the matching receptors, a hormone travelling all round the body in the blood still affects only the right organs.
Controlling blood glucose
Blood glucose must be kept within a narrow range. The pancreas monitors it and releases two hormones, working in opposite directions.
The liver is the store, holding glucose as glycogen and releasing it again when needed.
Examples in context
Example 1. The knee-jerk reflex. Tapping the tendon below the knee stretches a receptor, which sends an impulse along a sensory neuron to the spinal cord, through an interneuron to a motor neuron, and out to the thigh muscle (the effector), which contracts and kicks the lower leg forward. The response is automatic, showing the reflex arc in action.
Example 2. Type 1 diabetes. In type 1 diabetes the pancreas cannot make insulin, so after a meal the blood glucose stays dangerously high because the liver is not told to store it as glycogen. Treatment is injected insulin (made by genetic engineering), which does the job the missing hormone would do.
Try this
Q1. Name the neuron that carries impulses from the CNS to an effector. [1 mark]
- Cue. The motor neuron.
Q2. State which hormone the pancreas releases when blood glucose is too high. [1 mark]
- Cue. Insulin.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA N5 style4 marksDescribe the path of a nerve impulse through a reflex arc when a hand touches a hot object.Show worked answer →
A 4-mark answer should name the parts in order and link them to the rapid response.
A receptor in the skin detects the heat and starts an impulse.
The impulse passes along a sensory neuron to the central nervous system (the spinal cord).
Within the CNS, an interneuron (relay neuron) passes the impulse to a motor neuron.
The motor neuron carries the impulse to an effector, a muscle, which contracts to pull the hand away.
Markers reward the correct order: receptor, sensory neuron, interneuron, motor neuron, effector. The reflex is rapid and automatic, protecting the body from harm.
SQA N5 style4 marksExplain how the body lowers blood glucose when it rises after a meal.Show worked answer →
A 4-mark answer should trace detection, hormone, target and effect.
The pancreas detects that blood glucose has risen too high.
The pancreas releases the hormone insulin into the blood.
Insulin travels to the liver, its target tissue, which has receptors for it.
The liver responds by converting excess glucose into glycogen for storage, which lowers the blood glucose back to normal.
Markers reward (1) the pancreas detecting high glucose, (2) releasing insulin, (3) insulin acting on the liver, and (4) glucose converted to glycogen, lowering blood glucose.
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Sources & how we know this
- SQA National 5 Biology Course Specification — SQA (2019)