Biology - Messages in the Body (AQA)
Tiny hairs on the skin can be raised and lowered by small muscles to help keep us warm.

Biology - Messages in the Body (AQA)

In GCSE Science students will look at how organisms use nerves and hormones. This is the second of five quizzes on that topic and it looks in particular at how nerves and hormones carry messages around the body.

The nervous system enables humans to react to their surroundings and coordinate their behaviour. Receptors detect stimuli outside the body and relay messages to the central nervous system and brain for processing. Certain actions are voluntary, like walking or waving your hand, and are dealt with by the brain. Others are automatic and save the body from harm e.g. pulling your hand away from fire or your pupils closing up when a light is too bright. These are called reflexes and the messages from the sensors are processed in the central nervous system without needing the brain. Other messages are automatic too, like the ones telling the heart muscles to contract and relax. These are autonomous and continue all of the time.

The body also needs to control its temperature, ion content, water content and blood sugar levels. The nervous system plays its part but most of the control is done by hormones. They have a longer lasting effect and act more widely than a nerve or group of nerves. Hormones are secreted by glands and can spread throughout the body in the bloodstream. It is therefore possible for hormones to reach every cell in the body. If a cell has the right receptor chemicals, a hormone molecule will attach itself to the cell and make the cell carry out a specific action.

For example, if the blood sugar (glucose) level is high, the pancreas has cells that secrete the hormone insulin. This mixes with the blood plasma and is distributed around the body. The target organ for insulin is the liver, where glucose is changed into glycogen which can be stored and used to replenish blood sugars when the level is low. So you can see how nerves and hormones are used to carry messages around our bodies.

The central nervous system in humans is made up from what?
Only the spinal cord
Only the brain
Both the spinal cord and the brain
The spinal chord, brain and relay neurones
When a receptor is stimulated it sends a signal along the nerve cells - neurones - to the brain which co-ordinates the response, unless it is a reflex action
What do we call the type of neurone that sends a message from the central nervous system to a gland?
The message tells the gland to secrete a hormone
In a reflex action, what do we call the type of neurone which allows the message from the receptor to go directly to the effector without needing to go to the brain first?
This makes reflex actions much faster, helping to protect the body from damage
The messages are transmitted across the gap from one nerve cell to another. Which of the following pairs of words give the name for the gap and how the messages are transferred from one nerve cell to the next?
Dendrite, chemical
Dendrite, electrical
Synapse, chemical
Synapse, electrical
There are two things that could lead you to the wrong answer here. Many students confuse dendrite and synapse. The signals travel through nerve cells as electrical impulses but between nerve cells by chemicals called neurotransmitters. Many students assume that the the messages passing through the nervous sytem are entirely electrical
Which of the following statements about the nervous system and hormones is incorrect?
When compared to control via the nervous system, hormones act faster but their effects last longer
When compared to control via the nervous system, hormones act more slowly and their effects last longer
The effectors of the nervous system are muscles or glands, the effectors for hormones are target cells, tissues and organs
The response of control by the nervous system is a muscle contraction or hormone secretion, the response to hormones is a chemical change in the body
A lot of reading for that one! The nervous system is much faster than the endocrine system (hormone system) because the messages travel through the nerves as electrical impulses
Which of the following statements about insulin is correct?
Insulin is secreted by the liver and transported to the pancreas where it changes sugar into starch
Insulin is a catalyst that destroys glucose in the blood
Insulin is a hormone that helps to regulate the water content of the blood
Insulin is secreted by the pancreas and it stimulates cells in the liver to convert glucose into glycogen
People with diabetes either don't produce insulin, don't produce enough insulin or their insulin receptors don't work, so their blood sugar levels can drop too low or go too high. Some of these people can control it by careful eating whilst others need to have insulin injections. Most insulin for diabetics to use is now made from genetically modified bacteria rather than taken from cow or pig pancreases, as it used to be
What are the missing words in the correct order from this description of a reflex action?

1. A ______ detects a stimulus.
2. A sensory neurone sends impulses to a ______ neurone.
3. A motor _______ sends impulses to an effector.
4. An effector produces a ________.
sensory, effector, relay, response
receptor, relay, neurone, response
finger, motor, sensory, receptor
receptor, neurone, response, receptor
The relay neurone bypasses the brain, ensuring that the reflex action occurs as quickly as possible
When you are too hot or too cold, the brain sends nerve messages to the skin to do several things. Which one of the following is not a response used to control body temperature?
Tiny hairs on the skin can be raised and lowered by small muscles
Blood vessels in the skin can be dilated or contracted
Glands in the skin are stimulated to release greater quantities of natural oils onto the surface of the skin
Glands in the skin are stimulated to release sweat
Raising the hairs will trap air close to the surface of the skin. Trapped air is a good insulator. Opening the blood vessels gets rid of excess heat carried by the blood, that is why you look 'flushed' during and after exercise
Why is it important to maintain an even temperature of 37oC for the human body?
It is a nice temperature to be at
It is an easy temperature to maintain
When life first started, that was the temperature of the Earth
The enzymes in the body work most efficiently at that temperature
The body can work at higher or lower temperatures but only for a while. If the temperature of the body drops to below 35oC, hypothermia sets in, when it drops below 28oC it is very serious and death can occur. A fever is when the body temperature is higher than normal, fevers of over 41.5oC can be fatal but a fever is usually a response to illness and will pass as your body recovers
The main method of controlling the amount of water in the body is via the kidneys. How does this happen?
A hormone is used to send a message to the kidney to excrete more water
Nerve impulses from the brain are used to send a message to the kidney to excrete more water
Both of the above
No message is needed, it will happen automatically
The hormone that regulates the water content of the blood is ADH. It is made in the pituitary gland and the target organ is the kidneys. A nerve impulse is used but it is between the hypothalamus and the pituitary gland which is why the second option is incorrect
Author:  Kev Woodward

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