B5 - Homeostasis & Response

Question 1

What is the definition of homeostasis?

Answer 1

It is maintaining conditions within the body at the ideal level
The regulation of the conditions inside your body (and cells) to maintain a stable environment, in response to changes in both internal and external conditions
Maintaining a constant environment in the body

Question 2

Give some examples of systems that help regulate the internal environment of an individual

Answer 2

The nervous system
The hormonal (endocrine) system

Question 3

What are the 3 main components that all automatic control systems are made from?

Answer 3

Receptor cells
Coordination centres (including bran, spine and pancreas)
Effectors

Question 4

What does a negative feedback system do?

Answer 4

It counteracts changes - for example, if the body gets too hot, it will do something to counteract that, making the body go colder until it is at normal temperature again

Question 5

Give some examples of things in the body that need to be kept at an ideal level through homeostasis and often negative feedback loops

Answer 5

Temperature
Water levels
Some other stuff
Glucose levels in the blood
Ion levels

Question 6

Give an example of something that does NOT work in a negative feedback loop, and why

Answer 6

Adrenaline - because this is only used in fight or flight situations, so constantly running on adrenaline would cause the body to die from exhaustion
Also, pretty sure that adrenaline takes away energy from digestive system, so food is not digested efficiently whilst adrenaline is present

Question 7

What happens through the negative feedback loop when levels are too low?

Answer 7

Receptors detects a stimulus or change in environment - the level is too low
The coordination centre receives and processes this information, then organises a response
The effector produces a response, which counteracts the change and restores the optimum level (the level is increased to this optimum level)

Question 8

Homeostasis cannot be controlled, therefore it is automatic. True or false?

Answer 8

True

Question 9

Talk about what happens through the negative feedback loop when levels are too high

Answer 9

Receptors detects a stimulus or a change in the environment - the level is too high
The coordination centre receives and processes the information, then organises a response
The effector produces a response which counteracts the change and restores the optimum level - the level decreases back to the ideal level

Question 10

How long will effectors work for?

Answer 10

They will carry on producing their responses for as long as they’re stimulated by the coordination centre. This might cause the opposite problem - the level may change too much from the optimum level in the opposite way. Luckily, the receptors detect if the level becomes too different again, and negative feedback starts again

Question 11

What does CNS stand for?

Answer 11

Central Nervous System - Brain, spine and nerves

Question 12

Give the flow diagram to show a reflex arc

Answer 12

Receptor
Sensory neurons
Relay neuron (in CNS)
Motor neurons
(Effector)
Response

Question 13

What are 2 ways that a reflex action is different from an action controlled by hormones?

Answer 13

1) Reflexes act much quicker, (and are almost immediate
whereas hormones travel in the blood until they are detected, which takes longer)
2) Hormones have to be released into the bloodstream to travel, whereas reflexes travel through neurons

Question 14

What are the following hormones that these glands produce, and what do they do?

a) Pituitary gland in the brain
b) Thyroid
c) Pancreas
d) Testes
e) Ovaries
f) Adrenal

Answer 14

a) Produces lots of hormones (LH, FSH being some), all about the growth of the body into adulthood
b) Thyroxine. Helps with metabolism
c) Insulin and glucagon. Controls the blood glucose
d) Testosterone. Puberty stuff
e) Oestrogen and progesterone. Menstrual cycle stuff
f) Adrenaline. For fight or flight responses & dangerous situations

Question 15

What does CNS stand for? What does it do?

Answer 15

Central Nervous System. Refers to the brain and spine chord
It coordinated the response - it receives information from the receptors and then coordinates a response, which is carried out by effectors

Question 16

What is the nervous system made from?

Answer 16

The CNS - central nervous system, meaning brain & spinal chord
Sensory neurons - Neurons that carry information as electrical impulses from receptors to the CNS (relay neurons between sensory neurons and motor neurons in the CNS)
Motor neurons - The neurons that carry electrical impulses from the CNS to effectors
Effectors - All muscles and glands which respond to nervous impulses

Question 17

What are the differences between receptors and effectors?

Answer 17

Receptors are the cells that detect stimuli. There are many different types of receptors, such as taste receptors on the tongue, sound receptors in the ear. Receptors can form part of larger, complex organs (e.g. the retina of the eye is covered in light receptor cells)

Effectors respond to nervous impulses and bring about a change. Muscles and glands are known as effectors - as they respond in different ways. Muscles contract in response to a nervous impulse, whereas glands secrete hormones

In short - receptors detect, effectors act on that detection (once it has gone through neurons and the CNS)

Question 18

Muscles and glands are types of what?

Answer 18

Effectors

Question 19

What is the nervous system’s function?

Answer 19

Means that humans can react to their surroundings and coordinate their behaviour

Question 20

How are reflexes even faster than normal responses to stimuli?

Answer 20

Because usually the neurons transmit the new information to the brain so it can decide what to do. Whilst this is extremely fast, it may not be fast enough to get you out of harms way. |So a reflex goes to the spinal cord instead, which is a shorter journey. Also, it’s why you have a reflex without thinking, as it isn’t something your brain is aware of until after it happened

Question 21

Rearrange these stages of the reflex arc:

1) When the impulses reach a synapse between the relay neuron and the motor neuron, the same thing happens - chemicals are released and cause electrical impulses to be sent along the motor neuron
2) Because you don’t have to think about the response (which takes time), it’s quicker than normal responses
3) When a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS
4) The neuron in the reflex arcs go through the cord or through an unconscious part of the brain
5) The effector then takes action, usually a muscle contracts to move a body part away from danger, but it depends on the context
6) When the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone on the other side of the synapse
7) The impulses then travel along the motor neurone to the effector (usually a muscle)

Answer 21

4) The neuron in the reflex arcs go through the cord or through an unconscious part of the brain
3) When a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS
6) When the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone on the other side of the synapse
1) When the impulses reach a synapse between the relay neuron and the motor neuron, the same thing happens - chemicals are released and cause electrical impulses to be sent along the motor neuron
7) The impulses then travel along the motor neurone to the effector (usually a muscle)
5) The effector then takes action, usually a muscle contracts to move a body part away from danger, but it depends on the context
2) Because you don’t have to think about the response (which takes time), it’s quicker than normal responses

Question 22

Where are synapses and what do they do?

Answer 22

They’re at the end of neurones, and they connect 2 neurones.

Question 23

How do synapses work?

Answer 23

AT the end of one neuron, a nerve impulse arrives. his causes chemicals to be released into the gap known as the synapse. They diffuse across to the other side (the start of the next neurone). These chemicals - once found by the receptors on the opposite side - then cause a new electrical impulse in the next neurone. SO, the electircal impulse travels

Question 24

What are reflexes?

Answer 24

Fast, automatic responses to certain stimuli that don’t involve the conscious part of the brain - they can reduce the chance of being injured, as it happens faster to get you out of harm’s way sooner

Question 25

Give an example of how reflexes help keep your eyes safe from light

Answer 25

If someone shines a bright light in your eyes (please don’t), your pupils will automatically (and unconsciously, why it is a reflex) get smaller, so that less light gets into the eye - preventing it from being damaged.
The same happens the other way. When it is dark. Your pupil will grow as there is no danger of light now, and to help you see better

Question 26

The passage of information in a reflex is known as what?

Answer 26

A reflex arc

Question 27

What is a reflex arc?

Answer 27

The passage of information in a reflex

Question 28

Give an example of a hormone that works on the reflex arc

Answer 28

Adrenaline from the adrenal gland - if you get a shock, your body releases the hormone automatically in the blood (which enhances pretty much everything in the body, makes it faster). It doesn’t wait for you to decide you’re shocked, as then the shock or danger may have already hurt you.
Adrenaline prepares you for fight or flight response

Question 29

What practical can you use to measure reaction time?

Answer 29

Where you drop a ruler, and see hpw quickly a person can catch it.
Dependant variable - the reading on the ruler where the person caught it (mm ruler best)
Independant variable - if testing the effects of caffeine, then caffeine levels in the person. If just testing results for different people, then the person catching the ruler
Control variables - the starting height of the ruler/ metre stick, the person dropping the ruler, the ruler, the same hand to catch and drop
Remember to conduct the test with each person at least 3 times, then calculate a mean. ALso, remember not to count the person down and then drop it, it must be dropped randomly and unexpectedly, then it will be a reaction and not just timing it well.

HOWEVER - reaction time can also be measured on a computer - simple computer tests exist to do this, which often give a more precise reaction time, as they remove the possibility of human error

Question 30

What does reaction time mean?

Answer 30

How quickly you respond

Question 31

How are computer reaction tests arguably better?

Answer 31

As they are more precise
As they remove the possibility of human error compared to the dropping the ruler test
It gives the results in milliseconds, far more precise to millimetres
Removes the possibility the person can predict when to respond (with the ruler test, the catcher may anticipate the drop by reading the tester’s body language

Question 32

Give the instructions for the ruler test to measure reaction time and how caffeine effects reaction time

Answer 32

1) The catcher should sit with the arm resting on the edge of the table, preventing them from moving their arm up and down during the test. Make sure they have had no caffeine recently, so can’t be under it’s effects. You need a control
2) Hold a ruler vertically between their thumb and forefinger. Make sure the 0 is level with their thumb and forefinger. Then let go without giving any warning
3) The person being tested must catch the ruler (by closing their thumb and forefinger) as fast as they can - as soon as they see it fall
4) Reaction time is measured by the number on the ruler where it’s caught. The number should be read from the top of the thumb. The closer to 0mm it is, the faster their reaction time
5) Repeat this test at least 3 times (so it is more accurate), then calculate the mean distance that the ruler fell - this is their reaction speed
6) The person being tested should then have a caffeinated drink, such as 300ml of coca-cola. After 10 minutes (so the caffeine can take effect), repeat these steps
7) You need to control any variables to make it a fair, reproducible and repeatable test. Same person to catch the ruler with & without caffeine (although, you could test it on more people later to check that the effects of caffeine are universal). Catcher always uses the same hand (dominant hand). Ruler always dropped from same height.
8) Too much caffeine can cause unpleasant side effects, so the person being tested should avoid drinking any more caffeine for the rest of the day after the experiment is completed

Overall, caffeine should improve their reaction time