Chapter 14 - Coordination and response

Question 1

How are electrical impulses sent?

Answer 1

Electrical impulses are sent as nerve impulses and travel along neurones. A bundle of neurones is known as a nerve.

Question 2

What nervous systems are in the human body?

Answer 2

The human nervous system consists of the central nervous system (CNS) which is the brain and the spinal cord and the peripheral nervous system (PNS) which is all the nerves in the body.

Question 3

What do nerves allow humans to do?

Answer 3

It allows us to make sense of our surroundings and respond to them, also coordinating and regulating body functions.

Question 4

What are sensory neurones?

Answer 4

Sensory neurones carry impulses from sense organs to the CNS (brain or spinal cord). They are long and have a cell body branching off the middle of the axon.

Question 5

What are relay neurones?

Answer 5

Relay neurones are found inside the CNS and connect sensory and motor neurons. They are short and have a cell body at one end with many dendrites branching off it.

Question 6

What are motor neurones?

Answer 6

Motor neurones carry impulses from the CNS to effectors (muscles or glands). They are long and have a large cell body at one end with long dendrites branching off it.

Question 7

How are neurones adapted for transferring impulses?

Answer 7

Neurons have a long fibre (axon) which means less time is wasted transferring the impulse from one cell to another. The axon is insulated with a fatty sheath with small, uninsulated sections along it called nodes. This means that the electrical impulse does not travel down the whole axon but jumps from one node to the next. They cell body contains many extensions called dendrites which means they can connect to many other neutrons and receive impulses from them, forming a network for easy communication.

Question 8

What is a voluntary response?

Answer 8

A voluntary response is one where you make a conscious decision to carry out a particular action, therefore it starts with your brain.

Question 9

What is an involuntary response?

Answer 9

An involuntary (reflex) response does not involve the brain as the coordinator the reactions and you are not aware you have completed it until after you have carried it out. Involuntary actions are usually ones which are essential to basic survival and are rapid, whereas voluntary responses often take longer as we consider what the consequences might be before doing it.

Question 10

What is a reflex action?

Answer 10

A reflex action is when you are automatically and rapidly integrating and coordinating stimuli with the responses of effectors.

Question 11

What is the process of a reflex action?

Answer 11

1. The pin (the stimulus) is detected by a pain/pressure/touch receptor in the skin
2. Sensory neurone sends electrical impulses to the spinal cord (the coordinator)
3. Electrical impulse is passed on to relay neurone in the spinal cord
4. Relay neurone connects to motor neurone and passes the impulse on
5. Motor neurone carries impulse to a muscle in the leg (the effector)
6. The muscle will contract and pull the foot up and away from the sharp object (the response)

Question 12

What is a synapse?

Answer 12

A synapse is a junction between two neurones. They ensure that the impulses travel in one direction only.

Question 13

What is the process of the synapse?

Answer 13

1. The electrical impulse travels along the first axon
2. This triggers the nerve-ending of the presynaptic neurone to release chemical messengers called neurotransmitters from vesicles which fuse with the presynaptic membrane
3. The neurotransmitters diffuse across the synaptic gap (or cleft) and bind with receptor molecules on the membrane of the second neurone (known as the postsynaptic membrane)
4. This stimulates the second neurone to generate an electrical impulse that travels down the second axon
5. The neurotransmitters are then destroyed to prevent continued stimulation of the second neurone which would cause repeated impulses to be sent
6. Synapses ensure that impulses only travel in one direction, avoiding confusion within the nervous system if impulses were travelling in both directions

Question 14

How can drugs effect synapses?

Answer 14

As this is the only part of the nervous system where messages are chemical as opposed to electrical, it is the only place where drugs can act to affect the nervous system.

Question 15

What are sense organs?

Answer 15

Sense organs are a group of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals.

Question 16

What are the five sense organs sensitive to and what is their sense?

Answer 16

Question 17

How do receptor cells trigger an electrical impulse?

Answer 17

Once the receptor cell in the sense organ has been stimulated it generates an electrical impulse, this is passed on to a sensory neurone which carries the impulse to the central nervous system. Here a response will be decided on and the impulse will be passed to a motor neurone via a relay neurone. The motor neurone carries the impulse to the effector which carries out the response.

Question 18

What is the eye sensitive to?

Answer 18

The eye is a sense organ containing receptor cells that are sensitive to light.

Question 19

What is the function of the cornea?

Answer 19

Transparent covering at the front of the eye that refracts light.

Question 20

What is the function of the iris?

Answer 20

Muscle that controls how much light enters the pupil.

Question 21

What is the function of the lens?

Answer 21

Transparent disc that changes the shape to focus light onto the retina.

Question 22

What is the function of the retina?

Answer 22

Layer of light receptor cells that detect light intensity and colour.

Question 23

What is the function of the optic nerve?

Answer 23

Sensory neuron that carries electrical impulses from the eye to the brain.

Question 24

Diagram of the eye

Answer 24

Question 25

What is the pupil reflex?

Answer 25

The pupil reflex is an example of a reflex action. Its role is to control the light that enters the eye by altering the pupil diameter.

Question 26

How does the eye change in bright light?

Answer 26

In bright light, the pupil constricts (gets smaller) in order to prevent too much light entering the eye and damaging the retina. The radial muscles relax and the circular muscles contract.

Question 26

How does the eye change in dim light?

Answer 26

In dim light, the pupil dilates (gets bigger) in order to allow as much light into the eye as possible. The radial muscles contact, and the circular muscles relax.

Question 27

What is accommodation?

Answer 27

Accommodation is the term used to describe the way in which the eye focuses on near or distant objects.

Question 28

How does an object being up close effect the eye?

Answer 28

When an object is up close, the ciliary muscles contract and the suspensory ligaments loosen, which makes the lens more rounded causing more light to refract.

Question 29

How does an object being far away affect the eye?

Answer 29

When an object is far away, the ciliary muscles relax, and the suspensory ligaments tighten which causes the lens to become thinner and refracts less light.

Question 30

What are rod cells?

Answer 30

Rod cells can detect light at low levels, so play an important role in night vision. They are found all over the retina except for the blind spot.

Question 31

What are cone cells?

Answer 31

Three different types of cones can detect light at three different wavelengths, enabling colour vision. They are concentrated in the fovea.

Question 32

What is a hormone?

Answer 32

A hormone is a chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs. Adrenal glands produce adrenaline, pancreas produces insulin, testes produce testosterone and ovaries produce oestrogen.

Question 33

Why do hormonal glands have a good blood supply?

Answer 33

These glands have a good blood supply as when they make hormones, they need to get them into the bloodstream as son as possible so they can travel around the body to the target organs to bring about the response.

Question 34

What is glucagon?

Answer 34

Glucagon is secreted in the pancreas. It is produced when blood glucose falls and stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the blood.

Question 35

What is adrenaline?

Answer 35

Adrenaline is secreted in fight or flight situations, and it increases breathing rate and heart rate so glucose and oxygen can be delivered quickly to muscle cells and carbon dioxide can be taken away, diverts blood flow towards muscles to ensure the reactants of respiration are available as soon as possible, increases blood glucose concentration for increased respiration in muscle cells and increases pupil diameter to allow as much light to reach the retina so more information can be sent to the brain.

Question 36

What is the difference between the nervous system and the endocrine system?

Answer 36

Question 37

What is homeostasis?

Answer 37

Homeostasis is the maintenance of a constant internal environment. The human body works best at around 37oC. If body temperature increases over this temperature, enzymes will denature and become less effective at catalysing reactions such as respiration.

Question 38

What is the function of insulin?

Answer 38

Insulin is secreted into the blood at times when blood glucose levels are high and decreases blood glucose concentration.

Question 39

What is negative feedback?

Answer 39

Negative feedback occurs when conditions change from the ideal or set point and returns condition to this set point. If the level of something rises, control systems and switched on to reduce it again but it something falls, control systems are switched to raise it again. Negative feedback mechanisms are usually a continuous cycle of bringing levels down and then bringing them back up so that overall, they stay withing a narrow range of what is considered normal.

Question 40

What controls blood glucose levels?

Answer 40

Blood glucose levels are controlled by the negative feedback mechanism involving insulin and glucagon, both hormones are made in the pancreas.

Question 41

When is insulin produced?

Answer 41

Insulin is produced when blood glucose rises and stimulates liver and muscles cells to convert excess glucose into glycogen to be stored to decrease blood glucose levels.

Question 42

When is glucagon produced?

Answer 42

Glucagon is produced when blood glucose levels fall and stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the blood.

Question 43

Chart showing when insulin and glucagon are produced to regulate glucose blood level

Answer 43

Question 44

What is type 1 diabetes?

Answer 44

Type 1 diabetes is a condition where the blood glucose levels are not able to be regulated as the insulin secreting cells in the pancreas are not able to produce insulin, leading to very high blood glucose levels. It can be treated by injecting insulin.

Question 45

How is temperature regulated in the human body?

Answer 45

Regulation is controlled by the brain which contains receptors sensitive to the temperature of blood. The skin also has temperature receptors and sends nervous impulses to the brain via sensory neurones. the brain responds to this information by sending nerve impulses to effectors in the skin to maintain the temperature within a narrow range of the optimum.

Question 46

What is fatty tissue?

Answer 46

Fatty tissue under the dermis acts as a layer of insulation to prevent too much body heat being lost through the skin.

Question 47

Chart showing how the human body regulates temperature

Answer 47

Question 48

What does the body do when we are hot to cool us down?

Answer 48

Sweat is secreted by sweat glands, this cools skin by evaporation. Heat energy from the body is lost as liquid water in sweat becomes water vapour.
Hairs lie flat against the skin, allowing air to freely circulate. This increases heat transfer to the environment by radiation.

Question 49

What does our body do when we are cold to warm us up?

Answer 49

Skeletal muscles contract rapidly, and we shiver, this is an involuntary muscle contraction, and it needs energy from respiration and some of this is released as heat.
Erect hairs trap a layer of air around the skin, which acts as an insulator, preventing heat loss by radiation.

Question 50

What is vasoconstriction?

Answer 50

When we are cold, blood flow in capillaries slows down because arterioles leading to the skin capillaries get narrower, this is known as vasoconstriction. This reduced the amount of heat lost from the blood by radiation as less blood flows through the surface of the skin.

Question 51

What is vasodilation?

Answer 51

When we are hot, blood flow in capillaries increases because blood vessels to the skin capillaries gets wider, this is known as vasodilation. This cools the body as blood is flowing at a faster rate through the skins surface so more heat is lost by radiation.

Question 52

What is gravitropism?

Answer 52

Gravitropism is a response in which parts of a plant grow towards or away from gravity.

Question 53

What is phototropism?

Answer 53

Phototropism is a response in which parts of a plant grow towards to away from the direction of the light source.

Question 54

What is the difference between a positive and a negative response?

Answer 54

Growing towards a stimulus is known as a positive response and growing away from the stimulus is a negative response.

Question 55

What is auxin?

Answer 55

Auxin controls the direction of growth of roots or stems.

Question 56

What is the function of auxin?

Answer 56

Auxin is mostly made in the tips of the growing stems and roots and can diffuse to other parts of the stems or roots, spreading from a high concentration in the shoot tips down the shoot to an area of lower concentration. Auxin stimulates the cells behind the tip to elongate (get larger); the more auxin there is, the faster they will elongate and grow. Only the region behind the tip of a shoot is able to contribute to growth by cell division and cell elongation