3.5.1 Structures for Response
Objectives – What you will need to
know from this section
 Chemical or Hormonal Systems
 Nerve and Sense Organ System
 Movement, to include Growth and the Muscular and
Skeletal Systems
 An Immune System, e.g. response to viral infection
3.5.1 Structures for response
1. Chemical or Hormonal Systems
Animals
The ability to detect change and to
respond is called sensitivity. Response
is a form of defence that allows
organisms to survive.
 The endocrine system is
a group of specialised
tissues (glands) that
produce chemicals
called hormones, many
of which are proteins.
Pituitary
O
Thyroid
Pancreas
Adrenal
 Hormones are chemical ‘messengers’, produced in
specialised glands, and transported in the blood to a
particular area (the target organ), where they have their
effect.
 The endocrine glands are often called ductless glands.
 Exocrine glands have ducts to carry their secretions,
e.g. salivary glands.
 The endocrine glands interact with the
nervous system to provide the
communication, co-ordination and control
within the body.
 The action of hormones is slower and more general than
nerve action
 They control mainly long-term changes such
as growth, metabolism and sexual maturity.
Comparison of the endocrine and nervous systems - 1
Endocrine
Cells involved
Gland
Message
Chemical
(Hormone)
Carried by
Blood
Message sent to
Cells throughout
the body
Received by
Target organ
Comparison of the endocrine and nervous systems - 1
Endocrine
Nervous
Cells involved
Gland
Sense receptor
Message
Chemical
(Hormone)
Electrical(Impulse)
Carried by
Blood
Nerve cell
Message sent to
Cells throughout
the body
A specific cell or
tissue
Received by
Target organ
Effector (muscle or
gland)
Comparison of the endocrine and nervous systems -- 2
Endocrine
Speed of
transmission
Usually slow
Effects
Can be widespread
Duration
long-lasting
(hours)
Comparison of the endocrine and nervous systems -- 2
Endocrine
Nervous
Speed of
transmission
Usually slow
Rapid
Effects
Can be widespread Localised usually
Duration
long-lasting
(hours)
Usually brief
(seconds)
LEARNING CHECK
•
•
•
•
•
What is sensitivity?
What are endocrine glands?
What are exocrine glands?
What is the nervous system?
Give the main differences between the
nervous and endocrine systems.
1. Chemical or Hormonal Systems
Plants
The ability to detect change and to respond is called
sensitivity. Response is a form of defence that allows
organisms to survive.
 Growth is the increase in the number, size and volume
of cells.
Plant adapt to new situations by modifying their growth,
by means of chemicals called growth regulators
[hormones].
 A hormone is a chemical produced in one part of an
organism, transported to other tissues where it has
its effect.
 External factors that regulate the growth of plants are light
intensity, day length, gravity, temperature.
 Development means the
changes that lead to specialised
tissues and organs.
 Plant growth regulators [hormones] are chemicals that
interact with one another to control a particular
development or response.
 They are transported
through the vascular
system of the plant.
 Some regulators promote growth e.g. auxins,
gibberellins, cytokinins.
New roots developing
 Some regulators inhibit growth e.g. abscisic acid and
ethene.
Growth shut down for
winter
LEARNING CHECK
•
•
•
•
•
What is meant by growth?
What is meant by development?
What are growth regulators?
What is vascular tissue?
What is the difference between promoting
and inhibiting growth?
2. Nerve and Sense Organ System
 A nervous system allows an organism to detect and
respond to stimuli in its internal or external environment.
 A stimulus is any change in your environment
 e.g. a flash of light, a noise, a fly landing on your nose.
 The nervous system relies on electrical signals, carried by
specialised cells, and is involved in fast responses.
 The brain keeps a check on internal
organs and activities, such as the level
of carbon dioxide or water in the
blood.
Comparison of the endocrine and nervous systems - 1
Endocrine
Cells involved
Gland
Message
Chemical
(Hormone)
Carried by
Blood
Message sent to
Cells throughout
the body
Received by
Target organ
Comparison of the endocrine and nervous systems - 1
Endocrine
Nervous
Cells involved
Gland
Sense receptor
Message
Chemical
(Hormone)
Electrical(Impulse)
Carried by
Blood
Nerve cell
Message sent to
Cells throughout
the body
A specific cell or
tissue
Received by
Target organ
Effector (muscle or
gland)
Comparison of the endocrine and nervous systems -- 2
Endocrine
Speed of
transmission
Usually slow
Effects
Can be widespread
Duration
long-lasting
(hours)
Comparison of the endocrine and nervous systems -- 2
Endocrine
Nervous
Speed of
transmission
Usually slow
Rapid
Effects
Can be widespread Localised usually
Duration
long-lasting
(hours)
Usually brief
(seconds)
LEARNING CHECK
• What is a stimulus
• What is the nervous system?
• Give the main differences between the
nervous and endocrine systems.
3. Movement, to include Growth and the Muscular and
Skeletal Systems
Skeletons provide
 support,
 protection of
internal organs
 and a rigid frame
for movement.
 Muscles pull on bones and so provide movement.
4. An Immune System
 Immunity is the ability
of an organism to
resist infection.
 The human body is
designed to protect
itself from foreign cells
or invaders, and we
have two lines of
defence -general and
specific.
 Our General Defence System consists of: Skin,
Mucous membranes, Platelets and White blood cells.
 Our Specific Defence System involves an antigenantibody response, involving speciliased white blood
cells
LEARNING CHECK
• Give 3 function of the Musculoskeletal
system.
• What is immunity?
• Name some of the ways germs can enter the
body.
• Name the parts of our general defence
system.
• What cells are involved in our Specific
Defence sytem?