Download Coordination and Regulation Check 4 (Solutions)

Name: ___________________________________
Cell functioning: Control
VCE Biology- Unit 3
Coordination and regulation are considered at the cellular, rather than whole organism, level.
References to homeostasis and feedback mechanisms have been deleted from Unit 3. The treatment of homeostasis at a systems
level, including feedback mechanisms, involving hormonal control (for example, regulation of blood glucose), water balance and
temperature control, is included in Unit 2 Biology.
1. What are signaling molecules? Give 4 types of signaling molecules.
Signaling molecules carry signals or messages (chemical or electrical) from one cell to another.
Types: neurotransmitters, animal hormones, pheromones and plant growth hormones
2. Write the functions of each of the four signaling molecules listed in Q1.
Neurotransmitters: Compounds produced and released at the ends of axons, such as acetylcholine. They bind
to specific receptors on target cell to initiate a response in that cell.
Animal hormones: Transported through bloodstream to all parts of the body but will only have an effect on
specific target organs. Hormones modify the activity of cells as a result of interaction with specific
receptors.
Pheromones: Released into the atmosphere. They provide communication between individuals.
Plant growth hormones: Control growth responses in plants so that growth occurs in the correct way and so
the timing of plant activity is optimal.
3. Why do hormones only affect target cells?
Hormones only affect target cells as target cells alone have the protein receptors that match the specific
hormone.
4. Are hormones excreted or secreted? What is the difference between the two terms?
Hormones are secreted into the bloodstream. The term excretion refers to the movement of metabolic waste
material out of the body across an external boundary. For example, the movement of CO2 from the lung
capillaries to the alveoli of the lungs.
5. How do exocrine and endocrine glands differ? What type of gland produces hormones?
Exocrine glands (e.g. tear glands) are involved in the excretion of materials through ducts from the internal
environment to the external environment. Endocrine glands (ductless glands) are involved in internal
secretion into the bloodstream. Hormones are produced by endocrine glands.
6. List the major hormone producing glands of the body noting the hormones produced.
Gland
Pituitary
Hypothalamus
Thyroid
Adrenals
Pancreas
Testes
Ovaries
Hormones
Growth hormones and others
Many
Thyroxine
Adrenalin
Cortisol
Insulin
Glucagon
Testosterone
Oestrogen
Progesterone
Regulation
Master gland
Many activities including
temperature regulation
Metabolism and growth
Response to stress
Metabolism
Blood glucose concentration
Fertility and secondary sex
characteristics
Name: ___________________________________
7. Complete the following table.
Type of
Solubility
hormone
Proteins
and amino Water-soluble
acid- based
Steroids
Lipid-soluble
Site of
receptor
External
cell surface
membrane
Cytoplasm/
Nucleus
VCE Biology- Unit 3
Action within the cell
Interact with G-linked
proteins to produce a second
messenger which affects the
activity of enzymes
Alters gene transcription
Speed
fast
slow
Example
Thyroxine
Adrenaline
Insulin
Glucagon
Oestrogen
Testosterone
Transduction for both lipid-based and protein-based signaling molecules involves a cascade of reactions that
amplify the initial message, and can lead to a range of cellular responses. Names of second messengers are
not required and G protein pathways do not need to be defined.
8. In simple (general) terms, explain the process of signal transduction involving lipid-based AND proteinbased signaling molecules? (Note: names of second messengers are not required and G-protein pathways
do not need to be defined)
Hint: This process can be described as a three-step process, using the stimulus-response model.
Three-step process:
Reception (information is received by a cell’s receptor)
Transduction (information from the receptor is passed on to an effector), and
Induction/response (various cellular responses are initiated).
Lipid-based signaling molecules:
Lipid-based (water insoluble, lipid soluble) signaling molecules are able to pass straight through the cell
membrane to bind onto receptors within the cytosol to initiate transduction.
Protein-based signaling molecules:
Protein-based (water soluble, lipid insoluble) signaling molecules, which are unable to pass through the cell
wall, bind to receptors on the surface of the cell membrane, thereby activating a second messenger within
the cytosol to initiate transduction.
9. The stimulus-response model is often used to explain how organisms respond to stimuli. What is the
stimulus-response model?
stimulus ------> receptor ------> message/ (control centre)/message ------> effector ------> response
10. List 5 types of receptors and their stimuli.
1. Chemoreceptor: smell, taste
2. Mechanoreceptor: touch, pressure, sound
3. Photoreceptor: light
4. Thermoreceptor: temperature
5. Pain receptor: pain
11. Negative feedback helps bring about homeostasis. What is negative feedback and how is it different to
positive feedback?
Negative feedback is when a response to a stimulus results in a reduction of (counteracts) that stimulus
whereas in positive feedback the response to a stimulus results in reinforcement of the original stimulus.
12. What are the major components and a neuron (nerve cell)?
Axon, axon terminals, dendrite and cell body
Name: ___________________________________
VCE Biology- Unit 3
13. Name and explain the differences between the three types of nerve cells.
Sensory neurons have long dendrites that carry nervous information from a sense organ towards its cell
body and the central nervous system.
Connecting neurons (or intermediate neurons) have short dendrites and axons. They are found entirely
within the central nervous system (CNS).
Motor neurons have long axons and carry information from the CNS to effector organs such as muscles.
14. Draw a diagram of a simple nerve pathway from a receptor to an effector. Show the three neurons in the
pathway and indicate the direction a nerve impulse would travel.
CNS
15. What is a nerve impulse and how is one passed along a nerve?
A nerve impulse is an electrical message that passes along the conducting fibres (dendrites and axons) of a
neurone. The impulse is conducted along a fibre as a change in charge on the fibre membranes. At rest, the
cell membrane of a neurone is polarised. Sodium/potassium pumps actively pump sodium ions out and
potassium ions into the cell. The net result is more sodium ions outside the cell than potassium ions inside
the cell, therefore the inside is more negative. As the impulse passes along, the cell membrane becomes
more permeable to sodium ions which move into the cell. At this point, the inside of the membrane will have
a positive charge compared to the outside. Once the impulse has passed, the ions involved are returned to
their original position so the nerve is ready for another impulse. These changes are extremely rapid.
16. Which way does a nerve impulse pass along nerve cells?
Nerve impulses are generated at sense organs at the dendrite end of neurons therefore they always pass from
dendrites to the axon terminals within a nerve cell. Note that an artificially induced impulse can travel in
either direction along a neuron.
17. How does a nerve impulse pass from one nerve cell to the next?
A tiny gap exists between nerve cells (neurons). This is called the synaptic gap. An impulse does not pass
directly from one cell to the next. At the end of axon terminals are synaptic knobs with many mitochondria
and vesicles containing neurotransmitter. When an impulse reaches a synaptic knob, calcium ions diffuse
into the cell from the ECF. This stimulates the vesicles to move towards and fuse with the cell membrane
releasing the neurotransmitter into the synaptic gap. It diffuses across the gap to protein receptors on the
dendrites of an adjacent nerve cell. This results in the opening of protein channels allowing sodium ions to
move in and stimulates the production of a nerve impulse in this neuron. In this way, the message can be
passed on from one cell to the next.
Name: ___________________________________
VCE Biology- Unit 3
18. Explain the differences between a peripheral nervous system and the central nervous system.
The PNS consists of sensory neurons collecting information from receptors around the body (at the
periphery) and motor neurons taking information to effector organs such as muscles and glands.
The CNS consists of connecting neurons (intermediate neurons) located in the spinal cord and the brain.
These are enclosed by the bones of the skull and vertebral column. The sensory neurons end at the CNS and
the motor neurons begin at the CNS.
19. In mammals, how does a simple reflex reaction pathway differ from the pathway involved when a
conscious decision is made?
Information involved in reflex arcs can involve a minimum of three neurons and no connection to the brain.
If a conscious decision is involved, the impulse must travel to the brain before travelling to motor neurons.
20. How are the functions of the autonomic and somatic nervous systems different?
The autonomic system is involved in the control or organs such as the heart, lungs and digestive system
where there is normally no conscious control. The somatic system involves nerve pathways where an
individual has conscious control.
21. Describe three major differences between the functioning of the nervous and endocrine systems.
1. Speed of transmission: nerve impulses travel at rates thousands of times faster than hormones.
2. The hormone system is a purely chemical system. The nervous system involves chemical and electrical
components.
3. The effects of a nervous impulse are short-lived and act on a directly connected organ. The effects of
hormones can be long lasting and widespread. For example, growth hormones have effects all around the
body.
Name: ___________________________________
Regulation in Plants:
VCE Biology- Unit 3
The distinction between different types of growth regulators (auxins, cytokinins, gibberellins, abscisic acid
and ethylene) are not required, although teachers may use one or more of them to illustrate a particular
signal transduction pathway.
22. Growth responses of plants to their environment are called tropisms. Name the major types and state the
environmental factor to which the plant is responding.
Major environmental factors that plants respond to are: light (phototropism), gravity (geotropism), water
(hydrotropism), and touch (thigmotropism).
23. How do positive and negative tropisms differ?
Positive tropisms result when a plant grows towards an environmental stimulus, e.g. plant growing towards
light.
Negative tropisms involve growth away from the stimulus, e.g. plant stems grow upwards away from
gravity even if light is not present.
24. What, in general terms, is the role of plant growth regulators?
Plant growth regulators control growth responses in plants so that growth occurs in the correct way and so
that timing of plant activity is optimal. For example, many plants grow rapidly in the spring and then flower.
At this time growth conditions are best. There is plenty of water and warmth. In a good season the plant will
grow rapidly, flower and produce seeds within a few months. All of these events are regulated by plant
growth regulators.
25. Explain the role of receptors and effectors in plant responses.
A receptor is a group of cells that detect changes in the environment. These cells produce plant growth
regulators that move through the plant tissue, usually by diffusion, to effectors. The effectors will bring
about the response to the stimulus detected by the receptors.
26. Complete the following table.
Signaling
molecule
neurotransmitters
hormones
pheromones
plant growth
regulators
Receptor
Proteins on the external cell
membranes of neurons, muscle
or gland cells.
Proteins on the external cell
membranes or in the
cytoplasm/nucleus of target cells
Protein receptors on the smell
and taste receptors of another
individual
Proteins on the external cell
membranes or within the cell
Cellular response
Example
Excitation or inhibition
Acetylcholine
Dopamine
Affect the activity of
enzymes or gene
transcription
Affect the activity of
enzymes or gene
transcription
Affect the activity of
enzymes or gene
transcription
Insulin
Steroids
Scent trails
Auxin
Ethylene