C3.1 Integration of body systems Flashcards
C3.1.1—System integration
This is a necessary process in living systems. Coordination is needed for component parts of a system to
collectively perform an overall function.
C3.1.2—Cells, tissues, organs and body systems as a hierarchy of subsystems that are integrated in a
multicellular living organism
Students should appreciate that this integration is responsible for emergent properties. For example, a
cheetah becomes an effective predator by integration of its body systems.
C3.1.3—Integration of organs in animal bodies by hormonal and nervous signalling and by transport of
materials and energy
Distinguish between the roles of the nervous system and endocrine system in sending messages. Using
examples, emphasize the role of the blood system in transporting materials between organs.
C3.1.4—The brain as a central information integration organ
Limit to the role of the brain in processing information combined from several inputs and in learning and
memory. Students are not required to know details such as the role of slow-acting neurotransmitters.
C3.1.5—The spinal cord as an integrating centre for unconscious processes
Students should understand the difference between conscious and unconscious processes.
C3.1.6—Input to the spinal cord and cerebral hemispheres through sensory neurons
Students should understand that sensory neurons convey messages from receptor cells to the central
nervous system.
C3.1.7—Output from the cerebral hemispheres to muscles through motor neurons
Students should understand that muscles are stimulated to contract.
C3.1.8—Nerves as bundles of nerve fibres of both sensory and motor neurons
Use a transverse section of a nerve to show the protective sheath, and myelinated and unmyelinated
nerve fibres.
C3.1.9—Pain reflex arcs as an example of involuntary responses with skeletal muscle as the effector
Use the example of a reflex arc with a single interneuron in the grey matter of the spinal cord and a free
sensory nerve ending in a sensory neuron as a pain receptor in the hand.
C3.1.10—Role of the cerebellum in coordinating skeletal muscle contraction and balance
Limit to a general understanding of the role of the cerebellum in the overall control of movements of the
body
C3.1.11—Modulation of sleep patterns by melatonin secretion as a part of circadian rhythms
Students should understand the diurnal pattern of melatonin secretion by the pineal gland and how it
helps to establish a cycle of sleeping and waking.
C3.1.12—Epinephrine (adrenaline) secretion by the adrenal glands to prepare the body for vigorous
activity
Consider the widespread effects of epinephrine in the body and how these effects facilitate intense muscle
contraction.
C3.1.13—Control of the endocrine system by the hypothalamus and pituitary gland
Students should have a general understanding, but are not required to know differences between
mechanisms used in the anterior and posterior pituitary
C3.1.14—Feedback control of heart rate following sensory input from baroreceptors and chemoreceptors
Include the location of baroreceptors and chemoreceptors.
Baroreceptors monitor blood pressure. Chemoreceptors monitor blood pH and concentrations of oxygen
and carbon dioxide. Students should understand the role of the medulla in coordinating responses and
sending nerve impulses to the heart to change the heart’s stroke volume and heart rate.
C3.1.15—Feedback control of ventilation rate following sensory input from chemoreceptors
Students should understand the causes of pH changes in the blood. These changes are monitored by
chemoreceptors in the brainstem and lead to the control of ventilation rate using signals to the diaphragm
and intercostal muscles.
C3.1.16—Control of peristalsis in the digestive system by the central nervous system and enteric nervous
system
Limit to initiation of swallowing of food and egestion of faeces being under voluntary control by the
central nervous system (CNS) but peristalsis between these points in the digestive system being under
involuntary control by the enteric nervous system (ENS). The action of the ENS ensures passage of material
through the gut is coordinated.
C3.1.17—Observations of tropic responses in seedlings
Application of skills: Students should gather qualitative data, using diagrams to record their observations
of seedlings illustrating tropic responses. They could also collect quantitative data by measuring the angle
of curvature of seedlings.
NOS: Students should be able to distinguish between qualitative and quantitative observations and
understand factors that limit the precision of measurements and their accuracy. Strategies for increasing
the precision, accuracy and reliability of measurements in tropism experiments could be considered
C3.1.18—Positive phototropism as a directional growth response to lateral light in plant shoots
Students are not required to know specific examples of other tropisms.
C3.1.19—Phytohormones as signalling chemicals controlling growth, development and response to
stimuli in plants
Students should appreciate that a variety of chemicals are used as phytohormones in plants.
C3.1.20—Auxin efflux carriers as an example of maintaining concentration gradients of phytohormones
Auxin can diffuse freely into plant cells but not out of them. Auxin efflux carriers can be positioned in a cell
membrane on one side of the cell. If all cells coordinate to concentrate these carriers on the same side,
auxin is actively transported from cell to cell through the plant tissue and becomes concentrated in part of
the plant.
C3.1.21—Promotion of cell growth by auxin
Include auxin’s promotion of hydrogen ion secretion into the apoplast, acidifying the cell wall and thus
loosening cross links between cellulose molecules and facilitating cell elongation. Concentration gradients
of auxin cause the differences in growth rate needed for phototropism.
C3.1.22—Interactions between auxin and cytokinin as a means of regulating root and shoot growth
Students should understand that root tips produce cytokinin, which is transported to shoots, and shoot
tips produce auxin, which is transported to roots. Interactions between these phytohormones help to
ensure that root and shoot growth are integrated
C3.1.23—Positive feedback in fruit ripening and ethylene production
Ethylene (IUPAC name: ethene) stimulates the changes in fruits that occur during ripening, and ripening
also stimulates increased production of ethylene. Students should understand the benefit of this positive
feedback mechanism in ensuring that fruit ripening is rapid and synchronized.
