Control Systems | Edexcel A-Level Biology B (9BI0)

Control Systems

265 questions
19 subtopics
Topics 8 to 10, examined on Paper 2 and Paper 3
Paper 2 and Paper 3

How mammals and plants keep conditions steady and respond to change: negative feedback, hormonal and plant chemical control, the nervous system from brain regions to synapse, the eye, the control of heart rate, and the kidney's role in osmoregulation..

It covers homeostasis and negative feedback, chemical control in mammals, plant growth substances, auxins, cytokinins and apical dominance, phytochrome and photomorphogenesis, the organisation of the nervous system, brain regions and divisions of the peripheral nervous system, the autonomic nervous system, resting potential and the action potential, propagation and saltatory conduction, synaptic transmission, effects of drugs on the nervous system, the structure of the retina and rhodopsin, rods, cones and visual acuity, control of heart rate, kidney structure and ultrafiltration, selective reabsorption and the loop of Henle, aDH and osmoregulation and thermoregulation in endotherms.

Sample questions from Control Systems

Answer each one closed book first, then open the answer.

Homeostasis and negative feedback

Define negative feedback.

Show the answer
A control mechanism where a deviation from the set point triggers a response that returns the system towards the set point.
Plant growth substances

Explain the role of gibberellin during seed germination in cereals.

Show the answer
Gibberellin stimulates the production of amylase, which digests starch reserves to provide sugars for the growing embryo.
Phytochrome and photomorphogenesis

Which pigment controls photomorphogenesis in plants?

Show the answer
Phytochrome.
Brain regions and divisions of the peripheral nervous system

Which brain region is responsible for initiating voluntary movement?

Show the answer
The cerebrum.
Resting potential and the action potential

Why is the axon membrane more permeable to potassium ions than sodium ions at rest?

Show the answer
Because potassium leak channels are open at rest, allowing K⁺ to diffuse out of the axon.
Synaptic transmission

Describe how neurotransmitter molecules reach and affect the postsynaptic neurone.

Show the answer
Neurotransmitter molecules diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic membrane.
The structure of the retina and rhodopsin

What is the function of the pigment epithelium located behind the photoreceptors?

Show the answer
It absorbs stray light to prevent reflection within the eye.
Control of heart rate

How does noradrenaline affect the sinoatrial node?

Show the answer
It increases heart rate by increasing the frequency of electrical impulses generated at the SAN.

The 19 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Homeostasis and negative feedback	Recall questions on receptors, the control centre and effectors, negative feedback, and why positive feedback is the exception.	15
Chemical control in mammals	Recall questions on endocrine glands and target cell receptors, and the two modes of hormone action: second messengers for water-soluble hormones such as adrenaline, and direct binding to transcription factors for lipid-soluble hormones such as oestrogen.	16
Plant growth substances	Recall questions on auxins, cytokinins and gibberellins as plant growth substances, how gibberellin stimulates amylase production in germinating cereals, and the starch agar assay used to investigate it.	14
Auxins, cytokinins and apical dominance	Recall questions on how auxin promotes cell elongation and root growth, apical dominance, and how the antagonistic balance of auxin and cytokinin controls the growth of lateral buds.	8
Phytochrome and photomorphogenesis	Recall questions on phytochrome as a photoreceptor pigment, photomorphogenesis and flowering, the interconversion of Pr and Pfr by red and far-red light, Pfr as the active form, and how its reversion in darkness lets plants measure day length.	11
The organisation of the nervous system	Recall questions on the central and peripheral nervous systems, the brain and spinal cord, grey and white matter in the spinal cord, and the sensory and motor neurones of the dorsal and ventral roots.	10
Brain regions and divisions of the peripheral nervous system	Recall questions on the roles of the medulla oblongata, cerebellum, cerebrum and hypothalamus, and the division of the peripheral nervous system into the voluntary and autonomic nervous systems.	12
The autonomic nervous system	Recall questions on the sympathetic and parasympathetic divisions of the autonomic nervous system, their fight-or-flight and rest-and-digest effects on heart and breathing rate, and why antagonistic control allows fine adjustment.	8
Resting potential and the action potential	Recall questions on the resting potential, the sodium-potassium pump and potassium leak channels, threshold, depolarisation through voltage-gated sodium channels, repolarisation through potassium channels, and hyperpolarisation.	17
Propagation and saltatory conduction	Recall questions on local currents and the propagation of action potentials, the refractory period, Schwann cells, nodes of Ranvier and saltatory conduction, and why myelinated axons conduct faster.	10
Synaptic transmission	Recall questions on the sequence at a cholinergic synapse, the role of calcium, and summation and inhibition.	21
Effects of drugs on the nervous system	Recall questions on agonists and antagonists, and on how named drugs alter synaptic transmission.	13
The structure of the retina and rhodopsin	Recall questions on the photoreceptor, bipolar and ganglion cell layers of the retina, the path of light, the pigment epithelium, the optic nerve and blind spot, and how light converts retinal and bleaches rhodopsin.	12
Rods, cones and visual acuity	Recall questions on the distribution and connections of rods and cones, and how they explain acuity and sensitivity.	20
Control of heart rate	Recall questions on the cardiovascular centre, the effect of the sympathetic and parasympathetic nerves, and the role of baroreceptors and chemoreceptors.	28
Kidney structure and ultrafiltration	Recall questions on the cortex, medulla and nephron, the glomerulus, Bowman's capsule and podocytes, how high hydrostatic pressure drives ultrafiltration through the filtration barrier, and deamination and urea formation in the liver.	16
Selective reabsorption and the loop of Henle	Recall questions on reabsorption in the proximal tubule, and on how the counter-current multiplier concentrates the medulla.	13
ADH and osmoregulation	Recall questions on the long loops of Henle of the kangaroo rat, osmoreceptors in the hypothalamus, ADH release from the posterior pituitary, aquaporins in the collecting duct, and osmoregulation as negative feedback.	8
Thermoregulation in endotherms	Recall questions on the hypothalamus, vasodilation and vasoconstriction, sweating and shivering, and behavioural responses.	13

Control Systems is 265 of the 2,073 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.