Module 5: Communication, Homeostasis & Energy

• What is abscisic acid (ABA) in plants?

  A plant hormone that stimulates stomatal closing, maintains seed dormancy, and triggers cold protective responses.
• What does abscission refer to in plants?

  The shedding of leaves in plants.
• What is acetylcholine?

  A type of neurotransmitter used for communication between neurones.
• What is actin?

  A type of protein filament found in myofibrils that forms thin filaments.
• What happens to the actin-myosin binding site during muscle contraction?

  It becomes exposed, allowing a myosin head to attach.
• What is an actin-myosin cross-bridge?

  The cross-bridge formed when a myosin head attaches to the binding site on an actin filament.
• What is the function of adenylyl cyclase?

  It catalyses the conversion of ATP to cAMP.
• Where are adrenal glands located?

  On the top of the kidneys.
• What role does adrenaline play in the body?

  It serves as a ‘primary messenger’, activating adenylyl cyclase under stressful conditions.
• What is the function of the afferent arteriole?

  It carries blood to the glomerulus for ultrafiltration.
• What are alkaloids?

  A group of nitrogenous compounds found in plants that affect the metabolism of animals or insects.
• What does the all-or-nothing principle describe?

  It describes how any generator potential that reaches or exceeds the threshold potential will produce an action potential of equal magnitude.
• What do alpha cells (α cells) in the pancreas secrete?

  Glucagon to raise glucose concentration.
• What are anisotropic (A) bands in myofibrils?

  The darker bands consisting of overlapping actin and myosin filaments.
• What are anabolic steroids?

  A class of performance-enhancing drugs structurally similar to testosterone.
• What does the anterior pituitary gland do?

  Produces and secretes hormones.
• What is the function of antidiuretic hormone (ADH)?

  It increases the reabsorption of water in the kidney tubules.
• What is an aquaporin?

  A membrane channel used for the selective transport of water in and out of the cell.
• What does the autonomic nervous system control?

  Involuntary activities and carries nerve impulses to muscles and glands.
• What are auxins?

  A class of plant hormones that control cell elongation and produce tropisms.
• What is the function of an axon?

  It carries impulses away from the cell body.
• What do beta cells (β cells) in the pancreas secrete?

  Insulin to lower glucose concentration.
• What are bile canaliculi?

  Vessels that collect bile produced by hepatocytes.
• What is the blinking reflex?

  The involuntary blinking of the eyelid when an object is held close to the eye.
• What is cardiac muscle?

  A myogenic muscle found in the walls of the heart.
• What does the central nervous system (CNS) consist of?

  The brain and spinal cord.
• What is the cerebellum responsible for?

  Controlling muscle coordination and non-voluntary movement.
• What is the cerebrum?

  The largest region of the brain responsible for voluntary and some involuntary responses.
• What is a cholinergic synapse?

  A synapse that uses the neurotransmitter acetylcholine.
• What is creatine phosphate?

  A compound stored in muscles that serves as a phosphate reserve for ATP regeneration.
• What is cutting in plant propagation?

  A small section of the root or stem of an adult plant.
• What is cyclic AMP (cAMP)?

  A ‘second messenger’ involved in the action of adrenaline that activates protein kinase.
• What is a dendron?

  An extension from a nerve cell that carries impulses towards the cell body.
• What is depolarisation in nerve cells?

  The rapid influx of sodium ions that causes the cell to lose its negative charge.
• What is an ectotherm?

  An organism that depends on its environment to maintain its body temperature.
• What is an effector?

  An organ, tissue, or cell that produces a response to a stimulus.
• What is the function of the efferent arteriole?

  It carries blood away from the glomerulus after ultrafiltration.
• What is endocrine signalling?

  A type of signalling that uses hormones secreted into the blood to produce an effect on receptors.
• What is an endotherm?

  An organism that can regulate its own body temperature without relying on external heat sources.
• What is ethene in plants?

  A plant hormone that stimulates the ripening of fruit and promotes abscission.