Flashcards · 0610 · Topic 14

Coordination and response flashcards

29 cards on Topic 14, subtopics 14.1 to 14.5. Pick a subtopic or study them all.

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Central and peripheral nervous systems: CNS: brain and spinal cord. PNS: the nerves outside the brain and spinal cord.
Reflex arc, in order: Receptor → sensory neurone → relay neurone → motor neurone → effector (muscle or gland).
Reflex action: A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands).
SynapseExtended: A junction between two neurones.
Events at a synapseExtended: An impulse arrives → neurotransmitter is released from vesicles into the synaptic gap → it diffuses across the gap → binds with receptor proteins on the next neurone → a new impulse is stimulated.
Why do impulses cross a synapse in one direction only?Extended: Neurotransmitter is released only from the vesicles on one side, and the receptor proteins are only on the next neurone.

Sense organ: A group of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals.
Functions of the cornea, iris and lens: Cornea: refracts light. Iris: controls how much light enters the pupil. Lens: focuses light on to the retina.
Functions of the retina and optic nerve; what is the blind spot?: Retina: contains light receptors, some sensitive to different colours. Optic nerve: carries impulses to the brain. Blind spot: where the optic nerve leaves; no receptors.
Pupil reflex: Bright light: pupil diameter decreases. Dim light: pupil diameter increases.
Iris muscles in bright and in dim lightExtended: Bright: circular muscles contract, radial muscles relax, pupil constricts. Dim: radial muscles contract, circular muscles relax, pupil dilates.
Accommodation for a near objectExtended: Ciliary muscles contract → suspensory ligaments slacken → lens becomes fatter (more convex) → light refracted more. For a distant object, every step is reversed.
Rods vs conesExtended: Rods: more sensitive to light, give night vision, spread over the retina. Cones: three kinds, for colour vision, concentrated at the fovea.

Hormone: A chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs.
Glands and their hormones: adrenal glands, pancreas, testes, ovaries: Adrenal glands: adrenaline. Pancreas: insulin. Testes: testosterone. Ovaries: oestrogen.
Effects of adrenaline ("fight or flight"): Increased breathing rate, heart rate and pupil diameter.
Nervous vs hormonal control: Nervous: fast action, short-lived effect. Hormonal: slower action, longer-lasting effect.
Role of adrenaline in controlling metabolic activityExtended: It increases the blood glucose concentration and the heart rate.

Homeostasis: The maintenance of a constant internal environment.
Effect of insulin on blood glucose (Core): Insulin decreases the blood glucose concentration.
Negative feedbackExtended: A change away from the set point triggers a response that reverses the change.
Control of blood glucose by insulin and glucagonExtended: Too high: pancreas secretes insulin → liver converts glucose to glycogen → level falls. Too low: pancreas secretes glucagon → liver converts glycogen to glucose → level rises.
Treatment of Type 1 diabetesExtended: Insulin injections, monitoring blood glucose, controlling carbohydrate in the diet, and planning exercise.
How the body responds when it is too hotExtended: Sweating (evaporation cools the skin); vasodilation of arterioles supplying skin capillaries, so more heat is lost; hairs lie flat. (Capillaries do not move.)
How the body responds when it is too coldExtended: Shivering (respiration in muscles releases heat); vasoconstriction of arterioles supplying skin capillaries, so less heat is lost; hair erector muscles contract so hairs trap insulating air.

Gravitropism and phototropism: Gravitropism: parts of a plant grow towards or away from gravity. Phototropism: parts of a plant grow towards or away from the direction of the light source.
Responses of shoots and roots to light and gravity: Shoots grow towards light and away from gravity. Roots grow towards gravity and away from light.
Four facts about auxinExtended: Made in the shoot tip; diffuses through the plant from the tip; unequally distributed in response to light and gravity; stimulates cell elongation.
Explain why a shoot lit from one side bends towards the lightExtended: Auxin collects on the shaded side, so cells there elongate more, and the shoot bends towards the light.