Biology - 9201 OxfordAQA

Homeostasis

Gbogbo ọrọ náà

Step out of an air-conditioned classroom into the midday heat and the air around you may jump fifteen degrees in a single second. Your blood will not. By the time you reach the gate, the temperature deep inside you has moved by perhaps a tenth of a degree, and something has already begun putting even that small change back. Nobody decided any of it. You were thinking about lunch.

This lesson is about the machinery behind that steadiness. You will learn what homeostasis actually means, why your enzymes and your cells would be in serious trouble without it, and the three-part pattern that every automatic control system in your body is built from: something that detects, something that decides, something that acts. Once you can see that pattern, temperature control, blood glucose and water balance stop being three things to memorise and become three versions of one idea.

Ebumnobi

Automatic control systems in the body keep conditions inside the body relatively constant.
Control systems include: cells called receptors, which detect stimuli (changes in the environment); coordination centres that receive and process information from receptors; effectors, which bring about responses.
Receptors are found in many organs, including: the eyes - sensitive to light; the ears - sensitive to sound, and to changes in position (which enables us to keep our balance); the tongue and in the nose - sensitive to chemicals (enable us to taste and to smell); the skin - sensitive to touch, pressure, pain and to temperature changes; the brain - sensitive to blood temperature and the concentration of water in the blood; the pancreas - sensitive to the concentration of glucose in the blood. Knowledge and understanding of the structure and functions of sense organs such as the eye and the ear is not required.
Coordination centres include the brain and spinal cord and the pancreas.
Internal conditions that are controlled include: temperature; the water content of the body; the ion content of the body; blood glucose levels.

Maapụ uche

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Akwụkwọ Ọmụmụ

A trader stands in a market in Kano at two in the afternoon. The air is at 39 °C. Six hours later, on the walk home, it has dropped to 21 °C. Over that same stretch of the day the temperature of the blood leaving her heart has stayed within about half a degree of 37 °C. She has eaten a plate of rice, drunk very little water and walked several kilometres, and the concentration of glucose and of salts in her blood has barely shifted either.

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Nnyocha Ọmụmụ

Ekele diri gi maka imecha ihe karịrị na Homeostasis. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

Which statement best describes homeostasis? A. Keeping conditions outside the body constant B. Keeping conditions inside the body relatively constant C. Preventing any change in the body at all D. Increasing the rate of all reactions in the body Answer: B
Which of these is a coordination centre named in the specification? A. The skin B. The eye C. The pancreas D. A sweat gland Answer: C
Which organ contains receptors sensitive to the concentration of glucose in the blood? A. The liver B. The pancreas C. The kidney D. The spinal cord Answer: B
Which of the following is NOT one of the internal conditions controlled by homeostasis in humans? A. Body temperature B. The water content of the body C. The ion content of the body D. The loudness of sounds reaching the ear Answer: D
In a negative feedback system, the response produced by the effectors: A. acts in the same direction as the original change B. acts in the opposite direction to the original change C. has no effect on the original change D. removes the need for receptors Answer: B

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