GCSE Biology - homeostasis and response

Flashcards covering essential vocabulary and concepts from GCSE Biology on Organisation.

Homeostasis

The regulation of internal conditions to maintain a stable internal environment, in response to internal and external changes.

Control system components

Receptors, coordination centres (e.g. brain, spinal cord, pancreas), and effectors.

Receptors

Detect changes in the environment (stimuli).

Coordination centres

Receive and process information from receptors and organise a response.

Effectors

Muscles or glands that bring about responses to restore optimum levels.

Central nervous system (CNS)

Made up of the brain and spinal cord.

Reflex arc

Stimulus -> receptor -> sensory neurone -> relay neurone (in spinal cord) -> motor neurone -> effector -> response.

Purpose of reflexes

To provide rapid, automatic responses that protect the body.

Synapse

A gap between two neurones where nerve signals are transmitted by chemicals (neurotransmitters).

Measuring reaction time

Can be done using a ruler drop test, computer tests, or measuring response time to a stimulus.

Variables in reaction time experiments

Hand used, distance ruler is dropped from, environment (noise/light), time of day.

Main parts of the brain

Cerebral cortex (intelligence/memory/language), cerebellum (muscle coordination), medulla (unconscious activities like breathing/heartbeat).

Cornea

Transparent front layer that refracts light.

Iris

Controls how much light enters the eye by adjusting pupil size.

Lens

Focuses light onto the retina.

Retina

Contains receptor cells sensitive to light and colour.

Adjustment to bright light

Bright: circular muscles contract, pupil constricts.

Adjustment to dim light

Dim: radial muscles contract, pupil dilates.

Accommodation

The process by which the lens changes shape to focus on near or distant objects.

Myopia

Short-sightedness - distant objects appear blurry as light focuses in front of the retina.

Hyperopia

Long-sightedness - close objects appear blurry as light focuses behind the retina.

Correction of vision defects

Can be corrected with concave/convex lenses, contact lenses, laser eye surgery, or lens replacement.

Body temperature monitoring

Monitored by the thermoregulatory centre in the brain, containing receptors sensitive to blood temperature.

Responses to being too hot

Sweat production, blood vessel dilation (vasodilation), hairs lie flat.

Responses to being too cold

Hairs stand up, no sweat, vasoconstriction occurs, shivering increases respiration.

Hormones

Chemical messengers released into the blood by glands to target specific organs.

Differences between hormones and nerves

Hormones have slower action, longer-lasting effects, and act in a more general way.

Endocrine system

A system of glands that produce hormones, including the pituitary, pancreas, thyroid, adrenal, ovaries, and testes.

Insulin

Hormone that lowers blood glucose by facilitating glucose movement from blood into cells and storage as glycogen.

Glucagon

Hormone that increases blood glucose by converting glycogen back into glucose.

Type 1 diabetes

A condition where the pancreas produces little or no insulin. Treated with insulin injections.

Type 2 diabetes

The body becomes resistant to insulin. Treated with diet, exercise, and medication.

Menstrual cycle

Monthly cycle involving the release of an egg and preparation of the uterus lining.

Hormones in the menstrual cycle

The four main hormones are FSH, LH, oestrogen, and progesterone.

FSH (Follicle Stimulating Hormone)

Stimulates egg maturation and oestrogen production.

LH (Luteinizing Hormone)

Stimulates the release of an egg (ovulation).

Oestrogen

Stimulates LH, inhibits FSH, and thickens the uterus lining.

Progesterone

Maintains the uterus lining and inhibits FSH and LH.

Oral contraceptives

Contain hormones (oestrogen and progesterone) to inhibit FSH so no egg matures.

Fertility drugs

Contain FSH and LH to stimulate egg release.

IVF (In Vitro Fertilization)

Eggs fertilised outside body then implanted, involves hormones and embryo screening.

Issues with IVF

Expensive, low success rate, multiple births, and ethical concerns.

Auxin

A plant hormone that controls growth towards light (phototropism) and against gravity (gravitropism).

Gibberellin

A plant hormone used to stimulate seed germination, stem growth, and flowering.

Ethene

A plant hormone that controls cell division and ripening of fruit.

Plant hormones in agriculture

Used in weedkillers, rooting powders, controlling fruit ripening and dormancy.