Homeostasis and the Human Endocrine System

Homeostasis

Maintaining constant internal conditions, so that cells can survive.

Receptors

Cells that detect stimuli, and pass this information along neurones as electrical impulses.

Coordination centre

The central nervous system, which receives and processes information from receptors.

Effectors

Muscles or glands that make changes to restore optimum levels.

Blood glucose concentration

The level of glucose in the blood that is monitored and controlled by the pancreas.

Body temperature

A physical condition that is maintained within narrow limits for cell survival.

Water levels

A chemical condition that is maintained within narrow limits for cell survival.

Nervous system

One of the two automatic control systems in the body.

Endocrine system

The system made of glands that secrete hormones into the bloodstream.

Reflex Actions

Quick and short lasting responses that do not involve the conscious part of the brain.

Synapses

Gaps between neurones.

Hormones

Chemicals released by glands into the bloodstream that produce effects on target organs.

Negative feedback

When the body responds to a change in a factor by correcting it.

Insulin

A hormone released by the pancreas that causes glucose to move from blood into cells.

Glucagon

A hormone released by the pancreas that causes glycogen to be converted into glucose.

Type 1 diabetes

A disorder where the pancreas does not produce enough insulin.

Type 2 diabetes

A disorder where cells do not respond to insulin, often associated with obesity.

Adrenaline

A hormone produced by the adrenal glands in times of fear or stress that increases heart rate.

Thyroxine

A hormone produced by the thyroid gland that stimulates the basal metabolic rate.

Testosterone

The main male hormone produced by the testes that stimulates sperm production.

Follicle stimulating hormone (FSH)

A hormone produced by the pituitary gland that causes an egg in the ovary to mature.

Luteinising hormone (LH)

A hormone produced by the pituitary gland that causes the mature egg to be released into the oviduct.

Oestrogen

A hormone produced by the ovary involved in thickening the lining of the uterus and inhibiting FSH.

Progesterone

A hormone produced by the ovary involved in maintaining the thickened lining of the uterus.

Fertility drug

A medication given to women to increase their chances of becoming pregnant, containing FSH and LH.

FSH

Follicle Stimulating Hormone, a hormone involved in the maturation of eggs.

LH

Luteinizing Hormone, a hormone that works with FSH in the fertility treatment process.

IVF

In vitro fertilization, a process where eggs are collected from the mother and fertilized by sperm in a laboratory.

Success rate of fertility treatment

The likelihood of achieving pregnancy through fertility treatments, which is noted to be not high.

Multiple births

A condition that can arise from fertility treatments where more than one embryo is implanted, posing risks to the babies and mother.

Contraception

Methods used to control fertility and prevent pregnancy.

Hormonal contraceptives

Birth control methods that contain hormones to inhibit FSH production, preventing egg maturation.

Non-hormonal contraceptives

Methods that do not involve hormones, such as barrier methods and surgical sterilization.

Barrier methods

Contraceptive methods like condoms and diaphragms that prevent sperm from reaching an egg.

Spermicidal agents

Substances that kill or disable sperm to prevent fertilization.

Abstinence

Choosing not to engage in sexual intercourse during the time an egg may be present.

Ecosystem

The interaction of a community of living organisms with the non-living parts of their environment.

Adaptation

Features that enable organisms to survive in their natural environment.

Community

A group of species that live in the same place.

Interdependence

The reliance of each species in a community on other species for resources such as food and shelter.

Stable community

A community where all biotic and abiotic factors are in balance, and population sizes remain constant.

Abiotic factors

Non-living components of the environment that affect living organisms, such as light intensity and temperature.

Biotic factors

Living components of the environment that affect organisms, including availability of food and presence of predators.

Food chain

A linear sequence showing feeding relationships, starting with a producer.

Producers

Organisms that synthesize molecules, typically green plants or algae that make glucose through photosynthesis.

Primary consumers

Organisms that eat producers in a food chain.

Secondary consumers

Organisms that eat primary consumers in a food chain.

Tertiary consumers

Organisms that eat secondary consumers in a food chain.

Environmental changes

Alterations in abiotic factors that affect the distribution of species in an ecosystem.

Carbon Cycle

Carbon moves from the atmosphere into organisms through photosynthesis and is released back to the atmosphere through respiration.

Respiration by microorganisms

When living things die and decay, microorganisms (bacteria and fungi) break chemicals down, returning carbon dioxide to the atmosphere and mineral ions to the soil.

Water Cycle

Rain provides fresh water for plants and animals on land, which drains into the sea through rivers, with continuous evaporation and precipitation of water.

Biodiversity

The variety of all the different species of organisms on earth, or within an ecosystem.

Global warming

The increase in global temperatures due to elevated levels of carbon dioxide and methane in the atmosphere.

High biodiversity

Good for the stability of ecosystems, reducing the dependence of species on one another for food and shelter.

Human activities reducing biodiversity

Human actions have led to increased pollution, habitat loss, food loss, and the spread of disease, reducing biodiversity.

Pollution in water

Caused by sewage, fertiliser, or toxic chemicals, leading to reduced biodiversity.

Pollution in air

Caused by smoke and acidic gases, leading to reduced biodiversity.

Pollution on land

Caused by landfill and toxic chemicals, leading to reduced biodiversity.

Land use

Humans use land for building, quarrying, farming, and dumping waste, which reduces the land available for animals and plants.

Breeding programmes

Initiatives aimed at protecting endangered species to help stop the decline in biodiversity.

Rare habitats protection

Efforts to protect and regenerate rare habitats to support biodiversity.

Compost

Increases food production and is a result of decaying organic matter.

Deforestation

The reduction in size of forests, primarily a problem in tropical areas, often for agricultural purposes.

Genetic variation

Differences in the characteristics of individuals in a population, caused by genetic and environmental factors.

Gene

A short section of DNA on a chromosome that codes for a sequence of amino acids, making a specific protein.

Genome

The entire genetic material of an organism.

Eukaryotic cell

A cell in which genetic material is found in the nucleus and contained in chromosomes.

Non-coding DNA

Parts of DNA that do not code for proteins but can switch genes on and off, affecting gene expression.

Mitosis

A process of cell division in body cells where the number of chromosomes remains the same.

Cell cycle stage 1

The cell grows, the DNA replicates to form two copies of each chromosome, and new mitochondria and ribosomes are made.

Uses of cell division by mitosis

Growth, Repair of tissues, Asexual reproduction.

Meiosis

Happens in reproductive organs: ovaries and testes. In meiosis, the number of chromosomes is halved.

Fertilisation

The full number of chromosomes is restored when the male and female gametes fuse.

Cell cycle stage 2

Meiosis: the chromosomes are pulled to opposite poles twice. Male and female gametes join.

Cell cycle stage 3

The cytoplasm and cell membranes divide twice. There are now four genetically different gametes (sex cells).

Asexual reproduction

Involves only one parent.

Sexual reproduction

Involves the fusion of male and female gametes.

Polydactyly

Causes extra fingers or toes.

Allele

Version of a gene e.g. blue eyes, brown eyes.

Cystic fibrosis

A disorder of cell membranes, causing mucus to block narrow passages such as the bronchioles.

Genotype

The alleles that an organism has e.g. AA, Aa or aa.

Phenotype

The characteristics that an organism has e.g. tall, dimples, red flowers.

Dominant allele

A dominant allele is always expressed, even if there is only one copy.

Recessive allele

Two copies of a recessive allele are required for it to be expressed.

Homozygous

Two of the same alleles for a gene e.g. AA or aa.

Heterozygous

Two different alleles for a gene e.g. Aa.

Punnett Squares

A method to predict the probability of offspring genotypes.

Chance of offspring being pp

1 in 4 or 25%.

Natural Selection

Evolution is a change in the inherited characteristics of a population over time through a process of natural selection.

Mutation

Causes variation in the population.

Fossils

Evidence for natural selection; remains of organisms from millions of years ago, found in rocks.

Problems with the fossil record

Insufficient evidence for theories of evolution.

Extinction

The process through which species cease to exist, often due to factors like new diseases, new predators, climate change, habitat loss, or catastrophic events.

Antibiotic resistant bacteria

Bacteria that have evolved to survive exposure to antibiotics, serving as evidence for natural selection.

Selective breeding

The process where humans breed plants and animals for particular characteristics.

Genetic engineering

The technological alteration of an organism's genome by transferring genes from one organism to another.

Binomial name

The two-part scientific naming system for organisms, consisting of the genus and species.

Domains

The three new groups proposed by Carl Woese: Archaea, Bacteria, and Eukaryota.

Archaea

Bacteria living in extreme environments.