Yr 9 T4 — Science

Homeostasis

The self-regulating process by which a biological system maintains a stable internal environment while adjusting to changing external conditions

Enzymes

A biological catalyst, almost always a protein, that speeds up specific chemical reactions occurring in living cells without being consumed or destroyed in the process

Equilibrium

A state of balance where opposing forces or influences are equal and result in no net change over time

Negative feedback

The self-regulating control mechanism which triggers a response that reverses or weakens the initial change (restoring equilibrium) after a change in a physiological variable — the body acts against the stimulus

Positive feedback

A physiological process by which the bodies amplifies or increases an initial change until an event is complete, like a thermostat heating a room to a certain temperature — the body amplifies the stimulus

Nervous system

A complex biological network that coordinates actions and sensory information by transmitting electrochemical signals throughout the body

Central nervous system (CNS)

The central nervous system is the primary processing and command centre of the body’s nervous system, containing the brain and the spinal cord

Peripheral nervous system (PNS)

The network of nerves and ganglia located outside of the brain and spinal cord, connecting the CNS to the rest of the body

Neuron

A neuron is an electrically excitable cell in the nervous system which receives, processes, and transmits information through electrical and chemical signals

Ganglia

A cluster of neuronal cell bodies (somata) located outside the CNS which functions as a relay station or connection point for nerve signals

Nerves

A cord-like bundle of nerve fibres located in the peripheral nervous system that transmits electrical and chemical messages between the central nervous system and the rest of the body

Dendrite

The branched extensions of a nerve cell that receives electrochemical signals from other neutrons and passes them toward cell body

Cell body (soma)

The central part of a cell that houses the nucleus and main cellular organelles in a neuron

Axon

A long projection of a nerve ell that conducts electrical impulses (action potentials) away from the cell body and instead towards other neurons, muscles, or glands

Axon terminal

The bulbous swelling at the end of an axon branch which converts electrical signals into chemical messages

Synapse

The microscopic gap between neurons where a neuron communicates with another cell (not necessarily a neuron)

Sensory neurons

A specialised nerve cell that converts external and internal stimuli into electrical impulses before being transmitted to the CNS

Motor neurons

A specialised nerve cell which transmits electrical and chemical signals form the CNS to the PNS

Autonomic Nervous System (ANS)

A division of the PNS that regulates involuntary bodily functions

Somatic Nervous System (SNS)

Manages muscle movements and carries sensory information to and from the CNS

Sympathetic Nervous System (SNS)

A division of the ANS that regulates involuntary bodily functions like triggering the body’s “flight or flight” response

Parasympathetic Nervous System (PNS)

A division of the ANS that manages the body’s “rest and digest” and “feed and breed” functions during calm states, working in opposition to the sympathetic nervous system

Gland

group of cells that produces and releases chemicals

Metabolism

the network of chemical processes that turn consumed food and drink into energy

Exocrine glands

an organ or unit of cells that produces and secretes substances through ducts onto an internal or external body surface

Endocrine system

A network of glands and organs that produce and secrete hormones directly into the bloodstream to maintain homeostasis

Hormones

chemical messengers produced by specialised glands that travel through the bloodstream to maintain homeostasis

Adrenaline

a hormone produced by the adrenal glands that triggers the ‘fight or flight’ response

Estrogen

a group of sex hormones that regulate the development of female reproductive characteristics

Testosterone

a primary steroid sex hormone that triggers male reproductive organ formation

Set point

The target physiological value that the body tries to maintain

Range

The restricted set of values around a target set point where a physiological condition stays healthy and stable

Variable

Any specific physical or chemical condition inside the body that is monitored and kept within a narrow, stable range

Pituitary gland

An endocrine gland located at the base of the brain that produces and secretes hormones that control growth, metabolism, reproduction, stress response, water balance, and childbirth

Thyroid gland

An endocrine gland that produces and secretes hormones which control metabolism

Adrenal glands

Endocrine glands that produces and secretes hormones which control the body’s stress response, blood pressure, metabolism, and salt-and water- balance

Pancreas

An endocrine and exocrine gland which produces and secretes hormones like insulin and glucagon which control blood sugar levels and enzymes lick amylase and protease to digest food

Ovaries

Endocrine glans that control ovulation, produces and secretes the female sex hormones estrogen and progesterone which control the menstrual cycle, puberty, pregnancy, and secondary sex characteristics

Testes

Endocrine glands which control sperm production, produces and secretes hormones

Thermoreceptors

Specialised sensory nerve endings that detect changes in temperature

Chemoreceptors

Specialised sensory cells that detect changes in the chemical composition of their internal and external environment

Mechanoreceptors

Specialised sensory receptors that detect physical forces

Photoreceptors

Specialised sensory neurons that detect light

Nociceptors

Specialised sensory nerve endings that detect damaging or potentially damaging stimuli

Stimulus-Response model

A pathway that explains how living organisms detect and respond to changes in their internal or external environment

Stimulus

Any detectable physical or chemical change in an organism’s internal or external environment that triggers a physiological or behavioural response

Receptor

A specialised sensory cell, protein, or tissue that detects a stimulus in an organism’s internal or external environment

Control Centre

The part of the stimulus-response model that receives and processes signals from sensory receptors by comparing the input against an optimal range or set point before directing an appropriate response from an effector

Effector

A muscle, gland, or cell that receives a signal from the control centre to produce a response to an environmental stimulus

Response

The reaction produced by an organism as a result to a detected stimulus

Insulin

A hormone produced by the pancreas that moves glucose from the bloodstream into cells, lowering blood sugar levels

Glucagon

A natural peptide hormone produced by cells in the pancreas that raises blood glucose levels by signalling the liver to break down stored glycogen into glucose

Blood Glucose Levels

The concentration of glucose present in the bloodstream

Sexual reproduction

A biological process by which two haploid gametes fuse during fertilisation to create a diploid zygote

(Haploid) Gamete

An organism’s reproductive cells that fuse during fertilisation to form a zygote

Variation

The biological differences in traits and DNA between individuals belonging to the same species

(Diploid) Zygote

The eukaryotic cell formed by fertilisation between two gametes

Fertilisation

The biological process where the nucleus of a male gamete and the nucleus of a female gamete fuse together

Motile

The ability of an organism or cell to move independently and spontaneously using its own metabolic energy

Polyspermy

The fertilisation of a single egg cell by more than one sperm

Monospermy

The fertilisation of a single egg cell by only one sperm

Fallopian tube (Uterine tube; oviduct)

Ducts in the female reproductive system that connect the ovaries to the uterus, allowing it to push the embryo into the uterus. The fallopian tube is where fertilisation occurs

Embryo

The early stage of development of a multicellular organism which occurs immediately after fertilisation

Cilia

Microscopic ‘hairs’ that line the inside of the fallopian tubes to guide the embryo towards the uterus

Uterus

Hollow muscular organ which receives a fertilised embryo and nourishes the developing fetus. If pregnancy does not occur, the inner lining thickens and sheds each month

Fimbriae

Finger-like projections located at the ends of the fallopian tubes nearest to the ovaries which catch the ovum and guide it into the fallopian tubes

Ovary

A paired primary female reproductive organ that produces and releases egg cells, and produces hormones such as estrogen and progesterone

Cervix

The part of the uterus that connects the main body of the womb to the vagina. It allows menstrual blood and tissue to pass. During pregnancy, it creates a mucus plug that protects the baby until labor, when it effaces and dilates

Cervical canal

The cervical canal connects the uterus to the vagina, allowing menstrual blood to flow, cervical mucus to be secreted, and protects against bacteria and germs

Vagina

A canal that connects the cervix to the outside of the body. It receives the penis (and sperm) during sexual reproduction and allows a baby to pass during childbirth. It also serves as the exit canal for menstrual blood, and it blocks harmful microorganisms by maintaining a natural acidic environment

Vasa deferentia (Ductus deferens; sperm duct)

Long, muscular tubes in the male reproductive system which propels stored mature sperm during ejaculation

Bladder

An organ which stores urine before it leaves the body and is not a part of the male reproductive system

Seminal vesicle(s)

A pair of small glands that produce most of the liquid volume of semen, which gives sperm energy to move and protects sperm from the acidic environment of the female reproductive system

Prostate gland

A walnut-sized organ which produces a fluid to nourish sperm cells and keep them active

Penis

The external copulatory and urinary organ which delivers sperm into the vagina during sexual reproduction and allows urine to exit the body

Urethra

A narrow tube which acts as a shared passageway for urine to leave the bladder and semen do exit during ejaculation

Epididymis

A tightly coiled tube attached to the back of each testicle where sperm matures and are stored until ejaculation

Testis (testes)

Male reproductive glands which produce sperm and male sex hormones, primarily testosterone

Scrotum

The loose external pouch directly beneath the penis which houses and protects the testes and epididymides by keeping the testes ~2-3ºC cooler than the rest of the body, which is essential for healthy sperm production

Anther

The male reproductive part of a flowering plant which produces and stores pollen grains

Stigma

The sticky tip of the pistil which receives pollen and triggers germination in the pollen grain

Filament

The thread-like stalk that supports the anther by lifting and holding the anther in an accessible position for pollinators to pick up pollen

Style

A long stalk which connects the stigma to the ovary, making up part of the pistil

Petal

A leaf, usually brightly coloured, patterned, or scented to lure animals to the flower

Ovary (flowering plants)

The enlarged lower part of the pistil that holds the unfertilised eggs

Ovule (flowering plants)

A small structure located inside the ovary

Ovum (flowering plants)

The female gamete which fuses with the male sperm cell during fertilisation, forming a plant embryo

Pollen

A fine powder containing the male gametes of flowering plants

Dehiscence

The natural splitting open of a mature plant structure to release its contents

Stamen

The male reproductive organ of a flowering plant which produces and released pollen

Pistil

The female reproductive organ of a flowering plant which receives pollen, fertilises female gametes, and turning into seeds and fruit

Binary fission

A form of asexual reproduction in which a single organism creates an identical copy of its genetic material and splits into two identical daughter cells

Budding

A form of asexual reproduction in which a new organism develops as an outgrowth or ‘bud’ on the body of a single parent organism by receiving an identical copy of the parent’s genetic material before detaching from the parent upon maturation

Fragmentation

A form of asexual reproduction in which a parent organism breaks into two or more fragments, and each piece regenerates into a complete and genetically identical organism

Spore formation

A form of asexual reproduction in which a single parent organism produces spores which grow into a separate organism with identical genetics

Vegetative propagation

A form of sexual reproduction in plants where an independent but genetically identical plant grows from a vegetative part of the plant (e.g. stem, root, leaf) instead of from a seed or spore

Dispersal

The movement of genetically identical propagules away from the parent organism to a new location where they grow and mature into genetically identical organisms

Runners

Horizontal stems that grow along the surface of the ground

Hydra

A fresh-water organism which reproduces primarily through budding

Daughter cells

The individual and genetically identical cells formed when a single parent cell divides