Grade 12 Life Sciences: Responding to the Environment, Human Reproduction, and Homeostasis

High-yield vocabulary items and definitions covering human nervous response, reproduction, homeostasis, and plant growth based on Grade 12 Life Sciences revision materials.

Cerebrum

The part of the brain responsible for voluntary actions, intelligence, memory and interpretation of sensory information.

Cerebellum

The part of the brain responsible for balance, posture and coordination of voluntary muscle movements.

Corpus callosum

The part of the brain that connects the left and right cerebral hemispheres.

Medulla oblongata

The part of the brain that controls involuntary activities such as breathing and heartbeat.

Dendrites

Neuronal structures that receive nerve impulses.

Cell body

The part of a neuron that contains the nucleus and controls the activities of the neuron.

Axon

The structural part of a neuron that carries nerve impulses away from the cell body.

Myelin sheath

An insulating layer on the axon that increases the speed of impulse transmission.

Sensory neuron

A neuron that carries impulses from a receptor to the CNS (Central Nervous System).

Motor neuron

A neuron that carries impulses from the CNS to an effector.

Reflex arc

The nerve pathway involved in a reflex action, following the order: Receptor $\rightarrow$ sensory neuron $\rightarrow$ relay neuron $\rightarrow$ motor neuron $\rightarrow$ effector.

Synapse

The junction where an impulse reaches the end of the first neuron, neurotransmitters are released, cross the synaptic gap, and bind to receptors on the next neuron to generate a new impulse.

Cornea

The part of the eye that refracts light entering the eye.

Lens

The eye structure that further refracts/focuses light onto the retina.

Iris

The part of the eye that controls the amount of light entering the eye.

Retina

The layer of the eye containing photoreceptors that detect light.

Optic nerve

The nerve that carries impulses from the retina to the brain.

Rods

Photoreceptors that work well in dim light and do not detect colour.

Cones

Photoreceptors that require brighter light, detect colour, and provide more detailed vision.

Cochlea

The part of the ear containing the organ of Corti, where sound vibrations are converted into nerve impulses.

Organ of Corti

A structure in the cochlea whose sensory receptors convert sound vibrations into nerve impulses.

Semicircular canals

Structures in the ear that detect rotational/angular movement of the head and help maintain balance.

Sympathetic nervous system

The part of the autonomic nervous system that triggers the fight-or-flight response, increasing heart rate, breathing, and blood glucose, while dilating pupils.

Parasympathetic nervous system

The part of the autonomic nervous system that returns the body to its normal resting state after an emergency.

Testes

Male reproductive organs that produce sperm and testosterone.

Scrotum

The sac that keeps the testes at a temperature slightly lower than normal body temperature for sperm production.

Epididymis

The site where sperm are stored and allowed to mature.

Vas deferens

The tube that transports sperm from the epididymis toward the urethra.

Seminal vesicles

Glands that add nutrient-rich fluid to semen.

Prostate gland

A gland that adds fluid to semen and supports sperm function.

Urethra

The passage through which semen and urine leave the body.

Acrosome

The head part of the sperm containing enzymes that help penetrate the ovum.

Ovary

The female reproductive organ that produces ova and female sex hormones.

Oviduct (Fallopian tube)

The structure that transports the ovum and is the usual site of fertilisation.

Endometrium

The lining of the uterus where implantation occurs.

FSH (Follicle-Stimulating Hormone)

Hormone that stimulates development/maturation of ovarian follicles and promotes oestrogen secretion.

LH (Luteinising Hormone)

Hormone whose sudden increase causes ovulation and promotes the formation of the corpus luteum.

Progesterone

Hormone that maintains the thickened endometrium and prepares it for implantation.

Implantation

The attachment and embedding of the developing embryo into the endometrium.

Placenta

A selective barrier between maternal and foetal blood that allows exchange of oxygen, nutrients, and waste removal.

Insulin

A hormone produced by the pancreas that lowers blood glucose by promoting glucose uptake by cells and conversion into glycogen.

Glucagon

A hormone secreted by the pancreas that stimulates the conversion of glycogen into glucose when blood glucose falls below normal.

ADH (Antidiuretic Hormone)

Hormone that increases water reabsorption by the kidneys, reducing water loss in urine.

Thyroxine

Hormone that regulates the body's metabolic rate.

Adrenaline

The hormone associated with fight-or-flight, which can increase heart rate, breathing rate, and blood glucose.

Phototropism

Growth of a plant in response to light, controlled by the hormone auxin.

Gravitropism

Growth of a plant in response to gravity.