B3: Organism Level Systems - The Nervous and Endocrine Systems

Comprehensive vocabulary flashcards covering the Year 10 Biology module on Organism Level Systems, focusing on neurones, reflex actions, the endocrine system, the menstrual cycle, contraception, and blood glucose regulation.

Neurone

A specialised cell in the nervous system adapted to carry electrical impulses from one part of the body to another.

Myelin Sheath

A fatty layer insulating the axon of a neurone that speeds up electrical impulse transmission via saltatory conduction.

Dendrites

Branched projections of a neurone that connect multiple neurones together to receive and transmit impulses.

Stimulus

A detectable change in the internal or external environment, such as light, temperature, sound, or pressure.

Receptor

A specialised cell located in a sense organ (such as the eyes, ears, skin, nose, or tongue) that detects a specific stimulus.

Central Nervous System (CNS)

The coordinator of the nervous system, composed of the brain and spinal cord, which coordinates responses to stimuli.

Effector

A muscle or gland that brings about a response when stimulated by motor neurones.

Synapse

A microscopic gap between two neurones across which chemical messengers diffuse to transmit an impulse.

Neurotransmitter

A chemical messenger released into a synapse that diffuses across the gap and binds to receptors on the next neurone.

Coordinated Response

A voluntary, relatively slow nervous pathway involving conscious processing by the central nervous system (CNS).

Reflex Action

A rapid, involuntary, and protective response to a stimulus that travels via a relay neurone in the spinal cord without conscious brain involvement.

Relay Neurone

A type of neurone located in the spinal cord that connects sensory neurones directly to motor neurones during a reflex action.

Homeostasis

The maintenance of a constant internal environment, such as regulating body temperature, water balance, and blood glucose levels.

Hormones

Chemical messengers secreted directly into the bloodstream by endocrine glands that travel to target cells to produce slow, long-lasting effects.

Target Cells

Specific cells bearing matching receptors to which specific hormones bind to trigger an action or physiological change.

Menstrual Cycle

A recurring reproductive cycle in human females lasting an average of $28\text{ days}$ that coordinates egg release and the thickening of the uterine lining.

Follicle Stimulating Hormone (FSH)

A pituitary hormone with an initial peak between days $1$ and $5$ of the menstrual cycle that stimulates the maturation of an egg.

Oestrogen

A hormone peaking between days $5$ and $13$ of the menstrual cycle that stimulates the thickening of the uterine lining and inhibits FSH.

Luteinising Hormone (LH)

A pituitary hormone that surges to a sharp peak on day $14$ of the menstrual cycle to stimulate ovulation.

Progesterone

A hormone produced after ovulation, peaking between days $15$ and $28$, that maintains the uterine lining for potential pregnancy.

Combined Oral Contraceptive

A daily hormonal contraceptive pill containing oestrogen and progesterone that inhibits FSH and LH, prevents ovulation, and thickens cervical mucus.

Intrauterine Device (IUD)

A T-shaped copper device inserted into the uterus that prevents sperm survival and embryo implantation, providing $99\%$ effective non-hormonal contraception.

Sterilisation

A permanent surgical method of contraception, such as a vasectomy in males or blocking and cutting the fallopian tubes in females.

Insulin

A hormone produced by the pancreas that reduces blood glucose levels by causing cells to absorb glucose and the liver to convert it to glycogen.

Glycogen

An insoluble storage polymer of glucose formed in the liver and muscle cells under the action of insulin.

Type 1 Diabetes

A hereditary disorder wherein the pancreas produces little or no insulin, leading to uncontrolled high blood glucose that requires regular insulin injections.

Type 2 Diabetes

A metabolic condition where target body and liver cells become resistant to insulin, strongly associated with risk factors like obesity and older age.