Organism level systems Study Guide

Contraception aims to prevent pregnancy through various mechanisms. Hormonal methods typically involve synthetic versions of hormones already present in the female body, primarily oestrogen and progesterone. These hormones work by mimicking the signals of pregnancy, which prevents ovulation (the release of an egg from the ovary). They can also thicken the cervical mucus, making it difficult for sperm to pass through, and thin the lining of the uterus, making it less receptive to a fertilised egg. Examples include the combined pill, progesterone-only pill, contraceptive patch, injection, and implant. Each of these methods has different durations of effectiveness and routes of administration, but their core hormonal action is designed to disrupt the natural menstrual cycle and prevent fertilisation or implantation.

Non-hormonal contraception does not interfere with the body's natural hormone levels. These methods often act as physical barriers to prevent sperm from reaching and fertilising an egg, or they may involve disrupting sperm function. Examples include condoms, diaphragms, caps, and intrauterine devices (IUDs). Condoms are barrier methods that also offer protection against sexually transmitted infections (STIs). IUDs are small devices inserted into the uterus; copper IUDs prevent sperm survival and fertilisation, while some IUDs release progesterone, making them a hybrid method. Each contraceptive method has advantages and disadvantages related to effectiveness, ease of use, potential side effects, and protection against STIs, making the choice a personal one based on individual needs and health considerations.

The brain is the control center of the body, part of the central nervous system, and it coordinates all voluntary and many involuntary actions. It is a highly complex organ, broadly divided into several key regions, each with specific functions. The cerebrum is the largest part of the brain and is responsible for higher-level functions such as conscious thought, memory, language, and voluntary movement. It is divided into two hemispheres, and its outer layer, the cerebral cortex, is highly folded to increase its surface area, allowing for a greater capacity for information processing. The cerebellum, located at the back of the brain beneath the cerebrum, plays a crucial role in coordinating movement, balance, and posture. It helps to make movements smooth and precise. The medulla oblongata, often simply called the medulla, forms the brainstem along with the pons and midbrain. The medulla is vital for regulating essential involuntary bodily functions such as breathing, heart rate, and blood pressure. Damage to this area can be life-threatening. Together, these main parts work in a coordinated way to allow us to interact with our environment, learn, remember, and maintain our basic biological processes. Understanding the distinct roles of these regions helps us to appreciate the brain's remarkable ability to integrate diverse sensory information and generate appropriate responses.