Biology

• The nucleus is the control center of the cell, containing the genetic material and regulating cell activities.
• The cell membrane is a selectively permeable barrier that surrounds the cell and regulates the movement of substances in and out of the cell.
• Mitochondria are responsible for producing energy in the form of ATP through cellular respiration.
• The midpiece of a sperm cell contains mitochondria, which provide energy for the sperm to swim.
• The head of a sperm cell contains the genetic material (DNA) necessary for fertilization.
• The tail of a sperm cell, also known as the flagellum, propels the sperm forward through the female reproductive tract.
• The egg cell, also known as the ovum, is the female reproductive cell in animals.
• The egg cell is produced in the ovaries and is released during ovulation.
• The egg cell is typically larger than sperm cells and contains a nucleus, cytoplasm, and a protective outer layer called the zona pellucida.
• Ciliated epithelial cells are specialized cells found in the respiratory tract and other organs.
• Ciliated epithelial cells play a crucial role in protecting the respiratory system from infections and maintaining its normal functioning.
• Cilia are composed of microtubules and are capable of rhythmic beating motions.
• These cells have hair-like structures called cilia on their surface, which help in moving mucus and foreign particles out of the body.
• Cilia are slender, hair-like structures that extend from the surface of ciliated epithelial cells.
• The coordinated movement of cilia helps in moving mucus, dust, and other foreign particles out of the respiratory tract and other organs.
• Prokaryote:

  A single-celled organism that doesn’t have a nucleus
• Eukaryote:

  Complex cell/organism that has a nucleus
• The menstrual cycle is a monthly sequence of events that occurs in the female body. An egg is released and the body prepares the uterus (womb) in case the egg is fertilised
• menstrual cycle:

  • Day 1 : Menstruation starts, the uterus lining breaks down and is released

  • Day 4 - 14 : The uterus lining is repaired until it becomes a think spongy layer of full blood vessels. Ready for a fertilised egg to implant there

  • Day 14 : An egg develops and is released from the ovary (ovulation)

  • Day 25 - 28 : If no fertilised egg has landed on the uterus wall by day 28, the spongy lining breaks down again and the cycle starts again
• The menstrual cycle is controlled by 4 hormones : FSH, oestrogen, LH and progesterone
• FSH (follicle-stimulating hormone)

  • Released by the pituitary gland

  • Causes follicle ( egg and surrounding cells) to mature in one of the ovaries

  • stimulates oestrogen production
• Oestrogen

  • Released by the ovaries

  • Causes the lining of the uterus to thicken and grow

  • A high level stimulates a LH surge (a rapid increase)
• LH (luteinising hormone)

  • Released by the pituitary gland

  •The LH surge stimulates ovulation at day 14, the follicle ruptures and the egg is released

  •Stimulates the remains of the follicle to develop into a structure called a corpus luteum- which secretes progesterone
• Progesterone

  • Released by corpus luteum after ovulation

  • Maintains the lining of the uterus

  • Inhibits the release if FSH and LH

  •When the level of progesterone falls, and there’s a low oestrogen level, the uterus lining breaks down

  •A low progesterone level allow FSH to increase and the whole cycle starts again
• If a fertilised egg implants in the uterus (woman becomes pregnant) then the level of progesterone will stay high to maintain the uterus lining during pregnancy
• Hormones are chemicals released directly into the blood. They are carried to other parts of the body but only affect particular cells in particular organs (target organs).
• Hormones control things in organs that need constant adjustment
• Hormones are produced in (and secreted by) various glands called endocrine glands. These glands make up the endocrine system
• The pituitary gland produces many hormones that regulate body conditions.
• Ovaries produces oestrogen which is involved in the menstrual cycle
• Testies produce testosterone which controls puberty and sperm production in males
• Thyroid gland produces thyroxine which is involved in regulating things like the rate of metabolism, heart rate and temperature
• Adrenal glands produce adrenaline which is used to prepare your body for 'fight or flight' response
• The pancreas this produces insulin which is used to regulate the blood glucose levels
• Neurones: Very fast action, act for a very short time and act on a very precise area
• Hormones: Slower action, act for a long time, act in a more general way
• Adrenaline is a hormone released by the adrenal gland
• Adrenaline prepares the body for 'fight or flight'. It does this by activating processes that increase the supply of oxygen and glucose to cells
• When your brain detects a stressful situation, it sends nervous impulses to the adrenal glands, which respond by secreting adrenaline. This gets the body ready for action
• The body can control the levels of hormones in the blood by using negative feedback systems. When the body detects taht the level of substance has gone above or below the normal level, it triggers a response to bring the level back to normal again.