Review: support, movement and hormones
This lesson revisits Chapters 1 and 2 as a chain of ideas rather than a list of facts. The skeleton (206 bones in the book’s count) has an axial part, the skull, the vertebral column of 33 vertebrae and the rib cage, and an appendicular part, the girdles and limbs. Joints are fibrous, cartilaginous or synovial. A ligament joins bone to bone, and a tendon joins muscle to bone. Plants move too, by touch, sleeping movements, tendrils, pulling roots and streaming cytoplasm. Muscle contraction is a chain. A nerve impulse reaches the neuromuscular junction, calcium ions enter the nerve ending, acetylcholine crosses the gap and depolarizes the fibre, cross bridges form with the help of calcium ions and ATP and pull the actin filaments inwards, the Z-lines come closer and the sarcomere shortens. Cholinesterase then breaks the acetylcholine down. ATP is needed to detach the bridges as well, and when oxygen is short, lactic acid builds up and the muscle tires. Hormones travel in the blood from endocrine glands, and the pituitary, the master gland, controls many other glands. Many hormones work in opposite pairs: insulin lowers and glucagon raises blood glucose, and calcitonin lowers and parathormone raises blood calcium. Adrenaline prepares the body for an emergency, and thyroxine, which needs iodine, sets the metabolic rate. Whenever a hormone or a muscle problem concerns a real person, a doctor decides.
| Gland | Hormone | Target or job | Out of balance |
|---|---|---|---|
| Pituitary, anterior lobe | growth hormone | controls growth through protein making | dwarfism, gigantism (child), acromegaly (adult) |
| Thyroid | thyroxine (needs iodine) | growth and metabolic rate | goitre and other thyroid problems; a doctor decides |
| Parathyroids | parathormone | raises blood calcium | a doctor decides |
| Pancreas | insulin and glucagon | lower and raise blood glucose | too little insulin: diabetes mellitus |
| Adrenal medulla | adrenaline | prepares the body for an emergency | — |
| Adrenal cortex | aldosterone | keeps more sodium, loses extra potassium | a doctor decides |
| Bone | Part of the skeleton |
|---|---|
| Sternum | axial |
| Femur | appendicular |
| A lumbar vertebra | axial |
| Scapula | appendicular |
| A rib | axial |
| Radius | appendicular |
Make a link map, with a grown-up. On a sheet of paper write four boxes: nerve impulse, calcium, ATP and hormone. Draw arrows to show how the first three work together in a muscle, then add the box “insulin” and “glucagon” as a pair with two opposite arrows pointing at “blood glucose”. Check every arrow against Weeks 3 and 5.