Key Concepts in Human Biology and Physiology

By Rene Fester Kratz

Part of Biology For Dummies Cheat Sheet

The study of biology includes the study of human beings. The biological functions of humans are similar to those of many other animals. Like other animals, humans need to acquire oxygen and energy in order to survive. Here is a brief summary of key human biological concepts:

  • Organisms are made of organ systems, which are made of organs, which are made of tissues, which are made of cells, which are made of molecules, which are made of atoms.

  • Homeostasis is the balance, or equilibrium, of the body. Regulation of all the body’s systems seeks to keep the body in homeostasis.

  • The heart is a muscular pump. Contractions by the heart push blood through the circulatory system.

  • Within the circulatory system, blood travels in arteries to carry oxygen from the lungs to the tissues and returns through veins to carry carbon dioxide from the tissues to the lungs. Blood also carries nutrients from the digestive system to the cells of the body and removes wastes from the cells.

  • Exchange of the respiratory gases, oxygen and carbon dioxide, occurs in the lungs.

  • Digestion involves the mechanical and chemical breakdown of food molecules into their smallest subunits. Digestion begins in the mouth and continues in the stomach and small intestine.

  • Absorption of nutrients in the digestive system occurs through the cells of the small intestine.

  • Glands are organs in the endocrine system that secrete hormones. Hormones are chemical messengers that can alter the behavior of target cells.

  • The nervous system consists of two main systems, the central nervous system (CNS) and the peripheral nervous system. The CNS is made up of the brain and spinal cord and sends out instructions. The peripheral nervous system contains the nerves that send the messages from the CNS to the rest of the body.

  • The muscular and skeletal systems work together to allow movement. The muscles contain fibers that can contract, while the skeleton provides support and structures for muscles to pull against.