Category:Humans

In human biology we look at the structure (anatomy) and function (physiology) of human beings.

Vessels and Blood

Blood is a liquid that transports substances, comprising blood cells. Blood vessels are the artery, vein and capillary, there is an important change of pressure across a capillary. Haemoglobin 'carries' oxygen in red blood cells. See Vessels and Blood

The Nervous System

Nerve cells have myelin, dedrites and nodes of ranvier. They carry action potentials (eg. in a reflex arc). Junctions between neurones are synapses, where neurotransmitter (acetylcholine, say) diffuses. See The Nervous System

Muscles

There are three types of muscle: smooth, skeletal and cardiac. They are made up of myofibrils and sarcomeres and have distinctive banding patterns. Muscle contraction involves the movement of actin and myosin proteins. See Muscles

The Lungs

Breathing is carried out by the lungs, controlled by the intercostal muscles and diaphragm. Gas exchange takes place in the alveoli where oxygen is used in respiration. Breathing is coordinated in the medulla of the brain. See The Lungs

The Kidneys

Urea is produced in the body, and (among other things) is removed in the kidneys: ultrafiltration to Bowman's capsule, along the proximal convoluted tubule. Water is removed in the loop of henle and ADH regulates water in the blood. See The Kidneys

Hormones

Hormones are secreted from glands into the blood. Oestrogen and testosterone are sex hormones that determine sex and causes changes at puberty. Adrenaline is a hormone that increases the activity of the body. See Hormones

Homeostasis

Homeostasis is maintaining a constant internal environment, it works by negative feedback. Examples of conditions controlled in the body are temperature and blood glucose - using insulin from the pancreas. See Homeostasis

The Heart

A key organ in the body, blood exits via the aorta, around the body ... which are ventricles and atria? The heartbeat is regulated by nerves (vagus and accelerans) and expands from the sino atrial node (SAN) causing systole. See The Heart

The Eye

The eye has a complex structure, it focuses light by adjusting the size of the lens with ciliary muscles (cornea also refracts light). Rods and cones on the retina detect light and send impulses to the brain via the optic nerve. See The Eye

Digestive System

The oesophagus, stomach, liver and intestines make up the digestive system. Food is moved along by peristalisis and broken down by enzymes so that nutrients can be absorbed through the villi and into the bloodstream. See Digestive System

Animal Cells

The simplistic structure of a cell is a nucleus, membrane and cytoplasm. Substances move in and out of the cell by diffusion, transport or osmosis. Cells are specialized for certain functions, such as the nerve cell (neurone). See Animal Cells

The Brain

The main part of the brain is the cerebral hemispheres, it is made up of sensory, association and motor areas, located in different areas. The autonomic nervous system deals with subconscious control such as tear production. See The Brain