по Leung Mya 8 лет назад
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Neurons in the central nervous system don't regenerate easily. Some neurons in the peripheral nervous system regrow to repair a very small gap that is only a few millimetres apart between severed nerves.
Axons of limited neurons are covered by myelin.
Myelin acts like insulation on an electrical wire.
Prevents electrical impulses from passing to the wrong neuron.
Conducts electrical signals from one area of the body to another.
An estimation of 100 billion neurons in the brain
Surrounded by cerebrospinal fluid.
-Cushions the brain and spinal cord from injury -Transports chemicals and removes waste produced by the brain
Spine guards protect the spinal cord.
Skull protects the brain.
-Dense connective tissue mainly found in the ear, nose, esophagus, disks between vertebrae, and joints -Made up of special cells in a matrix of collagen fibres -Provides strong, flexible, low-friction support for bones and other tissues -prevents damage to the ends of bones
-Tough, elastic, connective tissues that hold bones together at the joints -Made up of mostly long fibres of collagen
-Hard and dense -Consists of bone cells within matrix of minerals (mainly Calcium and Phosphorus) and collagen fibres -Canals inside bones have nerves + blood vessels -Small percentage of bone tissue is living -Stores calcium and other minerals that are needed by the organism
Muscles can pull but not push.
Cardiac Muscle
Only in the heart, another example of a smooth muscle (involuntary)
Smooth Muscles (involuntary)
Involuntary muscles expand and contract without a conscious thought. you aren't able to control these muscles.
Skeletal Muscle (voluntary)
Always work in opposing pairs or groups
Voluntary muscles allow you to control them with a conscious thought.
Bloodstream
Bronchi (singular: bronchus)
Alveoli (singular: alveolus)
Are tiny blood vessels with very thin walls that allow substances to diffuse between blood and other body fluids.
Carry blood toward the heart (under lower pressure + walls of veins aren't as thick)
Carry blood away from the heart (under greater pressure than blood in other vessels)
-Special tissue only found in the heart -All cardiac muscles in the heart contract at the same time -Pumps blood around the body
-Protein rich liquid -Carries blood cells through the circulatory system -Makes up over 50% of the blood's volume
-Tiny cells that help in the case of blood clotting -Makes up less than 1% of the volume of blood
-Recognizes + destroys invading bacteria -Less than 1% of the blood's volume -Only blood cells to have a nucleus
-Most plentiful -Makes up about 50% of the blood's volume -Has a protein called hemoglobin -Hemoglobin allows red blood cells to transport oxygen through the body -Hemoglobin makes cells red
Stores bile that is created by the liver.
Produces insulin. Breaks down the sugar that is consumed. Regulates our glucose level.
Produces bile. A liquid that breaks down fats in our food
The Stomach
The Intestine
Small Intestine
Absorbs nutrients and minerals from food.
Large Intestine
Absorbs water from remaining leftover food
Between the stomach + anus. Produces mucus.
