Levels of Organisation - U1

Levels of Organisation

Different levels of complexity in which living matter is structured.

Atomic & mollecular level

• All matter is made up of very small elements called $atoms$
• Atoms come together to form $molecules$, which are held together by chemical bonds
• Atoms in living matter are called $bioelements$, which then form $biomolecules$
• The main bioelements in a human being is known as $CHON$ - carbon, hydrogen, oxygen and nitrogen

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Organism level

• A tissue is a $group of cells$ which all perform the same function
• Tissues are grouped into $organs$
• Organs joing together to form $organ systems$
• Organ systems form a $multicellular$ organism: the $human being$

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Cells & Organelles

Eukaryotic cells

• Plasma membrane is a $thin layer$ that $protects$ the cell and $regulates exchanges of substances$
• The nucleus is a $large spherical structure$ that contains genetic material which $organises$ the cell’s activity
• Cytoplasm is formed from a thick aqueous liquid called $cyostol$ that contains different $substances$ and $cell organelles$. It’s where $chemical reactions$ take place

• The nuclear membrane contains $nuclear pores$ that allows substances to be exchanged between the nucleus and the cytoplasm
• The nucleoplasm is made up of a thick aqueous liquid which contains DNA
• Chromatin is the $network$ of all DNA fibres and proteins, which then become $chromosomes$ when the cell divides
• The nucleolus is a spherical structure inside the nucleus where the components of $ribosomes$ are made

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Cell differentation

• All cells that make up the human body originates from a single celled called $zygote$
• The cells later become specialised to perform specific tasks
• Differentiation is the process in which the shape and structure of a cell $changes$ in order to perform a specific $function$

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Tissues

A tissue is a $group of cells$ that are $specialised$ to perform the $same function$

Epithelial tissue

• It’s made up of layers of cells packed together so closely that there is no space between them

Types:

• Covering epithelium $covers$ and $protects$ $outside surfaces$ and $internal cavities$ - mucus membranes
• Glandular epithelium $forms glands$ which are responsible for secreting substances - sweat glands

Connective tissue

• Connective tissue is made up of cells separated by fibres an intercellular substance called matrix

Types:

• Reticular connective tissue has an $extensive gel-like matrix$ that contains abundant fibres, it $fills in organs$ and the spaces between them and $forms tendons$
• Adipose tissue has a matrix with $low levels of intercellular substance$, its cells store fat as an $energy reserve$ and for $thermal insulation$, as its found under the skin
• Cartilaginous tissue has a $solid and elastic matrix$, and $covers the joints$ to prevent deterioration
• Osseous (bone) tissue has $solid and hard matrix$, since there are calcium salts present. This tissue $forms bones$
• Blood has a $liquid matrix called plasma$ which has blood cells suspended in it

Muscle tissue

• Muscle tissue is made up of $elongated cells$ that group together to $form muscle fibres$ that are able to contract and relax. It’s the tissue responsible for body movement

Types:

• Skeletal striated muscle tissue forms the muscles of the $locomotor system$ and can be $moved voluntarily$
• Cardiac striated muscle tissue forms the $walls of the heart$. It $contracts involuntarily$
• Smooth muscle tissue is $found in the walls of various organs$ like the stomach and bladder. It $contracts involuntarily$

Nervous tissue

• Nervous tissue is made up of two types of cells:

     1. Neurons, which $perceive$ & $react$ to stimuli & $control$ the body’s activity   2. Glial cells, which are found amongst neurons and $protect$ & $supply$ them with nutrients

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Organs and systems

Systems involved in nutritional functions:

• Digestive: $transforms$ food into nutrients, which are then $absorbed$ into the bloodstream
• Respiratory: $exchanges$ oxygen and carbon dioxide
• Circulatory: uses blood to $transport substances$ throughout the body
• Lymphatic: works together with the circulatory system to $transport substances$
• Excretory: $takes waste$ substances from the blood and $eliminates$ them from the body

Systems involved in the interaction function:

• Nervous: $receives information$ from the outside environment and $generate signals$, which then uses to $coordinate the body$
• Endocrine: works with the nervous system as it $generates signals$ that $induce responses$ in certain organs
• Muscular and skeletal: they make up the $locomotor system$ that’s controlled by the nervous system and $generate movement$

Systems involved in the reproduction function

• Female reproductive: $produces female gametes$ and $nurtures$ and $protects$ the embryo during its development
• Male reproductive: $produces male gametes$

Homeostasis: all the physiological processes that keep the internal environment stable

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Microscope

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