Positive feedback system
A disturbance triggers processes that change the body's condition such that the disturbances are intensified or prolonged.
Unstable and non-regulatory
Short-lived and produces radical change:
- Mammalian birth
- Swallowing or vomiting
- Generation of nerve impulse
Skin & Temperature Control
Skin
- Forms a continuous layer over the entire body
- Protects the underlying tissues and organs from mechanical injury
- Minimizes the loss of water through body
- Prevents entry of harmful bacteria and fungi
- Consisting mainly of Outer Epidermis & Inner Dermis
Outer Epidermis
Malpighian Layer
- Innermost layer of the epidermis
- Cells contain melanin which helps to absorb UV light
- Actively dividing cells that push the new cells towards the outer layers of the skin
Granular Layer
- Cells which are produced by the Malpighian layer move into the Granular layer and die.
Cornified Layer
- Consists of dead cells
- Keep bacteria out
- Reduces evaporation of water from the skin
Inner Dermis
Layer of connective tissue containing:
- Capillaries
- Sensory nerve endings
- Lymphatics
- Sweat glands
- Hair follicles
Blood capillaries
- Remove away carbon dioxide and nitrogenous wastes
- Brings oxygen and nutrients to the skin
- Presence of capillary loops close to the surface of the skin which are important in temperature regulation
- Process is mainly diffusion
Sweat Gland
- Coiled tube deep in the dermis
- When temperature is too high, it takes up water from the surrounding blood capillaries around it
- Water collects in the gland, travels up the sweat duct, comes out of the pore in the epidermis
- The body is cooled as evaporation of the perspiration takes away latent heat from the skin
- Sweat consists of water, dissolved salts and tiny amounts of urea
Hair Follicle
- Deep pit lined with Granular and Malpighian cells
- Malpighian cells keep dividing and add on to the base of the hair, causing it to grow
- It is attached to the errector muscle which raises the hair away from the skin surface when contracting
- A thicker layer of air is trapped and this is an insulating layer
- Goose pimples are also produced when the hair errector muscles contract
Sebaceous Gland
- Produces an oily substance, sebum, which lubricates the hair and keeps the skin supple
- During puberty, it may over produce sebum due to hormonal changes, causing the sebum to clog up the pore of the skin
- When bacteria incubate in the sebum deposits, boil and acne occur
Adipose Tissue
- Fat tissue underneath the dermis
- Serves as an insulating layer and reduces heat loss from the body
Brief overview of Homeostasis
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