Chapter 8: Homeostasis and Excretion (eugh!) Flashcards
Homeostasis
Means ‘steady state’
Conditions inside the body are controlled, to provide a constant internal environment
The conditions that must be controlled include body temperature, water content, carbon dioxide level, and blood sugar level
What role do kidneys play?
performs two key functions
homeostasis (maintaining balance)
and excretion (removal of waste products from cell metabolism)
Internal environment
Blood along with tissue fluid (salts, glucose and other solutes)
Tissue fluid
surrounds the cells and forms a pathway for the transfer of nutrients between the blood and cells
Body temperature:
What’s the tempreture where enzymes work best?
37 degrees c
Body temperature is controlled by:
- controlling blood flow to the skin
- sweating
- shivering
Describe the parts of the urinary system…
two kidneys, each supplied by a renal artery
Blood filtered in kidneys then passes to renal vein
the urnine passes to your piss bag (also known as the bladder)…
…from the bladder it passes down to the urethra and out of your dicky-di-do…(or noo-noo)
…da wee we is controlled by da sphincter
Describe the differfent parts of a kidney…
Nephron
Urine is produced in microscopic structures in the kidney called nephrons. There are approximately 1 million nephrons in each kidney.
What are the 3 parts to the process that takes place in the kidneys?
This process can be summarised in three important steps:
1. Filtration - where lots of water, ions, urea and sugar are squeezed from the blood into the tubules.
2. Selective reabsorption – the useful substances (ions and sugars) are reabsorbed back into the blood from the tubules.
3. Excretion of waste - urea and excess water and ions travel to the bladder as urine, to be released from the body.
Bowman’s capsule & glomerulus
the start of the nephron…a hollow cup of cells surroudning a ball of blood called a glomerulus…
….it’s here where the blood is filtered
Control of the body’s water content…
The kidneys are controlled by a hormone called ADH (anti-diuretic hormone) which is produced by the pituitary gland.
The brain detects any changes in the water concentration of the blood.
- If the water concentration falls, then more ADH is produced. In response to this, the kidney reabsorbs more water. This means that a small volume of very concentrated yellow wee wee is produced. This reduces water loss.
- If the water concentration rises, then less ADH is produced. In response to this, the kidney reabsorbs less water. This means that a large volume of very dilute urine is produced. This increases water loss.
Hypothalamus
The hypothalamus is the processing centre in the brain that controls body temperature.
It does this by triggering changes to effectors, such as sweat glands and muscles controlling body hair.
Heat stroke can happen when the body becomes too hot; and hypothermia when the body becomes too cold.
How our body maintains a constant temperature
Temperature receptors in the skin detect changes in the external temperature. They pass this information to the processing centre in the brain, called the hypothalamus.
The processing centre also has temperature receptors to detect changes in the temperature of the blood. The processing centre automatically triggers changes to the effectors to ensure our body temperature remains constant, at 37°C. The effectors are sweat glands and muscles.
Two ways skin can control body temperature
- Hairs on the skin trap more warmth if they are standing up, and less if they are lying flat.
- If the body is too hot, glands in the skin secrete sweat onto the surface to increase heat loss by evaporation. This cools the body.
Describe the structure of skin…
epidermis = (top layer) dead cells that stop water loss and protect the body from invasion by bacteria / micro orgs
dermis = (middle layer) contains many sensory receptors & location of sweat glands* & hair follicles
hyodermis = (lower layer) fatty tissue which insulates body from heat loss
* guy…your sweat glands are stinky
