homeostasis and excretion(kidney) Flashcards
what is homeostasis
homeostasis is the state of steady internal physical and chemical conditions maintained by living systems.
maintaining a certain body temp.
what is thermoregulation
maintaining a constant body temperature so that is evening out heat losses and heat gains
what is the hypothalamus
an important regulatory centre in the brain which links the nervous system to the endocrine system
what is vasoconstriction
a small muscle in an arteriole contracts so the blood flows further from the surface of the skin and this causes less heat loss
what is vasodilation
a small muscle in an arteriole relaxes causing the blood to flow closer to the surface of the skin resulting in greater heat loss
what is pili erection
as external temperature decreases it causes the pili erector muscle to contract causing hairs to stand up on edge which traps a layer of air between your skin so therefore it reduces heat loss
what is sweating
sweat glands release water onto the surface of the skin increasing the rate of heat loss
what is shivering
when we shiver our muscles contract rapidly meaning respiration is necessary to supply energy in order to shiver which in turn generates heat
what is the function of the hypothalamus in homeostasis
triggers these responses
what responses cause heat loss
vasodilation and sweating
what responses causes heat gain/prevents heat loss
vasoconstriction, pilli-erection, goosebumps and shivering
describe the looping cycle that regulates the glucose levels after digestion
- meal eaten
- glucose levels rise
- insulin is secreted to create glycogen
- glucose levels fall
- glucagon is secreted to form glucose
- glucose levels rise
what is excretion
the removal of waste products from metabolic reactions of the body
what are examples of excretion
CO2, urea, waste hormones, bile pigments and excess medical drugs
what substance is formed from respiration taking place in all living cells, and excreted through lungs as air
carbon dioxide
what is produced during respiration excess from food and drink, excreted through the skin, kidneys and lungs, and excreted as sweat, urine or expired air
water H2O
what is produced in the liver from the breakdown of surplus proteins, excreted through the kidneys and skin, and excreted as urine or sweat
urea
what is formed in the liver cells, excreted through the kidneys, and excreted as urine
waste hormones and toxins
what is formed from the surplus of food and cells, excreted through kidney and skin, and excreted as urine or sweat
mineral salts
what does the liver and spleen from breakdown of red blood cells, excreted through bile duct into small intestine then gets excreted in the faeces
bile pigments
what are the sphincter muscles
hold urine in the bladder for several hours, but when they relax, urine is forced down the urethra and out of the body
where are the sphincter muscles based
at the base of the bladder
why is homeostasis necessary
The internal environment must be kept within certain narrow limits if an organism is to survive ,however, the external environments are constantly changing so the body needs a way of combatting that
what is the first stage of ultrafiltration in the kidneys
Blood is filtered under high pressure through narrow tubes – urea, glucose, water, everything except blood cells and larger molecules is forced out of the “blood”
what is the second stage of ultrafiltration in the kidneys
At the proximal convoluted tubule, useful molecules (glucose, minerals, amino acids) plus most of the water are selectively reabsorbed
what is the third stage of ultrafiltration in the kidneys
The Loop of Henle alters the salt concentrations in the medulla to aid the reabsorption of water from collecting ducts
what is the fourth and final stage of ultrafiltration in the kidneys
In the distal convoluted tubule, more water and some mineral ions are reabsorbed into the blood
The collecting duct’s permeability to water is based on the anti-diuretic hormone (ADH) the more ADH, the more water reabsorbed here, and so less urine produced. In this way the body can fine tune its water level.
