Excretion And Homeostasis

Question 1

Why does the body remove urea

Answer 1

Because it is toxic and if to much builds up in the blood you could get ill
Helps keep quantities of these substances in the blood at the correct level

Question 2

What organ gets rid of urea

Answer 2

The kidneys constantly remove urea from the blood by excreting it in urine.

Question 3

What are the 2 main parts of the kidney

Answer 3

The cortex and the medulla
Cortex- the tissue making up the outer layer in a kidney
Medulla- the tissue making up the inner layers in a kidney

Question 4

What are kidneys made up of

Answer 4

Thousands of tiny tubules called nephrons
Each nephron begins in the cortex then goes to the medulla, back to the cortex and then down again to the medulla
The nephrons join up with the ureter

Question 5

What does the ureter do

Answer 5

Carries urine that the kidney has made to the bladder

Question 6

Nephron

Answer 6

One of the thousands of microscopic tubes inside a kidney where urine is made

Question 7

Glomeruli

Answer 7

A little network of blood capillaries where the blood is filtered in a kidney
Renal artery splits up to make them
Sing. Glomerulus

Question 8

Urine formation

Answer 8

Blood flows into the kidneys from the renal artery then splits up into gomeruli. As it flows through the glomerulus it is filtered .
The filtrate includes water ions urea and glucose
These move to the nephrons
Some of the ions water and all of the glucose is absorbed back into the blood as it flows through the nephrons (reabsorption!)
What is left is urea and salts in water.
This is urine and it flows out of the kidney along the ureter into the bladder
It is stored in the bladder for a while and then released through the urethra

Question 9

Reabsorption

Answer 9

In the kidney nephron, taking back required substances into the blood

Question 10

Internal environment

Answer 10

The conditions inside the body

Question 11

Homeostasis

Answer 11

The maintenance of a constant internal environment

Question 12

how does homeostasis help your cells

Answer 12

to work as efficiently as possible
keeping constant temp. helps enzymes work at optimun rate
keeping a constant amount of water means that your cells are not damaged by absorbing or losing too much water
keeping a constant conc. of glucose means that there is always enough fuel for respiration

Question 13

by what is glucose concentration controlled by

Answer 13

hormones secreted by the pancreas,
insulin reduces the concentration of glucose in the blood.
glucagon increases the concentration of glucose in the blood

Question 14

insulin

Answer 14

a hormone secreted by the pancreas, which decreases blood glucose concentration

Question 15

islets

Answer 15

groups of cells scattered through the pancreas
make two hormones called insulin and glucagon

Question 16

if the glucose blood concentration is too low…

Answer 16

the pancreas secretes glucagon, this causes the liver cells to break down glycogen to glucose and release it into the blood.

Question 17

if the glucose blood concentration is too high…

Answer 17

the islets in the pancreas detect this and secrete insulin into the blood. when insulin reaches the liver, it cause the liver to absorb glucose from the blood. some is used for respiration

Question 18

set point

Answer 18

our blood glucose concentration is not absolutely constant.
the range of normal values for a particular parameter is called a set point

Question 19

negative feedback

Answer 19

a mechanism that detects a move away from the set point and brings about actions that take the value back towards the set point.

Question 20

type 1 diabetes

Answer 20

a condition in which insufficient insulin is secreted by the pancreas, so that blood glucose concentration is not controlled.

Question 21

treating type 1 diabetes

Answer 21

it can damage many different organs
patients check their blood glucose conc. regularly using a simply sensor or check their urine for glucose using a simple dipstick.
is urine contain glucose it is bad.(high)
eating little and often helps
injection with insulin (rapid or long acting)

Question 22

what is one of the most important organs involved in temp. regulation

Answer 22

the human skin
covered in a layer of dead skin cells which form a tough, impermeable barrier that prevents water evaporating from living cells below.

Question 23

sweat gland

Answer 23

a structure found in the skin of mammals, which secretes a watery fluid onto the skin to reduce body temperature.

Question 24

hypothalamus

Answer 24

part of the brain that is involved in the control of body temperature.
coordinates the activities of the parts of the body that can help keep temp

Question 25

sweat formation

Answer 25

sweat glands extract water and ions from the blood and produce sweat. this travels up the sweat duct to the skin surface and is released through the a pore.

Question 26

arteriols

Answer 26

blood vessels that bring oxygenated to the skin
these divide to from small capillaries that bring it to just below the surface of the skin.
then join together again to form venules

Question 27

hair erector muscle

Answer 27

small muscle attached to the hair
if the hair erector muscle contracts the hair goes up

Question 28

what is the last layer of the skin

Answer 28

a layer of fat
contains cells that produce large drops of oil
helps insulate the body against heat loss and acts a energy reserves

Question 29

how does the hypothalamus work

Answer 29

contains temperature receptors that sense the temp of blood running through it.
if above or below 37 then it send electrical impulses aloong the neurons to parts of the body which have function of regulating body temp.

Question 30

when temperature falls (below normal body temperature)
(muscles)

Answer 30

muscles contract- muscles in the body contract and relax very quickly (shivering)
they get the energy from respiration and some energy is released as heat.
the heat generated warms the blood as it flows through them. the body distributes the heat.

Question 31

when temperature falls (below normal body temperature)
(metabolism)

Answer 31

metabolism increases- the speed of chemical reactions may increase, not only in the muscles.
this also releases heat.

Question 32

when temperature falls (below normal body temperature)
(arteriols)

Answer 32

vasoconstriction- the arterioles become narrower. onyl a little blood can pass through, forcing most to lie underneath the fat layer. making sure that blood does not loose so much heat.

Question 32

when temperature falls (below normal body temperature)
(hairs)

Answer 32

hair stands up- the erector muscles contract, pulling the hairs up. does not help in humans
in animals, it traps a thick layer of warm air next to the skin.

Question 33

when temperature falls (below normal body temperature)
(sweat)

Answer 33

sweat glands reduce secretion

Question 34

when temperature rises (above the normal body temperature)
(arterioles)

Answer 34

vasodilation- the arterioles become wider and allow more blood to flow through.
allows heat to easily leave the blood into the air.

Question 34

when temperature rises (above the normal body temperature)
(hair)

Answer 34

hairs lay flat- the erector muscles relax
allows heat to leave the skin through radiation into the air

Question 35

when temperature rises (above the normal body temperature)
(sweat)

Answer 35

sweat production increases- sweat glands secrete more sweat. sweat lies on the surface of the skin and when it evaporates it takes heat from the skin with it

Question 36

vasodilation

Answer 36

widening of the arterioles, caused by relaxation of the muscle in their walls.

Question 37

vasoconstriction

Answer 37

narrowing of arterioles, caused by the contraction of the muscle in their walls.