Chapter 13 - Excretion and Homeostasis

Question 1

What is excretion?

Answer 1

The removal of waste products of metabolism and substances in excess of requirements

Question 2

What is egestion?

Answer 2

The removal of undigested cellulose from the body as faeces

Question 3

What are the waste products of excretion?

Answer 3

Urea
Carbon dioxide
Excess water
Excess ions (salts)

Question 4

What are the waste products of egestion?

Answer 4

Undigested cellulose (fibre)
It is not the product of a chemical reaction

Question 5

The removal of faeces from the body is an example of excretion or egestion?

Answer 5

Egestion
As faeces is mainly undigested cellulose
It remains in the intestines and eventually passes out as faeces
The only excretory materials in it are bie pigments

Question 6

What are the waste products filtered by the kidneys and how are they removed from the body?

Answer 6

Urea, dissolved in water in urine
Excess ions, dissolved in water in urine
Excess water, depending on the amount of water drunk and the amount lost in sweat

Question 7

What are the waste products removed by the lungs and how?

Answer 7

Carbon dioxide, removed from the body by exhalation

Question 8

Where is Urea produced?

Answer 8

The liver

Question 9

How is Urea produced?

Answer 9

The amino acids from the diet are transported to the liver in the blood through the hepatic portal vein
The liver allows some amino acids to be transported in the blood to other parts of the body
The liver is important in the assimilation of amino acids
Some amino acids are converted to proteins, such as the plasma protein fibrinogen
The liver is also involved in the process of delamination (removal of the the nitrogen-containing part of the amino acids to form urea)
The Urea is formed in the liver from excess amino acids
The Urea dissolves in the blood plasma and is taken to the kidneys for excretion

Question 10

What is the function of the kidneys?

Answer 10

To filter blood and control the volume of water lost from the body in the urine

Question 11

What is the function of the ureter?

Answer 11

To carry urine away from the kidney

Question 12

What is the function of the urethra?

Answer 12

To carry urine out of the body

Question 13

What is the function of the bladder?

Answer 13

To store urine until it is convinient to expel it

Question 14

What is the function of the renal artery?

Answer 14

To carry oxygenated blood with more Urea content into the kidney

Question 15

What is the function of the renal vein?

Answer 15

To carry deoxygenated blood with less Urea content out of the kidneys

Question 16

What is the function of the cortex and where is it located?

Answer 16

Cortex filters the blood
It is located in the outer layer of the kidney

Question 17

What is the function of the medulla and where is it located?

Answer 17

The medulla determines the concentration of urine
It is located in the inner layers of the kidney

Question 18

Describe the structure of the glomerulus?

Answer 18

The glomerulus is a ball of blood capillaries, these provide a large surface area for ultrafiltration
The walls of the blood capillaries are one cell thick, contain tiny pores (called fenestration) and are covered by a thin basement memebrane
The membrane is partially permeable and only allows very small, soluble molecules or ions to pass through
The membrane is not permeable to blood cells, platelets and proteins
The high pressure in the glomerulus pushes blood plasma out of the capillaries

Question 19

Describe the process of ultrafiltration

Answer 19

Ultrafiltration takes place in the glomerulus
Blood is under high pressure and forced out of the glomerulus into the renal capsule to from the glomerular filtrate
This filtrate contains glucose, water, urea and salts
Large and insoluble plasma proteins and blood cells stay in the glomerulus

Question 20

Describe the process of selective reabsorption

Answer 20

Selective reabsorption takes place in the proximal convoluted tubule
All glucose and some salts are reabsorbed back into the blood by active transport against the concentration gradient
Water potential in the filtrate increases Most of the water is the reabsorbed back into the blood by osmosis leading to urea becoming more concentrated in the filtrate
The remaining filtrate is called urine Excess water, excess salts, and urea are passed out from the body as urine

Question 21

How is the wall of kidney tubule adapted for reabsorption?

Answer 21

Large number of mitochondria carry out aerobic respiration to provide energy for active transport
Microvilli increase the surface area for absorption
The wall is only one cell thick, which reduces the absorption distance

Question 22

What is homeostasis?

Answer 22

The maintenance of a constant internal environment

Question 23

Give 3 examples of homeostasis

Answer 23

Constant amount of water
Constant temperature
Constant concentration of glucose

Question 24

How is the blood glucose concentration controlled when it rises above the set point?

Answer 24

When the blood glucose concentration rises too high, the water potential of the blood decreases which can dehydrate cells
Pancreas detect the blood glucose concentration rising above the set point
The pancreas releases insulin
Insulin stimulates the liver to convert glucose to glycogen
The blood glucose concentration returns to normal, within the set point

Question 25

How is blood glucose concentration controlled when it falls below the set point?

Answer 25

When blood glucose concentration falls too low, cells may run short of energy
The pancreas detect the blood glucose level falling below the set point
The pancreas secretes glucagon
Glucagon stimulates the liver to convert glycogen to glucose
Glucose is released from the liver into the blood
The blood glucose concentration rises to normal, within the set point

Question 26

What are the symptoms of type 1 diabetes?

Answer 26

Slow wound healing
Glucose excreted in urine
Thirsty all the time
Blurred vision
Fatigue
Weight loss

Question 27

What are the causes of type 1 diabetes?

Answer 27

Autoimmune response against insulin-secreting cells

Question 28

What are the treatments of type 1 diabetes?

Answer 28

Insulin injections
Pancreas transplant
Restricted diet (should avoid excessive intake of carbohydrates)
Regular exercise

Question 29

What is a negative feedback mechanism?

Answer 29

A mechanism which returns conditions to the ideal or set point when they change from the ideal or set point ( when conditions move out of the set point )
When the level of something rises, the control systems reduce it again
When the level of something falls, the control systems raise it again

Question 30

Give an example of negative feedback and positive feedback

Answer 30

Control of blood glucose concentration is negative feedback

Hormones produced outside of set point during a woman giving birth is positive feedback

Question 31

What is the function of a shunt vessel?

Answer 31

Redirects blood flow deeper under the surface of the skin

Question 32

What is the function of an arteriole (or artery) ?

Answer 32

Regulates blood by constricting and dilating

Question 33

What is the function of a venule?

Answer 33

Collects blood from a network of the narrowest blood vessels

Question 34

What is the function of an artery?

Answer 34

Withstands the highest blood pressure

Question 35

What is the function of a capillary?

Answer 35

Allows the transfer of substances to and from the tissue fluid

Question 36

What is the function of a vein (or venule) ?

Answer 36

Transports blood towards the heart

Question 37

Describe the regulation of body temperature by negative feedback

Answer 37

Changes in body temperature are detected by thermoreceptors in the skin and hypothalamus ( a part of the brain)
The thermoreceptors in the skin detect the surface temperature of the body
The hypothalamus also contains thermoreceptors, which are sensitive to blood temperature change
Thermoreceptors send nerve impulses to the hypothalamus
The hypothalamus stimulates the effectors ( erector muscles, muscles in some parts of the body, arterioles, and sweat glands ) through nerve impulses

Question 38

How does the body regulate body temperature when the temperature falls?

Answer 38

The arteries constrict (vasoconstriction) and the shunt vessel dilates to reduce blood flow in the skin capillaries and to reduce heat loss by radiation
The skeletal muscles contract rapidly to release heat as a result of respiration in the muscles
The fatty tissue acts as an insulator by preventing heat loss from the surface of the skin
The erector muscles in the skin contract to pull hairs upright, this traps a layer of warm air at the skin

Question 39

How does the body regulator body temperature when the temperature rises?

Answer 39

The arterioles near the surface of the skin dilate and the shunt vessel constricts to allow for more blood flow in the skin capillaries, to allow more heat to be lost by radiation, and to bring more blood to the sweat glands and make more sweat
Releasing more sweat increases heat loss from the body as heat energy from the body will convert the water in sweat to water vapour
The erectors muscles in the skin will relax, and hairs will lie flat on the skin to prevent heat from being trapped in a layer of air on the skin

Question 40

Which 2 blood vessels the shunt vessel connect?

Answer 40

The shunt vessel connects an arteriole to a venule