B3.3 Maintaining Internal Environments

Question 1

Homeostasis

Answer 1

Maintenance of a stable internal environment in body,
despite fluctuations in the internal and external conditions

Question 2

Conditions which need to be controlled within the body

Answer 2

Temperature
Water levels
Blood glucose concentration
Blood solute levels
Blood pH

Question 3

Why temperature need to be controlled

Answer 3

To provide a suitable environment for enzymes,
so that they can work fatest at their optimum temperature

Question 4

Processes involving the skin which cool the body down

Answer 4

Sweating - water evaporates from skin surface resulting in increased energy transfer away from body
Vasodilation - Allow blood to flow closer to surface of skin allowing more heat to be released from body by convection and conduction
Hairs lie flat - preventing heat from being trapped by layer of still air between hair
These flat hairs increase flow of air next to skin increasing heat loss by convection

Question 5

Process of vasodilation

Answer 5

Thermoreceptors in hypothalamus detect a rise in core body temperature
Neural impulse sents to the blood vessels supplying capillaries at skin skin surface to dilate (smooth muscle in vessels = effector = relax)
Blood vessels dilate to allow more blood to enter capillaries
More blood flows closer to the skin surface where energy can be released by conduction

If we are too hot, then muscular walls relax
Allows more blood to enter and flow through capillaries close to skin surface
Excess heat energy is transferred to surroundings.

Question 6

Processes that work to keep body warm

Answer 6

Vasoconstriction
Shivering
Hairs lie flat on skin

Question 7

process of vasoconstriction

Answer 7

If we are too cold, then the muscular walls contract:
Thermoreceptors in the hypothalamus detect drop in core body temperature
Neural impulse sent to blood vessels supplying capillaries at skin
Blood vessels constrict to reduce blood flow in capillaries
This reduces blood flow to skin surface and heat energy is kept inside body and not lost to surroundings

Question 8

What happens when you get too hot

Answer 8

Body hairs lie flat – Hair erector muscle relaxes, hairs lie flat preventing an insulating layer of air forming around body, reducing heat loss to environment by radiation
Vasodilation - Blood vessels in the skin get wider allowing a larger volume of blood to flow near the skin surface, transferring heat to the environment by radiation
Sweating - Production of sweat from sweat glands. As the sweat evaporates it transfers heat away from body. Sweating also makes you lose water and mineral ions – you need to take in more liquid to replace lost water and mineral ions
Factors affecting evaporation – Temperature, humidity, wind speed, surface area exposed
What else – Remove extra layers of clothes, drink to replace water loss through sweating

Question 9

What happens when you get too cold

Answer 9

Vasoconstriction - Blood vessels supplying the skin capillaries get narrower caused by contraction of muscular wall of the blood vessels - reduces volume of blood flowing near the skin surface, and reduces the amount of heat lost from the body, causes pale appearance

Goosebumps – Hair erector muscles contract, hair stands up trapping a layer of air close to the skin - decreases heat loss to the environment by radiation

No sweat – The sweat glands stop producing sweat

Shivering - When core body temperature drops, muscles begin to twitch involuntarily - Rapid contraction and relaxation of the muscles requires respiration - respiration releases energy warming body

What else – Movement/exercise to warm-up, put more clothes on

Question 10

In the skin: Fat layer

Answer 10

Helps insulate the body, provides storage area for energy, helps protect internal structures

Question 11

In the skin: Skin Receptors

Answer 11

• Respond to stimuli, send information to the brain

Question 12

In the skin: Blood capillary -

Answer 12

Vessels supplying dilate when hot: increased blood flow at skin surface = more heat loss by radiation. Constrict when cold: decreased blood flow at skin surface = less heat loss by radiation

Question 13

In the skin: Hair Erector muscle

Answer 13

• Relax when hot = hairs lie flat. Contract when cold = hairs stand up

Question 14

In the skin: Sweat pore

Answer 14

• Sweat evaporates when hot = cooling

Question 15

On the skin: Hair

Answer 15

• Lies flat when hot = less air trapped so more heat loss by radiation. Stand up when cold = air trapped at skin surface so less heat loss by radiation

Question 16

In the skin: Epidermis

Answer 16

• waterproof barrier, protection from microbes etc

Question 17

In the skin: Dermis

Answer 17

• connective tissue , cushions the body from stress and strain

Question 18

In the skin: Sweat gland

Answer 18

• Produces sweat when hot to allow cooling by evaporation

Question 19

Why is it important to control blood glucose levels?

Answer 19

Glucose is the energy source used predominantly in respiration to transfer energy to ATP used by cells.
If levels rise too high this can damage blood vessels and nerves, increasing the risk of heart disease and stroke, kidney disease, vision problems, and nerve problems. In severe cases of uncontrolled blood sugar levels this can cause diabetic ketoacidosis (DKA), which can result in death.
If lows fall to low this can prevent cells from respiring effectively.

Question 20

2 effects caused by insulin secretion.

Answer 20

More glucose is taken up by cells decreasing blood glucose levels
Glucose is converted to glycogen decreasing blood glucose levels

Question 21

What does the secretion of glucagon cause

Answer 21

Cause glycogen to be broken down into glucose to raise the blood glucose concentration

Question 22

Difference between type 1 and type 2 diabetes

Answer 22

Type 1:
When pancreas is unable to produce (or does not produce enough) insulin
Can be controlled by diet alone
Begins in childhood
Controlled with insulin injection

Type 2:
When body no longer responds to insulin
Obesity
Immune system destroys pancreatic cells
Begins in adulthoodhood

Question 23

How can type 1 diabetes be treated?

Answer 23

Insulin injections
Insulin pump

Question 24

How can type 2 diabetes be treated?

Answer 24

Reducing the number of simple carbohydrates in diet
Losing weight
Increasing exercise
Drugs to make insulin more effective in body cells / help the pancreas makes more insulin / reduce the amount of glucose absorbed from the gut
Insulin injections may be used in some cases.

Question 25

Why is it important to maintain water balance?

Answer 25

The body need to to balance water and salts in (via food / drink / respiration) and water out (via sweating and excretion).
Ensure water and salt levels in blood plasma remain constant
Changes to water and salt levels in blood plasma can cause damage to cells.

Question 26

What happens if an animal cell is placed in a solution of higher water potential (too much water present / too little solute present in blood plasma)?

Answer 26

Water will move into the cell.
The cell will burst (lyse).

Question 27

What happens if an animal cell is placed in a solution of lower water potential (too little water present / too much solute present in blood plasma)?

Answer 27

Water will move out of the cell
The cell will shrink (crenate).

Question 28

What happens if an animal cell is placed in a solution of eqaul water potential (water and solute levels the same blood plasma / isotonic)?

Answer 28

There will be not net movement of water into or out of the cell.

Question 29

What is urine?

Answer 29

A liquid waste product containing water, urea and other waste substance produced by the kidneys.
Urea needs to be removed from the body because it is toxic.
formed when the digestion of protein results in an excess of (too many) amino acids, which can’t be stored in the body.
When there is too much urea in the bloodstream, it can harm cells and tissues.

Question 30

function of the kidneys?

Answer 30

Maintaining the balance of water and other substances in the body through urine production.
Filtering out the waste products, such as urea, water and ions from the body
Selectively reabsorbing useful substances such as glucose, ions and water into the blood.

Question 31

general structure of a kidney.

Answer 31

Three main regions: cortex, medulla & pelvis.
Renal artery (red) carries blood away to the kidneys
Renal vein (blue) carries blood away from the kidneys
Each kidney contains 1-1.5 million nephrons
Ureter carries fluid from the kidneys to the bladder

Question 32

Nephron diagram

Question 33

Ultrafilration

Answer 33

Blood enters the kidney under high pressure from the renal artery
The renal artery branches into arterioles, each leading to a glomerulus
At the glomerulus there is a knot of capilaries with a narrower arteriole leaving it than the arteriole supplying it therefore increasing the blood pressure
Increased blood pressure forces small molecules including water, glucose, salts and urea out of the glomerulus and into the Bowman’s capsule
Large molecules such as red blood cells and protein molecules are too large to pass through the capilary wall so remain in the bloodstream

Question 34

Selective reabsorption

Answer 34

Filtrate passes through the proximal convoluted tubule - all of the glucose in reabsorbed and some water and salts
Next, filtrate travels down through the loop of Henle where water and salt levels are balanced
Filtrate then passes through distal convoluted tubule and collecting ducts where remaining water can be further balanced using ADH secretion to fine tune water levels via negative feedback control

Question 35

ADH

Answer 35

ADH (anti-diuretic hormone) increases permeability of DCT and collecting duct to water
Increased permeability = increased water reabsorbed into the blood stream from collecting duct
Increased water reabsorbed = more concentrated urine

Too little water:
hypothalamus triggers the pituitary gland to release anti-diuretic hormone (ADH)
ADH increases the permeability (ability of things to pass through) of the kidney tubules
This means that more water is reabsorbed back into the bloodstream.
This results in a small volume of concentrated urine.

Question 36

negative feedback loop when dehydration is detected.

Answer 36

Osmorecptors in the hypothalamus detect low water levels
Thirst response stimulated
Hypothalamus stimulates the pituiaty gland to secrete more ADH
ADH travels in the blood to the collecting ducts of the kidneys where it stimulates an increased in permeability to water.
More water is reabsorbed and retained by the body

Question 37

negative feedback loop when overhydration is detected.

Answer 37

Osmorecptors in the hypothalamus detect high water levels
Hypothalamus stimulates the pituiaty gland to secrete less ADH
Collecting ducts of the kidneys show a decreased permeability to water.
Less water is reabsorbed and retained by the body
Dilute urine is produced
Salts at retained

Question 38

Negative feedback

Answer 38

Action taken by body to return something to a normal optimum level following a deviation from that level
This is how the body keeps conditions constant at optimum level (homeostasis)

Question 39

how the body responds to eating a sugary meal

Answer 39

Blood glucose concentration increases
pancreas releases insulin
Insulin travels in bloodstream
The liver is stimulated
Glucose is converted to glycogen
Glycogen is stored in liver
Blood glucose concentration drops

Question 40

blood vessels closest to the surface of the skin

Answer 40

Capillaries
5 - 10 um

Question 41

Deamination

Answer 41

In the liver, amino acids in blood undergo a process known as deamination, and the waste product is ammonia

Question 42

optimal blood glucose range for humans

Answer 42

6-8 mmol/dm³

Question 43

Advantages and disadvantages of dialysis

Answer 43

Advantages
Gives patients and doctors more time to find a donor kidney

Disadvantages:
Lasts 3-4 hours and is needed 3 times a week
Increases risk of blood clots and infections
Expensive process

Question 44

Uremia is often a tell-tale sign of what

Answer 44

kidney failure

Question 45

Which technology allows us to produce images of damaged organs

Answer 45

MRI