Feedback

Question 1

What is the purpose of a negative feedback loop?

Answer 1

When a system is disturbed, it returns it to normal by responding to the stimulus opposingly

Question 2

What are negative feedback loops used for?

Answer 2

• Maintain homeostasis

Question 3

What is the purpose of a positive feedback loop?

Answer 3

Amplify a stimulus with a response,

- Stimulus increases due to responds

Question 4

What are feedback loops used for?

Answer 4

• Responding to internal/external stimuli

- Maintain internal environments

Question 5

What part of the brain is responsible for thermoregulation?

Answer 5

Hypothalamus

Question 6

How do our bodies respond to heat?

Answer 6

• Blood vessels dilate
• Increased breathing rate
• Sweating

Question 7

How do our bodies respond to cold?

Answer 7

• Blood vessels constrict
• Shivering
• Increased metabolism by secretion of Thyroid hormone from the thyroid gland

Question 8

What type of feedback loop is thermoregulation?

Answer 8

Negative feedback, temperatures are restored to their normal levels

Question 9

Can the hypothalamus detect temperature changes on its own?

Answer 9

Yes

Question 10

What type of feedback loop is ovulation?

Answer 10

• Positive originally

- Negative after the formation of the Corpus luteum

Question 11

Explain the positive feedback loop in ovulation.

Answer 11

• The ovaries secrete estrogen
• This triggers the hypothalamus to secrete gonadotropin releasing hormone and the anterior pituitary to release luteinizing hormone
• The gonadotropin releasing hormone from the hypothalamus also stimulates the release of luteinizing hormone from the pituitary
• Luteinizing hormone stimulates the ovaries to increase estrogen production, therefore the secretion of gonadotropin releasing hormone and luteinizing hormone also increase in the blood due to this positive feedback loop

Question 12

Explain the negative feedback loop in ovulation.

Answer 12

• The Corpus luteum is formed in the ovaries,
• The Corpus luteum secretes progesterone in response to the luteinizing hormone,
• Progesterone inhibits the release of gonadotropin releasing hormone and luteinizing hormone from the hypothalamus and anterior pituitary respectively,
• Blood levels of these hormones decrease due to this negative feedback loop.

Question 13

What type of feedback loop is labour preceding child birth?

Answer 13

Positive

Question 14

Describe the labour preceding child birth feedback loop.

Answer 14

• First, the loop is initiated by contractions of the uterus moving the baby’s head to the cervix
• The pressure from the baby on the cervix stretches the cervix and stimulates nerves which send a message to the brain,
• These impulses are received at the hypothalamus which secretes oxytocin into the blood capillaries of the pituitary gland and travels to the uterus,
• When the uterus receives the oxytocin, the contractions increase and more pressure is applied to the cervix,
• This creates a positive feedback loop as more signals are sent to the hypothalamus and more oxytocin is secreted,
• This continues to dilate the cervix and push the baby at greater rates and intensities until the baby is delivered,
• The positive feedback cycle ceases as the baby is born and no pressure is being applied to the cervix

Question 15

What is pancreatic juice made of?

Answer 15

• Digestive enzymes
• Water
• Sodium bicarbonate

Question 16

What is the role of sodium bicarbonate in pancreatic juice?

Answer 16

Neutralize the stomach acid so that digestive enzymes can work

Question 17

What is the role of insulin?

Answer 17

A hormone that tells cells to store sugar from the blood, and the liver to stop the production of sugar

Question 18

What is the role of glucagon?

Answer 18

A hormone that tells cells and the liver to release glucose in the blood

Question 19

Where are insulin and glucagon produced in the pancreas?

Answer 19

Islets of Langerhans

Question 20

What type of feedback loop is blood sugar regulation?

Answer 20

Negative

Question 21

What are some consequences of diabetes?

Answer 21

• Heart attack
• Stroke
• Kidney failure

Question 22

What does diabetes do to your body?

Answer 22

• Insulin production is less/stopped
• Blood glucose levels are too high
• The blood hardens and prevents blood flow

Question 23

What is type 1 diabetes?

Answer 23

The body doesn’t produce any insulin because an autoimmune system destroys the insulin-producing cells in the body

• Most commonly found in childhood,
• 10% of all diabetes cases, typically found under 40yrs of age

Question 24

How does the body try to remove high levels of glucose in the blood in type 1 diabetes?

Answer 24

Through filtering in the kidneys, glucose expelled in urine

Question 25

What are the main symptoms of diabetes?

Answer 25

- Frequent urination (body needs to release excess glucose) - Blurred vision (glucose builds up around the eye) - Tiredness (less energy from glucose) - Weight loss (no glucose in cells for energy so use fat deposit) - Thrush or genital itching (bacteria can survive better near glucose) - Slow-healing wounds (bacteria survives around the cut) - Thirst (water loss in the urine)

Question 26

How is type 1 diabetes treated?

Answer 26

Insulin

Question 27

What is type 2 diabetes?

Answer 27

Insulin is produced but either don't work properly or there is not enough produced - Around 90% of cases

Question 28

Why does insulin not work properly in type 2 diabetes?

Answer 28

- Fat deposits build up in the cells, this means insulin cannot open cells to glucose since they no longer fit in the protein

Question 29

In type 2 diabetes what is the relationship between glucose levels and insulin levels initially?

Answer 29

- Blood glucose increases - Insulin increase to counter this but is not very effective so blood glucose continues to rise - Insulin increases as glucose increases

Question 30

How quickly do symptoms arise for each type of diabetes?

Answer 30

- Type 1: very quickly (weeks) | - Type 2: very slowly (years)

Question 31

How do you treat type 2 diabetes?

Answer 31

- Controlled diet - Increased exercise - Medication

Question 32

How are the levels of water in the body maintained?

Answer 32

- Hypothalamus detects low levels of blood water - Posterior pituitary releases ADH - ADH travels in the bloodstream to blood vessels and the kidneys - Kidneys increase water retention and prevent as much water from leaving in the urine - Blood vessels vasoconstrict to increase pressure and compensate for low blood pressure caused by lack of water

Question 33

What is a receptor?

Answer 33

A protein molecule where a signal molecule can bind

Question 34

What is a ligand?

Answer 34

The molecule that binds to a receptor, typically smaller than the receptor

Question 35

What are the steps to cell signalling?

Answer 35

- Reception (receptor receives a signal) - Transduction (the receptor changes shape and passes on the signal to other molecules) - Response (how the cell responds to the singal)

Question 36

What are the types of signalling?

Answer 36

- Direct contact - Paracrine signalling - Synaptic signalling - Endocrine signalling - Autocrine signalling

Question 37

What is direct contact signalling?

Answer 37

Signals between cells through the plasmata or gap junctions

Question 38

What is paracrine signalling?

Answer 38

A type of local signalling where ligands are ejected from cells to travel a short distance and bind to another cell, - It must be local because ligands are rapidly absorbed and degraded

Question 39

What is synaptic signalling?

Answer 39

Neurotransmitters being the ligand between nerves

Question 40

What is endocrine signalling?

Answer 40

Signalling involving hormones

Question 41

What is autocrine signalling?

Answer 41

When a cell signals itself by releasing a ligand that rebinds to a receptor imbedded in the cell membrane or a peripheral protein - If excessive growth factor is released by the cell could lead to cancer

Question 42

What are the three classes of protein receptors?

Answer 42

- G-protein coupled receptor - Ion channel receptors - Enzyme couple receptors

Question 43

Do ligands use energy when it binds to a ligand transport channel?

Answer 43

No, these transport channels use passive transport/ facilitated diffusion

Question 44

What type of protein do hydrophobic ligands bind to?

Answer 44

Cytoplasmic protein receptors

Question 45

What type of protein do hydrophilic ligands bind to?

Answer 45

Transmembrane protein receptors

Question 46

What is signal trasnduction?

Answer 46

When the receptor receives a ligand, it undergoes some sort of change (usually a change in shape) and produces a signal inside the cell

Question 47

What do osteoblasts do?

Answer 47

Build up bone tissue

Question 48

What do osteoclasts do?

Answer 48

Break down bone tissue

Question 49

Where is PTH secreted and what is its function?

Answer 49

``` Secreted from the parathyroid gland - Increases calcium levels in the blood when they are too low by activating osteoclasts and causing them to degrade bones to release calcium into the blood (negative feedback) - Stimulates osteoclast activity - Inhibits osteoclast activity ```

Question 50

What is the function of calcitriol/ vitamin D?

Answer 50

Absorbs calcium into the gut

Question 51

What two hormones are used to increase blood calcium levels?

Answer 51

- Calcitriol | - PTH

Question 52

How is the release of PTH stimulated from the parathyroid glands?

Answer 52

Low levels of calcium

Question 53

What is secreted when blood calcium levels are too high?

Answer 53

C cells/ parafollicular cells from the thyroid secrete Calcitonin

Question 54

What is the function of calcitonin?

Answer 54

Stimulate osteoblast activity/ build bone matrix to reduce blood calcium levels (negative feedback)