Human Bio Ch 5

Question 1

What is a feedback system?

Answer 1

A circular situation in which the body responds to a change or stimulus with the response altering the original stimulus thus creating feedback.

Question 2

What are the 6 stages of. feedback system?

Answer 2

Stimulus - change occurs in the environment
Receptor - stimulus detected by sensory cells
Modulator - structure to analyse and interpret information
Effector - muscle/gland to carry out response to counteract stimulus
Response - action to alter stimulus
Feedback - feedback response to change original stimulus.

Question 3

What is the difference between negative feedback and positive feedback systems?

Answer 3

Negative feedback systems reduce or eliminate the stimulus whereas positive feedback systems enhance the stimulus and have no role in homeostasis.

Question 4

What is an example of a positive feedback system?

Answer 4

During childbirth the contractions that push the baby out become more and more extreme as more oxytocin is released. Another example is blood clotting to stop someone from bleeding out.

Question 5

What are the main homeostatic negative feedback loops?

Answer 5

• Increase and decrease blood glucose levels
• Increase and decrease body temperature
• Osmoregulation (too much or not enough water in the body)
• Regulation of gas concentration in the body

Question 6

What is the cellular respiration equation for the release of energy from glucose?

Answer 6

glucose + oxygen –> carbon dioxide + water + energy

Question 7

What are the main organs involved in the regulation of blood glucose?

Answer 7

1. The islets of Langerhans in the Pancreas and the adrenal glands secrete hormones that affect the levels of glucose in the blood
2. The Liver stores excess glucose as glycogen.

Question 8

What is the role of the liver in blood glucose levels?

Answer 8

The liver is able to convert glucose into glycogen for storage or glycogen to glucose for release into the blood. The liver has the first chance to absorb the nutrients from digested food as the blood from the stomach, spleen, pancreas and intestines go straight to the liver.

Question 9

What are the main roles of glucose in the liver?

Answer 9

1. It may be removed from the blood by the liver to provide energy for liver functioning
2. It may be removed by the liver/muscles and converted into glycogen for storage
3. It may continue to circulate in the blood available for body cells to absorb
4. It may be converted into fat for long-term storage.

Question 10

What is glycogenesis?

Answer 10

Is stimulated by insulin and is the formation of glycogen from glucose which occurs in the liver.

Question 11

What is glycogenolysis?

Answer 11

Is stimulated by glucagon and is the breakdown of glycogen to glucose that occurs between meals and happens in the liver and skeletal muscles.

Question 12

What is gluconeogenesis?

Answer 12

Conversion of fats or proteins into glucose and occurs in the liver.

Question 13

What is the role of the pancreas in the regulation of blood glucose levels?

Answer 13

The pancreas contain secreting glands called the Islets of Langerhans. The cells in the islets are divided into 2 types:
1. Alpha cells (glucagon)
2. Beta cells (insulin)
Both of these cell types work to increase (glucagon) or decrease (insulin) blood glucose levels.

Question 14

What effect does insulin have on the blood glucose levels?

Answer 14

When the beta cells secrete insulin it:
1. enables entry of glucose into cells especially skeletal muscles
2. promotes conversion of glucose into glycogen to be stored in the liver and muscles
3. promotes fat storage in adipose tissue
4. stimulates the conversion of glucose into protein
All of which reduce blood glucose levels.

Question 15

What effect does glucagon have on the blood glucose levels?

Answer 15

When the alpha cells secrete glucagon it:
1. stimulates the conversion of glycogen to glucose (glycogenolysis)
2. stimulates the conversion of fats or proteins into glucose (gluconeogenesis)
All of which increase blood glucose levels.

Question 16

What is the role of the adrenal glands in the regulation of blood glucose?

Answer 16

In relation to blood glucose levels the only parts of the adrenal glands that we are interested in is:
1. cortisol in the adrenal cortex (outer part)
2. adrenaline and noradrenaline in the adrenal medulla (inner part)

The adrenal cortex is stimulated to secrete hormones by adrenocorticotropic hormone (ACTH), this stimulates the release of Cortisol which stimulates the conversion of glycogen to glucose during glycogenolysis.

The adrenal medulla secretes adrenaline and noradrenaline that produce the same effects as those in the sympathetic nervous system one of them being the stimulation of the breakdown of glycogen in the liver sand the release of glucose into the blood.

Question 17

What is thermoregulation?

Answer 17

The regulation of body temperature, the balance of heat gain and heat loss in order to maintain a constant internal body temperature independent of the environmental temperature.

Question 18

What is the optimal body temperature?

Answer 18

37 degrees celsius

Question 19

What are the main forms of heat gain in the body?

Answer 19

1. Heat from body processes (metabolism) especially, respiration of the liver and muscle cells.
2. Heat gained from surrounding environment through conduction and radiation.
3. Exercise

Question 20

What are the main forms of heat loss in the body?

Answer 20

1. Radiation, convection and conduction to surroundings
2. Evaporation of water from the skins surface
3. The lungs breathe out hot air
4. Urine and faeces are warm

Question 21

What are the 4 main ways heat can be lost from the body?

Answer 21

1. Conduction - transfer of heat by direct contact between objects
2. Convection - transfer of heat through the movement of liquid or gas
3. Radiation - transfer of heat by infrared radiation being emitted by objects
4. Evaporation - liquid forms a gas which absorbs heat energy.

Question 22

What is the metabolic rate?

Answer 22

The rate at which energy is released to the body by the breakdown of food.

Many factors can affect metabolic rate including
- exercise (muscular activity increases body temperature)
- stress (increase body temperature due to the activities of the autonomic division of the NS)
- body temperature (when a person has a fever the metabolic rate may be double its normal rate)

Question 23

How to blood vessels aid heat regulation?

Answer 23

Blood vessels in the skin carry heat from the core of the body to the surface.
When the diameter of the blood vessels increase - Vasodilation - more blood is transported to the capillaries in the skin and more heat is removed.
When the diameter of the blood vessels decreases - Vasoconstriction - less blood is brought to the skin and remains closer to the core of the body making heat loss decrease.

Question 24

How does sweat aid heat loss?

Answer 24

When large amounts of heat need to be lost and skin blood vessels are already at maximum dilation, sweating via the sweat glands must occur. Sweating is the active secretion of fluid by the sweat glands and the periodic contraction of the cells surrounding ducts to pump the sweat to the surface.
Heat is removed when the sweat on the skin’s surface is evaporated into gas and the body cools down.

Question 25

How does shivering aid heat gain?

Answer 25

Shivering produces rhythmic muscle tremors (contractions) they occur at a rate of around 10 to 20 per second and as no work is being done the heat released by the muscles wams up the body.

Question 26

What are the 2 types of thermoreceptors?

Answer 26

1. Cold receptor - stimulated by low temperatures
2. Heat receptor - stimulated by high temperatures

Question 27

How does the body prevent the body temperature from falling?

Answer 27

Decrease heat loss:
1. vasoconstriction of blood vessels
2. reduction if sweating
3. behavioural changes like putting a jumper on
4. reduction of surface area by curling into a ball

Increase heat production
1. shivering
2. increase in voluntary activity (jogging on the spot)
3. increased metabolic rate (long-term response)

Question 28

How does the body prevent body temperature from rising?

Answer 28

Increase heat loss
1. vasodilation of blood vessels
2. sweating
3. behavioural changes like remove clothing or turning on air con
4. increase surface area by spreading out

Decrease heat production
1. decrease in voluntary activity (sit down)
2. decreased metabolic rate (long-term response)

Question 29

What is heat stroke?

Answer 29

When the body’s core body temperature is over 42 degrees there is a failure in the person’s temperature regulating mechanisms when exposed to excessive heat.

Question 30

What is heat exhaustion?

Answer 30

Happens more often than heat stroke and happens as a result of extreme sweating and vasodilation to lose heat and normally ends up with the person passing out.

Question 31

What is hypothermia?

Answer 31

When the body’s core temperature is below 33 degrees the body cannot maintain normal functions and the metabolic rate is so low that heat production is unable to replace the heat lost.