Homeostasis And Response

Question 1

What is homeostasis?

Answer 1

Homeostasis is the maintenance of a constant internal environment in order to maintain optimum conditions for enzyme and cellular function.

Question 2

Give examples of conditions maintained by homeostasis in the body.

Answer 2

• Blood glucose concentration
• Body temperature
• Water levels

Question 3

What two types of responses are used in body control systems?

Answer 3

Nervous and chemical (hormonal)

Question 4

What three components do all control systems have?

Answer 4

• Receptors
• Coordination centres
• Effectors

Question 5

What is the function of a receptor?

Answer 5

Receptors detect changes in the environment (stimuli).

Question 6

What is the function of a coordination centre?

Answer 6

Coordination centres obtain and process information from receptors.

Question 7

What is the function of an effector?

Answer 7

Effectors (muscles or glands) bring about responses to stimuli.

Question 8

What is the function of the nervous system?

Answer 8

The nervous system allows the body to react to its surroundings and coordinate an appropriate response.

Question 9

How does a stimulus lead to a response being carried out by the body?

Answer 9

• Stimulus is converted to an electrical impulse
• The electrical impulse passes along sensory neurones to the central nervous system (CNS).
• The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response.

Question 10

What is the order of events for a response to stimuli?

Answer 10

Stimulus -> receptor -> coordinator -> effector -> response

Question 11

What is a reflex action?

Answer 11

A reflex action is an automatic and rapid response which does not involve any conscious input from the brain

Question 12

Why are reflex actions important?

Answer 12

Reflex actions aid survival by preventing harm to the body.

Question 13

Describe how a reflex action occurs via a reflex arc

Answer 13

• Stimulus is detected by a receptor
• An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS)
• At a synapse between a sensory neurone and a relay neurone, neurotransmitters diffuse across the gap and stimulate a new impulse which passes along the relay neurone.
• The same process occurs at a synapse between a relay neurone and a motor neurone
• At an effector, an appropriate response is carried out.

Question 14

What is the difference between a reflex pathway and a conscious pathway?

Answer 14

Within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious part of the brain. In a conscious pathway, the coordination centre is the conscious part of the brain.

Question 15

What is the name of the body’s coordination system which involves hormones?

Answer 15

The endocrine system

Question 16

What is a hormone?

Answer 16

A hormone is a chemical messenger secreted by a gland. It travels in the blood to a target organ where it causes a response.

Question 17

What type of effector secretes hormones?

Answer 17

Glands

Question 18

Which gland controls many other glands in the body?

Answer 18

The pituitary gland

Question 19

Why is the pituitary gland considered a ‘master gland’?

Answer 19

Secretes a wide range of hormones, some of which stimulate other endocrine glands.

Question 20

What is the role of the thyroid gland in the endocrine system?

Answer 20

Secretes the hormone thyroxine - controls metabolism, heart rate, and body temperature.

Question 21

What is the role of the pancreas in the endocrine system?

Answer 21

Secretes the hormones insulin and glucagon - controls blood glucose levels

Question 22

What is the role of the adrenal gland in the endocrine system?

Answer 22

Secretes adrenaline - controls the body’s ‘fight or flight’ response.

Question 23

What is the role of the ovaries in the endocrine system?

Answer 23

Secrete oestrogen, which coordinates the menstrual cycle and the development of female secondary sexual characteristics.

Question 24

What is the role of the testes in the endocrine system?

Answer 24

Secrete testosterone, which coordinates the production of sperm and the development of male secondary sexual characteristics.

Question 25

How does the pancreas respond when blood glucose levels are too high?

Answer 25

The pancreas secretes the hormone insulin. insulin binds to receptors on the liver and muscles, causing excess glucose to be converted into glycogen and stored.

Question 26

How does the pancreas respond when blood glucose levels are too low?

Answer 26

The pancreas secretes the hormone glucagon. Glucagon binds to liver cells causing glycogen to be converted into glucose and released into the blood.

Question 27

What is type 1 diabetes?

Answer 27

Type 1 diabetes is when the pancreas does not produce sufficient insulin to control blood glucose concentration. As a result, blood glucose levels are often very high, leading to excessive urination, tiredness and weight loss.

Question 28

How can type 1 diabetes be treated?

Answer 28

* Insulin injections before meals - allows glucose to be converted into glycogen * Limiting carbohydrate intake * Doing regular exercise which helps to remove excess glucose from the blood.

Question 29

What is type 2 diabetes?

Answer 29

Type 2 diabetes is a disorder in which the body’s cells stop responding to insulin, leading to an uncontrolled blood glucose concentration. It’s development is linked with increasing age and obesity.

Question 30

How can type 2 diabetes be treated?

Answer 30

* Following a carbohydrate controlled diet * Doing regular exercise * Use of drugs which increase insulin production and effectiveness

Question 31

What is the function of sex hormones during puberty?

Answer 31

* Males: Cause the development of secondary sexual characteristics * Females: Cause the development of secondary sexual characteristics and the maturation of eggs

Question 32

What is the main male sex hormone?

Answer 32

The main male sex hormone is testosterone, which is produced by the testes and controls sperm production.

Question 33

What is the main female sex hormone?

Answer 33

The main female sex hormone is oestrogen, which is produced by the ovaries and is involved in the menstrual cycle.

Question 34

What is the menstrual cycle?

Answer 34

The menstrual cycle is the monthly cycle of physiological changes that occur in females, involving the shredding of the uterus lining (menstruation) and ovulation.

Question 35

Describe the events of the menstrual cycle

Answer 35

* Uterus lining thickens and eggs begin to mature in the ovaries * An egg is released from one of the ovaries (ovulation) - uterus lining remains thick * If the egg is fertilised, pregnancy may occur. If not, both the egg and the uterus lining are shed during menstruation.

Question 36

What is ovulation?

Answer 36

Ovulation is the release of a mature egg from the ovaries, which occurs approximately every 28 days.

Question 37

Name the four main hormones involved in the menstrual cycle

Answer 37

* Oestrogen * Progesterone * Follicle stimulating hormone (FSH) * Luteinising hormone (LH)

Question 38

What is the role of FSH in the menstrual cycle?

Answer 38

FSH is secreted by the pituitary gland. It controls the maturation of eggs with in the ovaries (inside a follicle) and triggers the production of oestrogen by the ovaries.

Question 39

What is the role of oestrogen in the menstrual cycle?

Answer 39

Oestrogen is produced by the ovaries and released due to the action of FSH - it causes the regrowth of the uterus lining. It triggers the production of LH and restricts the release of more FSH.

Question 40

What is the role of LH in the menstrual cycle?

Answer 40

LH is produced by the pituitary gland as a result of oestrogen. It’s release triggers ovulation.

Question 41

What is the role of progesterone in the menstrual cycle?

Answer 41

Progesterone is secreted from the follicle of the ovary. It sustains the uterus lining and inhibits FSH and LH.