Week 2 - Endocrine System

Question 1

Learning Objective 1

Answer 1

Describe how the endocrine system maintains homeostasis

Question 2

Two communication systems maintain homeostasis

Answer 2

• nervous system
• endocrine system

Question 3

Nervous system
1. responds
2. generates and conducts __
3. through
4. altering activities of an

Answer 3

1. Quickly to stimulus
2. Electric signals
3. Highly specialised cells called neurons
4. Effector - specific muscles (skeletal, cardiac, smooth) or gland.

Question 4

Endocrine System
1. responds
2. producing and secreting __
3. into/through
4. altering activities of an

Answer 4

1. Slowly to stimulus
2. chemical messengers called hormones
3. bloodstream (blood plasma)
4. effector - cells that has appropriate hormone receptor

Question 5

Learning Objective 2

Answer 5

Briefly describe how endocrine glands are stimulated to secrete hormones,
the two chemical classifications of hormones and how hormones alter target cell activity

Question 6

Hormone are produced and secreted by

Answer 6

various endocrine glands located throughout the body

Question 7

stimuli that trigger endocrine glands to secrete their hormones can be grouped into three main categories :

Answer 7

1. Hormonal Stimulus
2. Humoral Stimulus
3. Neural Stimulus

Question 8

1. Hormonal Stimulus

Answer 8

• one hormone stimulates the secretion of another

Question 9

1. Hormonal Stimulus process

Answer 9

1. hypothalamus stimulates secretes a hormone that…
2. stimulates the anterior pituitary to secrete a hormone that…
3. stimulate other endocrine glands to secrete hormones (thyroid, adrenal cortex, gonad(testis))

Question 10

2. Humoral Stimulus

Answer 10

• changes in ion of nutrient blood levels e.g. glucose, Ca2+, Na+, K+.

Question 11

2. Humoral Stimulus

Answer 11

1. low blood calcium levels
2. stimulate parathyroid glands to secrete parathyroid hormone

Question 12

3. Neural Stimulus

Answer 12

Signals from the nervous system

Question 13

3. Neural Stimulus

Answer 13

1. Preganglionic sympathetic fibres
2. stimulate adrenal medulla to secrete adrenalin and noradrenalin

Question 14

Hormone secretion is also controlled by

Answer 14

feedback mechanisms - negative feedback returns hormones and blood levels to normal

Question 15

Negative feedback mechanism

Answer 15

1. stimulus - change in variable
2. receptor - detects change
3. control centre - endocrine gland increases hormone secretion
4. effector - hormone triggers target cell response
5. homeostasis restored - feedback to endocrine gland returns hormone secretion to normal levels

Question 16

Chemical classes of hormones

Two basic types according to chemical status:

Answer 16

1. Steroid Hormones
2. Amino Acid - Base Hormones

Question 17

Steroid Hormones

Answer 17

• made of cholesterol
• are lipid - soluble and can easily diffuse across the plasma membrane
• bind to receptors inside a cell - intracellular receptors

Question 18

Amino Acid - Base Hormones

Answer 18

• Vary in size - can be single amino acids, proteins or peptides
• are lipid insoluble and cannot easily diffuse across plasma membrane
• bind to receptors embedded in the plasma membrane - plasma membrane receptors

Question 19

Hormone actions

Answer 19

The binding of a hormone to its intracellular or plasma membrane receptor activates the target cell response.

Question 20

Response is depended on both

Answer 20

Hormone and target cell, insulin has different effects on liver cells and adipose cells

Question 21

Effects of hormone activation

Answer 21

• activating or deactivating enzymes > e.g enzymes required for metabolic reactions
• changing permeability of the plasma membrane by opening or closing ion channels
• stimulating protein synthesis > structural proteins for growth and cell division, enzymes for metabolic reactions, protein channels (e.g. aquaporins) for transportation