Introduction

Question 1

Peptide hormones

• Water solubility
• Oral activity
• Receptor activity

Answer 1

Very water soluble

Orally active- broken down my proteases (digestive enzymes in the mouth)

Receptors are membrane bound

• Requires membrane proteins to cross membrane
• Not lipid soluble

Question 2

Peptide hormones

• Speed of action
• Plasma half life

Answer 2

Rapid speed of action
- Seconds, minutes

Short plasma half life
- Protease activity

Question 3

Steroid/thyroid hormones

• Water solubility
• Oral activity
• Receptor activity

Answer 3

Not water soluble, but lipid soluble

Not orally activity

Binds to intracellular receptors
- Lipid soluble, can cross plasma membrane and nuclear membrane.

Question 4

Steroid/thyroid hormones

• Transport
• Speed of action
• Plasma half life

Answer 4

Transported in the blood via plasma proteins
- Not water soluble

Mostly slow acting
- Hours, days.

Slow plasma half life
- Only active when unbound

Question 5

Hormone definition [4]

Answer 5

• Chemical messenger released by a ductless gland
• Transported in the blood
• Acts on specific receptors on target tissues
• One hormone can affect multiple target tissues

Question 6

Endocrinology

Answer 6

Physiology of glands and hormones

Question 7

Endocrine

Answer 7

Method of cell signalling

- Chemical messenger (hormone) acts on target tissue far away from signalling cell.

Question 8

Paracrine

Answer 8

Method of cell signalling

- Chemical messenger acts on target tissue in close proximity to signalling cell.

Question 9

Autocine

Answer 9

Method of cell signalling

- Signalling cell secretes chemical messenger that acts on itself.

Question 10

Pituitary gland

• Location
• Anatomy
• Main function

Answer 10

Located at the base of the brain
- Sits in a bony case, sella turcica

Anatomy

• Connected to the hypothalamus via the infundibulum
• Portal system: hypothalamico-hypophyseal vessels—> Anterior
• Hypothalamico-hypophyseal tract—> Posterior

Function- master gland, secretes hormones to all glands.

Question 11

Hormones of the pituitary gland

Answer 11

Anterior

• Prolactin
• FSH
• LH
• ACTH
• GH
• TSH

Posterior

• Oxytocin
• ADH

Question 12

Thyroid + Parathyroid

• Anatomy
• Function

Answer 12

In the neck
- Below the larynx

• Controls metabolic rates
• Calcium homeostasis

Question 13

Adrenal glands

• Anatomy
• Function

Answer 13

On top of the kidneys

Functions

• Stress
• Blood sodium and glucose regulation

Question 14

Steroid hormone receptors

• Structure
• Mechanism
• Speed of action

Answer 14

Located in the cytoplasm or on nuclear membrane

Mechanism
1. Hormone binds to receptor to form hormone-receptor complex.

2. Complex binds to hormone-response element.
3. Hormone-response binds to DNA and affects gene transcription

Speed
- Slow acting, days of action.

Question 15

Endocrine organs

Answer 15

Pituitary gland
Thymus
Thyroid and Parathyroid
Adrenal gland
Pancreas
Gonads (Testes, ovaries)

Question 16

Tyrosine-kinase receptor - Action

• Speed
• Examples

Answer 16

Action: Receptor contains membrane bound enzyme

1. Hormone binds to receptor
2. Triggers phosphorylation of the receptor.
3. The receptor leads to cellular events that phosphorylates other intracellular proteins.

Speed: Very slow
- Used for growth and development

Example

• Prolactin
• Growth hormone

Question 17

G-protein coupled receptors

• Action
• Speed
• Examples

Answer 17

Action:

1. Hormone binds to 7 transmembrane receptor.
2. Secondary messenger is produced (cAMP, IP3)
3. Secondary messenger causes phosphorylation or influences other intracellular activity.

cAMP= smooth muscle relaxation
IP3= smooth muscle contractrion

Speed:
- Very fast action

Example:

• Adrenaline (adrenergic receptors)
• Calcitonin
• FSH

Question 18

Thyrotrophin releasing hormone [TRH]

Answer 18

Hormone released from the hypothalamus.

Triggers the release of thyroid stimulating hormone [TSH] from the anterior pituitary gland.

Question 19

Thyroid stimulating hormone [TSH]

Answer 19

Released from the anterior pituitary gland.
- Thyrotophic cells

Transported in the blood to the thyroid.

Stimulates the release of thyroxine.

Question 20

Corticotrophin releasing hormone [CRH] and adrenocorticotrophic hormone [ACTH]

Answer 20

CRH is released from the hypothalamus to the pituitary.

• Via hypothalamico-hypophyseal vessels.
• Triggers the release of ACTH from corticotropic cells

ACTH is released from the anterior pituitary.

• Transported in the blood to the adrenal cortex.
• Stimulates the released of cortisol.

Question 21

Gonadotrophin releasing hormone [GnRH] and Follicle stimulating hormone [FSH]

Answer 21

GnRH is released from the hypothalamus to the anterior pituitary gland.
- Triggers the release of FSH from gonadotropic cells.

FSH travels to the ovaries
- Stimulates the release of oestrogen

Question 22

Growth hormone releasing hormone [GHRH] and GH

• Secretion
• Action

Answer 22

GHRH is released from the hypothalamus to the anterior pituitary gland.
- Stimulates the release of GH from somatotropic cells

GH travels to the bones and stimulates linear growth.

Question 23

Luteinising hormone [LH]

• Secretion
• Action

Answer 23

LH is released from the anterior pituitary gland

• From gonadotropic cells
• Stimulates the ovaries to secrete progesterone
• Triggers ovulation

Question 24

Feedback control of hormones

Answer 24

Hormones can negatively inhibit the release of releasing and stimulating hormones.

• Cortisol inhibits CRH and ACTH.
• Progesterone inhibits LH.
• T3 and T4 inhibits TRH and TSH.

Question 25

Variation of cortisol release

Answer 25

Diurnal variation

• Peak in the morning, after waking. 9am.
• High Cortisol inhibits ACTH release

Drop in cortisol as the day progresses

• Allows increase in ACTH
• Cortisol lowest at night/sleep, 12am.

Question 26

Variation of oestrogen release

Answer 26

Monthly variation, overly roughly 28 days–> Menstruation cycle.
- Drop in oestrogen and progesterone allows disinhibition of hypothalamus to allow releasing of FSH and LH.