S6 L2 - Intro to the Endocrine System + Endocrine control of apetite

Question 1

Homeostasis:
What is homeostasis?
Mechanism exist at all levels - explain this…

Characteristics of a control system

Answer 1

What is homeostasis?
• Homeostatic mechanisms act to counteract changes in the internal environment
• Variables are regulated so that internal conditions remain stable and relatively constant
Homeostasis is not a steady state but a dynamic equilibrium. Failure in homeostasis leads to disease
Mechanism exist at all levels - explain this…
Mechanisms exist at all levels:
• Cell (e.g. regulation of intracellular Ca2+ concentration)
• Tissue (e.g. balance between cell proliferation and cell death (apoptosis)
• Organ (e.g. Kidney regulates water and ion concentrations in blood)
• Organism (e.g. constant body temperature)

Question 2

• *Biological Rhythms:**
• Another name for biological rhythm:
• ‘Biological clock’ in the brain is in small groups of neurones called
• Cues from the environment are called _______, these include…
• Why do people get jet lagged?
• Examples of a hormone and the gland that is is secreted from involved in setting the body clock?

Feedback:
Two main types of feedback
- How does negative feedback work (map showing all the hormones…)

Answer 2

Biological Rhythms:
- Another name for biological rhythm:
Circadian rhythm
- ‘Biological clock’ in the brain is in small groups of neurones called: suprachiasmatic nucleus
- Cues from the environment are called _______, these include….:
Zeitgebers
light, temperature, social interactions, exercise, eating/drinking pattern
- Why do people get jet lagged?
Mismatch between environment and body clock
- Examples of a hormone and the gland that is is secreted from involved in setting the body clock?
Melatonin from pineal gland

Feedback:
Two main types of feedback
How does negative feedback work (map showing all the hormones…)
(pic)

Question 3

Example of a control system:
Water
- What are the components of water in the body?
- What receptors monitior osmotic pressure?
- Osmolarity vs Osmolality? What are these?

Answer 3

Water components:
1/3 Extracellular —- 1/4 Blood plasma, 3/4 Interstial Fluid
2/3 Intracellular
- What receptors monitior osmotic pressure?
Osmoreceptors
- Osmolarity vs Osmolality? What are these?
pic

Question 4

The negative feedback that controls osmolarity…
Hormone
Mind map…

Answer 4

The negative feedback that controls osmolarity…
ADH
Mind map (pic)

Question 5

• *Plasma glucose homeostasis**
• negative feedback

Answer 5

Question 6

• *Endocrine system**
• What is this system?
• What are hormones?
• List some endocrine gland
• List some other organs and tissues involved…
• *Mechanisms of communication via hormones**
• 4 types

Answer 6

- What is this system?
The endocrine system is a collection of glands located throughout the body.
- What are hormones?
Hormones are chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues
- List some endocrine gland
Hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid gland, thymus, adrenal gland, pancreas, ovary, testis
- List some other organs and tissues involved…
Heart, liver, stomach, placenta, adpiose, kidney

• *Mechanisms of communication via hormones**
• pic

Question 7

• *Endocrine and nervous system**
• Common features between these two system
• Endocrine and nervous sytem - signal, nature, conveyance, mediators, speed

Answer 7

Question 8

• *Classification of hormones**
• Acronym
• *How are hormones transported?**
• Water soluble
• Lipid soluble
• Roles of carrier proteins

Answer 8

Classification of hormones
GAPS
(pic)

How are hormones transported?
Water soluble hormones:
Some hormones travel in blood in simple solution… peptides and adrenaline
Lipid soluble hormones: NEED BINDING PROTEINS
- Often specific proteins e.g. thyroid hromones (thyroxine-binding globulin)

ONLY THE FREE FORM IS BIOLOGICALLY ACTIVE - if a hormone is bound to a protein, it is not biologically active

Free hormone + Binding hormone Bound hormone

• *Roles of carrier proteins:**
• Increase solubility of hormones in plasma
• Increase half-life
• Readily accessible reserve

Question 9

• *Hormone Levels**
• Factors that determine hormone levels in blood
• How do hormones exert their effects…

Answer 9

Hormone Levels
- Factors that determine hormone levels in blood
1) Rate of production: Synthesis & secretion, the most highly regulated aspect of hormonal control
2) Rate of delivery: Higher blood flow to a particular organ will deliver more hormone.
3) Rate of degradation: Hormones are metabolized and excreted from the body.
- How do hormones exert their effects…
pic

Question 10

- How do water soluble hormones work: GPCR and Tyrosine kinase

- How do lipid soluble hormones water?

Answer 10

Question 11

• *Obestiy**
• What BMI is counted as obese?
• How can someone become overweight (science around this)
• *Control of Appetite**
• Which part of the hypothalamus is the control centre?

Answer 11

- What BMI is counted as obese?
BMI > 30kg/m^-2
- How can someone become overweight (science around this)
• Energy intake = expenditure -> body weight stable
• Energy intake exceeds expenditure -> energy stores (fat) will increase
• Energy expenditure exceeds intake -> energy stores deplete
Key word is ENERGY

Control of Appetite
- Which part of the hypothalamus is the control centre?
Arcuate nucleus

Question 12

• *Arcuate nucleus**
• What is the layout of this?

Answer 12

Arcuate nucleus
- What is the layout of this?
Blood -> hormones (produced by gut and body, on next flashcard) -> primary neurones (containing NPY, AgRP, POMC, alpha-MSH, beta-endorphin) -> primary neurones synapse with secondary neurones -> modulation of feeding behaviour

Question 13

• *Arcuate nucleus**
• Two types of primary neruone
• Neurotransmitters in each

Answer 13

Question 14

Hormonal signals from the gut to the hypothalamus
2

Hormonal signals from the body to the hypothalamus
3

Overview - Putting everything about the Arcuate nucleus together

Answer 14

PG LI

Hormonal signals from the gut to the hypothalamus PG
PYY (peptide tyrosine tyrosine):
Short (36-amino acid) peptide hormone released by cells in the ileum and promotes satiety
Ghrelin: ONLY ONE OUT OF 5 THAT STIMULATES APPETITE
Peptide hormone, released from stomach wall when empty, stimulates appetitie

Hormonal signals from the body to the hypothalamus LI
Leptin:
Peptide hormone released by adipocytes. Two effects: Stimulate the inhibitory (POMC) neurones and inhibits the excitatory (AgRP/NPY) neurones. Suppresses appetite
Insulin:
Suppresses apeptite. Stimulates inhibitory (POMC) neurones

Amylin:
Secreted by beta cells in pancreas
Suppressive appetite

Overview - Putting everything about the Arcuate nucleus together

Question 15

• *Leptin**
• What is the effect of a loss of function mutation in a leptin gene

Answer 15

- What is the effect of a loss of function mutation in a leptin gene

Leptin mutation leads to obestiy
Can be injected with leptin
This will resume normal appetite, so they will lose weight!

Leptin will not help someone loss weight who doesn’t just has common obesity