Metabolism S7 - Endocrine System Flashcards Preview

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Define 'Hormone' and briefly describe the features of hormone control.

A hormone is a chemical messenger that travels via the bloodstream

Hormones are secreted from endocrine glands and travel in the bloodstream to target cells where they exert their effect.


What are the classes of Hormone?



Amino acid derivatives



Describe the physical features of polypeptide hormones and give some examples of polypeptide hormones

Short or long chain amino acids

Eg. Insulin, Glucagon, Growth hormone


Describe the physical features of glycoprotein hormones and give some examples of glycoprotein hormones

Large protein molecules with carbohydrate side chains

Eg. Luteinizing hormone, Follicle stimulating hormone, Thyroid stimulating hormone

(Notice these are all anterior pituitary hormones, good way to remember)


Describe the physical features of Amino acid derivative hormones and give some examples of amino acid derivative hormones

Small molecules synthesised from amino acids

Eg. Adrenaline, Thyroxine, Tri-iodothyronine


From what are steroid hormones derived?

Give some examples of steroid hormones

All derived from Cholesterol

Cortisol, Aldosterone, Testosterone, Oestrogen


What Hormones are hydrophilic and which are hydrophobic?

Why is this significant to their transport around the body?

Hydrophillic: Polypeptide hormones, Glycoproteins hormones and adrenaline

Hydrophobic: Steroids and thyroid hormones

Hydrophobic need special transport proteins to dissolve in blood (small amount dissolves in plasma) for transport whereas hydrophilic hormones can travel dissolved in plasma.


Why is transport method of hormones in blood relevant to their effect on target cells?

Bound hydrophobic proteins are not physiologically active, therefore only the concentration of free/unbound hormone matters.


Give an example of the physiological effects of hormone deficiency or excess of a particular hormone

Growth hormone

Excess leads to acromegaly

Deficiency leads to failure to grow properly

Your example may vary, Check it!


How is hormone binding to a target cell dependent on it's chemical nature?

Hydrophobic hormones can cross the plasma membrane and bind to cytoplasmic or nuclear receptors

Hydrophilic hormones cannot cross the cell membrane readily so will bind to receptors on the cell surface


Give a brief description of a hormones binding and affect on a target cell

Will bind to a specific, high affinity receptor

This binding will trigger a change in the cell

Eg. Enzyme/protein activity, gene expression


When a hydrophilic hormone binds to the target cell, what process occurs before a change is cell activity is exerted?

Binding on the cell membrane will often trigger a secondary messenger within the cell which will in turn influence cell activity.


What is target tissue response time to a hormone dependent on?

Show an rough appreciation of the difference in response time.

Rapid response (seconds to minutes) is seen when hormone effect is altering the activity of functional proteins such as enzymes or transport proteins

Slower response (minutes to hours) time is seen to hormones that alter gene expression


Do hormones always have only one target tissue?


Give some examples of hormones and target tissues

No, they can hove one or multiple

For example:

TSH only affects thyroid gland

Insulin has effects on the Liver, Muscle and Adipose tissues


What are the 4 ways in which hormone secretion is controlled?

Negative feedback

One hormone controlling another

Releasing or inhibiting control hormones

Inactivation of Hormones


How is negative feedback used to control hormone secretion?

Secretion rate is affected by blood concentration.

As soon as blood concentration/the effect of a hormone decreases below critical level this stimulates secretion of the hormone until correct level is achieved.


Give an example of negative feedback hormone control.

Insulin secretion

Beta cells of the pancreas are sensitive to blood glucose concentration, when blood glucose rises above 5mM then this stimulates Insulin secretion


What are hormones that control other hormones called?

Where are they secreted from?

Hormones controlling another hormone are called trophic hormones

They are mostly secreted by the anterior pituitary gland.


Give the 6 main hormones secreted by the pituitary gland.

TSH - Thyroid stimulating hormone

ACTH - Adenocorticotrophic hormone

GH - Growth hormone

LH - Luteinizing hormone

FSH - Follicle Stimulating hormone



Give 4 examples of trophic hormones

Thyroid stimulating hormone

Adenocorticotrophic hormone

Luteinizing hormone

Follicle stimulating hormone


Give an example of a trophic hormone controlled by negative feedback and describe the process of negative feeback in this instance.

Thyroid stimulating hormone

When thyroid hormone concentration in the blood gets too high then TSH secretion falls, therefore thyroid hormone secretion falls

The opposite is true for a fall in thyroid hormone concentration


Your example may vary, check it!


Explain the action of Inhibiting or releasing hormones and give 4 examples

These hormones are secreted from nerve cells in the hypothalamus and travel to the gland via hypophyseal portal vessels.

This allows the brain to control hormone secretion


Thyrotrophin releasing hormone

Corticotrophin releasing hormone

Somatotrophin releasing hormone



What organ does thyroid stimulating hormone affect?



What gland does Adenocorticotrophic hormone affect?

Adrenal glands


What process does growth hormone affect?



What organs do luteinizing hormone and follicle stimulating hormone affect?

Ovaries or testis


What processes does Prolactin affect?

Breast development and milk production


What are 4 examples of hormones secreted from the hypothalamus and their effects?

Thyrotrophin releasing hormone

Stimulates TSH release


Corticotrophin releasing hormone

Stimulates ACTH release


Somatotrophin releasing hormone

Stimulates GH release



Inhibits GH release


Where does inactivation of hormones occur?

Liver or kidneys


How are steroid hormones inactivated?

By relatively small changes in chemical structures that increase their water solubility enabling their excretion in the urine or bile


How are protein hormones inactivated?

Undergo extensive chemical change and are degraded into amino acids to be recycled


Where is the appetite centre of the brain?

In the arcuate nucleus of the hypothalamus


What two types of neurone are present in the arcuate nucleus?

Primary neurones

Secondary neurones


What are the general functions of primary neurones in the arcuate nucleus?

Sense metabolite levels

Respond to hormones


What is the general function of secondary neurones in the arcuate nucleus?

Sense input from primary neurones and co-ordinate a response via the vagus nerve


What are the two types of primary neurone in the arcuate nucleus?




What is the function of Excitatory primary neurones in the arcuate nucleus?

Stimulate appetite via the release of Neuropeptide Y (NPY) and agouti-related peptide (AgRP)


What is the function of inhibitory primary neurones in the arcuate nucleus?

Suppress appetite by releasing Pro-opiomelanocortin (POMC)


What results from the peptide cleavage of pro-opiomelanocortin?

POMC is a prohormone that can be cleaved to produce:


Adenocorticotrophic hormone

alpha-Melanocyte stimulating hormone (alpha-MSH)


What is the function of alpha-melanocyte stimulating hormone?

Suppressing appetite by working on melanocortin 4 receptors


What is the arcuate nucleus' response to the stomach being filled?

POMC is released to suppress appetite

beta-Endorphin (from the POMC) give feelings of euphoria and tiredness


List the hormones involved in appetite and where they're secreted from.

Arcuate nucleus:

Neuropeptide Y

Agouti-related peptide

POMC (+beta endorphin) 




Ghrelin I



Small intestine:








Discuss nature of Ghrelin I, where it's released from, its effects on appetite and its inhibitory factor(s)

Peptide hormone released from empty stomach

Activates stimulatory neurones in arcuate nucleus

Increases appetite

Stretch of stomach wall inhibits


Discuss the nature of Leptin and its effects on metabolism

Peptide hormone released into blood from adipocytes

Stimulates inhibitory neurones and inhibits stimulatroy neurones of the arcuate nucleus

Descrease in appetite

Acts as a feedback mechanism from body's fat stores

Induces expression of uncoupling proteins in mitochondria


What is leptin insensitivity associated with?



What is PYY?

Where is it secreted from and what is its effect?

Peptide hormone

Released from small intestine

Decreases appetite


How is insulin involved in control of appetite?


Decreases appetite via same mechansm as leptin

Leptin still more important in tthis function


What is amylin?

How is amylin involved in control of appetite and what are its effects?

Peptide hormones secreted from B-cells of pancreas 

Decrease appetite

Decrease glucagon secretion

Slows gastric emptying 


What is 'metabolic syndrome'?

A group of symptoms including:

Insulin resistance


Glucose intolerance



Symptoms associated with central adiposity

Co-occurence of cardiovasular risk factors (dyslipidaemia, hypertension)

All in conjuction with obesity and sedentary lifestyle



What are the major factors that predispose to insulin resistance?


Sedentary lifestyle


What is insulin resitance associated with?

Dyslipidaemic profile (HIgh VLDL and LDL, Low HDL) that is highly atherogenic

Risk of hypertension



What are the WHO criteria for metabolic syndrome?

Central obesity with waist:hip ratio of:

>0.9 in men

>0.85 in women

BMI above 30kg/m2

Blood pressure >140/90mmHg

Triglycerides >1.7mmol/L

HDL cholesterol <0.9mmol/L (in men) <1mmol/L (women)

Fasting glucose of >7.8mmol/L

Glucose uptake during hyperinsulinaemic euglycaemic clamp in lowest quartile of population (High insulin resistance)


What was the basis for the development origins of health and disease theory?

What does this suggest?

Study conducted showing that incidence of coronary heart disease, hypertension and T2 diabetes are related to low birth weight

Suggests the experience of a foetus in utero during development somehow determines the future health of the individual


What effect on the foetus does nutrient supply have?

Biochemical adaptations occur that are 'programmed in' for adult life

This 'programming in' involves switching on/off gnees at critical times in foetal development


Is birth weight a heritably trait?

If so, what might be the explanation for this?


Explanation provided by epigenetics:

An epigenetic trait is a stably inherited phenotype resulting from changes in a chromosome without alterations to the DNA sequence

These changes may include Methylation of DNA at key points and altering of histone structure.