Overview of the hypothalamo-pituitary axis and feedback loops

Question 1

What does the endocrine system do?

Answer 1

-Cell communication
-A control system, acting in partnership with the nervous system, to control other systems of the body
-Made up of a collection of endocrine glands & tissues, and their hormone products
-Controls all major body processes:
1 -Growth
2 -Homeostasis
3 -Reproduction
4 -Adaptation to stress
5 -Behaviour

Question 2

What is the ddifference between endocrine and exocrine glands

Answer 2

Endo- crine glands internal secretion
Endocrine glands secrete hormones directly into the bloodstream upon stimulation
Contrast with ‘exocrine glands (eg salivary glands. sweat glands & glands of the gastrointestinal tract) which secrete into ducts
Endocrine glands are therefore highly vascularised

Question 3

What are the three types of arrangement of endocrine cells in the body?

Answer 3

Endocrine organ- devoted to hormone synthesis
Distinct clusters of cells within an organ
Individuals cells scattered diffusely throughout the organ

Question 4

Give an example of endocrine organ devoted to hormone synthesis

Answer 4

Thyroid gland

Question 5

Give an example of distinct clusters of endocrine cells within an organ

Answer 5

Islets of Langerhans(pancreas)

Question 6

Give an example of individuals endocrine cells scattered diffusely throughout the organ

Answer 6

gastrointestinal tract, skin

Question 7

What hormones does the hypothalmus release

Answer 7

Releasing hormones & inhibiting factors e.g 
corticotrophin-releasing hormone CRF 
gonadotrophin-releasing hormone GnRH
Growth hormone releasing hormone GHRH 
Thyrotrophin-releasing hormone TRH 
dopamine

Question 8

What hormones does posterior pituitary release

Answer 8

Arginine vasopressin (AVP)
Anti-diuretic hormone (ADH)
Oxytocin

Question 9

What hormones does anterior pituitary release

Answer 9

Adrenocorticotrophic hormone (ACTH)
Growth hormone
Prolactin
Follicle stimulating hormone (FS)
Luteinising hormone L11-1)
Thyroid stimulating hormone (TSH)

Question 10

What hormones does thyroid gland release

Answer 10

Thyroxine (T4)
Tri-iodothyronine (T3)
Calcitonin

Question 11

What hormones does parathyroid gland release

Answer 11

Parathyroid hormone (PTH)

Question 12

What hormones does adrenal gland release

Answer 12

adrenaline

cortisol

Question 13

What hormones does pancreas release

Answer 13

glucagon

insulin

Question 14

What hormones does gonads release

Answer 14

Progesterone
Oestrogen
Testosterone

Question 15

What is the chemical nature of hormones related to?

Answer 15

How they are synthesised & secreted
Nature of hormone receptor they bind to
Ability to bind to other proteins (eg. transport proteins)
How they partition in tissues
How they are degraded

Question 16

What is the difference between peptide/protein hormone and steroid hormones in terms of their structure

Answer 16

Protein/Peptide: Chains of amino acids

Steroid: Cholesterol- derived

Question 17

What is the difference between peptide/protein hormone and steroid hormones in terms of where they are soluble

Answer 17

Protein/Peptide: Hydrophilic

Steroid: Lipophilic

Question 18

What is the difference between peptide/protein hormone and steroid hormones in terms how they are synthesised

Answer 18

Protein/Peptide: Gene transcription and post-translational modification in Golgi

Steroid: De novo biosynthesis (stepwise modification of cholesterol in mitochondria and SER)

Question 19

What is the difference between peptide/protein hormone and steroid hormones in terms of how they are stored

Answer 19

Protein/Peptide: Large amounts in secretory granules

Steroid: Not stored (nb cholesterol precursor stored as esters

Question 20

What is the difference between peptide/protein hormone and steroid hormones in terms of how they are secreted

Answer 20

Protein/Peptide: Exocytosis

Steroid: Simple diffusion

Question 21

What is the difference between peptide/protein hormone and steroid hormones in terms of how they are transported in the blood

Answer 21

Protein/Peptide: As free hormone

Steroid: bound to transport proteins

Question 22

What is the difference between peptide/protein hormone and steroid hormones in terms of the type of receptor that it binds to

Answer 22

Protein/Peptide: cell surface receptor

Steroid: Intracellular receptor

Question 23

What is the difference between peptide/protein hormone and steroid hormones in terms of the mechanism of action

Answer 23

Protein/Peptide: Activation of second messenger system to alter activity of existing proteins
Steroid: Activation of specific genes to produce new proteins

Question 24

List of major endocrine glands

Answer 24

Pituitary gland
thyroid gland
parathyroid gland
gonads 
Pancreas

Question 25

Which of the major endocrine glands are not controlled by the pituitary gland

Answer 25

Parathyroid gland | Pancreas

Question 26

How are major endocrine glands independent from pituatory controlled

Answer 26

Via Counter regulatory hormones | regulate nutrients or ions etc

Question 27

What is an endocrine hormone

Answer 27

Something produced within glandular cell that is released directly into circulation

Question 28

What is a Neuroendocrine hormone

Answer 28

hormones derived from neurone, manufactured and synthesised and transported along axons to be released in circulation

Question 29

What is an autocrine hormone

Answer 29

Acts upon the cells that release hormone Local diffusion local hormone act within extracellular fluid and distribute to neighbouring cells in environment

Question 30

What is a paracrine hormone?

Answer 30

Act on neighbouring cells Local diffusion local hormone act within extracellular fluid and distribute to neighbouring cells in environment

Question 31

What are the main chemical classes of hormone

Answer 31

Steroid | Non-steroid

Question 32

What are the 5 classes of steroid hormones

Answer 32

``` Progestagens Glucocorticoids Mineralocorticoids Androgens Oestrogens ```

Question 33

What are the 5 classes of non-steroid hormones

Answer 33

``` Polypeptide/Protein Glycoprotein Eicosanoids Peptides Amines ```

Question 34

What controls the pituitary gland?

Answer 34

Hypothalamus

Question 35

What does the hypothalamus-pituitary axis do?

Answer 35

Interface between CNS and endocrine system | Neuroendocrine control and homeostatic regulation

Question 36

What does the hypothalamus-pituitary axis homeostatically regulate?

Answer 36

``` Stress & immune function Reproduction Growth and development Water/electrolyte balance Energy balance/appetite control Thermoregulation Sleep/wakefulness ```

Question 37

Where is the hypothalmus in the brain?

Answer 37

Medio-basal forebrain

Question 38

What are the boundaries of the hypothalmus

Answer 38

Anterior (optic chiasm) Posterior (mammillary bodies) Superior (thalamus) Inferior (median eminence)

Question 39

How is the hypothalamus divided?

Answer 39

Bilateral either side of 3rd ventricle | Two nuclei

Question 40

What are the nuclei called in the hypothalamus

Answer 40

Paraventricular | Supraoptic nuclei

Question 41

What do hypothalamus nuclei contain and what do they release and to where?

Answer 41

hypothalamic neurosecretory cells Peptides From axon terminals adjacent to capillaries in the portal system

Question 42

What is the pituitary also known as?

Answer 42

hypophysis

Question 43

What does the pituitary made up of?

Answer 43

Two glands Anterior lobe Posterior lobe

Question 44

What is the anterior lobe of the pituitary called

Answer 44

adenohypophysis

Question 45

What is the posterior lobe of the pituitary called

Answer 45

Neuropophysis

Question 46

What percentage of the pituitary is the posterior lobe?

Answer 46

25%

Question 47

What percentage of the pituitary is the anterior lobe?

Answer 47

75%

Question 48

What is the posterior lobe of the pituitary made of?

Answer 48

Neural tissue

Question 49

What is the anterior lobe of the pituitary made of?

Answer 49

glandular tissue

Question 50

What is neural tissue made of?

Answer 50

axons & nerve terminal endings of hypothalamic neurosecretory cells

Question 51

What is glandular tissue made of?

Answer 51

cells controlled by releasing hormones (or inhibitory factors) delivered via hypophysial portal system

Question 52

Whcih lobe of the pituitary is in direct control of the hypothalamus?

Answer 52

Posterior

Question 53

What is the blood supply of the anterior pituitary lobe?

Answer 53

Superior hypophysial artery - primary portal plexus - long portal vessel- secondary plexus

Question 54

What is the blood supply of the posterior pituitary lobe?

Answer 54

Inferior hypophysial artery from middle hypophysial artery

Question 55

Which of the hormones released by the anterior pituitary lobe is with tropic action

Answer 55

Follicle stimulating hormone (FSH) Luteinising hormone (LH) Adrenocorticotrophic hormone (ACTH) Thyroid stimulating hormone (TSH)

Question 56

What does tropic action mean in terms of the pituitary gland

Answer 56

Goes on to regulate another structure or gland

Question 57

What are Follicle stimulating hormone (FSH) and Luteinising hormone (LH) and what do they regulate Important for what

Answer 57

Gonadotropins gonads Fertility

Question 58

What does Adrenocorticotrophic hormone (ACTH) regulate

Answer 58

the adrenal cortex | production of cortisol hormone

Question 59

What does Thyroid stimulating hormone (TSH) regulate

Answer 59

thyroid Production of thyroxin T3

Question 60

What will the growth hormone regulate?

Answer 60

The liver | Production of insulin growth factor IGF1

Question 61

What does prolactin regulate?

Answer 61

Fertility of an individual

Question 62

What is the "tripartite" neuroendocrine system

Answer 62

Stimulus--> hypothalmus-releasing hormone-> pituitary lobe-tropic hormone-> endocrine gland-hormone-> target cells

Question 63

How do we regulate the hypothalmus pituitary axis

Answer 63

Combination of feedforward drive and hormone negative feedback

Question 64

What is feedforward drive

Answer 64

Increases hormone output

Question 65

Biorythms?

Answer 65

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