Pituitary gland and hypothalamus

Question 1

Antidiuretic hormone

Answer 1

Stimulates the kidneys to reabsorb water

Question 2

Oxytocin

Answer 2

• stimulates the contraction of uterine muscles during childbirth (an example of positive feedback) - stimulates milk release in breastfeeding

Question 3

Mechanism for posterior pituitary hormone secretion

Answer 3

1) stimulus: neural input to hypothalamus 2) hypothalamus signals posterior pituitary to release stored hormones by neural stimulation 3) ADH or oxytocin released into blood

Question 4

How the hypothalamus communicates with the posterior pituitary

Answer 4

• hypothalamus is connected to the posterior lobe by neurons - PP hormones are made in hypothalamus, travel down axon and stored at axon ending until required

Question 5

How the hypothalamus communicates with the anterior pituitary

Answer 5

• hypothalamus communicates with the anterior lobe by hormones in blood vessel - AP hormones are made in AP by specific cells

Question 6

Mechanism for anterior pituitary hormone secretion

Answer 6

1) stimulus: neural input into hypothalamus 2) hypothalamus signals the anterior pituitary to release hormones by hormonal stimulation, releasing hormones (or inhibiting hormones) 3) hormone binds to receptor on membrane of a specific cell type and a specific peptide hormone is secreted

Question 7

Growth hormone secretion sequence

Answer 7

1) Stimulus - stress, sleep, exercise, fasting 2) Hypothalamus - releases GHRH into bloodstream 3) Anterior pituitary - secretes growth hormone into bloodstream 4) Liver and other cells - increase in IGF-1 (growth factor) secretion 5) Metabolic effects

Question 8

metabolic effects of GH

Answer 8

increased protein synthesis and decreased glucose uptake in muscle, increased glucose synthesis in liver, increased fat breakdown by mobilising fatty acids

Question 9

GH disorders

Answer 9

• hyposecretion (too little) - dwarfism - hypersecretion (too much) - gigantism - Hyposensitivity (little or no response) - Hypersensitivity (respond too much)

Question 10

GH function

Answer 10

promotes the growth of bones, muscles and other tissues by stimulating cell division

Question 11

pituitary gland location

Answer 11

base of brain, attached to hypothalamus

Question 12

hormone

Answer 12

chemical messengers produced in one location and transported to a second location where they cause a response in those cells

Question 13

functions of endocrine system

Answer 13

Regulates our internal environment by secreting hormones into the bloodstream.

Question 14

Endocrine gland

Answer 14

secrete hormones

Question 15

major endocrine glands

Answer 15

hypothalamus, pituitary, thyroid, thymus, adrenal, testes

Question 16

Specificity of Hormone action

Answer 16

Target cells have specific receptors proteins that allows for specific and close hormone-target cell interaction

Question 17

hormone receptors for peptides and catecholamines

Answer 17

located on plasma membrane of target cell because they are water-soluble to cannot cross lipid bilayer

Question 18

hormone receptors for lipid-soluble hormones

Answer 18

located in cytoplasm (steroid hormones) or nucleus (thyroid hormones) because can diffuse across the cell membrane into target cell

Question 19

response to receptor activation of water-soluble hormones

Answer 19

1. Water-soluble hormone binds to cell surface receptor
2. Hormone binding allows activation of associated (G-) protein
3. G- protein activates adenylyl cyclase
4. Second messenger production e.g. cyclic AMP (cAMP)
5. cAMP activates protein kinase
6. Protein kinase activates specific enzyme Enzyme converts specific substrate to product (cell’s specific response)

Question 20

what determines amount of hormone in blood

Answer 20

• Rate of production – controlled by negative feedback loops (usually)
• Rate of removal – controlled by enzymes in the bloodstream

Question 21

response to receptor activation for lipid-soluble hormones (steroid and thyroid hormones)

Answer 21

1. Lipid-soluble hormone dissociates from carrier protein
2. Hormone diffuses across cell membrane
3. Hormone binds to INTRACELLULAR receptor
4. Hormone-receptor complex acts as a specific transcription factor
5. New mRNA is generated
6. New protein is generated by translation of mRNA
7. New protein mediates cell’s specific response (SLOW PROCESS)

Question 22

lipid soluble vs water soluble hormones

Answer 22

Question 23

comparison of endocrine and neural control systems

Answer 23

Neuronal (action potentials in axons and neurotransmitter release at synapse)

• Targeting achieved by specific wiring
• Fastest transmission speed to minimise response delays
• Good for brief responses

Hormonal (hormones released into blood)

• Targeting by expression of specific receptors on target cells
• Relatively slow, but long-lasting action
• Good for widespread and sustained responses

Question 24

pancreas and islets

Answer 24

• Head and neck in the C-shaped curve of the duodenum and the body extends behind the stomach
• Endocrine tissues called pancreatic islets are dispersed throughout the pancreas (~2% of mass)
• Beta cells secrete insulin
• Alpha cells secrete glucagon

Question 25

fed state

Answer 25

cellular uptake of nutrient and anabolic metabolism (synthesis of glycogen, protein and fat)

Question 26

fasting state

Answer 26

mobilisation of nutrient and catabolic metabolism (breakdown of glycogen, protein and fat)

Question 27

blood glucose regulation

Answer 27

• If blood glucose concentration rises above 6mmol/L insulin is secreted
• If blood glucose concentration drops below 3.5mmol/L glucagon is secreted
• Negative feedback for insulin release
• Also feedforward reaction- while eating, the pancreas releases insulin (signal from gastro-intestinal tract to pancreas)

Question 28

sequence of events that occurs when blood glucose concentration increases above the reference range

Answer 28

effects on muscle cells:

• amino acid uptake so protein synthesis
• glucose uptake so glycogen synythesis

effects on adipose cells:

• glucose uptake so fat synthesis

effects on liver cells:

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