Chapter 45 - Hormones & the Endocrine System

Question 1

Describe types of signaling pathways.

Answer 1

• Direct contact
• Paracrine
  
  • molecules diffuse locally and trigger repsonse in neighboring cells
• Autocrine
  
  • molecules diffuse locally and trigger a response in the cells that secrete them.
• Endocrine
  
  • molecules diffuse into bloodstream and trigger repsonses in target cells anywhere in body.
• Neuroendocrine
  
  • neurohormones diffuse into bloodstream and trigger responses in target cells anywhere in body.
• Synaptic
  
  • neurotransmitters diffuse across synapses and trigger responses in cells of target tissues (neurons, muscles, glands)
• Pheromones
  
  • checmicals released into environment

Question 2

Describe the general principles of signaling chemical types.

Answer 2

Specific cells are affected depending on:

• Type of receptor
• Signal transduciton pathways
• Effector proteins

Question 3

Describe water-soluble hormones vs. lipid-soluble hormones vs. local regulators.

Answer 3

• Water-soluble Hormones
  
  • Consists of polypeptides & some amines.
  • Secreted via exocytosis.
  • Travels easily in blood.
  • Binds to receptor on cell surface setting off cascade event.
• Lipid-soluble Hormones
  
  • Consists of steroids & some amines
  • Diffused across membranes
  • Require blood transport proteins to travel.
  • Acts via intracellular receptor on either cytolpasm or nucleus.
  • Affects gene transcription.
• Local Regulators
  
  • Not hormones, but molecules that act quickly by diffusing across short distances
    
    • Ex: Paracrine & autocrine signaling

Question 4

Name the gland that produces and describe the function of anti-diuretic hormone (ADH).

Answer 4

• Produced by the posterior pituitary gland
• Promotes retention of water by kidneys
• Regulated by salt & water balance

Question 5

Name the gland that produces and describe the function of oxytocin.

Answer 5

• Produced by posterior pituitary gland (an extension of the hypothalamus)
• Stimulates contraction of uterus and mammary gland cells

Question 6

Name the gland that produces and describe the function of the group of thyroid hormones, including possible imbalances.

Answer 6

The thyroid gland produces:

• Triiodothyronine (T₃) and thyroxine (T₄):
  
  • stimulates and maintain metabolic processes.
  • regulated by thyroid-stimulating hormone (TSH) from anterior pituitary gland.
• ​Hyperthyroidism:
  
  • ​Speeds up metabolic rate.
• ​Hypothyroidism:
  
  • ​Metabolic rate slows.
• ​Imbalances sometimes involves pituitary gland:
  
  • ​Not enough or too much TSH produced.

Question 7

Name the gland that produces and describe the function of calcitonin & PTH.

Answer 7

• Parathyroid hormone (PTH) produced by parathyroid glands
  
  • Raises blood calcium level
  • If blood calcium decreases, PTH releases calcium from bone, reabsorbs calcium in kidneys, and increases uptake of food calcium via vitamin D activation in liver
• Calcitonin produced in thyroid gland
  
  • Lowers blood calcium level
  • If blood calcium increases, calcitonin is released and causes opposite effects
  • Only really used in childhood

Question 8

Name the gland that produces and describe the function (including homeostatic imbalances) of insulin & glucagon.

Answer 8

• Insulin is produced by the pancreas
  
  • Lowers blood glucose level
  • Increases uptake of glucose by cells
  • Decreases glyocen breakdown in liver
• Glucagon is produced by the pancrease
  
  • Raises blood glucose level
  • Increases glycogen hydrolysis in liver
  • Converts fat and proteins into glucose
• Diabetes is an imbalance resulting in high blood glucose
  
  • Type I (insulin-dependent) develops in childhood
    
    • Insulin producing beta cells are destroyed by immune system
    • Requires daily insulin injections
  • Type II (non-insulin-dependent) develops in adulthood
    
    • Deficiency of insulin or decreased insulin sensitivity
    • Caused by heredity, unhealthy lifestyle

Question 9

Name the gland that produces and describe the function of catecholamines & corticosteroids.

Answer 9

• Catecholamines are “fight-or-flight” hormones (short-term stress response) and produced by adrenal glands
  
  • Epinepherine raises heart & metabolic rates
  • Norepinephrine constricts certain blood vessels
• Corticosteroids produced by adrenal glands and participate in long-term stress responses.
  
  • Glucocorticoids raise blood glucose level
    
    • Anti-inflammatory effects
  • Mineralocorticoids promote reabsorption of sodium and excretion of potassium in kidneys.

Question 10

Name the gland that produces and describe the function of sex hormones.

Answer 10

• Controlle by follicle -stimulating hormone (FSH) and luteinizing hormone (LH) from anterior pituitary gland
• Produces androgens in males (testosterone)
  
  • Determines sex in embryo and secondary male characteristics
• Produces estrogens (estradiol) in females…
  
  • Maintains female reproductive system and secondary sexual traits
• … and progestins (progesterone)
  
  • Prepare and maintain uterus for embryo development

Question 11

Name the gland that produces and describe the function of melatonin.

Answer 11

• Produced by pineal gland
• Release is controlled by light/dark cycles
• Function relates to biological rhythms (reproduction, seasonal cycles)