Ch 17/18

Question 1

What are the classes of chemical messengers?

Answer 1

Autocrine chemical messengers: released by cells and have a local effect on same cell type from which chemical signals released

Paracrine chemical messengers:
Released by cells and affect other cell types locally without being transported in blood

Neurotransmitter: produced by neurons and secreted into extracellular spaces by pre synaptic nerve terminals

Endocrine chemical messengers: type of intercellular signal. Produced by cells of endocrine glands, enter circulatory system

Question 2

Characteristics of the endocrine system:

Answer 2

• glands that secrete chemical messengers ( hormones) into circulatory system
• hormone characteristics
  
  • produced in small quantities
  • secreted into intercellular space
  • transported some distance in circulatory system
  • acts on target tissue elsewhere in body
• regulates activities of body structure
• ligands: more general term for chemical signals

Question 3

Comparison of nervous & endocrine system:

Answer 3

1. Both systems associated with the brain
   
   • hypothalamus
   • epithalamus
2. May use same chemical messengers as neurotransmitters and hormone
   * epinephrine
3. Two systems are cooperative
   
   • nervous system secretes neuroendocrine peptides, or neurohormones, into circulatory system

Question 4

General characteristics of hormones

Answer 4

1. Stability
   
   • half life: the length of time it takes for half a dose of substance to be eliminated from circulatory system
   • long life: regulates activities that remain at a constant rate through time
   • short half life: have a rapid onset and short duration
2. Communication :
   
   • interaction with target cell
3. Distribution :
   
   • hormones dissolve in blood plasma
   • hormones are distributed quickly because they circulate in blood

Question 5

Patterns of hormone secretion

Answer 5

• Chronic hormone regulation: maintenance of relatively constant concentration of hormone. Thyroid hormone.
• Acute hormone regulation: epinephrine in response to stress
• Episodic hormone regulation : female reproductive hormones

Question 6

Control of hormone secretion:

Answer 6

• most hormones controlled by negative feedback systems

- most hormones are not secreted at a constant rate

Question 7

Negative feedback:

Answer 7

1. Anterior pituitary secretes tropic hormone, travels in blood to target endocrine cell
2. Hormone from target endocrine cell travels to its target
3. Hormone from target endocrine cell has a negative feedback effect on anterior pituitary & hypothalamus and decreases secretion of tropic hormone

Question 8

Positive feedback:

Answer 8

1. Anterior pituitary secreted tropic hormone, travels in the blood to target endocrine cell
2. Hormone from the target endocrine cell travels to target
3. Hormone from target endocrine cell also has a positive feedback effect on the anterior pituitary and increases secretion of tropic hormone

Question 9

Overview of the endocrine system

Answer 9

1. Metabolism
2. Control of food intake and digestion
3. tissue maturation
4. Ion regulation
5. H20 balance
6. Heart rate and blood pressure regulation
7. Control of blood glucose and other nutrients
8. Control of reproductive functions
9. Uterine contractions and milk release
10. Immune system regulation

Question 10

Pituitary gland and hypothalamus

Answer 10

• where nervous and endocrine systems interact
• hypothalamus regulates secretions of anterior pituitary
• posterior pituitary is an extension of the hypothalamus
• anterior pituitary produce nine major hormones that :
  
  • regulate body functions
  • regulate the secretion of other endocrine glands

Question 11

Hormones of posterior pituitary ADH

Answer 11

• osmoreceptors : specialized neurons of hypothalamus monitor changes in intercellular osmolality. If the concentration of electrolytes increases or if the concentration of H20 decreases, then ADH secretion is stimulated
• Baroreceptors: specialized neurons found in walls of atria of heart, large veins, carotid arteries. If BP decreases then ADH secretion is stimulated

Question 12

Anterior pituitary hormones

Answer 12

• growth hormones (GH)
• thyroid - stimulating hormone ( TSH)
• adrenocorticotropic hormone (ACTH)
• melanocyte- stimulating hormone (MSH)
• beta endorphins
• lipotropins
• luteinizing hormone (LH)
• follicle stimulating hormone (FSH)
• prolactin

Question 13

Growth hormone

Answer 13

• stimulates uptake of amino acids; protein synthesis
• stimulates breakdown of fats to be used as an energy source but stimulates synthesis of glycogen
• promotes bone and cartilage growth
• regulates blood levels after meals

Question 14

Growth hormone stimulation

Answer 14

• • functions in regulation growth, tissue maintenance and metabolism

Question 15

Growth hormone inhibition

Answer 15

• hypothalamus produces growth hormone inhibiting hormone
• inhibits production of GH by anterior pituitary
• GHRH secretion in response to low blood glucose , stress
• GHIH secretions in response to high blood glucose

Question 16

TSH and thyroid hormone

Answer 16

• TRH from hypothalamus causes releases of TSH from anterior pituitary which causes secretion and storage of hormones T3 and T4

Question 17

Thyroid gland

Answer 17

• one of the largest endocrine glands
• highly vascular
• iodine enters follicular cells by active transport
• only gland that stores hormone

Question 18

Parathyroid glands

Answer 18

• embedded in thyroid
• two glands on each side
• secrete PTH: target tissues are bone, kidneys and intestines
• regulation depends on calcium levels

Question 19

Adrenal glands

Answer 19

• near superior poles of kidneys
• inner medulla; outer cortex
• medulla : secretes epinephrine and norepinephrine
• cortex : 3 zones from superficial to deep
  
  • zona glomerulosa
  • zona fasciculata
  • zona reticularis

Question 20

Hormones of the adrenal medulla

Answer 20

• secretory products are neuropeptides: epinephrine and norepinephrine
• epinephrine increases blood levels of glucose, increases fat breakdown in adipose tissue, cause dilation of blood vessels in skeletal muscles and cardiac muscles

Epinephrine and norepinephrine increase heart rate and force contraction; cause blood vessels to constrict in skin, kidneys, gastrointestinal tract

Question 21

Hormones of adrenal cortex

Answer 21

• Mineralocorticoids
• Glucocorticoids
• Androgens

Question 22

Pancreas

Answer 22

• located along small intestine and stomach
• exocrine gland ( produces pancreatic digestive juices )
• endocrine gland
  ( consists of pancreatic islets and composed of:
  Alpha cells - secrete glucagon
  Beta cells- secrete insulin
  Delta cells- secrete somatostatin- pancreas blocking insulin and glucagon

Question 23

Hormones of the reproductive system

Answer 23

Testes:

• testosterone - development of genitalia, maintenance of functional reproductive organs
• inhibin- inhibits FSH secretion

Ovaries:

• estrogen- Aids in uterine and mammary gland development and function, maturation of genitalia and menstrual cycle
  * progesterone : same as ^^
  * inhibin : inhibits FSH secretion
  
  • relaxin : increases the flexibility of connective tissue in pelvic area

Question 24

Other hormones and chemical messengers

Answer 24

• thymus gland, G1 tract :
  
  • thymosin.Development of the immune system
  • G1 tract: several hormones regulate digestion and enzyme secretion

Question 25

Hormone like chemicals

Answer 25

- autocrines: chemical signals released by a cell and the substance affects that same cell - paracrines: chemical signals released into intercellular fluid and affecting nearby cells

Question 26

Effects of aging on endocrine system

Answer 26

- gradual decrease in secretory activity of some glands * GH as people age except in people who exercise regularly * melatonin * thyroid hormones * kidneys secrete less renin - familial tendency to develop type 2 diabetes