Endocrine

Question 1

Hormones

Answer 1

• hormones are released into the blood
• chemical messengers that change metabolic activity of another cell
• cells with receptors are target cells/target organs

Question 2

Protein (peptide) hormones

Answer 2

• formed from chains of amino acids
• Ex: growth hormone

Question 3

Biogenic amines (amino acid derivatives)

Answer 3

• formed by altering the structure of a specific amino acid
• ex: thyroid hormones

Question 4

Steroid hormones

Answer 4

• type of lipid derived from cholesterol
• ex: estrogen, testosterone, cortisol

Question 5

What do the nervous and endocrine systems do?

Answer 5

• work together to regulate homeostasis
• both affect specific target cells using chemical messengers
• chemical messengers: chem that goes from one part of the body to another

Question 6

Nervous System Only

Answer 6

• uses nerve impulses along axons to reach target
• rapid response to stimulus
• localized, specific effects (ex: a specific muscle contracts)
• response lasts a short time (milliseconds)
  > ex: contracting and the deconstructing muscles

Question 7

Endocrine System Only

Answer 7

• uses hormones that are transported via blood to their targets
• relatively slow response
• widespread effects throughout body (ex: testosterone affects facial hair, acne, muscle growth, sexual response, etc)
• response lasts longer time (minutes, days, weeks…)

Question 8

Negative Feedbacks Loops

Answer 8

• hypothalamus detects low levels of hormone
• hypothalamus tells pituitary to fix low levels
• pituitary tells organ to produce hormone
• organ produces hormone
• now there’s enough hormone in the blood
• hypothalamus detects enough hormone in blood

Question 9

Positive Feedback Loop

Answer 9

• initial stimulus to endocrine system
• pituitary releases hormone
• hormone affects target
• prescience of hormone acts as stimulus to release more hormone

Question 10

The Hypothalamus

Answer 10

• “control center” of endocrine system
• the hypothalamus regulates endocrine system in 3 ways:
  
  1. Signals to anterior pituitary
  2. Signals to posterior pituitary
  3. Direct stimulation of adrenal cortex —> part of adrenal
     glands

Question 11

The Pituitary (Hypophysis)

Answer 11

• pituitary located in sella turcica of sphenoid bone
• anterior pituitary (adenohypophysis) :extensive vascular network, secretes 7 hormones in response to regulatory hormones secreted by the hypothalamus
• posterior pituitary (neurohypophysis): secretes only two hormones
• connected to the hypothalamus by infundibulum

Question 12

Hypothalamus to Anterior Pituitary

Answer 12

• hypothalamus secretes regulatory hormones
  > turn on, turn off and they regulate
• regulatory hormones stimulate anterior pituitary to secrete seven different hormones
  Seven Hormones:
  1. Thyroid stimulating hormone (TSH)
  2. Adrenocorticotropic hormone (ACTH)
  3. Follicle stimulating hormone (FSH)
  4. Luteinizing hormone (LH)
  5. Prolactin (PRL)
  6. Growth hormone (GH)
  7. Melanocyte stimulating hormone (MSH)

Question 13

hypothalamus to posterior pituitary

Answer 13

• neurons from hypothalamus stimulate cells in posterior pituitary
• posterior pituitary releases
  
  1. Vasopressin: restricts water loss in kidneys
  2. Oxytocin: involved in uterine contraction during birth, sexual response, milk ejection reflex

Question 14

Thyroid Gland

Answer 14

• two lobes connected by an isthmus (butterfly-shaped)
• anterior to trachea
• extensive blood supply (very vulnerable in surgery)

Question 15

How does the thyroid gland work?

Answer 15

• hypothalamus releases regulatory hormone to anterior pituitary
• anterior pituitary releases thyroid stimulating hormone (TSH)
• TSH stimulates thyroid to release T3 and T4 (thyroid hormones)

Question 16

Thyroid gland histology

Answer 16

• thyroid follicles lined by follicular cells
• follicular cells secrete T3 and T4
  > influence metabolic rate and protein synthesis
  > widespread targets (gut, heart)
• parafollicular cells release calcitonin, which regulates calcium homeostasis

Question 17

Parathyroid Glands

Answer 17

• four small glands located on posterior aspect of thyroid gland

Question 18

How parathyroid glands work?

Answer 18

• low blood calcium
• stimulates chief cells in parathyroid glands to release parathyroid hormone
• targets: increased osteoclast activity, kidney retains calcium

Question 19

Suprarenal glands

Answer 19

• attached to superior aspect of kidneys
• divided into suprarenal cortex and suprarenal medulla

Question 20

Suprarenal Glands: Suprarenal Cortex

Answer 20

• secretes 24 different corticosteroids, divided into:
• mineralocorticoids: influence electrolyte composition (ex: aldosterone targets kidneys to fine tune electrolytes)
• glucocorticoids: influence glucose metabolism (ex: cortisol targets liver to convert glycogen to glucose)

Question 21

How suprarenal cortex works?

Answer 21

• hypothalamus releases RH to anterior pituitary
• anterior pituitary releases adrenocotropic hormone (ACTH)
• ACTH stimulates release corticosteroids from adrenal gland

Question 22

Suprarenal Glands: Suprarenal Medulla

Answer 22

• cells suprarenal medulla resemble sympathetic ganglia
• innervated by preganglionic sympathetic fibers (axons)
• secrete epinephrine and norepinephrine
• effects are similar to “activation” but last longer
• takes a min to calm down bc suprarenal medulla has released cortisol —> floating around in the blood

Question 23

How does the suprarenal medulla work?

Answer 23

• hypothalamus directly innervates suprarenal medulla with preganglionic sympathetics
• adrenal medulla secretes epinephrine and norepinephrine to widespread target s

Question 24

Pancreas

Answer 24

• mixed gland in abdominal cavity with:
  > exocrine parts that secrete digestive juices
  > endocrine parts that secrete hormones

Question 25

alpha cells of the pancreas

Answer 25

• produce glucagon
• raises blood glucose
• targets liver to initiate glucogenesis
• if you have too little blood sugar

Question 26

Beta cells of pancreas

Answer 26

• produce insulin
• decreases blood glucose
• targets liver, skeletal muscle, adipose tissue to increase uptake of glucose by cells
• too much blood sugar

Question 27

How does it work if the blood glucose is too low?

Answer 27

• stimulates pancreatic alpha cells to release glucagon
• targets liver to begin process of gluconeogenesis (makes glucose)

Question 28

How does it work if the blood glucose is too high?

Answer 28

• stimulates pancreatic beta cells to release insulin
• targets liver, skeletal muscle, adipose tissue to increase glucose uptake

Question 29

Testis

Answer 29

• interstitial cells of the testis produce androgens
• androgens (ex: testosterone) have widespread effects (ex: facial hair, sexual function, muscular development, etc)

Question 30

How do the testis work?

Answer 30

• hypothalamus releases RH to anterior pituitary
• anterior pituitary releases luteinizing hormone (LH) and follicle stimulating hormone (FSH)
• LH stimulates production of androgens
• FSH stimulates development of sperm

Question 31

Ovary

Answer 31

• follicle cells surround oocytes and produce estrogen
• follicle cells merge w/ ovary and then ovulation happens
• after ovulation, follicular cells form corpus lutem, which produces progesterone

Question 32

How does it work for the ovary with FSH?

Answer 32

• hypothalamus releases RH to anterior pituitary
• anterior pituitary releases follicle stimulating hormone (FSH)
• FSH stimulates estrogen secretion: growth of ovarian follicle, maturation of oocyte, growth of uterine lining

Question 33

How does it work for the ovary with luteinizing hormone?

Answer 33

• hypothalamus releases RH to anterior pituitary
• anterior pituitary releases luteinizing hormone
• LH stimulates ovulation
  > LH stimulates progesterone secretion by corpus luteum:
  lining of uterus shifts to secretory phase