Lecture 4- Endocrine System

Question 1

Pituitary Gland

Answer 1

• Also called HYPOPHYSIS

- located at the base of the brain, in the pocket of the sphenoid bone just below the hypothalamus

Question 2

What are the two main regions of the pituitary gland?

Answer 2

1. Anterior pituitary (adenophypophysis)
2. Posterior pituitary (Neurohypophysis)
   - These regions are anatomically and functionally different

Question 3

Anterior Pituitary Lobes

Answer 3

1. Para tuberalis–> upper lope, surrounds the infundibulum
2. Pars intermedia–> intermediate lobe, minimal function in humans
3. Pars disalis–> anterior lobe, Large portion, produce specific hormones

Question 4

Posterior Pituitary Anatomy

Answer 4

• Neurons start in the hypothalamus and end in nervosa
  1. Median Eminence (part of the hypothalamus)
  2. Infundibular Stem (contain nerve Tracts from hypothalamus)
  3. Pars Nervosa, also called the neural lobe, contains neurons from hypothalamus

Question 5

Connections between the pituitary gland and hypothalamus

Answer 5

• Neuronal and VASCULAR connection
  1. Hypophyseal tract-Nerves connecting the hypothalamus and the posterior pituitary
  2. Hypophyseal Portal System-blood vessels that connect the hypothalamus with the anterior pituitary.

Question 6

Hypophyseal Portal System

Answer 6

• vascular connection between the hypothalamus and the anterior pituitary
• Plexus is a capillary network
• Anterior hypophyseal veins drain the blood containing hormones into the circulation

Question 7

Hypothalamic Regulation of the Anterior Pituitary

Answer 7

-Hypothalamus produces hormones that are released into the capillaries then go through the veins down into the 2nd plexus in the anterior pituitary, and will either stimulate of inhibit

Question 8

Anterior Pituitary Cells and Their Hormones (5)

Answer 8

1. Somatotropes–> Growth Hormone
2. Corticotropes–> ACTH and MSH
3. Thyrotropes–> Thyroid Stimulating Hormone
4. Lactotropes–> Prolactin
5. Gonadotropes—> Follicle stimulating hormone, Luteinizing Hormone

Question 9

Target Tissues for Anterior Pituitary Hormones

Answer 9

• Hormones act on other endocrine tissues or Systems

- Most hormones are TROPIC-stimulate more hormones

Question 10

Regulation of Hormone Secretion

Answer 10

-Stimulation by the nervous system by hypothalamic releasing hormones
Feedback Mechanism
-Levels of secreted hormones from the pituitary or target organ, can be stimulatory or inhibitory, and can occur at target organs, hypothalamus, or the pituitary

Question 11

Control of ACTH secretion: NEGATIVE feedback

Answer 11

• ACTH (corticotropin) is synthesized ad secreted by Corticotrophs
• tropic hormone
• Often produced with CRH in response to biological stress
• ATCH stimulates glucocorticoid( mainly cortisol) secretion by adrenal gland

Question 12

Growth Hormone: Target Tissues

Answer 12

• protein hormone of 190 amino acids
• Hypothalamus releases GHRH that stimulates somatotrophs to produce and secrete GH
• GH target Tissues: Liver, muscle, bone, and adipose tissue
• GH stimulates growth in most tissues and regulates METABOLISM

Question 13

GH Direct Effects: Mechanism

Answer 13

-GH binds to its receptor on target cells in target tissues

Question 14

GH direct Effects on Tissues

Answer 14

-Somatomedins–> hormones that protect cell growth and division in response to stimulations by growth hormone

Effects on Liver

1. increased Protein synthesis
2. increase gluconegenesis(synthesis of glucose_
3. Promotes secretion of somatomedins

Effects on adipose tissue

1. decrease glucose uptake
2. Increase lipolysis (fat breakdown)
3. decrease fat storage

Effect on Muscle

1. Increase amino acid uptake
2. decrease glucose uptake
3. increase muscle mass
4. increase protein synthesis