Physiology 14: Hypothalamus & Pituitary Gland

In central brain circuitry the hypothalamus…

regulates motivation

In pituitary/systemic the hypothalamus…

regulates hormones

How does Hypothalamic control of of the Anterior Pituitary work?

1. Hypothalamus secretes hormones into the portal circulation.

2. Hormones travel through the median eminence (small blood vessels) and transports signals to the anterior pituitary.

3. The hormones either stimulate or inhibit the release of hormones from the anterior pituitary.

What are the anterior pituitary cell types?

• PRL- Prolactin (takes up 10-30%)

• GH- Growth Hormone (takes up 45-50%)

• ACTH- Adrenocorticotropin (takes up 20-20%)

• TSH- Thyroid-stimulating Hormone (takes up 5%)

• LH- Lutenizing Hormone

• FSH- Follicle-stimulating Hormone

What is the function of the prolactin (PRL) hormone?

• Milk production

What is the function of the Growth hormone (GH)?

• Growth

• Metabolism

What is the function of the Adrenocorticotropin (ACTH) hormone?

• Stimulates the adrenal cortex (cortisol)

What is the function of the Thyroid-stimulating hormone (TSH)?

• Stimulates thyroid hormone release

What is the function of the Lutenizing hormone (LH)?

• Stimulates sex hormone production

What is the function of the Follicle-stimulating hormone (FSH)?

• Secreted via gonadotrophs that are scattered throughout the anterior pituitary

• Stimulates egg/sperm production

What hormones are Controlled by the Hypothalamus?

• Prolactin-releasing hormone (PRH)- Dopamine (PRL)

• Growth Hormone-Releasing Hormone (GHRH)- Somatostatin (GH)

• Corticotropin-Releasing Hormone (CRH)-(ACTH)

• Thyrotropin-Releasing Hormone (TRH)- (TSH)

• Gonadotropin-Releasing Hormone (GnRH)- (LH & FSH)

What anterior pituitary cell has the hypothalamic factor CRH?

• Corticotrophs

What anterior pituitary cell has the hypothalamic factor TRH?

• Thyrotrophs

What anterior pituitary cell has the hypothalamic factor GnRH?

• Gonadotrophs

What anterior pituitary cell has the hypothalamic factor GHRH?

• Somatotrophs

What anterior pituitary cell has the hypothalamic factor dopamine?

• Lactotrophs

What pituitary hormone does CRH produce?

• ACTH

• Beta-endorphin

What pituitary hormone does TRH produce?

• TSH

What pituitary hormone does GnRH produce?

• LH

• FSH

What pituitary hormone does GHRH produce?

• Growth Hormone

What pituitary hormone does dopamine produce?

• Prolactin

How does Hypothalamic control of of the Posterior Pituitary work?

Hypothalamic neurons send hormones to the pituitary gland ➡ hormones are released into the bloodstream.

1. Hypothalamus produces hormones (oxytocin & vasopressin)

2. Hormones travel along axons to the posterior pituitary gland

3. Posterior pituitary stores and releases the hormones into the bloodstream

4. The hormones affect the thyroid, adrenal, gonads

Oxytocin & Vasopressin…

are made in the hypothalamus & released into the posterior pituitary gland

What kind of hormone is vasopressin?

Anti-Diuretic Hormone (ADH)

What are the target organs or cells of the hormone: Oxytocin?

• Uterus

• Mammary gland

• Myoepithelial cells

What are the target organs or cells of the hormone: Vasopressin?

• Smooth Muscle Cells (V1R)

• Kidney Collecting Ducts (V2R)

What are the physiological effects of the hormone: Vasopressin?

• Vasoconstriction EX: stretching of the cervix in labor

• Increased water retention

What are the physiological effects of the hormone: Oxytocin

• Uterine Contraction EX: Childbirth

• Milk Ejection EX: Breastfeeding

What mechanical stimulus is a result of Systemic oxytocin release into the bloodstream?

• Stretch of cervix at the end of pregnancy (to hypothalamus)

• Breastfeeding/ Breast Pumping (to hypothalamus)

Oxytocin increases _____ contraction, uterus, and breast tissue

• smooth muscle

What is the process of Oxytocin increasing cellular calcium levels?

The myosin light chain kinase serves as a bridge between Increased calcium levels & muscle contraction

1. Oxytocin increases intracellular calcium levels

2. Pathway activates (signaling pathways) and leads to the release of calcium (Ca2+) from intracellular

3. This elevated calcium lands to calmodulin

4. Myosin Light Chain Kinase (MLCK) activates

5. Myosin phosphorylates

6. Muscle contraction occurs

Physiological Modulation can be defined as…

changing the way a physical process functions

What are the two outcomes of Physiological Modulation of Oxytocin Release?

• Increase in Oxytocin release

• Inhibited Oxytocin release

What factors cause an Increase in Oxytocin Release?

• Feeling secure

• Privacy

• Dim lighting

• People you know

• Touch

• Comfortable environment

• Relaxation

What factors cause an Inhibited Oxytocin Release?

• Feeling frightened

• Feeling watched

• Bright lights

• Strangers

• Questions

• Uncomfortable environment

• Thinking

What is the Hypothalamic Response to Low Vascular Tone (Lower blood pressure and poor tissue oxygenation?

Loss of Vasculature Baroreceptor Stimulation leads to Vasopressin release & vasoconstriction to increase blood pressure

1. Low BP (homeostasis is disturbed)

2. Decreased baroreceptor stimulation in vasculature (Baroreceptor reflex)

3. Hypothalamus is stimulated

4. Increased vasopressin is released into the bloodstream

5. Increased vasoconstriction (blood vessels narrow) via smooth muscle contraction

6. Increased BP

7. Homeostasis is restored (normotensive)

What is the Hypothalamic Response to Dehydration?

Increased Blood Plasma Osmolarity is detected by Hypothalamic (brain) Osmoreceptors.

1. Dehydration (homeostasis is disturbed)

2. Increased sodium concentration in ECF

3. Osmoreceptors are stimulated

4. Increased vasopressin release & increased thirst

5. Decreased urinary water loss & Increased water gain

6. Additional water dilutes ECF & volume increased

7. Homeostasis is restored. Normal ECF and Sodium concentration

What are Aquaporins?

• Water channels

Vasopressins increases the level of aquaporins in the _____

kidneys to retain water

Vasopressin release is stimulated by…

• Baroreceptors (Low BP)

• Osmoreceptors (High Blood Salt levels)

What are the effects of vasopressin release?

• Increased vascular resistance

• Increases aquaporins in the kidneys ➡ reabsorbed water ➡ Less Urine Output

• Increased blood pressure

• Increased blood volume

The hypothalamus is defined as…

The hypothalamus is an area of the brain that produces hormones that control:

Body temperature. Heart rate. Hunger.

The pituitary gland is defined as…

Organ attached to the part of the brain called the hypothalamus. The hypothalamus sends signals to the pituitary gland, which then makes hormones that control other glands and many of the body's functions, including growth and fertility.