The Nervous System & The Endocrine System: Year 8 Biology Final Exam Summary

2.2 Glands of the Endocrine System

The Human Endocrine System
Pituitary Gland
> Bean sized structure that dangles on a slendee stalk of tissue at the base of the brain.
> Divided to two parts: anterior and posterior.
> Secretes hormones that directly regulate many bodily functions or control the actions of other endocrine glands.
> Too much GH (growth hormone): gigantism.
> Too little GH: dwarfism.

Hypothalamus
> Attached to posterior pituitary, link between CNS and endocrine system.
> Controls the secretions of the pituitary gland.
> Activities are influenced by levels of hormones and other substances in the blood and sensory info.
> Contains cell bodies of neurosecretory cells whose axons extend into the posterior pituitary.
> Antidiuretic hormone (stimulates kidney to absord water), oxytocin (stimulates contractions during childbirths) are made in the cell bodies of the hypothalamus and stored in axons entering the posterior pituitary.
> When the cell bodies are stimulated, axons in the posterior pituitary release these hormones in the blood.

Anterior Pituitary Hormones
1. Follicle-stimulating hormone (FSH)
Stimulates production of mature eggs in ovaries and sperm in testes.
2. Luteinizing hormone (LH)
Stimulates ovaries and testes; prepare uterus for implantation of fertelized agg.
3. Thyroid-stimulating hormone (TSH)
Stimulates the synthesis and release of thyroxine from the thyroid gland.
4. Adreno-corticotropic hormone (ACTH)
Stimulates release of some hormones from the adrenal cortex.
5. Growth hormone (GH)
Stimulates protein synthesis and groth in cells.
6. Melanocyte-stimulating hormone (MSH)
Stimulates melanocytes in the skin to increase the production of the pigment melanin.
7. Prolactin
Stimulates milk production in nursing mothers.

> In contrast, hypothalamus has indirect control of the anterior pituitary.
> Hypothalamus produces releasing hormones which are secretes into blood vessels leading to the anterior pituitary.
> The hypothalamus controls the secretion of a specific releasing hormone that control the secretion of each anterior pituitary hormones.

Adrenal Glands
> Release hormone that help the body prepare for and deal with stress.
> Outer: adrenal cortex (bc cortex means skin i think), inner: adrenal medulla. But 80% is the cortex.
> Cortex produces more than two dozen steroid hormones called corticosteroids.
> One of them: aldosterone: regulates blood volume and pressure. Its release is stimulated by dehydration, excessive bleeding, or Na+ deficiency.
> Cortisol: helps control the rate of metabolism of carbohydrates, fats, and proteins. Released during physical stress such as exercise.
> Hormones released from the adrenal medulla produces the heartpounding, anxious feeling/ "fight or flight" response.
> Sympathetic nervous system stimulate cells in the adrenal medulla to release amounts of epinephrine (adrenaline) and norepinephrine.
> These increase heart rate and blood pressure. Cause airways to widen, increasing oxygen intake, stimulate release of extra glucose.

Pancreas
> Both an exocrine and endocrine gkand.
> Exocrine: release digestive enzymes that help break down food.
> Endocrine: consists of clusters of cells, resembling islands, "islets of Langerhans"– German anatomist Paul Langerhans.
> Each islet contains beta cells (secretes insulin) and alpha cells (secretes glucagon). Both help keep blood glucose level stable.

Blood Glucose Regulation
> When blood glucose level rise after a person eats, the pancreas releases insulin.
> Insulin stimulates cells to take glucose out of blood. Major target cells: liver, skeletal muscles, and fat tissues.
> Liver and skeletal muscles store glucose as glycogen. In fat tissue, glucose is converted to lipids.
> 1 or 2 hours after, the level of glucose drops, glucagon is released from the pancreas.
> Stimulates the liver and skeletal muscles to break down glucogen and release glucose into the blood.
> Also cause fat cells to break down fats to be converted to gkucose.

Diabetes Mellitus
> When body fails to produce or properly respond to insulin.
> Very high blood glucose levels can damage almost every system and cell in the body.
> Two types: Type I– autoimmune disorder, usually develops in people before the age of 15. Kills beta cells, little or no insulin. Strict diet and receive daily doses of insulin.
> Type II: develops in people after the age 40. Produce low to normal amounts of insulin. But the cells do not respond properly because the interaction of insulin receptors and insulin is inefficient. In early stages, can be controlled through diet and exercise.