Endocrine System Flashcards
What is the endocrine system composed of?
ductless glands that secrete chemical messengers called hormones into the blood stream.
What are hormones?
Chemical messengers produced by specialized cells that exert their effects on distant parts of the body.
What does a hormone do?
Regulate the rates of specific metabolic reactions - usually by regulation of enzyme activity.
What are some facts about Hormones?
- They are required in very small amounts
- May be excitatory or inhibitory
- Informational molecules that only work on cells that have the receptors to bind them
What glands are included in the normal endocrine system?
One pituitary gland
One thyroid gland
Four parathyroid glands
Two adrenal glands
One pancreas
One thymus
One pineal gland
Two gonads
What is the ‘Master Gland’ that controls other endocrine glands throughout the body?
The Pituitary Gland, which is controlled by the hypothalamus.
Where is the Pituitary gland located?
At the base of the brain just below the Hypothalamus.
What are the two lobes of the pituitary gland?
The Anterior and Posterior
What is the pituitary connected to?
Connected to the hypothalamus via a stalk; the infundibulum.
What does the anterior pituitary do?
Produces hormones
What does the Posterior Pituitary do?
- Responds to neurological stimulation
- Stores and secretes hormones produced by the hypothalamus
What are the hormones released by the posterior pituitary known as?
Direct-acting hormones because they produce the desired effect directly in the target tissue
True or False? The posterior pituitary produces hormones.
False. The posterior pituitary SECRETES and STORES hormones produced by the hypothalamus but does not create any of its own.
What are hormones secreted from the anterior pituitary called?
Indirect-acting hormones or Tropic hormones
What controls the release or cessation of hormones?
Positive and negative feedback control the levels of most hormones in the blood by secreting, releasing, or inhibiting factors that affect hormone release.
What hormones do the Anterior pituitary gland produce and secrete?
- TSH (Thyroid Stimulating hormone)
- ACTH (Adrenocorticotropic hormone)
- FSH (Follicle-stimulating hormone)
- LH (Luteinizing hormone)
- ICSH (Interstitial cell-stimulating hormone)
- Prolactin
- GH (growth hormone)
- MSH (Melanocyte-stimulating hormone)
Note: You will not be expected to memorize the complete name of the abbreviated hormones.
What hormones do the posterior pituitary gland store and secrete?
- ADH (Antidiuretic hormone)
- Oxytocin
Note: You will not be expected to memorize the complete name of the abbreviated hormones.
What is the Thyroid Gland?
It’s a butterfly-shaped gland located either side of the larynx.
What does the Thyroid Gland consist of?
Secretory cells arranged into rings or follicles surrounding a lumen in which the secretions are stored.
What is the Thyroid Gland controlled by?
Its function is controlled by TSH (Thyroid stimulating hormone) secreted by the anterior pituitary gland.
What does the Thyroid Gland secrete?
- T3 (Triiodothyronine) - regulates metabolism
- T4 (Thyroxine) - Regulates metabolism
- Calcitonin - Promotes absorption of calcium from blood into bones
Note: You are not expected to memorize the full name of the abbreviated hormones.
What are the Parathyroid Glands?
Four glands located on the surface of the thyroid gland.
What do the parathyroid glands secrete?
Parathormone or PTH (Parathyroid hormone)
Note: you are not expected to memorize the full name of the abbreviated hormones.
What does PTH do?
PTH helps to regulate blood calcium levels by mobilizing bone calcium. It also regulates the phosphorus content of the blood.
What are the Adrenal Glands?
Two glands that are located cranial to each kidney that consist of a cortex and medulla.
What do the Adrenal Glands do?
They regulate electrolytes, metabolism, sexual functions, and the body’s response to injury.
What is the Adrenal Cortex? What does it do?
- The outer portion of the Adrenal glands
- Secretes corticosteroids: Mineralocorticoids like aldosterone, Glucocorticoids like cortisol and hydrocortisone, and androgens.
What is the Adrenal Medulla? What does it do?
- Inner portion of Adrenal Glands
- Secretes epinephrine (Adrenaline) and norepinephrine (Noradrenaline). (These are known as catecholamines and act as both hormones and neurotransmitters.)
What is Epinephrine (Adrenaline)?
A vasopressor, which is a substance that stimulates blood vessel contraction and increases blood pressure.
What does Epinephrine (Adrenaline) do?
Stimulates sympathetic nervous system (Fight or Flight system) and increases blood pressure, heart rate, and blood glucose.
What does Norepinephrine (Noradrenaline) do?
Stimulates sympathetic nervous system (Fight or Flight) and increases blood pressure, heart rate, and blood glucose. It is similar in both structure and function to epinephrine.
What does the Pancreas do?
Secretes insulin and Glucagon by specialized cells called Islets of Langerhans.
What is special about the Pancreas?
It has both Exocrine and Endocrine functions.
Where is the Pancreas located?
Near the proximal duodenum.
What does insulin do?
Decreases blood glucose levels by transporting glucose into cells or into storage as glycogen (main storage form of carbohydrate).
What does Glucagon do?
Increases blood glucose levels by breaking down glycogen.
What is the Thymus?
A gland that is predominant in young animals.
Where is the Thymus?
Located near the midline in the cranioventral portion of the thoracic cavity. (The top, hollow portion of the thoracic cavity)
What does the Thymus secrete?
Thymosin.
What does thymosin do?
Augments the maturation of T-lymphocytes.
What does the Pineal Gland do?
Secretes melatonin and controls circadian rhythm and reproductive timing.
Where is the Pineal Gland?
Near the midline in the central portion of the brain.
What are the Gonads?
The gonads are the ovaries in females and the testes in males.
What do the gonads produce?
Gametes (Sex Cells).
What do the ovaries secrete?
Estrogen and Progesterone.
What do the testes secrete?
Testosterone.
