15 Endocrine System

Question 1

Endocrine System

Answer 1

secrete their products (hormones) directly into the blood which carries them throughout the body to specific target cells

Question 2

Endocrine System Response

Answer 2

Causes a slow but prolonged response (versus the nervous system which is fast, short reponse)

Question 3

Hormones

Answer 3

Chemical signals that allow communication between different cells, body parts and even other animals - usually act at a distance

Question 4

Peptide hormone

Answer 4

proteins that bind to receptors in plasma membranes causing the formation of cAMP which activates a cascade of enzymes in the cells

Question 5

Steroid hormones

Answer 5

lipids that enter the cell nucleus and affect gene activity (and thus protein synthesis)

Question 6

Prostaglandins (hormones)

Answer 6

local hormones that affect neighboring cells and thus are not carried in the bloodstream

Question 7

Pheromones (hormones)

Answer 7

a chemical hormone signals that pass between and influence behavior of other animals

Question 8

Action of Peptide Hormones

Answer 8

1. hormone binds to receptor on plasma membrane
2. binding leads to activation of enzymes, changes ATP to cAMP
3. cAMP activates enzyme cascade
4. many molecules of glycogen are broken down and enter the blood stream

Question 9

Action of Steroid HOrmones

Answer 9

lipids from adrenal cortex, ovaries, testis - include aldosterone, testosterone and estrogen

As lipids, they pass through cell membrane and bind to intranuclear receptors - not to membrane receptors

1. Hormone diffuses through plasma membrane (lipid solute)
2. hormone binds to receptor inside nucleus
3. hormone receptor activates synthesis of mRNA
4. mRNA moves to ribosomes and protein synthesis occurs

Question 10

Hypothalamus

Answer 10

located at the base of the brain, regulates internal environment through the autonomic nervous system

• helps control hearbeat, body temp, water balance, controls glandular secretions of pituitary

Question 11

Posterior Pituitary Gland

Answer 11

Stores ADH (antidiuretic hormone) and oxytocin that are produced by the hypothalamus (gets to posterior via axons)

Question 12

ADH

Answer 12

antidiuretic hormone

regulates water balance by reabsorbing water from the renal filtrate in tubule back into bloodstream at the kidney

Question 13

Oxytocin

Answer 13

causes uterine contractions during childbirth and allows milk to be released from breast during nursing

Question 14

Anterior Pituitary Gland

Answer 14

Controlled by hypothalamic-releasing and inhibiting hormones (e.g. thyroid releasing and inhibiting hormones) via a portal system (2 capillary beds connected by a vein) and frequently uses negative feedback homeostasis

• Six hormones produced by the anterior pituitary:
1. Thyroid-stimulating hormone (TSH): stimulates the thyroid
to produce thyroid hormones
2. Adrenocorticotropic hormone (ACTH): stimulates the adrenal cortex to produce cortisol
3. Gonadotropic hormones: Folicle Stimulating and Leutenizing Hormones (FSH and LH) stimulate gonads (ovary and testicle) to produce sex cells and sex hormones
4. Prolactin (PRL): stimulates mammary glands to develop and produce milk only after childbirth
5. Melanocyte-stimulating hormone (MSH): causes skin cells to produce melanin
6. Growth hormone (GH): promotes skeletal and muscular growth

Question 15

Too little or too much growth hormones?

Answer 15

• Pituitarydwarfism–toolittleGHproduced
during childhood results in small stature

• Gigantism–toomuchGHproduced during childhood results in large stature but poor health
• Acromegaly–overproductionofGHasan adult results in larger than normal feet, hands, and face

Question 16

Thyroid Gland

Answer 16

• Alargeglandinnecklocatedbelowthe larynx
• Dietaryiodineneededbythethyroidto produce its hormones

• Thyroid produces:
– Thyroxine (T4) and Triiodothyronine
(T3): both regulate metabolism
– Calcitonin: helps lower blood Calcium levels by stimulating the deposition of calcium in bones

Question 17

Thyroid Abnormalities

Answer 17

Simple goiter – thyroid enlarges because of increased TSH from Ant. Pituitary, due to lack of iodine in the diet (causing not enough thyroid hormones T3 and T4)

•_ Hypothyroidism_ – low blood levels of thyroid hormonesA. Congenital hypothyroidism: A child’s thyroid does not develop properly - characterized by a short, stocky person that may be mentally retardedB. Myxedema: hypothyroidism in adults characterized by lethargy, weight gain, loss of hair, cold intolerance and thick, puffy skin

• Hyperthyroidism – excess thyroid hormones in the blood
A. Exophthalmic goiter: such as seen in Graves’ disease - is characterized by enlargement of the thyroid gland, protrusion of the eyes, hyperactivity and insomnia
B. Thyroid tumor: can also cause hyperthyroidism

Question 18

Parathyroid Glands

Answer 18

• Usuallyfoursmallglandsembeddedinor near the surface of the thyroid gland

• Produceparathyroidhormone(PTH):
– causes blood calcium level to increase by promoting osteoclast activity to break down bones (releasing calcium)
– Promotes reabsorption of calcium by the kidneys

Question 19

Adrenal Glands

Answer 19

Adrenals have two parts
– Adrenal medulla: inner portion, controlled by the
nervous system
– Adrenal cortex: outer portion, controlled by adrenocorticotrophic hormone (ACTH) from the anterior pituitary gland

Question 20

Adrenal Medulla

Answer 20

• Innerportionoftheadrenalglands
• Vianeurons(nothormones),thehypothalamus stimulates the adrenal medulla to produce its
own hormones that allow a rapid, (but not as fast as neural) short-term response to stress: This is termed “Fight or flight”

– Epinephrine (adrenaline)

– Norepinephrine

Question 21

Adrenal Cortex

Answer 21

• Outer portion of the adrenal glands
• Stimulated by ACTH (hormone) from anterior pituitary, adrenal cortex produces its own hormones that provide a slow but long-term response to stress

Mineralocorticoids : regulate salt and water balance • e.g. aldosterone (reabsorbs Na+ at the kidney)

Glucocorticoids : regulate carbohydrate, protein and fat metabolism, e.g. cortisol and cortisone
• Promote breakdown of muscle protein to amino acids, which liver converts to glucose, and increases metabolism of fatty acids, sparing glucose
• Suppresses the body’s inflammatory response

Question 22

Adrenal Gland Malfuction

Answer 22

Addison’s disease – hyposecretion of glucocorticoids
by the adrenal cortex causes “bronzing” of the skin

Question 23

Pancreas

Answer 23

Composed of 2 separate tissues:

– Exocrine: produces and secretes digestive juices via duct into duodenum (amylase, lipase, trypsin, etc.)

– Endocrine: (islets of Langerhans): produces and secretes hormones into blood

1. Insulin – secreted when blood glucose is too high - stimulates uptake of glucose by muscle and liver cells (which lowers blood glucose)
2. Glucagon – secreted when blood glucose is too low - stimulates the breakdown of glycogen in the liver to glucose (which raises blood glucose

Question 24

What is diabetes mellitus?

Answer 24

Inability to control blood glucose levels

• Two types: Type 1 and Type 2 (used to be called Juvenile and Adult Onset Diabetes, but now so many overweight kids have “adult onset,” the names had to be changed!)

• 20 million people in the US have diabetes – up to 100 million are at risk of getting it (nearly 1/3 US population)
• General symptoms:
– Frequent urination
– Unusual hunger and/or thirst
– Unexplained change in weight
– Blurred vision
– Sores that heal slowly or not at all – Excessive fatigue

Long-term effects all caused by vascular disease (atherosclerosis): blindness, loss of limbs, nerve
deterioration, kidney failure, heart disease.

Question 25

Type 1 Diabetes

Answer 25

• usually early-onset
• likely an autoimmune disorder that tends to run in families
• pancreatic islet cells are attacked and they cannot produce insulin
• treated with insulin injections

Question 26

Type 2 Diabetes

Answer 26

• usually adult-onset and is most common type
• tends to occur in obese, sedentary people
• muscle and fat cells do not respond to insulin
• diet and exercise can control and may prevent type 2 by decreasing weight
• usually treated with oral meds, diet and exercise

Question 27

Testes

Answer 27

• Male gonads
• Produce male sex hormones, (e.g. testosterone)

• Gonadotropin Releasing Hormone (GnRH) from hypothalamus stimulates anterior pituitary output of Folicle Stimulating Hormone (FSH) and Leutinizing Hormone (LH). LH then stimulate testes to make Testosterone, that in turn:
– Stimulates growth of the penis and testes
– Causes male secondary sex characteristics such
as facial, underarm and pubic hair
– Prompts the larynx and vocal cords to enlarge, resulting in a lower-pitched voice
– Promotes muscular strength

Question 28

Ovaries

Answer 28

• Female gonads
• Produce female sex hormones

GnRH from hypothalamus stimulates FSH and LH from anterior pituitary, causing ovaries to produce
estrogen and progesterone, which in turn:
– Stimulate growth of the vagina and uterus
– Cause development of female secondary sex characteristics such as body hair, fat distribution and breast development
– Are responsible for egg maturation in ovaries
– Regulate the uterine cycle

Question 29

Thymus

Answer 29

• Lies beneath the sternum in upper chest
• Largest and most active during childhood
• T- lymphocytes mature here
• Secretes hormones called thymosins that aid in differentiation of lymphocytes

Question 30

Pineal

Answer 30

• located at base of brain
• secretes melatonin that regulates sleep/wake cycle (circadian rhythm)
• may also regulate sexual development

Question 31

Homeostasis

Answer 31

• the nervous and endocrine systems are important in maintaining homeostasis

– The hypothalamus bridges regulatory functions of both systems

– The nervous and endocrine systems are able to respond to changes in the external environment