BIO224A: Chapter 16, Endocrine System (Day 2, NO DIAGRAMS)

Calcitonin

produced and secreted by parafollicular cells; decreases blood calcium levels

What must be released when calcium ion level in blood is above normal?

calcitonin

How does calcitonin affect osteoclast activity?

inhibits osteoclast activity allowing osteoblast activity

How does osteoblast activity affect calcium ion levels?

They keep taking calcium out of the blood and using it to build bone, so calcium levels decrease

parathyroid gland

3-5 separate glands on posterior surface of thyroid gland

Where is the parathyroid from?

chief cells

Function of parathyroid hormone

increase blood calcium levels

Calcium ion homeostasis

1.) Para follicular cells secrete CALCITONIN to decrease blood calcium levels

2.) Parathyroid chief cells secrete PARATHYROID HORMONE to increase blood calcium levels

Adrenal glands

superior aspect of each kidney, pyramid shaped; produce catecholamine and steroid

Cortex

subdivided into three distinct zones

steroid hormones are derived from...

cholesterol

Outer zona glomerulosa

densely packed cells; produce mineralocorticoid hormones

middle zona fasciculata

cells stacked on one another in columns; secrete glucocorticoids and androgenic steroids

inner zona reticularis

thin layer of cells arranged loosely in clusters; secrete glucocorticoids and androgenic steroids

medulla

neuroendocrine organ that secretes neurohormones

What are the three distinct zones of the cortex?

outer zona glomerulosa, middle zona fasciculata, inner zona reticularis

What does zona glomerulosa secrete?

aldosterone

Aldosterone disorders

Hyperaldosteronism can lead to

- hypokalemia

- hypernatremia

- hypertension

Hyperaldosteronism

hypersecretion of aldosterone

Hypokalemia

low potassium

hypernatremia

high sodium

hypertension

high blood pressure

Zona fasciculata secretes...

cortisol

Stress response

events that maintain homeostasis when body is faced with stressor; regulation of blood glucose levels by cortisol

Cortisol function

stimulates liver cells to synthesize enzymes of gluconeogenesis

gluconeogenesis

production of new glucose molecules from amino acids and fatty acids

How does gluconeogenesis affect blood glucose levels?

increases blood glucose levels

Besides rising glucose levels, what is the effect of gluconeogenesis on the body?

- induce protein breakdown by releasing free amino acids for glucose conversion

- acts on adipocytes to release fatty acids for fuel/glucose for glucose conversion in the liver

- decreases certain leukocytes, a anti-inflammatory agent

How are cortisol disorders caused?

oversecretion of cortisol or long-term administration ofcorticosteroids

Cushing's disease

oversecretion from adrenal cortex, usually from tumor

Iatrogenic Cushing's syndrome

disorder caused by long-term administration of glucocorticoid-containing drugs

Symptoms of cortisol excess

muscle wasting and sliming of limbs

muscle wasting

the result of the breaking down of proteins in muscle; causes hyperglycemia

hyperglycemia

fats and amino acids converted into glucose

Slight mineralocorticoid effect causes...

hypertension

Effect on leukocytes causes...

immunosuppression

Effect on osteoblast activity and calcium absorption may cause...

osteoporosis

Why do limbs become slim from cortisol excess?

Lipolysis release fatty acids in lower and upper limbs resulting in slim appearance; deposit adipose tissue in TRUNK, FACE, BACK OF NECK

moon facies

round face due to cortisol excess

buffalo hump

hump on back of neck due to cortisol excess

Androgenic steroids

steroid sex hormones that affect GONADS and other tissues

How does the adrenal cortex synthesize hormones?

In small quantities in both genders; mainly by products of cortisol synthesis pathway

How do you change androgenic steroids into other sex hormones?

it can be converted in circulation to androgen testosterone or female hormone estrogen

What can adrenal insufficiency result in?

Addison's disease leading individuals susceptible to adrenal crisis

What is Addison's disease?

hyposecretion of cortisol and mineralocorticoids

What is the result of adrenal crisis?

disruption of fluid, electrolyte, and acid-base homeostasis

What causes adrenal insuffciency?

abnormal development of adrenal gland, deficiency in certain enzymes required to produce steroid hormones, and destruction of adrenal glands by individual’s immune system

Chromaffin cells

derived from nervous tissue; secrete mostly epinephrine

Chromaffin cells function

mediate immediate responses to stressor

How do chromaffin cells create an immediate response to stressors?

1.) increase HR by force of contraction and dilate bronchioles in lung

2.) increase blood pressure via constriction of blood vessels of skin, digestive, and urinary organs

3.) dilate blood vessels supplying skeletal muscles

4.) dilate pupiles

5.) decrease digestive and urinary function

Pancreatic islets

small rounded islands populated by endocrine cells; secrete hormones into bloodstream

Three main cell types of Pancreatic islets

Alpha cells

Beta cells

Delta cells

Alpha cells secrete...

peptide hormone glucagon

Beta cells secrete...

protein hormone insulin

Delta cells secrete...

peptide hormone somatostatin

Exocrine acinar cells

clustered around small ducts to secrete enzymes and other products; delivered to digestive tract

What regulates concentration of glucose in blood?

insulin and glucagon

Glucagon's major target tissues

cells of liver, muscle tissue, and adipose

Glucagon function

promotes reactions that increase levels of glucose and metabolic fuels in blood

glycogenolysis

Breakdown of glycogen

gluconeogenesis location

Formation of new glucose in liver

How is glucagon secretion inhibited?

by both elevated blood glucose level and somatostatin

What is glucagon secretion triggered by?

- decrease in blood glucose

- sympathetic NS stimulation

- Circulating catecholamines from adrenal medulla

–Ingested protein; hormonal response maintains stable glucose levels during feeding

Hormones of the endocrine pancreas

insulin and glucagon

Insulin

antagonist of glucagon; produced and secreted from beta cells of pancreatic islets

What cells does insulin target?

liver, cardiac muscle, skeletal muscle, and parts of brain

Cell responses to insulin

- uptake and storage of ingested nutrients; lowers blood glucose levels

- synthesis or glycogen in liver

- synthesis of fat from lipids and carbohydrates

- satiety

Satiety

feeling of fullness

Hypoglycemia

low blood glucose

what is hypoglycemia caused by?

elevated insulin levels

Symptoms of hypoglycemia

weakness, dizziness, rapid breathing, nausea, and sweating

Symptoms of severe hypoglycemia

confusion, hallucinations, seizures, coma, and death

When do symptoms of severe hypoglycemia occur?

when the brain is deprived of adequate glucose since glucose is the primary fuel for its metabolic reactions

Hyperglycemia

blood glucose too high

Causes of chronic hyperglycemia

Type I diabetes mellitus, but also often congenital

congenital

often-inherited medical condition that occurs at or before birth

What occurs during congenital hyperglycemia?

- target cells cannot take in circulating glucose

- glucose over produced because of no insulin

- increased level of ketone bodies

What is the result of hyperglycemia?

glucose and ketones in urine; water drawn from ECF by osmosis.

- polyuria and polydipsia from dehydration

polyuria

frequent urination

polydipsia

excessive thirst

Type II diabetes mellitus

non-insulin dependent diabetes millitus

Type I diabetes mellitus

insulin dependent diabetes mellitus

Explain the pathogenesis of type I diabetes mellitus

caused by the destruction or lack of beta islet cells that produce and secrete insulin

Explain the pathogenesis of type II diabetes mellitus

insulin's target tissues are insensitive to insulin; insulin resistance occurs

insulin resistance

so target cells do not initiate proper response to blood glucose concentration

Which diabetes type is usually genetic?

type I diabetes

Which diabetes type is often lifestyle linked?

type II diabetes

What is the result of type II diabetes mellitus?

hyperglycemia, glucosuria, polyuria, poludipsia

glucosuria

excess glucose in urine

Which type of diabetes generally produce enough insulin to prevent ketoacidosis?

type II diabetes mellitus

What are the effects of chronic hyperglycemia?

- damage to blood vessels, decreased circulation in heart and lower limbs

- peripheral nerves, peripheral neuropathy in lower limbs

peripheral neuropathy

numbness, tingling, and burning pain in affected areas

In extreme cases, what are the consequences of hyperglycemia?

blindness and kidney failure

pineal gland

primary endocrine; component of epithalamus

What neurohormone does the pineal gland secrete?

melatonin

When does melatonin secretion occur the most?

secretion increases when dark (night)

Is the pineal gland a primary, secondary, or neuroendocrine organ?

neuroendocrine organ

What is melatonin's main target tissues?

sleep regulation centers in reticular formation of brainstem; adjusts sleep/wake cycle in individuals

Thymus

primary endocrine gland in mediastinum

Where do T lymphocytes mature?

thymus