Lecture 19: Endocrine Flashcards
What is the endocrine system a series of?
Discrete glands, that you can see
What makes endocrine tissues different from glands?
They are just tissues, not discrete glands and are integrated into other tissue and they have endocrine properties
Where are Endocrine Tissues found?
- Digestive tract
- Kidneys
- Heart
- Adipose tissue
What is the Endocrine system?
A collection of glands and tissues of the body that secrete chemical messengers (hormones) into blood directly or via interstitial fluid or lymph
How do the endocrine system and the nervous system work together?
They both regulate processes in the body
What are the two types of Glands?
Exocrine and Endocrine
What do Exocrine glands do?
Release their secretions into ducts that carry the secretions to an epithelial surface
What do Endocrine glands do?
Release their secretions into blood (directly or via interstitial fluid)
What are examples of Exocrine glands?
Sweat, Mammary, Salivary
What are examples of Endocrine glands?
Thyroid, Pituitary, Adrenal
What does Glandular Epithelium consist of?
Specialized cells that synthesize, store, and secrete chemical substances
What is a Hormone?
A chemical messenger
What are hormones produced and secreted by?
Endocrine cells
How does a Hormone facilitate acting on specific target cells?
They can only bind to cells with certain receptors
What do Hormones travel through?
The blood
What are signals sent by in the Nervous system?
Neurons
What are signals sent by in the Endocrine system?
Endocrine glandular cells
How are signals conducted in the nervous system?
Electrical impulses are conducted along axons + neurotransmitters
How are signals conducted in the Endocrine system?
They are circulated in the bloodstream
What is the difference in specificity in the Nervous and Endocrine system?
The nervous system is highly specific and the endocrine system has widespread activity
What is the difference in duration between the Nervous and Endocrine system?
The nervous system has short term activity and the endocrine system has a long duration
How is there interaction between the nervous and endocrine system?
- The nervous system can control the endocrine system, especially though the pituitary glands
- Hormones can also feedback and affect neural function
Which chemical messengers do both neurons and gland cells secrete?
Adrenaline and Vasopressin (ADH)
What do hybrids between and endocrine cell and a neuron do?
They conduct electrical signals but release a hormone at the end
What are the four classes of hormones?
- Amino acid derivatives
- Peptide hormones
- Steroid hormones
- Eicosanoid hormones
What is an example of an amino acid derivative hormone?
Adrenaline
What is an example of a peptide hormone?
Oxytocin
What is an example of a steroid hormone?
Estrogen
What is an example of an Eicosanoid hormone?
Prostaglandins
What are Steroid Hormones mainly built from?
Cholesterol
What are Eicosanoid hormones derived from?
Fatty acids
What is unique about Eicosanoid hormones?
They really only work at short distances in paracrine and autocrine functions
What is blocked when taking aspirin or advil?
Prostaglandins
What do Thyroid Hormones do?
Elevate cellular oxygen use and metabolic rate
What are Thyroid hormones important for?
Growth and development
Where does the Thyroid gland sit?
Anterior to the trachea, inferior to the larynx
What is the Thyroid gland anchored to?
The first 2-3 tracheal rings
Why does the Thyroid Gland have a large blood supply?
Because its purpose is to secrete things into the blood
What does a Thyroid follicle consist of?
An outer capsule of follicular cells (T thyrocytes) and an inner cavity filled with colloid
What is Colloid?
A viscous protein rich fluid found inside follicles
What does Colloid contain?
The precursor of Thyroid hormones
What is the Precursor of Thyroid hormones found in the colloid called?
Thyroglobulin
What do T Thyrocyte (follicular) cells do?
Synthesize T thyrocytes into the lumen of the follicle
What is the relationship between Iodine and the Thyroid?
Iodine is actively transported into the Thyroid follicle and enzymes attach the Iodine molecules onto the Thyroglobulin protein
How does Thyroglobulin become activated?
Thyrocytes bring the thyroglobulin back into the cell from the lumen and combine it with enzymes that break apart the thyroglobulin and some of those parts that are produced are T3 and T4 which go into the blood
What are the hormones released by the thyroid?
T3 and T4
What are T3 and T4 derivatives of?
The amino acid tyrosine
What is the main hormone released by the thyroid?
Thyroxine (T4)
What is the more active hormone released from the Thyroid?
Triiodothyronine (T3)
What do both T4 and T3 do?
Regulate metabolism
Where does Thyroid Stimulating Hormone (TSH) come from?
The pituitary
What causes the Pituitary to release TSH?
Thyrotropin releasing hormone from the hypothalamus
What inhibits the thyroid from releasing T4 and T3?
Increased levels of T4 and T3 in the blood that tell the pituitary and the thyroid to stop releasing TSH and TRH
Where does the Pituitary sit?
In the bony sella turcica
What is the other name for the Pituitary Gland?
Hypophysis
What is the Pituitary connected to the brain by?
The infundibulum
What are the two parts of the Pituitary?
The Adenohypophysis (anterior lobe) and the Neurohypophysis (Posterior lobe)
What does the adenohypophysis look like?
Glandular tissue anywhere else
What does the Neurohypophysis contain?
Nerve terminals
What is a Portal System?
When there is a vein connecting to a capillary bed
What is the Primary Capillary Plexus?
The portion of the anterior pituitary that the nerve fibers terminate on
What is the Primary Capillary Plexus supplied by?
The Superior Hypophyseal artery
How does the Hypothalamic-Hypophyseal Portal System work?
The neurosecretory cells in the hypothalamus release neurotransmitters into, the primary capillary plexus which then goes to the secondary capillary plexus which secretes hormones through the efferent veins
What are the Anterior Pituitary hormones?
- Human Growth Hormone (hGH)
- Thyroid Stimulating Hormone (TSH)
- Follicle Stimulating Hormone (FSH)/Luteinizing Hormone (LH)
- Prolactin
- Adrenocorticotropic Hormone (ACTH)
- Melanocyte Stimulating Hormone (MSH)
What does Human Growth Hormone do?
Stimulates body growth and metabolism
What does Thyroid Stimulating Hormone do?
Controls Thyroid gland function
What does Follicle Stimulating Hormone/ Luteinizing Hormone do?
Control secretion of sex hormones and production of gametes
What does Prolactin do?
Stimulates milk production
What does Adrenocorticotropic Hormone do?
Controls hormone secretion by the adrenal cortex
What does Melanocyte Stimulating Hormone do?
Stimulates melanin secretion
How does the Neurohypophysis work?
Neurosecretory cells travel all the way to the capillary plexus of the neurohypophysis and secrete their neurotransmitters into the blood which then cause hormones to go into circulation
What are the Posterior Pituitary Hormones?
Vasopressin (ADH) and Oxytocin
What does Vasopressin (ADH) do?
Regulates the concentration of urine, regulate blood pressure
What is Vasopressin (ADH) made by?
Neurons of the supraoptic nucleus
What does oxytocin do?
- Stimulate uterine contraction during childbirth
* Stimulates release of milk from mammary glands
What is Oxytocin made by?
Neurons of the Paraventricular nucleus
What does the Adrenocorticotropic hormone act on?
The adrenal glands
What are the outer and inner part of the adrenal glands known as?
The Cortex and the Medulla
Where do a lot of the Steroid Hormones come from?
The Cortex of the adrenal gland
What are the three different zones of the Cortex from outside to inside?
- Zona Glomerulosa
- Zona Fasciculata
- Zona Reticularis
Which part of the cortex of the adrenal glands respond to ACTH?
The zona Fasciculata
What does the Zona Fasciculata secrete?
Glucocorticoids
What type of Hormones are secreted by the adrenal glands?
Steroid hormones derived from Cholesterol
What is an example of a Glucocorticoid?
Cortisol
What are Glucocorticoids used for?
Immunosuppressive and anti-inflammatory properties
What does the Zona glomerulosa produce?
Mineralcorticorticoids
What do Mineralocorticoids do?
- Controls electrolyte balance
- Increases renal absorption of Na and H2O
- Decreases renal absorption of K+
What is an example of a Mineralocorticoid?
Aldosterone
What does the Zona Reticularis secrete?
Androgens
What do Androgens (sex hormones) do?
- Stimulate growth of pubic hair
* Important source of testosterone in adult females
What hormones does the Zona Reticularis produce?
Androgens
Where do the preganglionic neurons on the sympathetic nervous system sit?
In the spinal cord
What stimulates the adrenal glands?
Preganglionic sympathetic fibers from the medulla
What is another name for Neuroendocrine cells
Chromaffin cells
What do the Chromaffin cells of the Adrenal Medulla release?
Adrenaline/noradrenaline into the blood
What are the Hormones of the Adrenal Medulla?
Epinephrine and Norepinephrine
What do Epinephrine and Norepinephrine do?
- Increase cardiac output
- Increase blood pressure
- Increase blood glucose
- Effect release of lipids from adipose tissue
What are the preganglionic neurons that stimulate the adrenal medulla activated by?
The Hypothalamus
What is the fast way to respond to a stressful situation?
Through the sympathetic neurons to the adrenal medulla causing release of epinephrine or adrenaline
What is the slow way to respond to a stressful situation?
From the hypothalamus to the anterior pituitary release ACTH which goes to the adrenal cortex and lead to the release of glucocorticoids
What type of Gland is the pancreas?
Both an endocrine and an exocrine gland
What do the Exocrine Glandular cells of the pancreas produce?
Pancreatic enzymes
What are the pancreatic enzymes secreted into?
The small intestine
What are Islet cells?
Islands of endocrine cells in the pancreas surrounded by exocrine cells
Why do Islet cells have substantial blood flow around them?
To collect the hormones produced by the cells
What are the three different types of cells found in the islet of the pancreas?
- Alpha
- Beta
- Delta
What do the beta cells of the pancreas produce?
Insulin
What do Alpha cells of the pancreas secrete?
Glucagon
What do Delta cells of the pancreas secrete?
Somatostatin
What does Glucagon do?
- Stimulates glucose synthesis
- Elevates blood glucose
- Mobilizes lipid reserves
What does Insulin do?
- Stimulates lipid and glycogen synthesis and storage
- Stimulates glucose uptake by cells
- Decreases blood glucose
What does Somatostatin do?
Inhibits the secretion of glucagon and insulin
What happens with insulin in diabetes mellitus?
There is an inability to produce or use insulin
What are the symptoms of Diabetes mellitus?
- Elevation of blood glucose levels (hyperglycemia)
* Excretion of glucose in urine
What occurs in type I diabetes?
An autoimmune disease destroys insulin secreting cells of islets
What occurs in Type II diabetes?
- There is a combination of insulin-resistance and insulin secretory defects
- Target cells become less sensitive to diabetes
How can Type II diabetes be treated?
Diet, exercise and weight loss
Where are the Parathyroid glands found?
Right behind the thyroid
What is the purpose of the Parathyroid gland?
Secrete parathyroid hormone which elevates calcium levels in the blood
How does Parathyroid hormone secreted by the parathyroid gland work?
It removes calcium deposition in bone so that it can go into the blood
Which less essential hormone counteracts PTH?
Calcitonin
What does the pineal gland secrete?
Melatonin
What does Melatonin do?
Regulates the biological clock
What do the hormones secreted by the Thymus gland do?
Promote the proliferation and maturation of T-lymphocytes
What do the hormones secreted by the GI tract do?
Regulate the activity of the GI tract and digestive glands
Which hormones are secreted by the kidneys?
- Erythropoietin
* Renin
What does Erythropoietin do?
Increases RBC production
What does Renin do?
Increases blood pressure
Which hormone is secreted by the heart?
Atrial Natriuretic peptide
What does Atrial Natriuretic Peptide do?
Decreases blood pressue
What hormone is secreted by the Adipose tissue?
Leptins
What are Leptins?
A hormone appetite suppressant
