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Anatomy and Physiology > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

Endocrine System Overview

A
  • Second controlling system of the body
    o Nervous system is the fast-control system
  • Uses chemical messengers (hormones) that are released into the blood
    o Collect information and stimulate effectors to respond
  • Secretes hormones which are slow to react but effect is long-lasting
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2
Q

Endocrine System Overview: Hormones Control Several Major Processes

A 
o	Reproduction
o	Growth and development 
o	Mobilization of body defenses 
o	Maintenance of much of homeostasis
o	Regulation of carbohydrate, protein and fat metabolism
o	Water and electrolyte balance 
o	Energy balance 
o	Aid in the bodies response to stress
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3
Q

The Chemistry of Hormones

A 
Hormones are classified chemically as: 
o	Amino acid–based, which includes: 
	Proteins 
	Peptides
	Amines 
	Excludes those secreted by the adrenal cortex and the reproductive glands

o Steroids (lipid hormones) — made from cholesterol

o Prostaglandins—made from highly active lipids that act as local hormones

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4
Q

Hormone Action

A

Hormones affect only certain tissues or organs (target cells or target organs)
o Target cells must have specific protein receptors

  • Hormone binding alters cellular activity

Typically, one or more of the following occurs:
o Change plasma membrane permeability or membrane potential by opening or closing ion channels
o Activate or inactivate enzymes
o Stimulate or inhibit cell division
o Promote or inhibit secretion of a product
o Turn on or turn off transcription of certain genes

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5
Q

Hormone Action - Two Mechanisms

A

Direct gene activation
o Used by steroid hormones and thyroid hormone

Second-messenger system
o Used by protein and peptide hormones
o Can influence cell activity by binding to hormone receptors on the target cells

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6
Q

Hormone Action: Direct Gene Activation

A
  • Steroid hormones diffuse through the plasma membrane of target cells
  • Once inside the cell, the hormone enters the nucleus
  • Then, the hormone binds to a specific protein within the nucleus
  • Hormone-receptor complex binds to specific sites on the cell’s DNA
  • Certain genes are activated to transcribe messenger RNA
  • mRNA is translated in the cytoplasm
  • New proteins are synthesized
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7
Q

Hormone Action: Second Messenger System

A
  • Hormone (first messenger) binds to a membrane receptor protein
  • Activated receptor sets off a series of reactions that activates an enzyme
  • Enzyme catalyzes a reaction that produces a second-messenger molecule (such as cyclic AMP, known as cAMP)
  • Oversees additional intracellular changes to promote a specific response in the target cell
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8
Q

Hormonal Stimuli

A
  • Most common category of stimulus
  • Endocrine organs are activated by other hormones from other endocrine organs

Example:
o Hormones of the hypothalamus stimulate the anterior pituitary to secrete its hormones to influence the thyroid gland, adrenal cortex, gonads, pancreas and adrenal medulla
o After target tissue is stimulated –> hypothalamus and pituitary receive signals (hormones) that stop the hormones released –> ending chain of hormonal control

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9
Q

Humoral Stimuli

A

Changing blood levels of certain ions and nutrients stimulate hormone release
o Humoral indicates various body fluids, such as blood and bile

Examples:
o Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels
 Blood calcium then rises –> ending release of parathyroid hormone
o Insulin is produced in response to changing levels of blood glucose levels

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10
Q

Neural Stimuli

A
  • Nerve fibers stimulate hormone release
  • Most are under the control of the sympathetic nervous system

Examples:
o Sympathetic stimulation of the adrenal medulla to release epinephrine and norepinephrine during fight or flight response
 Effect
• Increased HR, BP, rate of respiration and blood flow to muscles
• Decreased blood flow to visceral organs and pupils are dilated

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11
Q

Major Endocrine Organs

A
  • Hypothalamus
  • Pituitary gland
  • Pineal gland
  • Thyroid gland
  • Parathyroid glands
  • Thymus
  • Adrenal glands
  • Pancreas
  • Gonads (testes and ovaries)
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12
Q

The Major Endocrine Organs: Exocrine vs Endocrine

A
  • Endocrine Glands –> internal secretion directly into the blood stream
  • Exocrine Glands –> external secretion have ducts to carry secretions to body surface or other organs

Some glands have purely endocrine functions
o Anterior pituitary, thyroid, adrenals, parathyroids, sweat glands, salivary glands, lacrimal glands and pancreas glands

  • Endocrine glands are ductless glands
  • Hormones are released directly into blood or lymph
  • Other glands are mixed glands, with both endocrine and exocrine functions (pancreas, gonads)
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13
Q

Hypothalamus

A

Collects information from body systems and integrate responses in systems to maintain homeostatic balance
o Regulates metabolism, heart rate, energy level, thirst, blood composition and pressure

Hypothalamus produces releasing hormones and inhibiting hormones
o These hormones are released into portal circulation, which connects hypothalamus to anterior pituitary

Hypothalamus also makes two hormones: oxytocin and antidiuretic hormone
o Carried to posterior pituitary via neurosecretory cells for storage

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14
Q

Pituitary Gland

A
  • Pea-sized gland that hangs by a stalk from the hypothalamus in the brain
  • Protected by the sella turcica of the sphenoid bone

Has two functional lobes
o Anterior pituitary—glandular tissue
o Posterior pituitary—nervous tissue

  • Often called the “master endocrine gland”
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15
Q

Posterior Pituitary

A
  • Does not make the hormones it releases –> not a true endocrine gland

Stores hormones made by the hypothalamus
o Two Hormones Released
 Oxytocin
 Antidiuretic hormone (ADH)

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16
Q

Oxytocin

A
  • Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding
  • Causes milk ejection (let-down reflex) in a breastfeeding woman
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17
Q

Antidiuretic Hormone (ADH)

A
  • Inhibits urine production (diuresis) by promoting water reabsorption by the kidneys
  • Urine volume decreases, blood pressure increases
  • In large amounts, causes constriction of arterioles, leading to increased blood pressure (the reason why ADH is known as vasopressin)
  • Increases blood volume –> because of increased reabsorption of fluid and sodium by the kidney –> contributing to higher blood pressure

Alcohol inhibits ADH secretion
o Resulting in increased urination, dehydration and dry mouth the morning after drinking
- Subject to humoral control
- Secreted when plasma levels decreases from hydration, profuse sweating during exercise, secreted when solid particles in the blood become more concentrated

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18
Q

Six Anterior Pituitary Hormones

A

Two hormones affect nonendocrine targets
o Growth hormone
o Prolactin

Four are tropic hormones 
o	Follicle-stimulating hormone 
o	Luteinizing hormone 
o	Thyrotropic hormone 
o	Adrenocorticotropic hormone
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19
Q

Anterior Pituitary Hormones

A
  • Are proteins (or peptides)
  • Act through second-messenger systems
  • Are regulated by hormonal stimuli
  • Are regulated mostly by negative feedback
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20
Q

Growth Hormones

A
  • General metabolic hormone
  • Major effects are directed to growth of skeletal muscles and long bones
  • Plays a role in determining final body size

Causes amino acids to be built into proteins
o GH is an anabolic hormone that induces protein synthesis and stimulates most target cells to grow and divide

  • Causes fats to be broken down for a source of energy and spares glucose
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21
Q

Prolactin

A
  • Stimulates growth of mammary glands and maintains milk production following childbirth
  • Function in males is unknown
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22
Q

Gonadotropic Hormones

A

Regulate hormonal activity of the gonads

Follicle-stimulating hormone (FSH)
 Stimulates estrogen and egg development in ovaries
 Stimulates sperm development in testes

Luteinizing hormone (LH)
 Triggers ovulation of an egg in females
 Produces progesterone and estrogen in women
 Stimulates testosterone production in males
• By stimulating the interstitial cells

23
Q

Thyrotropic Hormone (Thyroid Stimulating Hormone)

A
  • Influences growth and activity of the thyroid gland

- Stimulates the release of thyroxin and triiodothyronine

24
Q

Adrenocorticotropic Hormone (ACTH)

A

Regulates endocrine activity of the adrenal cortex

o Stimulates the release of steroid hormones

25
Q

Pineal Gland

A

Hangs from the roof of the third ventricle of the brain

Secretes melatonin
o Level releases rises and falls through day and night
 Lowest is around noon
o Believed to trigger the body’s sleep/wake cycle
o Believed to coordinate the hormones of fertility in humans and to inhibit the reproductive system until maturity occurs

26
Q

Thyroid Gland

A
  • Found at the base of the throat, inferior to the Adam’s apple
  • Consists of two lobes and a connecting isthmus
  • Follicles are hollow structures that store colloidal material

Produces two hormones
o Thyroid hormone
o Calcitonin

27
Q

Thyroid Hormone

A
  • Major metabolic hormone
  • Controls rate of oxidation of glucose to supply body heat and chemical energy
  • Needed for tissue growth, development and maturation
Composed of two active iodine-containing hormones (iodine is from dietary intake) 
o	Thyroxine (T4 )—secreted by thyroid follicles 
o	Triiodothyronine (T3 )—conversion of T4 at target tissues
28
Q

Calcitonin

A
  • Maintains calcium homeostasis
    o Decreases blood calcium levels by causing calcium deposition on bone
  • Also reduces the absorption of calcium by the intestine and kidney
  • Within adulthood –> very little is released by the thyroid gland
  • Antagonistic to parathyroid hormone
  • Produced by parafollicular cells found between the follicles of the thyroid gland
29
Q

Parathyroid Glands

A

Tiny masses on the posterior of the thyroid

Secrete parathyroid hormone (PTH) in response to low blood calcium levels
o Most important regulator of calcium ion (Ca2+) homeostasis of the blood

o Stimulates osteoclasts to remove calcium from bone
 Moves calcium from bone to blood

o Hypercalcemic hormone (increases blood calcium levels)

o Stimulates the kidneys and intestine to absorb more calcium
 With aid of Vitamin D in digestion
 Stimulating kidney resorption of calcium from urine and excreting phosphorus

30
Q

Thymus

A
  • Located in the upper thorax, posterior to the sternum
  • Largest in infants and children
  • Decreases in size throughout adulthood

Produces a hormone called thymosin
o Matures some types of white blood cells (e.g., T-cells)
o Important in developing the immune system

31
Q

Adrenal Glands

A

Sit on top of the kidneys

Two regions
o Adrenal cortex (functions as a gland)
 Outer glandular region has three layers that produce corticosteroids
 Mineralocorticoids are secreted by outermost layer
 Glucocorticoids are secreted by middle layer
 Sex hormones are secreted by innermost layer

Adrenal medulla
 Inner neural tissue region
 Part of the nervous system
• Stimulated by the sympathetic branch of the ANS

32
Q

Hormones of the Adrenal Cortex: Mineralcorticoids

A

o Produced in outer adrenal cortex
o Regulate mineral (salt) content in blood, particularly sodium and potassium ions
o Regulate water and electrolyte balance
o Regulation to changes in blood pressure and plasma levels
o Target organ is the kidney
o Controlled by the anterior pituitary

33
Q

Hormones of the Adrenal Cortex: Mineralcorticoids (Release of Aldosterone)

A

 Humoral factors (fewer sodium ions or too many potassium ions in the blood)

 Hormonal stimulation (ACTH)

 Renin and angiotensin II in response to a drop in blood pressure
• Renin triggers a series of reactions that trigger the release of angiotensin II
• Angiotensin II is a potent stimulator for aldosterone release

 Aldosterone production is inhibited by atrial natriuretic peptide (ANP), a hormone produced by the heart when blood pressure is too high
• Reduces blood volume and blood pressure

 Under the influence of aldosterone, when sodium and water are reabsorbed by kidneys plasma volume increases –> raising blood pressure

34
Q

Hormones of the Adrenal Cortex: Glucocorticoids (e.g., cortisone and cortisol)

A

o Produced by middle layer of adrenal cortex
o Promote normal cell metabolism
o Help resist long-term stressors by increasing blood glucose levels (hyperglycemic hormone)

Anti-inflammatory properties
 Decreasing edema
 Inhibit pain by inhibiting pain causing prostaglandin

o Released in response to increased blood levels of ACTH

o Maintain blood glucose levels by converting fats and amino acids into glucose –> through process of glucogenesis
 Ensure brain and NS have constant supply of glucose –> only fuel source

35
Q

Hormones of the Adrenal Cortex: Sex Hormones

A

o Produced in the inner layer of the adrenal cortex
o Small amounts are made throughout life
o Most of the hormones produced are androgens (male sex hormones), but some estrogens (female sex hormones) are also formed

36
Q

Adrenal Medulla

A 
Produces two similar hormones (catecholamines) 
o	Epinephrine (adrenaline)
o	Norepinephrine (noradrenaline)

These hormones prepare the body to deal with short term stress (“fight or flight”) by:
o Increasing heart rate, blood pressure, blood glucose levels
o Increases in metabolic rate and glucose production by liver make more energy available for the potential brush with danger
o Dilating small passageways of lungs

37
Q

Catecholamines

A

Hormones released into blood in times of physical or emotional stress
o Bodies response is called an ‘adrenaline rush’

Prepare body for short term stressful situations and cause the so-called alarm stage of stress response

38
Q

Glucocorticoids

A

Produced by cortex and are important when coping with prolonged or continuing stress
 E.g., dealing with death of family member or having major operation

Operate primarily in resistance stage of stress response
 If successful –> problem will be resolved without lasting damage
 If continues –> adrenal cortex may burn out –> potentially fatal

39
Q

Pancreatic Islets

A

Pancreas
o Located in the abdomen, close to stomach
o Mixed gland, with both endocrine and exocrine functions
 Endocrine – secreting hormones controlling blood glucose
 Exocrine – excretes digestive enzymes

The pancreatic islets (islets of Langerhans) produce hormones
o	Insulin—produced by beta cells 
	Decrease blood glucose levels  
o	Glucagon—produced by alpha cells
	Increase blood glucose levels

These hormones are antagonists that maintain blood sugar homeostasis

40
Q

Insulin

A

o Released when blood glucose levels are high
o Increases the rate of glucose uptake and metabolism by body cells
o Stimulates liver to convert glucose into glycogen or fat
o Effects are hypoglycaemic
o Provides life sustaining energy
 Only hormone capable of getting glucose into the body cells

41
Q

Glucagon

A

o Released when blood glucose levels are low
o Stimulates the liver to release glucose to blood, through the breakdown of glycogen
 Thus increasing blood glucose levels

42
Q

Gonads: Ovaries

A

o Female gonads located in the pelvic cavity
o Produce eggs
o Produce two groups of steroid hormones
 Estrogens
 Progesterone

43
Q

Gonads: Testes

A

o Male gonads suspended outside the pelvic cavity
o Produce sperm
o Produce androgens, such as testosterone
o Produce several androgens

Testosterone is the most important androgen
 Responsible for adult male secondary sex characteristics
 Promotes growth and maturation of male reproductive system
 Required for sperm cell production

o Released when stimulated by LH from the anterior pituitary

44
Q

Gonads: Estrogen and Progesterone

A

Oestrogens
o Stimulate the development of secondary female characteristics
o Mature the female reproductive organs
o Regulates menstrual cycle and promotes breast development

Progesterone
o Acts with oestrogen to bring about the menstrual cycle
o Helps in the implantation of an embryo in the uterus
o Helps prepare breasts for lactation

With progesterone, oestrogens also:
o Promote breast development
o Regulate menstrual cycle

45
Q

Other Hormone Producing Tissues and Organs

A 
Other organs that are generally non-endocrine in function also secrete hormones
o	Stomach 
o	Small intestine 
o	Kidneys
o	Heart
46
Q

Placenta

A

o Produces hormones that maintain pregnancy

o Some hormones play a part in the delivery of the baby

o Produces human chorionic gonadotropin (hCG) in addition to estrogen, progesterone, and other hormones
 Initially produced by the developing embryo –> then continued to be produced by fetal part of placenta

 Stimulates ovaries to continue producing oestrogen and progesterone
• Ensures uterine lining is not degraded as menstrual bleeding occurs

 In third month of pregnancy –> produces estrogen and progesterone
• Ovaries become inactive for remainder of pregnancy

o Human placental lactogen (hPL) prepares the breasts for lactation
 Works alongside estrogen and progesterone

o Relaxin relaxes pelvic ligaments and pubic symphysis for childbirth
 Eases birth passage

o Respiratory, excretory and nutrition delivery systems for the fetus

47
Q

Endocrine Disorders and Diseases

A
  • Major disorders of the pituitary gland include acromegaly dwarfism and diabetes insipidus
  • Major disorders of the thyroid gland are hyperthyroidism and hypothyroidism
  • Parathyroid gland disorders affect calcium levels in the blood
48
Q

Diabetes Mellitus

A

Diabetes mellitus results from the inability of the pancreas to produce sufficient amounts of insulin to regulate blood glucose levels

Type I
 Autoimmune disorder
 Immune cells attack insulin secreting beta cells in the pancreas
• Causes insulin production to decrease or stop altogether

Type II
 Pancreas secretes insulin, but bodies receptors are downregulated
• Called insulin resistance
• Insulin resistant receptors wont intake insulin  blood glucose levels increase

49
Q

Overactive and Inactive Pituitary Gland

A

Overactive pituitary gland secretes excessive amounts of a particular hormone
o Most common –> hypersecretion of GH –> results in gigantism
 Can result in diabetes

Inactive pituitary gland secretes inadequate amounts of a particular hormone
o Hypo –> can lead to dwarfism and hypothyroidism
 Dwarfism only affects height and size
• Mental capability is normal

50
Q

Antidiuretic Hormone: Hyposecretion

A

Hyposecretion of an antidiuretic hormone from posterior pituitary gland
o Cause diabetes insipidus
 Excessive thirst

51
Q

Hyperthyroidism: Over-active and Under-active

A

Hyperthyroidism (over-active thyroid)
o Characterised by a visibly enlarged thyroid gland
 Called a goiter
 Caused by insufficient levels of iodine –> necessary for production of TH

o Can lead to increased HR, body temperature, hyperactivity, weight loss, diarrhea and difficulty concentration

Hypothyroidism (under-active thyroid)
o Caused by thyroiditis –> result of inflammation which damages thyroid cells

o Symptoms
 Fatigue, pale, dry skin, thin hair, brittle fingernails, increased sensitivity to cold, constipation and weight gain

52
Q

Hyper and Hyposecretion of the Parathyroid Hormone

A

Hypersecretion of parathyroid hormone
o Causes too much calcium in blood –> hypercalcemia
 Leads to increased calcium absorption by kidneys, brittle bones, decreased HR, fatigue, depression

Hyposecretion of parathyroid hormone
o Leads to low blood calcium levels –> sustained muscle contractions

53
Q

Adrenal Gland: Tumour Glands

A

Can cause an adrenal cortex disorder
 Can also be caused by irregular secretion of hormones from other glands acting on adrenal cortex

 Pushing Syndrome
• Disorder caused by hypersecretion of cortisol
• Associated with symptoms such as a rounded moon shaped face, weight gain, high blood glucose, high BP, osteoporosis, difficulty concentrating, facial hair in women

54
Q

Hyposecretion of Adrenal Cortex Hormones

A

Can cause Adison’s Disease

 Can cause muscle atrophy, a bronze skin tone and kidney damage

Anatomy and Physiology (14 decks)

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