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A & P Unit 4 > Chapter 16 Endocrine System > Flashcards

Chapter 16 Endocrine System Flashcards

1
Q

The body’s second great controlling system which influences metabolic activities of cells by means of hormones is

A

the endocrine system

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2
Q

Endocrine glands are

A

the pituitary, thyroid, parathyroid, adrenal, pineal, and thymus

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3
Q

The pancreas and gonads produce both

A

hormones and exocrine products

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4
Q

What has both neural functions and releases hormones?

A

the hypothalamus

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5
Q

Other tissues and organs that produce hormones are:

A

adipose cells, pockets of cells in the walls of the small intestine, stomach, kidneys, and heart

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6
Q

Major endocrine organs

A
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7
Q

Autocrines

A

chemicals that exert effects on the same cells that secrete them

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8
Q

Paracrines

A

locally acting chemicals that affect cells other than those that secrete them

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9
Q

Autocrines and Paracrines are

A

not considered hormones since hormones are long-distance chemical signals

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10
Q

Hormones

A

chemical substances secreted by cells into the extracellular fluids

  • regulate the metabolic function of other cells
  • have lag times ranging from seconds to hours
  • tend to have prolonged effects
  • are classified as amino acid-based hormones or steroids
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11
Q

Elcosanoids

A

biologically active lipids with local hormone-like activity

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12
Q

Types of hormones

A
  • amino acid-based
    • ​amines, thyroxine, peptide and protein hormones
  • Steroids-gonadal and adrenocortical hormones
  • Elcosanoids-leukotrienes and prostaglandins
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13
Q

Hormones alter target cell activity by one of two mechanisms

A
  • second messengers:
    • regulatory G proteins
    • amino acid-based hormones
  • direct gene activation
    • steroid hormones

The precise response depends on the type of target cell

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14
Q

Hormones produce one or more of the following cellular changes in target cells:

A
  • alter plasma membrane permeability
  • stimulate protein synthesis
  • activate or deactivate enzyme systems
  • induce secretory activity
  • stimulate mitosis
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15
Q

Amino Acid-Based hormone action:

cAMP Second Messenger*

A
  • hormone (first messenger) binds to its receptor, which then binds to a G protein
  • the G protein is then activated as it binds GTP, displacing GDP
  • activated G protein activated the effector enzyme adenylate cyclase
  • adenylate cyclase generates cAMP (second messenger) from ATP
  • cAMP activates protein kinases, which then cause cellular effects
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16
Q

Amino Acid-Based Hormone Action:

PIP-Calcium*

A
  • hormone binds to the receptor and activates the G protein
  • G protein binds and activates phospholipase
  • phospholipase splits and phospholipids PIP2 into diacylglycerol (DAG) and IP3 (both act as second messengers
  • DAG activates protein kinases; IP3 triggers the release of Ca2+ stores
  • Ca2+ (third messenger) alters cellular responses
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17
Q

Steroid hormones

A
  • this interaction prompts DNA transcription to produce mRNA
  • the mRNA is translated into proteins, which bring about a cellular effect
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18
Q

Target Cell Specificity

A
  • hormones circulate to all tissues but only activate cells referred to as target cells
  • target cells must have specific receptors to which the hormone binds
  • these receptors may be intracellular or located on the plasma membrane
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19
Q

Target cell Activation depends on three factors:

A
  • Blood Levels of the hormone
  • Relative number of receptors on the target cell
  • the affinity of those receptors for the hormone-(means how likely they will bind)
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20
Q

Up-regulation is when

A

target cells form more receptors in response to the hormone

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21
Q

Down-regulation is when

A

target cells lose receptors in response to the hormone

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22
Q

Hormones circulate in the blood in what two forms:

A

free or bound

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23
Q

Hormones are removed from the blood by:

A
  • degrading enzymes
  • the kidneys
  • liver enzyme systems
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24
Q

Interaction of Hormones at Target Cells

The three types of hormone interaction:

A
  • permissiveness
  • synergism
  • antagonism
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25
**permissiveness** is when
one hormone cannot exert its effects without another hormone being present
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**synergism is when**
more than one hormone produces the same effects on a target cell
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**antagonism** is when
one or more hormones opposes the action of another hormone
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Blood levels of hormones are
**controlled by negative feedback systems**
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**Hormones are synthesized and released in response to:**
* **Humoral stimuli** * **Neural stimuli** * **Hormonal stimuli**
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**Humoral stimuli:**
secretion of **hormones in direct response to changing blood levels of ions and nutrients** **Example: concentration of calcium ions in the blood** * declining blood Ca2+ concentration stimulates the parathyroid gland to secrete PTH (parathyroid hormone) * PTH causes Ca2+ concentrations to rise and the stimulus is removed
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**Neural stimuli:**
nerve fibers stimulate hormone release
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**Hormonal stimuli:**
release of hormones in response to hormones produced by other endocrine organs
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**Major endocrine organs: Pituitary (Hyopohysis)** **What are the 3**
1. **pituitary gland** 2. **neurohypophysis (posterior lobe)** 3. **adenohypophysis (anterior lobe)**
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**Pituitary gland:**
a two-lobed organ that secrets **nine major hormones**
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**Neurohypophysis:**
**posterior lobe** (neural tissue) and the infundibulum * **receives, stores and releases hormones from the hypothalamus**
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**Adenohypophysis:**
**anterior lobe** made up of glandular tissue * **synthesizes and secretes a number of hormones**
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**Major Endocrine Organs: Pituitary (Hypophysis)**
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The **six** hormones of the adenohypophysis:
* **abbreviated as GH, TSH, ACTH, FSH, LH, and PRL** * **regulate the activity of other endocrine glands** In addition, pro-opiomelanocortin (POMC): * has been isolated from the pituitary * is split into ACTH, opiates, and MSH
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Activity of the Adenophypophysis The hypothalamus sends a chemical stimulus to the anterior pituitary
* **Releasing hormones to stimulate the synthesis and release of hormones** * inhibiting hormones shut off the synthesis and release of hormones
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**The tropic hormones that are release are:**
* **Thyroid-stimulating hormone (TSH)** * **Adrenocorticotropic hormone (ACTH)** * **Follicle-stimulating hormone (FSH)** * **Luteinizing hormone (LH)**
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Growth Hormone (GH) * produced by **somatotropic cells** of the **anterior lobe** that:
* stimulate most cells, but target bone and skeletal muscle * promote protein synthesis and encourage the use of fats for fuel
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Metabolic action of growth hormone:
* **GH stimulates the liver, skeletal muscle, bone, and cartilage to produce insulin-like growth factors**
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Metabolic Action of Growth Hormone (GH)
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Thyroid-stimulating hormone (Thyrotropin)
* **stimulates the normal development and secretory activity of the thyroid**
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Adrenocorticotropic Hormone (Corticotropin)
* **stimulates the adrenal cortex to release corticosteroids** * **internal and external factors such as fever, hypoglycemia, and stressors can trigger the release of CRH**
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**Gonadotropins**-follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
* **regulate the function of the ovaries and testes** * **FSH stimulates gamete (egg or sperm) production**
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Prolactin (PRL)
* **in females, stimulates milk production by the breasts**
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The posterior pituitary and hypothalamic hormones ## Footnote **posterior pituitary made of:**
axons of hypothalamic neurons, **stores antidiuretic hormone (ADH0 and oxygen** * **ADH and oxytocin are synthesized in the hypothalamus** * **ADH influences water balance** * **Oxytocin stimulates smooth muscle contraction in breasts and uterus** * **both use PIP-calcium second-messenger mechanism**
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**Oxytocin:**
* Oxytocin is a strong stimulant of uterine contraction * regulated by a **positive feedback mechanism** to oxytocin in the blood * this **leads to an increase in the intensity of uterine contractions**, ending in birth * **oxytocin triggers milk ejection** ("letdown" reflex) in women producing milk
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Antidiuretic Hormone (ADH) ## Footnote **ADH helps to:**
* **avoid dehydration or water overload** * **prevents urine formation** * **alcohol inhibits ADH release and causes copious urine output**
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Thyroid Gland is the
**largest gland, located in the anterior of the neck**, consists of two lateral lobes connected by a median tissue mass called the isthmus
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Thyroid Gland
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**Thyroid hormone is a:**
**major metabolic hormone** * **consists of two related iodine-containing compounds** * **​T4-thyroxine:** has two tyrosine molecules plus four bound iodine atoms * **T3-triiodothyronine:** has two tyrosines with three bound iodine atoms
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Effects of Thyroid Hormone TH is concerned with:
* glucose oxidation * increasing metabolic rate * heat production
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Effects of Thyroid Hormone ## Footnote **TH plays a role in:**
* maintaining blood pressure * regulating tissue growth * developing skeletal and nervous systems * maturation and reproductive capabilities
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Calcitonin
* a peptide hormone produced by the parafollicular, or C, cells * **lowers blood calcium levels in children** * antagonist to parathyroid hormone (PTH) * calcitonin targets the skeleton * **regulated by a humoral (calcium ion concentration in the blood) negative feedback mechanism**
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Parathyroid glands are
* **tiny glands embedded in the posterior aspect of the thyroid** * cells are arranged in cords **containing** oxyphil and **chief cells** * **chief (principal) cells secrete PTH** * **PTH (parathormone) regulates calcium balance in the blood**
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Parathyroid Glands
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Effects of Parathyroid Hormone ## Footnote **PTH release increases Ca2+ in blood as it:**
* stimulates osteoclasts to digest bone matrix * enhances the reabsorption of Ca2+ and the secretion of phosphate by the kidneys * increases absorption of Ca2+ by intestinal mucosal ## Footnote **Rising Ca2+ in the blood inhibits PTH release**
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Effects of Parathyroid Hormone
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Adrenal (Suprarenal) Glands ## Footnote **Adrenal glands:**
* are paired, pyramid-shaped organs atop the kidneys Structurally and functionally, **they are two glands in one** * **Adrenal medulla**-neural tissue that acts as part of the SNS * **Adrenal cortex**-glandular tissue derived from embryonic mesoderm
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Adrenal Cortex
* **synthesizes and releases steroid hormones called corticosteroids** * different corticosteroids are produced in each of the three layers * **Zona glomerulosa-mineralocorticoids: regulate electrolytes in extracellular fluids. (most important to aldosterone)** * **Zona fasciculata-glucocorticoids: help the body resist stress. (Chiefly cortisol)** * **Zona reticularis-gonadocorticoids: most are androgens (male sex hormones), and the most important one is testosterone. (androgens contribute to the onset of puberty)**
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Adrenal Cortex
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Adrenal Medulla
made up of chromaffin cells that **secrete epinephrine and norepinephrine**
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Pancreas
* a **triangular gland**, which has both **exocrine and endocrine cells**, located **behind the stomach**
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**Pancreatic islets** (islets of Langerhans)
produce hormones (endocrine products) **The islets contain two major cell types:** * **Alpha (a) cells** that produce **glucagon** * **Beta (B) cells** that produce **insulin**
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Glucagon **Its major target is the liver**, where it promotes:
* **Glycogenolysis**-the **breakdown** of glycogen to glucose * **Gluconeogenesis**-**synthesis** of glucose from the lactic acid and noncarbohydrates * **release of glucose to the blood from liver cells**
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**Insulin**
* **lowers blood glucose levels**
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Diabetes Mellitus (DM) * **Results from hyposecretion or hypoactivity of insulin** * The **three** cardinal signs of DM are:
* Polyuria-**huge urine output** * Polydipsia-**excessive thirst** * Polyphagia-**excessive hunger and food consumption**
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Gonads: Female * Paired ovaries in the abdominopelvic cavity **produce estrogens and progesterone** * They are responsible for:
* maturation of the reproductive organs * the appearance of secondary sexual characteristics * breast development and cyclic changes in the uterine mucosa
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Gonads: Male * Testes located in an extra-abdominal sac (scrotum) **produce testosterone** * Testosterone:
* initiates maturation of male reproductive organs * causes the appearance of secondary sexual characteristics and sex drive * is necessary for sperm production * maintains sex organs in their functional state
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Pineal Gland is the:
* **small gland hanging from the roof of the third ventricle of the brain** * **secretory product us melatonin** * **melatonin is involved with:** * **day/night cycles**
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Thymus
* lobulated gland located **deep to the sternum** * these hormones are essential for the development of the T lymphocytes (T cells) of the **immune system** * the **thymus gland**, located behind your sternum and between your lungs, is **only active until puberty. After puberty, the thymus starts to slowly shrink and become replaced by fat.**
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A & P Unit 4 (6 decks)

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