Test 1 Flashcards
The Endocrine System
The second communication system of the body (after nervous system)
Hormones
Chemical messengers
Endocrine glands
“Ductless” glands
Primary glands
are hypothalamus, pituitary, thyroid, parathyroid, adrenal, pineal, thymus
Types of Hormones
Amino Acid Based Hormones
Steroid Hormones
Amino Acid Based Hormones
Water soluble and include peptides & proteins. React with their target cells by activating membrane bound receptors and setting off 2nd messenger systems. Because they are water soluble they don’t easily cross the lipid bilayer (hydrophobic region) of cell membrane. These types of hormones move “unbound” within the water based plasma of the vascular system.
Steroid Hormones
Lipid soluble therefore easily cross lipid bilayer and bind to intracellular receptors to alter gene activation in the cell nucleus. Lipid soluble hormones circulate “bound to proteins” through the vascular system. Any protein bound hormone (or any drug or compound) are non-functional until they are dissociated or unbound from their protein carriers.
Hormone characteristics
1) Regulate metabolic function of other cells
2) Have significant lag times
3) Have prolonged effects
4) Alter plasma membrane permeability
5) Stimulate protein synthesis
6) Activate or deactivate enzyme systems
7) Stimulate mitosis
Target Cells
Specify the action of a specific hormone. Must have receptors either on the cell surface (amino acid based hormones) or intracellular receptors (steroid hormones) for hormones to attach to.
Target Cell Activation Depends On
1) Blood levels (quantity) of hormones, 2) Number of receptors (quantity) on the target cell
3) Binding affinity of hormone to receptor.
Up-regulations
More receptors are formed on, or within the target cell.
Down-regulation
Loss or decrease of receptors associated with the target cell.
Most cases of change in receptors numbers in through
down regulation
Stimuli for Hormone Release
1) Humoral – response to changing blood levels of ions and nutrients
2) Neural – ex. Sympathetic nervous system in the adrenal medulla
3) Hormonal – release of hormones in response to other hormones.
Most stimuli for hormone release in the body follow the
“Negative Feedback Pathway”
Major Glands
1) Hypothalamus
2) Pituitary
Hypothalamus
Superior to the pituitary gland and physically connected to the pituitary by the
infundibulum.
Pituitary
Called the “Master Gland” of the body by the majority of literature and endocrinologist.
Anterior Pituitary
“Adenohypophysis”
Posterior Pituitary
“Neurohypophysis”
Adenohypophysis
Glandular tissue
The hypothalamus sends a chemical signal to the anterior pituitary, either through “releasing” hormones for the synthesis and release of a tropic hormone
TRH
an “inhibitory” hormone to shut off the synthesis and release of hormones
TIH
Tropic Hormones
Hormones which stimulate the release of other hormones from specific target endocrine glands.
Tropic Hormones from the Anterior Pituitary
Thyroid Stimulating Hormone (TSH) Adrenal Corticotrophic Hormone (ACTH) Follicle Stimulating Hormone (FSH) Luteinizing Hormone (LH) Prolactin (PRL)
Thyroid Stimulating Hormone (TSH)
Release is triggered by TRH (TIH) from the hypothalamus. Targets Thyroid Gland
Adrenal Corticotrophic Hormone (ACTH)
Triggered by ACTRH (ACTIH) from hypothalamus. Targets the Adrenal Cortex.
Follicle Stimulating Hormone (FSH)
GnRH (GnIH) from hypothalamus. Targets the Ovaries & Testes.
Luteinizing Hormone (LH)
GnRH (GnIH) from hypothalamus. Targets the Ovaries & Testes.
Prolactin (PRL)
PRH (PIH) from the hypothalamus. Targets the Mammary Glands.
Growth Hormone (GH)
GHRH (GHIH) from hypothalamus. Released from the anterior pituitary however is not a “tropic hormone” by definition but rather is a direct acting hormone primarily on skeletal muscle and the skeletal system.
Non-Homeostatic Conditions Related To Growth Hormone
Hypersecretion and Hyposecretion
Hypersecretion
of GH results in gigantism in children and acromegaly in adults
Hyposecretion
of GH causes dwarfism in children but generally no problems in adults
Neurohypophysis
Neural Tissue
Oxytocin
Stimulant of uterine contractions during child birth and mammary gland contraction for the nursing infant. Follows a “Positive Feedback Pathway”.
ADH
Controlled through osmoreceptors that monitor solute concentrations.
Abnormally high concentrations of solutes
increase (↑) of ADH release to preserve water in the body.
Abnormally low concentrations of solutes
decrease (↓) ADH release to promote diuresis or more urine output.
Thyroid Gland
The largest “pure” endocrine gland
Where is the Thyroid gland located?
Base of the neck behind adam’s apple
“pure” means
releases only hormones from “ductless” endocrine glands and does not have an “exocrine” function such as in the Pancreas.
Three (3) Thyroid hormones (TH) are
T4 – Thyroxine
T3 – Triiodothyronine
Calcitonin
T4 – Thyroxine
Tyrosine plus four bound Iodine atoms
T3 – Triiodothyronine
Tyrosine plus 3 bound Iodine atoms
Thyroid Hormones, T4 & T3, function in some degree in regulating
Blood pressure, Tissue growth, developing Nervous and Skeletal system, Reproductive system and Basal Metabolic Rate.
Calcitonin
Lowers blood calcium levels by inhibiting osteoclasts and stimulates uptake of calcium into the bone
Non-Homeostatic Conditions Related To The Thyroid Gland
Hypothyroid and Hyperthyroid
Hypothyroid
Generally occurs due to a deficiency in iodine therefore decreased TH. “Goiter” is an enlargement of the thyroid gland as more & more TSH is released from the anterior pituitary.
Hyperthyroid
Autoimmune disease results in antibodies similar in shape to TSH therefore stimulates excess TH release. These individuals may show signs of elevated BMR, elevated heart rate, tremors, excessive diaphoresis (sweating). “Exophthalmos” results from edema (fluid) accumulating posterior to the eyeballs. (Graves Disease)
Myxedema
is the adult form while Cretinism is the similar condition in infants
Parathyroid Glands
Parathyroid hormone (PTH) increases blood concentrations of calcium by stimulating osteoclasts
Where is the parathyroid gland located?
next to the two thyroid gland lobes in the neck
Adrenal Glands
Two tissue segments or regions, glandular and nervous tissue which make up this endocrine gland are analogous or similar to the pituitary gland from a histology viewpoint.
Where are the adrenal glands located?
on top of the kidneys
Adrenal cortex
Outer most layer of glandular or secretory cells which are similar to the anterior pituitary gland. The adrenal cortex secretes the “Corticosteroids”. Release of these are stimulated by ACTH from the anterior pituitary to regulate electrolytes in extracellular fluid.
Adrenal medulla
Innermost region of the adrenal gland are nerve fibers from the Sympathetic Nervous System, or in laymen’s terms, the “Fight or Flight System.” This makes the medulla area similar to the posterior pituitary gland.
The adrenal medulla secretes
the adrenalins, Epinephrine and Norepinephrine.
These elevate blood glucose, constrict blood vessels
makes the heart beat faster and stronger, increase respiratory rate and dilate the respiratory passage ways.
Epinephrine primarily targets the heart
leading to its stimulation while Norepinephrine is basically active in the walls of blood vessels and walls of the trachea and bronchioles of the respiratory system
Non-Homeostatic Conditions Related To The Adrenal Glands
Hypersecretion and Hyposecretion
Hypersecretion
from the adrenal medulla
Hyposecretion
from the adrenal medulla, no significant adverse effects in the body, however this is a controversial theory.
Pheochromocytoma
generally from a tumor of the medulla. Causes increased release of the catecholamines, Epinephrine & Norepinephrine and the symptoms of increased sympathetic nervous system activity in the body.
Pancreas
An exocrine and endocrine gland
Pancreatic cells called
“islets of Langerhans”
Pancreatic cells
where are found the Alpha cells that produce the hormone “Glucagon”
Glucagon
increases blood glucose
concentration through the processes of glycolysis and gluconeogenesis in the liver
The pancreatic Beta cells produce
the hormone “Insulin”
Insulin
lowers blood glucose concentration
Insulin is initially synthesized as
“Proinsulin”
Proinsulin, or any “pro-drug” implies
that in this form it is inactive or in the case of (pro)insulin cannot mobilize glucose from blood in to cells. Further metabolism of proinsulin must occur before it is in the active form of Insulin.
Non- Homeostatic Conditions Related to The Pancreas
Diabetes Mellitus (DM), Hyposecretion, Hypoactivity
Diabetes Mellitus (DM)
Results from hyposecretion or hypoactivity of insulin
Hyposecretion
is an inability to produce enough insulin to drive the glucose from the blood into the cells. This is “Type I Diabetes”
Hypoactivity
is a case where there is a high enough concentration of insulin
being produced but generally a decrease in quantity of receptors for the insulin to bind to. This is “Type II Diabetes”
Prolonged, uncontrolled elevated blood glucose levels may result in a
“Diabetic Coma”
Hyperinsulinism, or excess insulin within the blood relative to the blood glucose may result
“Insulin Shock”
Both of these conditions can lead to confusion, loss of consciousness and death
Diabetic Coma & Insulin Shock
The Cardinal Signs & Symptoms in Any Type of Uncontrolled Diabetes Are
Polyuria, Polydipsia, Polyphagia
Polyuria
Excess urine output
Polydipsia
Excessive thirst
Polyphagia
Excessive hunger and food consumption
Pineal Gland
Hormone is melatonin which is involved with day/night cycles
Where is the pineal gland located?
deep in the brain in an area called the epithalamus
Thymus
Essential for the initial development of the immune system in the very young. Hormone prepares the T-lymphocytes of the immune system to combat intracellular pathogens. Gland begins to atrophy with age and becomes non-functional.
Where is the thymus gland located?
located behind the sternum (breastbone) but in front of the heart
Other Hormone Producing Atypical Endocrine Structures
Heart, Gastrointestinal tract, Placenta, Kidneys, Skin, Adipose
Heart
Hormone is Atrial Natriuretic Peptide (ANP) which helps to regulate blood pressure
Gastrointestinal tract
Releases digestive hormones
Placenta
Hormones to help regulate the course of pregnancy
Kidneys
Hormone, Erythropoietin which signals production of red blood cells in the bone marrow
Skin
Cholecalciferol hormone precursor to Vitamin D
Adipose
Hormone Leptin involved in the feeling of being satiated or full and increases cellular energy.
Blood
Composition; pH 7.35-7.45, Temperature 380C, Liquid plasma, & Formed elements
Erythrocytes
Red Blood Cells (RBC’s) – Bi-concave, anucleated cells. Approximately 97% of
content is comprised of Hemoglobin (Hb). Classic example of “complementarity of structure
and function” which means that the anatomy of the RBC is critical to its normal function. RBC’s have an approximate life span of 100-120 days.
Hemoglobin
Protein consisting of 2 alpha and 2 beta chains. Each chain contains 1 heme molecule bound to 1 iron atom (Fe). Oxygen specifically binds to the iron. Therefore 4 molecules of oxygen can be carried by 1 Hb molecule per RBC. Carbon dioxide binds to the globin chains of Hb.
Hematopoiesis
refers to the synthesis of all formed elements of blood within the bone marrow, red blood cells, white blood cells and platelets
The three formed elements of blood all originate from
the “hemocytoblasts” stem cell.
Erythropoiesis
Synthesis of Red Blood Cells
To few RBC’s leads to
to tissue hypoxia, (decreased) oxygen concentration delivered to the cells.
In this case the “kidneys” release
the hormone erythropoietin which stimulates erythropoiesis within the bone marrow.
Hematocrit
The percentage (%) of RBC’s in the total blood volume
Generally 45% is considered
a normal hematocrit
Erythrocyte Disorders
Anemia, Polycythemia, Thalassemias
Anemia
A symptom rather that a disease. Decreased blood oxygen levels to support tissue metabolism. Signs & Symptoms include; Fatigue, paleness, shortness of breath, chills
Hemorrhagic anemia
result of blood loss
Hemolytic anemia
prematurely ruptured RBC’s
Aplastic anemia
Destruction or inhibition of red bone marrow
Iron-deficiency anemia
Insufficient iron intake or absorption. Microcytic anemia
Pernicious anemia
deficiency of Vitamin B12 due to lack of “intrinsic factor” from the stomach. Also known as Macrocytic anemia.
Polycythemia
Excess RBC’s that increase blood viscosity
Polycythemia vera
Bone cancer leading to excess RBC’s
Blood doping
A self-induced polycythemia used to increase the quantity of RBC’s therefore the amount of oxygen supplied to the cells. This practice also results in thick blood in these individuals and often leads to a lethal outcome.
Thalassemias
Faulty globin chain in Hb
Sickle cell anemia
One amino acid out of 146 in a “beta chain” of hemoglobin is wrong leading to sickle-shaped cells and abnormal clotting
Leukocytes
White Blood Cells (WBC’s) – Of all the formed elements of blood, the WBC is the only “complete cell” consisting of a nucleus and various organelles.
WBC’s make up
approximately 1% of the total blood volume (along with the platelets)
Leukopoiesis
Synthesis of white blood cells and originate from hemocytoblasts in the bone marrow as do all of the formed elements
Leukemias
Uncontrolled proliferation of WBC’s
Immature WBC’s found in the bloodstream are
non-functional
Bone marrow is pre-occupied with the production of ____ therefore _________ formation declines.
WBC’s, RBC’s & platelet
Platelets
Basically cell fragments containing serotonin, calcium, enzymes, ADP and platelet derived growth factor (PDGF). Function to form a temporary plug to seal broken blood vessels.
Originate from hemocytoblasts in the bone marrow. Normal life span approximately 10 days. Kept inactive, or prevented from forming an unnecessary plug by nitric oxide (NO) and prostacyclin in the plasma.
Hemostasis
Defined as the process to stop vascular bleeding. Consists of the following three processes
Following three processes in hemostasis
Vascular spasm, Platelet plug formation, Coagulation
Vascular spasm
Vasoconstriction at site of injury from contraction of smooth muscle in the walls.
Platelet plug formation
Platelets don’t typically stick to each other or unbroken vessels
Coagulation
Blood clotting involving over 30 various clotting factors
Clot Retraction
Following hemostasis, stabilization of the clot by fibrin strands at the site of injury must take place to allow for healing of tissues and prevent the clot from breaking apart too early resulting in further bleeding.
Fibrinolysis
Dissolving of un-needed clots
Plasmin
The natural “clot buster” in the body. Activated by plasminogen
Tissue Plasminogen
Activator (TPA)
secreted by endothelial cells lining blood vessels or injected in patients suspected of having coronary (heart) or cerebral (brain) clots forming.
Unnecessary clotting is also prevented by
1) Smooth Endothelial Lining of blood vessel walls in the lumen
2) Heparin secreted by endothelial cells in the vascular wall
3) Vitamin E quinone (an anticoagulant) also secreted from the endothelial lining (cells)
4) Aspirin
5) Warfarin
Aspirin
Inhibits thromboxane A2, one of the clotting factors
Warfarin
Oral anticoagulant
Thrombus
“Stationary Clot” in an unbroken vessel. Thrombi can block circulation resulting in tissue death (necrosis).
Embolus
A “moving clot” or thrombus in the blood stream
Thrombocytopenia
Deficient number of circulating platelets. Patients show “petechiae” from widespread hemorrhage resulting in purple spots under the skin.
Petechiae
Caused by suppression or destruction of bone marrow (e.g., malignancy, radiation)
Hemophilia
Genetic disorder resulting in a missing gene for one of the coagulation factors
Rh Factor
Individuals with the Rh antigen on the surface of their RBC are Rh-Positive (Rh+). Those without the Rh antigen are therefore Rh-Negative (Rh-).
Universal Donor
“Type-O”, every blood type can receive Type-O blood because, Type-O does not have any antigens (A or B) on the surface of the RBC therefore there will be no coagulation or clotting regardless of any antibodies that may be in the recipient’s blood.
Universal Recipient
“Type-AB” individuals with Type-AB blood can receive any of the blood types (on a short term basis) because they have no plasma antibodies to A or B antigens in their blood. No antibodies means no coagulation or clotting regardless of the blood type or antigen on the surface.
AB
antigens - A, B
antibodies - none
receive - A, B, AB, O
B
antigens - B
antibodies - Anti-A (a)
receive - B, O
A
antigens - A
antibodies - Anti-B (b)
receive - A, O
O
antigens - None
antibodies - Anti-A (a), Anti-B (b)
receive - O
