BIOL 2402 A&P-2 UNIT 1 Lecture Exam Study Guide

What is a hormone?

a long distance chemical signal that travels in the blood or lymph

What are a hormone's main functions?

serve as messengers, controlling and coordinating activities throughout the body

What are endocrine glands?

ductless glands that produce hormones.

have a rich vascular and lymphatic drainage that receives the hormones and are in cords and branching networks.

What do endocrine glands secrete?

hormones directly into the bloodstream

Major examples of endocrine glands?

pituitary, thyroid, parathyroid, adrenal, and pineal glands

How is the endocrine system different from the action of the nervous system?

initiates responses slowly

long-duration responses

acts via hormones released into the blood

acts at diffuse locations-targets can be anywhere blood reaches

hormones act over long distances

Location and identification of endocrine glands in the body

Distinguish between hormones, autocrines and paracrines

• Hormones: long-distance chemical signals; travel in blood or lymph

• Autocrines: chemicals that exert effects on same cells that secrete them

• Paracrines: locally acting chemicals that affect cells other than those that secrete them

Chemical structure of amino acid-based

Amino acid derivatives: peptides (short chains of amino acids) and proteins (long chains of amino acids)

Chemical structure of steroids

Synthesized from cholesterol

Of the hormones produced by major endocrine organs, only Gonadal and adrenocortical hormones are steroids.

What are target cells?

tissues with receptors for a specific hormone

Two major mechanisms by which hormones bring about their effects on target tissues

(1) Water-soluble hormones (all amino acid-based hormones except thyroid hormone), cannot enter the target cells, act on plasma membrane receptors

(2) Lipid-soluble hormones (steroid and thyroid hormones), act on intracellular receptors that activate genes

How does a hormone communicate with its target cell?

Depends on the chemical nature of the hormone and the cellular location of the receptor

1. Water soluble hormones(all amino acid based hormones except thyroid)Act on receptors in the plasma membrane. These receptors are usually coupled via regulatory molecules called G proteins to one or more intracellular second messengers which mediate the target cell's response.

- cannot enter the cell

2. Lipid soluble hormones(steroid and thyroid hormones)

- Act on receptors inside the cell, which directly activate genes.- can enter the cell

Where are the receptors? Outside or inside the cell?

Water soluble hormones receptors are outside the cell

Lipid soluble hormones receptors are inside the cell

water soluble hormones

(all amino acid-based hormones except thyroid hormone)

Act on plasma membrane receptors

Act via G protein second messengers

Cannot enter cell

lipid soluble hormones

(steroid and thyroid hormones)

Act on intracellular receptors that directly activate genes

Can enter cell

Three types of endocrine gland stimuli with examples

1. Humoral Stimulus-Cells of the parathyroid glands monitor the body's blood CA2+, glucose, and low Na+ or high K+ levels and release parathyroid hormones as need.

2. Neural Stimulus-the response to stress. The sympathetic nervous system stimulates the adrenal medulla to release norepinephrine and epinephrine.

3. Hormonal Stimulus-releasing and inhibiting hormones produced by the hypothalamus regulate the secretion of most anterior pituitary hormones, in turn, stimulate other endocrine organs to release their hormones.

What are the three factors that influence activation of a target cell by a hormone?

1. Blood levels of hormone

2. Relative number of receptors on/in target cell

3. Affinity (strength) of binding between receptor and hormone

Up-regulation

target cells form more receptors in response to low hormone levels

Down-regulation

target cells lose receptors in response to high hormone levels

Desensitizes the target cells to prevent them from overreacting to persistently high levels of hormone

Half-life

time required for level of hormone in blood level to decrease by half - varies anywhere from fraction of a minute to a week, depending on hormone

Onset (Hormones have different response times:)

Some responses are immediate

Some, especially steroid, can take hours to days

Some are inactive until they enter target cells

duration of hormone activity

(The duration of response is usually limited)

Ranges from 10 seconds to several hours

Effects may disappear rapidly as blood levels drop, but some may persist for hours at low blood levels

Synergism:

more than one hormone produces same effects on target cell, causing amplification

Example: glucagon and epinephrine both cause liver to release glucose

Antagonism:

one or more hormones oppose(s) action of another hormone

Example: insulin and glucagon

Permissiveness:

one hormone cannot exert its effects without another hormone being present

Example: reproductive hormones need thyroid hormone to have effect

Hypothalamus and pituitary interactions (posterior pituitary)

Hypothalamus and pituitary interactions (anterior pituitary)

Anterior pituitary (adenohypophysis)

consists of glandular tissue

Posterior pituitary (neurohypophysis):

composed of neural tissue that secretes neurohormones

Summary of posterior pituitary hormones

Summary of anterior pituitary hormones

1. Growth hormone (GH)

2. Thyroid-stimulating hormone (TSH)

3. Adrenocorticotropic hormone (ACTH)

4. Follicle-stimulating hormone (FSH)

5. Luteinizing hormone (LH)

6. Prolactin (PRL)

(look in page 612-613 of the textbook for more information)

Oxytocin (OXT) (major effects on their target cell)

Strong stimulant of uterine contractions released during childbirth

Also acts as hormonal trigger for milk ejection - letdown reflex

Both are positive feedback mechanisms

Antidiuretic hormone (ADH) (major effects on their target cell)

Hypothalamus contains osmoreceptors that monitor solute concentrations

If solute concentration too high, posterior pituitary triggered to release stored ADH

Targets kidney tubules to reabsorb more water to inhibit or prevent urine formation

Release also triggered by low blood pressure Inhibited by alcohol and diuretics

Growth hormone (GH) (major effects on their target cell)

Has direct actions on metabolism and indirect growth-promoting actions

It makes tissues like muscles, bones, liver, and cartilage grow

Thyroid-stimulating Hormone (TSH) (major effects on their target cell)

Stimulates normal development and secretory activity of thyroid

Adrenocorticotropic hormone (ACTH) (major effects on their target cell)

stimulates adrenal cortex to release corticosteroids

Follicle-stimulating hormone (FSH) (major effects on their target cell)

stimulates production of gametes (egg or sperm)

luteinizing hormone (LH) (major effects on their target cell)

promotes the production of gonadal hormones

1. In females, LH helps mature follicles of egg, triggers ovulation and release of estrogen and progesterone

2. In males, LH stimulates the production of testosterone

Prolactin (PRL) (major effects on their target cell)

Stimulates milk production in females

Know which releasing and inhibiting hormones secreted by the hypothalamus leads to the secretion of their corresponding hormones by the anterior pituitary

growth hormone-releasing hormone (GHRH)

growth hormone-inhibiting hormone (GHIH)

thyroid releasing hormone (TRH)

corticotropic hormone (CRH)

gonadotropin-releasing hormone (GnRH)

Prolactin inhibiting hormone (PIH)

Growth-promoting and metabolic actions of GH

Regulation of thyroid hormone secretion

location and structure of thyroid gland

just below larynx, sits on the anterior surface of the trachea.has right and left lateral lobes. has a very rich blood supply.

Follicular cells - hormones produced?

the glycoprotein thyroglobulin and the thyroid hormone

parafollicular cells - hormones produced?

calcitonin

Thyroid hormones

Body's major metabolic and Iodine-containing amino hormone

Thyroid Hormone (TH) found in two forms

T4 (thyroxine) and T3 (triiodothyronine)

T4 (thyroxine)

major form with four bound iodine atoms

T3 (triiodothyronine)

form with three bound iodine atoms

Major effects of thyroid hormones

1. Increases basal metabolic rate (BMR) and heat production

2. Regulates tissue growth and development

Critical for normal skeletal and nervous system development and reproductive capabilities

3. Maintains blood pressure

Increases adrenergic receptors in blood vessels

Thyroid Disorders

myxedema, goiters & Grave's disease

Myxedema

Symptoms include low metabolic rate, thick and/or dry skin, puffy eyes, feeling cold, constipation, edema, mental sluggishness, extreme tiredness or lethargy

Goiters

Thyroid gland enlarges due to lack of iodine

Grave's disease

An autoimmune disease that happens when the body makes abnormal antibodies directed against thyroid follicular cells

Symptoms: elevated metabolic rate, sweating, rapid and irregular heartbeats, nervousness, and weight loss despite adequate food

Role of calcitonin in calcium regulation

1. Decreases blood Ca2+ levels

2. Inhibits osteoclast activity and prevents release of Ca2+ from bone matrix

3. Stimulates Ca2+ uptake and incorporation into bone matrix

Role of parathyroid hormone (PTH) hormones in calcium regulation

most important hormone in Ca2+ homeostasis Response: Increases blood Ca2+ levels

Secreted in response to low blood levels of Ca2+

• Target organs: skeleton, kidneys, and intestine

Structure of adrenal glands

Capsule

Zona glomerulosa produce Mineralocorticoids

Zona fasciculata produce Glucocorticoids

Zona reticularis produce Gonadocorticoids

Adrenal medula produce catecholamines

Hormones produced from the adrenal cortex and medulla

mineralocorticoids, glucocorticoids, gonadocorticoids, and catecholamines

Mineralocorticoids (aldosterone)

Regulate electrolyte concentrations (primarily Na+ and K+) in ECF

Stimulates Na+ reabsorption by kidneys - results in increased blood volume and blood pressure

Stimulates K+ elimination by kidneys

decrease urine output

Glucocorticoids (cortisol)

Influence metabolism of most cells and helps resist stressors

Keep blood glucose levels relatively constant

Maintain blood pressure by increasing action of vasoconstrictors

Gonadocorticoids (Adrenal Sex Hormones)

weak androgens convert to testosterone

1. Onset of puberty and appearance of secondary sex characteristics

2. Sex drive in women

3. Source of estrogens in postmenopausal women

catecholamines (epinephrine (80%) and norepinephrine (20%))

major effects from the adrenal medulla:

1. Vasoconstriction

2. Increased heart rate

3. Increased blood glucose levels

4. Blood diverted to brain, heart, and skeletal muscle

Aldosterone regulation (especially the Renin-Angiotensin-Aldosterone mechanism)

1. Renin-angiotensin-aldosterone mechanism (Decreased blood pressure stimulates special cells in kidneys. These cells release renin into blood. Renin cleaves angiotensinogen, that triggers an enzyme cascade, resulting in conversion to angiotensin I to angiotensin II (Ang-II). Ang-II is a potent stimulator of aldosterone release)

2. Plasma concentration of K+ (Increased K+ directly influences zona glomerulosa cells to release aldosterone)

3. ACTH (Can cause small increases of aldosterone during periods of increased stress)

4. Atrial natriuretic peptide (Secreted by heart in response to high blood pressure. Blocks renin and aldosterone secretion to decrease blood pressure)

Cushing's syndrome

increases too much glucose

Causes: tumor on pituitary, lungs, pancreas, kidney, or adrenal cortex

Stress and the adrenal gland (short term stress)

The hypothalamus activates the adrenal medulla via neural stimuli

Stress and the adrenal gland (long term stress)

The hypothalamus activates the adrenal cortex via hormonal stimuli. This greatly reinforces the continuing short-term stress response.

Pancreas structure and different cell populations

Triangular gland located partially behind stomach and between the kidneys

It has Acinar cells (exocrine) produce enzyme-rich juice for digestion

It has Pancreatic islets that produce:

Alpha cells which produce glucogen

Beta cells which produce insulin

Insulin and glucagon regulation of blood glucose

How does insulin work to reduce blood glucose levels?

1. Enhances membrane transport of glucose into all cells; catalyze oxidation of glucose for ATP production - first priority!!

2. Liver: Convert glucose to stored form glycogen = Glycogenesis

3. Adipose tissue: Convert glucose to fat

Factors that influence insulin release?

1. Elevated blood glucose levels: primary stimulus

2. Rising blood levels of amino acids and fatty acids

3. "Fed state" - Release of acetylcholine by parasympathetic nerve fibers

4. "Anti-insulin" hormones - glucagon, epinephrine, growth hormone, thyroxine, glucocorticoids

5. Sympathetic nervous system inhibit insulin release

Diabetes mellitus (DM)

when hyposecretion or the absence of insulin causes high sugar levels - Type 1

when high blood sugars are not affected by insulin - Type 2

What are the three cardinal signs of DM?

1. Polyuria: huge urine output

2. Polydipsia: excessive thirst

3. Polyphagia: excessive hunger and food consumption

Consequences of insulin deficit

transport (functions of blood)

1. Delivering O2 and nutrients to body cells

2. Transporting metabolic wastes to lungs and kidneys for elimination

3. Transporting hormones from endocrine organs to target organs

regulation (functions of blood)

1. Maintaining body temperature by absorbing and distributing heat

2. Maintaining normal pH using buffers; alkaline reserve of bicarbonate ions

3. Maintaining adequate fluid volume in circulatory system

protection (functions of blood)

1. Preventing blood loss - Plasma proteins and platelets in blood initiate clot formation

2. Preventing infection - Antibodies, Complement proteins, White blood cells

plasma

nonliving liquid portion of blood

55% of whole blood

erythrocytes (formed element)

red blood cells, or RBCs

45% of whole blood

leukocytes (formed element)

white blood cells, or WBCs

greater than 1% of whole blood

Platelets (thrombocytes) (formed element)

Thin, whitish layer between RBCs and plasma layers

greater than 1% of whole blood

What comprises the buffy coat?

leukocytes and platelets

Composition of plasma

90% water

8% plasma proteins

1% other solutes

composition of plasma proteins

60% albumin

36% globulin

4% fibrinogen

What is hematocrit?

percent of blood volume that is RBCs

Structure and function of RBCs

• RBCs are dedicated to transport oxygen and carbon dioxide throughout the body

Structure of hemoglobin, role in oxygen binding/transport

Hemoglobin binds reversibly with oxygen

Every hemoglobin molecule can bind a maximum of four O2 molecules

oxyhemoglobin (ruby red)

a protein that is produced by O2 loading in lungs

deoxyhemoglobin or reduced hemoglobin (dark red)

a protein that is produced by O2 unloading in tissues

carbaminohemoglobin

a protein that is produced by CO2 loading in tissues and then being filter through the lungs

Stages of Erythropoiesis

Hematopoietic stem cell

proerythroblast

basophilic erythroblast

polychromatic erythroblast

orthochromatic erythroblast

reticulocyte

erythrocyte. (7 sequences).

Role of erythropoietin (EPO) in erythropoiesis

stimulates formation of RBCs

Life cycle of RBCs, fate and destruction

RBCs live from 100 to 120 days

As they get older they git rigid and stiff

Hemoglobin begins to degenerate

Macrophages in spleen and liver engulf and breakdown dying RBCs

Anemia

A disorder where blood has abnormally low O2-carrying capacity that is too low to support normal metabolism

Three groups based on cause:

I. Blood loss

II. Not enough RBCs being produced

III. Too many RBCs being destroyed too quickly

Anemia (Blood loss)

1. Hemorrhagic anemia

Major causes: Rapid blood loss (ex.: severe wound)

Treatment: blood replacement

2. Chronic hemorrhagic anemia

Major causes: Slight but persistent blood loss (ex.: hemorrhoids)

Treatment: problem must be treated to stop blood loss

Anemia (Not enough RBCs being produced)

1. Iron-deficiency anemia

Major causes: hemorrhagic anemia, low iron intake or impaired absorption

Treatment: iron supplements

2. Pernicious anemia

Major causes: low B12 RBCs intake that results in large macrocytes

Treatment: B12 injections

3. Renal anemia

Major causes: lack of EPO

Treatment: synthetic EPO

4. Aplastic anemia

Major causes: drugs, chemicals, radiation, or viruses

Treatment: short-term with transfusions, long-term with transplanted stem cells

Anemia (Too many RBCs being destroyed too quickly)

1. Premature lysis or RBC's (hemolytic anemias)

Major causes: incompatible transfusions, infections, or hemoglobin abnormalities

Treatment:

2. Thalassemias

Major cause: One globin chain is absent or faulty

Treatment: Very severe cases may require monthly blood transfusions

3. Sickle-cell anemia

Major cause: a hereditary disease

Treatments: inject Hydroxyurea drug

Polycythemia

Abnormal amount of RBCs

Increases blood viscosity causing sluggish blood flow

Treatment: therapeutic phlebotomy

Percentages of leukocytes in normal blood

Granulocytes

Neutrophils (50-70%)

Eosinophils (2-4%)

Basophils (0.5-1%)

Agranulocytes

Lymphocytes (25-45%)

Monocytes (3-8%)

Summary of formed elements