Endocrine System Flashcards
Located in the anterior neck; it is situated anterior to the trachea and is easily palpated (i.e., you can feel the nodules or enlargement).
Thyroid gland
Butterfly-shaped and has two large lobes connected by a band of tissue called the isthmus (iss-muss).
Thyroid gland
This band of tissue connects the thyroid gland.
Isthmus (iss-muss)
The thyroid gland contains ___ types of cells.
2
The thyroid gland contains two types of cells: the ___ cells, located within the thyroid ___, and the ___ cells, located between the ___.
follicular
follicle
parafollicular
follicles
Composed of many secretory units called follicles.
Thyroid gland
True or false: each type of cell in the thyroid gland secretes a specific hormone.
True
The cavity in each follicle is filled with this clear, viscous substance.
Colloid
Follicular cells secrete ___ thyroid hormones.
2
Follicular cells secrete two thyroid hormones: ___ (___) and ___ (___ or ___).
triiodothyronine (try-eye-oh-doh-thy-roh-neen) / T3
tetraiodothyronine (tet-rah-eye-oh-doh-thy-roh-neen) (T4 or thyroxine)
The term thyroid hormones refers to ___ and ___ collectively.
T3
T4
True or false: the thyroid hormones T3 and T4 have similar functions, although T3 is more potent.
True
The small amount of T4 that enters the cells is converted to ___.
T3
Regulates all phases of metabolism; they increase the release of energy from carbohydrates and fatty acids, increase protein synthesis, and determine the number of calories required to “keep the body running at rest.”
Thyroid hormones
The “keep the body running at rest” is called the ___ ___ ___ (___).
basal metabolic rate
BMR
Determines basal metabolic rate.
Thyroid hormones
Essential for the normal maturation of the nervous system and for normal growth and development; they also play a permissive role in that they are necessary for the proper functioning of all other hormones.
Thyroid hormones
Thyroid Gland. (A) Location; the follicular cells (thyroid follicle) and parafollicular cells.
This system communicates through chemical signals called hormones.
Endocrine System
This system responds more slowly and generally exerts longer-lasting effects.
Endocrine system
The ___ system and its ___ help regulate metabolic processes involving carbohydrates, proteins, and fats.
endocrine
hormones
Play an important role in growth and reproduction and help regulate water and electrolyte balance.
Hormones
When you become hungry, thirsty, hot, or cold, your body’s response includes the secretion of ___.
hormones
Help the body meet the demands of infection, trauma, and stress.
Hormones
Composed of endocrine glands that are widely distributed throughout the body.
Endocrine system
Secrete the chemical substances called hormones.
Endocrine glands
Ductless glands (secrete the hormones directly into the blood and not into ducts). For example, the pancreas secretes the hormone insulin into the blood, which then delivers the insulin to cells throughout the body.
Endocrine glands
Many hormones are also secreted by ___, such as the stomach, kidney, and heart.
organs
An ___ gland, such as the sweat gland, uses ducts or tiny tubes to carry its secretions to the surface of the body.
exocrine
Secrete hormones into the blood and not into ducts.
Endocrine glands
A chemical messenger that influences or controls the activities of other tissues or organs.
Hormone
Chemically classified as either proteins (and protein-related substances) or steroids.
Hormones
True or false: with the exception of secretions from the adrenal cortex and the sex glands, all hormones are protein or protein related.
True
The adrenal cortex and the sex glands secrete ___.
steroids
Major Endocrine Glands of the Body.
Each hormone binds to a specific tissue called its ___ tissue or organ.
target
May be located close to or at a distance from the endocrine gland.
Target tissue
Some hormones, such as thyroid hormone and insulin, have ___ target tissues and therefore exert more widespread or generalized effects.
many
Some hormones such as parathyroid hormone (PTH) have ___ target tissues and therefore exert fewer effects.
few
What Hormones Do. (A) Hormones: aim at target tissues or target organs. (B) Protein hormones and membrane receptors. (C) Steroid hormones and intracellular receptors.
Hormones bind to the ___ sites of the cells of their target tissues.
receptor
The two types of receptors are those located on the outer surface of the cell membrane (___ receptors) and those located within the cell (___ receptors).
membrane
intracellular
True or false: the hormone and its receptor can be compared with a lock-and-key mechanism. The key must fit the lock.
True
Hormones can only stimulate the cells that have their specific ___.
receptors
Generally bind to receptor sites located on the cell membrane.
Protein hormones
The interaction of the protein hormone with its receptor stimulates the production of a second messenger such as ___ ___ ___ (___).
cyclic adenosine monophosphate (cAMP)
sick - lick - a - den - o - seen - mon - o - fos - fate
Helps activate the enzymes in the cell. For example, when epinephrine stimulates its receptors in the heart, it is formed and then stimulates the heart itself.
cyclic adenosine monophosphate (cAMP)
sick - lick - a - den - o - seen - mon - o - fos - fate
This receptor is located intracellularly.
Steroid receptors
Steroid hormones, which are lipid soluble, pass through the plasma membrane of the target cell and bind to receptors in the ___.
nucleus
The steroid-receptor complex then stimulates ___ synthesis.
protein
True or false: newly synthesized protein alters cellular function.
True
Three mechanisms control the secretion of hormones: ___ control loops, ___, and control by the ___ nervous system (___).
feedback
biorhythms (bye - oh - rith - ums)
central - CNS
True or false: normal endocrine function depends on the normal plasma levels of hormones.
True
True or false: life-threatening complications develop when the glands hypersecrete or hyposecrete hormones.
True
The adrenal cortex, a steroid-secreting gland, knows when it has secreted enough steroids through a ___ feedback control loop.
negative
The pattern of adrenocorticotropic hormone (ACTH) and cortisol secretion is one example of a ___ feedback loop. ACTH, secreted by the anterior pituitary gland, stimulates its ___ organ (___ cortex) to secrete cortisol. As blood levels of cortisol increase, the cortisol in the blood chemically ‘tells’ the anterior pituitary gland to slow further secretion of ACTH. The diminished ACTH, in turn, decreases the secretion of cortisol by the ___ cortex.
negative
target
adrenal x2
The following picture is an example of a:
negative feedback loop.
True or false: because the cortisol diminished the secretion of the anterior pituitary gland, the response is referred to as negative feedback control.
True
True or false: over time, the plasma level of cortisol declines as the hormone is degraded and eliminated from the body; the negative inhibition by cortisol is relieved, and ACTH is again secreted.
True
Causes an enhanced response, a self-amplification cycle in which a change is the stimulus for an even greater change in the same direction. For example, during early labor, the head of the baby stretches the cervix, the neck of the uterus. The stretch causes nerve impulses to travel from the cervix to the brain, which in turn causes the secretion of a hormone called oxytocin. The oxytocin is carried by the blood to the uterus, where it stimulates the contraction of the uterus. In response to uterine contraction, the cervix is stretched further by the baby’s head, causing the release of additional oxytocin.
Positive feedback loop
True or false: positive feedback loops are often designed to produce a rapid response.
True
True: negative feedback loops are more common than positive feedback loops.
True
Blood levels of most hormones are also controlled by ___.
biorhythms (bye - oh - rith - ums)
A rhythmic alteration in a hormone’s rate of secretion.
Biorhythm (bye - oh - rith - um)
True or false: some hormones, such as cortisol, are secreted in a circadian rhythm.
True
A 24-hour rhythm; its pattern repeats every 24 hours.
Circadian rhythm (sir - kay - dee - in)
Circa- means ‘around’; -dian means ‘day’
True or false: because of its circadian rhythm, cortisol secretion is highest in the morning hours (peak at 8 AM) and lowest in the evening hours (lowest at midnight).
True
True or false: the female reproductive hormones represent another biorhythm. They are secreted in a monthly pattern-hence, the monthly menstrual cycle.
True
Can be disturbed by travel and alterations in sleep patterns. For example, jet lag and the symptoms of fatigue experienced by persons who work the night shift.
Biorhythms
True or false: more recently, alterations in biorhythms have also been linked to disturbances in cholesterol metabolism and diseases such as cancer. The problem has become so acute that some hospitals have developed staffing schedules based on biorhythms.
True
True or false: sometimes drugs are administered on a schedule that mimics normal biorhythms. For example, steroids are administered in the morning, when natural steroid levels are highest. Coordinating with the natural rhythms increases the effectiveness of the drug and causes fewer side effects. The effect of biorhythms on drug effects is so important that a branch of pharmacology addresses this issue: chronopharmacology. The time of drug administration may have a profound effect on its activity.
True
The CNS helps control the secretion of hormones in two ways: activation of the ___ and stimulation of the ___ nervous system.
hypothalamus (hypo-thal-a-mus)
sympathetic
When we are stressed out, the ___ nervous system (___) causes several of the endocrine glands to secrete stress hormones, thereby alerting every cell in the body to the threat.
central
CNS
True or false: our emotions affect the endocrine system because the central nervous system (CNS) is also the centre of our emotional lives.
True
True or false: stress can cause the menstrual period to occur early or late; it may even cause the cycle to skip a month.
True
Hypophysis (hye-pof-is-sis):
Pituitary gland (pa-too-a-tary)
A pea-sized gland located in a depression of the sphenoid bone on the floor of the cranium.
Pituitary gland (pa-too-a-tary)
The pituitary gland is attached to the undersurface of the hypothalamus by a short stalk called the ___.
infundibulum (in-fin-dib-u-lum)
The pituitary contains two main parts: the ___ pituitary gland and ___ pituitary gland.
anterior
posterior
Pituitary Gland. (A) Hormones and target organs of the anterior and posterior pituitary glands. (B) Relationship of the hypothalamus to the anterior pituitary gland. (C) Relationship of the hypothalamus to the posterior pituitary gland. ACTH, Adrenocorticotropic hormone; ADH, antidiuretic hormone; FSH, follicle-stimulating hormone; GH, growth hormone; LH, luteinizing hormone; PRL, prolactin; TSH, thyroid-stimulating hormone.
The secretions of both the anterior and posterior lobes of the pituitary gland are dependent upon the ___, although in different ways.
hypothalamus (hypo-thal-amus)
The secretion of the ___ pituitary gland is controlled by the hypothalamic secretion of hormones called releasing hormones and release-inhibiting hormones.
anterior
Prolactin-releasing hormone, secreted by the hypothalamus, ___ the pituitary gland to secrete prolactin (PRL).
stimulates
Stimulate the secretion of anterior pituitary hormones.
Releasing hormones
Inhibits the secretion of anterior pituitary hormones.
release-inhibiting hormones
Prolactin-inhibiting hormone (PIH), secreted by the hypothalamus, ___ the secretion of PRL by the anterior pituitary gland.
inhibits
The hypothalamus secretes its hormones into a network of capillaries (tiny blood vessels) that connect the hypothalamus with the ___ pituitary gland. These connecting capillaries are called the ___-___ portal system. Thus, hormones secreted by the hypothalamus flow through the portal capillaries to the ___ pituitary.
anterior
hypothalamic–hypophyseal (hypo-thal-a-mic)-(hypo-fiz-e-ol)
anterior
Composed of glandular epithelial tissue.
Anterior pituitary gland (pa-too-a-tary)
Adenohypophysis (ad-eh-no-hye-pof-i-sis):
Anterior pituitary gland (pa-too-a-tary)
The anterior pituitary gland secretes ___ major hormones. These hormones control other glands and affect many organ systems. In fact, the anterior pituitary affects so many other glands that it is often called the ___ gland.
6
master
The hormones of the anterior pituitary include:
Growth hormone (GH)
The gonadotropins: follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Prolactin (PRL): thyroid-stimulating hormone (TSH) and adrenocorticotropic hormone (ACTH)
Includes thyroid-stimulating hormone (TSH), ACTH, growth hormone (GH), the gonadotropins, and PRL.
Anterior pituitary hormones
Somatotropin or somatotropic hormone:
Growth hormone (GH)
Its primary effects are on the growth of bones, cartilage, and skeletal muscles, thereby determining a person’s size and height.
Growth hormone (GH)
Exerts powerful metabolic effects causing amino acids to be built into proteins and fats to be broken down and used for energy.
Growth hormone (GH)
Stimulates the conversion of protein to glucose (gluconeogenesis), especially during periods of fasting between meals (causing blood glucose levels to rise).
Growth hormone (GH)
True or false: growth hormone (GH) has been used successfully in the treatment of severe burns because it stimulates tissue growth and repair.
True
Affects electrolyte balance: it stimulates the kidneys to reabsorb sodium (Na+), potassium (K+), and chloride (Cl − ) and the digestive tract to absorb dietary calcium. These electrolytes then become available to growing tissue.
Growth hormone (GH)
Stimulates the liver to produce growth stimulants called insulin-like growth factors (or somatomedins).
Growth hormone (GH)
True or false: growth hormone (GH) is secreted primarily during periods of exercise, sleep, and hypoglycemia.
True
Parathyroid glands. Parathyroid hormone (PTH) and three target organs (bone, kidneys, and intestine).
(A) Adrenal glands: adrenal medulla and adrenal cortex. (B) Negative feedback control of the secretion of cortisol. ACTH, Adrenocorticotropic hormone.
Pancreatic regulation of blood glucose: insulin and glucagon.
