Physiology 2

Front 1

The thyroid gland is located ________ and __________ to the trachea, just below the thyroid cartilage (Adam's apple).

Back 1

anterior, lateral

Front 2

The thyroid consists of 2 lobes (one on each side of the trachea). The lobes are connected by a bridge of thyroid tissue called the ________, which is located just below the _________ __________, midway between the apex of the thyroid cartilage and the suprasternal notch.

Back 2

isthmus, cricoid cartilage

Front 3

The superior thyroid artery arises from the __________________________, whereas the inferior thyroid artery arises from the ____________ _________of the subclavian artery.

Back 3

common or external carotid artery, thyrocervical trunk

Front 4

Venous drainage is via multiple surface veins coalescing into superior, lateral, & inferior __________.

Back 4

thyroid veins

Front 5

forms of hypothyroidism characterized by thyroid enlargement (e.g. - ________- ___________ hypothyroidism).

Back 5

iodine deficient

Front 6

On microscopic examination, the thyroid gland is found to consist of a series of ________ _________ of varying size.

Back 6

thyroid follicles

Front 7

The thyroid follicles contain a material called the ________ and are surrounded by a single layer of cuboidal epithelium (_________ _________).

Back 7

colloid, follicular cells

Front 8

The colloid (thyroid follicles contain this material) contains large numbers of ______________ ____________.

Back 8

thyroglobulin molecules; TGB

Front 9

Each thyroid follicle is surrounded by a dense _______ network as well as individual cells called ____________.

Back 9

capillary, parafollicular (C) cells

Front 10

Thyroid hormones are a derivative of what amino acid

Back 10

tyrosine

Front 11

The two types of thyroid hormones __________ (T3) and ______ (T4).

Back 11

triiodothronine, thyroxine

Front 12

A majority of the thyroid hormone secreted by the thyroid gland is ___ (approx. ____%).

Back 12

T4, 95%

Front 13

Most of the ___ released by the thyroid gland is ___, however, is converted to ____ by target tissues

Back 13

T4, T3

Front 14

___ is about 4-5 times more potent than __.

Back 14

T3, T4

Front 15

Thyroid hormones are unique in that they contain ______% of the trace element _____.

Back 15

60-65%, iodine

Front 16

_________ are the only substances in the body that have iodine in their structure

Back 16

thyroid hormones

Front 17

hypothalamus > ____ > pituitary > _______ > thryoid
(hormones)

Back 17

TRH, TSH

Front 18

thryoid synthesis in _________ requires two things: _________ and ________.

Back 18

colloid, iodine, thryoglobulin molecule

Front 19

__________ cells produce T4 and T3.

Back 19

follicular

Front 20

What produces calcitonin

Back 20

parafollicular cells (C cells)

Front 21

Iodine is added to ________: one iodine, ____, two iodines, ____. MIT and DIT are hooked together. DIT+DIT=T4, MIT+DIT=T3.

Back 21

tyrosine, MIT, DIT

Front 22

Colloid can store a lot of thyroid hormone, enough to last _________.

Back 22

8-12 weeks

Front 23

The thionamides, methimazole (Tapazole) and propylthiouracil (PTU), are the primary drugs used to treat ____________.

Back 23

hyperthyroidism

Front 24

MIT and DIT are called:

Back 24

iodotyrosines

Front 25

Antithyroid drugs inhibit ___________ __________and hence decrease the synthesis of thyroid hormone by inhibiting the oxidation of _______, the iodination of _______, and the coupling of iodotyrosines (MIT, DIT).

Back 25

thyroid peroxidase, iodine, tyrosine

Front 26

TSH Actions: 4 things

Back 26

-stimulates iodide pump activity
-activates thyroid peroxidase
-stimulates TGB synthesis
-stimulates growth of thyroid follicles

Front 27

TGB and TBG

Back 27

-thyroglobulin (TGB) molecules
-thyroxine-binding globulin (TBG)

Front 28

There are three major thyroid hormone transport proteins:

The total amount of thyroid hormones bound to these plasma proteins provides a substantial reservoir of T3 and T4.

Back 28

-thyroxine-binding globulin (TBG)
-thyroxine-binding prealbumin (TBPA) or transthyretin
-albumin

Front 29

Thyroid hormones are transported in blood bound to ___________. Although only ____% of T3 and T4 are "free", it is the free fraction that is responsible for hormonal activity.

Back 29

carrier proteins, 0.04%

Front 30

It is also important to emphasize that thyroid hormones act as _______rather than as all-or-none signals that turn processes on or off. Much of what thyroid hormone does is ________, serving to facilitate the actions of other hormones and pathways. Thus, it is easy to forget the role of thyroid hormones in making other hormones (e.g. -- GH, epinephrine, etc.) ________.

Back 30

modulators, permissive, work optimally

Front 31

Attainment of normal adult stature requires optimal amounts of thyroid hormone.

There is no evidence that T3 or T4 acts directly on cartilage or bone cells to signal increased bone formation -- rather, thyroid hormones appear to act permissively or synergistically with _________ and _______________ to promote bone formation.

Back 31

growth hormone, insulin like growth factors

Front 32

The thyroid gland develops very early (_____days after conception); it starts concentrating iodide by about the 11th week of gestation; it begins secreting significant amounts of T3 and T4 around the ________week of gestation.
At the ________week of gestation, T3 and T4 have significant impacts on brain development -- some of the actions of thyroid hormones include growth of the cerebrum, vascularization of the cerebrum, growth of the cerebellum and neuron myelination -- while this thyroid hormone dependent development begins in utero, it is not completed until ____________ of age.

Back 32

24 days, 18 - 20th, 18-20th, 2 to 3 years

Front 33

____________ is one of the preventable causes of mental retardation -- major complications can be prevented if diagnosed early and started on replacement therapy; early diagnosis is difficult because the clinical signs are not apparent at birth and appear gradually; thus it is very important to screen newborns for ________________ and it is a routine newborn screening test in most of the developed countries
Specimens are obtained by heel stick filter-paper blood spot -- the results are more reliable if TSH test is done on day 5 of life and __ test between day 2 and 5 of life; there is a physiologic increase in ___ levels at 2-5 days of life, which is not seen, in hypothyroid infants

Back 33

Congenital hypothyroidism, Congenital hypothyroidism, T4, T4

Front 34

Increased secretion of thyroid hormones exaggerates many of the responses regulated by __________.

Some evidence suggests that thyroid hormones may increase the number of receptors for __________ and ________(beta-adrenergic receptors) in myocardium and other tissues.

Back 34

SNS,epi, norepi

Front 35

________________ -- a measure of oxygen consumption under defined resting conditions -- is highly sensitive to _______ hormone levels.
Oxygen consumption in all tissues except _____, ______, and _______ has been experimentally shown to increase in response to ______ hormones.
Oxygen consumption ultimately reflects activity of mitochondria and is coupled with formation of high-energy bonds in ATP -- splitting of ATP energizes cellular processes and ultimately results in heat production.

Back 35

basal metabolic rate, thyroid, brain, testes, spleen, thyroid

Front 36

Thyroid hormones stimulate carbohydrate utilization in most tissues, glycogenolysis & gluconeogenesis in ________, and glucose absorption from the digestive tract.

Back 36

hypatocytes

Front 37

Thyroid hormones stimulate ________ and __________ of free fatty acids by cells.

Back 37

lipolysis, beta-oxidation

Front 38

Thyroid hormones increase the abundance of ______________ receptors in hepatocyte membranes -- this effectively lowers the amount of ____ in the plasma.

Back 38

LDL, LDL

Front 39

Thyroid hormones help to maintain the secretion of _________ from the kidneys and hence _________.

Back 39

erythropoietin, erythropoiesis

Front 40

Thyroid hormones ________ intestinal motility

Back 40

stimulate

Front 41

The principal signs and symptoms of ____________ are related to increased heat production (e.g. – heat intolerance, sweating) ________ sensitivity (e.g. -- tachycardia, tremor) and other effects of thyroid hormones.

Back 41

hyperthyroidism, adrenergic

Front 42

Exophthalmos occurs with ___________ and is a result of ____________.

Back 42

Grave's Disease, hyperthyroidism

Front 43

examples of hyperthyroidism

Back 43

-Graves' Disease (Diffuse Toxic Goiter)
-Toxic Multinodular Goiter (Plummer's Disease) / Toxic Adenoma
-TSH-Mediated Hyperthyroidism
-Subacute Thyroiditis
-Exogenous and Ectopic Hyperthyroidism

Front 44

_______________ is second only to diabetes mellitus as the most common endocrine disorder in the US, and its prevalence is estimated around __ per 1000 individuals.

Back 44

hypothyroidism, 18

Front 45

________________ is caused by TSH deficiency,

Back 45

secondary hypothyroidism

Front 46

_________________ is caused by TRH deficiency.

Back 46

tertiary hypothyroidism

Front 47

causes of primary hypothyroidism

Back 47

Chronic Autoimmune (Hashimoto's) Thyroiditis
Radioiodine Therapy
External Neck Irradiation
Iodine Deficiency or Excess
Congenital Thyroid Agenesis, Dysgenesis or Defects in Thyroid Hormone Synthesis

Front 48

congenital hypothyroidism, also called:

Affects approx. 1 of every ___ births. Potential causes:

Neonatal screening & thyroid hormone replacement therapy averts permanent disabilities

Back 48

cretinism
400,
-lack of thyroid gland
-abnormal biosynthesis of T3 & T4
-abnormal biosynthesis or secretion of TSH

Front 49

Clinical Manifestations of Hypothyroidism: Many of the symptoms and signs that accompany the _____________________ are similar to those of hypothyroidism. As examples, older patients who are euthyroid may complain of fatigue, cold extremities, dry skin, and constipation.

Back 49

normal aging process

Front 50

bronchocele

Back 50

goiter

Front 51

Calcium (Ca+2) is important for a wide range of intracellular & extracellular biological processes including:

Back 51

-muscle contraction
-exocytosis
-blood clotting
-formation of cardiac action potentials
-enzyme activation
-cell signaling (as in second messenger systems like IP3)
-bone & tooth structure

Front 52

Total serum concentration of calcium in human is maintained between _________ mg/dL. Deviations in either direction are not readily tolerated and, if severe, can be life-threatening

Back 52

8.5 to 10.5 mg/dL

Front 53

About _____ mg of Ca+2 is ingested per day, but only ___ of this amount is absorbed from the small intestine and enters the ECF.

Back 53

1000, 1/3

Front 54

Ca+2 is taken up along the entire length of the small intestine, but uptake is greatest in the _____ and ____.

Back 54

ileum and jejunum

Front 55

Both ionized and complexed calcium pass freely through the glomerular membranes. Normally, ______% of the 10,000 mg of Ca+2 filtered by the glomeruli each day is reabsorbed by the ____________.

Back 55

98-99%, renal tubules

Front 56

The adult human body contains approximately _____ g of Ca+2, about ___% of which is sequestered in bone, primarily in the form of ___________ crystals. In addition to providing structural support, bone serves as an enormous _________ for Ca+2 salts.

Back 56

1000g, 99%, hydroxyapatite, reservoir

Front 57

Each day, about ___ mg of Ca+2 is exchanged between ____ and the ___. Much of this exchange reflects resorption and reformation of bone as the skeleton undergoes constant remodeling.

Back 57

600mg, bone and ECF

Front 58

What are the three definable fractions of Ca+2 in the blood

Back 58

1) ionized or “free” calcium 50%)
2) protein-bound calcium (40%)
3) complexed to citrate & phosphate forming soluble complexes (10%)

Front 59

Both complexed and ionized Ca+2 are ultrafilterable, so that about 60% of the total Ca+2 in blood crosses semi-permeable membranes. Nearly 90% of the protein-bound Ca+2 is bound to ______ and the remainder to globulins. The binding of Ca+2 to albumin is __ dependent.

Back 59

albumin, pH

Front 60

Because it is the ionized fraction of Ca+2 that is physiologically important, it is not surprising that patients who hyperventilate and develop acute respiratory ______ may develop carpal spasm and even seizures due to increased neural excitability.

Back 60

alkalosis

Front 61

The binding of Ca+2 to albumin is __ dependent. Acute acidosis ________ (decreases or increases) binding and (decreases or increases) ionized Ca+2, whereas acute alkalois ________ binding with a consequent _________ in ionized Ca+2.

Back 61

pH, acidosis decreases binding and increases ionized Ca+2, alkalosis increase binding and decreases ionized Ca+2

Front 62

Parathyroid glands are well vascularized and derive their blood supply mainly from the _____________ arteries.

Back 62

inferior thyroid

Front 63

They are well vascularized and derive their blood supply mainly from the inferior thyroid arteries. These glands adhere to the posterior surface of the thyroid gland or occasionally are embedded with the thyroid tissue.

Back 63

parathyroid

Front 64

What are the most predominant cells in the parathyroid glands?

Back 64

The principal or chief cells

Front 65

What the two main functions of the principal or chief cells of the parathyroid gland?

Back 65

a) synthesis & secretion of PTH
b) sensors of minute fluctuations of ECF Ca+2.

Front 66

The function of the second parathyroid cell type, the _______ cells, is unknown. Some recent evidence suggests that they may be degenerated principal cells. Few ______cells are seen before puberty, but their number increases thereafter with age.

Back 66

oxyphil, oxyphil

Front 67

stimulus for secretion is hypocalcemia

Back 67

parathyroid

Front 68

-“straight-chain” protein hormone of 84 amino acids
-½ life in the blood of 2-3 minutes
-metabolized by its target tissues
-metabolites excreted in urine

Back 68

parathyroid

Front 69

What are the 3 tissues the parathyroid works on either directly or indirectly

Back 69

bones (direct), kidney (direct), intestine (indirect)

Front 70

PTH effects on bone (direct)

Back 70

-stimulates existing osteoclast activity
-stimulates new osteoclast production

Front 71

PTH effects on the kidneys (direct)

Back 71

-stimulates the reabsorption of Ca+2 in distal convoluted tubules
-stimulates 1-hydroxylation of 25-hydroxycholecalciferol (i.e. -- activation of Vitamin D)

Front 72

PTH effects on the intestines (indirect)

Back 72

-intestinal uptake of Ca+2 is stimulated by "active" Vitamin D
-PTH has no directs effect on intestinal absorption of Ca+2

Front 73

PTH stimulates 1-Hydroxylation of 25- hydroxycholecalciferol in the ______ (an organ) -- this creates the active form of _______ called 1(a),25 dihydroxycholecalciferol

Back 73

kidney, Vit D

Front 74

The protein hormone (32-amino acids) that is synthesized and secreted by the parafollicular cells of the thyroid gland.

Back 74

calcitonin

Front 75

calcitonin is secreted by what cells of the thyroid gland

Back 75

parafollicula

Front 76

Stimulus for calcitonin secretion in many animals is ____________.

Back 76

hypercalcemia

Front 77

Calcitonin will promptly and dramatically lower the level of ECF Ca+2 by acting on the _____ and _______.

Back 77

bone and kidneys

Front 78

Calcitonin does not appear to be a major factor in calcium homeostasis in humans. Recent evidence has shown that the importance of calcitonin may be limited to protection against excessive bone ________.

Back 78

resorption

Front 79

Possible etiologies for hypercalcemia:

Back 79

-hyperparathyroidism
-bone malignancies
-prolonged immobilization
-excess vitamin D and calcium in the diet

Front 80

An ________ in ECF calcium depresses central and peripheral neural excitability, resulting in mental sluggishness, dulling of consciousness, muscle weakness and hypo-reflexia.

Back 80

increase

Front 81

Increased concentrations of ________ in blood may cause _______ salts to precipitate out of solution because of their low solubility at physiological pH. "Stones" form, especially in the kidney, where they product severe painful damage (renal colic), which can lead renal failure and hypertension.
If the _________ is due to excessive bone resorption, an increased incidence of fractures can also occur.

Back 81

calcium, calcium, hypercalcemia

Front 82

Possible etiologies of hypocalcemia:

Back 82

-surgical removal of parathyroids
-hypoparathyroidism
-vitamin D deficiency
-impaired ability to activate vitamin D

Front 83

When the ECF concentration of _______ (falls or rises) below normal, the nervous system becomes progressively more excitable because of increased permeability of neuronal membranes to sodium. This results in hyper-reflexia as well as spontaneous, asynchronous & involuntary contractions of skeletal muscles (_______).

Back 83

calcium, falls, tetany

Front 84

A typical attack of hypocalcemic tetany involves muscular spasms in the face (____________ sign) and characteristic contortions of the arms and hands (________ sign).

Back 84

Chvostek's sign, Trousseau's sign

Front 85

Pronounced (hypocalcemia or hypercalcemia) may produce more generalized muscular contractions and convulsions. Laryngeal spasm and contraction of respiratory muscles may compromise breathing.

Back 85

hypocalcemia