Chemical coordination and integration 2 Flashcards
what is parathyroid gland
In humans, four parathyroid glands are present on the back side of the
thyroid gland, one pair each in the two lobes of the thyroid gland (Figure
22.3b). The parathyroid glands secrete a peptide hormone called
parathyroid hormone (PTH). The secretion of PTH is regulated by the
circulating levels of calcium ions.
Parathyroid hormone (PTH) increases the Ca2+ levels in the blood. PTH
acts on bones and stimulates the process of bone resorption (dissolution/
demineralisation). PTH also stimulates reabsorption of Ca2+ by the renal
tubules and increases Ca2+ absorption from the digested food. It is, thus,
clear that PTH is a hypercalcemic hormone, i.e., it increases the blood
Ca2+ levels. Along with TCT, it plays a significant role in calcium balance
in the body
explain the thymus gland and hormoens
The thymus gland is a lobular structure located between lungs behind
sternum on the ventral side of aorta. The thymus plays a major role in
the development of the immune system. This gland secretes the peptide
hormones called thymosins. Thymosins play a major role in the
differentiation of T-lymphocytes, which provide cell-mediated
immunity. In addition, thymosins also promote production of antibodies
to provide humoral immunity. Thymus is degenerated in old individuals
resulting in a decreased production of thymosins. As a result, the immune
responses of old persons become weak.
differentiate humoral and cell mediated immunity
cell mediated:
consists of t-lymphocytes
the t lymphicyets release toxins to neutralise pathogen
humoral:
- the cell releases antibodies to attack the pathogen
-consists of blymphyctes
what are the adrenal glands
Our body has one pair of adrenal glands, one at the anterior part of each
kidney (Figure 22.4 a). The gland is composed of two types of tissues.
The centrally located tissue is called the adrenal medulla, and outside
this lies the adrenal cortex
what id addisons’s disease
Underproduction of hormones by the adrenal cortex alters
carbohydrate metabolism causing acute weakness and fatigue leading
to a disease called Addison’s disease.
what hormones are released by adrenal medulla
The adrenal medulla secretes two hormones called adrenaline or
epinephrine and noradrenaline or norepinephrine. These are
commonly called as catecholamines. Adrenaline and noradrenaline are
rapidly secreted in response to stress of any kind and during emergency
situations and are called emergency hormones or hormones of Fight
or Flight.
functions of stress hormones
These hormones increase alertness, pupilary dilation,
piloerection (raising of hairs), sweating etc. Both the hormones increase
the heart beat, the strength of heart contraction and the rate of respiration.
Catecholamines also stimulate the breakdown of glycogen resulting in an increased concentration of glucose in blood. In addition, they also
stimulate the breakdown of lipids and proteins.
different layers of
The adrenal cortex can be divided into three layers, called zona
reticularis (inner layer), zona fasciculata (middle layer) and zona
glomerulosa (outer layer). The adrenal cortex secretes many hormones,
commonly called as corticoids.
The corticoids, which are involved in
carbohydrate metabolism are called glucocorticoids. In our body, cortisol
is the main glucocorticoid. Corticoids, which regulate the balance of water
and electrolytes in our body are called mineralocorticoids. Aldosterone is
the main mineralocorticoid in our body.
give the functions of glucocorticoids and cortisol
Glucocorticoids stimulate gluconeogenesis, lipolysis and proteolysis;
and inhibit cellular uptake and utilisation of amino acids. Cortisol is also
involved in maintaining the cardio-vascular system as well as the kidney
functions. Glucocorticoids, particularly cortisol, produces antiinflammatory reactions and suppresses the immune response. Cortisol
stimulates the RBC production.
what is the function of aldosterone
Aldosterone acts mainly at the renal
tubules and stimulates the reabsorption of Na+
and water and excretion
of K+
and phosphate ions. Thus, aldosterone helps in the maintenance of
electrolytes, body fluid volume, osmotic pressure and blood pressure.
Small amounts of androgenic steroids are also secreted by the adrenal
cortex which play a role in the growth of axial hair, pubic hair and facial
hair during puberty.
which cells secrete hormones in pancreas
Pancreas is a composite gland (Figure 22.1) which acts as both exocrine
and endocrine gland. The endocrine pancreas consists of ‘Islets of
Langerhans’. There are about 1 to 2 million Islets of Langerhans in a
normal human pancreas representing only 1 to 2 per cent of the pancreatic
tissue. The two main types of cells in the Islet of Langerhans are called
α-cells and β-cells. The α-cells secrete a hormone called glucagon, while
the β-cells secrete insulin.
explain the functions of glucagon
Glucagon is a peptide hormone, and plays an important role in
maintaining the normal blood glucose levels. Glucagon acts mainly on
the liver cells (hepatocytes) and stimulates glycogenolysis resulting in an
increased blood sugar (hyperglycemia). In addition, this hormone
stimulates the process of gluconeogenesis which also contributes to
hyperglycemia. Glucagon reduces the cellular glucose uptake and
utilisation. Thus, glucagon is a hyperglycemic hormone.
define:
(i) glycogenolysis
(ii)gluconeogensis
(iii) glycogenesis
(i) break down of glycogen to glucose
(ii) formation of carb from non carbohydrate substrate
(iii) glycogensis is the formation of glycogen from glucose
give the functions of insulin
Insulin is a peptide hormone, which plays a major role in the
regulation of glucose homeostasis. Insulin acts mainly on hepatocytes
and adipocytes (cells of adipose tissue), and enhances cellular glucose
uptake and utilisation. As a result, there is a rapid movement of glucose
from blood to hepatocytes and adipocytes resulting in decreased blood
glucose levels (hypoglycemia). Insulin also stimulates conversion of
glucose to glycogen (glycogenesis) in the target cells. The glucose
homeostasis in blood is thus maintained jointly by the two – insulin and
glucagons.
what is diabetes melltisu
Prolonged hyperglycemia leads to a complex disorder called diabetes
mellitus which is associated with loss of glucose through urine and
formation of harmful compounds known as ketone bodies. Diabetic
patients are successfully treated with insulin therapy.
