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Flashcards in SNS - Biology - Endocrimology Deck (50):
1

Hormones
Peptides
Examples
 

1.    ADH – simple, short peptide
2.    Insulin – complex polypeptide
 

2

Hormones
Steroid
Examples
 

1.    Oestrogen
2.    Aldosterone
 

3

Endocrine Glands
A-H
 

Secrete hormones directly into bloodstream
1.    Adrenals
2.    GI glands
3.    Heart
4.    Hypothalamus

4

Endocrine Glands
I-P
 

1.    Kidney
2.    Pancreas
3.    Parathyroids
4.    Pineal
5.    Pituitary
 

5

Endocrine Glands
Q-Z
 

1. Ovaries
2. Testes
3. Thymus
4. Thyroid

6

Endocrine Glands
Adrenal
 

Situated on top of the kidneys
Consist of cortex and medulla
 

7

Endocrine Glands
Adrenal
Cortex
 

•    Anterior pituitary releases ACTH in response to stress, stimulating the adrenal cortex to synthesise and secret corticosteroid hormones – glucocorticoids and sex steroids
•    Renin-angiotensin mechanism controls production of aldosterone
 

8

Corticosteroids

1.    Glucocorticoids
2.    Mineralocorticoids
3.    Cortical sex hormones
 

9

Corticosteroids
Glucocorticoids
 

•    Cortisol, cortisone
•    Involved in glucose regulation and protein metabolism – raise blood glucose levels by promoting protein breakdown and using the products for gluconeogenesis as well as decreasing protein synthesis
 

10

Corticosteroids
Mineralocorticoids
 

•    eg Aldosterone
•    Regulate plasma levels of sodium and potassium and thus extracellular fluid volume
•    Causes active reabsorption of sodium and passive reabsorption of water in the nephron, increasing blood volume and BP.
•    Excess aldosterone results in hypertension therefore
 

11

Corticosteroids
Cortical Sex Hormones
 

•    Adrenal cortex secretes small amounts of androgens with androstenedione and dehydroepiandrosterone in both males and females
•    In males, most androgens produced by testes, in females however, overproduction can have masculinising effects
 

12

Endocrine Glands
Adrenal
Medulla
 

•    Produces catecholamines (adrenaline and noradrenaline)
•    Adrenaline increases conversion of glycogen to glucose in liver and muscle tissue
•    Both NA and adrenaline increase heart rate and force and dilute and constrict blood vessels in such a way as to increase blood supply to skeletal muscle, heart and brain and decrease supply to kidneys, skin and digestive tract
 

13

Endocrine Glands
Pituitary
 

•    Small, trilobed structure at base of brain
•    Two main lobes – anterior and posterior
•    Third lobe – intermediate – is rudimentary
 

14

Endocrine Glands
Pituitary
Anterior
 

•    Synthesises both direct and trophic hormones
•    Regulated by hypothalamic secretions – releasing or inhibiting hormones/factors
 

15

Endocrine Glands
Pituitary
Anterior
Direct Hormones
 

Directly stimulate target organs
1.    GH – bone and muscle growth
2.    Endorphins – NTs which behave like opioids
3.    Prolactin – stimulates milk production and secretion in female mammary glands
 

16

Endocrine Glands
Pituitary
Anterior
Trophic Hormones
 

Stimulate other endocrine glands to release hormones
1.    ACTH – stimulates adrenal cortex to secrete glucocorticoids. Regulated by CRF
2.    TSH = stimulates thyroid to release thyroid hormones such as thyroxine
3.    LH – stimulates ovulation and formation of corpus luteum in females. Stimulates interstitial cells of testes to synthesise testosterone in  males
4.    FSH – stimulates maturation of ovarian follicles and secretion of oestrogen in females. Stimulates maturation of seminiferous tubules and sperm production in males
 

17

Endocrine Glands
Pituitary
Posterior
 

•    Neurohypophysis
•    Doesn’t synthesize but stores and releases peptide hormones produced by neurosecretory cells of the hypothalamus upon AP from hypothalamus
1.    Oxytocin
2.    ADH
 

18

Endocrine Glands
Pituitary
Posterior
Oxytocin
 

•    Secreted during childbirth
•    Increases strength and frequency of uterine contractions
•    Positive feedback mechanism – oxytocin release causes uterine contraction which in turn stimulates the release of more oxytocin. Continues until the child is born
•    Secretion also induced by suckling, as stimulates milk secretion in the mammary glands
 

19

Endocrine Glands
Pituitary
Posterior
ADH
 

•    Increases the permeability of the collecting duct in the nephron to water, promoting water reabsorption and decreasing blood osmolarity by increasing blood volume
•    Secreted when plasma osmolarity increases, as sensed by osmoreceptors in the hypothalamus, or in response to decreased blood volume as sensed by baroreceptors in the circulatory system
 

20

Endocrine Glands
Hypothalamus
 

•    Receives neural transmission from other parts of the brain and peripheral nerves which trigger specific responses from neurosecretory cells
•    Neurosecretory cells regulate pituitary gland secretions via negative feedback and via actions of inhibiting and releasing hormones
 

21

Endocrine Glands
Hypothalamus
Interaction With Posterior Pituitary
 

•    Neurosecretory cells of the hypothalamus synthesize both oxytocin and ADH and transport them via their axons into the posterior pituitary for storage and release

22

Endocrine Glands
Hypothalamus
Interaction With Anterior Pituitary
 

•    Releasing hormones stimulate or inhibit secretions of the anterior pituitary
•    For example, GnRH stimulates release of LH and FSH
•    Releasing hormones are secreted into the hypothalamic-hypophyseal portal system – circulatory pathway from capillaries of the hypothalamus via the portal vein into the anterior pituitary where diverges into a second capillary network
 

23

Endocrine Glands
Thyroid
 

•    Bi-lobed structure located in the ventral surface of the trachea
•    Produces and secretes thyroxine and tri-iodothyronine (thyroid hormones) and calcitonin
 

24

Endocrine Glands
Thyroid
Thyroid Hormones
 

•    Thyroxine (T4) and tri-iodothyronine (T3)
•    Derived from iodination of tyrosine
•    Necessary for growth and neurological development in children
•    Increase rate of metabolism in the body
 

25

Hypothyroidism

•    Little or no secretion of thyroid hormones
•    Symptoms include slowed heart rate and respiratory rate, fatigue, cold intolerance, weight gain
 

26

Cretinism

Hypothyroidism in newborns
Characterised by mental retardation and short stature
 

27

Hyperthyroidism

•    Thyroid over stimulated, resulting in oversecretion of thyroid hormones
•    Symptoms include increased metabolic rate, excessive warmth, sweating, palpitations, weight loss, protruding eyes
•    Thyroid often enlarges – goitre
 

28

Endocrine Glands
Thyroid
Calcitonin
 

•    Decreases plasma Ca2+ by inhibiting release of Ca2+ from the bone
•    Secretion regulated by plasma Ca2+ levels
•    Antagonistic to parathyroid hormone
 

29

Endocrine Glands
Pancreas
 

•    Both exocrine and endocrine
•    Exocrine – performed by cells that secrete digestive enzymes into the small intestines via series of ducts
•    Endocrine – performed by small glandular structures – islets of Langerhans, composed of alpha and beta cells which secrete glucagon and insulin respectively
 

30

Endocrine Glands
Pancreas
Glucagon
 

Stimulates protein and fat degradation, conversion of glycogen to glucose and gluconeogenesis
Serves to increase blood glucose
 

31

Endocrine Glands
Pancreas
Insulin
 

Protein hormone secreted in response to high blood glucose
Stimulates uptake of glucose by muscle and adipose cells, synthesis of fats from glucose and storage of glucose as glycogen in muscle and liver cells
Serves to decrease blood glucose
Antagonistic to glucagon, glucocorticoids, GH and adrenaline
 

32

 Endocrine Glands
Parathyroid
 

•    Four small, pea shaped structures embedded in the posterior surface of the thyroid
•    Synthesize and secrete parathyroid hormone which regulates plasma Ca2+ conc by increasing bone resorption and decreasing Ca2+ excretion in the kidney
•    Ca2+ bound to phosphate in bone, so breakdown releases phosphate as well as Ca2+. Parathyroid hormone compensates for this by stimulating excretion by kidneys
 

33

Endocrine Glands
Kidneys
 

•    When blood volume falls, secrete renin – converts plasma protein angiotensin to angiotensin I.
•    This then converted to angiotensin II which stimulates secretion of aldosterone from adrenal cortex
 

34

Endocrine Glands
Gastrointestinal Glands
 

1.    Gastrin
2.    Secretin
3.    Cholcystokinin
 

35

Endocrine Glands
Gastrointestinal Glands
Gastrin
 

•    Ingested food stimulates stomach to release gastrin
•    Carried to gastric glands and stimulates to secrete HCl
 

36

Endocrine Glands
Gastrointestinal Glands
Secretin
 

•    Released by small intestine when acidic food material enters from the stomach
•    Stimulates secretion of alkaline bicarbonate solution which neutralises the acidic chyme
 

37

Endocrine Glands
Gastrointestinal Glands
Cholecystokinin
 

•    Released from small intestine in response to the presence of fats.
•    Causes contraction of the gallbladder and release of bile into the small intestine.
•    Also travels to the brain’s satiation centre to stimulate the sensation of being ‘full’
 

38

Endocrine Glands
Pineal Gland
 

•    Tiny structure at the base of the brain
•    Secretes melatonin  - unclear role in humans but believed to have a role in circadian rhythms
•    Secretion regulated by light-dark cycles in the environment
 

39

Regulation In Plants

•    Primarily involved in regulation of growth. Produced by actively growing parts such as meristematic tissues of apical region of shoots and roots

1.    Auxins
2.    Anti-auxins
3.    Gibberellins
4.    Ethylene
5.    Inhibitors
6.    Kinins
 

40

Regulation In Plants
Auxins
 

•    Stimulate the production of new xylem cells from cambium
•    Associated with several types of growth pattern

1.    Phototropism
2.    Geotropism
3.    Inhibition of lateral buds
 

41

Phototropism

•    Tendency of shoots to grow towards light
•    When light strikes tip of plant from one side, reduces auxin supply on that side.
•    Thus illuminated side grows more slowly than shaded side
•    Indoleacetic acid is one auxin associated with phototropism
 

42

Geotropism

•    Growth of portions of plants towards or away from gravity

43

Geotropism
Negative
 

•    Causes shoots to grow upwards, away from the acceleration of gravity
•    Gravity increases auxin conc on lower side of horizontally placed plant while conc on upper side decreases
•    Stimulates cells on lower side to elongate faster than cells of upper side causing the plant to grow vertically
 

44

Geotropism
Positive
 

•    Causes roots to grow downwards
•    Horizontally placed roots also have higher auxin conc on lower side than upper, but effect is opposite to effect on stems – cells exposed to higher auxin conc are inhibited from growing, causing roots to turn downwards
 

45

Inhibition of Lateral Buds

•    Auxins produced in terminal bud of plant’s growing tip move downwards in the shoot and inhibit development of lateral buds
•    Conversely, auxins initiate the formation of lateral roots while inhibit root elongation
 

46

Regulation In Plants
Gibberelins
 

•    Stimulate rapid stem elongation, particularly in plants which normally don’t grow tall
•    Inhibit formation of new roots and stimulate production of new phloem cells by the cambium
•    Also terminate dormancy of seeds and buds
•    Induce some biennial plants to flower during first year of growth
 

47

Regulation In Plants
Kinins
 

•    Promote cell division
•    For example, kinetin – ratio of kinetin to auxin is particularly important in determination of timing of differentiation of new cells. Action is enhanced when auxin is present
 

48

Regulation In Plants
Ethylene
 

•    Stimulates fruit ripening
•    Also induces senescence
 

49

Regulation In Plants
Inhibitors
 

•    Block cell division and serve important roles in growth regulation
•    Particularly important to maintenance of dormancy of lateral buds and seeds during autumn and winter
•    Break down gradually with time
•    For example, abscisic acid
 

50

Regulation In Plants
Anti-Auxins
 

•    Regulate activity of auxins
•    For example, indoleacetic acid oxidase regulates conc of indoleacetic acid. Increased conc of indoleacetic acid increases production of indoleacetic acid oxidase
 

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