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Biosciences 2 > Endocrinology > Flashcards

Endocrinology Flashcards

1
Q

What is endocrinology?

A

Study of endocrine glands and their secretions

Hormones help maintain normal homeostasis

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2
Q

What do hormones do?

A

Tell cells what to do
Results in the production of a protein that has some effect on the body
Most have another hormone that regulates its’ secretion

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3
Q

What are the elements of the enodcrine system?

A 
Pituitary
Pineal
Thyroid
Thymus
Adrenal
Pancreas
Ovaries/Testes
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4
Q

What is the pituitary gland?

A

The ‘master gland’- has extensive influence on other organs
Linked to the hypothalamus; stimulates and inhibits pituitary hormones
Responsible for making hormones to stimulate organs to act

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5
Q

What are the 4 stages of growth?

A 
Foetal 
Infancy
Childhood
(GH/GF axis 4-8cm/yr)
Puberty/Adolescence 
(sex steroids and GH 8-10cm/yr)
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6
Q

Describe growth in utero

A

Growth dependent on the mother’s genetics. Also the mother’s health. Placental nutrition and function
Most rapid period of growth
Peaks at 10cm per month around 13-18 weeks gestation

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7
Q

What are the maternal factors of growth?

A

Mother’s health will impact the baby; i.e. smoking and alcohol
Chronic disease, i.e. hypertension

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8
Q

Describe growth in infancy

A

Linear growth is initially rapid; 25cm in the first year of life
Continuation of the fetal growth pattern
Growth rate declines
Most important influencing factor is nutrition

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9
Q

Describe growth in childhood

A 
Period of relatively steady growth
Body proportions more adult like
Children are slender, leggy and agile
Little difference in the growth rates between girls and boys
Growth rate 4-7cm/year
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10
Q

What are the impacts of the endocrine system on growth?

A

Nutrition becomes less important
Hormonal influences;
-principle regulating mechanisms for linear growth
-growth hormone
-insulin-like growth factor (IGF-1)
-thyroid hormone;
hypothyroid, growth rate and short stature

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11
Q

What is adrenarche?

A

onset of androgen dependent changes, e.g. pubic and axillary hair, BO, acne

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12
Q

What is thelarche?

A

onset of female breast development

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13
Q

What is puberty?

A

development of secondary sexual characteristics. Attain reproductive capacity

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14
Q

What is menarche

A

onset of menstruation

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15
Q

What factors influence the timing and onset of puberty?

A

genetic background
environment
general health of child

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16
Q

Definition of normal puberty

A

Girls- puberty development after the 8 years (mean 10 year)

Boys- puberty development after the age of 9 years (mean 12 years)

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17
Q

What are the clinical aspects of normal puberty?

A

Females: Breast development
Males: Genital development; testicular volume
Both: Pubic hair development
Axillary hair development

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18
Q

Describe the normal control of water balance

A

Stability of plasma concentration is controlled, in part, by hypothalamic centres that regulate thirst

Thirst mechanism- stimulates intake of free water and stimulates ADH release

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19
Q

Describe anti-diuretic hormone

A

Synthesised by the hypothalamus and stored in the posterior pituitary gland

Stimulates the distal and collecting tubules in the kidneys to increase the reabsorption of the free water into the cardiovascular system (maintains physiologic osmolality)

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20
Q

How does ADH work?

A

The hypothalamus senses low blood volume and increased serum osmolality and signals the pituitary gland

The pituitary gland secrets ADH into the bloodstream

ADH causes the kidneys to retain water

Water retention boosts blood volume and decreases serum osmolality

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21
Q

How does the nephron regulate fluid and electrolytes?

A

GLOMERULUS filters fluid at a rate of 180L/day
Acts as a bulk filter to pass along protein-free and red blood cell-free filtrate (liquid that has been filtered)

PROXIMAL TUBULE has freely permeable call membranes
Reabsorbs most electrolytes, glucose, urea and amino acids
Carries large amounts of water with electrolytes back to circulation
Reduces water concentration of filtrate by 70%

LOOP OF HENLE contains a high concentration of salts, mostly sodium
Further concentrates filtrate because of water lost by osmosis
Pulls chloride and sodium out of filtrate without water and reabsorbs them in ascending limb
Causes filtrate to become more dilute as it moves into distal tubule

DISTAL TUBULE reabsorbs water and concentrates urine as a result of antidiuretic hormone action
Reabsorbs sodium and water
Secretes potassium as a result of aldosterone action

COLLECTING DUCT has ADH which absorbs water
Absorbs or secretes potassium, sodium, urea, hydrogen ions, and ammonia, according to the body’s needs

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22
Q

What is plasma osmolality?

A

Measures the concentration of all chemical particles found in the fluid part of the blood
Normal levels 285-295mOsm/L

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23
Q

What is urine osmolality?

A

Used to measure the number of dissolved particles per unit of water in the urine
Normal levels 500-800mOsm/kg water
Large values = concentrated
Low values= dilute

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24
Q

What is diabetes insipidus?

A

An acute or chronic condition
Inadequate secretion of ADH from the posterior pituitary gland (cranial)
Insufficient renal response to adequate levels of ADH (nephrogenic) causes the kidneys to make a lot of urine
Causes in CDI- cerebral malformation
acquired disease
familial

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25
Q

What do thyroid hormones effect?

A

Growth
Neurological development
Metabolism
Cardiovascular function

26
Q

What thyroid hormones are released by the hypothalamus?

A

Thyrotrophin Releasing Hormone (TRH)

27
Q

What thyroid hormones are released by the pituitary gland?

A

Thyroid Stimulating Hormone (TSH)

28
Q

What thyroid hormones are released by the thyroid gland?

A

Thyroxine (T4)

Tri-iodothyronine (T3)

29
Q

What is the hypothalamo-pituitary adrenal axis?

A

Complex set of direct influences and feedback interactions
Corticotrophin releasing hormone stimulates the release of adrenocorticotrophic hormone which releases cortisol which acts back onto the hypothalamus and pituitary

30
Q

What are the layers of the adrenal gland?

A 
OUTER LAYER (cortex)
Zona glomerulosa (mineralcorticoids)
Zona fasciculata 
(glucocorticoids)
Zona reticularis
(sex steroids)
-All steroid hormones from cholesterol 
INNER LAYER (completely surrounded by cortex)
medulla (catecholamines)
31
Q

Outline the properties of the zona glomerulosa

A

Contains mineralcorticoids such as:

Aldosterone (regulated blood pressure by regulating salt retention)

32
Q

What is hyperaldosteronism?

A

Due to excessive secretion of mineralcorticoids.
Can cause excessive reabsorption of sodium chloride and water, causing increased blood volume and hypertension.
Excess excretion of potassium, causing hypokalaemia, which leads to cardiac arrhythmias, alkalosis, syncope and muscle weakness

33
Q

What is hypoaldosteronism?

A

A low amount of aldosterone results in failure of the kidneys to regulate sodium, potassium and water excretion, leading to

  • Blood sodium deficiency (hyponatraemia) and potassium excess (hyperkalaemia)
  • dehydration, low blood volume and low blood pressure
34
Q

What is aldosterone?

A

Helps regulate the salt levels in the body:

  • Amount of salt intake varies with what we eat
  • The job of the kidneys is to prevent salt accumulation; this is to prevent increased blood pressure and fluid retention
  • Additionally they want to regulate and prevent salt loss which would cause vomiting and dehydration
  • Aldosterone makes the kidney conserve salt
  • If there is not enough salt in the diet, aldosterone production increases
  • If there is too much aldosterone amount is reduced
35
Q

Describe the properties of the zona fasciculata

A

Produces glucocorticoids including cortisol

This is the body’s natural steroid.

36
Q

What are the 3 main functions of cortisol?

A
  • Helps control blood sugar levels
  • Helps body deal with stress
  • Helps to control BP and blood circulation
37
Q

Describe the properties of the zona reticularis

A

Produces sex steroids/androgens

  • DHEA (dehydroepiandrosterone)
  • Androstenedione (secondary sexual characteristics)
  • Produced by adrenal cortex in both sexes
  • Also produced by the testes in males
  • Adrenal androgens contribute to the formation of pubic hair
38
Q

Describe the properties of the adrenal medulla

A

Produce catecholamines-
ADRENALINE-
Released in response to signals from the sympathetic nervous system
Increases blood sugar, muscle glycogen breakdown, blood flow to muscle, respiration
NORADRENALINE-
Similar effects to adrenaline, as well as maintains BP
DOPAMINE-
Precursor to adrenaline and noradrenaline
Is a neurotransmitter

39
Q

What are the 2 categories of stressors?

A

Psychosocial and physical

40
Q

What are some psychosocial stressors?

A

Bereavement, mental illness, work environment

41
Q

What are some physical stressors

A 
Heat/Cold
Infection
Bleeding
Pain
Fever
Disease processes
42
Q

What are the specific stressors in children?

A

Hunger
Thirst
Pain
Fear

43
Q

What are the 3 phases of the stress response?

A

Alarm (fight or flight)
Resistance stage
Exhaustion stage

44
Q

Outline some of the effects of the alarm stage

A
  • Fight or flight
  • Body responds immediately to a threat
  • Can be brief and short lived, or strong and longer lasting
  • Non essential activities are decreased (decreased blood supply and stimulation)

What physiological effects take place?

  • Body organs and systems work together to increase the activity of organs that are most necessary in fighting off danger
  • Increase in blood supply to bring them increased oxygen and glucose
45
Q

What are the examples of physiological responses of the alarm stage?

A

Pulse (Rate and strength) increase
Respiratory rate and effort (increase)
Blood pressure (increase)
Body core temperature (slight increase)
Skin (pales and cools and sweating occurs)
Blood glucose concentration (increases)
Urinary output (decreases, although bladder may relax)
Mouth (dries) and digestive system (decreases digestive activity, stomach activity increases)
Emotional state (sensation of fear, focus on stressor)

46
Q

What happens to young infants in the alarm stage?

A 
Dont usually sweat- not a useful indicator of stress
Urinary output may vary
Inability to communicate feelings
Different stressors than adults
Be familiar with vital signs for age
47
Q

Describe the physiology of the alarm stage?

A

The hypothalamus is able to respond to the chemistry and composition of the blood as it passes through: e.g. toxins, fever, dehydration
Receives nerve impulses from the conscious centres of the brain

Triggers the SNS which…
Activates the necessary organs and glands:
Heart to increase
Liver to produce glucose
Spleen to release blood
Stimulate adrenal medulla (adrenaline and noradrenaline)
Posterior pituitary secretes ADH and decreases urine output

48
Q

Describe the resistance stage

A 
CORTISOL
-Increases glucose
-Increases protein breakdown
-Blood vessels constrict
-Decrease in inflammation. 
   >Increases BP. May not be useful if no blood loss
   >Delayed wound healing
   >Increased risk of infection

ALDOSTERONE
-Increases BP
> Useful if bleeding or fluid loss has occurred or in dehydration but may be unhelpful

Human GrowthHormone
Thyroid hormones

49
Q

Describe stress in infants

A

Young infants and especially preterm and low birthweight babies have immature body systems which alters their stress response

  • Poor thermoregulation-smaller changes in environmental or body temperature cause stress
  • Poor glucose stores- more likely to become hypoglycaemic (a stressor). Less glucose in the body to use during stress causes quicker exhaustion
50
Q

Describe the exhaustion stage

A
  • If the resistance stage is not successful in combating stress, the body will move to the exhaustion stage
  • Body mechanisms and reserves have been exhausted e.g. potassium levels fall dangerously low (lost to balance out sodium which is retained) and body cells cannot function normally- glucocorticoid production may be exhausted- cells and tissues do not receive necessary support
  • Body tissues, then whole organs start to fail
  • Unless urgent intervention occurs, this stage will prove fatal
  • Management should always aim to prevent the patient reaching the exhaustion phase
  • Young infants, and children who are not in good general health, will reach the exhaustion stage sooner than older children and those previously in good health
51
Q

Describe the short-term stress response

A

Increased heart rate
Increased blood pressure
Liver converts glycogen to glucose and releases glucose into the blood
Dilation of bronchioles
Changes in blood flow patterns leading to increased alertness, decreased digestive system activity and reduced urine output
Increased metabolic rate

52
Q

Describe long-term stress responses

A 
Retention of sodium and water by kidneys
Increased blood volume and pressure
Proteins and fats converted to glucose or broken down for energy
Increased blood sugar
Suppression of immune system
53
Q

What is insulin?

A

Anabolic hormone which has a key role in glucose metabolism; has an important effect on fat and protein metabolism

54
Q

What happens to insulin after eating?

A

Insulin rises, facilitating entry of glucose into cells via glucose specific transporters (especially in muscle and adipose tissue)
Insulin stimulates glycogen synthesis in the liver and muscles

55
Q

What happens to insulin during fasting?

A

Glucose concentration and insulin secretion fall
Absence of glucose uptake in muscle and adipose tissue
Stimulation of glycogenolysis in the liver and muscles, and hepatic gluconeogenesis, from amino acids and ketones

56
Q

Describe glucose regulation

A 
The pancreas has an exocrine and endocrine function
Pancreatic islets (islets of Langerhans) are clusters of cells and this is the endocrine part of the pancreas
Pancreatic islets consist of beta cells which secrete the hormone insulin and alpha cells which secrete the hormone glucagon
57
Q

Describe the difference between insulin and glucagon

A

Insulin- decreases glucose

Glucagon- increases glucose

58
Q

Describe the release of insulin

A

Release stimulated by high blood sugars. Insulin acts on different cells, especially liver and skeletal muscle cells to promote the facilitated diffusion of glucose into the cells
Insulin speeds up the synthesis of glycogen from glucose (glucose stored as glycogen in cells)
Blood glucose levels falls as glucose diffuses out of the blood into the cells where it is stored as glycogen
Insulin release is inhibited by a low blood sugar (negative feed back)

59
Q

Describe the release of glucagon

A

Is stimulated by low blood sugars; in order to increase them. It acts on liver cells to promote breakdown of stored glycogen back into glucose
Liver releases this glucose into the blood so blood glucose level rises
Glucagon release is inhibited by high blood glucose levels (negative feedback)

60
Q

Describe insulin-dependent diabetes mellitus in children

A 
It is an autoimmune destruction of the beta cells in the islets of langerhans in the pancreas. This means it will not produce the insulin needed to break down blood sugars. Without insulin, blood glucose cannot enter cells therefore more and more builds up in the blood causing high blood sugars.
Occurs in 1 in 400/500 children and adolescents
Persistent hyperglycaemia (fasting blood glucose >7mmol/L)
Serious risk of diabetic ketoacidosis
Risk of long term complications such as retinopathy, renal failure, cardiovascular disease, neuropathy

Biosciences 2 (5 decks)

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