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Human Biology ATAR > Chemical messengers > Flashcards

Chemical messengers Flashcards

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1
Q

What is the endocrine system?

A

Influences the activity of cells by the release of chemical messengers known as hormones

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2
Q

What is homeostastis

A

Maintaining a stable internal enviroment

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3
Q

What are exocrine glands?

A

Secrete into a duct that carries the secretion to the body surface or one of the body cavities EG. Sweat glands, mucous glands, salivary glands and the glands of the alimentary canal

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4
Q

What are endocrine glands?

A

Secrete hormones into the extracellular fluid that surrounds the cells that make up the gland. They are then usually passed into the capillaries which are then transported by blood.
Can also be called ductless glands

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5
Q

What are the major endocrine glands?

A
  • Hypothalamus
  • Pituitary
  • Pineal
  • Thyroid
  • Pancreas
  • Thymus
  • Parathyroid
  • Adrenal glands
  • Ovaries in females
  • Testes in males
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6
Q

What are hormones?

A

Any secretion from an endocrine gland

  • May be proteins, steroids or amines
  • Transported by blood
  • May affect all the cells of the body, or only a particular group of cells (target cells) or particular organs (target organs)
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7
Q

What are paracrine hormones?

A
  • May be released in order for cells to communicate within other cells in the same tissue
  • Are secreted by all cells in a tissue
  • Move through the extracellular fluid
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8
Q

Protein and amine hormones

A

Attach to receptor proteins in the membrane of the target cell
This causes a secondary messenger substance to diffuse through the cell and activate a particular enzyme.

EG. The hormone insulin binds to a receptor protein and this leads to increased glucose absorption by the cell. However, because there are only a limited number of specific receptor proteins, once each insulin receptor in the cell membrane is bound to insulin, the rate of glucose uptake cannot be increased further.

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9
Q

Steroid hormones

A

Enter a target cell and combine with a receptor protein inside the cell.
The receptor may be on the mitochondria, or on other organelles or in the nucleus

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10
Q

What is the hormone-receptor complex?

A

Activates the genes controlling the formation of particular proteins

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11
Q

List three activities that hormones carry out?

A
  • Activate certain genes in the nucleus so that a particular enzyme or structural protein is produced
  • Change the shape (active site) or structure of an enzyme so that it is turned ‘off’ or ‘on’
  • Change the rate of production of an enzyme or structural protein by changing the rate of transcription or translation
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12
Q

Enzyme amplification

A

Means that one molecule does not cause the manufacture or activation of just one enzyme molecule, but thousands of enzyme molecules

  • Hormone triggers a cascading effect
  • The number of reacting molecules involved increased hundreds or thousands of times for each step along the metabolic pathway
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13
Q

When and where are hormones broken down?

A

Hormones are broken down after producing the desired effect

  • Some hormones are broken down by the target cell
  • Most are broken down in the liver and kidneys
  • Degraded hormones are then excreted either in bile or urine
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14
Q

The hypothalamus

A
  • Located at the base of the brain
  • Regulates functions such as body temperature, water balance and heart rate
  • Many of these functions are carried out through the pituitary
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15
Q

What joins the hypothalamus and the pituitary?

A

A stalk called the infundibulum

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16
Q

The pituitary

A
  • Lies just under the hypothalamus

- Consists of an anterior lobe and a posterior lobe

17
Q

The anterior lobe of the pituitary

A

It has no nerves connecting to the hypothalamus, but instead is connected by a complex network of blood vessels.

18
Q

How are the secretions of the anterior pituitary controlled?

A

Secretions are controlled by releasing and inhibiting factors secreted by the hypothalamus
- These factors are hormones in themselves
o Secreted into extracellular fluid around the cells of the hypothalamus
o Carried by the blood to the anterior lobe

19
Q

What are the main hormones secreted by the anterior lobe of the pituitary?

A
  • gonadotrophins
  • growth hormone
  • thyroid stimulating hormone
  • Adrenocorticotropic hormone
  • prolactin
20
Q

Gonadotrophins

A

Are hormones that affect the gonads
- Follicle stimulating hormone (FSH)
o In females: it stimulates development of the follicle that contains eggs
o In males: it stimulates the production and maturation of sperm in the testes
- Luteinising hormone (LH)
o In females: it brings about ovulation, leading to the development of the corpus luteum
o In males: it stimulates the interstitial cells in the testes to secrete male sex hormones

21
Q

Growth hormone (GH)

A
  • Stimulates body growth, particularly growth of the skeleton
  • Increases the rate at which amino acids are taken up by the cell and built into proteins
  • Secreted throughout life, helping to maintain the size of organs once maturity is reached
22
Q

Thyroid-stimulating hormone

A

Stimulates production and release of hormones from the thyroid gland

23
Q

Adrenocorticotropic hormone (ACTH)

A

Controls production and release of some of the hormones from the cortex of the adrenal glands

24
Q

Prolactin

A

Works with other hormones to initiate and maintain milk secretion in females

25
Q

Posterior lobe of the pituitary

A

Releases oxytocin and anti-diuretic hormone
(neither is manufactured in the posterior lobe)

Both hormones are produced in special nerve cells in the hypothalamus of the brain

  • These cells have long extensions that pass through the infundibulum to the posterior lobe
  • These hormones move down the extensions and are stored ready for the release into the blood stream

The release of hormones is triggered by the nerve impulses which are initiated by the hypothalamus

26
Q

Oxytocin

A
  • Stimulates contraction of the muscles of the uterus
  • Released in large quantities during labour
  • Also stimulates the contraction of cells in the mammary glands, resulting in release of milk during breastfeeding
27
Q

Anti-diuretic hormone

A
  • Causes the kidneys to remove water from urine that is forming
  • Water is returned to blood stream
  • Helps to retain fluid within the body
  • In high concentrations- cause constriction of small arteries
28
Q

Pineal gland

A

Found deep inside the brain, about the size of a pea in children
- After puberty, it gradually decreases in size

Secretes Melatonin

  • Involved in the regulation of sleep patterns
  • The production of melatonin is stimulated by darkness and inhibited by light
29
Q

The thyroid gland

A

Located in the neck and consists of two lobes that lie on either side of the trachea. Joined by a piece of tissue in front of the trachea

Main hormone = thyroxine

  • Made from iodine and amino acid
  • Controls body metabolism
  • Regulates reactions in which complex molecules are broken down to release energy, other reactions in which complex molecules are synthesised from simpler ones
  • Due to this release of energy, which is the overall effect of thyroxine, some energy is released in the form of heat, maintaining body temperature

Secreted in response to TSH from the anterior lobe of the pituitary

30
Q

Parathyroid glands

A

There are usually four parathyroid glands (some people have more)

  • Size of a small pea
  • Embedded in the rear surface of the thyroid glands

Secrete parathyroid hormone (PTH) which controls calcium and phosphate levels in the blood

31
Q

The thymus

A

Located in the chest, just above the heart and behind the sternum

It is largest in infants and children, and begins to shrink after puberty

Secretes a group of hormones called thymosins
- Influence the maturation of disease-fighting cells called t-lymphocytes

32
Q

The adrenal glands

A

There are two adrenal glands, one on top of each kidney

Each have an outer adrenal cortex and an inner adrenal medulla

33
Q

The adrenal medulla

A
  • Produces adrenaline: helping to prepare the body for a reaction to a threatening situation
  • Noradrenaline: increasing the rate and force of the heart beat
34
Q

The adrenal cortex

A
  • Produces hormones known as corticosteroids
  • Aldosterone: act on the kidney to reduce the amount of sodium and increase the amount of potassium in the urine
  • Cortisol: promotes normal metabolism, helping the body to withstand stress and also helps with the repair of damaged tissues
35
Q

The pancreas

A

Both an exocrine and endocrine gland

The exocrine gland
- Secretes digestive enzyme into the small intestine though the pancreatic duct

The endocrine gland

  • Cluster of islet of Langerhans cells within the pancreas
  • Secrete insulin and glucagon
36
Q

Insulin

A
  • Reduces the amount of glucose in the blood (blood sugar levels)
  • Promotes the uptake of glucose from the blood by the cells of the body
    In liver
  • Causes the conversion of glucose to glycogen and fat
    In skeletal muscles
  • Causes the formation of glycogen from glucose
    In fat storage
  • Causes glucose to be converted to fat

The level of insulin secreted is determined by the amount of sugar in the blood and is controlled though the negative feedback system

37
Q

Glucagon

A
  • Works to increase blood sugar levels
  • Promotes the breakdown of glycogen to glucose
  • Also stimulates the breakdown of fat in the liver and in the fat storage tissues

Insulin and glucagon maintain a constant level of glucose in the blood

38
Q

The gonads

A

Androgens

  • Male sex hormone produced by the testes
  • Responsible for the development and maintenance of the female

Oestrogen and progesterone

  • Female sex hormones
  • Responsible for the development and maintenance of the female sexual characteristics
  • With the gonadotropic hormones of the pituitary, these hormones regulate the menstrual cycle
  • Are involved in changes that occur during pregnancy
39
Q

Other endocrine tissues

A

The stomach and the small intestine: secrete hormones that coordinate the exocrine glands of the digestive system

Kidneys: secrete erythropoietin (EPO), stimulating the production of red blood cells by the bone marrow

The heart: secretes hormones that help to reduce blood pressure

The placenta: secretes hormones to maintain pregnancy, stimulates foetal development, as well as the stimulation of mammary glands

Human Biology ATAR (13 decks)

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