Chp 2 Hormones & the body - HB

How is coordination Of the body structures achieved?

Through Activities of the Endocrine & Nervous system

How does the nervous system exert control?

By transmission of nerve impulses to and from various tissues

How does the Endocrine system work?

Influences the activity of cells By The release of hormones

What is homeostasis?

Maintaining a stable internal state/environment

• Endocrine mainly focuses on this

What is a stimulus?

Any changes in the environment that you can respond to

What does secrete mean?

Produced & released

What does saturation mean (in terms of hormones)

When receptors close and doesn’t allow hormones to enter because they are already occupied by another hormone.

What are the two types of glands in the body?

EXOcrine (ducted glands)

ENDOcrine (ductless glands)

Where do Exocrine glands secrete?

Secretary into duct that carries secretion to body surface or to one of body cavities.

E.g: Sweat glands, Salivary glands, Mucous glands

Where do Endocrine glands secrete?

Secrete into extracellular fluid that surrounds cells that make up gland.

→ Secretion usually passes into capillaries to be transported by blood.

Eg: pituitary, hypothalamus, pancreas, thyroid, ovaries, testes

What are hormones?

Chemicals secreted by endocrine glands

Transported in bloodstream

NOT ENZYMES

• can be steroids, proteins or amines

What are paracrines?

Aka: Local hormones

Secreted by ALL cells in a PARTICULAR TISSUE

Move through extracellular fluid

How do hormones change the functionIng of the cell?

By changing the:

• type

• Activity

• Quantity

Of proteins produced

How do hormones change the activity of enzymes?

By:

• changing activity of enzymes

• Changing their concentration

What can hormones do?

• activate certain genes in nucleus so particular enzyme or structural protein produced

• Change shape or structure of enzyme so its turned ‘on’ or ‘off’

• Change rate of production o enzyme or structural protein by changing rate of transcription or translation during protein production.

what cells can hormones influence?

Cells that have correct receptor for hormone.

• all cells of the odd

• Particular group of cells Target cells

• Particulars group of organs Target organs

What are the 3 types of proteins?

• hormones

• Transporter

• Receptor

How do receptor proteins work?

they are specific

→ each type of receptor will bind with only one specific molecule

Variation in sensitivities of cells to hormones & other substances bus different cells have different types & number of receptor proteins

How can saturation occur?

Limited number of proteins in membrane of each cell

When each receptor id bound to a molecule, there can be no further increase in rate of cell’s activity

→ Saturation can occur

How can hormones travel?

Once released into bloodstream:

→ bind to transport protein, enabling them to travel in bloodstream

→ when reach target cell, hormones seperate from transport protein

→ bind to receptor protein

Types of hormones (hint 3)

1. Steroid

2. Protein

3. Amine

What are steroid hormones?

1. Derived from cholesterol

2. Lipophilic (lipid soluble) & hydrophobic

→ can freely diffuse through plasma membrane of cell (phospholipid bilayer)

3. 2 classes: Sex hormone & Corticosteroids

What are sex hormones & where are they produced?

In the gonads (testes & ovaries)

Produce: progesterone, oestrogen, testosterone

What are corticosteroids & where are they produced?

Produced by: Adrenal glands

Produce: Cortisol, aldosterone

Mode of action: Steroid hormones

1. Enter target cells & bind to receptors in in Cytoplasm, Nucleus, mitochondria or other organelles. Forms active hormone-receptor complex

2. Hormone-receptor complex activates genes controlling the formation of particular proteins

3. Hormone-receptor complex binds to promotor section of a certain gene

→ stimulation or inhibiting transcription

→ and therefore protein synthesis

Slow response but long-lasting effect

What are Protein & Amine hormones?

Formed from changes of Amino acids (same way as other proteins)

Hydrophilic & LipophobiC

→ cannot freely cross plasma membrane

E.g: Insulin, Prolactin

Mode of action: Protein & Amine hormones

1. Attac h to receptor proteins in membrane of target cell

2. Receptors are linked to secondary messenger systems on other side of membrane

3. Once hormone combines with receptor, it causes secondary messenger substances to diffuse through cell & activate particular enzymes

Quick response, effect is short lasting

What is enzyme amplification?

Activation of thousands of molecules

1. Hormone triggers cascading effect where number of reacting molecules involved is increased hundreds/thousands of times for each step along metabolic pathway

→ very small stimulus, very large effect

What is hormone clearance?

Once hormone produced required effect, must be turned off

Done by breaking down hormone molecules;es.

Where are hormones broken down & excreted?

Some in target cells, but most in Liver & Kidneys

Degraded hormones then excreted in bile or urine

How does the body control hormone secretions?

Hormones mist be closely regulated

→ oversecretion or undersecretion = abnormal body function

Control by: Negative feedback systems

→ response produced by secretion of hormone is opposite of stimulus that caused secretion

What is the hypothalamus (purpose & location)

Location: base of brain, below thalamus, above pituitary glands

Purpose: serves as connection between two systems

Regulates basic functions of body (body temp, water balance, heart rate)

Increasing & decreasing secretions of other glands

Where are the functions of the hypothalamus carried out?

Pituitary gland

What does the hypothalamus secrete?

Releasing factors - stimulate the secretion of hormone or, inhibiting factor -slow down secretion of hormone

Other hormones produced by hypothalami’s pass along nerve fibres to posterior lobe of pituitary glands where released

How do the factors travel?

Through blood vessels to anterior lobe of pituitary gland, affecting secretion of its hormones

Where is the pituitary gland located?

In smal depression in skull bone, beneath hypothalamus

What is the structure of the pituitary gland?

Connected to hypothalami’s by thin stalk called infundibulum

~13mm diameter

Consists of anterior lobe & posterior lobe (each have seperate functions)

How is the anterior lobe connected

Connected to hypothalamus by complex network of blood vessel

How is the posterior lobe connected & what does it do?

Joined to hypothalamus by nerve fibres that come from nerve cell bodies in hypothalamus & pass through infundibulum

Not a true gland bcs doesn’t secrete hormones

→ stores & releases them

What does the anterior lobe secrete?

Number of hormones

• secretions controlled by releasing & inhibiting factors secreted by hypothalamus

Releases:

• Gonadotropins, FSH, LH, Growth hormone, Thyroid-stimulating hormone, Adrenocorticotropic hormone, Prolactin

What does Gonadotropins do?

Affect the gonads (overlies & testes)

What does Follicle-stimulating hormone do? (FSH)

Stimulated development of follicles in ovary & production & maturation of sperm in testes

What does Lutenising hormone (LH) do?

Works with FSH to bring about ovulation & form corpus luteum after ovulation

Stimulates interstitial cells in testes to secrete male sex hormone

What does growth hormone do? (GH)

Aka somatropin

Stimulates body growth (specifically, skeleton)

Increases rate which amino acids are taken up by cells & built into proteins

Secreted throughout life, helps maintain size of organs one maturity reached

What does Thyroid-stimulating hormone do? (TSH)

Aka thyrotropin

Stimulates production & release of hormones from thyroid gland

What does adrenocorticotropic hormone (ACTH) do?

Aka adrenocorticotropin

Controls production & release of some hormones from cortex of adrenal glands

What does Prolactin do? (PRL)

Works with other hormones to initiate & maintain milk production

What does the posterior lobe secrete?

NOT MADE IN POSTERIOR LOBE!!! ONLY STORES & RELEASES

• Oxytocin

• Antidiuretic hormone

What does oxytocin do? (OT)

Stimulates contractions of muscles of uterus

Released in large quantities during labour

Stimulates contraction of cells in mammary glands

→ resulting in release of milk during breastfeeding

What does Antidiuretic hormone do?(ADH)

Aka vasopressin

Causes kidneys to remove water from urine forming

Water returned to bloodstream

-ADH helps retain fluid within body

@ high concentrations can cause constriction of small arteries (arterioles)

Where is oxytocin & ADH made?

In special nerve cells in hypothalamus

How do the hormones reach the posterior lobe?

Special nerve cells have long extensions that pass through infundibulum to posterior lobe

Hormones move down extensions and stored, ready for release into bloodstream

How is the release of hormones triggered?

By nerve impulses initiated in hypothalamus & conducted along cell extensions

Where is the pineal gland & what does it do?

Found deep inside brain

Secretes melatonin (involved in sleep pattern regulation)

→ production stimulated by darkness & inhibited by light

Where is the thyroid gland & it’s structure?

Located in neck below larynx

2 lobes that life on either side of trachea

→ joined by narrow piece of tissue tat lies across front of trachea

What hormones are the secreted by the thyroid gland?

Follicular cells secrete: Thyroxine (T4 tetraiodothyronine) & T3 (triiodothyronine)

→ made from iodine & amino acids, continuously manufactured

What is the function of Thyroxine?

Controls body metabolism by regulating reactions in which complex molecules are broken down to release energy.

Also controls other reactions where complex molecules are synthesised from simpler ones

What is the overall effect of thyroxine?

Bring about released of energy

→ some energy released as heat to maintain body temp

What does the thyroid gland also release?

Calcitonin by C-cells

What is the role of calcitonin?

Regulates levels of calcium & phosphate

How does calcitonin regulate calcium?

When concentration of calcium in blood increases, → thyroid gland releases calcitonin,

→ which reduces reabsorption of calcium

→ by kidneys & the break down of bone.

How does calcitonin regulate phosphate?

If concentration of phosphate in blood becomes too high

→ calcitonin acts to move phosphate into bone

→ reduces its reabsorption by kidneys

Where is the parathyroid gland and what is its function?

Located: rear surface of lobes of thyroid gland

Purpose: Secrete parathyroid hormone (PTH or Parathormone)

→ increases calcium levels in blood & phosphate excretion in urine

Where is the thymus & what is its function?

Located: in chest above heart, behind sternum

Purpose: secretes group of hormones called thymosins

→ influence maturation of disease-fighting cells

→ T-lymphocytes

What are the 2 adrenal glands?

1. Inner adrenal medulla

2. Outer adrenal cortex

→ each adrenal gland is 2 seperate endocrine glands

What hormones are produced by the Adrenal Medulla?

Adrenaline & Noradrenaline

What is the function of adrenaline?

Aka epinephrine

helps to prepare body for reaction to threatening situations

What is the function of Noradrenaline?

Aka norepinephrine

Increase rate & force of heartbeat

What hormones does the Adrenal cortex produce?

Over 20 different hormones, known collectively as:

Corticosteroids

→ 2 main are: adolsterone & cortisol

What is the function of aldosterone?

Acts on kidney to reduce amount of sodium & increases amount of potassium in urine

A what is the function of cortisol?

With related hormones

→ promotes normal metabolism, helping body to withstand stress & to repair damaged tissues

What role does the pancrease play?

Both an exocrine and endocrine gland

What does the exocrine part of the pancreas do?

secretes digestive enzymes into small intestine through pancreatic duct

What does the endocrine part of the pancreas do?

ADE up of listers of special cells called islets of Langerhans (pan creative islets)

→ cells secrete 2 hormones: Insulin & Glucagon

What is the function of insulin?

Secreted by beta cells of pancreatic islets

→ reduces amount of glucose in blood

How does insulin work?

Promotes uptake of glucose from blood by cells of body

In Liver: insulin causes conversion of glucose → glycogen & fat

In Skeletal muscle: causes formation of glycogen from glucose

In Fat storage tissues: causes glucose to be converted into fat

How is insulin regulated?

Determined by amount of glucose in blood

→ controlled through negative feedback system

What is the function of glucagon?

Secreted by alpha cells of pancreatic islets

Works to increase blood glucose level

→ by promoting breakdown of glycogen to glucose in Oliver

Also stimulates breakdown of far in liver & fat storage tissues

What is androgen?

Category of hormones produced by the gonads

E.g: Testosterone, Oestrogen & Progesterone

What is the function of testosterone?

Aka male sex hormones

Responsible for development & maintenance of make sex characteristics

Produced by testes

What is the function of oestrogen and progesterone?

Produced by ovaries

Stimulate development & maintenance of female sex characteristics

Tgt with gonadotropic hormones of pituitary

→ regulates menstrual cycle & involved in changes that occur during pregnancy

What does the stomach & small notes tine secrete?

Hormones that coordinate the exocrine glands o digestive system,

What do the kidney’s secrete?

Enthropoirtin (EPO)

→ hormones that stimulates production of red blood cells by bone marrow

What does the heart secrete?

Hormone that helps reduce blood pressure

What does the placenta secrete?

Number of hormones during pregnancy that helps maintain pregnancy, stimulate development of foetus & stimulate mother’s mammary glands