the endocrine system

what does it consist of

a secretory organ (gland)

small quantities of a chemical messenger (hormone)

target cell or organ

what is the main function of the endocrine system

maintain homeostasis

what do glands do

produce and secrete hormones

function of endocrine system

controls body activities by releasing mediators called hormones

functions of the nervous system

controls body actions through nerve impulses

nervous system vs endocrine system

nervous endocrine

neurotransmitters vs hormones

act close to release site vs act far from release site

muscles,glands,neurons vs cells throughout body

onset of action ms onset of action seconds,hours,days

duration brief duration longer - sec to hours

what is intercelluar communication

• Is the transfer of information from one cell to another. Cells signal each other by the release of a substance from one cell that is taken up by another cell

• Parts of the nervous system stimulate or inhibit the release of hormones

• Hormones may promote or inhibit the generation of nerve impulses

what are the types of intercellular communication

• Paracrine - cells talk to neighbouring cells

• Neurotransmitters

• Hormones

what is a hormone

• Chemical messenger in the endocrine system

• Produced and secreted in the body and control and regulate the activity of certain cells or organs

what do hormones do

Hormones regulate extra-cellular fluid, metabolism, biological clock, growth and development, tissue formation, reproduction, sleep and mood

factors determining level of hormone activation/action

1. Hormone

2. Number of receptors in target cell

3. Sensitivity of the receptor in the target tissue

how do hormones act

bind to receptors in target cells

what are the 2 types of hormones

steroid and non steroid

what are steroid hormones

• Chemical structure similar to cholesterol (most derived from cholesterol)

• Soluble in lipids

• Diffuse easily through cell membranes

• Receptors in cytosol and nucleus

what are non steroid hormones

• Can be divided into

  • Peptide or protein hormones

  • Amino acid hormones

• Are not liposoluble

  • Don’t diffuse through the plasma membrane

what is steroid hormone action

direct action

1. Steroid hormones can diffuse through the cell membrane

2. Binding to specific receptors into the cell (cytosol or nucleus of the cell)

3. Hormone-receptor binds to promoter regions of responsive genes and stimulate (some inhibit) gene transcription

 

what is non steroid hormone action

indirect action

1. Hormone (first messenger) binds to receptor on the cell memebrane

2. Activation of enzyme or other protein

3. Formation of second messenger

4. Second messenger promotes a series of reactions leading to cellular changes

examples of steroid hormones

• Cortisol

• Aldosterone

• Testosterone

• Progesterone

• Oestradiol

what are female sex hormones

Primary function is development of secondary sexual characteristics and are essential for endometrium thickening and woman's reproductive health

 

Oestrogens effect

• Maintenance of bone mineral density

• Metabolic functions e.g. fat oxidation

• Cardiovascular protection

examples of non steroid hormones

• Thyroxin (T4)

• Triiodothyronine (T3)

• Epinephrine (adrenaline)

• Norepinephrine (noradrenaline)

what is hormone secretion controlled by

feedback loops

what is negative feedback

Negative feedback is a way to counteract a change in the body by releasing hormones e.g. insulin response to blood glucose

roles of the hypothalamus

• Releasing hormones

• Regulating body temp

• Maintaining daily physiological cycles

• Controlling appetite

• Managing sexual behaviour

• Regulating emotional responses

how do hormones of the hypothalamus work

When it recieves a signal from the nervous system, the hypothalamus secretes substances known as neurohormones that start and stop the secretction of pituitary hormones

examples of hormones released by the hypothalamus

• Anti-diuretic hormone (ADH)

  • Body H2O regulation

• Oxytocin

  • Various - childbirth, social bond and reproduction

• Gonadotropin-releasing hormone (GnRH)

  • Release of LH and FSH

• Growth hormone releasing hormone and growth hormone inhibiting hormone

  • Controle release of GH

• Corticotropin releasing hormone

  • Release od the adrenocorticotropic horm

• Thyrotropin releasing hormone

  • Thyroid releasing hormone and prolactin

what is the pituitary gland

• Main function is to secrete hormones into the bloodstream

• Hormones affect other organs and glands

• Called master gland

how can pituitary gland be split up

anterior lobe and posterior lobe

what is the anterior lobe

made up of several types of cells that produce and secrete different types of hormones

what is the posterior lobe

secretes hormones but doesn’t produce them - hormones produced by hypothalamus are stored in posterior lobe until released

what is the thyroid gland

endocrine gland in your neck

what 2 hormones are produced by thyroid gland

T4-thyroxin

T3-triiodothyronine

what is T4

biologically inactive - has no effect

converted to T3 by the liver

what is T3

 acts in all cells speeding up the conversion of food to energy and drive metabolic rate

what is the adrenal gland

• Endocrine glands that produce variety hormones

• Each gland has an outer cortex which produces steroid hormones and an inner medulla

function of the adrenal gland

• Key role in metabolism, immune function and homeostasis

types of endocrine deficiency/disease

addisons disease

cushins syndrome

type 1 diabetes

what is addisons disease

• adrenal insufficiency which is a long-term endocrine disorder where adrenal glands don't produce enough steroid hormones

  • Low blood pressure

  • Weakness

  • Weight loss

  • Caused by immune system response attacking glands or cancers

what is cushins syndrome

• caused from too much cortisol

  • Consequence of taking steroid medicine

  • Increased fat on chest and abdomen but slim arms and legs

  • Thin skin

what is type 1 diabetes

• Affects how body regulates blood glucose levels

• Insulin helps reduce the levels of blood glucose and glucagon helps increase levels

• Type 1 caused by body not producing enough insulin