Endocrine

Chapter 12 in text

Hormones are important for EVERYTHING! From breakdown of glucose during exercise to initiating orgasm in humans read on to find out more…

How to use online lectures

There are lecture slides and notes to explain- similar to what I would chat about in the lecture (look below the slides!)

You can either print them off (choose to print “notes pages” rather than just the slides/ handouts)

Read through with chapter 12 of the text and use text/internet to check terms/ concepts for further information if you don’t understand

Also feel free to post a discussion question on webCT and I will get back to you ASAP

Good luck!

Endocrine GlandsEndocrine Glands

Secrete hormones into the blood Lack ducts (ductless), but discharge their substances

directly into the extracellular space around the gland Hormones then diffuse into the blood for transport

throughout the body Eg. The adrenal medulla is an endocrine gland that

secretes epinepherine and norepinepherine into the blood that targets many different tissues to cause a sympathetic response.

Exocrine GlandsExocrine Glands

Contain secretory ducts that lead directly to the specific compartment or surface that requires the hormone

Include the sweat glands and upper digestive tract glands

The nervous system controls almost all exocrine glands

Hormone Classification Hormone Classification

Peptide hormones – Composed of linked amino acids

Steroid hormones– Derived from cholesterol and amine hormones

Amine hormones – Derived from a single type of amino acid

Peptide Hormones Peptide Hormones

Range from small peptides of only three amino acids to large proteins and glycoproteins

Are water-soluble Bind to surface membrane receptors and act

through a second messenger Signal transduction:

– G-protein coupled receptors– Second messenger– A cascade of metabolic processes

Steroid HormonesSteroid Hormones

Lipid-soluble Derived from cholesterol Made only in adrenal cortex, gonads, and

placenta (in pregnancy) Include androgens (testosterone), estrogens

and progestagens

Amine Hormones Amine Hormones

Small molecules synthesized from one or two amino acids comprise the amine hormones

Include catecholamines (epinephrine and norepinephrine) - they are neurohormones

Hormone ActionsHormone Actions

Hormones– Change the synthesis rate of intracellular

proteins – Alter enzymatic activity – Modify cell membrane transport – Induce secretory activity

Patterns of Hormone SecretionPatterns of Hormone Secretion

Hormones are secreted:– On an as-needed basis– At regular intervals during a 24-hour cycle,

referred to as diurnal variation– Some secretory cycles span several weeks,

whereas others follow daily cycles

Major hormones you should know

Hormones of the PancreasHormones of the Pancreas

Insulin– Regulates glucose metabolism by facilitating glucose

uptake in all tissues 9mostly muscles and liver) except the brain in response to hyperglycemia (hyper = high)

Glucagon– Stimulates the catabolism (breakdown) of liver

glycogen to increase glucose output to prevent hypoglycemia (hypo = low)

INSULIN-

Controller of blood glucose levels

Diabetes Mellitus Diabetes Mellitus

Type 1 diabetes results from the body's failure to produce insulin.

Type 2 diabetes results from insulin resistance (a condition where the body fails to properly use insulin) combined with relative insulin deficiency

Gestational diabetes- diabetes occurring only while a woman is pregnant- afflicts about 4% of all pregnant women

Blood glucose levels

<4 mmol/L – Too low- give jelly beans/ juice etc

4-6 mmol/L- Average 12 mmol/L – Too high, but doesn’t require

insulin yet 15 mmol/L- Too high- requires insulin

Considerations for exercise:

Exercise 60-90 minutes after insulin injection Watch for signs of hypoglycaemia (lethargy,

slurring words etc) Keep hydrated Keep some glucose on hand- jelly beans or

fruit juice

Benefits of exercise for diabetics

Glycaemic control- acute decrease in blood glucose levels and increased insulin sensitivity of peripheral tissues (meaning that there is a stabilisation of blood glucose levels). As these effects may last for a few hours to a few days (av = 48 hours) there is a stabilisation of blood glucose levels

Pituitary HormonesPituitary Hormones

Anterior lobe– Growth hormone (GH)– Prolactin (PRL)– Tropic hormones

ACTH- corticotropin FSH- Follicle stimulating

hormone LH- luteinizing hormone

Posterior lobe– Oxytocin- “cuddle

hormone” childbirth and orgasm (not in that order!)

– Antidiuretic hormone ADH or vasopressin

Growth Hormone (GH)Growth Hormone (GH)

Promotes cell division and proliferation It increases calcium retention, and strengthens and

increases the mineralization of bone. It increases muscle mass through the creation of new

muscle cells (which differs from hypertrophy) It promotes lipolysis, which results in the reduction of

adipose tissue (body fat). It increases protein synthesis and stimulates the

growth of all internal organs excluding the brain.

Exercise, GH, and Tissue Synthesis Exercise, GH, and Tissue Synthesis

GH secretion increases a few minutes after exercise begins

Increasing exercise intensity increases GH production and secretion

GH promotes its anabolic, tissue-building effects (mediated via somatomedins) on diverse tissue including bone and skeletal muscle

Too much GH!!

Thyroid hormones

Major endocrine gland Secretes hormone that is essential to proper

growth, development and differentiation of all cells of the human body

Failure to secrete thyroid hormones = hypothyroidism. Too much thyroid hormone = hyperthyroidism

Hypothyroidism

Mostly due to lack of thyroid gland.

- Also linked to iodine deficiency (note to self- buy iodised salt!)

Goiter

Hormones of the Adrenal MedullaHormones of the Adrenal Medulla

Catecholamines– Neural outflow from the hypothalamus directly

influences adrenal medulla secretions Epinephrine (80%) and norepinephrine (20%)

– Increase heart rate, contractility, and blood pressure– Rate of secretion is strongly influenced by exercise

intensity

Hormones of the Adrenal CortexHormones of the Adrenal Cortex

Mineralocorticoids – Aldosterone regulates sodium reabsorption in the

kidneys’ distal tubules Glucocorticoids

– Cortisol regulates blood glucose concentrations via its permissive interactions with glucagon and catecholamines

Androgens– Dehydroepiandrosterone (DHEA)

Hormonal responses to exercise