ENDOCRINE SYSTEM

CTLI Training: 12,13 July 2011

H.C.Adonis

HOMEOSTASISLIVER SKIN

PANCREAS LUNGS

KIDNEYS

glucoseAmino acidsIns

ulin &

glu

cago

n

ureum Excess water, salts, ions

oxygen

carbondioxideureum

Excess

water,salts,h

eat

HOMEOSTASIS: Main ideasMaintenance of constant internal environment in

the body/keeping conditions in tissue fluid constant

WHY?Cells dependant on tissue fluid to function

optimallyHOW?Various systems that help in maintaining tissue

fluid/internal environment constant i.e. nervous system, excretory system, respiratory system, ENDOCRINE SYSTEM.

Various systems need to be coordinated in order for body to function as a unit.

HOW ARE THESE SYSTEMS COORDINATED?

CHEMICAL COORDINATION

: Endocrine System

Communication through the use of

hormones: results in slower responses

NERVOUS COORDINATION:Nervous system

Communication takes place via

neurons: results in quick

responses

HOW DOES CHEMICAL COORDINATION TAKE PLACE?

RECEPTORS: detect

stimuli/change

EFFECTORS (glands): react on

stimuli

HOMEOSTATIC CONTROL CENTRE:

THE BRAIN(hypothalamus) Nerve

impulses/Hormones in bloodstream

Nerve impulses

stimuli responsesFeedback

CHEMICAL vs NERVOUS COORDINATION

CHEMICAL COORDINATIONCo-ordinates different

systems in the body to work together

Involves hormones transported in the bloodstream in small quantities

Has general and local effects on the body

Is slower actingHas long-lasting effects

NERVOUS COORDINATIONCo-ordinates different parts

of the body to work together

Involves isensations that are transported via neurons in the form of impulses

Has specific targets/effectors

Is very fast actingHas more short-term effects

HUMAN ENDOCRINE SYSTEM• Ductless glands• Release hormones

directly into bloodstream or lymph.

Endocrine

glands• Release secretions in

ducts to be carried to body cavity or outside of body i.e. saliva, tears etc.

Exocrine glands

ENDOCRINE SYSTEM Endocrine system co-ordinates the body’s organs to help maintain

homeostasis Based on the production of chemical messengers called

HORMONES. Hormones control body processes that require several organs of

the body to interact for a combined effect. Are chemical "messengers“, secreted by glands. Moves very slowly. Most hormones are proteins and some are steroids. Hormones have specific target organs Regulatory effect – stimulate OR inhibit Do not function in isolation – integrated with other hormones

Functions controlled by hormones include: activities of entire organs growth and development reproduction sexual characteristics usage and storage of energy regulate water content (osmoregulation) ionic (salt) regulation regulation of blood glucose level

ENDOCRINE GLANDS: position + function

IMPORTANT!

POSITION OF GLANDS

HORMONES SECRETED

FUNCTION / EFFECT OF HORMONES

ENDOCRINE GLANDS: locationHypophysis / pituitary

gland

Thyroid gland

Pancreas

Adrenal glands

Ovaries

Testes

ENDOCRINE GLANDS: location & function

Pituitary gland/hypophysis

Located at base of brain, attached to hypothalamus

Nerve fibres from hypothalamus runs into posterior lobe

Known as “master gland”

Consist of anterior (adenohypophysis) and posterior lobe (neurohypophysis)

Anterior lobe releases:•TSH (Thyroid-stimulating hormone)•Growth hormone (STH)•FSH (Follicle-stimulating hormone)•LH (Luteinising hormone)•Prolactin

Posterior lobe releases:•ADH (Anti-diuretic hormone)•Oxytocin

HYPOPHYSIS / PITUITARY GLAND

HYPOPHYSIS HORMONES: Anterior lobe

TSH• Stimulates the thyroid to

secrete the hormone thyroxin

GROWTH HORMONE(STH)

• Promotes growth of skeleton and muscles by stimulating synthesis of proteins

FSH• Stimulates development

of primary follicles in ovaries into Graafian follicles

LH • Stimulates ovulation

PROLACTIN• Stimulates the mammary

glands to produce milk after the birth of a baby

HYPOPHYSIS HORMONES: Posterior lobe

ADH (Anti-diuretic

hormone)

• Controls re-absorption of water into blood from renal tubules

OXITOCIN

• Cause muscle contractions in uterus during birth

• Triggers milk release during breastfeeding

ENDOCRINE GLANDS: location & functionThyroid: consist of two lobes on either side of trachea, just below larynx

Produces and secretes hormone thyroxin

The element iodine, essential for production of

thyroxin

Shortage could result in enlarged thyroid / goitre

THYROID GLAND

Functions of thyroxineIncreases basal metabolic rate

(amount of energy the body needs to function when body is at rest)

Increases breathing rate and heart rate

Development and functioning of nervous system

Normal growth and development of important organs

Thyroid DisordersOver secretion:Hyperthyroidis

mm

• Increased metabolic rate• Weight loss• Increased heart rate,

respiration rate and blood pressure

• Increased irritabilityUnder secretion:Hypothyroidism

• Causes very low metabolism• In children: cretinism• In adults: myxoedema

Cretinism • Abnormal growth• Mental retardation• Do not reach sexual maturity

Myxoedema

• Mental decline, physical lethargy

• Thickening of skin, increase in body mass

THYROID DISORDERS

HYPERTHYROIDISM HYPOTHYROIDISM

HOMEOSTATIC CONTROL

THYROID HYPOPHYSIS

More TSH

less TSH

Less thyroxin

More thyroxin

NEGATIVE FEEDBACK SYSTEM

GROWTH DISORDERS

HYPOSECRETION HYPERSECRETIONGigantism &

AcromegalyDwarfism

ENDOCRINE GLANDS: location & function

PancreasTwo types of cells: • Pancreatic cells• Islets of Langerhans (small groups of cells)

Pancreatic cells have exocrine function and secrete pancreatic juice into pancreatic duct which leads to duodenum

Islets of Langerhans have endocrine function and secretes 2 hormones directly into bloodstream i.e. glucagon and insulin

Alpha cells secrete glucagon and beta cells produce insulin

Insulin and glucagon responsible for homeostatic control of blood glucose levels through negative feedback system

PANCREAS

PANCREAS

INSULIN & GLUCAGON: Homeostatic control

INSULIN: Beta cells

• Stimulates absorption of glucose to body cells

• Stimulates conversion of glucose to glycogen in liver and muscles

• Inhibits conversion of glycogen to glucose

GLUCAGON:

Alpha cells

• Stimulates conversion of glycogen to glucose in the liver

• Inhibits conversion of glucose to glycogen

LOW BLOOD GLUCOSE1.

2. glucagon

Blood glucose levels return to normal , feedback to

hypothalamus

Low blood glucose(stimulus)

3.

4.

HIGH BLOOD GLUCOSEHigh blood glucose(stimulus)

insulin

Blood glucose returns to normal, feedback to hypothalamus

1.

2. 3.

4.

HOMEOSTATIC CONTROL: BLOOD GLUCOSE

DIABETES mellitus: Type 1Dysfunction of beta cells, little or no insulin is

produced - can cause elevation of glucose level in blood.

The excess glucose is now removed from the body through urine.

Excess glucose is also removed throughsweating.

SYMPTOMS:Frequent urinationIncreased hungerInexplicable weight lossRepeated infectionsImpaired visionExhaustion and dizziness Wounds that heal slowly

Treatment and management

Daily insulin injectionA specially adapted dietRegular testing of blood sugar

levels

Type 2 diabetesCharacterised by insulin resistanceLife style disease

CAUSES:Overweight and obesityInactivityAgeTREATMENT AND MANAGEMENT

Maintain normal body mass through balanced dietRegular exerciseOral medication or insulin

ENDOCRINE GLANDS: location & function

Adrenal glands

Located at top of each kidney ; consist of outer cortex and inner medulla

Adrenal cortex produces hormone aldosterone.

Adrenal medulla produces adrenalin.

ADRENAL GLANDS

Effects of Adrenalin & Aldosterone:ADRENALIN: Known as “fight or flight” hormone Increases heart rate - more blood with oxygen and

glucose to muscles Increases blood pressure due to vasoconstriction of

vessels in skin- more blood to muscles ,heart and brain Increases conversion of glycogen to glucose –

increase glucose levels in blood which releases energy Increase rate and depth of respiration – more oxygen

absorbed in blood Increase muscle tone – muscles can react faster Pupils dilate – allow more light into eye for improved

vision Increase sweat production – cool body during activityALDOSTERONE:Steroid hormone that regulates ionic balance of tissue fluid

ENDOCRINE GLANDS: location & functionGonades: testes and ovaries

Testes located outside body in scrotum

Interstitial cells (Leydig cells) produces hormone testosterone

Ovaries located in abdominal cavity, on either side of uterus

Graafian follicles produce hormone oestrogen

Corpus luteum produces hormone progesterone

GONADS: Testes & ovariesTESTOSTERONE Secondary male sex characteristics Role in development of male sex organ during puberty Neccesary for maturation and quality of sperm cells

OESTROGEN Secondary female sex characteristics Role in development of female sex organs during puberty Responsible for thickening of endometrium and

preparation for implantation

PROGESTERONE Responsible for further thickening of endometrium and

maintenance therof during pregnancy Suppresses release of FSH and LH

END