Endocrine System

 
12.6 Endocrine System
 
  • Endocrine gland is a ductless gland that secretes hormones directly into the blood
  • The endocrine gland consists of a mass of cells, tissues or organs
  • Hormone is a chemical substance made up of proteins or steroids which can regulate physiological processes in humans and animals
 
Endocrine glands and their secretion:
 
Endocrine gland Secretion
Hypothalamus Gonadotropin-releasing hormone (GnRH)
Thyroid gland Thyroxine
Pituitary gland

Growth hormone (GH)

Antidiuretic hormone (ADH)

Follicle-stimulating hormone (FSH)

Luteinizing hormone (LH)

Thyroid-stimulating hormone (TSH)

Adrenocorticotrophic hormone (ACTH)

Prolactin

Oxytocin

Pancreas

Insulin

Glucagon

Adrenal gland

Aldosterone

Adrenaline

Androgen

Cortisol

Ovary

Oestrogen

Progesterone

Testis Testosterone
 
Functions of hormones:
 

Gonadotropin-releasing hormone (GnRH)

Target tissue/organ: pituitary gland

Function: regulates activities of the pituitary gland to secrete LH and FSH

 

Growth hormone (GH)

Target tissue/organ: liver and adipose tissue

Function: stimulates growth especially in bone and muscle and regulates the metabolism of proteins, lipids and carbohydrates

 

Follicle-stimulating hormone (FSH)

Target tissue/organ: testis and ovary

Function: stimulates the development of follicles in the ovary, stimulates the formation of sperms in the testis and stimulates the ovaries to secrete oestrogen

 

Luteinizing hormone (LH)

Target tissue/organ: testis and ovary

Function: stimulates testis to produce testosterone in males and stimulates the ovary to perform ovulation and formation of corpus luteum in females

 

Thyroid-stimulating hormone (TSH)

Target tissue/organ: thyroid gland

Function: stimulates the thyroid gland to secrete thyroxine

 

Adrenocorticotropic hormone (ACTH)

Target tissue/organ: adrenal gland

Function: stimulates adrenal cortex to secrete corticoid hormones and regulates the growth of the adrenal cortex

 

Oxytocin

Target tissue/organ: uterus muscles and mammary gland

Function: simulates the contraction of the uterus during birth and stimulates the mammary gland to secrete milk

 

Antidiuretic hormone (ADH)

Target tissue/organ: kidney

Function: Stimulates the kidneys to reabsorb water and reduces the production of urine

 

Prolactin

Target tissue/organ: mammary gland

Function: stimulates the mammary gland to secrete milk

 

Thyroxine

Target tissue/organ: all tissues

Function: stimulates, maintain the rate of metabolism in the body and controls physical growth and normal development of the brain

 

Insulin

Target tissue/organ: liver, muscles and adipose tissues

Function: lowers blood glucose level by stimulating the uptake of glucose into cells for metabolism and converts excess glucose into glycogen

 

Glucagon

Target tissue/organ: liver, muscles and adipose tissues

Function: raises blood glucose level by stimulating the conversion of glycogen into glucose

 

Adrenaline

Target tissue/organ: heart, liver and muscles 

Function: increases blood glucose level and rises metabolic activities such as heartbeat rate, breathing rate, vasodilation and vasoconstriction of blood vessels for preparing the body in a "fight or flight" situation

 

Aldosterone

Target tissue/organ: kidney

Function: stimulates the absorption of mineral salt in kidneys

 

Androgen

Target tissue/organ: reproductive organs

Function: important to reach puberty and regulates the maturity of reproductive organs and the development of secondary sexual characteristics

 

Cortisol

Target tissue/organ: all tissues

Function: stimulates the conversion of lipids and proteins into glucose and produced during fight and flight situations to increase the blood sugar level

 

Testosterone

Target tissue/organ: male reproductive organs

Function: stimulates sperm production and stimulates the development of secondary sexual characteristics in males

 

Oestrogen

Target tissue/organ: female reproductive organs

Function: stimulates the development of female reproductive organs, repairs and build the uterine wall, and stimulates the secondary sexual characteristics in female

 

Progesterone

Target tissue/organ: uterus

Function: maintains the thickening of the uterine wall for embryo implantation

 

Coordination of both nervous system and endocrine system in an anxious situation:

 
  • Stimulus of fear occurs
  • Nerve impulse sent to the central nervous system
  • Central nervous system interprets information
  • Heartbeat increases
  • Breathing rate increases
  • Blood pressure increases
  • Metabolic rate increases
  • Blood glucose level increases
  • Energy production increases
  • Skeletal muscles use the energy to fight or flight
 
Comparison between the nervous system and endocrine system:
 
Similarities
  • Both systems play important roles in the coordination and response of the body toward stimuli
  • Coordinates all body activities
  • Both systems have cell, tissue or organ as target
Nervous system Endocrine system

Consists of nerve tissue

Signals are transmitted via nerve impulses and neurotransmitters

The signal is sent along the neurones

The transmission of electrical impulses is rapid

The region of response is small, limited to a specific region

The effect is short-lived and reversible

Involves voluntary and involuntary actions

Involves in the movement of the body

Comprises of endocrine glands

The signal is sent via hormones

The signal is sent by blood circulation

The delivery of hormones is relatively slow

The region of response is wider, involved few target organs

Only involves involuntary actions

Involves in physiological processes in the body

 

Endocrine System

 
12.6 Endocrine System
 
  • Endocrine gland is a ductless gland that secretes hormones directly into the blood
  • The endocrine gland consists of a mass of cells, tissues or organs
  • Hormone is a chemical substance made up of proteins or steroids which can regulate physiological processes in humans and animals
 
Endocrine glands and their secretion:
 
Endocrine gland Secretion
Hypothalamus Gonadotropin-releasing hormone (GnRH)
Thyroid gland Thyroxine
Pituitary gland

Growth hormone (GH)

Antidiuretic hormone (ADH)

Follicle-stimulating hormone (FSH)

Luteinizing hormone (LH)

Thyroid-stimulating hormone (TSH)

Adrenocorticotrophic hormone (ACTH)

Prolactin

Oxytocin

Pancreas

Insulin

Glucagon

Adrenal gland

Aldosterone

Adrenaline

Androgen

Cortisol

Ovary

Oestrogen

Progesterone

Testis Testosterone
 
Functions of hormones:
 

Gonadotropin-releasing hormone (GnRH)

Target tissue/organ: pituitary gland

Function: regulates activities of the pituitary gland to secrete LH and FSH

 

Growth hormone (GH)

Target tissue/organ: liver and adipose tissue

Function: stimulates growth especially in bone and muscle and regulates the metabolism of proteins, lipids and carbohydrates

 

Follicle-stimulating hormone (FSH)

Target tissue/organ: testis and ovary

Function: stimulates the development of follicles in the ovary, stimulates the formation of sperms in the testis and stimulates the ovaries to secrete oestrogen

 

Luteinizing hormone (LH)

Target tissue/organ: testis and ovary

Function: stimulates testis to produce testosterone in males and stimulates the ovary to perform ovulation and formation of corpus luteum in females

 

Thyroid-stimulating hormone (TSH)

Target tissue/organ: thyroid gland

Function: stimulates the thyroid gland to secrete thyroxine

 

Adrenocorticotropic hormone (ACTH)

Target tissue/organ: adrenal gland

Function: stimulates adrenal cortex to secrete corticoid hormones and regulates the growth of the adrenal cortex

 

Oxytocin

Target tissue/organ: uterus muscles and mammary gland

Function: simulates the contraction of the uterus during birth and stimulates the mammary gland to secrete milk

 

Antidiuretic hormone (ADH)

Target tissue/organ: kidney

Function: Stimulates the kidneys to reabsorb water and reduces the production of urine

 

Prolactin

Target tissue/organ: mammary gland

Function: stimulates the mammary gland to secrete milk

 

Thyroxine

Target tissue/organ: all tissues

Function: stimulates, maintain the rate of metabolism in the body and controls physical growth and normal development of the brain

 

Insulin

Target tissue/organ: liver, muscles and adipose tissues

Function: lowers blood glucose level by stimulating the uptake of glucose into cells for metabolism and converts excess glucose into glycogen

 

Glucagon

Target tissue/organ: liver, muscles and adipose tissues

Function: raises blood glucose level by stimulating the conversion of glycogen into glucose

 

Adrenaline

Target tissue/organ: heart, liver and muscles 

Function: increases blood glucose level and rises metabolic activities such as heartbeat rate, breathing rate, vasodilation and vasoconstriction of blood vessels for preparing the body in a "fight or flight" situation

 

Aldosterone

Target tissue/organ: kidney

Function: stimulates the absorption of mineral salt in kidneys

 

Androgen

Target tissue/organ: reproductive organs

Function: important to reach puberty and regulates the maturity of reproductive organs and the development of secondary sexual characteristics

 

Cortisol

Target tissue/organ: all tissues

Function: stimulates the conversion of lipids and proteins into glucose and produced during fight and flight situations to increase the blood sugar level

 

Testosterone

Target tissue/organ: male reproductive organs

Function: stimulates sperm production and stimulates the development of secondary sexual characteristics in males

 

Oestrogen

Target tissue/organ: female reproductive organs

Function: stimulates the development of female reproductive organs, repairs and build the uterine wall, and stimulates the secondary sexual characteristics in female

 

Progesterone

Target tissue/organ: uterus

Function: maintains the thickening of the uterine wall for embryo implantation

 

Coordination of both nervous system and endocrine system in an anxious situation:

 
  • Stimulus of fear occurs
  • Nerve impulse sent to the central nervous system
  • Central nervous system interprets information
  • Heartbeat increases
  • Breathing rate increases
  • Blood pressure increases
  • Metabolic rate increases
  • Blood glucose level increases
  • Energy production increases
  • Skeletal muscles use the energy to fight or flight
 
Comparison between the nervous system and endocrine system:
 
Similarities
  • Both systems play important roles in the coordination and response of the body toward stimuli
  • Coordinates all body activities
  • Both systems have cell, tissue or organ as target
Nervous system Endocrine system

Consists of nerve tissue

Signals are transmitted via nerve impulses and neurotransmitters

The signal is sent along the neurones

The transmission of electrical impulses is rapid

The region of response is small, limited to a specific region

The effect is short-lived and reversible

Involves voluntary and involuntary actions

Involves in the movement of the body

Comprises of endocrine glands

The signal is sent via hormones

The signal is sent by blood circulation

The delivery of hormones is relatively slow

The region of response is wider, involved few target organs

Only involves involuntary actions

Involves in physiological processes in the body