Hind brain : It is divided into three parts.

Cerebellum :
-Very large & well developed.
- controls coordination and adjustment of movements (equilibrium) and posture.

Pons varolii :
-It lies above the medulla oblongata.
-It controls some aspects of respiration.

Medulla oblongata :
-It is the posterior most part of the brain.
-continues into the spinal cord.
-It controls involuntary functions of the body :
heart beat
rate of breathing,
secretion of saliva
swallowing
coughing
sneezing
vomiting

(II)Spinal cord :
Spinal cord is a cylindrical structure.
The spinal cord starts from medulla and extends downwards.
It is enclosed by vertebral column.
Spinal cord is also surrounded by membranes called meninges.
31 pairs of nerves arise from the spinal cord .
Function:
-It is responsible for spinal reflex actions
-conductions of nerve impulses to and from the brain.
Reflex action -the response which is at the level of spinal cord itself.
•It is a rapid automatic response to a stimulus by an organ or a system of organs, which does
not involve the brain for its initiation.
• A reflex action is an unconscious (without will) and involuntary response of effectors (muscles
or glands) to a stimulus.
 The pathway taken by nerve impulses in a reflex action is called the
reflex arc.
• Examples of reflex actions :
(i) Withdrawal of hand when pricked with a needle.
(ii) Closing of eyes when flashed with strong light.

Peripheral nervous system(PNS) :

It includes cranial nerves and spinal nerves.
• It mainly controls the voluntary activities of the body.
• Cranial nerves also called cerebral nerves arise from brain.
• 12 pair of cranial nerves
 31 pair of spinal nerves arise from spinal cord.

Autonomic nervous system (ANS): ‘

‘self governing nervous system’.
-It controls and regulates the functions of the internal organs of our body
involuntarily such as heart, blood vessels, glands & smooth muscles of alimentary canal &
uterus.
-It is subdivided into
• Sympathetic & Parasympathetic system :

-Organs receive nerves from both sympathetic and parasympathetic nerve fibres.
-They have opposite effects on the organs if one is stimulatory, the other is inhibitory.
CHEMICAL CO-ORDINATION IN HUMANS
• Any chemical substance which is formed in endocrine glands is carried by the
blood to other parts of the body for its specific actions is termed as hormone.
Characteristics of hormones :
• They are the secretions of endocrine glands.
• They are produced at a place and act on target organs which are
mainly away from their source.
• They are poured directly into the blood stream.
• They are required in very small quantities.
Endocrine system : A group of endocrine glands which produces
various hormones is called as endocrine system.
The endocrine glands present in the human body are : 
1. Hypothalamus gland
2. Pineal gland
3. Parathyroid glands
4. Adrenal glands
5. Pancreas
6. Pituitary gland
7. Thyroid gland
8. Thymus
9. Ovaries (only in females)
10. Testes (only in males)
The hormones produced by endocrine glands act as messengers
between the nervous system and the organs of our body. 

1.Hypothalamus -present in the brain.

Function:To regulate the secretions of hormones from pituitary
gland.
2. Pituitary Gland (or Hypophysis) : 
 • It is a small ovoid structure attached to the base of brain
(hypothalamus) by a short stalk called infundibulum. 
 • Pituitary gland is also known as the master gland as it controls
other endocrine glands. 
• This gland consists of three lobes-anterior, middle and posterior.  
• Each lobe of the pituitary gland secretes different sets of
hormones. 
Hormones of anterior lobe of pituitary :
1. Growth hormone (GH) : This hormone promotes and regulates the
process of growth in the body.  
• It’s deficiency during childhood leads to dwarfism
  over secretion leads to gigantism and acromegaly in adult.

2.Thyroid stimulating hormone (TSH) :

It controls the functioning of thyroid gland.  
 • It stimulates thyroid gland to secrete thyroxine.

3.Follicle stimulating hormone (FSH) :

 stimulates the production of gametes. 

4.Leuteinizing hormone : t stimulates the production of

hormones. 

Hormones of mid lobe of pituitary : 

1. Melanocyte stimulating hormone (MSH) : This is the only
hormone secreted by middle pituitary.
- controls the growth and development of melanocytes
responsible for skin colour.  

Hormones of posterior lobe of pituitary : 

(I) Vasopressin or Antidiuretic hormone (ADH) : This causes the
reabsorption of water into the blood and results in
concentrating the urine and reducing its volume. 
(II) Oxytocin : stimulates uterus contractions at the time of child
birth and causes release of milk from mammary glands.  
• It is also known as birth hormone or milk ejecting hormone.

3.Pineal Gland : 
• It is a small gland reddish-grey in colour
 size of a pea
 • It regulates the biological clock (circadian rhythm). 
• It contributes in regulating gonadal development.
 It controls development & concentration of melanin.
 It secretes melatonin hormone.

4. Thyroid Gland : The thyroid gland consists of two lobes

joined together by an isthmus. 
• It is situated in the lower part of the neck .
Two hormones secreted by the thyroid gland are :
(i) Thyroxine:  
• It increases the metabolic rate of the organs
• The basal metabolic rate (B.M.R.) is increased in
hyperthyroidism and reduced in hypothyroidism.
Hypothyroidism :  low production of thyroxine
• Cretinism in children
• Iodine deficiency causes simple goitre in adults. 
Hyperthyroidism :
Excessive amount of thyroxine production causes toxic goitre or
exophthalamic goitre (grave’s disease).
(ii) Calcitonin:
lowers the blood calcium level in two ways : • By inhibiting
calcium reabsorption from urine.
• By raising calcium reabsorption by bones.

5. Parathyroid Gland : 
• small ovoid pea shaped glands.
They lie behind the thyroid gland.
Parathormone (Collip’s hormone)
•  t regulates the balance between the calcium in bones and in
extracellular tissue fluid, thus affecting the amount of calcium in the
blood.
• It increases the blood calcium level.
•  t also controls the excretion of phosphates in the urine.

7. Thymus Gland : 
• This gland is situated in the thorax in midline under the sternum in
front of trachea. 
Thymosin.
It helps in producing T-lymphocytes.

8. Adrenal Gland : 
• These are two small semilunar structures lying one each on upper
pole of the kidneys.
• Each gland consists of two separate parts known as cortex and
medulla. 
• Cortex secretes three different kinds of hormones known as
corticosteroids.
They are :
(I) Mineralocorticoids : These regulate sodium and potassium
balance in the body.
(II) Glucocorticoids : These derive their name from their influence
on carbohydrate metabolism. e.g. Glycogenesis is promoted in
liver.
(III) Sex hormones : Small quantities of sex hormones as androgens
and oestrogen are produced by adrenal glands which influence
sexual development and growth. 
Adrenal medulla :
It secretes two hormones.
(I) Adrenaline : t is a stress hormone causes increase in blood
pressure, dilation of coronary blood vessels, increased sweating
and increase in metabolic rate. 
It brings restlessness, muscle fatigue and anxiety.
(II) Noradrenaline : It is a general vasoconstrictor, increases both
systolic and diastolic pressures. 
• Both of these hormones are helpful in emergency conditions.
Thus are called as “fight or flight response” or 3F’s.

9. Ovary :
Secretes progesteron (pregnancy hormone) and estrogen that develop
secondary sexual characters of female.

11. Testis : Secretes Testosterone (spermatogenesis & secondary

sexual characters).