Parts Of Brain	Function
Cerebrum	The cerebrum controls the voluntary motor actions. It is the site of sensory perceptions; like tactile and auditory perceptions. It is the seat of learning and memory.
Cerebellum	It coordinates the motor functions.
Hypothalmus	It controls sleep and wake cycle (circadian rhythm) of the body. It also controls the urges for eating and drinking.
Medulla	Medulla controls various involuntary functions; like hear beat, respiration, etc.

Central nervous system is composed of the brain and spinal cord. Peripheral nervous system is composed of nerves which are outside the spinal cord. Central nervous system has a well-developed system for protection. Brain is enclosed in skull for protection. Spinal cord is enclosed in vertebral column for protection. Additionally, the cerebrospinal fluid provides a cushion against mechanical shocks.

(a) Thyroxin
 Ans. General metabolism
(b) Insulin
 Ans. Glucose metabolism
(c) Adrenaline
 Ans. Preparing the body for emergencies
(d) Growth hormone
 Ans. Growth
(e) Testosterone. 
Ans. Secondary sexual characters

Various plant hormones and their effects are as follows:

• Auxin: Promotes cell elongation and thus promotes growth of a plant part.
• Gibberellins: Promotes growth.
• Cytokinin: Promotes cell division and thus promotes growth.
• Abscissic acid: Inhibits growth and is responsible for shedding or older parts.

The sudden involuntary movement in a voluntary organ; in response to a stimulus; is called reflex action.
 Examples of reflex action:
 (a) Moving your hand away from a hot iron plate
 (b) Blinking of eyes

Reflex Arc: The path of electrical impulse during a reflex action is called reflex arc. A reflex arc is composed of a sensory neuron, spinal cord, motor neuron and muscle. It involves following steps:
• The sensory neuron picks signals from the stimulus and carries the signals to the spinal cord.
• Spinal cord process the signals and sends message through the motor neuron.
• Motor neuron transmits the signals to the effector muscle so that the muscle can take immediate action. 

Control and coordination of functioning of various systems is under the direct control of nervous system. It is the nervous system which governs the way a particular organ or organ system has to work. This control is achieved by a complex network of neurons which carry signals in the form of electric impulses; to and from the brain.

 The hormonal system, on the other hand, coordinates the functioning of nervous system. The hormonal system has somewhat indirect control on various functions. It tells a system to either slow down or pace; according to the situation. 
 
 Nervous and hormonal systems are complementary to each other. Thus, it can be said that nervous and hormonal system together perform the function of control and coordination in human beings 

Hormones facilitate chemical control in animals. Hormones are chemicals which are directly released in bloodstream. A particular hormone reaches the target site through blood. Hormone tells the target tissue to behave in a particular manner. To understand this, let us takes the example of adrenalin. Adrenalin is secreted by adrenal gland. It reaches the heart and lungs and also to the GI tract. Heart speeds up its pumping action so that more blood could be supplied to the limbs and facial muscles. But activity of the GI tract is slowed down to ensure better blood supply in limbs. Thus, adrenalin prepares the body for a fight or flight situation.

Electrical impulse travels through a neuron. But to be transmitted to another neuron, it need to be passed in the form of neurotransmitters. Neurotransmitters are specialized chemicals. These can enter a neuron only through specialized channels. Such channels are present in dendrites but not in axon. On the other hand, a neurotransmitter can enter a dendrite. Due to this, the flow of signals in a synapse is from axonal end of one neuron to dendritic end of another neuron but not the reverse.