Second messengers are a substance that trigger communication inside the cell . This happens after the action of neurotransmitters and hormones.  Second Messengers affect our body in many different ways. One way it affects our body is that it can cause long term changes in the nervous system, manufacture and release neurotransmitter, it affects our Metabolism and it also affects our growth and development. A second messenger results in a cellular response.

seurotransmitters are the chemical messengers of the brain. Neurotransmitters cross the synapse and they simulate the next neuron. They do this by binding to receptors.  Binding to the next neuron causes the sending of the next action potential, contradiction of muscles or the stimulation of enzymes.   The first Neurotransmitter ever discovered was Acetylcholine. Acetylcholine is essential for the stimulation of muscles that includes the gastro-intestinal system.  Acetylcholine is also critical for regular attention memory and normal sleep. Acetylcholine is broken down by an enzyme named Acetylcholinesterase.  Blocking Acetylcholine can cause myasthenia gravis.   2 other amino acid neurotransmitters are GABA and Glutamate. GABA function is to inhibit the firing of neurons. GABA's activity increase by Benzodiazepines and by anticonvulsant drugs.  This can prevent seizures. Huntington's disease happens when GABA producing neurons degenerate.  Glutamate induces the firing of neurons.  Glutamate binds to a NMBA receptors. This is implicated in learning and memory.  An over stimulation  of NMBA causes stroke, seizures and nerve damage. Another type of Neurotransmitter is called Catecholamines.  The most popular type of  Catecholamines is dopamine. Dopamine regulates movement and endocrine system, important for cognition & emotion.  Another type  Catecholamines is Norepinephrine.  Norepinephrine is secreted by sympathetic system & adrenal gland during stress it is also  important for learning and memory. Another type of Neurotransmitter is called serotonin. Serotonin is important for sleep quality, mood, depression and anxiety.  A drug that alters serotonin is named Fluoxetine.   Fluoxetine  

In the brain there are 2 types of cells Neurons and Glial Cells. There are 10 times more Glial in the brain than neurons.  Glial cells are found in both the CNS and the PNS.   Glial cells are a general name given to a variety of cells. Some types of Glial cells in the CNS contain Oligodendrocytes, Astrocytes , Ependymal cells and Microglia.  Oligodendrocytes are responsible for forming Myelin sheaths and wrapping it around axons.  Astrocytes have many functions.  Astrocytes from support for the CNS.  Astrocytes also help from the Blood-Brain barrier. Another function of is to secrete Nerurotropic factors.  Astrocytes  also take up K+ neurotransmitters.  Ependymal cells create barriers between cells. Microglia act as the immune system of the brain it protects the brain from bacteria and other harmful things that try to enter the brain.  Another function of microglia is to act like scavengers .  The PNS contains its own kinds of Glial Cells. One type is known as Schwann cells. Schwann cells feature similar functions as Oligodendrocytes in the CNS. Both Schwann cells and Oligodendrocytes help from Myelin sheaths.  However Schwann cells also secrete Neurotropic factors.  The last type of Glial cells in the PNS are satellite cells. Satellite cells support cell bodies.

The mammal brain contains 100 million to 1 billion neuron.  there are 3 main parts of the neuron ( Cell Body , Axon and Dendrites).  The Cell Body integrates signals and it coordinates metabolic activity.  The Axon looks like a long arm extending from the Cell Body.  The Axon transmitters the action potential. The Axon is insulated by a myletian sheath. This forces the action potential to jump from one Node of Ranvier to the other one.  Dendrites extend out of the cell body. Dendrites recive messages from other Neurons. 

The Nervous system is divided into 2 parts. The CNS ( central nervous system) and the PNS ( peripheral nervous system).  The CNS contains the Brain , Spinal cord and the retina of the eyes.  The PNS contains the nerves and the ganglia. 

There are 4 lobes of the brain ( The Frontal Lobe ,Temporal Lobe , Ocipital Lobe and Paratieal Lobe).  The frontal lobes are involved in motor function, problem solving,  memory, language, initiation, judgement, impulse control, and social behavior.  The temporal lobe is involved in primary auditory perception, such as hearing.  The occipital lobe is invololved in vision. and depth persecption. The paratieal lobe is used in understanding the 5 senses. 

There is 2 views of the brain the lateral view and the superior view. The brain can be divided into 2 hemispheres the left hemisphere and the right hemisphere. The 2 halves are joined together by the corpus callousm.  The cerebrum is the largest part of the brain and it contains all 4 lobes of the brain. The cerebellum is referred  to as the little brain and it is used in actions that use precise timing such as catching a ball.