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The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of human and transmit signals between different parts of its body. The human nervous system has two main divisions as seen in the concept map, they are the central nervous system and the peripheral nervous system. Two main system: - The central nervous system (CNS) contains the brain and spinal cord. - The peripheral nervous system (PNS) includes the somatic motor nervous system, and the autonomic nervous system.
 * The nervous system **

1) The largest part. 2) Enclosed and protected by meninges, a three-layered system of membranes. 3) Acts as the central control region of the nervous system because it processes information and issues commands.
 * The central nervous system (CNS): **

1) A collective term for the nervous system structures that do not lie within the central nervous system (CNS). 2) Two nervous system: - **The somatic motor nervous system**: consists of the nerves that send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle. - **The autonomic nervous system:** controls smooth muscle of the internal organs and glands. It carries information from the CNS to organs, blood à **//regulates//** heart rate, respiration, digestion and pupil contraction. à **//control//** muscle contraction in walls of blood vessels, digestive, urinary and reproduction tracts. à **//carries messages//** to help stimulate glands to secrete tears, mucus and digestive enzymes - It is divided into two parts: the sympathetic nervous system and the enteric nervous system.
 * The peripheral nervous system (PNS): **


 * Sympathetic Nervous System: ** arouses the body.


 * Parasympathetic Nervous System: ** clams after arousal.

1) A neuron is a cell of the nervous system and has cell membranes and nucleus. Neurons contain cytoplasm, mitochondria and other organelles and carry out basic cellular processes, such as energy production, and information through an electrochemical process.
 * A neuron or a nerve cell: **

2) Three parts: cell body, and axon. Neurons have specialized extensions called dendrites and axons . Dendrites bring information to the cell body and axons take information away from the cell body.

3) Neurons can also be classified by the direction that they send information. - Sensory (or afferent) neurons: send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) toward the central nervous system.  - Motor (or efferent) neurons **:** send information away from the central nervous system to muscles or.  - Interneurons : send information between sensory neurons and motor neurons. Most interneurons are located in the central nervous system.

1) Achemical messenger that carries, boosts and modulates signals between neurons and other cell s in the body. 2)A neurotransmitter is released from one neuron at the axon terminal. Then, neurotransmitters crossthesyn aptic gap to reach the receptor site of the other cell or neuron. 3) Then, in a process known as reuptake, the neurotransmitter attaches to the receptor site and is reabsorbed by the neuron.
 * Neurotransmitter **

4) The action of neurotransmitters can be stopped by four different mechanisms: - Diffusion: Drifting away the neurotransmit ter to out of the synaptic cleft where it can no longer act on a receptor.



- Enzymatic degradation (deactivation): A specific enzyme changes the structure of the neurotransmitter so it is not recognized by the receptor.

- Glial cells: Astrocytes remove neurotransmitters from the synaptic cleft.

- Reuptake: That the whole neurotransmitter molecule is taken back into the axon terminal that released it. So, these neurotransmitters are removed from the synaptic cleft so they cannot bind to receptors.



** The spinal cord **
1) The spinal cord is the extension of the central nervous system and the main pathway for information connecting the brain and peripheral nervous system. 2) The human spinal cord is protected by the bony spinal column that is made up of bones called vertebrae.

3) The spinal cord works by receptors. Receptors in the skin send information to the spinal cord through the spinal nerves. The nerve fibers enter the spinal cord through the dorsal root. Some fibers make synapses with other neurons in the dorsal horn, while others continue up to the brain. Many cell bodies in the ventral horn send axons through the ventral root to muscles to control movement.

- Receptors in the skin -> the spinal nerves -> the dorsal root -> the dorsal horn -> the ventral root -> muscles -> control movement

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Primary organization of the BRAIN


 * 1) ** Hindbrain ** : largely unconscious, but essential functions like breathing, circulation, balance andwakefulness. (also the oldest part of the brain)

//__ medulla __// : involved in regulation basic life functions //__ Pons __// : involved with sleep and wakefulness //__ Cerebellum __// : is involved in controlling balance and coordination
 * Includes ** :


 * 1) ** Midbrain ** : Preliminary integration of vision and hearing.


 * 1) ** Forebrain ** : more complex sensory processing, regulation of biological needs and emotions. Also complex thought.


 * Includes: **
 * //__ Thalamus __//**** : ** relay station for sensory information (sending the info about vision to one area, info about hearing to another area)


 * //__ Hypothalamus: __//** regulates many vital bodily functions: body temperature, reproduction, emotional states, responses to stress, aggression, hunger and thirst.


 * //__ Limbic system: __//** memory and emotional processing

//__ Cerebral cortex: __// Brain’s thinking, calculation, organizing, and creative center. (Takes up most of the room inside the skull )


 * CEREBRUM **

Takes up most of the room inside the skull and the outer covering is called the **cerebral cortex**, which covers the cerebrum like a cap and is no more than an inch thick but essential for thinking, calculating, organizing and creativity. The cerebrum and cerebral cortex are the most recently evolved portions of the brain and they regulate most complex behavior.

The **cerebrum** is divided into two large masses called the **//right//** and **//left hemisphere//**. They in turn are connected by a thick bundle of nerve fibers called **corpus callosum** (latin “thick body”). This connection between the right and left hemispheres is a pathway that each hemisphere uses in order to share information, communication and coordinate their activities.

The **//left and right hemispheres//** share some functions but they are also specialized in certain tasks. The right side of the brain controls the left side of the body and vice versa.


 * Right Hemisphere ** : Visual and spatial tasks, music, visual imagery, face recognition and perception of emotion.


 * Left Hemisphere: ** Language, math and logic

Each hemisphere is divided into four lobes, delineated by deep fissures on the surface of the brain.


 * Occipital Lobes: ** Receives and processes Visual information.


 * Parietal Lobes: ** Receives sensor information from sense receptors all over the body. Touching processing and monitoring body position.


 * Temporal Lobes: ** Involved in complex visual tasks; balance, regulates emotions, strong role in understanding language. Contains centers of hearing, smells and memory.

**//Prefrontal cortex://** executive control functions
 * Frontal lobes: ** coordinate body movements and control fine muscles such as tongue and fingers. Coordinates messages from other cerebral lobes; involved in complex problem solving tasks. Controls higher mental functions like thinking, planning, problem solving, and decision making and accessing and acting on stored memories.



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** Vocabulary Words ** 1. Sensory neurons: send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) toward the central nervous system.

2. Motor neurons **:** send information away from the central nervous system to muscles or glands.

3. Diffusion: Drifting away the neurotransmitter to out of the synaptic cleft where it can no longer act on a receptor.

4. Reuptake: That the whole neurotransmitter molecule is taken back into the axon terminal that released it.

5. The spinal cord is the extension of the central nervous system and the main pathway for information connecting the brain and peripheral nervous system.

6. Cerebrum: The largest and most complex portion of the brain. It controls thought, learning and other complex activities.

7. Cerebral cortex: the outer layer of the cerebrum, composed of six cell layers of deeply folded and ridged gray matter.

8. Corpus callosum: a large bundle of nerve fibers that connect the two cerebral hemispheres.

9.Occiptial lobe: the region at the back of each cerebral hemisphere that contains the center of vision and reading ability.

10. Parietal lobe: the middle lobe of each cerebral hemisphere between the frontal and occipital lobes; it contains important sensory centers and therefore process information relating to touch, pressure, temperature, pain and body movement.

11. Frontal lobe: the top, front regions of each of the cerebral hemispheres. They are used for reasoning, emotions, judgment and voluntary moment.

12. Temporal lobe: the region at the lower side of each cerebral hemisphere; contains center of hearing and memory.