Lesson 1

The Human Nervous System

Lesson1: The Human Nervous System

Objectives: • Describe the role and function of the two major divisions of the nervous

system: CNS and PNS

• Describe the role and function of the Somatic Nervous System

Today’s lesson -Central Nervous System CNS -Peripheral Nervous System PNS -Somatic division of PNS

Next Lesson -Autonomic division of PNS (sympathetic and parasympathetic)

Central Nervous System CNS

- The central nervous system is that part of the nervous system that consists of the brain and spinal cord.- The brain is the center of the nervous system in all vertebrate and most invertebrate animals. The brain controls the other organ systems of the body, either by activating muscles or by causing secretion of chemicals such as hormones and neurotransmitters.- The spinal cord is the main pathway for information connecting the brain and peripheral nervous system.

Peripheral Nervous System PNS

-Peripheral means outside the centre or in the surrounding areas.

-The peripheral nervous system (PNS) is comprised of all the neurons outside the central nervous system.

-It is located mainly in the body (with the exception of the spinal cord), although the cranial nerves in the head (outside the skull) are also part of the peripheral nervous system. These are the only nerves in the PNS that enter the brain (CNS) without going via the spinal cord.

-The PNS provides the pathway from the brain and spinal cord to all other parts of the body (including the internal organs and glands).

-It allows two-way communication between the CNS and all other areas. -The peripheral nervous system is separated into two other divisions, which are distinguished by their different functions. These are the somatic nervous system and the autonomic nervous system.

Somatic Nervous System SNS

The somatic nervous system has a sensory function and a motor function.

The sensory function involves the transmission of information to the brain from sensory receptors located at a number of different points throughout the body.

The motor function involves the movement of muscles attached to the body’s skeleton.

Sleep Paralysis - How and Why???Skeletal muscles are those that allow such actions as shaking hands, moving your mouth to speak, and walking. Skeletal muscles become almost totally inactive during the stage of sleep in which most of our dreams occur. This happens because messages from the motor cortex can not reach the somatic branch of the peripheral nervous system due to a “blockage” near the base of the brain. Whilst it is not clear why this happens, it results in a temporary period of “paralysis” of the limbs.