1. The Nervous System C-Scope 2010 Unit 5, Lesson 2

2. The Nervous System Fun Facts: Fun Facts: The brain is composed of 85% water. The brain is composed of 85% water. The brain uses 25% of the body’s oxygen supply. The brain uses 25% of the body’s oxygen supply. The average brain has a mass of 1.6 kg (about 3 pounds) The average brain has a mass of 1.6 kg (about 3 pounds) Your brain could power a 10 watt light bulb! Your brain could power a 10 watt light bulb!

3. The Nervous System The nervous system is the body’s control center and communication network. The nervous system is the body’s control center and communication network. The nervous system allows us to think, evaluate, and remember information. The nervous system allows us to think, evaluate, and remember information. The most important part of the nervous system is the neuron or nerve cell. The most important part of the nervous system is the neuron or nerve cell.

4. Neurons This is the working unit (cell) of the nervous system. This is the working unit (cell) of the nervous system. The neuron is made up of a cell body and branches called dendrites and axons. The neuron is made up of a cell body and branches called dendrites and axons. Dendrites receive messages and send them to the body cells. Dendrites receive messages and send them to the body cells. Axons carry messages away from the neuron. Axons carry messages away from the neuron. A message received is called an impulse. A message received is called an impulse.

5. Neuron Dendrite Nucleus Axon Direction of Impulse

6. The Nervous System There are three functions of the nervous system: There are three functions of the nervous system: Sensory Input Sensory Input Integration Integration Motor Input Motor Input

7. Sensory Input When the eyes see something or hands touch a warm surface, the neurons send a message straight to the brain. When the eyes see something or hands touch a warm surface, the neurons send a message straight to the brain. This action of getting information from the surrounding environment is called sensory input because things are being sent to the brain by way of the senses. This action of getting information from the surrounding environment is called sensory input because things are being sent to the brain by way of the senses.

8. Sensory Neurons Receives sensory input and sends an impulse TO the spinal cord or brain. The input comes from structures in the skin called receptors (your nerves).

9. Integration The interpretation, or translation, of things that have been felt, tasted, and touched with the sensory neurons into responses that the body recognizes. The interpretation, or translation, of things that have been felt, tasted, and touched with the sensory neurons into responses that the body recognizes. This process is accomplished by the brain. This process is accomplished by the brain.

10. Interneurons Through out the brain and spinal cord Through out the brain and spinal cord Relays impulses from sensory neurons to motor neurons. Relays impulses from sensory neurons to motor neurons. “The Middle Man” “The Middle Man” There are more of these than sensory and motor neurons. There are more of these than sensory and motor neurons.

11. Motor Output Once your brain has interpreted all that has been sent by using any of the senses, then your brain sends a message through neurons to muscle or other cells, which work to perform the response.

12. Nervous System

13. The human nervous system is divided into two parts: The human nervous system is divided into two parts: The Central Nervous System The Central Nervous System The Peripheral Nervous System The Peripheral Nervous System

14. Central Nervous System It is the body’s most rapid means of maintaining homeostasis. Regulates vital bodily functions by sensing changes within the body and from the environment. Interprets the changes and makes adjustments in a split-second by delivering electrochemical impulses. These impulses result in muscular contractions and/or glandular secretions.

15. Central Nervous System The central nervous system consists of the brain and the spinal cord and association neurons. These neurons make up most of the spinal cord and change the input impulse to output impulses and cause the body to respond.

16. Peripheral Nervous System Peripheral nervous system– There are two types of neurons in this system. Sensory Neurons Motor Neurons

17. More on Sensory Neurons Send information to the central nervous system from internal organs, from the environment, and motor neurons; which send impulses to the voluntary and involuntary muscles.

18. More on Motor Neurons Divided into the somatic nervous system and the autonomic nervous system Somatic – controls the skeletal muscles and external sensory organs such as the skin This system is said to be voluntary because the responses can be controlled consciously. An exception is the reflex reactions of skeletal muscle. These are involuntary reactions to external stimuli. Autonomic Nervous System controls involuntary muscles such as smooth and cardiac muscle. This system is also called the involuntary nervous system.