The Nervous System

1. The Nervous System

2. 4 Functions of the Nervous System • Gathers information both from the outside world and from inside the body. • Transmits the information to the processing area of the brain and spinal cord. • Processes the information to determine the best response.  • Sends information to muscles, glands, and organs (effectors) so they can respond correctly. 

3. The Central Nervous System (CNS) • consists of the Brain and the Spinal Cord • the Spinal Cord carries messages from the body to the Brain where they are analyzed and interpreted • response messages are then passed from the Brain through the Spinal Cord and to the rest of the Body.

4. The Peripheral Nervous System (PNS) • consists of the neurons NOT Included in the Brain and Spinal Cord • Afferent Neurons Collect Information from the Body and Transmit it TOWARD the CNS.  • Efferent Neurons Transmit Information AWAY from the CNS. 

5. The Somatic Nervous System • regulates activities that ARE UNDER CONSCIOUS CONTROL, movement of skeletal muscles. • many nerves within this system are part of reflexes and can act automatically.

6. The Autonomic Nervous System • regulates involuntary activities • are not under conscious control • is responsible for maintaining homeostasis in the functioning of organs • EXAMPLES:  heart beat, digestion, breathing

7. Sympathetic Nervous System • generally ACTIVATES ORGANS or SPEEDS UP

8. Parasympathetic Nervous System • generally RETARDS ORGANS or SLOWS DOWN • Most organs are under control of both Sympathetic and Parasympathetic Neurons.

9. The Neuron

10. The Cell Body • contains the nucleus and much of the cytoplasm • responsible for most of the metabolic activity of the cell, including the generation of ATP and synthesis of protein

11. Dendrites • short branch extensions spreading out from the cell body • dendrites receive STIMULI and carry IMPULSES from the environment or from other neurons and carry them TOWARD the cell body.

12. AXON • long fiber that carries impulses AWAY from the cell body • each neuron has only ONE AXON • ends in a series of small swellings called AXON TERMINALS • Axons of most Neurons are covered with a Lipid Layer known as the MYELIN SHEATH.

13. The Myelin Sheath • both Insulates and Speeds Up transmission of Action Potentials through the Axon • In the PNS, is produced by SCHWANN CELLS, which surround the Axon • GAPS in the Myelin Sheath along the length of the Axon are known as the NODES OF RANVIER

14. Characteristics of Neurons • Nervous messages are called impulses. • A Neuron carries impulses in only ONEdirection • Impulses are in the from of electric signals

15. Types of Neurons Interneurons, Efferent or Motor Neurons, Afferent or Sensory Neurons

16. Afferent Neurons(Sensory) • carry impulses from the SENSE ORGANS to the Brain and Spinal Cord • detect external or internal changes and send the information to the Central Nervous System by way of the Afferent Neurons

17. Efferent Neurons(Motor) • carry impulses from the Brain and Spinal Cord to MUSCLES or GLANDS • in response to impulses, Muscles Contract and Glands Secrete

18. Interneurons • Connect Sensory and Motor neurons and carry impulses between them  • are found entirely within the Central Nervous System