Ch. 19 Sec. 2 Notes Divisions of the Nervous System Central Nervous System



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Ch. 19 Sec. 2 Notes

Divisions of the Nervous System

*Central Nervous System consists of the brain and spinal cord

*Peripheral Nervous System includes all the nerves located outside of the central nervous system
Central Nervous System

*The central nervous system is the control center of the body

-Includes the brain and spinal cord

*The brain, located in the skull, is the part of the central nervous system that controls most functions in the body

*The spinal cord is the thick column of nervous tissue that links the brain to most of the nerves in the peripheral nervous system

-Most impulses travel from the peripheral system through the spine to get to the brain, where it will create a response

-Then the response will travel back down the spinal cord and to the peripheral system to receive the message
The Brain and Spinal Cord

*Your brain contains about 100 billion neurons, all of which are interneurons

*There are 3 main regions of the brain that receive and process information:

1. Cerebrum

2. Cerebellum

3. Brain Stem


Cerebrum

*The largest part of the brain

*Interprets input from the senses, controls movement, and carries out complex mental processes such as learning and remembering

*Divided into a left and right half

-Right half sends impulses to skeletal muscles on the left side of the body

-Left half controls the right side of the body


Cerebellum and Brain Stem

*Cerebellum is second largest part of brain

*Cerebellum coordinates the actions of your muscles and helps you keep your balance

*The brain stem, which lies between the cerebellum and spinal cord, controls your body's involuntary actions

Ex: breathing and control your heart beat

The Spinal Cord

*The spinal cord is the link between your brain and the peripheral nervous system


Peripheral Nervous System

*Consists of a network of nerves that branch out from the central nervous system and connect it to the rest of the body

*Involved in both involuntary and voluntary actions

-43 pairs of nerves make up the peripheral nervous system (12 in brain and 31 in spinal cord)


How Spinal Nerves Function

*Impulses travel on a spinal nerve in two directions -- to and from the central nervous system

*Each spinal nerve contains axons of both sensory and motor neurons

-Sensory neurons carry impulses to the central nervous system

-Motor neurons carry impulses from the central nervous system
Somatic and Autonomic Systems

*The nerves of the peripheral nervous system can be divided into 2 groups:

1. Somatic Nervous System: Control voluntary actions

2. Autonomic Nervous System: Control involuntary actions


Reflexes

*Automatic response that occurs very rapidly and without conscious control

*Help protect the body
A Reflex Pathway

*Some reflexes are controlled by your skeletal muscles that involve the spinal cord and not the brain

Ex: if you touch a sharp object, your spinal cord will tell your arm to move away
Signaling the Brain

*If you touch a sharp object, your brain tells you if you're in pain or not


Nervous System Injuries

*Concussions and spinal cord injuries are two ways in which the central nervous system can be damaged


Concussions

*A concussion is a bruise-like injury of the brain

*Occurs when the soft tissue of the brain collides against the skull

-Usually, the injured tissue heals itself over time


Spinal Cord Injuries

*Occurs with the spinal cord is cut or crushed and impulses cannot pass through anymore



*Usually results in paralysis

-Loss of movement in some part of your body


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