Nervous System Parts of the Nervous System Brain

Nervous System

Parts of the Nervous System • Brain • Spinal Cord • Nerves

Vocabulary to Know • Homeostasis – The regulation of steady, life-maintaining conditions inside an organism, despite changes in its environment

Nerve Cells • Neurons – Basic functioning units of the nervous system

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Neurons • Made up of a cell body and branches called dendrites and axons – Dendrites receive messages from other neurons and send them to the cell body – Axons carry messages away from the cell body

Any message carried by a neuron is called an impulse

Neurons A message carried by a neuron is called an impulse

Types of Neurons • Sensory • Motor • Interneuron

Sensory Neurons • Receive information • Send impulses to the brain or spinal cord

Interneurons • Send impulses from sensory neurons to motor neurons

Motor Neurons • Conduct impulses from the brain or spinal cord to muscles or glands throughout your body

Synapse • Small space across which an impulse moves from an axon to the dendrites or cell body of another neuron

Synapse • An impulse reaches the end of an axon • Axon releases a chemical • Flows across the synapse • Stimulates the impulse in the dendrite of the next neuron • Impulse moves from neuron to neuron

http: //www. med. harvard. edu/publications/On_The_Brain/Volume 7/Number 1/images/Neuron. jpg

An impulse moves in only one direction across a synapse - from an axon to the dendrites or cell body of another neuron. http: //mhln. com

Two Parts of the Nervous System • Central (CNS) • Peripheral (PNS)

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Central Nervous System • Brain • Spinal cord

The Brain • Coordinates body activities • Made up of approximately 100 billion neurons • Divided into three major parts– the cerebrum – the cerebellum – the brain stem.

Cerebrum • • • The largest part of the brain Where thinking takes place Where memory is stored Where movements are controlled Where impulses from the senses are interpreted.

Cerebellum • Interprets stimuli from eyes, ears, muscles • Controls voluntary muscle movements • Maintains muscle tone • Helps maintain balance

Brain Stem • Connects brain to spinal cord • Made up of: _the midbrain, the pons, Act as pathways connecting various parts of the brain with each other _Medulla controls involuntary actions

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The Spinal Cord • Extension of the brain stem • Bundles of neurons that carry made up of bundles of neurons that carry impulses from all parts of the body to the brain and from the brain to all parts of your body

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Peripheral Nervous System • Connects body to brain & spinal cord • 12 pairs of nerves from your brain (cranial nerves) • 31 pairs from your spinal cord (spinal nerves) – Bundles of sensory and motor neurons held together by connective tissue

http: //www. christopherreeve. org/Research. cfm? ID=178&c=21

Peripheral Nervous System • Two divisions – Somatic – Autonomic

http: //abdellab. sunderland. ac. uk/lectures/Parmacology/Pics/anatomy/PNS. GIF

Somatic Nervous System • Controls voluntary actions • Made up of the cranial and spinal nerves that go from the central nervous system to your skeletal muscles

Autonomic Nervous System • Controls involuntary actions-those not under conscious control-such as your heart rate, breathing, digestion, and glandular functions

http: //users. rcn. com/jkimball. ma. ultranet/Biology. Pages/A/autonomic. gif

Reflexes • Involuntary, automatic response to a stimulus • Involves a simple nerve pathway called a reflex arc