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

http://ilearn.senecac.on.ca/aahs/health/IHP/ottawa/anatomy/neuron/map/neuron.html

http://35.9.122.184/images/40-AnimalStructureAndFunction/

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 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/Volume7/Number1/images/Neuron.jpg

http://mhln.com

An impulse moves in only one direction across a synapse - from an axon to the dendrites or cell body of

another neuron.

Two Parts

• Central (CNS)• Peripheral (PNS)

http://inside.salve.edu/walsh/cns_pns.jpg

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

• Largest part of the brain• Thinking• Memory is stored• Movements are controlled• 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

http://www.cbituk.org/GRAPHICS/brain.gif

The Spinal Cord

• Extension of the brain stem• 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

extension of the brain stem. It is 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

                                                                                                                                                                                                                                                                           Research Visit the Glencoe Science Web site at tx.science.glencoe.com for more information about the nervous system. Make a brochure outlining recent medical advances.

The Peripheral Nervous System Your brain and spinal cord are connected to the rest of your body by the peripheral nervous system. The PNS is made up of 12 pairs of nerves from your brain called cranial nerves, and 31 pairs from your spinal cord called spinal nerves. Spinal nerves are made up of bundles of sensory and motor neurons bound together by connective tissue. For this reason, a single spinal nerve can have impulses going to and from the brain at the same time. Some nerves contain only sensory neurons, and some contain only motor neurons, but most nerves contain both types of neurons.

Somatic and Autonomic Systems The peripheral nervous system has two major divisions. The somatic system controls voluntary actions. It is made up of the cranial and spinal nerves that go from the central nervous system to your skeletal muscles. The autonomic system controls involuntary actions-those not under conscious control-such as your heart rate, breathing, digestion, and glandular functions. These two divisions, along with the central nervous system, make up your body's nervous system.

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/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/BiologyPages/A/autonomic.gif

Reflexes

• Involuntary, automatic response to a stimulus

• Involves a simple nerve pathway called a reflex arc