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

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

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)

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

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.co m for more information about the nervous system. Make a brochure outlining recent medical advances. tx.science. glencoe.co m 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

Peripheral Nervous System Two divisions –Somatic –Autonomic

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

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