Nervous System

NERVOUS SYSTEM

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 (medulla)

Cerebrum Largest part of the brain Used for: –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

Medulla (Brain Stem) Connects brain to spinal cord Act as pathways connecting various parts of the brain with each other Controls involuntary actions –Breathing, digestion, heart beat

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

PERIPHERAL NERVOUS SYSTEM NERVES AND SENSES

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

STIMULUS /RESPONSE

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

Synapse As 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.

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