The Nervous System Peripheral Nervous System Central Nervous System

Organs of the Nervous System The nervous system consists of: brain spinal cord nerves neurons sense organs

The Neuron

The Brain

Functions of the Nervous System Your nervous system is a communications network Receiving information Responding to stimuli Maintaining homeostasis

Receiving Information Because of your nervous system, you are aware of what is happening in the environment around you Your brain is also aware of your internal conditions like temperature and glucose level

Responding to Stimuli After receiving information, your nervous system analyzes the data and causes a response Putting your hand in front of your face if a ball is coming at you Increasing your heart rate when exercising

Maintaining Homeostasis The nervous system maintains homeostasis by directing the body to respond correctly to the information it receives When you are hungry, your brain tells you to eat

Central Nervous System The control center of the body Composed of your: Brain – controls most functions Spinal Cord – thick column of nerve tissue that links the brain to nerves in the peripheral nervous system

Brain The brain contains 100 million neurons The skull, layers of connective tissue, and fluid protect the brain from injury The brain is composed of three main parts Cerebrum Cerebellum Brain stem

Cerebrum Largest part of the brain reads input from the senses controls skeletal muscles In charge of learning, remembering and making judgments

Cerebrum Right side Left side controls left side of body controls creativity and artistic ability Left side controls right side of body Controls math, speech, writing, and logic

Cerebellum Second largest part of your brain Coordinates actions of your muscles Helps you keep your balance

Brain Stem Lies between the cerebellum and spinal cord Controls involuntary actions Breathing Heartbeat

Spinal Cord The link between your brain and peripheral nervous system Protected by bone, connective tissue and fluid

Peripheral Nervous System Consists of a network of nerves that branch out from the central nervous system Made up of 43 pairs of nerves 12 begin in the brain 31 begin in the spinal cord One nerve in each pair goes to the right side and one to the left

The Neuron Neurons are cells that carry information around your body Nerve impulse - The message a neuron carries

The Neuron The cell body of the neuron has two extensions Dendrite – carries impulses to the cell body Axon – carries impulses away from the cell body The nerve impulse begins in the dendrite, moves to the cell body then moves down the axon

The Neuron signal goes from axon to dendrite

Kinds of Neurons Different kinds of neurons perform different functions Sensory neurons Interneurons Motor neurons

Sensory Neuron Picks up stimuli from the internal or external environment and converts each stimulus into a nerve impulse The impulse travels along the sensory neuron until it reaches an interneuron in the brain or spinal cord sensory impulse travels at 76.2 m/s

Interneuron Neuron that carries nerve impulses from one neuron to another Can pass stimuli from sensory neuron to motor neuron

Motor Neuron Send an impulse to a muscle and the muscle contracts in response Motor impulse travels at 119 m/s

How a Nerve Impulse Travels Millions of nerve impulses travel your body each day The nerve impulse travels along the neuron in the form of electrical and chemical signals

How a Nerve Impulse Travels There are tiny spaces or synapses between a neuron and the next structure A nerve impulse must jump this gap Axon tips release a neurotransmitter that allows the impulse to travel the gap

How a Nerve Impulse Travels Drugs and alcohol can affect the neurotransmitters alcohol increases reaction time depressants, like marijuana also increase reaction time stimulants, like meth, decrease reaction time

The Path of a Nerve Impulse

Reflex A reflex is an automatic response that occurs very rapidly and without conscious control Reflexes protect us from pain and injury

Reflexes

Body systems that work with the nervous system; The nervous system works with every system in the body

Comparing Cells to the Body The cell part that controls the cell is the nucleus