The Nervous System Central Nervous System Peripheral Nervous

The Nervous System Central Nervous System Peripheral 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 – 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