The Nervous System (2:44) Click here to launch video Click here to download print activity

The nervous system sends messages through the nerves to coordinate all the body’s activities.

neurons cerebrum cerebellum brain stem epilepsy cerebral palsy

How the Nervous System Works The nervous system coordinates all of the activities in the body. Your nervous system is a complex network that allows communication between the brain and parts of the body.

How the Nervous System Works The brain, spinal cord, and nerves work together, transmitting messages between organs, tissues, and cells.

How the Nervous System Works The central nervous system (CNS) consists of the brain and spinal cord. The peripheral nervous system (PNS) gathers information from inside and outside your body.

How the Nervous System Works The PNS includes nerves that extend from the brain, spinal cord, and sensory receptors, such as those in the skin. The CNS receives messages from the nerves in the PNS, interprets them, and sends out a response.

Understanding Neurons Neurons transmit messages from the brain and spinal cord to the rest of the body.

Understanding Neurons Neurons transmit messages to and from the spinal cord and brain. Neurons Nerve cells

Understanding Neurons The Three Types of Neurons Sensory Neurons Motor Neurons Interneurons Carry messages from receptors in the body to the CNS. Carry messages from the CNS back to muscles or glands in response to an impulse. Communicate with and connect other neurons.

Understanding Neurons The Three Main Parts of a Neuron Cell BodyDendritesAxons

Understanding Neurons The cell body of a neuron contains the nucleus, which regulates the production of proteins within the cell.

Understanding Neurons Dendrites are branched structures that extend from the cell body in most neurons. Dendrites receive information and transmit impulses toward the cell body.

Understanding Neurons Axons transmit impulses away from the cell body and toward another neuron, muscle cell, or gland.

Understanding Neurons A nerve impulse begins when a sensory receptor is stimulated. The impulse travels to the CNS and is interpreted with the help of an interneuron. Then an impulse is sent to a muscle cell or gland in response to the stimulus.

The Central Nervous System The central nervous system is made up of the brain and spinal cord. The brain and spinal cord send and receive impulses to and from nerves in the body.

Sections of the Brain The brain coordinates and controls the activities of the nervous system. Your brain helps you to receive and process messages; to think, remember, reason, and feel emotions; and to coordinate muscle movements.

Sections of the Brain Three Main Divisions of the Brain The Cerebrum The Cerebellum The Brain Stem

The Cerebrum Billions of neurons in the cerebrum are the center of conscious thought, learning, and memory. cerebrum The largest and most complex part of the brain

The Cerebrum The cerebrum’s right and left sides, or hemispheres, communicate with each other to coordinate movement. The right hemisphere controls the left side of the body, and the left hemisphere controls the right side of the body.

The Cerebrum The center of language, reasoning, and critical thinking skills. The center for processing music and art and comprehending spatial relationships. Left Hemisphere Right Hemisphere

The Cerebrum Each hemisphere of the brain has four lobes. The Frontal Lobe The Parietal Lobe The Occipital Lobe The Temporal Lobe Controls voluntary movements and has a role in use of language. Possibly involved with intellect and personality. Involved with sensory information, including feelings of heat, cold, pain, touch, and body position in space. Controls the sense of sight. Contains the sense of hearing and smell, as well as memory, thought, and judgment.

The Cerebellum The cerebellum coordinates the movement of skeletal muscles and maintains the body’s posture and balance. Cerebellum The second largest part of the brain

The Brain Stem Incoming sensory impulses and outgoing motor impulses pass through the brain stem. Brain stem A 3-inch-long stalk of nerve cells and fibers that connects the spinal cord to the rest of the brain

The Brain

The Brain Stem Parts of the Brain Stem The medulla oblongata Regulates heartbeat, respiratory rate, and reflexes such as coughing and sneezing. The pons The midbrain The thalamus The hypothalamus Helps regulate breathing and controls the muscles of the eyes and face. Controls eyeball movement, pupil size, and the reflexive response of turning your head. Relays incoming sensory impulses from the eyes, the ears, and from pressure receptors in the skin. Regulates body temperature, appetite, sleep, and controls secretions from the pituitary gland.

The Peripheral Nervous System The peripheral nervous system is made up of the nerves that are not in the brain and spinal cord. The PNS carries messages between the CNS and part of the body, signaling internal and external changes.

The Peripheral Nervous System The PNS is made up of: the autonomic nervous system the somatic nervous system

The Autonomic Nervous System The autonomic nervous system controls such involuntary functions as digestion and heart rate.

The Autonomic Nervous System The autonomic nervous system consists of a network of nerves divided into two smaller networks: the sympathetic nervous system the parasympathetic nervous system

The Autonomic Nervous System The sympathetic nervous system causes a reflex when you are startled, sending messages that cause your heart rate to increase. Blood vessels in your muscles dilate, allowing greater blood flow and preparing you to react in a dangerous situation.

The Autonomic Nervous System A reflex is the body’s spontaneous response to a stimulus. Reflexes can prevent injuries such as a burn from a hot stove.

The Autonomic Nervous System How Your Reflexes Work

The Autonomic Nervous System The parasympathetic nervous system slows body functions during periods of rest to conserve energy. It also stimulates production of saliva and stomach secretions to promote the digestion of food.

The Somatic Nervous System The somatic nervous system involves voluntary responses that are under your control. Sensory neurons relay messages from the eyes, ears, nose, tongue, and skin to the CNS, and motor neurons carry impulses from the CNS to skeletal muscles.

Caring for Your Nervous System Making healthful choices can protect your nervous system from injury. Making healthful choices keeps a nervous system functioning properly.

Caring for Your Nervous System Eat a well-balanced diet Exercise regularly Get enough sleep Wear a safety belt when in a motor vehicle. Never dive into shallow water Wear a helmet and other protective gear while riding a bicycle, motorcycle, or other open vehicle, or when enjoying a contact sport. Do not use drugs and alcohol, which can permanently damage nerve cells.       

Problems of the Nervous System Injury to the nervous system affects the immediate tissues, and may lead to other problems, including: Headaches Head Injuries Spinal Injuries Meningitis

Problems of the Nervous System Headaches can be caused by muscle tension, eyestrain, exposure to fumes, a sinus infection, dehydration, or food allergies. Migraines are recurrent headaches that may be accompanied by sensitivity to light.

Problems of the Nervous System Each year, 435,000 American children and teens sustain brain injuries. ConcussionContusionComa a temporary loss of consciousness a bruising of the brain tissues that causes swelling caused by major trauma

Problems of the Nervous System Spinal cord injuries require medical care. Swelling of the spinal cord or the tissue around it can result in temporary loss of nerve function. If the spinal cord is severed, paralysis results.

Problems of the Nervous System Meningitis is an inflammation of the spinal and cranial meninges caused by bacterial or viral infection. Meningitis is very serious and can result in death.

Problems of the Nervous System Degenerative nervous system diseases occur over time as cells break down. Multiple Sclerosis Parkinson’s Disease Alzheimer’s

Problems of the Nervous System Causes of epilepsy include brain damage at birth, infections, head injury, or exposure to toxins. Epilepsy A disorder of the nervous system that is characterized by recurrent seizures— sudden episodes of uncontrolled electrical activity in the brain

Problems of the Nervous System Physical therapy and medication help patients cope with cerebral palsy. Cerebral palsy A group of neurological disorders that are the result of damage to the brain before, during, or just after birth or in early childhood

After You Read Reviewing Facts and Vocabulary The nucleus is located in the cell body. 1.Where is the nucleus of a neuron located?

After You Read Reviewing Facts and Vocabulary 2.How can a reflex prevent injury? A reflex is a spontaneous response of the body to a stimulus. Reflexes allow a person to respond to and avoid danger.

After You Read Reviewing Facts and Vocabulary 3.What are some causes of nervous diseases and disorders? Some diseases of the nervous system are degenerative, while others may result from head injury or neurological problems.