The Nervous System The Nervous System 1 Two

The Nervous System

The Nervous System • 1. Two main divisions • a. Central Nervous System (CNS) – consists of brain and spinal cord • b. Peripheral Nervous System (PNS) – includes nerves extending from brain and spinal cord • c. The CNS receives messages from the PNS, interprets them, and then sends out a response.

Neurons • 2. Neurons - nerve cells that transmit messages to and from the spinal cord and brain • a. Sensory Neurons – carry messages FROM body TO CNS • ex. Playing games in computer lab. When light switches to green, a sensory neuron transmits a message from your eye to your brain

Neurons • b. Motor Neurons – carry message TO body FROM CNS • ex. Your brain sends a signal through a motor neuron to tell your finger to click the mouse. • c. Interneurons – connect neurons

3. Structure and Functions of Neurons • 1. Dendrites – receive information and transmit impulses toward cell body • 2. Cell Body – large area which contains cell nucleus or power plant • 3. Axon – transmit impulses away from cell body and toward axon terminal • 4. Axon Terminals – branched structures at the ends of neurons. • 6. Myelin Sheath – insulating coat which covers the axon. This helps messages relay faster.

Neuron

The Central Nervous System • 1. The brain • a. Helps you think, remember, reason, feel emotion, and coordinate muscle movement • b. Divided into three main parts: cerebrum, cerebellum, brain stem

The Central Nervous System • 2. The Cerebrum • a. largest, most complex part of brain • b. right and left sides communicate with each other to coordinate movement. Right controls left side and vice versa. • c. left hemisphere is for language, reasoning, and critical thinking • d. right hemisphere is for spatial relationships

The Central Nervous System • 3. Four lobes (parts) of the cerebrum • a. Frontal Lobe – controls voluntary movements and use of language • b. Parietal Lobe – sensory information, including feelings of heat, cold, pain, touch, and body position in space • c. Occipital Lobe – Controls sense of sight • d. Temporal – sense of hearing and smell

Lobes of the Brain

The Central Nervous System • 4. The Cerebellum • a. second largest part of brain • b. maintains body’s posture and balance • c. coordinates complex muscle movements like serving a volleyball or playing violin

The Central Nervous System • 5. The Brain Stem • a. 3 inch long stalk of nerve cells that connect the spinal cord to the rest of the brain

The Central Nervous System • b. five parts • c. Medulla Oblongata – regulates heartbeat, breathing rate • d. Pons – regulates breathing and controls muscles of eye and face. • e. Midbrain – controls pupil size and reflexive response of turning your head • f. Thalamus – relays incoming information from the eyes, ears, and pressure receptors in skin • g. Hypothalamus – regulates body temp, appetite, sleep

The Peripheral System • 1. Broken into two parts • a. Autonomic Nervous System – controls involuntary functions such as digestion and heart rate • - you cannot control this; it is automatic! (autonomic) b. Somatic Nervous System – voluntary responses that are under your control • feeling and itch on your skin and scratching it

The Peripheral System • 2. Autonomic Nervous System • a. Broken down into two smaller networks • b. Sympathetic nervous system – kicks in when you are startled. Messages are sent that increase your heart rate. Also, blood vessels dilate to allow for greater blood flow. • - “Fight or flight response” • - Example… you are riding in a car and a deer jumps out in front of you. Think about how you feel. Your body prepares you to make a sudden reaction.

The Peripheral System • c. Parasympathetic nervous system – opposite of sympathetic nervous system • - slows heartbeat, relaxes blood vessels, lowers blood pressure

Problems of the Nervous System • 1. Headaches – caused by muscle tension, eyestrain, sinus infection, dehydration, or food allergies • 2. Head injuries • a. concussion – a temporary loss of consciousness • b. contusion – bruising of brain tissue that causes swelling

Problems of the Nervous System • 3. Spinal Injuries • a. swelling of spinal cord tissue can result in temporary loss of nerve function • b. if spinal cord is severed, you may become paralyzed.

Problems of the Nervous System • 4. Meningitis – inflammation of the spinal and cranial meninges caused by a virus or bacteria • a. symptoms include fever, headache, light and sound sensitivity, and neck stiffness. • b. can result in death

How to care for/prevent these problems: • 1. Eat a well-balanced diet, exercise regularly, get lots of sleep! • 2. Wear protective devices – helmet, seat belt • 3. Stay away from drugs and alcohol!!!