Nervous System The nervous system maintains homeostasis by controlling and regulating all other parts of the body. REGULATION

Functions of the Nervous System 1.Sensory-uses receptors to gather information from all over the body 2. Interpretation-the brain then processes the information into possible responses 3. Response-sends messages back through the system of nerve cells to control body parts

Evolutionary Trends of the Nervous System Simple Complex

Structures of the Nervous System Neurons: the functional cell that transmits signals through the body; an individual nerve cell Parts of a Neuron 1.cell body- the largest part of the neuron; contains the nucleus and organelles 2. dendrites- short, branching extensions spreading out from the cell body; receive and carry impulses to the cell body 3. axon- long, fibrous part of neuron; conducts nerve impulses away from cell body 4. at the end of the axon, the impulse travels across the synapse, a tiny gap separating the axon of one neuron from the dendrite of another

Neuron Nerve Impulse- an electrical signal is sent from the dendrite, along the axon, to the terminal. A chemical message, called a neurotransmitter is released from the axon terminals into the synapse, where it travels to the next cell.

Types of Neurons a. sensory neurons- carry impulses from sense organs to brain b. motor neurons- carry impulses from brain/spinal cord to muscles/organs c. interneurons- carry impulses between sensory and motor neurons

Divisions of the Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS)

Central Nervous System (CNS) A.Brain- “control center”- receives and analyzes information; processes and sends back instructions

Parts of the Brain 1. Cerebrum controls thought, language, learning, judgment, & voluntary action 2. Cerebellum controls involuntary functions of muscles & maintains balance and posture 3. Brain stem Controls involuntary functions such as breathing, heart rate, and swallowing 4. Thalamus, Hypothalamus Controls homeostasis- temperature, hunger, thirst, fight or flight responses

Spinal cord- link between the brain and PNS; also controls reflexes Reflex: a simple, automatic response (ex. Hand on a tack)

Peripheral Nervous System (PNS) A.Consists of nerves- ropelike bundles of neurons B.Gathers information, delivers it to and from CNS

Levels of Organization Nerves Brain Nervous Neurons

Interaction with other systems for Regulation  Bones of the skeletal system protect the spinal cord and brain.  The brain controls heart rate, blood pressure, and breathing via the circulatory and respiratory systems.  Glands in the brain control the release of hormones of the endocrine and reproductive systems.  The brain controls muscles both in digestion and movement.

Diseases / Disorders of the Nervous System 1.Polio- a virus that attacks the spinal cord; eventually causes paralysis 2.Multiple Sclerosis (MS)- affects neurons; slows nerve impulses, causing muscle weakness, possibly paralysis. 3.Alzheimer’s- brain tissue deteriorates; severe memory loss 4.Stroke- a blockage in a blood vessel in the brain, causing brain damage 5.Concussion- a bruise to the brain when the brain hits the inside of the skull

Fun Facts  A human body contains more nerve cells than there are stars in the Milky Way  Neurons are the largest cell in the body and do NOT undergo mitosis  Nerve impulses move at 100 meters per second or more  Longest axon of a neuron is 15 ft! (in the giraffe)