THE NERVOUS SYSTEM Schaefer Hedgepeth

Divisions of the Nervous System Central Nervous System Peripheral Nervous System Somatic Nervous System Autonomic Nervous System

Central Nervous System (CNS) Composed of brain and spinal cord, which are protected by the skull and vertebrae and insulated by fluids and tissue

Peripheral Nervous System (PNS) Contains the nerves that connect the brain and spinal cord to the rest of the body. Two divisions of PNS pathways: Sensory pathways (afferent): give input from body to the Central Nervous System Motor pathways (efferent): carry signals from the Central Nervous System to the muscles and glands

Somatic Nervous System (SNS) The part of the nervous system that controls the muscle system and external sensory receptors External sense organs are receptors, ex. Skin Effectors are the muscle fibers and glands

Somatic Nervous System (SNS) The sensory input obtained from the Somatic Nervous System is processed by the Central Nervous System, which then sends responses via the Peripheral Nervous System to the body’s organs. Reaction to stimulus is involuntary and automatic, and it can’t be inhibited

Autonomic Nervous System Controls internal organs Two divisions of the Autonomic Nervous System: Sympathetic Nervous System controls the fight or flight response Parasympathetic Nervous System controls relaxation These two work to reverse each other, for example the Sympathetic Nervous System causes your heart to beat faster in a dangerous situation and the Parasympathetic Nervous System reverses the effect.

Organs of the Nervous System Brain Purpose: The brain is the control center for everything that happens in the body. Spinal cord Purpose: The spinal cord links the brain to the rest of the body and is involved in reflexes that don’t travel immediately to the brain. Neurons and glial cells Purpose: Neurons transmit messages around the brain and glial cells surround neurons.

The Brain The key to taking over the human race because it is the organ in charge of everything. It is the organ that makes people human and who they are. It is made of 100 billion nerve cells called neurons. Neurons make up the brain’s “gray matter” and dendrites and axons make up the brain’s “white matter” (we will talk about this more later)

Divisions of the Brain Cerebrum Largest part More developed in humans than any other animal, which makes people more intelligent and smarter than animals. Divided into two hemispheres, which are further divided into four lobes in each hemisphere. Frontal lobes Involved in speech, thought, learning, emotion and movement Parietal lobes Process sensory information including touch, temperature, and pain Occipital lobes Deal with vision Temporal lobes Involved in hearing and memory

Divisions of the Brain Cerebellum Coordinates muscle movement and balance Transmits information to spinal cord and other parts of the brain Thalamus Incoming nerve impulses are sent to the thalamus, and are then sent to the appropriate region of the brain for processing Hypothalamus Controls hormone secretions from pituitary gland Hormones of the pituitary gland control growth and instincts, such as eating and drinking, sex, anger, and reproduction Brain Stem Controls reflexes, heart rate, breathing, and blood pressure

Spinal Cord Runs along the dorsal side of the body Protected by bony vertebrae It is also composed of gray and white matter. It sends messages from the body to the brain and vice versa.

Neurons and Glial Cells Neurons are made of three parts. Axon sends messages away from the cell body. Surrounded by myelin sheaths. Dendrites receive info from other cells and give it to the cell body. Cell body contains all the organelles of the cell. Glial cells are the cells that surround neurons. Their function is to support and protect the neurons.

How does it all work? The spaces between nerve cells are called synapses. Neurotransmitters are stored at the tip of each axon and are released when a message must be sent. The neurotransmitters are released across the synaptic clefts to stimulate the next neuron.

How does it all work? Messages are received from the sensory receptors, such as the skin, blood pH, or hormones. The messages are sent to the brain or spinal cord. The messages are processed and the body responds with an action, such as movement or change in heart rate.

Homeostasis The nervous system is essential in maintaining homeostasis because the body is constantly sending information to the brain and spinal cord and adjusting accordingly from the information that travels through the nervous system.

Works Cited human-body/human-body/brain-article.html human-body/human-body/brain-article.html kNERV.html kNERV.html 9.htm 9.htm “For a passing reference to a website in text, the URL is sufficient; no reference list entry is needed.”