Nervous System By: Zach Hardin

Nervous System Definition The Nervous System consist of the brain, spinal cord, sensory organs, and all the nerves that connect the organs to the rest of the body.

Functions of the Nervous System Sensory: This function of the system includes collecting information from sensory receptors that monitor the body’s internal and external condition. Integration: This is the function of processing many sensory signals that come through the CNS at a given time. Motor: This function happens once the CNS evaluates the sensory information and has decided on its action and how it will respond to the stimulus.

Divisions of the Nervous System Central Nervous System- the brain and spinal cord come together to form the CNS. The CNS acts as the control center for the body by providing its processing, memory, and regulation systems. The CNS monitor conscious and subconscious information. The CNS is also responsible for language, creativity, expressions, emotions, and personality. Peripheral Nervous System- this is all the parts of the nervous system outside the spine and brain. These parts of the PNS include spinal nerves, ganglia, and sensory receptors.

Somatic Nervous System- the SNS is a division of the PNS that includes all of the voluntary efferent neurons. This is the only consciously controlled part of the PNS. The SNS is also responsible for stimulating skeletal muscles. Autonomic Nervous System- the ANS is also a division of the PNS that include all involuntary efferent neurons. The ANS controls subconscious things such as visceral muscle tissue, cardiac muscle tissue, and glandular tissue.

The Nerve Definition: The nerve is a bundle of axons in the Peripheral Nervous System that acts like a information highway between the brain, spinal cord, and the rest of the body. Axons- extend from cell body and send messages to other neurons Dendrites- extend from the cell body and pick up signals from the environment

Types of Nerves Afferent Nerves- this is a nerve that carries information from the sensory receptors to the Central Nervous System. Efferent Nerves- this is a nerve that carries signals from the Central Nervous system to muscles and glands. Mixed Nerves- these contain both afferent and efferent axons and act as a two way street for signals. Cranial Nerves- these provide a direct connection to the brain for special sense organs. There are 12 pair of cranial nerves. They are identified by their location and function. Spinal Nerves- these are mixed nerves that extend from left to right. There are 31 pair of spinal nerves. These are split into groups: 8 pair of cervical nerves, 12 pair of thoracic nerves, 5 pair of lumbar nerves, 5 pair of sacral nerves, and 1 pair of coccygeal nerves.

The Neuron Neurons are cells that communicate with the body by transmitting electrical and chemical signals. A neuron is composed of a cell body with all the organelles.

Types of Neurons Afferent Neuron- (sensory neuron) transmits sensory signals to the Central Nervous System to the receptors in the body. Efferent Neuron- (motor neuron) transmits signals to muscles and glands in the body. Interneurons- combine the information received from the sensory neurons and sends the function to the motor neurons.

Neuroglia This is also known as a glial cell and the “helper” to the nervous system. Each neuron in the body is covered by 6-60 neuroglia cells. The glial cells help the neuron by protecting, feeding, and insulating. The glial cell is vital in maintaining a functional nervous system.

The Brain The brain is a soft wrinkled organ that weighs about three pounds. The brain is located inside the cranium where the bones of the skull surround and protect it. The brain and the spinal cord come together to form the Central Nervous System.

The Spinal Cord The spinal cord is a long, thin bundle of neurons that carry information through the vertebral cavity. The spine starts at the medulla oblongata and continues to the lumbar region of the spine. Cauda Equina- this is a bundle of nerves shaped like a horses tale located in the lumbar region of the spine and continuing to the coccyx.

Cerebrospinal Fluid The space surrounding the organs of the Central Nervous System is filled with a clear liquid know as Cerebrospinal Fluid. Choroid Plexuses- these help form cerebrospinal fluid from blood plasma.

Functions of Cerebrospinal Fluid. Absorb shock between the brain and the skull and between the spinal cord and vertebrae. The brain and spinal cord float in the fluid which reduces their weight. The reduction of weight allows the blood vessels of the brain to stay open and help the nervous tissue from crushing under its own weight. The cerebrospinal fluid helps maintain chemical homeostasis. It contains nutrients that support chemical balance of the nervous system. The cerebrospinal fluid also removes waste products from cellular metabolism.

Connection to other Systems The nervous system interacts with the skeletal, cardiovascular, muscular, endocrine, lymphatic, respiratory, digestive, reproductive, urinary, and integumentary system. Skeletal System- the bones of the skull protect the brain from injury. The vertebrae protect the spinal cord. Cardiovascular System- cerebrospinal fluid drains into the venous blood supply. The brain regulates heart rate and blood pressure.

Muscular System- receptors in the muscles allow the brain to know the position and movement of the body. Endocrine System- hormones allow information to the brain for neural processing. Reproductive hormones affect the development of the nervous system. Lymphatic System- the brain can stimulate the defense mechanisms to fight infection. Respiratory System- the brain monitors respiratory volume and blood gas levels. The brain regulates respiratory rate.

Digestive System- the autonomic nervous system controls the tone of the digestive tract. The brain controls drinking and eating behavior. The brain controls the muscles for eating. Reproductive System- reproductive hormones affect the brains development. Urinary System- the bladder sends sensory information to the brain. The brain controls urination. Integumentary System- receptors in the skin send sensory information to the brain. The autonomic nervous system regulates peripheral blood flow and sweat glands. Nerves control muscles connected to hair follicles.

Disease: Alzheimer’s This is a progressive, degenerative disease that occurs in the brain and results loss of memory, thinking, and behavior. This disease usually occurs in mid to old age people. This disease is the cause of neurons breaking connection with each other and eventually passing.

Fun Facts about the Nervous System There are more nerve cells in the human brain that there are stars in the Milky Way. If we were to line up all the neurons in our body, it would be around 600 miles long. There are 100 billion neurons in your brain alone. There are around 13.5 million neurons in the human spinal cord. The total surface area of the human brain is about 25,000 square cm. On average, you use only 4% of the cells in your brain at any one time.

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