The Nervous System
This complex network of systems has helped us in all aspects of survival. It is comprised of two main parts: the central nervous system and the peripheral nervous system. This body system helps us perform extraordinary feats like storing and utilizing unlimited information, controlling homeostasis, and coordinating the most precise movements.
The CNS
The central nervous system is comprised of the brain and the spinal cord, and its main function is to control all bodily functions, voluntary and autonomic. The spinal cord is a long is a long line of vertebra that extends from the brain stem to the first lumbar vertebra. Its job is to send signals from the brain to the body and vice versa in response to stimuli. For more information about the brain, check out the next page!
The PNS
The peripheral nervous system is comprised of the rest of all the nerves, sensory organs, and receptors scattered throughout the rest of the body. It connects the limbs, organs, and all other parts of the body to the central nervous system.
Divisions of the PNS: Somatic and Autonomic
The PNS is divided into the somatic nervous system, which controls voluntary activities like the skeletal muscles, and the autonomic nervous system, which controls involuntary actions like breathing, heart beat, and digestion.
Divisions of the Autonomic Nervous System: Sympathetic and Parasympathetic
The ANS is composed of the sympathetic and parasympathetic nervous system. The sympathetic nervous system is what controls our bodies under stress. It signals the fight or flight mode and prepares our bodies for intense action by altering several things such as faster heart rate to pump more blood to the muscles, dilated pupils to see from a distance, increased sweating to cool down the body, and a variety of other actions. The parasympathetic nervous system is in charge of the body during times of rest and relaxation like digestion and sleeping.
Divisions of the PNS: Somatic and Autonomic
The PNS is divided into the somatic nervous system, which controls voluntary activities like the skeletal muscles, and the autonomic nervous system, which controls involuntary actions like breathing, heart beat, and digestion.
Divisions of the Autonomic Nervous System: Sympathetic and Parasympathetic
The ANS is composed of the sympathetic and parasympathetic nervous system. The sympathetic nervous system is what controls our bodies under stress. It signals the fight or flight mode and prepares our bodies for intense action by altering several things such as faster heart rate to pump more blood to the muscles, dilated pupils to see from a distance, increased sweating to cool down the body, and a variety of other actions. The parasympathetic nervous system is in charge of the body during times of rest and relaxation like digestion and sleeping.
The Neuron
The brain contains a vast network of neurons that help it perform its amazing job of conducting all the functions of the body and processing information to implement the perfect response. From the cold weather to intense pain, these spidery-looking neurons send all kinds of information from all over the body to the brain.
Firing an Impulse
Neurons receive information from the rest of the body and pass it on to other neurons through an electrical impulse called the action potential. An impulse starts in the cell body, or soma, and makes its way down the axon where the membrane depolarizes. Sodium ions enter the cell, and as the impulse reaches the axon terminal or the synapse, calcium ions signal synaptic vesicles to bind to the membrane and release neurotransmitters (chemicals that control different bodily functions) into the synaptic cleft (space between the sending cell's axon and the receiving cell's dendrite). These neurotransmitters are received by protein receptors on the next cell and fires the neuron to send the signal or inhibits it. This process is called synaptic transmission. Afterwards, the neurotransmitters are sucked back into the vesicles by transporters for further use in a process called reuptake. Other neurotransmitters are broken down by enzymes, so that they don't stay in the synaptic cleft..
Synaptic Action
Fun Facts
- There are more nerve cells in the body than there are stars in the Milky Way.
- The brain contains about 100 billion neurons, which, when lined up, would be 600 miles long.
- Babies growing in a womb can grow neurons at a rate of 250,000 per minute.
- There are 43 different pairs of nerves that connect the brain (12 pairs) and spinal cord (31 pairs) to the rest of the body.
- As we grow older, the brain loses a gram each year.
- Neurons are the largest cells in the human body. Unfortunately, they do not reproduce like other cells (mitosis).
- The nervous system works very rapidly and can send signals at a rate of 180 mph within the body.
- The brain contains about 100 billion neurons, which, when lined up, would be 600 miles long.
- Babies growing in a womb can grow neurons at a rate of 250,000 per minute.
- There are 43 different pairs of nerves that connect the brain (12 pairs) and spinal cord (31 pairs) to the rest of the body.
- As we grow older, the brain loses a gram each year.
- Neurons are the largest cells in the human body. Unfortunately, they do not reproduce like other cells (mitosis).
- The nervous system works very rapidly and can send signals at a rate of 180 mph within the body.