Biology Chapter 29 Nervous System

Central Nervous System

The central nervous system (CNS) is made up of the brain, the spinal cord, and the optic nerves. The central nervous system controls thought processes, guides movement, and registers sensations throughout the body. Basically it controls the enter body

Peripheral Nervous System

The peripheral nervous system (PNS) is the other of the two major divisions of the nervous system. Nerves in the PNS connect the central nervous system with sensory organs, other organs, muscles, blood vessels, and glands. Essentially serving as a communication relay going back and forth between the brain and spinal cord with the rest of the body.

Somatic Nervous System

The Somatic Nervous System (SoNS) is the part of the peripheral nervous system associated with skeletal muscle voluntary control of body movements. The SoNS consists of afferent nerves or sensory nerves, and efferent nerves or motor nerves. It controls voluntary actions.

Somatic is voluntary actions

Autonomic Nervous System

The Autonomic Nervous System is the part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, the heartbeat, and digestive processes. It is divided into the sympathetic and parasympathetic. Essentially the Autonomic Nervous System controls involuntary actions.

Parasympathetic Nervous System

Sometimes called the rest and digest system, the parasympathetic system conserves energy as it slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles in the gastrointestinal tract.

Sympathetic Nervous System

The sympathetic nervous system activates what is often termed the fight or flight response. Like other parts of the nervous system, the sympathetic nervous system operates through a series of interconnected neurons. Sympathetic neurons are frequently considered part of the peripheral nervous system (PNS), although there are many that lie within the central nervous system (CNS).

Sensory Neuron

Sensory neurons are nerve cells within the nervous system responsible for converting external stimuli from the organism's environment into internal electrical impulses. For example, some sensory neurons respond to tactile stimuli and can activate motor neurons in order to achieve muscle contraction.

Interneuron

Interneurons (also known as association neurons) are neurons that are found exclusively in the central nervous system. That means that they are found in the brain and spinal cord and not in the peripheral segments of the nervous system. There are more than 100 billion interneurons in the human body, which makes them the most abundant of the three major neuron types (along with sensory and motor neurons). Interneurons serve as the connection point between sensory and motor neurons.

Motor Neuron

In vertebrates, motor neurons (also called motoneurons) are efferent neurons that originate in the spinal cord and synapse with muscle fibers to facilitate muscle contraction and with muscle spindles to modify proprioceptive sensitivity. Controls body movement

Neuromuscular Junction

A neuromuscular junction (or myoneural junction) is a chemical synapse formed by the contact between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction.

Acetylcholine

Acetylcholine is the neurotransmitter at neuromuscular junctions, at synapses in the ganglia of the visceral motor system, and at a variety of sites within the central nervous system. Acetylcholine in the peripheral nervous system (PNS) Acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system.

Norepinephrine

Norepinephrine is a naturally occurring chemical in the body that acts as both a stress hormone and neurotransmitter. It's released into the blood as a stress hormone when the brain perceives that a stressful event has occurred. As part of the body's response to stress, norepinephrine affects the way the brain pays attention and responds to events.

Epinephrine

Epinephrine, also called adrenaline, hormone that is secreted mainly by the medulla of the adrenal glands and that functions primarily to increase cardiac output and to raise glucose levels in the blood. Epinephrine typically is released during acute stress, and its stimulatory effects fortify and prepare an individual for either “fight or flight”

Synapse

Neurons communicate with one another at junctions called synapses. At a synapse, one neuron sends a message to a target neuron—another cell. Most synapses are chemical; these synapses communicate using chemical messengers. Other synapses are electrical; in these synapses, ions flow directly between cells. At a chemical synapse, an action potential triggers the presynaptic neuron to release neurotransmitters. These molecules bind to receptors on the postsynaptic cell and make it more or less likely to fire an action potential.

White Matter

White matter is found in the deeper tissues of the brain. It contains nerve fibers (axons), which are extensions of nerve cells (neurons). Many of these nerve fibers are surrounded by a type of sheath or covering called myelin. Myelin gives the white matter its color. It also protects the nerve fibers from injury and improves the speed and transmission of electrical nerve signals.

Gray Matter

The grey matter is mainly composed of neuronal cell bodies and unmyelinated axons. Axons are the processes that extend from neuronal cell bodies, carrying signals between those bodies. In the grey matter, these axons are mainly unmyelinated, meaning they are not covered by a whitish-colored, fatty protein called myelin. The grey matter serves to process information in the brain. Structures within the grey matter process signals generated in the sensory organs or other areas of the grey matter.

Cerebral cortex

The Cerebral Cortex is made up of tightly packed neurons and is the wrinkly, outermost layer that surrounds the brain. It is also responsible for higher thought processes including speech and decision making . The cortex is divided into four different lobes, the frontal, parietal, temporal, and occipital, which are each responsible for processing different types of sensory information.

Frontal Lobe

You use your frontal lobe nearly everyday. You use it to make decisions, such as what to eat or drink for breakfast in the morning, as well as for thinking or studying for a test. The frontal lobe is also where our personality is formed and where we can carry out higher mental processes such as planning. In addition, the frontal lobe is necessary to being able to speak fluently (without fault) and meaningfully.

Parietal Lobe

The parietal lobe carries out some very specific functions. As a part of the cortex, it has a lot of responsibilities and has to be able to process sensory information within seconds. The parietal lobe is where information such as taste, temperature and touch are integrated, or processed. Humans would not be able to to feel sensations of touch, if the parietal lobe was damaged.

Temporal Lobe

The Temporal Lobe mainly revolves around hearing and selective listening. It receives sensory information such as sounds and speech from the ears. It is also key to being able to comprehend, or understand meaningful speech. In fact, we would not be able to understand someone talking to us, if it wasn't for the temporal lobe. This lobe is special because it makes sense of the all the different sounds and pitches being transmitted from the sensory receptors of the ears.

Occipital Lobe

The occiptial lobe is important to being able to correctly understand what your eyes are seeing. These lobes have to be very fast to process the rapid information that our eyes are sending. The occipital lobe makes sense of visual information so that we are able to understand it. If our occipital lobe was impaired, or injured we would not be able to correctly process visual signals, thus visual confusion would result.

Limbic System

The limbic system is a complex set of structures that lies on both sides of the thalamus, just under the cerebrum. It includes the hypothalamus, the hippocampus, the amygdala, and several other nearby areas. It appears to be primarily responsible for our emotional life, and has a lot to do with the formation of memories.

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