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Definition
| The brain and the spinal cord make up the central nervous system. |
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Term
| Peripheral Nervous System |
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Definition
| The nerves that connect and the brain and spinal cord with sensory receptors, muscles and glands. |
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| the nerve impulses travel from the periphery to the central nervous system |
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| From the central nervous system to the periphery |
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| The motor (efferent fiber) is divided in two groups |
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Definition
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| innervates the skeletal muscles, and is under voluntary, conscious control |
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| innervates smooth muscle, the heart (cardiac muscle) and glands - it is involuntary |
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| The Autonomic Nervous system is divided in three |
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Definition
| sympathetic, parasympathetic and enteric |
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Definition
| consists of neurons found in the gut, and in some ways can be regarded as an extension of the parasympathetic division. |
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| Out number neurons by 9 to 1 and make up 50% of the volume of the brain. Once thought as "support" cells for neurons. |
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| Star-shaped cells found between neurons and blood vessels. Their processes cover nearly all the capillaries in the brain, and they also make contact with the surfaces of neurons. |
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Term
| Neuroglia: Oligodendrocytes |
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Definition
| Resemble astrocytes, but processes are fewer and shorter. They produce a phospholipid myelin sheath around axons of neurons in the CNS system. In the peripheral nervous system, this function is subserved by Schwann cells. |
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Definition
| The brain's microphages. They are small cells with few process. Like macrophages, they may originate from monocytes circulating in the blood. The phagocytize bacteria and cellular debris, and can migrate into an are of damaged nervous tissue. |
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Definition
| Like epithelial cells, they line the ventricles of the brain and the central canal in the spinal cord. The cells by by cuboidal or columnar, and may have cilia. |
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Definition
| neurons that are involved in conveying sensory information to the CNS |
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Definition
| Neutrons that convey information from one neuron to another neuron. In some parts of the central nervous system, inter neurons inhibit or stop other neurons from firing. Such interneurons are said to be inhibitory. |
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| neurons that convey motor commands, usually to skeletal muscles |
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| Neurons contain neurofibils and Nissl bodies or granules. The latter are modified rough endoplasmic reticulum and function in protein synthesis. |
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Definition
| short and highly branched. Function is to conduct nerve impulses toward the cell body. |
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Definition
| A long tubular process arising from the axon hillock on the cell body. The axon conducts nerve impulses away from the cell body to another neuron or muscle or gland cells. |
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Term
Collaterals
Axon terminals
Synaptic end bulbs
Presynaptic terminals |
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Definition
| Axons give off branches called collaterals, and their axon terminals have many specialized, bulb-like endings that are called synaptic end bulbs or presynaptic terminals. The presynaptic terminals are in close contact with the plasma membranes of other cells |
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Definition
| The specialized structure formed at the point of close contact between the presynaptic terminal and the plasma membrane of the receiving cell |
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Definition
| A slow process which is responsible for carrying soluble proteins synthesized in the cell body down to the axon terminals |
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Definition
a faster, ATP requiring process. This process is involved in the transport of organelles (such as synaptic vesicles, mitochondria) through the axon.
The transport occurs on the surfaces of micro- or nuerotubules, fine threads composed of special proteins that course inside the axon along its entire length |
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Term
| Retrograde axonal transport |
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Definition
the opposite of anterograde axonal transport, and can move particles toward the neural cell body.
Herpes, polio, rabies viruses can hitch a ride on this system, and make their way from the surface of the body via the axons of neurons into the cell bodies of the neurons themselves. |
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Term
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Definition
| Communication between skeletal muscle and neurons (motor neurons). Only one neuromascular junction is found per muscle fiber (=cell), although a single neuron may transmit signals via branching collaterals to many muscle fibers. |
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Term
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Definition
| At the neuromuscular junction the plasma membrane of the receiving muscle fiber is modified to form the motor |
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Term
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Definition
| When a nerve impulse arrives at the presynaptic terminal, the neurotransmitter acetycholine is released and diffuses to motor end plate, where it binds to acetylcholine receptors in the plasma membrane of the muscle. As a result, a wave of electrical depolarization spreads over the surface of the muscle fiber, causing the muscle fiber to contract. |
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Term
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Definition
| Destroys the acetylcholine stoping its action. The advantage is that the neuromusclular junction is rapidly readied for the next nerve impulse to arrive |
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Term
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Definition
| the cell bodies of motor neurons are located in the anterior horn of the spinal cord gray matter, and their axons emerge from the spinal cord and course along the spinal nerves. |
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Definition
A motor neuron and all the muscle fibers it is called a motor unit
Since each muscle has only one neuromuscular junction, it can only receive commands from one motor neuron. |
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Definition
| Increasing the number of motor neurons and therefore motor units, activated at any one time, can increase the force of contraction of the muscle. |
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Term
| The all-or-none phenomenon |
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Definition
| applies to single muscle fibers. A stimulus is either sufficient to cause a maximum contraction, or it is subthreshold and there is no contraction at al. Therefore, activation of a single motor neuron causes maximum contraction of all the muscle fibers in the motor unit |
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Term
| Grading the contraction of the whole muscle |
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Definition
| The muscle fibers in other motor units do not contract until their motor neurons are activated. In the whole muscle that many motor units, and therefore the force of contraction of the whole muscle can be graded by the altering the number of motor units activated. |
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Term
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Definition
| If a muscle is stimulated at high frequency, it does not have time to relax between twitches. Therefore, the individual twitches merge together. Under these conditions, there is a continuous tetanic contraction. This is called Tetanus |
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Term
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Definition
| located within the body of the muscle provide data the changing length of muscle during contraction or when it is stretched. |
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Term
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Definition
| located in the tendons provide data on the tension bend developed by the muscle. |
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Term
Spinal Nerves
Cranial Nerves |
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Definition
| The nerves from the spinal cord are called spinal nerves. The nerves that emerge from the brain are called the cranial nerves. Together they make up the peripheral nervous system |
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Term
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Definition
The spinal cord consists of 31 segment, each of which gives rise to a pair of spinal nerves.
Cervical - 8
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 1 |
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Definition
| gives rise to nerves for the arms |
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Definition
| contains the cell bodies of sensory neurons whose nerve endings are often specially adapted to act as sensory receptors. The axons of these sensory neurons enter the spinal cord through the dorsal root and for synapsis with other neurons in the spinal cord. |
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Term
| The ventral root (or motor root) |
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Definition
| is actually composed of a number of rootlets, and carries the axons of motor neurons whose cell bodies are located in the gray matter of the spinal cord. |
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Term
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Definition
| The dorsal and ventral roots merge to form a spinal nerve that emerges from the vertebral canal through an intervertebral foramen. After emerging from the foramen, the spinal nerve splits into an anterior and a posterior branch. The spinal nerves in the thoracic and lumbar regions also have rami (branches) that are part of the automatic nervous system |
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Term
Anterior (ventral) median fissure
Posterior (dorsal) median sulcus |
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Definition
| The spinal cord is partially divided into right and left halves by a deep anterior (ventral median fissure and a shallow posterior (dorsal) median sulcus. |
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Definition
| Consists of many cell bodies of neurons with their axons and dendrites, occupies the central region of the cord, and looks like a butterfly or an H in cross section. |
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Definition
| send axons in the lateral and ventral columns of the white matter for distances ranging from a few, to many segments up and down the spinal cord. |
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Term
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Definition
| Consists of myelinated nerve fibers and is divided by the gray matter into anterior (ventral), posterior (dorsal), and lateral funiculi |
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Term
| Function of Spinal Cord: Organization of Neurons |
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Definition
It is the major pathway of all information ascending to the brain from the sensory systems of the body and for all commands descending from the brain to the muscles and other effector systems.
There are two major ascending tracts conveying sensory information to the cerebellum. There are five major descending tracts carrying motor information to the spinal cord. |
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| Function of the Spinal cord: Nerve Fiber Tracts |
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Definition
| The spinal cord is able to execte certain simple behavioral activities without involving the brain. These activities are referred to as spinal reflexes. Also neural networks in the spinal cord are responsible for storing the motor program involved in walking. |
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Term
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Definition
| is a simple response to a stimulus, and it activates only neurons in the spinal cord. Spinal reflexes provide an important "background" against which voluntary movements take place and are important in posture. |
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Term
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Definition
| simple response to a stimulus, and it activates only neurons in the spinal cord. Spinal reflexes provide an important "background" against which voluntary movements take place and are important in posture |
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Term
| Spinal Reflex: A sensory receptor |
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Definition
| Function to sense some change in either the internal or external environment. |
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Term
| Spinal Reflex: A sensory neuron |
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Definition
| Attached to the sensory receptor; the nerve impulse is passed from the receptor along this to the spinal cord. |
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Term
| Spinal Reflex: An interneuron |
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Definition
| which may be either inhibitory or excitatory |
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Term
| Spinal Reflex: The motor neuron |
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Definition
| Receives input from the interneuron and then conveys an impulse to the effector organ (away from the spinal cord) |
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Term
| Spinal Reflex: The effector |
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Definition
| is outside the nervous system |
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Term
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Definition
| Occurs when one touches something painful. This involves the withdrawal of the entire hand and arm or leg and foot away from the painful stimulus. |
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Term
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Definition
| When the is cut at the level of the neck or thorax, all spinal reflexes are temporarily lost. The reason is that higher brain center normally modulate and facilitate spinal reflexes. When the descending nerve impulses from these higher facilitatory center are lost, the neurons of the spinal reflexes become temporarily insensitive, and fail to respond. During recovery, the spinal reflexes return, often in exaggerated form. |
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