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Lab 06: Muscle and Nervous Tissue
Muscles Nerves Muscles Nerves
58
Anatomy
Undergraduate 1
09/26/2010

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Term
Central Nervous System
Definition
The brain and the spinal cord make up the central nervous system.
Term
Peripheral Nervous System
Definition
The nerves that connect and the brain and spinal cord with sensory receptors, muscles and glands.
Term
Sensory, Afferent Fiber
Definition
the nerve impulses travel from the periphery to the central nervous system
Term
Motor, efferent fibers
Definition
From the central nervous system to the periphery
Term
The motor (efferent fiber) is divided in two groups
Definition
Somatic, Autonomic
Term
Somatic
Definition
innervates the skeletal muscles, and is under voluntary, conscious control
Term
Autonomic
Definition
innervates smooth muscle, the heart (cardiac muscle) and glands - it is involuntary
Term
The Autonomic Nervous system is divided in three
Definition
sympathetic, parasympathetic and enteric
Term
The enteric division
Definition
consists of neurons found in the gut, and in some ways can be regarded as an extension of the parasympathetic division.
Term
Neuroglia
Definition
Out number neurons by 9 to 1 and make up 50% of the volume of the brain. Once thought as "support" cells for neurons.
Term
Neuroglia: Astrocytes
Definition
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.
Term
Neuroglia: Oligodendrocytes
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.
Term
Neuroglia: Microglia
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.
Term
Neuroglia: Ependyma
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.
Term
Sensory Neurons
Definition
neurons that are involved in conveying sensory information to the CNS
Term
Interneurons
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.
Term
Motor neurons
Definition
neurons that convey motor commands, usually to skeletal muscles
Term
Neurons: cell body
Definition
Neurons contain neurofibils and Nissl bodies or granules. The latter are modified rough endoplasmic reticulum and function in protein synthesis.
Term
Neurons: Dendrites
Definition
short and highly branched. Function is to conduct nerve impulses toward the cell body.
Term
Neuron: Axon
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.
Term
Collaterals
Axon terminals
Synaptic end bulbs
Presynaptic terminals
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
Term
Synapse
Definition
The specialized structure formed at the point of close contact between the presynaptic terminal and the plasma membrane of the receiving cell
Term
Axoplasmic flow
Definition
A slow process which is responsible for carrying soluble proteins synthesized in the cell body down to the axon terminals
Term
Axon transport
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
Term
Retrograde axonal transport
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.
Term
Nueromascular junction
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.
Term
Motor end plate
Definition
At the neuromuscular junction the plasma membrane of the receiving muscle fiber is modified to form the motor
Term
Acetylcholine
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.
Term
Cholinesterase
Definition
Destroys the acetylcholine stoping its action. The advantage is that the neuromusclular junction is rapidly readied for the next nerve impulse to arrive
Term
Th motor neurons
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.
Term
Motor Unit
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.
Term
Motor recruitment
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.
Term
The all-or-none phenomenon
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
Term
Grading the contraction of the whole muscle
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.
Term
Tetanus
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
Term
Muscle spindles
Definition
located within the body of the muscle provide data the changing length of muscle during contraction or when it is stretched.
Term
Golgi tendon organs
Definition
located in the tendons provide data on the tension bend developed by the muscle.
Term
Spinal Nerves
Cranial Nerves
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
Term
The spinal cord
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
Term
Cervical enlargement
Definition
gives rise to nerves for the arms
Term
The dorsal root ganglion
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.
Term
The ventral root (or motor root)
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.
Term
Intervertebral foramen
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
Term
Anterior (ventral) median fissure
Posterior (dorsal) median sulcus
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.
Term
Spinal cord: gray matter
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.
Term
Propriospinal neurons
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.
Term
White matter
Definition
Consists of myelinated nerve fibers and is divided by the gray matter into anterior (ventral), posterior (dorsal), and lateral funiculi
Term
Function of Spinal Cord: Organization of Neurons
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.
Term
Function of the Spinal cord: Nerve Fiber Tracts
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.
Term
A spinal reflex
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.
Term
Spinal Reflex
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
Term
Spinal Reflex: A sensory receptor
Definition
Function to sense some change in either the internal or external environment.
Term
Spinal Reflex: A sensory neuron
Definition
Attached to the sensory receptor; the nerve impulse is passed from the receptor along this to the spinal cord.
Term
Spinal Reflex: An interneuron
Definition
which may be either inhibitory or excitatory
Term
Spinal Reflex: The motor neuron
Definition
Receives input from the interneuron and then conveys an impulse to the effector organ (away from the spinal cord)
Term
Spinal Reflex: The effector
Definition
is outside the nervous system
Term
Withdrawal reflex
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.
Term
Spinal shock
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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