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33 terms

The peripheral nervous system

Chapter 6
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Neurons
A nerve cell
- The basic structural and functional unit of the nervous system
Schwann Cells
Cell that wraps around a nerve fibre forming the myelin sheath
Nodes of Ranvier
A gap in the myelin sheath of a nerve fibre
Neurilemma
A sheath surrounding a nerve fibre
Sensory neurons
A nerve cell that carries messages from receptors to the brain or spinal cord
- AKA receptor neuron
Motor neurons
A nerve cell that carries messages from the brain or spinal cord to eff ector organs (muscles and glands)
- AKA effector neuron
Interneurons
A nerve cell in the brain or spinal cord that carries messages between other nerve cells
- AKA association neurons or connector neurons
Multipolar neurons
A nerve cell with one axon and many dendrites
- The most common type of neuron
Bipolar neurons
a neuron with two processes—one axon and one dendrite—arising from opposite sides of the cell body - These neurons are sensory, such as the neurons found in the retina of the eye
Unipolar neurons
A neuron with a single process, an axon
- The cell body is to one side of the axon
- In humans such neurons are sensory and carry messages to the spinal cord
Nerve fibres
An axon with its associated coverings
Nerves
A bundle of nerve fibres
Synapse
The junction between the branches of adjacent neurons
Neuromuscular junction
The junction between branches of a motor nerve cell and a muscle fibre
- AKA: the motor end plate
PNS
The part of the nervous system that connects the central nervous system with the receptors, muscles and glands
- Peripheral Nervous System
Ganglion
A group of nerve cell bodies outside the
brain and spinal cord
- Ganglia
Cranial nerves
One of the twelve pairs of nerves that arise from the brain
Spinal nerves
One of the 31 pairs of nerves that arise from the spinal cord
- Joined to the spinal cord by dorsal and ventral roots
Ventral root
One of the two roots that link a spinal nerve to the spinal cord
- Located towards the front of the body
- Contains axons of motor neurons
Dorsal root
One of the two roots that link a spinal nerve to the spinal cord
- Located towards the back of the body and contains axons of sensory neurons
Dorsal root ganglion
A group of nerve cell bodies located in the dorsal root of a spinal nerve
Somatic sensory neurons
A nerve cell that carries messages from receptors in the skin, muscles, bones and joints into the brain and spinal cord
Visceral sensory neurons
A neuron that takes impulses from the internal organs to the central nervous system
Nerve impulse
The electrochemical change that travels along the membrane of a nerve cell
- The message carried by a nerve
- (See also action potential)
Electrochemical change
The change in electrical voltage brought about by changes in the concentration of ions inside and outside the cell membrane of the neuron
Saltatory conduction
The conduction of a nerve impulse along a myelinated nerve fibre
- The impulse seems to jump from one node of Ranvier to the next
Reflex
A rapid, automatic response to a change in the
external or internal environment
- Tries to restore homeostasis
Spinal reflex
A reflex carried out by the spinal cord, without involvement of the brain
Reflex arc
The basic pathway travelled by nerve impulses from receptor to effector
Spinal reflex arc
The basic pathway travelled by nerve impulses from receptor to effector in the case of a spinal reflex
Receptor
A structure that detects a stimulus
Effector
A muscle or gland that carries out a response to a stimulus
Acquired reflexes
A reaction that has been learned as a result of the occurrence of a stimulus