Peripheral Nervous System Flashcards
What is the PNS?
Peripheral nervous system contains nerves that originate in the brain and spinal cord but end peripherally.
Consists of motor, sensory, and autonomic neurons that innervate end-organs That include sensory receptors, muscles, and glands
T or F: The PNS consists 8 cranial nerves and 20 pairs of spinal nerves and all associated with ganglia and sensory receptors
False: the PNS consists of 12 cranial nerves and 31 pairs of spinal nerves and all associate with ganglia and sensory receptors
Where do sensory nervers originate?
Dorsal root ganglia
where do motor nerves originate?
Anterior horn of the spinal cord
What is the autonomic system divided into?
Sympathetic and parasympathetic nerves.
Where do the sympathetic nerves originate ?
Lateral horn of the thoracic spinal cord
Where do the parasympathetic nerves originate?
From the lateral gray matter of the sacral level of the spinal cord and from the brain stem itself
How are peripheral nerves typically classified?
By axon diameter and speed of conduction
List teh Sensory End-organ Receptors.
- Thermoreceptors
- Nociceptors
- Mechanoreceptors: Merkel’s disc, Ruffini’s corpuscle, Pacinian corpuscle, muscle spindle, free nerve endings, Golgi tendon organ (GTO)
- Chemoreceptors
- Photoreceptors
Axon
Projection of a nerve AWAY from the cell body that conducts impulses
Dendrite
An extension of the cell body that receives signals from other neurons
Endoneurium
Innermost covering of a peripheral nerve that surrounds each individual axon
Epineurium
Outermost covering of a peripheral nerve that surrounds the entire nerve and provides a buffer for the peripheral nerve
Motor unit
Single motor neuron and all of the muscle fibers that it innervates
Myelin
Proteins and lipids that form to crate a sheath around particular nerves; increases conductivity of the nerve impulse
