PNS Flashcards
(31 cards)
What is the Peripheral Nervous System (PNS)?
The PNS is derived from neural crest cells and consists of cranial and spinal nerves and their ganglia.
What are the main components of cranial and spinal nerves?
They are composed of axons (nerve fibers) of neurons whose cell bodies are located within the CNS or in ganglia.
What are neurolemmocytes?
Neurolemmocytes, also known as Schwann cells, arise from neural crest and myelinate axons in the PNS.
What are the parts of a neuron?
A neuron consists of a cell body and processes, which include one axon and one or more dendrites.
Define a unipolar neuron.
A unipolar neuron has only one process, the axon, and all afferent neurons are unipolar.
What characterizes a pseudounipolar neuron?
A pseudounipolar neuron has two processes that arise separately, fuse briefly, and then divide into an axon and dendrite.
Describe a bipolar neuron.
A bipolar neuron has two processes: one axon and one dendrite.
What defines a multipolar neuron?
A multipolar neuron has three or more processes: one axon and two or more dendrites.
What are sensory or afferent neurons responsible for?
They conduct impulses from receptor organs to the CNS.
What do motor or efferent neurons do?
They conduct impulses from the CNS to target organs.
What is the role of association neurons (interneurons)?
They transfer sensory impulses from sensory neurons to efferent neurons.
What do somatic neurons innervate?
Somatic neurons innervate voluntary muscles and structures derived from ectoderm.
Define visceral neurons.
Visceral neurons innervate involuntary muscles and structures derived from splanchnopleure.
What constitutes the autonomic nervous system (ANS)?
The ANS consists of visceral efferent neurons and involves two motor neurons: preganglionic and postganglionic.
What is a nerve fiber?
A nerve fiber is an axon of a neuron and its sheath that connects peripheral structures with the brain or spinal cord.
How do spinal nerves connect to the spinal cord?
Spinal nerves connect via two roots: dorsal root for sensory fibers and ventral root for motor fibers.
What are the four functional types of spinal nerves?
- General Somatic Afferent (GSA)
- General Visceral Afferent (GVA)
- General Somatic Efferent (GSE)
- General Visceral Efferent (GVE)
What do GSA spinal nerves conduct?
They conduct impulses from receptor organs to the spinal cord.
What is the function of GVA spinal nerves?
They carry impulses from visceral organs to the spinal cord.
What do GSE spinal nerves do?
They conduct impulses from the spinal cord to skeletal muscles.
Describe the function of GVE spinal nerves.
They arise from a chain of two neurons between the spinal cord and target organs.
What is the role of the olfactory nerve (I)?
The olfactory nerve is sensory and arises from olfactory hair cells.
What is the function of the optic nerve (II)?
The optic nerve is sensory and arises from sensory neurons in the retina.
Which cranial nerve is responsible for eye movement?
The oculomotor nerve (III) controls eye movement.
