Organization of the Nervous System Flashcards
Two anatomical divisions of the nervous system
The nervous system is divided into two anatomical divisions: the central nervous system (CNS), which is composed of the brain and spinal cord,
and the peripheral nervous system, which includes neurons located outside the brain and spinal cord—that is, any nerves that enter or leave the
CNS
Two subdivisions of Peripheral nervous system
Efferent (E for Exit) and afferent divisions.
What is the purpose of efferent and afferent neurons
The efferent neurons carry signals away
from the brain and spinal cord to the peripheral tissues, and the afferent neurons bring information from the periphery to the CNS. Afferent neurons
provide sensory input to modulate the function of the efferent division through reflex arcs or neural pathways that mediate a reflex action
Devisions of efferent
the somatic and the ANS
What are the purpose of the somatic and autonomic NS
The somatic efferent neurons are involved in the voluntary control of functions such as contraction of the skeletal muscles essential for locomotion. The ANS, conversely, regulates the everyday requirements of vital bodily functions without the conscious participation of the mind. Because of the involuntary nature of the ANS as well as its functions, it is also known as the visceral, vegetative, or involuntary nervous system. It is composed of efferent neurons that innervate smooth muscle of the viscera, cardiac muscle, vasculature, and the exocrine glands, thereby controlling digestion, cardiac output, blood flow, and glandular secretions.
Divisions of the ANS
Sympathetic, parasympathetic, enteric
Where does the sympathetic preganglionic neurons originate?
In the CNS and emerge in the thoraxic ( T1 to T12) and Lumbar ( L1-L5) segments of the spinal cord.
Where does the parasympathetic preganglionic fibers originate?
Originate from cranial nerve nuclei 111, VII,IX and X AND sacral segment of the spinal cord
Where does the enteric (“Brain of the Gut”) originate
Myenteric plexus - Auerbach’s
Submucosal - Meissner’s
Two types of efferent neurons
the preganglionic neurons and the postganglionic neurons.
Where is the cell body of preganglionic neuron located
In the CNS (brain stem or spinal cord)
Where does the preganglionic neuron make a synapse?
The preganglionic neurons emerge from the brainstem or spinal cord and make a synaptic connection in ganglia (an aggregation of nerve cell bodies located in the peripheral nervous system). The ganglia function as relay stations between the preganglionic neuron and the second nerve cell, the postganglionic neuron.
Where is the postganglionic neuron’s cell body located?
The cell body of the postganglionic neuron originates in the ganglion.
Is postganglionic neurons myelinated
It is generally nonmyelinated and terminates on effector organs, such as smooth muscles of the viscera, cardiac muscle, and the exocrine glands.
What is the importance of the afferent neurons?
The afferent neurons (fibers) of the ANS are important in the reflex regulation of this system (for example, by sensing pressure in the carotid sinus and aortic arch) and in signaling the CNS to influence the efferent branch of the system to respond.
