TBL3 - Somatic & Autonomic Nervous Systems Flashcards
What does the central nervous system (CNS) consist of?
1) The brain
2) The spinal cord
What does the peripheral nervous system (PNS) consist of?
1) Cranial nerves
2) Spinal nerves
3) Autonomic nerves
What is the role of the CNS?
The principal roles of the CNS are to integrate and coordinate incoming and outgoing neural signals and to carry out higher mental functions, such as thinking and learning
What is the role of the PNS?
The peripheral nervous system (PNS) consists of nerve fibers and cell bodies outside the CNS that conduct impulses to or away from the CNS. The PNS is organized into nerves that connect the CNS with peripheral structures
What are two types of neurons that constitute the majority of neurons comprising the nervous system (and the peripheral nervous system in particular) and what are a few characteristics of each?
These excitable, conductive nerve cells are designated:
1) Multipolar (motor) neurons
a) Most common in the nervous system
b) All of the motor neurons that control skeletal muscle and those comprising the ANS are multipolar neurons
2) Pseudounipolar (sensory) neurons
a) Short, double process covered by pia mater, CSF, arachnoid mater, & dura mater
Where do the mulitpolar neurons project from, in which direction are impulses sent and what is their function?
1) Multipolar neurons in anterior horns of the spinal cord project long motor axons of the spinal nerves that conduct impulses away from the CNS
2) The axons are designated efferent axons that voluntarily activate skeletal muscles of the body wall and extremities
Where do the pseudounipolar neurons project from, in which direction are impulses sent and what is their function?
1) Sensory neurons have a single short stem that divides into peripheral and central axons
2) Sensory neurons reside in a spinal ganglion (aka dorsal root ganglion or DRG) of the PNS. In the ganglion, sensory impulses pass from the long peripheral axons directly onto the shorter central axons, which comprise the posterior roots of the spinal nerves
3) Together the axons convey sensations of touch, pain, and temperature from muscles, bones, and skin of the body wall and extremities into the CNS; thus, they are designated afferent axons
What are interneurons?
1) Posterior roots synapse with neurons in the posterior horn of the spinal cord
2) These multipolar neurons are designated interneurons that convey the sensory impulses to motor neurons in the adjacent anterior horn or help convey the sensory impulses to the brain
Which neurons are affected by amyotrophic lateral sclerosis (ALS) and why is the disease ultimately fatal?
1) Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig disease, is a progressive neuromuscular disorder caused by destruction of specific neurons in the brain and spinal cord. ALS belongs to a class of disorders known as motor neuron diseases and results in loss of nervous control of skeletal muscles, which leads to degeneration and atrophy of muscle fibers
2) Respiratory muscles are ultimately affected; death is thus due to an inability to breathe
Aside from the spinal nerves, which nerves also contain motor and sensory axons? What do these two types of nerves constitute?
1) The cranial nerves also contain motor and sensory axons that innervate skeletal muscles, bones, and skin of the head and neck
2) Cranial nerves and spinal nerves innervate all parts of the body (soma) except the organs, glands, and smooth muscles; thus, they are designated somatic nerves and constitute the SNS
What does the autonomic nervous system (ANS) do?
The ANS (visceral nervous system or visceral motor system) includes a pair of multipolar neurons that involuntarily regulate the organs (viscera), glands, modified cardiac muscle (the intrinsic stimulating and conducting tissue of the heart) and smooth (involuntary) muscles
Where do the pair of multipolar neurons from the ANS reside? What are two divisions of the ANS?
1) The nerve cell body of the first presynaptic (preganglionic) neuron is located in the gray matter of the CNS
2) The fiber (axon) of the first neuron synapses only on the cell body of a postsynaptic (postganglionic) neuron, the second neuron in the series found in the PNS. The cell bodies of these second neurons are located outside the CNS in autonomic ganglia, with fibers terminating on the effector organ (smooth muscle, modified cardiac muscle, or glands)
3) The pair of motor neurons represents the sympathetic division of the ANS
4) The parasympathetic division provides contrasting, yet coordinated regulation of the viscera, glands, and smooth muscles
