GRQ #6 - ANS and Reflexes Flashcards
What are some examples of vital functions that the autonomic nervous system oversees?
heart rate, blood pressure, digestive and urinary processes
The ANS operates ____.
autonomously or without conscious control
What is a visceral reflex arc?
A series of events in which a sensory stimulus in an organ leads to a predictable visceral motor response mediated by the ANS
How does the ANS perform many of its autonomous functions?
through a series of visceral reflex arcs
How many steps occur in a visceral reflex arc of the ANS? (according to figure 14.1)
4
What is step 1 of a visceral reflex arc of the ANS?
- sensory signals from the viscera and skin are sent by afferent sensory neurons to the brain or to the spinal cord
What is step 2 of a visceral reflex arc in the ANS?
- the stimuli are then integrated by the CNS
What is step 3 of a visceral reflex arc in the ANS?
- motor impulses from the CNS are sent out via efferent motor neurons in cranial and spinal nerves that usually lead to autonomic ganglia (ganglia in the PNS)
What is step 4 of a visceral reflex arc in the ANS?
- the autonomic ganglia send the impulses via other efferent motor neurons to various target organs, where they trigger a motor response in the target cells
What are autonomic ganglia?
A collection of cell bodies of postganglionic autonomic neurons
Somatic motor neurons largely control what type of movement? They innervate what kind of muscle fibers?
Voluntary muscle contractions or those that are initiated consciously. Somatic motor neurons innervate skeletal muscle fibers.
How do somatic motor neurons stimulate skeletal muscle fibers?
They stimulate skeletal muscle fibers by releasing the neurotransmitter acetylcholine (ACh)
The somatic nervous system targets ____ and controls ___ movement.
skeletal muscle fibers; voluntary
The autonomic nervous system targets ____, ____, and ____ and controls ____ movement.
smooth muscle cells, cardiac muscle cells and glands; involuntary
Motor neurons in the autonomic nervous system ___ directly innervate their target cells. Instead ___ ___ are involved.
Do NOT. Instead 2 neurons are involved.
What are the names of the 2 neurons involved in innervating target cells in the ANS?
The preganglionic neuron and the postganglionic neuron.
What is the preganglionic neuron?
The initial efferent autonomic neuron whose cell body is located in the CNS in either the spinal cord or the brainstem.
Where does the preganglionic neuron synapse?
On the cell body of the postganglionic neuron within an autonomic ganglion in the PNS.
What is the postganglionic neuron?
An autonomic neuron whose cell body is located in an autonomic ganglion in the PNS.
Where does the axon of the postganglionic neuron synapse?
On the target cell
How does the postganglionic neuron trigger a change?
It triggers a change by releasing various neurotransmitters, including ACh and norepinephrine.
The neurotransmitters released by the postganglionic neuron may ___ or ____ their target cell.
stimulate or inhibit.
