Autonomic motor system

Know and understand the function and importance of the autonomic nervous system

A complex system of nerves that govern involuntary actions. Works with the somatic nervous system to regulate body organs and maintain normal internal functions

Homeostasis

Adjusts internal water, electrolytes, nutrients, and gas concentrations in the body outside of conscious awareness

Somatic nervous system

Operates under conscious control. Uses somatic sensory neurons to conduct stimulus information from a sensory receptor and some somatic motor neurons to innervate skeletal muscle fibers

Autonomic nervous system

Functions are involuntary. Also utilizes sensory and motor neurons.

Visceral sensory neurons & somatosensory receptors

Provide input to activate the ANS

Autonomic motor neurons

Innervate smooth and cardiac muscle fibers or glands

Divisions of the ANS

Subdivided into parasympathetic and sympathetic

Divisions

Similar in that they both use a preganglionic neuron and a ganglionic neuron to innervate muscles or glands, but perform dramatically different functions. Both contain the autonomic ganglia that house the ganglionic neurons. Both are involuntary and are concerned with the body's internal environment. Both regulate homeostasis

Parasympathetic division

Primarily concerned with conserving energy and replenishing nutrient stores, "rest and digest", "rest and repose." Most active when the body is at rest or digesting a meal

Parasympathetic activities

Constricts pupils to restrict light, helps with reading, stimulation of defecation, constriction of respiratory passageways, reduces heart rate, stimulation of sexual arousal and glands.

Sympathetic division

Primarily concerned with preparing the body for emergencies, "fight or flight." Increased activity results in increased alertness & metabolic activity necessary in times of fear, stress, increased exertion, or emergency

Sympathetic activities

Increases feeling of euphoria, increased activity of cardiovascular and respiratory centers, elevated blood pressure, heart rate, depth, and rate of breathing, muscle tone (look tense, shiver, mobilize energy reserves) Preganglionic neurons form T1-L2; postganglionic neuron near spinal cord

Why is dual innervation by the parasympathetic and sympathetic divisions necessary?

Usually organs are innervated by both divisions. Actions of the divisions usually oppose each other. Communication by neurotransmitters, specific in each division. Maintains homeostasis through autonomic reflexes that occur in the innervated organs

Opposing effects

are achieved by increasing or decreasing activity in one division

Autonomic plexuses

Innervate organs through specific axon bundles

What neurotransmitters are used by each division, and by what portions of each division?

Two are used in the ANS, acetylcholine (ACh) and norepinephrine (NE). Released by the presynaptic cell. Bind to specific receptors in the postsynaptic cell membrane. Binding has either an excitatory or an inhibitory effect on the effector, depending on the receptor. Released by the presynaptic cell, and received by postsynaptic cell

Neurotransmitters in parasympathetic division

Both preganglionic and postganglionic axons in this division release acetylcholine and thus are called cholinergic.

Neurotransmitters in sympathetic division

The preganglionic axon and a few postganglionic axons in this division are also cholinergic. Most of the postganglionic axons in this division release norepinephrine and are called adrenergic

What is an autonomic reflex, and why are they important?

Or visceral reflexes, help maintain homeostasis. Similar to spinal reflexes. Involuntary. Reflex arcs consist of smooth and cardiac muscle contractions, or secretion by glands in response to a specific stimulus

Micturition reflex

Partly controls the release of urine

Other reflexes (Autonomic reflexes)

Alteration of heart rate, changes in respiratory rate and depth, regulation of digestive system activities, and alteration of pupil diameter

How does the CNS control the ANS?

Autonomic function is influenced by the cerebrum, hypothalamus, brainstem, and spinal cord. Brainstem nuclei in the mesencephalon, pons, and the medulla oblongata mediate visceral reflexes

Hypothalamus

Central brain structure involved in emotions and drives that act through the ANS

Sensory processing in the thalamus

And emotional states, controlled in the limbic system directly affect the hypothalamus

Reflex centers

Control accommodation of the lens, blood pressure changes, blood vessel diameter changes, digestive activities, heart rate changes, and pupil size

Centers for cardiac, digestive, and vasomotor functions

Housed within the brainstem

Some responses in CNS control of autonomic function

Processed and controlled at the level of the spinal cord without the involvement of the brain. Higher centers in the brain may consciously inhibit these reflex activities