Unit 4 - ANS

What neurotransmitters are secreted by adrenergic and cholinergic fibers? Which fibers secret each neurotransmitter?

Cholinregic - acetylcholine adrenergic - norepinephrine sympathetic adrenergic fibers secrete each

How can the sympathetic division cause smooth muscle to relax in some organs but contract in others?

Dual innvervation - exerted through dual innervation of same effector cells heart rate decreases (PNS); heart rate increases (SNS) exerted b/c each division innervates different cells - pupillary dilator muscle (SNS) dilates pupil; constrictor pupillae (PNS) constricts pupil

What are the adrenal glands?

Located above each kidney and composed of two sections - adrenal cortex and adrenal medulla; secretes mineralcorticoids (aldosterone), glucocorticoids (cortisol), and androgens (male hormones)

What is the enteric nervous system and how does it work?

The Enteric Nervous System contains complete reflex circuits that detect the physiological condition of the gastrointestinal tract and integrate information about the state of the gastrointestinal tract.

Compare and contrast the sympathetic and parasympathetic division - fiber length of preganglionic and post ganglionic fibers, origin in CNS, location of ganglia, neurotransmitter of postganglionic fibers, amount of neural divergence, effects on cardiovascular, respiratory, GI, and urinary system

The parasympathetic nervous system (PNS) controls homeostasis and the body at rest and is responsible for the body's "rest and digest" function. The sympathetic nervous system (SNS) controls the body's responses to a perceived threat and is responsible for the "fight or flight" response. The PNS and SNS are part of the autonomic nervous system (ANS), which is responsible for the involuntary functions of the human body. preganglionic fibers synapse within the ganglion, and then short postganglionic fibers, 1 millimeter to several centimeters in length, leave the ganglia to travel a short distance to the target organ; sympatheitc fibers tend to be shorter than PNS fibers b/c SNS ganglia are closer to the spinal cord than are the PNS ganglia Cns originates in the brain and extends down to the lower extremity of the trunk PNS originates in craniosacral region from brainstem and sacral plexus SNS originates in the spinal cord ganglia in PNS - head (ciliary, otic, pterygopalatine, and submandibular) ganglia in SNS - along sides of the spinal cord (paravertebral or chain ganglia) neurotransmitter of postganglionic fibers in sympathetic division use norepinephrine (noradrenalin); in parasympathetic division they use acetylcholine extensive neural divergence in the sympathetic; minimal divergence in the parasympathetic division

How does the autonomic nervous system differ from the somatic nervous system? How is it similar?

The somatic nervous system has sensory and motor pathways, whereas the ANS only has motor pathways. The ANS controls internal organs and glands, while the somatic nervous system controls muscles and movement. The sympathetic nervous system (part of the autonomic nervous system) and the somatic nervous system respond to external stimuli. The sympathetic nervous system responds to external stimuli by preparing the body for fight or flight and the somatic nervous system responds to external stimuli (by carrying information from sensory receptors to the spinal cord and brain).

Suppose that the cardiac nerves were destroyed. How would this affect the heart and the body's ability to react to a stressful situation?

Vagal (parasympathetic) tone would predominate and the heart would beat more slowly than normal, a condition called bradycardia. In emergency situations, the heart would not speed up as it normally does, and the lack of increased circulation would compromise one's tolerance of physical exertion and reaction to stress.

How can the sympathetic nervous system have contrasting effects in a target organ without dual innervations?

adrenal medulla, piloerector muscles, sweat glands, and many blood vessels receive only sympathetic fibers. ex: blood pressure/routes of blood flow

Explain the three routes that sympathetic fibers can follow (give the name and the path)

spinal nerve route sympathetic nerve route splanchnic nerve route

Why do the sympathetic effects last longer than parasympathetic?

they are reabsorbed in the bloodstream before finally degrading in the liver, so they last minutes instead of seconds (not quickly broken down by AChE like sympathetic fiber)