ANS: Autonomic Nervous System : Consists of motor neurons that innervate smooth muscles, cardiac, and glands. Shunts blood to areas that are needed, adjusts heart rate, blood pressure, etc
ANS Effectors: Innervates cardiac & Smooth muscles & glands.
ANS Pathways & Ganglia: Uses 2 neuron chain. Preganglion Neuron: Cell body in CNS with thin, lightly myelinated, Pregangliaonic Axon, extends to ganglion; Postganglionic Neuron: Cell body synapses with preganglionic axon in autonomic ganglion with nonmyelinated postganlionic axon that extends to effector organ.
ANS: Preganglic fibers release ACh, Postganglionic fibers release NE or ACh at effectors. Either stimulatory, inhibitory, depends.
SNS Effectors: Innervates skeletal muscles.
SNS Pathways & Ganglia: Cell Body is in CNS, & a single, thick myelinated group. Axon extends in spinal or cranial nerves directly to skeletal muscle.
SNS: All somatic motor neurons releases ACh, effect is always stimulating
DIVISIONS OF ANS
Parasympathetic Division: Promotes maintenance functions, conserves energy
Also called craniosacral division because fibers originate from brain stem & sacral regions. Long preganglionic fibers extend from CNS almost to target organs. Ex: Person relaxing & reading, Blood pressure, heart rate respiratory rates are low, Gastrointestinal tract activity is high, pupils constricted etc. *REST-DIGEST SYSTEM
Sympathetic Division: Mobilizes body during activity
Exercise, excitement, emergency, embarrassment activates sympathetic system. During vigorous physical activity: shunts blood to skeletal muscles, heart, dilates bronchioles, causes liver to release glucose. Sympathetic is more complex & innervates more organs than ps. Some structures are innervate only by sympathetic, sweat glands, arrector pili muscle, smooth muscles etc. Also called Throacolumbar division because neurons are in T1-L2. FIGHT-FLIGHT SYSTEM
Visceral Sensory Neurons: Send info about chemical changes, stretch, temperature, etc. Around viscera, cell bodies located in dorsal root ganglia & sensory ganglia of cranial nerves.
Visceral Reflex: Have some components as somatic reflex arcs: receptor, sensory neuron, integration center, motor neurons & 3 main differences.
- Visceral Reflex Arc has 2 consecutive neurons in the motor pathway
- Afferent Fibers are **Visceral Sensory neurons
- Effectors are smooth, cardiac muscles & glands rather than skeletal muscles.
Neurotransmitters: ACh & NE. ACh is released by cholingeric fibers. All ANS preganglionic axons & ALL ps postganglionic azons NE is released by adrenergic fibers at; all sympathetic postganglionic axons.Cholingeric Receptors- 2 types binds ACh; 1 Nicotinic Receptors, 2 Muscarinic Receptors
Adrengic Receptors- 2 Major classes responds NE, Alpha & Beta Receptors.PS & S Interactions: Most visceral organs have dual innervation. AP's continually fire down axons of both, producing antagonistic interaction. Both ANS divisions are partially active, resulting in basal s & ps tone.
Control of ANS functions: ANS is under control of CNS centers.
Hypothalamus- is generally main integrative center of ANS activity. Cerebral input may modify ANS but does subconsciously. Works through limbic system structures on hypothalamic centers.
Homeostatic Imbalance:
Autonomic Neuropathy: Damage to autonomic nerves that is a common complication of diabetes mellitus. Other frequent symptoms include dizziness after standing suddenly, urinary incontinence, sluggish eye pupil reactions, etc. Best way to prevent diabetic neuropathy is maintain good blood glucose.
Hypertension: Overactive sympathetic vasoconstrictor response to stress. Heart works harder & artery walls are subject to increased wear & tear. Treated with adrergic receptor-blocking drugs.
Rayaud's Disease: Painful, exaggerated vasoconstriction in fingers & toes. Digits turn pale, then cyanotic, treated with vasodilators.
Autonomic Dysreflexia: Life-threatening, uncontrolled activation of autonomic neurons in quadriplegics & people with spinal cord injuries about T6. Blood pressure skyrockets, posing increasted risk for stroke.