Chapter 14 Flashcards
Autonomic Nervous System (ANS)
Motor neurons that:
-Innervate smooth muscle cardiac muscle, and glands
-Make adjustments to ensure optimal support for body activities
-Operate via subconscious control
Involuntary Nervous System: Fight-or-Flight
Somatic Versus Autonomic Nervous Systems
Both have motor fibers Differences -Effectors -Efferent pathways and ganglia -Target organ responses to neurotransmitters
Effectors
Somatic nervous system -Skeletal muscles Autonomic Nervous System -Cardiac muscle -Smooth muscle -Glands
Efferent Pathways and Ganglia
Somatic Nervous System
- Cell body in CNS
- Thick, myelinated fibers
- Spinal or cranial nerve to skeletal muscle
Autonomic Nervous System Pathway uses 2-Neuron Chain
- Pre-ganglionic Neuron
- In CNS has a thin lightly myelinated axon - Post-ganglionic Neuron
- Autonomic ganglion outside CNS
- Nonmyelinated axon extends to effector organ
Neurotransmitter Effects: Somatic Nervous System
- All somatic motor neurons release acetylcholine (ACh)
- Effects always stimulatory
Neurotransmitter Effects: Autonomic Nervous System
Pre-ganglionic fiber release ACh
Post-ganglionic fibers release norepinephrine or ACh at effectors
Effect is either stimulatory of inhibitory, depending on type of receptors
Overlap of Somatic and Autonomic Function
Most spinal and many cranial nerves contain both somatic and autonomic fibers
Adaptations usually involve both skeletal muscles and visceral organs
Divisions of the Autonomic Nervous System
Sympathetic division
Parasympathetic division
Dual innervation
Dual Innervation
All visceral organs served by both divisions but cause opposite effects
Role of Parasympathetic Division
Maintenance activities and conserves body energy -Directs digestion Person relaxing and reading after a meal -low BP and Heart Rate -Gastrointestinal tract activity high -Pupils constricted
Role of Sympathetic Division
Mobilizes body during activity "Fight or Flight" system -Exercise -Excitement -Emergency -Embarrassment Increased BP and Heart Rate, Tensed
Role of the Sympathetic Division During Vigorous Physical Activity
Shunts blood to skeletal muscles and heart
Dilates bronchioles
Causes liver to release glucose
Run away to survive
Sympathetic Trunks and Pathways
Paravertebral ganglia vary in size, position, and number
There are 23 paravertebral ganglia in the sympathetic trunk (chain)
-3 Cervical
-11 Thoracic
-4 Lumbar
-4 Sacral
-1 Coccygeal
Pathways with Synapses in Trunk Ganglia: Fibers that Innervate
Sweat Glands
Arrector Pili Muscles
Vascular Smooth Muscle
Pathways to Head
Fibers synapse in the superior cervical ganglion
These fibers:
-Innervate skin and blood vessels of the head
-Stimulate dilator muscles of the iris
-Inhibit nasal and salivary glands
-Innervate smooth muscle of upper eyelid
-Branch to heart
Pathways to Thorax
These Fibers Innervate:
- Heart vis the cardiac plexus
- Thyroid gland and the skin
- Lungs and esophagus
Pathways to Abdomen
Post-ganglionic fibers serve the stomach, intestines, liver, spleen, and kidneys
Pathways to Pelvis
Post-ganglionic fibers serve the distal half of large intestine, the urinary bladder, and the reproductive organs
Primarily inhibit activity of muscles and glands in abdominopelvic visceral organs
Pathways with Synapses in the Adrenal Medulla
Upon stimulation, medullary cells secrete norepinephrine and epinephrine into blood
Visceral Pain
Visceral pain afferent travel along same pathways as somatic pain fibers, contributing to phenomenon of referred pain
Neurotransmitter
Cholinergic Fibers
Adrenergic Fibers
Cholinergic Fibers
Release ACh
- All ANS pre-ganglionic axons
- All parasympathetic post-ganglionic axons at effector synapse
Adrenergic Fibers
Release Norepinephrine
-Most sympathetic post-ganglionic axons
Interactions of the Autonomic Divisions
Most visceral organs have dual innervation
Dynamic antagonism allows for precise control of visceral activity
-Sympathetic division increase heart and respiratory rates, and inhibits digestion and elimination
-Parasympathetic division decreases heart and respiratory rates, and allows for digestion and discarding wastes
Sympathetic Division
Long
Body Wide Effects
Parasympathetic Division
Short
Localized
Control of ANS Function
Hypothalamus
-Main integrative center of ANS activity
Subconscious cerebral input
-via limbic system structures on hypothalamic centers
Other controls come from cerebral cortex, reticular formation, and spinal cord
Hypothalamic Controls
Control may be direct or indirect
Centers of Hypothalamus Controls
Heart activity and blood pressure
Body temperature, water balance, and endocrine activity
Emotional stages (rage, pleasure) and biological drives (hunger, thirst, sex)
Reactions to fear and “fight or flight” system
Cortical Controls
Connections of hypothalamus to limbic lobe allow cortical influence on ANS
Voluntary cortical control of visceral activities is possible
Biofeedback of Cortical Controls
Awareness of physiological conditions with goal of consciously influencing them
Training allows some to control migraines and manage stress
Homeostatic Imbalances of ANS
Hypertension Raynaud's Disease -pale than cold fingers Autonomic Dysreflexia -High BP and life threatening
Developmental of Aspects of the ANS
Older Age
- Dry eyes
- Constipation
- Low BP
