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Ch. 11
Efferent peripheral nervous system
• Midterm 2 on Nov 11th will cover chapters 8, 10, 11.
• Today:– Autonomic division
• Homeostasis• Organization• Neurotranmsitters and neuromodulators• Receptors
Mixed nerves
• Afferent and efferent fibers
• Autonomic fibers (involuntary)
• Somatic motor fibers (voluntary)
Autonomic Division of the Peripheral Nervous System
• Sympathetic “branch”– dominates in stressful situations– In emergencies “fight or flight”– Always blood vessel diameter
• Parasympathetic “rest and digest”
Sympathetic and parasympathetic contributions to homeostasis
• Maintain the internal environment
• Tonic control
• Antagonistic control
• Specific receptors determine responses
Autonomic fibers exert tonic control of blood vessels- vasodilation or vasoconstriction
- sympathetic fibers- up or down control
Dual antogonistic innervation
Cooperation between sympathetic and parasympathetic effects
• E.g male reproductive system: – Parasympathetic fibers penile erection– Sympathetic fibers ejaculation
Different effect with different receptor: vasodilation or vasoconstriction
Brain regulates autonomic function
• Hypothalamus, pons, medulla
• Heart rate, blood pressure, temp. water balance
• Influence from limbic system and cerebral cortex
• Also autonomic reflexes e.g. urination
Autonomic efferent pathways
**divergence**
Blue, parasympathetic,Red, sympathetic
Parasympathetic ganglia are close To the targets
Autonomic neurotransmitters and receptors
Neuroeffector junction: synaptic vesicles are in varicosites
Norepinephrine release from varicosity: - MAO (monoamine oxidase) metabolizes NE