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