chapter 11- human physiology summary

Autonomic Division

• Physiological Role: Autonomous control of internal organs; involuntary control

• Division: Sympathetic (fight or flight) and parasympathetic (rest and digest)

Sympathetic vs. Parasympathetic

• Sympathetic: Originates in thoracolumbar region; short preganglionic neuron, long postganglionic neuron.

• Parasympathetic: Originates in brainstem/sacral region; long preganglionic neuron, short postganglionic neuron.

Efferent Division Overview

• Efferent Neurons: Transmit signals from CNS to effectors like muscles and glands.

• Somatic Neurons: Control voluntary movement; directly initiate muscle contractions.

• Autonomic Neurons: Control involuntary functions; regulates heart rate, digestion, etc.

Neurotransmitters

• Sympathetic: Mostly norepinephrine (adrenergic receptors).

• Parasympathetic: Acetylcholine (cholinergic receptors).

Autonomic Pathways

• Two Neuron System: Preganglionic neuron -> Ganglion (first neuron) -> Postganglionic neuron.

• Divergence: Preganglionic neurons can connect to multiple postganglionic neurons.

Chemical Communication

• Neurotransmitter Synthesis: ACh and NE synthesized in the axon terminals. Reception via specific receptor types (nAChR, adrenergic).

Adrenal Medulla

• Function: Releases catecholamines (epinephrine, norepinephrine) to enhance sympathetic responses during stress.

Control of Homeostasis

• Role in Homeostasis: Regulates body systems, balances sympathetic and parasympathetic activity for optimal function (e.g., heart rate, digestive activity).

Summary of Autonomic Division Control

• Tonic Control: Continuous regulation (e.g., blood vessels).

• Antagonistic Control: Sympathetic and parasympathetic branches often have opposing effects on the same organ.

• Varied Responses: Different receptors can cause different responses in different tissues (e.g., adrenergic receptors in blood vessels: vasoconstriction vs vasodilation).