AUTONOMIC NERVOUS SYSTEM The ANS is part of the efferent portion of the peripheral nervous system

Functions n Regulation of heartbeat n Smooth muscle contraction n Secretions of glands ***It is controlled by the hypothalamus with input from the cerebral cortex and limbic system

Comparing the Somatic and Autonomic Nervous System

Somatic Nervous System n Receptors (sensory neurons) are sensitive to external enviroment and transmit signals to the CNS n Causes stimulation of reflexes or conscious sensation n Information from efferent fibers sent to skeletal muscle n Cell bodies located in CNS; only one motor neuron involved

Autonomic Nervous System n Internal enviroment monitored by interoceptors n Stimulation of ANS rarely results in conscious sensations n Visceral Effectors: smooth,cardiac muscle and glands n Pathway involves TWO motor neurons in sequence – Preganglionic neuron cell body is in CNS; Postganglionic cell body is outside CNS n Axon fibers of 2nd neuron not myelinated and release ACh or NE

Divisions of the Autonmic Nervous System Sympathetic Division - Flight or Fight Parasympathetic Division - Rest or Repose

Differ in location of preganglionic cell body n Sympathetic Division (Thoracolumbar) - cell bodies located in lateral gray horns of thoracic & lumbar regions of spinal cord n Parasympathetic Division (Craniosacral) - cell bodies found in cranial & sacral regions of the cord

Differ in location of ganglionic synapse n Sympathetic Division - – Paravertebral ganglia - Chain ganglia – Prevertebral ganglia - Collateral ganglia – Postganglionic axon fiber is very long n Parasympathetic Division- – Terminal ganglia – close to effectors – Preganglionic axon fiber is long – Postganglionic axon fiber is very short

Neurotransmitters n Sympathetic Division - ACh is released at preganglionic axon terminal; NE or adrenalin is released at the postganglionic axon n Parasympathetic division - ACh is released at both synapses * Effect: inhibitory/excitatory depending on receptors on effectors

Length of influence n Sympathetic - is more widespread, more intense and response is of longer duration n Parasympathetic - a more controlled reaction with local effect and shorter duration

Types of Autonomic Neurons n Cholinergic neurons - release ACh – All preganglionic neurons & all parasympathetic postgangionic neurons n Adrenergic neurons - release NE – Most sympathetic postganglionic neurons

Sympathetic Responses n Pupils and bronchioles dilate n Heart and respiration rate increases n Dilation of blood vessels to skeletal muscles n Constriction of vessels to nonessential organs- BLOOD PRESSURE ZOOMS UP n Secretion and motility to digestive structures inhibited

Parasympathetic Responses n Constriction of pupils and bronchioles n Decreases respiration rate; slows down the heart n Increases blood flow to GI tract n Decreases blood flow to skeletal muscle n Kidneys begin to function - urination n Erection on both male and female