Bio 209 Ch 15

• Sensory Input
• Somatic: (1) sensory neurons carry info from somatic sensory receptors and special sense organs to the CNS (2) sensations consciously perceived
• Autonomic: (1) sensory neurons carry info mainly from interoceptors to CNS (2) interoceptors are sensory receptors located in BV, visceral organs, muscles, nervous system that respond to changes in internal environment (3) sensations not usually consciously perceived

• Motor Output
• Somatic: (1) motor neurons extend from spinal cord to skeletal muscle (2) stimulation ALWAYS excitatory (3) conscious, voluntary control of contraction
• Autonomic: (1) two motor neurons in series (2) first motor neuron extends from spinal cord and synapses à second motor neuron in autonomic ganglia; second motor neuron innervates effectors (3) effects of ANS are cardiac & smooth muscles, glands (4) stimulation is either excitatory of inhibitory (5) stimulation modifies contraction but may not initiate it

• Neurotransmitters
• Somatic: neurotransmitter is ALWAYS Acetylcholine (Ach)
• Autonomic: neurotransmitter is EITHER Ach or Norepinephrine (NE)

Sympathetic & Parasympathetic

one division stimulates organ activity while the other inhibits it

• Preganglionic:
• (1) First neuron in motor pathway (2) Cell body in brain/spinal cord (3) Axon exits CNS as cranial/spinal nerve

• Postganglionic:
• (1) Second neuron in motor pathway (2) Cell body in autonomic ganglia (3) Axon extends to effector

Sympathetic: also called “Thoracolumbar” division because its cell bodies are located in lateral horns of the 12 thoracic, first two lumbar segments of spinal cord

Parasympathetic: also called “Craniosacral” division because its cell bodies are located in nuclei of 4 cranial nerves in brainstem, in lateral gray matter of 2nd-4th sacral segments of spinal cord

Sympathetic: vertical row of ganglion on either side of vertebral column

Parasympathetic: close to or within the wall of the effector

Sympathetic Pre-Ganglionic Axons travel a short distance to ganglia near vertebral column, while Parapsympathetic Pre-Ganglionic Axons travel a longer distance to ganglia near their effectors

Location: thorax, abdomen, pelvis

Contains axons of sympathetic and parasympathetic neurons

• Pre-Ganglionic
• Sympathetic: leaves spinal cord thru anterior (ventral) roots, then travel to nearest sympathetic trunk ganglion

• Post-Ganglionic
• Sympathetic: leaves trunk to (1) enter spinal nerves, to neck, trunk and limbs (2) form cephalic periarterial nerves (travel to hear by follwing arteries traveling form neck to hear) (3) form sympathetic nerves that innervate heart and lungs

• Pre-Ganglionic
• Parasympathetic: leaves CNS as part of (1) a cranial nerve or (2) an anterior root of a spinal nerve

• Post-Ganglionic
• Parasympathetic:

Acetylcholine

• Binds to:
• - Nicotinic receptors because nicotine mimics Ach; DOES NOT mimic muscarinic receptors
• - Muscarinic receptors because these receptors mimic Ach; DOES NOT mimic nicotine receptors

Norepinephrine

• Binds to:
• - Alpha Receptors: Alpha 1 & Alpha 2
• - Beat Receptors: Beat 1, Beta 2, Beta 3
• - Alpha1 & Beta 1 = Excitatory
• - Alpha 2 & Beta 2 = Inhibitory

• Agonist: chemical that binds to and activates a receptor, mimicking the effect of aneurotransmitter/hormone
• - Phenylephrine: common ingredient of cold/sinus medicine that binds to adrenergic Alpha-1 receptors and mimics action of norepinephrine (constricts BV in nasal mucosa causing the production of mucus to decrease and relieving nasal decongestion

• Antagonist: chemical that binds to and blocks a receptor, preventing a neurotransmitter/hormone from exerting an effect
• - Propanolol: antihypertensive drug that blocks Beta receptors and
• prevents binding of norepinephrine/epinephrine to Beta receptors (decreases BP by blocking Beta-1 receptors in the heart, causing a decrease in HR and force of contraction)
• - Metoprolol: selective Beta-1 blocker, binding only to Beta-1 receptors so it can reduce high BP without causing bronchoconstriction

Balance between sympathetic and parasympathetic activity (if sympathetic increases, parasympathetic decreases)

• Sympathetic:
• (1) Fight-or-Flight
• (2) Active when body is stressed (ex: running from a bear)

• Parasympathetic:
• (1) Resting and Digesting
• (2) Active when relaxing after a meal, reading etc.
• (3) SLUDD (Salivation, Lacrimation, Urination, Digestiong, Defecation)

• Components:
• (1) Receptor, sensory neuron, intergrating center, motor neuron, effector
• (2) Main integrating centers in hypothalamus and brain stem; integrating centers for urination and defecation

• Control:
• (1) BP, respiration, digestion, defecation, urination

• (1) Receives sensory input from interoceptores
• (2) Integrates info
• (3) Sends output to autonomic centers in brain stem and spinal cord