ch 14

motor division of the PNS

cardiac or smooth muscle or glands

a 2 neuron motor unit

its cell body is in the brain or cord

the site of synapse

its cell body and/or dendrites are in the ganglion

effector

ACH

NE or ACH

pre ganglionic neurons cell bodies are in the thoracic segments & the first 2 or 3 lumbar segments of spinal cord

• paravertebral
• prevertebral

sympathetic trunk

anterior and associated w/ large abdominal arteries

ganglia are close to CNS and far from effectors

synapses w/ many post ganglionic neurons & stimulate numerous visceral effectors

craniosacral

1) preganglionic neurons cell bodies are in the cranial nerves and the sacral segments of the spinal cord

terminal ganglia-

located at the end of the pathway, close to or within the effector

ganglia are far from the CNS and close to effectors

synapses with 4 or 5 post ganglionic neurons and stimulate a single visceral effector

• -released by all preganglionic neurons in both divisions
• -released by all parasympathetic post-ganglionic neurons
• - releasd by a few sympathetic post ganglionic neurons (sweat glands, blood vessels, some skeletal muscles, external genitalia)
• - short lived, rapidly degrading

• released by most sympathetic post- ganglionic neurons
• - has longer lasting more widespread effects- because its is broken down much more slowly

• it is the receptor which determines the effect of the neurotransmitter on the effector.
• same Neurotransmitter will have diff effects depending on the type of receptor

bind ACH, named for drugs that bind to them and mimic ACH's effect

found on all post-ganglionic neurons in both divisions and on hormone producing cells of the adrenal medulla

• always excitatory
• opens ion channels
• depolarizes the post-synaptic membrane

• found on all effector cells of parasympathetic target organs and a few sympathetic targets
• eccrine sweat glands & some blood vessels in skeletal muscles

can be excitatory (smooth muscle of digestive tract) or inhibitory (heart) depending on the subclas of receptor located on the target organ

bind norepinephrine and are found on most sympathetic post-ganglionic neurons

effects are usually excitatory by causing increased permeability of membrane to Na+

most have inhibitory effects by causing increased permeability to K+ out and Cl- in

• in the heart NE binding causes an increase in strength of contraction & heart rate
• hence, use of beta blockers for high blood pressure

• 1) dual innervation
• 2) dynamic antagonism
• 3) parasympathetic resting and digesting
• 4) sympathetic flight or fight
• 5) cooperative effects

increase heart rate, open airways, inhibit digestion & elimination

heart rate & airway diameter return to normal, digestive processes, refuel & eliminate wastes

parasympathetic control: lubrication (glandular secretion) and erectors (blood vessel dilation in penis & clitoris)

sympathetic control. sinal cort mediated reflexes that result in ejaculation of semen and contractions of vaginal & uterine walls

• - keeps blood vessels in a constant state of partial constriction
• - maintains adequate blood pressure
• - also allows blood to be shunted away from viscera to skeletal muscle when muscles are vigorously contracting

• -dominates in the heart and in the smooth muscle of the digestive and urinary tracts
• - slows the heart (vagal tone) and sets the normal activity levels of digestive & urinary processes
• (sympathetic can override in cases of stress)