Ch 9 Flashcards
Somatic Nervous System
- somatic neurons have cell bodies in spinal cord and just one neuron traveling from spinal cord to effector (neuromuscular junction)
- somatic motor neurons release only ACh which is always excitatory
Autonomic Nervous System
Sympathetic and Parasympathetic divisions
- two neurons in PNS
1. first has cell bodies in brain or spinal cord and synapses in autonomic ganglion
2. second has cell bodies in ganglion and synapses on the effector
-autonomic neurons release mainly ACh and norepinephrine and may be excitatory or inhibitory (ex. raise or lower HR)
Autonomic Neurons
- innervate organs not under voluntary control
- effectors include:
- -> cardiac muscle, smooth muscle of visceral organs/blood vessels, glands
- part of PNS
- autonomic neurons can stimulate or inhibit, depending on organ and receptors
- -> preganglionic and postganglionic
- -> autonomic ganglia are located in head, neck, and abdomen as well s in chains along either side of spinal cord
Preganglionic neurons
originate in the midbrain or hindbrain or from the thoracic, lumbar, or sacral spinal cord
Postganglionic neurons
originate in ganglion
Sympathetic Division
preganglionic neurons come from thoracic and lumbar regions (thoracolumbar)
-preganglionic neurons synapse in sympathetic ganglia that run parallel to spinal cord (paravertebral ganglia) –> connected forming sympathetic chain of ganglia
Adrenal Glands
- adrenal medulla secretes epinephrine and norepinephrine when stimulated by sympathetic nervous system
- directly innervated by preganglionic sympathetic neurons
Parasympathetic Division
preganglionic neurons come from the brain or sacral region of the spinal cord (craniosacral division)
- synapse on ganglia located near/or in effector organs called terminal ganglia
- preganglionic neurons do NOT travel w/somatic neurons
- terminal ganglia supply very short postganglionic neurons to then effectors
Occulomotor Nerve
- MOTOR NERVE
- preganglionic fibers exit midbrain and synapse on ciliary ganglion
- postganglionic givers innervate the ciliary muscle of the eye
Vagus Nerve
- MOTOR/SENSORY NERVE
- preganglionic fibers exit medulla, branch into several plexi and nerves, and travel to ganglia within effector organs
Sympathetic Functions
- “fight or flight” –> release of norepinephrine from postganglionic neurons and secretion of epinephrines from adrenal medulla
- prepares body fro intense activity: increases HR/glucose levels
- regulates heart, blood vessels, and other organs
Parasympathetic Functions
antagonistic to sympathetic
- “rest and digest” –> release of ACh from postganglionic neurons
- slows HR and increases digestive activities
Cholinergic
ACh is used by all preganglionic neurons (sym, para)
- released from most parasympathetic postganglionic neurons
- some sympathetic postganglionic neurons (innervate sweat glands and skeletal muscle blood vessels) release ACh
Adrenergic
-norepinephrine is neurotransmitter released by most postganglionic neurons
Vericosities
swellings on axons of postganglionic neurons that release neurotransmitter along length of axon
-sympathetic/ parasympathetic neurons innervate the same tissues, but release different neurotransmitter
Adrenergic Stimulation
- can be epinephrine in blood OR norepinephrine from sympathetic nerves
- can stimulate or inhibit depending on receptors
Adrenergic Stimulation examples
heart, dilatory muscles of the iris, smooth muscles of many blood vessels
Adrenergic Inhibition examples
bronchioles in lungs, other blood vessels
–> inhibits contraction and causes dilation of these structures (ex. skeletal muscles)
Alpha Adrenergic Receptors
A1 and A2 (sympathetic)
- ->alpha receptors are more sensitive to norepinephrine
- postganglionic neuron
- eye, skin, skeletal muscle, stomach/intestine, liver
Beta Adrenergic Receptors
B1 and B2 (sympathetic)
- ->beta receptors are more sensitive to blood epinephrine
- adrenal medulla
- heart, skeletal muscle, lungs, liver
Cholinergic Stimulation
- ACh released from preganglionic neurons of both sympathetic/parasympathetic division is STIMULATORY
- ACh from postganglionic neurons of the parasympathetic division is usually stimulatory, but some are inhibitory (depending on receptors)
- ->generally sympathetic and parasympathetic effects are opposite
Cholinergic Receptors: Nicotinic
found in autonomic ganglia
- stimulated by ACh from preganglionic neurons
- serve as ligand-gated ion channels for Na and K
Cholinergic Receptors: Muscarinic
found in visceral organs
- stimulated by release of ACh from postganglionic neurons
- five types
- stimulatory or inhibitory
- openings of K or Ca channels
Organs with Dual Intervention
- most visceral organs are innervated by both sympathetic and parasympathetic neurons
- divisions most often oppose each other
- complementary effects occur when both divisions produce similar effects on same target
Dual Intervention
Opposition:
- heart rate: sym increases, para decreases
- digestive functions: sym decreases, para increases
- pupil diameter: sym dilates, para constricts
Complement:
- salivary gland secretion:
- sym constricts blood vessels = thicker secretion
- para stimulates watery secretion
Organs w/o dual intervention
only sympathetic
- adrenal medulla
- arrector pili muscles in skin
- sweat glands in skin
- most blood vessels
- regulated by increase and decrease in sym nerve activity
- important for body temp regulation through blood vessels and sweat glands
