Ch 11: Efferent Nervous System

what does autonomic control?

smooth and cardiac muscle, lymphoid and adipose tissue, glands

sympathetic branch

fight or flight

parasympathetic branch

rest and digest

autonomic reflexes

involuntary stuff (homeostasis, body tmep, blood pressure, endocrine and brhavioral response)

antagonistic control

either excitatory or inhibitory (dynamic like a seesaw)

sympathetic neuron chain

CNS -> preganglionic neuron -> autonomic ganglion (near spinal cord) -> postganglionic neuron -> target tissue

parasympathetic neuron chain

CNS -> pregang neuron -> autonomic gang (near target tissue) -> postgang neuron -> target tissue

neurotransmitter used by parasymp

acetylcholine

neurotransmitter used by symp

acetylcholine at autonomic gang, norepinephrine at target tissue

vagus nerve

75% of parasympathetic fibers (info from brain to organs), stimulation helps with memory retention, implanted device in neck for stroke

bulk/volume transmission

neurotransmitters are released from varicosities (works the same way as synaptic transmission but is faster effect and greater effect)

volume transmission mechanism

action potential depolarizes area -> Ca2+ enters, triggering vesicle exosytosis -> neutransmitters bind to adregenic receptors on target -> reuptake/degradation/osmosis away

clinial application: beta blockers

very potent, used for hypertension, must be carefully regulated, "-olol"

receptors on target for parasympathetic branch

muscarinic - G-protein coupled receptors, stimulate K+ and Ca2+ influx

receptors on target for symp branch

adregenic, G-protein coupled but diff types with different effects

adrenal medulla

neurohormonal astructure, secretes epinephrine into blood (located near arteries)

postgang of adrenal medulla

chromaffin (not neurons, don't have exons, secrete into blood not organ)

somatic motor divison

controls skeletal muscle only (simpler than autonomic) - single CNS neuron with axon at target

neuromuscular junction

makes contact with target, has: acon terminal, Schwann cell sheaths, and motor end plates

motor end plates

lots of folds for more surface area and more sensitivity to Ach and depolarization, nicotinic Ach receptors

what terminates transmission at NMJ

enzymatic breakdown of Ach

myasthenia gravis

Ach receptors blocked by antibodies (treatment: AchE inhibitors, immunosuppressants)