Chapter 11 - Efferent Division

Autonomic neurons control

smooth and cardiac muscle, many glands, and some adipose tissues

Which system does the autonomic neurons work with to maintain homeostasis?

endocrine and behavioral state systems

CNS regions involved in control of autonomic system

Hypothalamus, pons, medulla

Antagonistic Control

modulates the activity of an organ system by two separate regulators which act in opposition (excitatory, inhibitory)

Preganglionic

CNS to autonomic ganglion

postganglionic

ganglion to target

Divergence in ganglions

1 preganglionic neuron reaches multipule post ganglionic neurons

Pathway of sympathetic

short preganglionic, long postglanglionic neurons

pathway of parasympathetic

long preganglionic, short postganglionic neurons

sympathetic ganglion location

close to spinal cord (formed as two ganglion chains)

parasympathetic ganglion location

on or close to targets

origin of sympathtic ganglia in CNS

thoratic and lumbar segments (of spinal cord)

Origin of parasympathetic ganglia in CNS

brainstem and sacral segments

Vagus nerve is a major part of

parasympathetic branch (75%) that delivers info from or to the brain (from/to internal organs)

Vasovagal response/syncope

A sudden drop in heart rate and blood pressure leading to fainting, often in reaction to stressful trigger

Vasovagal response/syncope cause

overactivation of vagal nerve and the parasympathetic response

neurotramsitter of sympathetic pathway

acetylcholine (1빠) and norepinephrine

neurotransmitter of parasympahtetic pathways

acetylcholine (1빠, 2빠)

Postganglionic sympathetic neurons release NE onto?

(α, β) adrenergic receptors

Postganglionic parasympathetic neurons release ACh onto?

mAChR (muscarinic receptor)

what is one exception of postganglionic sympathetic neuron release?

cholinergic neurons release ACh not norepinephrine

Neuroeffector junction

the synapse between a postganglionic autonomic neuron and its non-neuronal target cells (effector)

varicosities

series of swollen areas at their distal ends where neurotransmitters are synthesized and released

Neuromodulation is done by

neurohormones and paracrine signals
(receptors on varicositites to regulate release of neurotransmitter)

α1 receptors (most common) reacts mostly to

norepinephrine

second messenger of α1

activate phospholipase C, creating inositol triphosphae (AP3) and diacylglycerol (DAG), leads to Ca2+ signaling inside the cell

β1 receptors controls

enhancement of cardiac contraction

β2 receptors control

relaxation of smooth muscles

β1 receptor responds to

epinephrine and norepinephrine equally

β2 receptor responds to

mostly ephinephrine

second messenger of β2

cyclic AMP and phosphorylation of intracellular proteins

Muscarinic receptors

G protein-coupled receptors, second messenger pathways, at least 5 sub types

Adrenam Medulla

neuroendocrine tissue associated with the sympathetic branch

Adrenal Medulla neurohormone

epinephrine (secreted into blood)
—> cause of adrenaline rush

Pharmaceutical drugs that target autonomic system

β blockers (propranolol), MAO inhibitors (selegeline. antidepressant)

Drugs of abuse: cocaine mechanism

blocks reuptake of monoamines, lasting longer in the synapse
- dopamine —> causes euphoria
- NE —> toxic cardiac effects

AChE inhibitors

overstimulation of muscarinic and nicotinic ACh receptors — affects both sympathetic and parasympathetic

Nicotinic symptoms of ogranophosphae poisoning

MTWTF
Mydriasis
Tachycardia
Weakness
Hypertension
Fasciculations

Muscarinic symptoms of organophosphate poisoning

DUMBELS
Defecation/diaphoresis
Urination
Miosis
Bronchospasm/bronchorrhea
Emesis
Lacrimation
Salivation

Dysautonomia

associated with other disease like cancer and diabetes
(ex. diabetic autonomic neuropathy)

Multiple system atrophy

autonomic functions degenerate (ex. widespread demyelination)

Somatic motor neurons control

skeletal muscles (voluntary)

somatic motor neurons origin and target?

originate in CNS and project to skeletal muscles

Pathway of somatic motor neurons

myelinated, can be very long, brances close to target to control many muscles

somatic motor neuron excitatory or inhibitory?

ALWAYS excitatory (activates muscle)

Neuromuscular junction (NMJ) includes

• presynaptic axon terminal filled with synaptic vesicles and mitcohondria

• synaptic cleft

• postynaptic membrane of the skeletal muscle fiber

• motor end plates

• schwann cell sheaths

Motor end plate (on muscle fibers) contains

• ALOT of nicotinic type M ACh receptors

• Acetylcholinesterase (to degrade neurotransmitter)

Neuromuscular junction (NMJ) is

a neuroeffector junction between neuron and muscle

Nm Cholinergic receptors open what type of channel for depolarization?

nonspecific monovalent cation channels

Myastenia gravis

NMJ disease that causes weakness in skeletal muscles that worsens after periods of activity and improves after periods of rest

Symptoms of Myasthenia Gravis

weakness of arm or leg muscles, double vision, drooping eyelids, difficulties with speech, chewing, swallowing, breathing

Cause of myasthenia gravis

loss of (type Nm) ACh receptors

why is myasthenia gravis chronic autoimmune?

antibodies attack ACh receptors for desctruction