The Efferent Division

what are the functions of autonomic neurons?

control smooth and cardiac muscle, many glands, and some adipose tissue mostly involuntary works with endocrine and behavioral state systems to maintain homeostasis

what is the CNS region involved in?

control of the autonomic systen

what are the functions of autonomic reflexes?

maintain homeostasis: temp control, water balance, eating, urinary bladder control, breathing, blood pressure

where are control centers of autonomic reflexes located?

in the hypothalamus, pons, and medulla

what does antagonistic control mean?

one autonomic branch is excitatory and the other is inhibitory

what are the sympathetic and parasympathetic responses of the heart?

sympathetic: increased heart rate and force of contraction parasympathetic: slower heart rate

what is the sympathetic response of the adrenal medulla?

secreted catecholamines

what are the sympathetic and parasympathetic responses of the urinary bladder?

sympathetic: urinary retention parasympathetic: release of urine

what 2 efferent neurons are in autonomic pathways?

preganglionic and postganglionic

what is the process of an autonomic pathway?

CNS → preganglionic neuron → autonomic ganglion → postganglionic neuron → target tissue

what is the divergence of autonomic pathways?

one preganglionic neuron typically synapses on multiple postganglionic neurons

what do sympathetic ganglia form?

2 ganglion chains along either side of the vertebral column

what is the parasympathetic branch and what is its purpose?

a) vagus nerve that contains about 75% of all parasympathetic fibers b) sensory information from internal organs to the brain and output from brain to organs

what is a vasovagal response/vasovagal syncope?

a sudden drop in heart rate and blood pressure leading to fainting, often in reaction to a stressful trigger overactivation of the vagal nerve and the parasympathetic response

what are the characteristics of sympathetic responses?

originates from the thoracic and lumbar segments of the CNS ganglions located close to the spinal cord short preganglionic, long postganglionic neuron pathways

what are the characteristics of parasympathetic responses?

originates from the brainstem and sacral segments of the CNS ganglions located on/close to targets long preganglionic, short postganglionic neuron pathways

what do preganglionic neurons release?

ACh onto nAChR

what do postganglionic sympathetic neurons release?

NE onto adrenergic receptors exception: sympathetic cholinergic neurons

what do postganglionic parasympathetic neurons release?

ACh on mAChR

what are neuroeffector junctions?

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

what are varicosities?

series of swollen areas at the distal ends where neurotransmitters are synthesized/released

where are neurotransmitters released?

into interstitial space and diffuse to receptors on target cell

what signals do neuromodulation?

neurohormone and paracrine

what allows for the regulation of the release of neurotransmitters?

varicosities have receptors for certain chemicals

what types of sympathetic receptors are there?

⍺- and β-adrenergic receptors with subtypes

what are the functions of ⍺1 receptors and where is it found?

a) react mostly to norepinephrine activates phospholipase C, creating IP3 and DAG, leads to Ca2+ signaling inside the cell, increases PKC5 b) in most sympathetic target tissues

what is the function of β1 receptors and where are they found?

a) responds equally to epinephrine and norepinephrine increases cAMP b) in heart muscle and kidney

what is the function of β2 receptors and where are they found?

a) responds mostly to epinephrine increases cAMP b) in certain blood vessels and smooth muscle of some organs

what is the function of β3 receptors and where are they found?

a) increases cAMP and phosphorylation of intracellular proteins b) in adipose tissue

what is the function of ⍺2 receptors and where are they found?

a) decreases cAMP b) in gastrointestinal tract and pancreas

what are parasympathetic receptors?

muscarinic cholinergic receptors in parasympathetic target cells

what is the function of NN receptors and where are they found?

a) opens nonspecific monovalent cation channels b) in postganglionic autonomic neurons

what is the function of NM receptors and where are they found?

a) opens nonspecific monovalent cation channels b) in skeletal muscle

what is the function of M1, M3, and M5 receptors and where are they found?

a) increases IP3 and intracellular Ca2+, increases PKC5 b) in nervous system and parasympathetic target tissues

what is the function of M2 and M4 receptors and where are they found?

a) decreases cAMP, opens K+ channels b) in nervous system and parasympathetic target tissues

what happens in sympathetic and parasympathetic pathways when there is inactivation of neurotransmitter at synapse?

sympathetic: uptake into varicosity, diffusion parasympathetic: enzymatic breakdown, diffusion

what is the neuron-target synapse for sympathetic and parasympathetic pathways?

sympathetic: NE on ⍺- or β-adrenergic receptor parasympathetic: ACh on muscarinic receptor

what is the adrenal sympathetic system?

adrenal medulla neuroendocrine tissue associated with the sympathetic branch primary neurohormone is epinephrine which is secreted into the blood

what do β blockers target?

propranolol

what do MAO inhibitors target?

selegeline

what does cocaine do the body?

blocks reuptake of monoamines, specifically NE, leading to toxic cardiac effects

what are the effects of AChE inhibitors?

overstimulation of muscarinic and nicotinic ACh receptors

what does organophosphate poisoning affect?

both sympathetic and parasympathetic systems

what are the nicotinic signs of AChE inhibitors?

MTWHF: mydriasis, tachycardia, weakness, hypertension, fasciculations

what are the muscarinic signs of AChE inhibitors?

DUMBELS: defecation/diaphoresis, urination, miosis, bronchospasm/brochorrhea, emesis, lacrimation, salivation

what is dysautonomia?

diabetic autonomic neuropathy associated with other diseases like cancer and diabetes

what is multiple system atrophy?

autonomic functions degeneration

what is the function of somatic motor neurons?

control skeletal muscles mostly voluntary

what are the characteristics of a single neuron?

originate in the CNS and project to skeletal muscles myelinated, can be very long branch close to targets to control many muscle fibers excitatory

what are the characteristics of a neuromuscular junction (NMJ)?

presynaptic axon terminal filled with synaptic vesicles and mitochondria consists of axon terminals, motor end plates on the muscle fibers, and schwann cell sheaths

what does acetylcholinesterase do to the neuromuscular junction?

degrades neurotransmitter

what is the motor end plate?

region of muscle membrane that contains high [ ] of ACh receptors

what is the process of neurotransmitter release at the NMJ?

→ action potential arrives at the axon terminal → voltage-gated Ca2+ channels open → release of ACh-containing vesicles into synaptic cleft → ACh binds to nAChRs at the motor end plate → nAChRs (NM subtype) opens → Na+ enters muscle fibers, K+ leaves → depolarization of muscle fiber → triggers action potential in muscle fiber → contraction → termination of signal by AChE

what is myasthenia gravis?

the most common disorder of the NMJ chronic, autoimmune, neuromuscular disease that causes weakness in the skeletal muscles that worsens after periods of activity and improves after periods of rest characterized by loss of ACh receptors

what are common symptoms of myasthenia gravis?

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

what are the characteristics of the somatic motor division?

1 neuron in efferent path ACh/nicotinic receptors at neuron-target synapse targets skeletal muscle neurotransmitters released from axon terminals excitatory effects: muscle contracts axons found outside of CNS functions: posture and movement

what are the characteristics of the autonomic division?

2 neurons in efferent path ACh/muscarinic or NE/⍺- or β-adrenergic receptors t neuron-target synapse targets smooth and cardiac muscle, some endocrine and exocrine glands, and some adipose tissue neurotransmitters released from varicosities and axon terminals excitatory/inhibitory preganglionic axons, ganglia, and postganglionic neurons found outside of CNS functions: visceral function, including movement in internal organs and secretion, and control of metabolism