The Peripheral Nervous System: Efferent Division-->The Autonomic Nervous System

What are the two efferent divisions of the peripheral nervous system?

The autonomic nervous system and the somatic nervous system.

How does the autonomic nervous system differ from the somatic nervous system in terms of voluntary control?

The autonomic nervous system is involuntary, while the somatic nervous system is voluntary.

What is the typical length of axons in the autonomic nervous system compared to the somatic nervous system?

The autonomic nervous system often has multiple neurons in its efferent pathway, while the somatic nervous system typically has a single neuron.

What types of effector organs are controlled by the autonomic nervous system?

Smooth muscle, cardiac muscle, and glands.

What neurotransmitter is commonly released by the sympathetic division?

Norepinephrine, although acetylcholine is released at the ganglia.

What neurotransmitter is primarily released by the parasympathetic division?

Acetylcholine.

What is the response of target organs when activated by the sympathetic nervous system?

Typically, it prepares the body for 'fight or flight' responses.

What is the response of target organs when activated by the parasympathetic nervous system?

Typically, it promotes 'rest and digest' activities.

What is antagonistic control in the context of the autonomic nervous system?

It refers to the opposing effects of the sympathetic and parasympathetic systems on the same organ.

How does epinephrine affect blood vessels differently?

It causes some blood vessels to constrict and others to dilate depending on the type of adrenergic receptor activated.

What anatomical differences exist between sympathetic and parasympathetic pathways?

Sympathetic pathways originate in the thoracolumbar region, while parasympathetic pathways originate in the craniosacral region.

Which cranial nerve is the primary parasympathetic tract?

The vagus nerve (Cranial Nerve X).

What are the targets of autonomic neurons?

Smooth muscle, cardiac muscle, and glands.

What is the first step in neurotransmitter release at the neuromuscular junction?

The arrival of an action potential at the axon terminal.

What enzyme deactivates acetylcholine at the neuromuscular junction?

Acetylcholinesterase.

How many subtypes of muscarinic receptors are there?

There are five subtypes of muscarinic receptors (M1 to M5).

What is the role of the adrenal medulla in the sympathetic nervous system?

It releases catecholamines (epinephrine and norepinephrine) into the bloodstream during stress responses.

What is the Renin-Aldosterone-Angiotensin system's role in the sympathetic nervous system?

It regulates blood pressure and fluid balance in response to sympathetic activation.

What body functions are exclusively controlled by the sympathetic nervous system?

Functions such as fight or flight responses, including increased heart rate and blood flow to muscles.

Give an example of cooperation between the sympathetic and parasympathetic nervous systems.

During sexual arousal, the parasympathetic system promotes blood flow, while the sympathetic system facilitates ejaculation.

What does the autonomic nervous system (ANS) innervate?

Smooth and cardiac muscle, glands, and adipose tissue.

What are the two main subdivisions of the nervous system?

Central nervous system (CNS) and peripheral nervous system (PNS).

What are the two divisions of the peripheral nervous system?

Sensory division and motor division.

What are the two types of motor divisions in the peripheral nervous system?

Somatic nervous system (SNS) and autonomic nervous system (ANS).

How do the ANS and SNS differ in terms of effectors?

SNS affects skeletal muscle (voluntary), while ANS affects cardiac and smooth muscle, and glands (involuntary).

What is the structure of the efferent pathways in the SNS?

The SNS has a single neuron extending from the CNS to the effector.

What is the structure of the efferent pathways in the ANS?

The ANS uses a two-neuron chain: preganglionic and postganglionic neurons.

What neurotransmitter is released by the preganglionic neurons in the ANS?

Acetylcholine (ACh).

What are the primary neurotransmitters used by postganglionic neurons in the ANS?

Norepinephrine (NE) or Acetylcholine (ACh).

What are the two divisions of the ANS?

Sympathetic division and parasympathetic division.

What is the primary function of the sympathetic division?

Mobilizes the body during extreme situations (fight-or-flight response).

What activities are associated with the parasympathetic division?

Maintenance activities such as digestion, defecation, and diuresis (rest-and-digest).

What is the role of norepinephrine in the sympathetic division?

It acts as the primary postganglionic transmitter via adrenergic receptors.

How does the sympathetic division affect heart rate and digestion?

It increases heart rate and inhibits digestion.

What is the effect of parasympathetic tone on the heart and digestive systems?

It slows the heart and dictates normal activity levels of the digestive and urinary systems.

What are the structural similarities between the sympathetic and parasympathetic divisions?

Both originate in the CNS and have preganglionic and postganglionic fibers.

What are the structural differences in the preganglionic fibers of the sympathetic and parasympathetic divisions?

Sympathetic fibers exit via thoracic and lumbar spinal nerves; parasympathetic fibers exit via cranial nerves and sacral spinal nerves.

What is the role of the adrenal medulla in the sympathetic division?

It secretes epinephrine (EPI) and norepinephrine (NE) into the blood during sympathetic activation.

What is the significance of divergence and convergence in the sympathetic division?

Divergence allows one preganglionic neuron to synapse on several postganglionic neurons, while convergence allows several preganglionic neurons to synapse on one postganglionic neuron.

What is the function of white and gray rami communicantes?

White rami carry myelinated preganglionic sympathetic axons to the trunk; gray rami carry unmyelinated postganglionic sympathetic axons from the trunk to spinal nerves.

What is the effect of denervation in the SNS?

It leads to paralysis.

What is the effect of denervation in the ANS?

It results in denervation hypersensitivity.

What neurotransmitter is released by all preganglionic neurons?

Acetylcholine (ACh).

What is the role of the chromaffin cell in the adrenal medulla?

It acts as a modified postganglionic sympathetic neuron, secreting epinephrine into the blood.

What are the two types of cholinergic receptors?

Nicotinic (Nn and Nm) and Muscarinic (M1-M5)

Where are nicotinic receptors found?

Neuromuscular junctions, all postganglionic cell bodies of both sympathetic and parasympathetic divisions, and cells of the adrenal medulla.

What type of receptors are nicotinic receptors?

Ligand-gated ion channels

What is the effect of ACh binding to nicotinic receptors?

Always stimulatory

What type of receptors are muscarinic receptors?

G-protein coupled receptors

What is the effect of ACh binding to muscarinic receptors?

Can be either inhibitory or excitatory, depending on the receptor subtype.

What are the responses of nicotinic receptors in skeletal muscle?

Depolarization, producing action potentials and muscle contraction.

What is the response of muscarinic receptors in smooth muscle and glands?

Depolarization and contraction of smooth muscle, secretion of glands.

What is the effect of ACh on muscarinic M2 receptors in the heart?

Hyperpolarization, slowing the rate of spontaneous depolarization.

What neurotransmitters are primarily used in the sympathetic nervous system?

Norepinephrine (NE) and sometimes Dopamine (DA).

What are the two types of adrenergic receptors?

Alpha (α1 and α2) and Beta (β1, β2, and β3)

What is the primary function of α1 adrenergic receptors?

Vasoconstriction in most blood vessels and pupil dilation.

What is the function of α2 adrenergic receptors?

Inhibition of norepinephrine release and regulation in the CNS and pancreas.

What is the role of β1 adrenergic receptors?

Increase heart contraction and release of renin from the kidneys.

What is the effect of β2 adrenergic receptors on blood vessels and lungs?

Vasodilation in blood vessels to skeletal muscle and bronchodilation in the lungs.

What is the role of β3 adrenergic receptors?

Triglyceride breakdown in adipose tissue and relaxation of the urinary bladder.

What are adrenergic agonists?

Drugs that promote the process stimulated by norepinephrine.

What are adrenergic antagonists?

Drugs that block the action of norepinephrine.

What is the mechanism of action for catecholamines?

binding to specific G-protein coupled receptors, primarily on the surface of target cells, to trigger intracellular signaling cascades

How are catecholamines metabolized?

By enzymes COMT (catechol-o-methyl transferase) and MAO (monoamine oxidase).

What is the significance of sympathetic tone?

It maintains blood vessels in a state of partial constriction, regulating blood pressure.

What physiological effects does the sympathetic division control?

Thermoregulation, release of renin from kidneys, and metabolic effects.

What happens to blood vessels during low temperature?

Constriction of blood vessels to retain blood in deeper vital organs.

What is the effect of norepinephrine compared to acetylcholine?

Norepinephrine is inactivated more slowly than ACh and acts via a second-messenger system.

What is the effect of fever on blood vessels?

Widespread dilation of blood vessels to bring warm blood to the surface.

What are the therapeutic uses of adrenergic agonists?

Used for conditions like hypertension, asthma, and cardiac issues.

What are the three main methods of neurotransmitter termination in the synapse?

1. Diffusion away from the synapse

2. Reuptake into neurons by presynaptic transporters

3. Uptake into glia or smooth muscle.

Which enzymes metabolize catecholamines?

Catecholamines are metabolized by COMT (catechol-o-methyl transferase) and MAO (monoamine oxidase).

Why do norepinephrine (NE) and epinephrine (EPI) have long-lasting effects?

NE is inactivated more slowly than ACh, is an indirectly acting neurotransmitter using a second-messenger system, and EPI is released into the blood, remaining until destroyed by the liver.

What physiological activities are controlled by the sympathetic division?

The sympathetic division controls thermoregulation, release of renin from the kidneys, and various metabolic effects.

How does the sympathetic division respond to low temperatures?

It causes blood vessel constriction to retain blood in deeper vital organs.

What are the metabolic effects of the sympathetic division that are not reversed by the parasympathetic division?

Increased metabolic rate, elevated blood glucose levels, mobilization of fat as a food source, and stimulation of the reticular activating system for increased mental alertness.

What is sympathetic tone and its role in blood pressure regulation?

Sympathetic tone maintains blood vessels in a state of partial constriction, increasing blood pressure as needed and prompting dilation to decrease blood pressure.

What is the origin of the sympathetic nervous system?

The sympathetic nervous system originates from the thoraco-lumbar region of the spinal cord.

What neurotransmitter is primarily used by the parasympathetic nervous system?

Acetylcholine.

What are the receptor types associated with the sympathetic nervous system?

Adrenergic receptors: Alpha (α), Beta (β), and Dopamine.

What is the main integration center of autonomic nervous system activity?

The hypothalamus.

What characterizes visceral reflexes compared to somatic reflexes?

Visceral reflexes are always polysynaptic pathways.

What are the effects of the sympathetic division on the heart?

Increases heart rate and contractility.

What is the effect of the parasympathetic division on the gastrointestinal tract?

It contracts smooth muscle and relaxes sphincters, stimulating secretion.

What is the role of the adrenal medulla in the sympathetic nervous system?

It releases hormones that facilitate mass activation of the sympathetic response.

What are common disorders resulting from poor control of smooth muscle activity?

Hypertension, excessive sympathetic stimulation leading to vasospasms, and autonomic neuropathy.

What is orthostatic hypotension?

Excessive decrease in blood pressure when a person stands.

What symptoms are associated with sympathetic nervous system disorders?

Ptosis, miosis, anhydrosis, facial flushing, erectile dysfunction, and urinary issues.

What is the effect of the sympathetic division on blood vessels during stress or exercise?

It causes vasoconstriction in skin vessels to minimize bleeding and shunts blood to more needed areas.

What are the effects of the parasympathetic division on the eye?

Contracts the circular muscle to constrict the pupil.

What is the role of baroreceptors in blood pressure regulation?

They detect increased blood pressure and send signals to the CNS to decrease heart rate.

What is the function of autonomic varicosities?

They release neurotransmitters over the surface of target cells.

What is the effect of the sympathetic division on the bladder?

It causes slight relaxation of the bladder wall and contraction of the urethral sphincter.

What is the primary method of terminating neurotransmission in the parasympathetic nervous system?

Inactivation by acetylcholinesterase.

How does the sympathetic division affect blood vessels in skeletal muscles?

It causes vasodilation to increase blood flow during emergencies.

What is the significance of the reticular activating system (RAS) in the sympathetic response?

It increases mental alertness.

What are the effects of sympathetic stimulation on sweat glands?

Increases thermoregulatory sweating.

What are the primary effectors of the somatic nervous system?

Skeletal muscles.

What are the primary effectors of the autonomic nervous system?

Cardiac and smooth muscles, organs (viscera), and glands.

How do the efferent pathways differ between the SNS and ANS?

SNS has one neuron per muscle innervated, while ANS has two neurons separated by a ganglia (preganglionic and postganglionic neurons).