Autonomic Nervous System & Higher-Order Brain Functions Overview

What is the primary function of the autonomic nervous system (ANS)?

The ANS controls involuntary functions of visceral effectors such as smooth muscle, glands, and cardiac muscle.

How does the autonomic nervous system differ from the somatic nervous system?

The ANS controls involuntary functions, while the somatic nervous system controls voluntary movements of skeletal muscles.

What are the two main divisions of the autonomic nervous system?

The sympathetic division and the parasympathetic division.

What is the role of the sympathetic division of the ANS?

The sympathetic division prepares the body for 'fight or flight' responses, increasing alertness and metabolic rates.

What is the role of the parasympathetic division of the ANS?

The parasympathetic division promotes 'rest and digest' activities, conserving energy and maintaining resting metabolic rates.

What are preganglionic neurons in the ANS?

Preganglionic neurons have cell bodies in the brainstem and spinal cord and project to autonomic ganglia.

What are postganglionic neurons in the ANS?

Postganglionic neurons have cell bodies in autonomic ganglia and synapse with peripheral target organs.

What neurotransmitter is primarily released by sympathetic preganglionic neurons?

Acetylcholine (ACh) is released at the synapse with postganglionic neurons.

What are the effects of sympathetic activation?

Increased mental alertness, metabolic rate, heart rate, blood pressure, and respiratory rate; reduced digestive and urinary functions.

What are the effects of parasympathetic activation?

Decreased metabolic rate, heart rate, and blood pressure; increased secretion by glands and motility in the digestive tract.

What is dual innervation in the context of the ANS?

Dual innervation refers to the phenomenon where most organs receive input from both sympathetic and parasympathetic divisions, often with opposing effects.

What is autonomic tone?

Autonomic tone is the balance of sympathetic and parasympathetic activity that regulates the function of organs.

What is the significance of visceral reflexes in the ANS?

Visceral reflexes are automatic responses that help maintain homeostasis and regulate bodily functions.

What is the thoracolumbar division of the sympathetic nervous system?

It refers to the origin of sympathetic preganglionic neurons located in the thoracic and lumbar regions of the spinal cord.

What are sympathetic chain ganglia?

Clusters of postganglionic neuron cell bodies located on either side of the vertebral column that innervate various organs.

What types of ganglia are associated with the sympathetic division?

Sympathetic chain ganglia, collateral ganglia, and adrenal medullae.

How do sympathetic preganglionic fibers reach the sympathetic ganglia?

They pass through spinal anterior roots and white rami communicantes.

What is the effect of sympathetic activation on energy reserves?

It activates energy reserves to prepare the body for immediate physical activity.

What is the primary neurotransmitter released by postganglionic sympathetic neurons?

Norepinephrine (NE) is primarily released by postganglionic sympathetic neurons.

What are the effects of aging on the autonomic nervous system?

Aging can lead to decreased responsiveness of the ANS and affect interactions with other organ systems.

What is the role of neurotransmitters in memory formation?

Neurotransmitters influence the processes of creating, storing, and recalling memories.

What is the relationship between the ANS and visceral organs?

The ANS regulates the functions of visceral organs, adapting responses based on the body's needs.

What are collateral ganglia?

Paired or unpaired ganglia located anterior to the vertebral column that are part of the sympathetic division.

Where do preganglionic fibers from the inferior thoracic spinal segments synapse?

At the celiac ganglion or the superior mesenteric ganglion.

What do postganglionic neurons of the sympathetic division innervate?

Abdominopelvic tissues and viscera.

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

It acts as a modified sympathetic ganglion that releases epinephrine and norepinephrine into the bloodstream.

What neurotransmitter do sympathetic preganglionic neurons release?

Acetylcholine (ACh).

What are adrenergic synapses?

Synapses that use norepinephrine (NE) as a neurotransmitter.

What is the role of varicosities in postganglionic neurons?

They store neurotransmitters and branch into telodendria to release them at target organs.

What are the effects of sympathetic activation during a crisis?

Increased energy, blood pressure, heart rate, and mobilization of energy reserves.

What types of receptors bind norepinephrine and epinephrine?

Adrenergic receptors.

What are the two main classes of adrenergic receptors?

Alpha (α) receptors and Beta (β) receptors.

What is the function of Alpha-1 (α1) receptors?

They stimulate smooth muscle contraction and increase intracellular calcium levels.

What is the role of Beta-1 (β1) receptors?

They increase metabolic activity in muscles and the heart.

What do Beta-2 (β2) receptors do?

They trigger relaxation of smooth muscles along the respiratory tract.

What neurotransmitter is primarily released by postganglionic sympathetic neurons?

Norepinephrine (NE).

What is the main function of the parasympathetic division?

To promote rest and digest activities in the body.

Where are the cell bodies of preganglionic neurons in the parasympathetic division located?

In the brainstem and lateral horns of the sacral segments.

What cranial nerves contain parasympathetic fibers?

Cranial nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus).

What neurotransmitter do postganglionic neurons of the parasympathetic division release?

Acetylcholine (ACh).

What is the difference between cholinergic and adrenergic synapses?

Cholinergic synapses use acetylcholine, while adrenergic synapses use norepinephrine.

What is the effect of sympathetic neurotransmitters on target cells?

They cause changes in metabolic activities, often lasting longer than direct sympathetic innervation.

What is the significance of the adrenal medulla's release of hormones?

It enhances and prolongs the effects of sympathetic activation throughout the body.

What is the primary role of the sympathetic division during stress?

To prepare the body for 'fight or flight' responses.

What happens to blood flow and energy use in non-essential organs during sympathetic activation?

Blood flow and energy use are reduced.

What are splanchnic nerves?

Preganglionic fibers that synapse at the inferior mesenteric ganglion.

What is the primary function of postganglionic fibers from the celiac ganglia?

To innervate the stomach, liver, gallbladder, pancreas, and spleen.

What is the primary function of the vagus nerve in the parasympathetic division?

The vagus nerve provides 75% of all parasympathetic output.

Where do the pelvic nerves synapse in the parasympathetic division?

They synapse at intramural ganglia in the walls of the kidneys, urinary bladder, terminal portion of the large intestine, and sex organs.

What are the two types of ganglia in the parasympathetic division?

Terminal ganglia, which are near the target organ, and intramural ganglia, which are embedded in the tissues.

What are the major effects of parasympathetic activation?

1. Constriction of pupils and focusing on near objects. 2. Secretion by digestive glands. 3. Increased smooth muscle activity along the digestive tract. 4. Stimulation of defecation and contraction of the urinary bladder during urination.

What neurotransmitter is released by all parasympathetic neurons?

Acetylcholine (ACh).

How is acetylcholine inactivated in the parasympathetic system?

Most ACh is inactivated at the synapse by acetylcholinesterase (AChE), and ACh that diffuses into surrounding tissues is inactivated by tissue cholinesterase.

What are the two types of cholinergic receptors in the parasympathetic division?

Nicotinic receptors and muscarinic receptors.

Where are nicotinic receptors located?

On postganglionic neurons of both the sympathetic and parasympathetic divisions.

What is the function of muscarinic receptors?

They are located at target organs and tissues of the parasympathetic division and are G protein-coupled receptors that can have excitatory or inhibitory responses.

What is dual innervation?

Most vital organs are innervated by both the sympathetic and parasympathetic divisions, often with opposing effects.

What is the role of the cardiac plexus?

It is a nerve network in the thoracic cavity made by sympathetic and parasympathetic fibers that innervate the heart.

How does the parasympathetic division affect heart rate?

ACh released by parasympathetic postganglionic fibers slows the heart rate.

How does the sympathetic division affect heart rate?

Norepinephrine (NE) released by sympathetic postganglionic fibers accelerates the heart rate.

What is the significance of the esophageal plexus?

It is formed by the parasympathetic descending branches of the vagus nerves and sympathetic splanchnic nerves, innervating the esophagus.

What does the celiac plexus innervate?

It innervates abdominal viscera and contains fibers from the esophageal plexus.

What is the function of the inferior mesenteric plexus?

It innervates visceral organs of the abdominal cavity.

What is the role of the hypogastric plexus?

It innervates digestive, urinary, and reproductive organs of the pelvic cavity.

What are the cranial nerves associated with the parasympathetic division?

Cranial nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus).

What is the difference in divergence between the sympathetic and parasympathetic divisions?

The sympathetic division has extensive divergence, while the parasympathetic division has much less divergence.

What happens during nicotine poisoning?

It results from widespread exacerbated autonomic activation and may lead to coma or death.

What is muscarine and its source?

Muscarine is a toxin produced by some poisonous mushrooms that binds to muscarinic receptors.

What division of the autonomic nervous system dominates at rest?

The parasympathetic division

What effect does a crisis have on heart rate?

It speeds the heart rate by stimulating sympathetic and inhibiting parasympathetic nerves.

Which organs are innervated by only one division of the autonomic nervous system?

Blood vessels, which are only under sympathetic control.

What neurotransmitter is released from sympathetic fibers at smooth muscle cells in blood vessel walls?

Norepinephrine (NE)

What is the role of sympathetic tone in blood vessels?

It keeps muscles partially contracted.

What happens when more blood flow is needed in blood vessels?

The rate of NE release decreases, stimulating sympathetic cholinergic fibers, causing smooth muscle relaxation and dilation.

What are visceral reflexes?

Autonomic polysynaptic reflexes that provide automatic motor responses in glands and nonskeletal muscle organs.

Which higher center can modify visceral reflexes?

The hypothalamus

What are the components of a visceral reflex arc?

Receptor, sensory neuron, processing center (interneurons), two visceral motor neurons (preganglionic and postganglionic), and peripheral effector.

What are long reflexes in the autonomic nervous system?

Reflexes that coordinate the activities of an entire organ.

What are short reflexes in the autonomic nervous system?

Reflexes that bypass the CNS and control activity in one part of an organ.

What is the enteric nervous system?

A system capable of controlling digestive functions independent of the CNS.

What brain structure coordinates complex reflexes in the autonomic nervous system?

The medulla oblongata

What are the three characteristics of higher-order functions?

They require the cerebral cortex, involve conscious and unconscious information processing, and are subject to adjustment over time.

What are fact memories?

Specific bits of factual information.

What are skill memories?

Learned motor behaviors incorporated at an unconscious level with repetition.

What is memory consolidation?

The process of converting a short-term memory into a long-term memory.

What are short-term memories?

Memories that do not last long but can be recalled immediately.

What are tertiary memories?

Long-lasting memories that do not fade over time.

Which brain regions are essential for memory consolidation?

The amygdaloid body and hippocampus.

What happens if the hippocampus is damaged?

Inability to form new long-term memories, but existing long-term memories remain intact.

What role does the nucleus basalis play in memory?

It plays an uncertain role in memory storage and retrieval.

Which part of the brain is involved in the integration of autonomic and somatic nervous system activities?

The brainstem.

What is the primary function of the long-term memory store?

It stores most long-term memories.

Which brain regions are crucial for memory of faces, voices, and words?

Portions of the occipital and temporal lobes.

What is a memory engram?

A single circuit that corresponds to a single long-term memory, formed as a result of experience and repetition.

What factors affect the formation of memory engrams?

The nature, intensity, and frequency of the original stimulus, as well as the activity of the hippocampus and drugs that stimulate the CNS.

What neurotransmitter is linked to memory formation and is affected by NMDA receptors?

Glutamate.

What happens when NMDA receptors are blocked?

Long-term memory formation is prevented.

What characterizes the conscious state?

An awareness of and attention to external events and stimuli.

What occurs during deep sleep?

The entire body relaxes, and cerebral cortex activity is at a minimum.

What is REM sleep, and what occurs during this state?

Rapid eye movement sleep where active dreaming occurs, and muscle tone decreases markedly.