Human Physiology - Organ Innervation
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Questions and Answers

Which type of innervation do most organs receive?

  • Only sympathetic innervation
  • Both sympathetic and parasympathetic innervation (correct)
  • Neither sympathetic nor parasympathetic innervation
  • Only parasympathetic innervation

What distinguishes certain organs from others regarding innervation?

  • Some organs receive both types of innervation while others do not (correct)
  • Only parasympathetic innervation is necessary for organ function
  • Only organs with sympathetic innervation can function properly
  • All organs require sympathetic innervation only

Which of the following statements is false regarding organ innervation?

  • Some organs have only sympathetic innervation
  • All organs receive both sympathetic and parasympathetic innervation (correct)
  • Certain organs may lack one type of innervation entirely
  • Some organs have only parasympathetic innervation

Why might an organ have only one type of innervation?

<p>It may only require a single type of regulation (D)</p> Signup and view all the answers

Which center is responsible for regulating blood vessel diameter?

<p>Vasomotor center (B)</p> Signup and view all the answers

Which of the following functions is NOT associated with the medulla?

<p>Pneumotaxic regulation (C)</p> Signup and view all the answers

What is the primary role of the pneumotaxic center?

<p>Controlling the rhythm of breathing (D)</p> Signup and view all the answers

Which of the following centers are involved in autonomic responses such as coughing and vomiting?

<p>Medulla and pons centers (A)</p> Signup and view all the answers

Which center specifically oversees the coordination of breathing during activities such as speaking?

<p>Pneumotaxic center (C)</p> Signup and view all the answers

What phenomenon occurs when the number of receptors in post-synaptic membranes increases?

<p>Up-regulation (C)</p> Signup and view all the answers

What is one proposed cause of denervation super-sensitivity?

<p>Increased number of post-synaptic receptors (B)</p> Signup and view all the answers

Which neurotransmitters are mentioned in relation to denervation super-sensitivity?

<p>Nor-adrenaline and acetylcholine (A)</p> Signup and view all the answers

What happens to receptor numbers when nor-adrenaline or acetylcholine is no longer released?

<p>They increase (C)</p> Signup and view all the answers

Which statement about denervation super-sensitivity is correct?

<p>It can occur due to increased post-synaptic receptor numbers. (D)</p> Signup and view all the answers

Which of the following locations does not contain α1 receptors?

<p>Liver (A)</p> Signup and view all the answers

What action is primarily produced by α1 receptors?

<p>Contraction of vascular smooth muscle (B)</p> Signup and view all the answers

Which metabolic process is associated with α1 receptor activation?

<p>Glycogenolysis (C)</p> Signup and view all the answers

Which neurotransmitter is equally effective at activating α1 receptors?

<p>Norepinephrine (C)</p> Signup and view all the answers

Which of the following is NOT a function produced by α1 receptors?

<p>Glucose uptake (C)</p> Signup and view all the answers

What type of receptors are M2 and M4 receptors associated with?

<p>Gi/s proteins (B)</p> Signup and view all the answers

Which second messengers are associated with the activation of phospholipase C?

<p>IP3 and DAG (C)</p> Signup and view all the answers

What is the function of adenyl cyclase in cellular signaling?

<p>To convert ATP to cAMP (D)</p> Signup and view all the answers

What occurs as a result of upregulation of cyclic AMP (cAMP)?

<p>Enhanced cellular response and activity (A)</p> Signup and view all the answers

What role does downregulation of signaling molecules generally play in cells?

<p>Decreases cellular sensitivity to signals (B)</p> Signup and view all the answers

What is the primary function of tone in the nervous system?

<p>To allow the nervous system to influence organ activity by adjusting stimulation levels (C)</p> Signup and view all the answers

How does tone affect the activity of organs?

<p>It allows for both enhancement and reduction of activity in response to stimuli (B)</p> Signup and view all the answers

Which statement best describes the relationship between tone and organ stimulation?

<p>Tone allows for dynamic regulation of organ activity by varying stimulation (B)</p> Signup and view all the answers

What misconception may arise regarding the role of tone in the nervous system?

<p>That tone only works in emergency situations (B)</p> Signup and view all the answers

Which of the following best describes the nervous system's control over organs via tone?

<p>It can finely tune the level of stimulation to suit various physiological needs (D)</p> Signup and view all the answers

Flashcards

Dual Innervation

The nervous system controls body functions through two main branches: the sympathetic and parasympathetic nervous systems.

Sympathetic Nervous System

Sympathetic nervous system activation prepares the body for 'fight or flight' response.

Parasympathetic Nervous System

Parasympathetic nervous system promotes 'rest and digest' functions.

Single Innervation

Some organs receive nerve signals from only one branch of the nervous system.

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Examples of Single Innervation

Examples include sweat glands and blood vessels, which are mainly controlled by the sympathetic nervous system.

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Alpha-1 (α1) Receptors

A type of adrenergic receptor primarily found in smooth muscle, notably in the skin, splanchnic region, GI tract, bladder sphincters, iris, and heart. It is associated with excitation.

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What is the primary function of α1 receptors?

They are responsible for initiating a response that leads to contraction or constriction in the target tissue.

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α1 Receptor Sensitivity

Alpha-1 Receptors are equally responsive to both norepinephrine (noradrenaline) and epinephrine (adrenaline).

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α1 Receptor role in glucose metabolism

α1 Receptors play a role in glycogenolysis (breakdown of glycogen) and gluconeogenesis (production of glucose) within the body.

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Where are α1 receptors located?

α1 Receptors are found in various locations, including the skin, digestive system, bladder, and heart.

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Vasomotor center

Part of the brainstem responsible for regulating blood vessel diameter, hence blood pressure.

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Respiratory center

Part of the brainstem that controls the rhythm and depth of breathing.

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Swallowing center

Part of the brainstem that coordinates muscle movements for swallowing, ensuring food and liquid go down the esophagus.

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Coughing center

Part of the brainstem that coordinates coughing, a reflex to clear the airway.

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Vomiting center

Part of the brainstem that coordinates vomiting, a reflex to expel stomach contents.

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Phospholipase C (PLC)

A type of enzyme that splits phospholipids, like PIP2, into two signaling molecules: IP3 and DAG.

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Inositol Triphosphate (IP3)

A second messenger molecule that binds to receptors on the endoplasmic reticulum, causing the release of calcium ions into the cytoplasm.

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Diacylglycerol (DAG)

A second messenger molecule that activates protein kinase C, leading to downstream signaling events.

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Gi/s protein

A type of G protein associated with the M2 and M4 muscarinic acetylcholine receptors, sometimes referred to as inhibitory G proteins because they can suppress the activity of adenylate cyclase.

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Adenyl Cyclase

An enzyme that catalyzes the conversion of ATP to cAMP, which is an important second messenger involved in various cellular signaling pathways.

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Tone

The ability of a single nervous system to both increase and decrease the activity of a stimulated organ.

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Increase in Tone

A nervous system can activate an organ to a greater degree.

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Decrease in Tone

A nervous system can reduce the activity of an organ.

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Nervous System Control

The process involving a nervous system controlling an organ.

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Stimulated Organ

The organ receiving instructions from the nervous system.

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Denervation supersensitivity

When a synapse is no longer receiving neurotransmitters (like norepinephrine or acetylcholine), the target cells increase the number of receptors on their surface. This is called 'up-regulation' and it makes the cells more sensitive to any remaining neurotransmitter.

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Up-regulation

The increase in the number of receptors on the surface of a cell, in response to reduced stimulation.

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Neurotransmitters

Norepinephrine and acetylcholine are two chemical messengers that transmit signals in the nervous system.

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Synapse

A synapse is a specialized junction where communication occurs between neurons or between a neuron and its target cell (e.g., muscle cell).

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Neurons

These are specialized cells that receive and transmit signals in the nervous system.

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Study Notes

Autonomic Nervous System (ANS)

  • The autonomic nervous system is a network of pathways that connect the central nervous system (CNS) to various organs.
  • It regulates smooth muscle, cardiac muscle, and glands.
  • A major role of the ANS is homeostasis.
  • ANS output to visceral organs is continuous (tonic), unlike somatic nervous system output to skeletal muscle (phasic).
  • ANS activity adjusts to anticipated demands.

Characteristics of the ANS

  • The ANS is marked by rapid and intense changes in visceral functions.
  • For example, heart rate can double within 3-5 seconds.
  • The ANS has three divisions: sympathetic, parasympathetic, and enteric.

Organization of ANS Output

Sympathetic Nervous System

  • Characterized by extensive branching (1:20).
  • Action is diffuse (generalized).
  • Functions involve catabolic processes (expenditures).
  • Has specific effects on target organs.

Parasympathetic Nervous System

  • Characterized by limited branching (1:1).
  • Action is discrete (localized).
  • Functions involve anabolic processes (conservation and restoration).
  • Has specific effects on target organs.

Synaptic Organization

  • Synapses are formed in ganglia.
  • Parasympathetic ganglia often lie close to effector organs.
  • Sympathetic ganglia are located along the paravertebral chain.

Pre-ganglionic Neurons

  • Sympathetic pre-ganglionic neurons originate in the spinal cord (thoracic and lumbar regions).
  • Parasympathetic pre-ganglionic neurons originate in the brain stem and sacral spinal cord.
  • Sympathetic fibers are usually short and myelinated.
  • Parasympathetic fibers are usually long and myelinated.

Post-ganglionic Neurons

  • Post-ganglionic neurons are located in autonomic ganglia.
  • Sympathetic post-ganglionic fibers are typically long and unmyelinated.
  • Release nor-epinephrine (typically).
  • Parasympathetic post-ganglionic fibers are typically short and unmyelinated.
  • Release acetylcholine.

Role of the Adrenal Medulla

  • The adrenal medulla acts as a sympathetic ganglion.
  • Cells in the adrenal medulla secrete nor-epinephrine and epinephrine into the bloodstream.
  • These hormones mimic the direct effects of the sympathetic nervous system.
  • Nor-epinephrine and epinephrine's effects last longer than direct sympathetic stimulation.

Neurotransmitters of the ANS

  • Adrenergic neurons: release nor-epinephrine.
  • Cholinergic neurons: release acetylcholine.

Cholinergic Receptors

  • Nicotinic receptors: are ion channels and stimulate excitation.
  • Found at neuromuscular junctions and within the ganglia of the autonomic nervous system.

Muscarinic Receptors

  • Are G protein-coupled receptors and can cause excitation or inhibition.
  • Found in many locations throughout the body.

Beta Receptors

  • Are found in the sinoatrial (SA) node, atrioventricular (AV) node, ventricular muscle, and juxta-glomerular cells.
  • Produce excitation through Gs protein and elevation of cAMP
  • Includes B1, B2, and B3 subtypes

Alpha Receptors

  • Are present on vascular smooth muscle, the gastrointestinal tract, bladder sphincters, and the iris radial muscles.
  • Produce excitation and/or contraction through Gq proteins, influencing intracellular calcium levels.
  • Includes alpha 1 and alpha 2 subtypes
  • Alpha 2 receptors produce inhibition.

ANS Function Examples

  • Cholinergic functions: digestive processes; homeostasis processes like food, sleep menstration, bladder, and sexual activity.
  • Nor-adrenergic functions: emergency/stress responses; elevate glucose/fatty acids for rapid energy; pupils dilate for light; blood pressure accelerates for perfusion; blood vessels in skin contract for reduced blood loss.

Denervation Supersensitivity

  • Increased sensitivity of effector organs to neurotransmitters following nerve damage or removal.
  • Characterized by an exaggerated response to neurotransmitters, generally.

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Autonomic Nervous System (ANS) PDF

Description

Test your knowledge on the innervation of organs in the human body with this quiz. Explore the distinctions between different organ innervation types, their functions, and the centers that regulate physiological responses. This quiz addresses key concepts in understanding the autonomic nervous system and its influence on organ function.

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