Physiology of Eating and Hunger Control

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Questions and Answers

What is the primary effect of sympathetic activation on salivary secretion?

It increases secretion variety.

It provides a copious saliva output.

It maintains high protein levels.

It reduces saliva output. (correct)

Which of the following describes the composition of saliva secreted by the parasympathetic system?

Protein poor with high K and HCO3 levels.

Protein rich with lower K and HCO3 levels.

Protein poor with lower K and HCO3 levels. (correct)

Protein rich with high K and HCO3 levels.

What happens to salivation after denervation of the salivary glands?

There is a transient increase in secretion.

There is no effect on secretion.

Secretion increases significantly.

Secretion decreases, leading to glandular atrophy. (correct)

Which factor is likely to cause dryness of the mouth during sleep?

Decreased salivation. Signup and view all the answers

What physiological change occurs when patients experience anxiety or stress?

Decreased saliva production. Signup and view all the answers

Which center is NOT among those in the medulla relevant to parasympathetic regulation?

Digestive center. Signup and view all the answers

Why do dental procedures tend to stimulate salivation?

They activate unconditioned salivary reflexes. Signup and view all the answers

How does atropine affect salivary glands?

It blocks acetylcholine effects, reducing secretions. Signup and view all the answers

Which gland is primarily responsible for saliva production during the unstimulated phase?

Submandibular gland Signup and view all the answers

What type of glands are the submandibular and sublingual glands classified as?

Mixed serous and mucous glands Signup and view all the answers

What is the primary role of angiotensin II in fluid regulation?

Activating the thirst center Signup and view all the answers

Which structure is NOT part of the secretory unit of salivary glands?

Otic ganglion Signup and view all the answers

How does the blood flow to salivary glands compare to other glands?

Higher blood flow proportional to weight Signup and view all the answers

Which gland contributes the least to overall saliva production?

Sublingual gland Signup and view all the answers

What is the correct statement regarding the parotid glands?

They are histologically serous type. Signup and view all the answers

What occurs during hemorrhage related to fluid intake?

Increased drinking despite unchanged osmolality. Signup and view all the answers

What is released by exocytosis in response to secretagogues from mucous cells?

Mucin Signup and view all the answers

Which compound is oxidized by peroxidases found in human saliva, tears, and milk?

Thiocyanate (SCN) Signup and view all the answers

How much can the parotid gland concentrate thiocyanate (SCN)?

What type of stimulation primarily controls salivary gland function?

Autonomic nervous system Signup and view all the answers

Which nervous system has a stronger effect on salivary secretion?

Parasympathetic nervous system Signup and view all the answers

What type of substances are secreted by the exocrine glands mentioned?

Oxidants Signup and view all the answers

What occurs to blood vessels during powerful sympathetic stimulation to the salivary glands?

Constriction Signup and view all the answers

What happens to saliva output after initial stimulation of the glands?

It rapidly decreases Signup and view all the answers

What role does glucosyl transferase (GTF) play in dental caries?

It converts sugar into a sticky substance that helps bacteria adhere to teeth. Signup and view all the answers

What is one consequence of the formation of plaque on teeth?

It promotes bacterial production of an enzyme that erodes enamel. Signup and view all the answers

Which factor can contribute to xerostomia (dry mouth)?

Medications that decrease salivary flow. Signup and view all the answers

What is the primary function of salivary amylase?

To hydrolyze polysaccharides such as starch. Signup and view all the answers

Why does salivary amylase have a minor role in carbohydrate digestion?

It is inactivated quickly after food enters the stomach. Signup and view all the answers

What percentage of starch can be digested to the disaccharide stage by amylase in the mouth, when food is chewed for an extended period?

75 percent Signup and view all the answers

What is one of the essential functions of saliva aside from digestion?

Facilitating taste sensation. Signup and view all the answers

Which of the following is NOT a role of saliva?

Promoting bacteria growth. Signup and view all the answers

What is the primary function of the masseter muscle in the process of digestion?

To crush and break food. Signup and view all the answers

Which nerve is primarily associated with the intrinsic and extrinsic muscles of the tongue during swallowing?

CN-XII (Hypoglossal) Signup and view all the answers

What triggers the involuntary phase of swallowing once the food reaches the pharynx?

Stimuli from swallowing receptor areas. Signup and view all the answers

During the voluntary stage of swallowing, what action does the tongue perform?

It pushes food upwards and backwards. Signup and view all the answers

Which muscle group is involved in the automatic contractions during the pharyngeal phase of swallowing?

Pharyngeal constrictor muscles. Signup and view all the answers

Which of the following substances is known to increase lower esophageal sphincter pressure?

Motilin Signup and view all the answers

What is the role of the pterygoid muscles in the digestion process?

To elevate the mandible for chewing. Signup and view all the answers

Which condition is primarily characterized by food accumulation and massive dilation in the esophagus?

Achalasia Signup and view all the answers

Which of the following occurs as a result of the bolus of food entering the pharynx?

Muscular contractions become automatic. Signup and view all the answers

What mechanism is suggested for the esophageal motility issues seen in achalasia?

Decrease in myenteric plexus activity Signup and view all the answers

What is the primary purpose of saliva in the digestive process?

To mix with food and begin digestion. Signup and view all the answers

Which of the following is NOT a treatment option for achalasia?

Medication with peppermint Signup and view all the answers

What does the term 'dilated esophagus' refer to in the context of achalasia?

Widening of the esophagus due to trapped food Signup and view all the answers

Which nerve is primarily involved in the conditions affecting the lower esophageal sphincter in achalasia?

Vagus nerve Signup and view all the answers

What role does gastrin play in the context of lower esophageal sphincter pressure?

It contributes to increasing lower esophageal sphincter pressure. Signup and view all the answers

Which of the following factors is not associated with decreasing lower esophageal sphincter pressure?

Prostaglandins Signup and view all the answers

Study Notes

Eating: Salivation, Mastication, and Deglutition

This topic covers the physiological processes of eating, including salivation, mastication (chewing), and deglutition (swallowing).

Physiology of Hunger

Hunger: A craving for food, associated with objective sensations like pangs, increased salivation, and food-searching behavior.
Appetite: Preferences for specific foods that may persist even after satiety has been achieved.
Satiety: The feeling of fullness that occurs after eating, reducing the desire for food.
Anorexia: Aversion to eating despite hunger cues.

Central Control

Higher centers (prefrontal cortex and amygdala) are involved in habit, conditioning, and the overall control of food intake.
The hypothalamus plays a crucial role in regulating appetite through interactions between its various areas.
Key areas within the hypothalamus include the ventromedial and ventrolateral nuclei.

Feedback Control

Short-term feedback: Oral activity (chewing, tasting, swallowing) inhibits the feeding center. Stomach or duodenal distension also inhibits the feeding center. Chemical components of food (e.g., hormones like CCK, GRP, GLP-1, somatostatin, insulin, and glucagon) inhibit food intake.
Long-term feedback: Temperature (cold stimulates feeding, heat inhibits), and blood nutrient concentrations (low glucose, amino acids, and lipids stimulate more feeding, while high levels of these promote satiety) influence food intake. Adipose tissue (fat stores) influence feeding through leptin.

Salivary Glands

Parotid glands: Serous type, major contributor to saliva flow in stimulated phases.
Submandibular and sublingual glands: Mixed serous and mucous types, major contributors in unstimulated phases.
Buccal and labial glands: Mixed types.
Saliva contains various proteins, including alpha-amylase (ptyalin), lingual lipase, and antibacterial agents (muramidase, lysozyme).

Nervous Regulation of Salivary Secretion

The autonomic nervous system (sympathetic and parasympathetic) regulates salivary gland function.
Stimulation of both sympathetic and parasympathetic nerves increases secretions, but parasympathetic effects are more prolonged.

Regulation of Fluid Intake

The thirst center in the hypothalamus (supraoptic area) regulates fluid intake.
Input from the renin-angiotensin system and extracellular fluid volume and osmolality are significant factors in initiating thirst.

Digestion in the Mouth and Oropharynx

Mastication: Crushing and breaking food into smaller pieces, increasing its surface area for digestion and better mixing with saliva.
Swallowing (Deglutition): Three stages: (1) voluntary stage (tongue pushes food back), (2) pharyngeal stage (involuntary reflexive movements pushing food down), and (3) esophageal stage (involuntary peristalsis moves food to stomach).

Esophagus

Lower esophageal sphincter (LES): Thickened portion of esophageal circular muscle near the stomach, crucial to prevent gastric reflux.
Peristalsis: Wave-like contractions that push food through the esophagus.
Primary and secondary peristalsis: Primary peristalsis follows pharyngeal swallowing, and secondary peristalsis occurs if the primary wave is incomplete.

Stomach

Stomach contents are highly acidic and contain proteolytic enzymes. Esophageal mucosa (except lower 1/8) can’t withstand these contents; the lower esophageal sphincter prevents reflux when working correctly.

Disorders of the Esophagus

Achalasia: Impaired relaxation of the lower esophageal sphincter (LES), resulting in food accumulation and esophageal dilation.
Gastroesophageal reflux disease (GERD): Lower esophageal sphincter incompetence, allowing reflux of acidic stomach contents into the esophagus, causing heartburn, and potential esophageal damage.

Additional Information

Various substances (protein, alcohol, drugs) can increase or decrease lower esophageal sphincter (LES) pressure.
Infancy lacks fully developed secondary peristalsis mechanisms.

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Description

Explore the complex physiological processes involved in eating, including salivation, mastication, and deglutition. This quiz also delves into the roles of hunger, appetite, and satiety, as well as the central control mechanisms in the brain, particularly the hypothalamus and its feedback systems.