GIT Muscle Movements and Tonic Contractions Quiz

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Questions and Answers

What is the primary function of saliva during mastication?

Moisten food and the mouth (correct)

Dissolve food in the stomach

Increase saliva production

Break down proteins

What percentage of saliva is water?

99.5% (correct)

98.5%

99.0%

100%

Which structure prevents backflow of stomach contents?

Lower esophageal sphincter (correct)

Pyloric sphincter

Fundus

Upper esophageal sphincter

Which part of the stomach is responsible for mixing food and producing chyme?

Antrum Signup and view all the answers

What is the primary role of the parotid gland?

Produce amylase Signup and view all the answers

What type of muscle contraction is characterized by maintained contraction without relaxation?

Tonic contractions Signup and view all the answers

Which region of the stomach is primarily responsible for temporary storage of ingested food?

Body Signup and view all the answers

What does saliva primarily inhibit?

Bacterial growth Signup and view all the answers

What is the primary function of peristalsis in the gastrointestinal tract?

Pushing food toward the anus Signup and view all the answers

Which part of the autonomic nervous system inhibits gastrointestinal tract activities?

Sympathetic nerves Signup and view all the answers

What is the viscous mixture formed in the stomach called?

Chyme Signup and view all the answers

Which of the following hormones is NOT typically involved in regulating gastrointestinal activities?

Adrenaline Signup and view all the answers

What is the primary digestive role of the tongue during mastication?

Manipulating food and detecting taste sensations Signup and view all the answers

What is the moist lump called that results from the mixing of food with saliva during mastication?

Bolus Signup and view all the answers

What is the role of the myenteric plexus in gastrointestinal function?

Controls movements and contractions Signup and view all the answers

Which of the following processes do NOT contribute to mechanical digestion in the mouth?

Chemical breakdown by amylase Signup and view all the answers

What substance is generated by the action of carbonic anhydrase?

Carbonic acid Signup and view all the answers

What is the process called when bicarbonate ions are released into the bloodstream, resulting in an increase in blood pH?

Alkaline tide Signup and view all the answers

Which hormone is primarily responsible for stimulating acid production in the stomach?

Gastrin Signup and view all the answers

Which of the following mechanisms directly inhibits parietal cell acid production?

Somatostatin Signup and view all the answers

What happens to gastric secretion as food empties from the stomach into the intestine?

Gastric secretion gradually decreases Signup and view all the answers

Which digestive process begins in the antrum of the stomach?

Protein digestion Signup and view all the answers

Which of the following is the primary role of secretin in the digestive process?

Inhibiting acid secretion Signup and view all the answers

What protective mechanism does the gastric mucosal barrier provide?

Protecting the stomach lining from gastric secretions Signup and view all the answers

What stimulates the secretion of HCL and pepsinogen in the stomach?

Vagal nerve impulses Signup and view all the answers

What is the primary function of the gastric phase?

To stimulate chemoreceptors in the stomach Signup and view all the answers

Which nerve mediates the receptive relaxation of the stomach?

Vagus nerve Signup and view all the answers

What characterizes the basic electrical rhythm (BER) in the stomach?

It occurs continuously and initiates contractions Signup and view all the answers

What is chyme?

Semi-fluid mixture of digested food Signup and view all the answers

What controls the strength of peristaltic contractions during gastric emptying?

Signals from the stomach and duodenum Signup and view all the answers

What role do secretin and cholecystokinin play during the intestinal phase?

Inhibit gastric juice secretion Signup and view all the answers

What is the purpose of the pyloric sphincter during gastric emptying?

To prevent backflow of food into the stomach Signup and view all the answers

What is the main function of bile salts in the digestive process?

To convert large fat globules into lipid emulsion Signup and view all the answers

What structure is formed by lipid molecules arranged in a spherical form in aqueous solutions?

Micelle Signup and view all the answers

Which part of the small intestine is mainly responsible for nutrient absorption?

Jejunum Signup and view all the answers

What is the role of bilirubin in the digestive system?

To be excreted in bile as a waste product Signup and view all the answers

What method of motility in the small intestine allows for the mixing of chyme?

Segmentation Signup and view all the answers

What component of bile salts is derived from cholesterol?

Lipid-soluble part Signup and view all the answers

What is a primary characteristic of the jejunum's structure that aids in absorption?

Extensive villi Signup and view all the answers

What is the main function of the duodenum in the small intestine?

Neutralize acidic chyme Signup and view all the answers

Study Notes

Tonic Contractions (VALVES)

Maintained contraction without relaxation; crucial for specific functions in the gastrointestinal (GI) tract.
Not linked to slow wave activity; regulated primarily by continuous spike potentials.
Influenced by hormonal effects and ongoing calcium entry into cells.

Muscular Movements of the GI Tract

Mixing: Occurs in oral cavity and stomach; breaks down food into smaller particles for better digestion.
Peristalsis: Wavelike contractions from oropharynx to rectum that propel food towards the anus.
Segmentation: Localized contraction and relaxation in the small intestine; enhances digestion and absorption efficiency.

Regulation of GI Activities

Autonomic Nervous System (ANS):
- Sympathetic nerves inhibit GI function.
- Parasympathetic nerves enhance GI activity.
Enteric Nervous System (ENS): Contains extensive networks of neurons; coordinates local gut functions through myenteric and submucosal plexuses.
Hormonal Control: GI hormones modulate activity; enteroendocrine cells release key hormones like serotonin and gastrin.
Local Factors: pH changes and chemical presence in the lumen affect GI function.

The Mouth

Mechanical digestion via mastication breaks down food.
Salivary amylase initiates chemical digestion, converting polysaccharides to disaccharides.
Saliva, comprised mostly of water, moisten food and aid taste perception.

Salivary Glands

Three pairs (sublingual, parotid, submandibular) produce saliva under neural control.
Saliva includes 99.5% water; functions to moisten, clean teeth, and initiate starch digestion.

Esophagus

Transports food from the throat to stomach via primary peristaltic waves.
Upper and lower esophageal sphincters regulate movement and prevent air and reflux.

Stomach Anatomy

Muscular, J-shaped organ capable of expanding to hold 1-1.5 L of chyme.
Regions include fundus, cardia, body, antrum, and pylorus; each with specific roles in digestion.

Functions of the Stomach

Temporarily stores food, mechanically mixes it, and initiates protein digestion.
Generates acidity through carbonic anhydrase, impacting blood pH and bicarbonate levels.

Regulatory Mechanisms

Acetylcholine (Ach) stimulates gastric secretion and motility.
Gastrin increases HCl secretion in response to food and Ach stimulation.
Somatostatin and secretin inhibit gastric acid secretion in response to high acidity.

Stomach Activity

Gastric secretion wanes as chyme empties into the intestine; carbohydrate and protein digestion continues.
Alcohol and aspirin are absorbed, but larger food particles are not.

Phases of Gastric Secretion

Cephalic Phase: Prepares stomach for food; increases HCl and pepsinogen secretion due to stimuli from the head (e.g., sight, smell).
Gastric Phase: Food in stomach stimulates intrinsic and extrinsic nervous systems.
Intestinal Phase: After chyme enters small intestine, secretin and cholecystokinin decrease gastric juices.

Gastric Filling and Storage

Stomach accommodates large increases in volume with minimal tension change due to receptive relaxation facilitated by vagus nerve.

Gastric Mixing and Emptying

Peristaltic movements mix food into chyme; strong contractions in the antrum push chyme through the pyloric sphincter.

Pancreas

Exocrine function (enzyme secretion) and endocrine function (hormone regulation); connected to the duodenum by ducts.
Responsible for production of bile salts that emulsify fats and facilitate digestion.

Small Intestine

Main site for nutrient digestion and absorption; consists of duodenum, jejunum, and ileum.
Duodenum neutralizes acidic chyme; jejunum specializes in chemical digestion; ileum controls flow into large intestine.
Features large surface area for absorption through villi.

Small Intestine Motility

Segmentation: Primary motility method; involves periodic contractions to mix chyme and promote slow movement through the small intestine.

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Description

Test your knowledge on the muscular movements of the gastrointestinal tract, focusing on tonic contractions and their regulation. This quiz covers key concepts such as mixing, peristalsis, and the biochemical factors influencing these processes. Understand how the GI tract efficiently breaks down and moves food through the system.