Digestive System 1 Flashcards
What are the 6 Main Digestive Concepts?
Ingestion
Motility
Secretion
Digestion
Absorption
Defecation
What are Ingestion and Motility?
Ingestion – entry to mouth
Motility – movement – mixing/propulsion
What is Secretion
Secretion – contributions – release of water/enzymes / environmental factors
What are Digestion, Absorption and Defacation?
Digestion: Mechanical and Chemical breakdown
Absorption: entry to body.
Defecation: elimination from body.
What is the GI Tract?
Gastrointestinal (GI) tract-
muscular tube; from mouth to anus
What are the Functions of the GI Tract?
(4)
- Material to build and fuel body.
- Ingestion with breakdown.
- Absorption to internal environment.
- Elimination of remaining material plus metabolic end products and wastes.
What Receptors can Detect Change in the GI Tract?
(3)
Mechanoreceptors: Distension (stretch)
Osmoreceptors: Omolarity
Chemoreceptors: Specific concentrations and acidity
What is the Respone of Smooth Muscle Cells to Gastrointestinal regulation?
Smooth muscle cells – circular and longitudinal muscle layer
contractions
What is the Respone of Enteroendocrine Cells Gastrointestinal regulation?
Enteroendocrine cells – hormonal secretions
What is the Respone of Exocrine cells to Gastrointestinal regulation?
Exocrine cells – enzyme and environmental secretions
What is the Respone of Mucous cells to Gastrointestinal regulation?
Mucous cells – mucus secretions
Afferent information sent to CNS from receptors (3)
Somatic sensory – muscles.
Visceral sensory – organs.
Special sensory – eyes, ears, etc
Efferent information sent to effectors from CNS (3)
Somatic motor – muscles.
Autonomic motor (or autonomic nervous system; ANS): sympathetic, parasympathetic, enteric – variable targets.
Enteric –GI tract’s own local neural control; more neurons than spinal cord.
Afferent vs Efferent Neural Divisons?
What is the Enteric nerve plexuses?
What are the 2 Main ones?
Enteric nerve plexuses are intricate networks of neurons that are located in the walls of the gastrointestinal (GI) tract:
- Myenteric
- Submucosal
What type of communication exists between the Enteric nerve plexuses?
(3)
- Within plexus and between plexuses.
- Receptors to plexuses
- CNS to plexuses
What is the Myenteric Plexus?
This plexus is situated between the circular and longitudinal muscle layers of the GI tract. It primarily controls muscle contractions and is involved in regulating the motility of the digestive system
What is the Submucosal Plexus?
This plexus is located in the submucosa of the GI tract, beneath the mucous membrane, especially Epithelial Cells. It is responsible for regulating secretions from the mucosal glands, blood flow, and absorption in the intestine
What are the Short reflexes of the Enteric nerve plexuses?
Short reflexes (intrinsic to GI tract; enteric)
- Within GI tract.
- Stimuli – receptors – plexus – effector – response
What are the Long reflexes of the Enteric nerve plexuses?
Long reflexes (extrinsic to GI tract; CNS)
- Extending outside GI tract and adds to enteric path:
- Afferent – receptors to CNS.
- Efferent autonomic (sympathetic and
parasympathetic) – CNS to plexuses
Short and Long Responses Visual:
What are Enteroendocrine cells?
Location, Structure, function, Target Areas
Location: Mainly stomach and small intestine.
Structure: have one surface that is exposed to the lumen of the GI tract, allowing them to detect and respond to stimuli encountered in the digestive contents
Function: When stimulated, opposite cell surface from GI tract lumen releases hormone into blood, can be inhibitory or excitatory
Target Area: Can have multiple target areas
What are the Key Hormones released by the Enteroendocrine cells?
- Gastrin
- Secretin
- Cholecystokinin (CCK)
- Somatostatin
What is a Chemical messenger
Chemical messenger – hormone, neurotransmitter,
paracrine substance, autocrine substance.
- Chemical messenger is released and will bond a receptor on a target.
- Target will generate a response to the binding of the receptor.
- Targets can be close to release site or over distance.
What is a Cephalic stimuli?
signal to salivary center in medulla oblongata
What is the Parasympathetic Response of Cephalic stimuli?
2
Basic stimulation – signals salivary glands to provide basic level of salivation (saliva production) to keep tissues moist
Parasympathetic to stomach in preparation for food coming - increases acid secretion and stomach motility
Parasympathetic
Cephalic Stimuli Flow Chart:
What is the Sympathetic Response of Cephalic stimuli?
Sympathetic stimulation:
- Increased stimulation – signals salivary glands to decrease salivation.
- Alters volume and composition.
- Dry mouth feel
Sympathetic
Cephalic Stimuli Flow Chart:
