BIO 132 – Anatomy and Physiology II
Study Outline
5.1. Overview to the Regulation of Digestive Function:
a. Examples of sensory receptors that provide the afferent limb of visceral reflexes that affect digestive function are: __________________________, _________________________, and ______________________________.
b. A short reflex involves sensory information passing to ___________________________which in turn stimulates the effectors which could be either ______________________ or ________________________.
c. By contrast, a ___________________________ involves sending afferent information back to the central nervous system which in turn generates an efferent response involving the _______________________ system with its ______________________ division and ______________________ division.
d. In some cases, stimuli that provoke __________________________ reflexes come in the form of sight, smell or even thought of food.
5.2. Functions of Saliva:
a. In humans, typically about ___________ liters of saliva is produced each day.
b. Saliva serves a number of functions including ________________________, _________________________, ____________________________________, _________________________, and _________________________________.
c. Among the constituents of saliva are ________________________________, ___________________________, __________________________________, ___________________________, and _______________________________.
d. The glycoprotein, _____________________________, when put into aqueous solution produces a thick mucus which serves the function of _______________________________________.
e. Two of the constituents of saliva, ________________________________ and ___________________________________, help to fight bacteria.
f. The digestion of _______________________ begins in the mouth through the action of ___________________________. Another enzyme present in small amounts is ___________________________.
g. The condition in which a person lacks functional salivary glands is called ______________________, which is correlated with an increased frequency of __________________________ and ____________________________. However starch digestion is usually not affected because of the presence of ____________________________.
5.3. Secretion of Saliva:
a. The ionic composition produced by acinar cells is only slightly hypotonic to __________________________.
b. Striated duct cells modify the composition of saliva by extracting _______________________ and _______________________, and adding _______________________ and _______________________. Of these the ____________________ serves the purpose of helping to buffer acidic foods.
c. Amylase is secreted mainly by _____________________________ cells.
5.4. Neural Control of Salivary Secretion:
a. Sensory information used in controlling salivary secretion is generated by _________________________ and __________________________ in the mouth. These signals, in turn, are sent to the __________________________________.
b. In some cases, eating ______________________ foods as well as nausea can stimulate salivation.
c. In other cases, the smell, sight, sound, or thought of food can stimulate ____________________________ centers. These stimuli constitute ______________________ activation and involve learned behaviors.
d. Stimulation of _________________________ nerves results in an increase in _____________________ secretion whereas sympathetic nerve stimulation produces a more _______________________ secretion.
e. Increased salivary secretion can also arise from increased ______________________________ flow caused by VIP which acts to _________________________.
5.5. Swallowing:
a. Swallowing is typically initiated ______________________________but is thereafter under ____________________ control. The swallowing reflex is an ordered sequence of events in which a bolus of food is propelled from the __________________________ to the ______________________________.
b. Swallowing consists of three phases called the _________________________ phase, ______________________ phase, and _________________________ phase.
c. The _____________________ phase is a voluntary phase that begins by separating a bolus of food in the mouth with the _______________________. During this time the ______________________________ is closed.
d. During the pharyngeal phase, the _______________________ and _______________________ are pulled upward to prevent food from passing into the nasopharynx; the ___________________________ is elevated so the _________________________ covers the opening into the respiratory system; and the ________________________ muscles contract setting up a peristaltic wave. During this period the ______________________________ is relaxed.
e. During the last phase, called the _______________________ phase, the upper esophageal sphincter is now ____________________________. Just before the food reaches the stomach, the ________________________ relaxes. Any condition that tends to relax the lower esophageal sphincter will give rise to ________________________________.
5.6. Gastric Secretions:
a. The two digestive enzymes released from _____________________ cells are _________________________ and ____________________________. The __________________________ is released in inactive form and is activated by either ________________________ or ___________________________.
b. Stomach acid, chemically is ________________________ which is produced by _________________________ cells. In this case the H+ is obtained by the chemical reaction involving CO2 and H2O which is catalyzed by the enzyme ______________________________________. The H+ are pumped to the __________________________, whereas the _________________________ are pumped to the interstitial fluids giving rise to the alkaline tide.
c. The three agents which can stimulate acid secretion are _____________________________, _____________________________ and _____________________________. Of these only ____________________ uses cAMP as a second messenger.
d. Normally, the gastric mucosa can produce on the order of ________________ liters of gastric secretion per day.
5.7. Regulation of Gastric Secretion:
a. The events of gastric secretion occur in three distinct, but overlapping phases called the _____________________ phase, the _______________________ phase, and the ___________________________ phase.
b. The _______________________ phase occurs before food actually enters the stomach. The smell, taste, sight or thought of food generates input that is sent to the _________________________ which in turn stimulates ____________________ nuclei in the brainstem. Stimulation of the vagus nerve results in gastric glands increasing their secretion of ________________________, ___________________________, and ___________________________. Conversely this phase is damped when a person is depressed or with no appetite, or when the __________________________ system is activated.
c. Once food reaches the stomach, both neural and hormonal mechanisms initiate the next phase, called the _____________________ phase.
d. The vago-vagal reflex involves sensory information generated by _____________________ receptors and/or ________________________ present in the wall of the stomach. The efferent response is carried in the _______________________ nerve.
e. Acetylcholine released from parasympathetic nerves (i.e. vagus) cause gastric glands to increase ____________________ and _____________________ secretion as well as the secretion of ____________________ from entero-endocrine cells.
f. Gastrin secretion is stimulated by _____________________________, ________________________, or _________________________ and acts to increase _________________________ secretion from chief cells but also to increase ___________________________ secretion.
g. Histamine is produced by ________________________ cells in the lamina propria and stimulates _____________________ receptors on parietal cells. People who suffer from acid-based ulcers are given H2 _____________________ which reduce acid secretion.
h. Gastrin secretion is inhibited by ___________________________. Also emotional stress decreases acid secretion through a stimulation of the _____________________________ system.
i. The _____________________ phase is stimulated by the presence of low pH and partially digested food in the duodenum. One of the effects is to stimulate secretion of _______________________which has a positive influence on gastric secretions.
j. The ____________________ reflex is triggered by distension of the duodenum as well as the presence of acid and partially digested food in the duodenum. This reflex involves the inhibition of ______________________ in the brainstem, inhibiting local reflexes involving ACh, and stimulating the ___________________ system which causes the pyloric sphincter to contract.
k. Several hormones are secreted during the intestinal phase including ____________________________, ________________________________, ____________________________, and _____________________________. Of these, _________________________ probably is most important in inhibiting gastric secretions.
5.8. Gastric Motility and Emptying:
a. The term which describes why the internal pressure within the stomach remains essentially constant up to about one liter is __________________________ which occurs due to output from the ____________________________ center and a local reflex involving release of _________________________ which relaxes smooth muscle.
b. Peristaltic waves proceed from the _______________________ to the __________________________. The strength of contraction is increased by ______________________ and _____________________________. By contrast, emotional stress inhibits gastric motility through activation of the ___________________________ system.
c. Gastric emptying is initiated by stimuli such as ____________________ of the stomach wall, and the presence of partially digested proteins and ________________________. These stimuli increase _________________ secretion and an increased frequency of vagal nerve impulses. These in turn stimulate contraction of the ____________________ sphincter, increased gastric motility, and relaxation of the _____________________ sphincter.
d. Inhibition of gastric emptying is mediated by the _____________________ reflex and involves an inhibition of __________________ activity as well as increased secretion of ________________________________, ___________________________, ____________________________, and __________________________, of which __________________________ has the most potent inhibitory effect on gastric emptying.
e. _________________ involves the forced expulsion of stomach contents out the mouth and involves ____________________ centers located in the brainstem. Prolonged vomiting can lead to __________________ and ________________________ in the blood due to continued production of __________________________ in order to replace the stomach acid.