Flashcards in Unit 3 Deck (103)
What are the 2 functional types of smooth muscle
Multi-unit and unitary
In multi smooth muscle, each fiber is ____ of other fibers
Each multi-unit smooth muscle is innervate by:
It’s own nerve ending
Multi-unit smooth muscle is insulated from ____ ____ fibers by ____ and ____.
Other smooth muscle fibers
Where is multi-unit smooth muscle found?
In ciliary muscle of the eye, iris, pilo-erector muscles
Unitary smooth muscle, AKA:
Syncytial smooth muscle
In unitary smooth muscle, multiple muscle fibers function as a ____ ___.
Fibers are arranges in ____ or ____.
Membranes are interconnected by ___ ___.
Sheets or bundles
Unitary Smooth muscles are found where?
Most viscera (gut, blood vessels, uterus, ureters, bile ducts)
In smooth muscle, Actin is attached to:
Adjacent ones are attached to each other by:
In smooth muscle, myosin is interspersed amongst the:
Smooth muscle contraction properties
Slow cycling of myosin cross bridges
Force of contraction
The smooth muscle frequency is much (MORE/LESS) than skeletal muscle, and cross bridges hold for (LONGER/SHORTER) time
Once tension has developed, _______ are maintained for a period of time with (LOTS/LITTLE) additional energy. This is an energy efficient way to maintain ___.
Stress-relaxation response is seen principally in:
Visceral unitary muscle
The stress-relaxation response is a response to what?
In stress-relaxation response, smooth muscle responds to stretch _____, then:
Adapts to its new length
The new length retains its ability to contract
The stress-relaxation response enables organs such as the ____ and ____ to:
Stomach and bladder
Temporarily store contents
In smooth muscle contraction,
Stimulus causes increase in ____ ___.
This will bind to ______.
For smooth muscle contraction, Ca+2/calmodulin binds to and activates:
This phosphorylates :
Which is capable of:
Myosin light chain kinase (MLCK)
The light chains of the myosin heads
Binding to actin
Smooth muscle relaxation,
Contraction is stopped by :
Source of calcium for muscle contraction
Cell membrane calcium channels
Almost all of the calcium used in muscle contraction is used from:
The sarcoplasmic reticulum is ____ developed in smooth muscle
Smooth muscle has rudimentary T-Tubules called:
Smooth muscle can be stimulated by:
The nervous system
Local tissue factors
For smooth muscle contraction, autonomic fibers end in ______ making _______. Nerve endings are closer to _______ smooth muscle cells as compared to ____ muscle
“Diffuse” neuromuscular junctions
Typical smooth muscle neurotransmitters are:
Ach and NE
Review pic in slide 9
Hormones may cause smooth muscle contraction or dilation based on:
The receptor type they bind to
Some hormone receptors for smooth muscles are themselves ____ ____ that cause ____ or _____ depending on:
Depolarization or hyperpolarization
Which ion they are specific to.
For smooth muscle
Some hormones use ____ ____ __ such as ____q
Second messenger systems
Hormones used in smooth muscle contraction
Many smooth muscles naturally maintain ___, such as those in:
Vasodilation of smooth muscle tone results from:
Increased body temp
Smooth muscle stretch reduces the ___ of the smooth muscle membrane potential leading to more ____ at the:
Peaks of the slow waves
In smooth muscle membrane potentials, no true ___ ____ occur.
Cells are individually _____.
Cells are too ____ to generate an ___
Depolarizations are called:
In AP of unitary SM, _____ channels are more responsible for AP than:
AP patters for unitary SM
Slow-waves (spontaneous, pace-maker like fluctuations in membrane potentials) with spike potentials
AP with plateaus
Depolarization factors of GI smooth muscle
Hyperpolarizing facotrs of GI smooth muscle
Function of GI
Propulsion of good through GI tract
Secretion of digestive juices
Digestion; chemical and mechanical digestion
Absorption of digestive products
Circulation of blood through the GI tract (to circulate absorbed digestive products)
Local, nervous and hormonal control of the above functions
Propulsion of food through the GI tract includes:
Peristalsis (esophagus, stomach, small intestine, large intestine)
Mechanical digestion of the GI includes:
Segmentation (small intestine)
Absorption of the GI includes:
Nutrients and water to blood vessels and lymph vessels (small intestine)
Water to blood vessels (large intestine)
GI tract wall layers, external to internal
Longitudinal smooth muscle
Circular smooth muscle
Mucosal and submucosal glands
What is the enteric nervous system
The GI tracts own nervous system from the esophagus to the anus
Plexi of the enteric NS and their location
Myenteric (Auerbach’s) plexus
-Between longitudinal and circular muscle layers
Submucosal (Meissner’s) Plexus
- Within the submucosa
What plexus is mostly responsible for GI movements?
What is it composed of?
A linear chain of interconnecting neurons extending the length of the GI tract
Excitation of the myenteric plexus increases:
Tonic (tone) contractions
Intensity of rhythmic contractions
Velocity of wave conduction
Release of vasoactive intestinal polypeptide (which relaxes pyloric and ileocecal sphincters)
Functions of the submucosal plexus
Control local intestinal secretion and absorption
Control local contraction of submucosal muscles (unfolding of the mucosa)
Which parasympathetic nerves innervates the esophagus -> 1st half of large intestine? What else does it innervate?
Cranial parasympathetic nerves (mainly vagus)
Parasympathetic innervation from distal large intestine -> anus
Sacral parasympathetic nerves (pelvic nerves)
Postganglionic parasympathetic neurons and ganglia are within the ___ ___.
Acetylcholine is largely _____ to the GI tract
Preganglionic neurons to the GI tract originate from where?
Postganglionic neurons originate from the:
______ inhibits intestinal tract smooth muscle mainly via the ___ ___
Enteric plexus (except the muscularis mucosa which it excites)
80% of nerve fibers in the vagus nerves are ____.
Afferents from the gut are sensitive to:
Irritation of the mucosa
Distention of the gut
Chemicals in the gut
What are the 3 types of GI reflexes
Enteric reflexes are entirely located where?
They control what?
Within the gut wall enteric nervous system
Control local GI secretions, peristalsis, mixing and local inhibitory effects
What are some examples of autonomic reflexes?
Gastrocolic reflex- Promotes evacuation of the colon
Enterogastric reflex- Inhibits stomach motility and secretions
Colonileal reflex- Inhibits emptying of ileal contents into the colon
Sensory signals originate from the gut -> prevertebral ganglia -> Then motor back to the gut
Higher level reflexes
Sensory signals from the gut to the spinal cord or brainstorm to the GI tract
Examples of higher level reflexes
Reflexes from the stomach and duodenum to the brain stem and back to control stomach motility and secretions
Pain reflexes that cause general inhibition of the GI tract
Defecation reflexes to from and to the colon
Gastric is secreted by what?
“G” cells of the stomach
Gastric acid secretion and gastric mucosal growth
Cholecystokinin is secreted by what?
“I” cells of the duodenum mucosa
Gall bladder contraction, slows gastric emptying and inhibits appetite
Secretin is secreted by what?
“S” cells of duodenum mucosa
Pancreatic secretion of bicarbonate, and some effect on GI motility
Gastric inhibitory peptide is secreted by what?
Upper small intestine
Insulting secretion, and decreases stomach motility
Propulsive movements in one directions
GI Peristalsis is generally stimulated by:
Also by parasympathetic and irritation to the epithelium
GI peristalsis required:
The myenteric plexus
What are mixing movements of the GI?
Peristalsis towards a closed sphincter— causes a churning effect.
Local intermittent constrictive contractions creating a “chopping” or “shearing” effect
Arterial supply for splanchnic circulation
Sup mesenteric art
Inf mesenteric art
The portal system drains what?
From the gut, spleen and pancreas to the liver - through sinusoids- to the IVC via hepatic veins
Within the liver, what removes any bacteria or particulate materials that may have gotten into the blood?
Reticuloendothelial cells (Kupffer/macrophages)
Water soluble nutrients go to the ____ where ____% gets stored there for further processing
In portal system, fats are absorbed into the ____ which goes to the:
Thoracic duct (bypasses the liver)
As motility and absorption increase in the gut, so does:
Blood flow in the microcirculation of the villus
What are vasodilator substances from the mucosa
Vasoactive intestinal peptide
Mechanism of microcirculation in the gut
Vasodilator substances from mucosa
Kinin vasodilators (bradykinin) from intestinal glands also vasodilator
O2 lack leading to vasodilation
Parasympathetic- increased glandular activity therefore increased blood flow by autoregulation
Sympathetic- causes vasoconstriction
Sympathetic vasoconstriction can be over ridden by _____.
Autoregulation (autogregulation escape)
Constriction is important during when
Or in circulatory shock to shunt blood to general circulation
Incisors are for _____ and provide ___ lbs of pressure
Molars are for ____, and have up to ____ lbs pressure
Muscles of mastication are innervated by what?
CN V3 (Trigeminal)
Muscles of mastication
Medial and lateral pterygoids
What forms the Dental arcades?
Alveolar processes of the maxillae and mandible
Describe the chewing reflex
Bolus causes pressure
Relaxes muscles to open jaw
Pressure is released
Stretch of muscles
Importance of mastication
To break down food for ease of swallowing
To mix food with saliva
Breaks down cellulose to release nutrients in plant based foods
3 stages of deglutition
1- voluntary stage
2- Pharyngeal stage
3- esophageal stage
voluntary stage of deglutition
Tongue pushes food against palate and squeezes food towards oropharynx
What triggers the brain stem mediated reflexes to the pharyngeal muscles
Tonsilar pillars (have swallowing receptors)
What happens in the pharyngeal stage
The palate raises to close pose nares
Palatopharyngeal folds narrow to only allow smaller particles to pass into pharynx
Vocal cords approximate and larynx pulled upward to meet epiglottis to cover larynx
Laryngeal elevation also opens upper esophageal sphincter (normally closed to prevent ingestion of air)
Pharyngeal constrictor muscles propel food by peristalsis into esophagus
What happens in the esphageal stage
Primary peristalsis of the esophageal stage
Continuation of pharyngeal peristalsis
Extends from pharynx to stomach
Lasts 8-10 seconds, gravity aids process
2ndary peristalsis in the esophageal stage
Food that fails to descend distends the esophagus initiating enteric NS mediated waves of peristalsis
(This is what kicks in when you feel like you’re choking. It failed to go down the normal way so body kicks in)
Receptive relaxation in esophageal stage
Lower esophageal sphincter and stomach relaxes
Sensory innervation for swallowing
CN V and IX
Swallowing center is located where?
In the brainstem
Efferent innervation for swallowing
Mostly via CN X
The pharynx and upper 1/3 of the esophagus is ___ muscle.
The lower 2/3 is: