Flashcards in Unit 3 Deck (103)
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1
What are the 2 functional types of smooth muscle
Multi-unit and unitary
2
In multi smooth muscle, each fiber is ____ of other fibers
Independent
3
Each multi-unit smooth muscle is innervate by:
It’s own nerve ending
4
Multi-unit smooth muscle is insulated from ____ ____ fibers by ____ and ____.
Other smooth muscle fibers
Collagen
Glycoproteins
5
Where is multi-unit smooth muscle found?
In ciliary muscle of the eye, iris, pilo-erector muscles
6
Unitary smooth muscle, AKA:
Syncytial smooth muscle
7
In unitary smooth muscle, multiple muscle fibers function as a ____ ___.
Fibers are arranges in ____ or ____.
Membranes are interconnected by ___ ___.
Single unit
Sheets or bundles
Gap junctions
8
Unitary Smooth muscles are found where?
Most viscera (gut, blood vessels, uterus, ureters, bile ducts)
9
In smooth muscle, Actin is attached to:
Adjacent ones are attached to each other by:
Dense bodies
Intercellular proteins
10
In smooth muscle, myosin is interspersed amongst the:
Actin
11
Smooth muscle contraction properties
Slow cycling of myosin cross bridges
Force of contraction
“Latch mechanism”
Stress-relaxation
12
The smooth muscle frequency is much (MORE/LESS) than skeletal muscle, and cross bridges hold for (LONGER/SHORTER) time
Less
Longer
13
Once tension has developed, _______ are maintained for a period of time with (LOTS/LITTLE) additional energy. This is an energy efficient way to maintain ___.
Cross-bridges
Little
Tone
14
Stress-relaxation response is seen principally in:
Visceral unitary muscle
15
The stress-relaxation response is a response to what?
Stretch
16
In stress-relaxation response, smooth muscle responds to stretch _____, then:
Briefly
Adapts to its new length
The new length retains its ability to contract
17
The stress-relaxation response enables organs such as the ____ and ____ to:
Stomach and bladder
Temporarily store contents
18
In smooth muscle contraction,
Stimulus causes increase in ____ ___.
This will bind to ______.
Intracellular calcium
Calmodulin
19
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
20
Smooth muscle relaxation,
Contraction is stopped by :
Myosin phosphatase
21
Source of calcium for muscle contraction
Cell membrane calcium channels
Sarcoplasmic reticulum
22
Almost all of the calcium used in muscle contraction is used from:
Extracellular sources
23
The sarcoplasmic reticulum is ____ developed in smooth muscle
Poorly
24
Smooth muscle has rudimentary T-Tubules called:
Caveolae
25
Smooth muscle can be stimulated by:
The nervous system
Hormones
Local tissue factors
Stretch
26
For smooth muscle contraction, autonomic fibers end in ______ making _______. Nerve endings are closer to _______ smooth muscle cells as compared to ____ muscle
Varicosities
“Diffuse” neuromuscular junctions
Multi-unit
Visceral
27
Typical smooth muscle neurotransmitters are:
Ach and NE
28
Review pic in slide 9
Slide 9
29
Hormones may cause smooth muscle contraction or dilation based on:
The receptor type they bind to
30
Some hormone receptors for smooth muscles are themselves ____ ____ that cause ____ or _____ depending on:
Ion channels
Depolarization or hyperpolarization
Which ion they are specific to.
31
For smooth muscle
Some hormones use ____ ____ __ such as ____q
Second messenger systems
CAMP
32
Hormones used in smooth muscle contraction
Norepinephrine
Epinephrine
Acetylcholine
Angiotensin
Endothelin
Vasopressin
Oxytocin
Serotonin
Histamine
33
Many smooth muscles naturally maintain ___, such as those in:
Tone
Arterioles
Metarterioles
Pre-capillary sphincters
34
Vasodilation of smooth muscle tone results from:
Oxygen lack
Increased CO2
H+
Lactic acid
Adenosine
Increased body temp
35
Smooth muscle stretch reduces the ___ of the smooth muscle membrane potential leading to more ____ at the:
Negativity
Depolarization
Peaks of the slow waves
36
In smooth muscle membrane potentials, no true ___ ____ occur.
Cells are individually _____.
Cells are too ____ to generate an ___
Depolarizations are called:
Action potentials
Innervated
Small
AP
“Junction potentials”
37
In AP of unitary SM, _____ channels are more responsible for AP than:
V-gated CA+2
Na+2
38
AP patters for unitary SM
Spike potentials
Slow-waves (spontaneous, pace-maker like fluctuations in membrane potentials) with spike potentials
AP with plateaus
39
Depolarization factors of GI smooth muscle
Stretching
Acetylcholine/parasympathetic
Gastrointestinal hormones
40
Hyperpolarizing facotrs of GI smooth muscle
Norepinephrine/epinephrine/sympathetic
41
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
42
Propulsion of food through the GI tract includes:
Swallowing (oropharynx)
Peristalsis (esophagus, stomach, small intestine, large intestine)
43
Mechanical digestion of the GI includes:
Chewing (mouth)
Churning (stomach)
Segmentation (small intestine)
44
Absorption of the GI includes:
Nutrients and water to blood vessels and lymph vessels (small intestine)
Water to blood vessels (large intestine)
45
GI tract wall layers, external to internal
Serous
Longitudinal smooth muscle
Circular smooth muscle
Submucose
Mucosa
-Epithelium
-Muscularis mucosa
Mucosal and submucosal glands
46
What is the enteric nervous system
The GI tracts own nervous system from the esophagus to the anus
47
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
48
What plexus is mostly responsible for GI movements?
What is it composed of?
Myenteric plexus
A linear chain of interconnecting neurons extending the length of the GI tract
49
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)
50
Functions of the submucosal plexus
Control local intestinal secretion and absorption
Control local contraction of submucosal muscles (unfolding of the mucosa)
51
Which parasympathetic nerves innervates the esophagus -> 1st half of large intestine? What else does it innervate?
Cranial parasympathetic nerves (mainly vagus)
Pancreas
52
Parasympathetic innervation from distal large intestine -> anus
Sacral parasympathetic nerves (pelvic nerves)
53
Postganglionic parasympathetic neurons and ganglia are within the ___ ___.
Enteric plexus
54
Acetylcholine is largely _____ to the GI tract
Excitatory
55
Preganglionic neurons to the GI tract originate from where?
T5-L2
56
Postganglionic neurons originate from the:
Prevertebral ganglia
57
______ inhibits intestinal tract smooth muscle mainly via the ___ ___
Norepinephrine
Enteric plexus (except the muscularis mucosa which it excites)
58
80% of nerve fibers in the vagus nerves are ____.
Sensory
59
Afferents from the gut are sensitive to:
Irritation of the mucosa
Distention of the gut
Chemicals in the gut
60
What are the 3 types of GI reflexes
Enteric
Autonomic
Higher level
61
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
62
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
63
Autonomic reflexes
Sensory signals originate from the gut -> prevertebral ganglia -> Then motor back to the gut
64
Higher level reflexes
Sensory signals from the gut to the spinal cord or brainstorm to the GI tract
65
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
66
Gastric is secreted by what?
It stimulates:
“G” cells of the stomach
Gastric acid secretion and gastric mucosal growth
67
Cholecystokinin is secreted by what?
It stimulates:
“I” cells of the duodenum mucosa
Gall bladder contraction, slows gastric emptying and inhibits appetite
68
Secretin is secreted by what?
It stimulates:
“S” cells of duodenum mucosa
Pancreatic secretion of bicarbonate, and some effect on GI motility
69
Gastric inhibitory peptide is secreted by what?
It stimulates:
Upper small intestine
Insulting secretion, and decreases stomach motility
70
Peristalsis
Propulsive movements in one directions
71
GI Peristalsis is generally stimulated by:
Distention
Also by parasympathetic and irritation to the epithelium
72
GI peristalsis required:
The myenteric plexus
73
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
74
Arterial supply for splanchnic circulation
Celiac artery
Sup mesenteric art
Inf mesenteric art
75
The portal system drains what?
From the gut, spleen and pancreas to the liver - through sinusoids- to the IVC via hepatic veins
76
Within the liver, what removes any bacteria or particulate materials that may have gotten into the blood?
Reticuloendothelial cells (Kupffer/macrophages)
77
Water soluble nutrients go to the ____ where ____% gets stored there for further processing
Liver
50-75%
78
In portal system, fats are absorbed into the ____ which goes to the:
Lymph
Thoracic duct (bypasses the liver)
79
As motility and absorption increase in the gut, so does:
Blood flow in the microcirculation of the villus
80
What are vasodilator substances from the mucosa
Cholecystokinin
Vasoactive intestinal peptide
Gastrin
Secretion
81
Mechanism of microcirculation in the gut
Vasodilator substances from mucosa
Kinin vasodilators (bradykinin) from intestinal glands also vasodilator
O2 lack leading to vasodilation
Adenosine
Parasympathetic- increased glandular activity therefore increased blood flow by autoregulation
Sympathetic- causes vasoconstriction
82
Sympathetic vasoconstriction can be over ridden by _____.
Autoregulation (autogregulation escape)
83
Constriction is important during when
Intense exercise
Or in circulatory shock to shunt blood to general circulation
84
Incisors are for _____ and provide ___ lbs of pressure
Cutting
55
85
Molars are for ____, and have up to ____ lbs pressure
Grinding
200
86
Muscles of mastication are innervated by what?
CN V3 (Trigeminal)
87
Muscles of mastication
Temporalis
Masseter
Medial and lateral pterygoids
88
What forms the Dental arcades?
Alveolar processes of the maxillae and mandible
89
Describe the chewing reflex
Bolus causes pressure
Relaxes muscles to open jaw
Pressure is released
Stretch of muscles
Triggers contractions
Repeat
90
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
91
3 stages of deglutition
1- voluntary stage
2- Pharyngeal stage
3- esophageal stage
92
voluntary stage of deglutition
Tongue pushes food against palate and squeezes food towards oropharynx
93
What triggers the brain stem mediated reflexes to the pharyngeal muscles
Tonsilar pillars (have swallowing receptors)
94
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
95
What happens in the esphageal stage
Primary peristalsis
2ndary peristalsis
Receptive relaxation
96
Primary peristalsis of the esophageal stage
Continuation of pharyngeal peristalsis
Extends from pharynx to stomach
Lasts 8-10 seconds, gravity aids process
97
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)
98
Receptive relaxation in esophageal stage
Lower esophageal sphincter and stomach relaxes
99
Sensory innervation for swallowing
CN V and IX
100
Swallowing center is located where?
In the brainstem
101
Efferent innervation for swallowing
Mostly via CN X
102
The pharynx and upper 1/3 of the esophagus is ___ muscle.
The lower 2/3 is:
Striated
Smooth
103
