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Physiology Flashcards

(102 cards)

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1
Q

What is the basic function of the mouth and oropharynx?

A

Chops and lubricated food, starts carbohydrate digestion, propels food to the oesophagus

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2
Q

What is the basic function of the oesophagus?

A

It is a muscular tube that propels food to the stomach

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3
Q

What is the basic function of the stomach?

A

It stores/churns food, continues carbohydrate and initiates protein digestion, regulates delivery of chyme to the duodenum

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4
Q

What enzyme is present in the stomach?

A

Pepsin, helps to break down food

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5
Q

What are the 3 sections of the small intestine?

A

Duodenum, jejunum and ileum

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6
Q

What is the basic function of the small intestine?

A

Principal site of digestion and absorption of nutrients

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7
Q

What are the 3 sections of the large intestine?

A

Caecum, appendix and colon

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8
Q

What is the basic function of the large intestine?

A

Colon reabsorbs fluid and electrolytes, stores faecal matter before delivery to the rectum

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9
Q

What is the basic function of the rectum and anus?

A

Storage and regulated expulsion of faeces

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10
Q

What are the accessory structures?

A

Salivary glands, pancreas, liver and gall bladder (hepatobiliary system)

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11
Q

Where is fat digestion initiated?

A

Small intestine

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12
Q

What are the 4 activities of the alimentary canal?

A

Motility, secretion, digestion and absorption

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13
Q

What occurs during motility?

A

Mechanical activity mostly involving smooth muslce (skeletal muslce at mouth, pharynx, upper oesophagus and external anal sphincter)

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14
Q

What occurs during secretion?

A

Into the lumen of the digestive tract occurs from itself and accessory structures in response to the presence of food, hormonal and neural signals. Secretion is required for: digestion, protection and lubrication

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15
Q

What occurs during digestion?

A

Chemical breakdown by enzymatic hydrolysis of complex foodstuffs to smaller, absorbable untis

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16
Q

What occurs during absorption?

A

The transfer of the absorbable products of digestion (with water, electrolytes and vitamins) from the digestive tract tot eh blood, or lymph - largely mediated by numerous transport mechanisms

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17
Q

What is contained within the mucosa?

A 
Epithelial cells 
Exocrine cells 
Endocrine gland cells
Lamina propria (capillaries, enteric neruones, immune cells (lymphocytes and pathogens)
Muscularis mucosae
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18
Q

What is the function of the muscularis mucosae?

A

Thins smooth muscle layer that has the function of changing the shape of the entire mucosa and is important in the mixing the contents of the lumen

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19
Q

What is contained within the submucosa?

A

Elastic connective tissue, larger blood and lymph vessels, glands and the submucous plexua

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20
Q

What are the 2 parts tot he muscularis externa?

A

Circular smooth muscle and longitudinal muscle layer

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21
Q

What does the circular smooth muscle do?

A

Controls the diameter of the lumen

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22
Q

What does the longitudinal smooth muscle layer do?

A

Controls the length of the lumen

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23
Q

What is the serosa?

A

Connective tissue

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24
Q

What type of cells are contained within the serosa?

A

Squamous cells that secrete lubricants that help the movement of flood through the intestine

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25
What occurs when the circular muscle contracts?
The lumen of the tract becomes narrower and longer
26
What occurs when the longitudinal muscle contract?
The lumen becomes shorter and fatter
27
What is a single unit muscle?
The muscle is comprised of individual smooth muscle cells but they are electrically linked via gap junctions
28
What is the function of gap junctions?
They allow the spread of electrical currents from cell to cell forming a functional syncytium
29
What modulated spontaneous electrical activity via pacemaker cells?
Intrinsic (enteric) and extrinsic (autonomic) nerves | Numeous hormones
30
What is a slow wave?
Rhythmic patterns of membrane depolarisation and repolarisation that spread from cell to cell via gap junctions
31
What does the slow wave electrical activity determine?
The max frequency, direction and velocity of rhythmic contractions
32
What is the name of the pacemaker cells in the GI tract?
Interstitial cells of Cajal (ICCs)
33
When does contraction occur in smooth muscle cells?
Only occurs if the slow wave amplitude is sufficient to trigger SMC action potentials
34
What mediates the upstroke of SMC action potentials?
Voltage-activated Ca2+ channels (L-type Ca2+ channels)
35
What mediates the downstroke of SMC action potentials?
Voltage-activated K+ channels
36
Where are ICCs located?
Between the longitudinal and circular muscle layers and in the submucosa
37
What do slow waves determine?
The basic electrical rhythm (BER)
38
What is the BER frequency in the stomach?
3 slow waves per minute - will only initiate an AP if it reaches the threshold via the action of a stimulus
39
What is the BER frequency of the small intestine?
12 in the duodenum and 8 in the terminal ileum, this drives luminal contents in the aboral direction
40
What is the BER frequency of the large intestine?
8 in the proximal colon 16 in the distal (sigmoid) colon which favours retention of luminal contents facilitating reabsorption of water and electrolytes
41
Where can parasympathetic fibers be released from?
``` Vagus nerve (medulla oblongata) Sacral spinal cord (S2-4) - pelvic nerves ```
42
Where are the synapses within the parasympathetic system?
Preganglionic fibres synapse with ganglion cells within the ENS
43
What occurs when the parasympathetic nervous system is excited?
Increased gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction
44
What inhibitory influences does the parasymathetic system impose?
Relaxation of some sphincters and receptive relaxation of stomach
45
Where does the sympathetic nervous system synapse?
Preganglionic fibers synapse in the prevertebral ganglia (abdomen). The postganglionic fibers will then innervate mainly enteric neurones but also other structures
46
Where can sympathetic nerves originate from?
Thoraco-lumbar region
47
What are the prevertebral ganglia in the abdomen?
Celiac Superior mesenteric Inferior mesenteric
48
What are the exitatory influences of the sympathetic innervation on the GI tract?
Increased sphincter tone
49
What are the inhibitory influences of sympathetic innervation on the GI tract?
Decreased motility, secretion and blood flow
50
What does the myenteric plexus regulated?
Motility and sphincters
51
What does the submucous plexus regulate?
Mainly epithelia and blood vessels
52
What are sensory neurones?
Mechanoreceptors Chemoreceptors Thermoreceptors
53
What is the function of interneurones?
To co-ordinate reflexes and motor programmes
54
What is the function of effector neurones?
Excitatory and inhibitory motor neurones supplying both smooth muscle layers, secretory epithelium, endocrine cells and blood vessels
55
What is a local reflex?
Occurs entirely within the walls of the GI tract (mechanical receptor detects distension, signals to interneurone which then sends this to the motor neurone)
56
What is an example of a local reflex?
Peristalsis
57
What is a short reflex?
Sensory nerurone detects change and sends signal to prevertebral ganglion where it synapses. This then sends the signal to the interneurone back within the walls of GI tract where it synapses with the effector neurone
58
What is an example of a short reflex?
Intestine-interstinal inhibitory reflex
59
What is a long reflex?
Same as short reflex but the sensory neruone is not contained within the GI walls and it will synapse in the CNS with the vagus nerve
60
What is an example of a long reflex?
Gastroileal reflex
61
What is peristalsis?
A wave of relaxation followed by contraction that normally proceeds along the gut in an aboral direction, triggered by distension of the gut wall
62
What occurs in the propulsive segment?
Longitudinal muslce relaxes (release of VIP and NO from inhibitory motorneurone) Circular muslce contracts (release of ACh and substance P from excitatory motorneurone)
63
What occurs in the receiving segment?
Longitudinal muscle contracts (release of ACh and substance P from excitatory motorneurone) Circular muscle relaxes (release of VIP and NO from inhibitory motorneurone)
64
What is energy homeostasus?
The physiological process whereby energy intake is matched to energy expenditure over time
65
What does energy homeostasis promote?
Body fuel stability, energy is primarily stored as fat
66
What are the causes and consequences of metabolic stress?
``` Metabolic syndrome Central obesity Dyslipidemia Insulin resistance Type 2 diabetes CV disease ```
67
How is BMI calculated?
Weight/m2
68
What are the BMI vales?
up to 25 = thin/acceptable 25-29.9= overweight 30.0-39.9 = obese 40 or above morbidly obese
69
What are the major factors influencing obesity?
Genetics | Environment - sedentery lifestyle
70
What are the long term consequences of obesity?
``` Stroke (hypertension) Respiratory disease (sleep apnea) Heart disease (lipids, diabetes, hypertension) Osteoarthritis Gallbladder disease Dementia (alzheimers) NAFLD (fatty liver) Diabetes Cancer (uterus, breast, prostate, colon) Hyperuricemia, gout ```
71
Why do we need fat?
Energy storage Prevention of starvation Energy buffer during prolonged disease`
72
Why is it difficult to lose weight once gained?
Increased body fat alters the brain function and long term obesity changes the brain to view the extra weight as normal and dieting as a threat to body survivial
73
How does the CNS influence energy balance and body weight?
Behaviour - feeding and physical activity ANS activity - regulates energy expenditure Neuroendocrine system - secretion of hormones
74
What neural center is responsible for control of energy intake and body weight?
Hypothalamus Lesioning ventromedial hypothalamus = obesity Lesioning lateral hypothalamus = leanness
75
What 3 concepts underly the control system that controls energy intake + body weight?
Satiety signalling Adiposity negative feedback signalling Food reward
76
What is satitation?
The sensation of fullness generated during a meal
77
What is satiety?
The period of time between termination of one meal and the initiaion of another
78
What is adiposity?
The state of being obese
79
How do satiation signals change during meals?
They increase during meals to limit the meal sizes
80
What is cholecystokinin (CCK)?
A hormone secreted from enteroendocrine cells in the duodenum and jejunum.
81
What is the function of CCK?
It is released in proportion to lipids and proteins in meals. It signals via sensory nerves to hindbrain and stimulates the hindbrain directly (nucleus of solitary tract (NTS))
82
What is Peptide YY (PYY)?
A hormone secreted from endocrine mucosal L-cells of the GI tract
83
What is the function of PYY?
Levels increase rapidly post-prandially. This inhibits gastric motility, slows emptying and reduces food intake (hypo)
84
What is glucagon-like peptide 1 (GLP-1)?
A product of pro-glucoagon gene that is released frfom L cells in response to food ingestion
85
What is the function of GLP-1?
Inhibits gastric emptying and reduces food intake (hypo, NTS)
86
What is oxyntomodulin (OXM)?
A protein from pro-glucagon and released from oxynitic cells of the small intestine after a meal
87
What is the function of OXM?
It acts to supress appetite
88
What is obestatin?
A peptide produced from a gene that encodes ghrelin and released from cells lining the stomach/small intestine
89
What is the function of obestatin?
It reduces food intake and also may act to antagonise the actions of ghrelin
90
What is ghrelin?
An octanolyated peptide that is produced and sereted by oxynitic cells in the stomach
91
When do ghrelin levels rise and fall?
Ghrelin levels increase before meals before meals and decrease after meals. Levels are raised by fasting and hypoglycaemia
92
What is the function of ghrelin?
Peripheral ghrelin stimulates food intake (hypo) and decreases fat utilization
93
What signals increase food intake?
Glutamate, Gaba and opioids
94
What signals supress food intake?
Monoamines
95
What is leptin?
A hormone made and released from fat cells
96
What is inslin?
A hormone made and released from pancreatic cells, the levels int he blood increase as more fat is stored
97
What is the function of hormones in feeding?
It informs the hypothalamus to alter energy balance - eat less and increase energy burn
98
What is the function of leptin?
Circulates in proportion to body adiposity and has a specific transport system for leptin to enter the brain as there are high levels of leptin receptors (Ob-Rb) in the hypothalamus.
99
What are the biological roles of leptin?
Food intake/energy expenditure/fat deposition Peripheral glucose homeostasis/insulin sensitivity Maintenance of immune system Maintenance of reproductive system Angiogenesis Tumorigenesis Bone formation
100
What is an approved weight loss drug?
Orlistat which inhibits pancreatic lipase decreasing triglyceride absorption. This reduces the efficiency of fat absorption in the small intestine
101
What is an example of surgery that can be used for weight loss?
Gastric by-pass produces substantial weight loss and can completely resolve type 2 diabetes By-pass restricts calorie intake and induces malabsorption of nutrients
102
What are thermogenic adipocytes?
They increase energy expenditure by uncoupling of oxidative metabolism from ATP production. The uncoupling of protein 1 (fatty acid activated protein) short circuits the proton gradient in the mitochondria and accelerates fuel oxidation producing heat

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