Rest of Bio Flashcards
What is the cardiac cycle?
Contraction of atria (AKA atrial systole), followed by contraction of ventricles (ventricular systole), followed by a rest (diastole) when neither chamber is contracting
What is the contraction called?
Systole (arterial BP –120–/80)
Relaxation is called?
Diastole (arterial 120/–80–)
What is diastolic arterial pressure called?
AFTERLOAD the pressure against which the heart must work to eject blood during systole (systolic pressure)
What do neural and endocrine signals control?
Strength and rate of heart contractions
What does sympathetic innervation (norepinephrine) do on heart rate
Increases
What does parasympathetic innervation (acetylcholine) do on heart rate?
Decreases
What does epinephrine do on each contraction?
Increases the strength
What happens from rest to exercise?
- Heart rate can increase to nearly 200 bpm
- Cardiac outpuut INCREASES from 5-25L/min
What is electrical signal propopaged by?
- Nodes
SA (sinoatrial) node (hearts natural pacemaker: electrical impulses are generated here
AV (atrioventricular) node - Nerves
Bundle of His
Bundle branches
Purkinge fibres - Intercalated disks (gap functions)
What does cardiac muscle consists of?
Individual cardiomyocytes connected by intercalated disks (gap junctions) to work together as a single functional organ
What are some examples of miscommunication of the heart?
Results in some kind of arrhythmia
What does abnormal sinoatrial (SA) node firing result in?
Result in tachycardia, bradycardia, tachy is fast, brady is slow
What do blocks do?
- eg at the AV node, vary in terms of blockage
- Can slow down or prevent signal propogation from atria to ventricles
- Ventricles can contract independently (bundle of His, 40 bpm)
Why are fibrillations more serious?
Occuring when cells depolarize independently
What is atrial fibrillation?
Also called A-fib, is a quivering or irregular heartbeat (arrthymia)
What is atheroscelorisis?
- Narrowing of arteries due to calcified fatty deposits (plaque) and thickening of the wall, triggered by damage to arterial wall (inflammation), can lead to heart attacks or stroke, when this occurs in the arteries of heart muscle, called coronary artery disease
What are factors of atherosclerosis?
- Elevated blood lipids, hypertension, inflammatory mediators (C-reactive protein)
- Diet (sodium, potassium, saturated/trans fat)
- Smoking, physical inactivity, obesity/diabetes
- Age, genetics
How do you treat coronary artery blockage?
- Angioplasty (a catheter and balloon are threaded into the coronary atery to the point of blockages)
- Bypass surgery (vein taken from arm or leg; one end attached above the blockage and the other below)
What is hypertrophy?
sign of being “overworked” heart muscle will respond and hypertrophy just like your skeletal muscle would repsond to weight-lifting
How does the heart reflect of athletes?
Mostly an increase in LV chamber (need to increase cardiac output)
How does the heart reflect of weightlifters?
Mostly increase in LV wall and septum thickness (need to overcome increased after load- the amount of pressure needed to eject blood during ventricular contraction
Why is enlargement of the heart bad?
Causes include high blood pressure and narrowing of aortic valve… heart must work harder to overcome these
Why is enlargement of the heart good?
Athletes heart- an appropriate adaptation, occurs in both athletes and weightlifters
Does BP vary with cardiac cycle?
Yes
What does a systolic BP mean
Maximum pressure
- When the ventricles contract, sending blood in the arteries
Diastolic blood pressure mean?
Minimum pressure
- When the heart relaxes between beats- not zero due to elastic recoil of arterial wall
What does blood pressure categories mean?
Normal numbers less than 120 systolic, less than 80 diastolic
Elevated 120-129 systolic, and less then 80 diastolic
High BP (hypertension stage 1) 130-139 systolic, and 80-89 diastolic
High BP (hypertension stage 2) 140 or higher systolic and 90 or higher diastolic
Hypertensive crisis (consult with your doctor) higher then 180 systolic and higher then 120 diastolic
What does vasoconstriction mean?
- Alpha-receptors are located on arteries
- Norepinephrine and epinephrine bind to alpha 2 adrenergic receptors
- Causes arteries to constrict (vasoconstriction)
- This increases BP
- Eg during excercise
What does vasodilation mean?
- Blood vessels in skeletal muscles lack alpha-receptors
- Norepinephrine and epinephrine bind to b2 adrenergic receptors found in arteries of skeletal muscle
- This dialates vessels of the skeletal muscles (vasodilation) so they can receive increased blood flow
- Eg also during excercise!
What happens to BP during aerobic (cardio) excercise?
Cardiac output increases 5x during excercise, up to 8 in athletes
Does BP increase dramatically during excercise?
Not really, why not?
- Distribution of blood does not increase proportionally- blood flow is diverted to where it is needed during excercise the working muscles
- Dialation of vessels to skeletal muscle and heart increases blood flow to the muscls (beta 2 receptors and local metabolites)
- Constriction of vessels to the gut and kidneys decreases blood flow to the organs (alpha receptors)
- Dialating vessels in muscle decreases resistance and have a lot of muscle mass
- So, BP does NOT increase dramatically during excercise
What is resistant excercise?
muscles against a force eg weightlifting, can cause dramatic increases in BP
-Why holding your breath increases inthoaratic pressure during the lift- called Valsalva maneuver
What does the GI track represent?
- It “sees” not only our food, but potentionally toxic substances and infectious agents
- Unique mechanisms to deal with this:
- Sense and expel noxious substances (vomit, diarrhea)
- Specialized populations of T cells localized to the intestinal mucosa
- Eg Peyers patches
How does it go through the body GI?
- Oral cavity (upper esophageal sphincter)
- Esophagus (lower esophageal sphincter)
- Stomach (pyloric sphincter)
- Small intestine (ileocecal valve)
- Colon (large intestine)
- Anal sphincter
- Rectum
How long is the GI track?
- 28 ft long
Is there a highly variable transit time?
Total of 30-80 h
- 5-8 hrs in stomach and small intestine
- Rest of time in colon
What is microbiome?
- Bacteria, etc
- Protects against pathogenic microbes that enter/reside in the tract
What is the intrinsic (aka enteric) nervous sytem?
Control and coordinate all this functioning (eg opening and closing of sphincters)
What are the 4 basic processes?
Motility
- Peristalsis (contraction and relaxation of muscles throughout the digestive tract)
Secretion
- Saliva, mucous
- Antibodies (IgA)
- Digestive enzymes
- Bile
- Bicarbonate
Digestion
Absorption
- Water
- Nutrients
What is the celiac phase of digestion and absorption?
- Chemical and mechanical digestion begins in the mouth
- Chewing (mastification)
- Secretions in response to sensory stimuli (sight, smell, taste) prepares the GI tract for food processing
What is salivary secretion under control of?
Autonomic control (stimulated by sympathetic and parasympathetic nervous system)
What does salivary secretion do?
- Softens and lubricates food
- Provides enzymes: amylase and some lipase (but no protein digestion)
What is the Gastric phase of Digestion and Absorption?
- Secretory cells of gastric mucosa- note the influence of the Parasympathetic Nervous System (rest and digest)
- It increases intestinal and gland activity, and relaxes sphincter muscles in GI tract
What digests in the stomach?
Protein and fat, but not carbs
What happens in small intestine and acessory organs?
Pancreas: main contributor of digestive enzymes
- Enzymes are released from pancreas in inactive form eg trypsinogen
- Activated in small intestines by enterokinase in brush border of duodenum to form trypsin - for protein digestion
Gallbladder: stores bile (produced by liver)
- Fat digestion
Is there absorption in the small intestine?
Yes
What does small intestinal mucosa do?
Villi increase surface area to promote nutrients absoprtion
What secretions in the lumen of the small intestine upon opening of the pyloric sphincter and food (chyme) entering the upper duodenum
- Bicarbonate- from cells in the intestinal epithelium and in pancreatic seretions
- Digestive enzymes- from pancreas
- Bile acids (as bile fluid)- from liver/gallbladder
Digestive enzymes anchored on the luminar surface of small intestine epethilial cells
- Disaccharides
- Amino peptidases
What is maltose?
2 glucose
What is sucrose?
Fructose and glucose
What is lactose?
Galactose and glucose