Lecture 15 & 16 Flashcards
What is the Cardiac System?
-a continuous loop never-ending Contraction is called systole
(e.g. arterial BP: 120 / 80)
Relaxation is called diastole
(e.g. arterial BP: 120 / 80)-healthy blood pressure
▪ Contraction of atria (AKA atrial systole)
▪ Followed by contraction of ventricles (ventricular systole)
▪ Followed by a rest (diastole) when neither chamber is contracting (lowest point)–Diastolic arterial pressure is called the AFTERLOAD - the pressure against which the heart must work to eject blood during systole (systolic pressure)-the artery
-if this number is high the heart must work harder
-can lead to problems later on
What are the neural and endocrine signals that control the strength and rate of heart contractions?
- Sympathetic innervation (norepinephrine): increase heart rate (running a race)
- Parasympathetic innervation (Acetylcholine): decrease heart rate (sitting down not a lot of oxygen needed)
- Epinephrine: increase in strength of each contraction e.g. From rest to exercise:
- Heart rate can increase to nearly 200 bpm (max HR = 220 - age)- heart can really increase during this stage
- Cardiac output increases from 5 to 25 L/min (40 L/min in elite athletes**!)- really high amounts of blood
2 ** 40 Litres: TEN 4-litre milk jugs
What is conduction through the heart?
-understanding how the heart beats (is a muscle)
Electric signal is propagated by:
* Nodes-sends signals
healthy individual relies on -SA (sinoatrial) node (heart’s natural pacemaker: electrical impulses are generated here!)
* AV (atrioventricular) node
* Nerves- communicate with both atriums
* Bundle of His
* Bundle branches
* Purkinge fibres
* Intercalated discs (gap junctions)
Cardiac muscle consists of individual cardiomyocytes connected by intercalated discs (GAP JUNCTIONS!) (nerves move very fast)
to work together as a single functional organ
-ventricles connects to the atrium
What goes wrong when conduction occurs in the heart?
Some examples of miscommunication - usually results in some kind of arrhythmia:
* Abnormal sinoatrial (SA) node firing (can result in tachycardia- fast, bradycardia-slow)
* Blocks e.g. at the AV node, vary in terms of the degree of the blockage
* Can slow down or prevent signal propagation from atria to ventricles
* Ventricles can contract independently (bundle of His, 40 bpm)- slow heart beat
* Fibrillations are more serious, occurring when cells depolarize independently
-blocked at a certain point
Ventricular fibrillation, or V-fib, is considered the most
serious cardiac rhythm disturbance!
-heart is dying, can lead to death ventricles are not working properly
Atrial fibrillation (also called A-fib) is a quivering
or irregular heartbeat (arrhythmia)
-atrium is not working properly but the ventricles work
What is cardiovascular disease—artherosclerosis?
▪ 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 attack or stroke
▪ When this occurs in the arteries of heart
muscle, it is called coronary artery disease
Factors:
▪ Elevated blood lipids (fat flows through the blood), hypertension (High blood pressure),
inflammatory mediators (C-reactive protein)
▪ Diet (sodium, potassium, saturated/trans fats (don’t see as often),
cholesterol- not a risk because it is dietary
-becomes a concern when the body produces it
▪ Smoking, physical inactivity, obesity/diabetes
▪ Age, genetics
How are coronary artery blockages treated?
-build up of fatty acids
-low amounts of oxygen in blood blocks the arteries
-angioplasty
-a catheter and balloon are threaded into the coronary artery to the point of blockage (stent)
-the balloon is inserted into the blocked area
-forces the arteries to stay open
-plaque is pushed to the artery walls and held there by the stent
-bypass surgery: the vein is taken from arm or leg one end is attached above the blockage and the other below
-it is put into the thickest veins so it does not burst and the blood can get through
Is the enlargement of the heart as an adaptation good or bad?
-heart is working too hard and tries to grow
hypertrophy – a sign of being “overworked”. The heart muscle will respond and
hypertrophy just like your skeletal muscle would respond to weight-lifting.
The Bad: Causes include high blood pressure and narrowing of aortic valve … the heart must work harder to overcome these
The Good: Athlete’s heart – an appropriate adaptation! Occurs in both endurance athletes and weightlifters! ☺
Endurance athletes – mostly an increase in LV chamber (need to increase cardiac output)
Weightlifters – mostly increased LV wall and
septum thickness (need to overcome increased afterload – the amount of pressure needed to eject blood during ventricular contraction)
-has a thicker wall-chamber can get small
-depends how big the heart is
What is arterial blood pressure?
BP varies with cardiac cycle
Systolic blood pressure = maximum pressure
* When the ventricles contract, sending blood into the arteries
* Diastolic blood pressure = minimum pressure
* When the heart relaxes between beats - not zero due to elastic recoil of arterial wall
Contraction is called systole (e.g. arterial BP: 120 / 80)
Relaxation is called diastole (e.g. arterial BP: 120 / 80)
What is the neural control of artieriolar diameter?
-both depend on the location it is occuring in the body
-body prioritizes what needs oxygen
Vasoconstriction
* Alpha-receptors are located on arteries.
* Norepinephrine and epinephrine bind to 2 adrenergic
receptors
* This causes arteries to constrict (vasoconstriction)
* This increases blood pressure!
-diameter gets smaller which causes an increase in blood pressure
* E.g. during exercise
Vasodilation
* Blood vessels in skeletal muscles lack alpha-receptors
* Norepinephrine and epinephrine bind to b2 adrenergic
receptors found in arteries of skeletal muscle
* This dilates vessels of the skeletal muscles- arteries get bigger (vasodilation) so they can receive increased blood flow
* E.g. also during exercise!
What about with resistance exercise?
Resistance exercise (e.g. weightlifting) CAN cause dramatic increases in blood pressure—up to 345/245 mm-very high
-not chronic
-muscles are squeezed impacts arteries
-stable-increases after
-heart has to pump very high
Why?
Holding your breath – increases intrathoracic pressure during the lift – called the “Valsalva maneuver.”
Temporarily raises blood pressure and slows heart rate
What is the gastrointestinal tract (GI)?
GI tract represents a vast body surface area that
is exposed to the external environment.
* It “sees” not only our food, but potentially toxic
substances and infectious agents
* Unique mechanisms to deal with this:
* Sense and expel noxious substances
* vomit, diarrhea
-tries to get rid of this
* Specialized populations of T cells localized to
the intestinal mucosa
* E.g. Peyer’s patches
-clusters of lymphatic tissues
-immune response-first line of defense
-Muscular sphincters and valves partially segregate function within the tube
Includes:
oral cavity-upper esophogeal sphincter
esophagus-lower esophageal sphincter
stomach- pyloric sphincter
small intestine-
colon (large intestine)- anal sphincter
rectum
What are the GI tract’s unique properties?
~28 ft. long – has to be folded extensively in abdominal cavity
▪ Large luminal surface area of ~200-400 m2 due to lots of villi
/ microvilli (a tennis court is 264 m2)
-finger-like projections
▪ Highly variable transit time for ingested meal (total of 30-80 h)
▪ ~5-8 hours in stomach and small intestine
▪ Rest of time in the colon
▪ Houses resident gut microbiome (bacteria, etc.), protects
against pathogenic microbes that enter/reside in the tract.
-straight carbs that move throughout our body quicker than full meals (including fibre, proteins etc)
▪ Intrinsic (AKA enteric) nervous system to control and
coordinate all this functioning! (e.g. opening and closing of
sphincters)
-mesh-like containing neurons
What are the four basic processes?
Motility- how food moves through our body
* Peristalsis- automatic/ involuntary
-wave-like movement
Secretion
* Saliva, mucous
* Antibodies (IgA)- protect the surface against substances
* Digestive enzymes
* Bile- breaks down triglyceride
* Bicarbonate- buffer for acidity
-eliminates risks of cysts
-maintains pH
Digestion- break down of large molecules
Absorption
* Water- large intestine
* Nutrients- small intestine
What is the cephalic phase of digestion and absorption?
-cephalic means in the head region
❖ Chemical and mechanical digestion begins in the mouth- secretions
❖ Chewing (mastication)
❖❖ Secretions in response to sensory stimuli (sight, smell, taste) prepares the GI tract for food processing!
-makes you want to eat by producing saliva
❖ Salivary secretion is under autonomic control (stimulated by Sympathetic (inhibition of motor activity, less digestion occurs as the GI is inhibited) and Parasympathetic Nervous Systems)
- Softens and lubricates food
- Provides enzymes: amylase and some lipase- (but no protein digestion)
-amylase= enzyme that breaks down starch and carbs
-lipase= lipid enzyme that breaks down fats
What is the Gastric Phase of Digestion and Absorption?
- gastric= stomach
Secretory cells of the gastric mucosa – note the influence of the Parasympathetic Nervous System (“rest and digest”)
** - increases intestinal and gland activity, and relaxes sphincter muscles in the GI tract
-opening of the gastric gland= the lining of the stomach - various cell types in stomach are triggers for many chemical signals
Ex: chief cells trigger pepsin (ogen) and gastric lipase which triggers the release of acetylcholine (spike)- the release of fat breakdown
-after we consume a meal these levels are triggered
-spikes to signal release
Note: digestion of protein and fat, but not carbohydrate in the stomach.
-carbohydrate digestion starts in the mouth and in the small intestine
