PCB4723C Exam 4 Review Questions

What are some key features of an open circulatory system?

- Hemocoel spaces or cavities in body tissues that separate the artery from the vein.

- Hemolymph moves through vessels that open into extracellular spaces.

What are some key features of a closed circulatory system?

- Blood is pumped from a heart through vessels that return blood to the heart.

- Closed circulatory systems have capillaries which are the primary structure distinguishing a closed circulatory system from an open one.

What is the role of the spleen in the maintenance of blood components?

The spleen removes old erythrocytes and stores healthy erythrocytes, platelets and lymphocytes.

What is the role of bone marrow in the maintenance of blood components?

Hemopoietic tissues (aka red bone marrow in birds/mammals) generate new erythrocytes in a process called erythropoiesis.

What does erythropoietin do?

Erythropoietin (EPO) is secreted by the kidneys to stimulate red blood cell production in response to low oxygen in the blood.

What are platelets and where do they come from in mammals?

- Platelets are cell fragments circulating in mammalian blood.

- Platelets shed from megakaryocytes in bone marrow.

Platelets are stimulated by thrombopoietin (from the liver)

What does thrombopoietin do?

Thrombopoietin stimulates the production of platelets.

What is the role of platelets in homeostasis?

-Platelets form platelet plugs by sticking to exposed collagen, then sticking to each other, forming a plug.

- These plugs maintain homeostasis by secreting chemicals that induce vasoconstriction and enhance blood coagulation.

What is the first of the clotting factors that begins the clotting cascade?

Factor XII is the first factor that triggers the clotting cascade.

What does prothrombin do?

Prothrombin activates thrombin which promotes blood clotting.

What does thrombin do?

Thrombin converts fibrinogen into fibrin.

What does fibrinogen do?

Fibrinogen helps in blood clotting.

What does fibrin do?

Fibrin, an insoluble thread-like molecule, forms a stabilized meshwork at the site of a platelet plug and forms the clot.

What is the role of plasmin?

Plasmin dissolves clots

How is plasmin activated from plasminogen?

Factor XII triggers a cascade of reactions leading to activation of plasminogen (produced by the liver) to form plasmin.

How many chambers do fish hearts have?

Two primary chambers

Explain the roles of Na+, Ca2+, and K+ in generating pacemaker potentials in the mammalian heart, including when specific channels are open/closed.

Membrane potential of pacemaker cells slowly depolarizes due to:

- Increased inward Na+ current

- Decreased outward K+ current

- Increased inward Ca2+ current

What is the plateau phase in regards to action potentials in the heart and what causes it?

The plateau phase is a period of relatively stable membrane potential following a rapid depolarization phase. It happens due to the opening of 'slow' L-type Ca2+ channels and the closing of K+ channels. Ca2+ slowly flows inward, prolonging positivity inside the cell.

What is the function of the plateau phase during cardiac action potentials?

Plateau phases prolong ventricular contractions to aid pumping.

Label the major features on an ECG (PQRST) and explain what each corresponds to in terms of electrical activity of the heart.

P wave represents atrial depolarization

QRS complex represents ventricular depolarization

T wave represents ventricular repolarization

What happens during the early ventricular diastole step of the cardiac cycle?

- AV valves are open; aortic and pulmonary valves are closed

- Blood flows from veins into atria into ventricles

What happens during the late ventricular diastole step of the cardiac cycle?

- SA node fires and atria depolarize (P wave)

- Atria contract, increasing atrial pressure

What happens during the end of ventricular diastole step of the cardiac cycle?

Ventricular filling is completed (end-diastolic volume)

What happens during the ventricular excitation and onset of ventricular systole step of the cardiac cycle?

- Impulse passes through AV node and bundle of His and depolarizes ventricles (QRS complex)

- Ventricles contract, increasing pressure

- AV valves close

What happens during the isovolumetric ventricular contraction step of the cardiac cycle?

Ventricles are closed chambers while ventricular pressure rapidly rises

What happens during the ventricular ejection step of the cardiac cycle?

- When ventricular pressure exceeds arterial blood pressure, aortic and pulmonary valves open

- Blood is forced into arteries and ventricular volume decreases substantially

What happens during the end of ventricular systole step of the cardiac cycle?

- Ventricular emptying is completed

- Amount of blood pumped out is the stroke volume

What happens during the ventricular repolarization and onset of ventricular diastole step of the cardiac cycle?

- Ventricles repolarize (T wave)

- Ventricular pressure falls below arterial blood pressure and aortic and pulmonary valves close

What happens during the isovolumetric ventricular relaxation step of the cardiac cycle?

Ventricles are closed chambers while ventricular pressure rapidly falls.

What happens during the ventricular filling step of the cardiac cycle?

- When ventricular pressure falls below arterial pressure, AV valves open

- Ventricles begin to fill with blood

What are the two factors that determine cardiac output?

Cardiac output is determined by heart rate and stroke volume

Cardiac output = heart rate x stroke volume

What variables can affect heart rate and stroke volume?

- Heart rate is determined by antagonistic regulation by the autonomic nervous system

-End diastolic volume (EDV) and sympathetic stimulation have direct affects on stroke volume

How does parasympathetic stimulation affect heart rate?

Heart rate decreases under parasympathetic stimulation

How does sympathetic stimulation affect heart rate?

Heart rate increases under sympathetic stimulation

How does sympathetic stimulation affect ventricular contractility?

Sympathetic stimulation enhances contractility of the heart.

How does sympathetic stimulation affect stroke volume?

Sympathetic activity increases stroke volume.

How does venous return (end diastolic volume) affect stroke volume of the heart and how is this affected by sympathetic stimulation?

There is a direct correlation between end-diastolic volume (EDV) and stroke volume. Sympathetic activity increases venous return which increases stroke volume

What is coronary circulation?

Through coronary circulation, the heart receives its blood supply

What is the role of adenosine in coronary circulation?

Adenosine induces the dilation of coronary vessels.

What two factors determine the flow rate through blood vessels?

The pressure gradient and resistance determine the flow rate through blood vessels

What is the most important factor determining vascular resistance?

The radius of the vessel

How many chambers are in an amphibians heart?

Three chambers with two atria

How many chambers are in a reptiles heart?

Three chambers

How many chambers are in crocodiles hearts?

Four chambers with 2 atria and 2 ventricles

How many chambers are in birds and mammals hearts?

Four chambers with no shunts

How do you calculate mean arterial pressure?

Mean arterial pressure = diastolic pressure + 1/3(systolic pressure - diastolic pressure)

What are the important intrinsic and extrinsic factors that cause vasoconstriction or vasodilation of arterioles, respectively?

Vasoconstriction results from smooth muscle contraction --> decreased radius, increased resistance.

Vasodilation results from smooth muscle relaxation --> increased radius, decreased resistance

What is the function of precapillary sphincters?

Precapillary sphincters control flow through individual capillaries.

What causes precapillary sphincters to relax or constrict?

A decrease in O2 and an increase in CO2 and other metabolites causes the relaxation of precapillary sphincters

What are the four types of pressures that allow bulk flow to occur from capillaries and then back into venules?

- Capillary blood pressure (Pc)

- Plasma colloid osmotic pressure (πp)

- Interstitial fluid hydrostatic pressure (Pif)

- Interstitial fluid colloid osmotic pressure (πif)

Explain the function of the lymphatic system in managing interstitial fluids?

- The lymphatic system returns excess filtered fluid to the blood

- Interstitial fluid enters small blind ended terminal vessels to form lymph

- Lymph vessels flow into the venous system near heart

- Passage of lymph through the lymph nodes aids in immune defense against disease

What keeps the movement of venous blood flow to the heart going in one direction?

Venous one way valves in large vessels prevent blood from flowing backwards or away from the heart

What mechanisms enhance venous blood flow to the heart?

- Driving pressure of cardiac contraction

- Sympathetic activity produces venous vasoconstriction

- Repeated contraction of skeletal muscles compresses veins

From Figure 9-67, understand all of the mechanisms that determine mean arterial blood pressure.

Ok

From Figure 9-65, understand how the baroreceptor reflex works, how the sympathetic and parasympathetic systems respond to blood pressure, and how the heart and blood vessels respond to these stimuli.

Okay

What are the four basic digestive processes?

Motility, secretion, enzymatic hydrolysis & absorption

What occurs during the basic digestive process of motility?

- Muscular contraction that mix the contents of the digestive tract and move them forward

- Due to smooth muscle in the walls of the digestive organs controlled by complex autonomic mechanisms

What occurs during the basic digestive process of secretion?

- Digestive juices are secreted into the lumen of the digestive tract by exocrine glands

- Each secretion contains water, electrolytes, and organic molecules important in the digestive process

What occurs during the basic digestive process of enzymatic hydrolysis?

- Complex food molecules are broken down into smaller absorbable units

- Carbohydrates are hydrolyzed into monosaccharides

- Proteins are hydrolyzed into amino acids

- Fats are hydrolyzed into monoglycerides and FAs

- Nucleic acids are hydrolyzed into nucleotides

What occurs during the basic digestive process of absorption?

- Small absorbable units, along with water, vitamins and electrolytes, are transferred from the digestive tract into blood or hemolymph

- Involves specialized transporters in epithelial cells

What are slow wave potentials and how are they involved in gastrointestinal motility?

Slow wave potentials are fluctuations in membrane potential (myogenic).

What are the main components of saliva?

Water, mucus, and salivary amylase

What are some important functions of saliva?

- Moistening food

- Digestion

- Defense

- Taste

- Neutralization of acids

- Thermoregulation

What is the main stimulus that causes the simple salivary reflex?

Saliva is produced by salivary glands. The salivary center in the medulla must be activated.

What anatomical structures and movements are involved in the swallowing reflex?

- Uvula is elevated and seals of the nasal passage

- Glottis is closed and covered by the epiglottis to prevent food from entering the respiratory airways

- Pharyngeal muscles contract to force bolus into esophagus

What specific cell in the stomach secretes mucous cells, chief cells, and parietal cells?

Oxyntic mucosa cells

What specific cell in the stomach secretes endocrine G cells?

Pyloric gland area cells

What do mucous cells secrete?

A thin, watery mucus

What do chief cells secrete?

Pepsinogen

What do parietal cells secrete?

HCl and intrinsic factor

What do G cells secrete?

Gastrin into the blood

What do enterochromaffin-like cells secrete?

Histamine

What do D cells secrete?

Somatostatin

What are the mechanisms and transporters that produce and secrete acid in the stomach?

- Parietal cells secrete acid

- Carbonic anhydrase = CO2 + H2O → H+ + HCO3-

- Proton pump = H+/K+ ATPase & H+ pumped out into lumen

- HCO3-/Cl- exchanger = HCO3- into plasma & Cl- follows H+ into lumen

What is the function of pepsin?

Pepsin digests proteins in a low pH environment

How is pepsin activated?

Parietal cells secrete HCl

Chief cells secrete pepsinogen

HCl cleaves pepsinogen to pepsin

What is the cephalic phase of gastric secretion?

Anticipatory secretion of HCl and pepsinogen due to food related stimuli

What are the three stimuli for acid secretion in the cephalic phase?

Acetylcholine, gastrin, and histamine

What is the gastric phase of secretion?

Stimuli (e.g. food) acting in the stomach -- protein distension, caffeine, and alcohol

Explain the excitatory components of the intestinal phase of gastric secretion.

Excitatory component - presence of protein fragments in duodenum

Explain the inhibitory component of the intestinal phase of gastric secretion.

Inhibitory component - Duodenal distension and low pH inhibit gastric secretion

What are the digestive secretions of the exocrine pancreas and what does each accomplish?

- Pancreatic amylase converts polysaccharides to disaccharides

- Pancreatic proteases digest proteins

- Pancreatic chitinase breaks down chitin

- Pancreatic lipase hydrolyzes triglycerides into monoglycerides and free fatty acids

- Sodium bicarbonate is secreted by pancreatic duct cells to neutralize acidic contents arriving from the stomach.

What is the role of secretin in stimulating pancreatic secretions?

Secretin stimulates the secretion of sodium bicarbonate

What is the role of cholecystokinin in stimulating pancreatic secretions?

Cholecystokinin stimulates the secretion of pancreatic digestive enzymes

What are some of the functions of the liver in digestion and metabolism?

- Secretion of bile salts

- Metabolic processing of nutrients

- Detoxification of body wastes, hormones and drugs

- Synthesis of plasma proteins and lipoproteins

- Storage of glycogen, fats, iron, copper, and vitamins

- Activation of vitamin D

- Removal of bacteria and worn out red blood cells

- Secretion of hormones

- Excretion of cholesterol, biliverdin, and bilirubin

- Synthesis of ascorbic acid (Vitamin C)

- Buoyancy in sharks

What is the function of bile salts in lipid digestion?

- Bile salts aid digestion of fats

- Bile salts break large lipid droplets into smaller ones

- Bile salts form micelles around lipid molecules for dispersion through the watery contents of the lumen

What are the purposes of segmentation and the migrating motility complex in the small intestine?

- Segmentation both mixes and slowly propels chyme

- After absorption is complete, segmentation is replaced by the migrating motility complex

- Weak peristaltic waves sweep remaining debris towards the large intestine

How are glucose, galactose, and amino acids absorbed in the small intestine?

- Glucose and galactose are absorbed by secondary active transport with Na+ as a cotransporter

- Amino acids are absorbed by secondary active transport similar to glucose transport

What are the primary functions of the large intestine?

Absorbing water & electrolytes, producing and absorbing vitamins, and forming and propelling feces toward the rectum for elimination

What are haustral contractions?

Contractions that impede the flow of materials

What is the role of smooth muscle in defecation?

Internal anal sphincter (smooth muscle) relaxes and the rectum and sigmoid colon contract more vigorously

What is the role of skeletal muscle in defecation?

Defecation occurs when the external anal sphincter (skeletal muscle) is voluntarily relaxed

What are micelles and how do they contribute to lipid absorption?

Micelles are tiny balls of bile salts and lipids that help fats mix with water in your intestines. They carry digested fats to the surface of intestinal cells so they can be absorbed into the body.

What are chylomicrons and how do they contribute to lipid absorption?

Chylomicrons are tiny fat-carrying particles made in intestinal cells. They transport absorbed fats from the intestines into the bloodstream so the body can use or store them.

What do stem cells in the bone marrow produce?

Red and white blood cells

What are AV valves and AV nodes?

- Right and left atrioventricular (AV) valves allow flow from atria into ventricles during ventricular filling

- Atrioventricular (AV) node transmits impulses between the atria and the ventricles

Gap junctions in cardiac muscle fibers serve what purpose?

Gap junctions allow electrical activity to flow between cells to create a coordinated muscle contraction.

What is the difference between systole and diastole?

Systole is the period of contraction and emptying whereas diastole is the period of relaxation and filling

Where is blood pressure highest and lowest?

Pressure is highest in the arteries, blood pressure drops going into the arterioles, lowest pressure is in the veins