Physiology exam prep 2

Cardiac Cycle

• The cardiac cycle is a rhythmic, coordinated contraction and relaxation of individual parts of the heart
• The entire cardiac cycle lasts for:
  • 0.8 seconds in humans
  • 1.4 seconds in horses
• There are three phases in the cardiac cycle:
  • Atrial systole (approximately 0.1 seconds)
  • Ventricular systole (approximately 0.3 seconds)
  • Total diastole or pause (approximately 0.4 seconds)

Ventricular Filling

• At the beginning of the cardiac cycle, both the atria and ventricles are relaxed (diastole)
• Blood flows into the right atrium from the superior and inferior venae cavae and the coronary sinus
• Blood flows into the left atrium from the four pulmonary veins
• The two atrioventricular valves (tricuspid and mitral valves) are open, allowing blood to flow from the atria into the ventricles
• Approximately 70-80% of ventricular filling occurs during this phase
• The two semilunar valves (pulmonary and aortic valves) are closed, preventing backflow of blood into the right and left ventricles

Atrial Contraction

• As the atrial muscles contract, pressure rises within the atria
• Blood is pumped into the ventricles through the open atrioventricular valves
• Atrial contraction contributes the remaining 20-30% of filling
• Atrial systole ends prior to ventricular systole, as the atrial muscle returns to diastole

Ventricular Systole

• Isovolumetric contraction:
  • The muscles in the ventricle contract, causing pressure to rise within the chamber
  • Blood pressure quickly rises above that of the atria, causing blood to flow back toward the atria
  • The tricuspid and mitral valves close, and the volume of blood within the chamber remains constant
• Ventricular ejection phase:
  • The contraction of the ventricular muscle raises the pressure within the ventricle
  • Blood is pumped from the heart, pushing open the pulmonary and aortic semilunar valves
  • Pressure generated by the left ventricle is appreciably greater than the pressure generated by the right ventricle

Diastole

• Early diastole (isovolumetric relaxation):
  • Ventricular relaxation causes pressure on the remaining blood within the ventricle to fall
  • When pressure within the ventricles drops below pressure in both the pulmonary trunk and aorta, blood flows back toward the heart
  • The semilunar valves close to prevent backflow into the heart
• Late diastole:
  • As the ventricular muscle relaxes, pressure on the blood within the ventricles drops even further
  • Blood flows from the atria into the ventricles, pushing open the tricuspid and mitral valves
  • The atrioventricular valves are open, and the semilunar valves remain closed

Process of Normal Expiration

• Expiration is a passive process impacted by:
  • Relaxation of the respiratory muscles
  • Lung elastic powers
  • Gravity of the chest cavity
  • Organs of the abdominal cavity that press on the diaphragm
• Self-regulation of expiration:
  • During inspiration, lungs stretch, and impulses through the afferent parasympathetic vagus fibers go to the respiratory center
  • Inspiratory neurons are suppressed, and they stop sending impulses to the spinal cord
  • Respiratory muscles relax, and lungs deflate
  • Expiratory neurons in the medulla oblongata are activated, inhibiting inspiratory neurons
  • Pons in the brain switches from inspiration to expiration
  • Information to the spinal cord is not sent, and the diaphragm and external muscles of the chest relax
  • The chest deflates, pressure in the pleural cavity increases
  • Lungs contract, and air flows out

Pancreas and Hormones

• Exocrine secretion: digestive enzymes target the duodenum
• Endocrine secretion: pancreatic islets (islets of Langerhans) produce:
  • α cells: glucagon (increases glucose level in the blood)
  • β cells: insulin (decreases glucose level in the blood), amylin (centrally acting, neuroendocrine hormone)
  • δ cells: somatostatin (inhibits the release of glucagon and insulin)
  • PP cells: pancreatic polypeptide (inhibits gastrointestinal movement and pancreatic secretion, gallbladder contraction)

Physiological Roles of Hormones

• Insulin:
  • Absolutely necessary for life-support
  • Impacts metabolism of proteins, carbohydrates, and fats
  • Main target organ is the liver
• Glucagon:
  • Impacts metabolism of proteins, carbohydrates, and fats
  • Increases glucose level in the blood
• Hypoglycemia:
  • Decreases blood glucose level
  • Increases permeability of the cell membrane to glucose
  • Increases glycogen synthesis in the liver and muscles
  • Increases protein and fat synthesis
• Hyperglycemia:
  • Increases blood glucose level
  • Glycosuria begins (renal threshold for glucose is 10 mmol/L in dogs and 16 mmol/L in cats)
  • Polyuria and polydipsia occur
  • Fat oxidation (degradation) processes stop in the intermediate stage
  • Incompletely oxidized metabolic products (ketones) accumulate in the body, leading to acidosis

Types of Hypoxia

• Hypoxic hypoxia: decreased pO2 in arterial blood
• Anemic hypoxia: pO2 in arterial blood is normal, but the amount of hemoglobin is decreased
• Ischemic (stagnant) hypoxia: arterial blood supply to tissues is impaired
• Histotoxic hypoxia: pO2 and transport of O2 is normal, but tissues are unable to use O2 due to toxins

Neural Regulation of Renal Functions

• Sympathetic nervous system:
  • Kidney blood vessels constrict
  • Blood supply to the kidneys decreases
  • Filtration processes decrease
  • Diuresis decreases
• Parasympathetic nervous system:
  • Blood vessels dilate
  • Blood supply to the kidneys increases
  • Filtration processes increase
  • Diuresis increases
• In case of pain:
  • Regulation through the cerebral cortex
  • Increases the release of ADH in the hypothalamus
  • Sympathetic nervous system intensifies
  • Blood vessels constrict
  • Decreases blood supply to the kidneys
  • Decreases filtration processes and diuresis

Cardiac Conduction System

• The cardiac conduction system is responsible for generating and conducting electrical impulses in the heart.
• It consists of five elements:
  • Sinoatrial (SA) node: generates the action potential and is located in the posterior wall of the right atrium.
  • Atrioventricular (AV) node: located in the interatrial septum.
  • Bundle of His: divides into two bundles (left and right).
  • Bundle branches: branch into Purkinje fibers.
  • Purkinje fibers: branch into the myocardium.
• The speed of conduction of excitation in the heart varies in different parts:
  • SA node to left atrium: 1 m/sec.
  • AV node: 0.1 m/sec (slowest conduction speed, known as AV delay).
  • Bundle of His: 4 m/sec (fastest conduction speed).
  • Ventricles: approximately 1 m/sec.

Functions of the Digestive Tract

• The digestive tract has five main functions:
  • Secretory function: glands secrete digestive juices.
  • Motor function: performs mechanical processing of food.
  • Absorption function: allows water and broken nutrients to enter the bloodstream and lymph.
  • Excretory function: releases substances or metabolites not used by the body.
  • Incretory function: hormones produced by endocrine cells enter the bloodstream.
  • Receptor function: induces various functions, such as gastric emptying reflex and intestinal peristalsis.

Physiological Effects of Progesterone

• Progesterone is a pregnancy protection hormone produced in the corpus luteum.
• Its effects on the uterus and mammary glands:
  • Prepares the uterus for fertilization.
  • Promotes the fixation of the fertilized ovum.
  • Inhibits the effect of oxytocin on the smooth muscle of the uterus.
  • Inhibits the development of follicles in the ovaries.
  • Promotes the development of mammary gland alveoli.
  • Protects pregnancy and stops the growth of new follicles.
  • Stimulates udder development during pregnancy.
  • Keeps parturition and lactogenesis in check.

Electrocardiogram (ECG)

• The ECG records the electrical activity of the heart.
• It provides information about:
  • The origin of excitation in the heart.
  • Cardiac arrhythmias.
  • Transmission of excitation in the heart.
  • Metabolic disorders in the myocardium.
  • Heart pathologies, such as heart attack.
• Waves and intervals on the ECG:
  • P wave: represents atrial depolarization.
  • PR interval: time between the start of the P wave and the start of the QRS complex.
  • QRS complex: represents rapid depolarization of the ventricles.
  • ST segment: represents the period when the ventricles are depolarized.
  • T wave: represents ventricular repolarization.
  • QT interval: duration of ventricular depolarization and repolarization.
  • RR interval: duration of the ventricular cardiac cycle.

Spontaneous and Induced Ovulation

• Types of ovulation:
  • Spontaneous ovulation: occurs independently of copulation (e.g., cows, sheep, dogs, humans, horses).
  • Induced ovulation (reflex ovulation): requires copulation for ovulation to occur (e.g., cats, mink, rabbits, camels).

Motility of the Stomach

• Gastric motility:
  • Provided by three layers of muscles (external, middle, and internal).
  • Ensures mechanical processing of food.
  • Tonic movements: typical of an empty stomach.
  • Peristaltic movements: typical of a full stomach.
  • Receptive relaxation: allows the stomach to stretch without high resistance and pressure increase.
• Evacuation of food from the stomach to the duodenum:
  • Regulated by the pyloric reflex.
  • pH receptors and stretch receptors stimulate the pyloric reflex.
  • Alkaline pancreatic juice, bile, and duodenal juice neutralize the acidity of the food.
  • Gastric emptying rate depends on the chemical content and physical properties of the food.

Vomiting and Regurgitation

• Vomiting: a protective reaction to remove harmful substances from the stomach.
  • Caused by direct irritation of receptors in the tongue, throat, vestibular apparatus, and gastric mucosa.
  • Caused by central irritation of the vomiting center.
• Regurgitation: the passive, retrograde expulsion of previously swallowed material from the esophagus, stomach, or rumen.
  • Often a clinical symptom, but can also be associated with a conditioned reflex to feed young.

Respiration Impact on Heart Rate and Blood Pressure

• Respiratory function influences the venous return to the heart, enhancing venous return through the respiratory pump.
• Increased pressure difference between the abdominal and thoracic vena cava during inspiration increases venous return to the heart.
• Respiratory system participates in the regulation of acid-base balance, responding to changes in CO2 levels to normalize H+ concentration.
• Respiratory system regulates blood pressure via the renin angiotensin-aldosterone system, converting Angiotensin I to Angiotensin II in the lungs.

Respiratory-Induced Fluctuations in Blood Pressure

• Pulsatory oscillations (first-degree waves) correspond to the heart rhythm, with pressure increasing after ventricular systole and decreasing after total diastole.
• Respiratory fluctuations (second-order waves) correspond to the rhythm of breathing, with blood pressure decreasing during inspiration and increasing during expiration.

Sinus Rhythm and Arrhythmia

• Sinus rhythm is a normal heart rhythm, while sinus arrhythmia is a normal variation of sinus rhythm with irregularities on ECG.
• Sinus rhythm is influenced by the autonomic nervous system, with the parasympathetic nervous system slowing down the heart rate and the sympathetic nervous system increasing it.

Hypertension and Hypotension

• Hypertension is high blood pressure, while hypotension is low blood pressure.

Digestion in the Small Intestine

• The small intestine is responsible for digestion and absorption of nutrients from food.
• Digestion occurs through mechanical and chemical processing, with the help of digestive enzymes and juices.
• The small intestine has a large surface area with villi and microvilli, increasing the absorption of nutrients.

Regulation of Digestion

• The autonomic nervous system, including the parasympathetic and sympathetic nervous systems, regulates digestion and secretion of digestive juices.
• Neurotransmitters and neuromodulators, such as acetylcholine, serotonin, and vasoactive intestinal peptide, play a crucial role in regulating digestion.

Arteries

• Arteries are elastic blood vessels that equalize blood flow, making it continuous.
• Arteries are divided into three types based on their structure: elastic type, muscle type, and mixed type.

Motility in the Small and Large Intestine

• Motility is the coordinated contractions and relaxations of muscles necessary to move contents from the mouth to the anus.
• Peristalsis is a type of motility that occurs in the small intestine, ensuring mixing of food substances, mixing with digestive juices, and pressing the food substances to the intestinal wall.
• The large intestine has slower movements than the small intestine, with peristaltic, segmental, and antiperistaltic waves.

Functions of Capillaries

• Capillaries have a circulatory function, regulating the flow of blood to tissues and organs, and a metabolic function, associated with the movement of substances through the capillary wall.
• The number of capillaries in different organs depends on their intensity of metabolism.

Movement of Substances through the Capillary Wall

• Substances move through the capillary wall through diffusion, osmosis, active transport, filtration, and reabsorption.
• Diffusion occurs through a concentration gradient, with passive diffusion occurring more slowly and active diffusion occurring more quickly.
• Osmosis occurs due to osmotic pressure gradient, with dissolved substances moving from higher concentration to lower concentration.
• Active transport involves the use of energy to move substances against their concentration gradient.
• Filtration and reabsorption occur due to hydrostatic and oncotic pressure gradients, with filtration occurring at the arterial end and reabsorption occurring at the venous end of the capillaries.

Pancreas Function

• The pancreas has both exocrine and endocrine functions.
• Exocrine function: • Synthesizes and secretes enzymes (zymogens) to avoid self-digestion. • Secretes bicarbonate ions to neutralize acidic chyme from the stomach. • Controlled by hormones gastrin, cholecystokinin, and secretin from the stomach and duodenum in response to food.

Pancreatic Juice

• Organic components of pancreatic juice include: • Proteases (zymogens): trypsinogen, chymotrypsinogen, carboxypeptidase, and aminopeptidase. • Lipases: pancreatic lipases. • Amylases: α-amylase, maltase, lactase, and sucrase.
• Inorganic component: Na bicarbonate, which gives an alkaline reaction.

Humoral Regulation of Pancreatic Secretion

• Secretin: • Stimulates the release of sodium bicarbonate in pancreatic juice. • Inhibits gastrin secretion in the stomach. • Stimulates liver secretion of bile. • Regulates water homeostasis in the body.
• Cholecystokinin (CCK) or Pancreozymin: • Stimulates the pancreas to release enzymes like amylase, lipase, and trypsin. • Stimulates the release of stored bile from the gallbladder. • Inhibits motility and closes the pyloric sphincter.

Lymph Formation and Circulation

• Lymph forms when blood plasma passes through capillary walls into the tissue fluid.
• Lymphatic capillaries are highly permeable, allowing substances to pass quickly from tissues into the lymph.
• Lymph has a composition similar to blood plasma but with less protein.
• Lymphatic flow is promoted by: • Smooth muscle elements (lymphangions) in lymphatic vessels that contract regularly. • Skeletal muscle contractions. • Respiratory movements.

Leydig and Sertoli Cells

• Leydig cells: • Produce testosterone, stimulating sperm production, male sex characteristics, psychological development, and sex drive. • Located outside seminiferous tubules.
• Sertoli cells: • Support the development of spermatozoa mechanically. • Supply nutrients to developing spermatozoa. • Participate in the regulation of spermatogonia differentiation into spermatozoa. • Produce inhibin, which inhibits FSH secretion from the anterior pituitary gland.

Digestion in the Large Intestine

• The large intestine mainly absorbs water and salts.
• The pH of chyme is important for enzyme activity.
• Fermentation and putrefaction processes occur in the large intestine, producing vitamins (B6, K, biotin, folic acid).
• Defecation is a combination of voluntary and involuntary processes regulated by the sacral segments of the spine and the cerebral cortex.

Respiratory System Functions

• Gas exchange between the lungs and blood by diffusion.
• Maintains acid-base balance in the body.
• Acts as an excretory system, eliminating water, volatile substances, and CO2.
• Participates in thermoregulation, venous return to the heart, and humoral regulation.
• Provides immune protection, analyzes inhaled air, heats, moistens, and cleans it.

Colostrum

• A secretion accumulating in the mammary glands before parturition.
• Different composition than milk, with more fat, proteins, minerals, and vitamins.
• Contains immunoglobulins, which provide passive immunity to offspring.
• Helps protect against infection, and is critical for young animals in industrial conditions.

Insulin Release and Function

• Insulin is released from beta cells into the blood in response to glucose, amino acids, and fatty acids.
• Stimulates cellular uptake of glucose, amino acids, and fatty acids, promoting nutrient incorporation into cellular stores.
• Lowers blood glucose, amino acid, and fatty acid concentrations.
• Promotes glycogen synthesis, inhibits gluconeogenesis, and stimulates protein synthesis and triglyceride synthesis.

Types of Immunity

• Innate (inborn) immune system: • Mediates rapid response to pathogens. • Responds without prior exposure. • Not specific. • Includes physical barriers, antimicrobial proteins, and phagocytosis.
• Adaptive (acquired) immune system: • Develops after birth. • Reacts more slowly. • More effective. • Highly specific. • Involves lymphocytes (B-cells and T-cells).

Lipids in the Body

• Lipids are a group of naturally occurring molecules that include fats, sterols, phospholipids, and others
• Made up of glycerol and fatty acids
• Relatively insoluble in water, but soluble in nonpolar solvents like ether, chloroform, benzole, and acetone
• Stored in adipose tissue, serving as thermal and electrical insulators
• Important components of cell and mitochondrial membranes
• Lipoproteins serve as a means of transport of lipids in blood

Types of Lipids

• Neutral lipids (fats and oils)
  • Functions: energy source, insulation, protection, carrier for fat-soluble vitamins
• Polar lipids (phospholipids and glycolipids)
  • Phospholipids: structural components of cell membranes, emulsifiers, and important for lipid absorption and transport
  • Glycolipids: lipids containing fatty acid, sphingosine, and carbohydrate
• Brown adipose tissue: high density of mitochondria, present in newborn animals, and important for heat generation

Veins and Blood Circulation

• Veins are volume or capacity blood vessels due to their ability to stretch easily and fill with blood
• Veins regulate blood flow to the heart, especially from the extremities against gravity
• Factors promoting blood circulation in veins:
  • Skeletal muscles
  • Venous valves
  • Respiratory movements
  • Suction action of the heart
• Venous pulse: volume fluctuations of the veins, detected in veins close to the heart, reflecting the activity of the right side of the heart

Hormones Regulating Appetite

• Regulated by a center located in the hypothalamus
• Feeling of hunger is caused by:
  • Afferent nerves from the stomach and intestines
  • Changes in physical-chemical properties of blood (i.e., "hunger blood")
• Hormones regulating appetite:
  • Ghrelin: orexigenic (stimulates appetite), released from the stomach wall when empty
  • Leptin: anorexigenic (suppresses appetite), released from adipocytes (fat cells)
  • Insulin: suppresses appetite, released from beta cells in the pancreas
  • PYY (peptide tyrosine tyrosine): suppresses appetite, released from cells in the ileum and colon in response to feeding

Cellulose Breakdown in Ruminants

• Cellulose and carbohydrate breakdown in the forestomach of ruminants
• 60-70% of digestible cellulose is broken down in the forestomach
• Bacterial enzyme cellulase breaks down cellulose into cellobiose, then further broken down into glucose, eventually forming volatile fatty acids

Pulmonary Surfactant

• A surface-active complex of phospholipids and proteins formed by alveolar cells
• Creates a hydrophobic film lining the internal surface of the lungs
• Functions:
  • Reduces surface tension
  • Gives alveoli a round shape and prevents collapse during exhalation
  • Has anti-inflammatory action and helps lyse microorganisms
  • Regulates oxygen diffusion through the alveolar wall
  • Prevents fluid accumulation in alveoli
  • Makes breathing easier

Phosphorus

• Found in both organic and inorganic forms in the body
• Most present in bone tissue and teeth (80-85%) and soft tissues and fluids (15-20%)
• Functions:
  • Important in bone and cartilage composition
  • Component of phospholipids, nucleic acids, and phosphoproteins
  • Involved in energetic processes and cell metabolism
  • Helps maintain normal pH of body fluids
• Deficiency symptoms:
  • Osteomalacia
  • Rickets
  • Joint stiffness
  • Muscular weakness
  • Pica
  • Reduced growth and reproduction
• Toxicity symptoms:
  • Kidney stones
  • Interferes with calcium absorption

Respiratory System Resistance

• Total resistance of the breathing process consists of non-elastic and elastic resistance
• Non-elastic resistance (~35%):
  • Viscous resistance (7%)
  • Air flow resistance (28%)
  • Influenced by air flow patterns (laminar or turbulent) and airway diameter
• Elastic resistance (~65%):
  • Created by chest, respiratory, and lung tissue compliance
  • Influenced by lung volume, body posture, and blood supply

Protein Splitting in Ruminant Forestomach

• Proteins broken down into peptides and amino acids by microbial enzymes
• Amino acids deaminated to form ammonia, which is used by bacteria to synthesize their own proteins
• Urea circulation: ammonia in liver → urea → salivary glands → saliva → forestomach → urease → ammonia and CO2
• Nitrogen circulation: ammonia in forestomach → liver → urea → salivary glands → saliva → forestomach
• Methane and CO2 produced in fermentation process, released through belching and exhalation

Mechanisms of Conduction of Excitation in Nerve Fibers

• Unmyelinated nerve fibers:
  • Depolarization and circular powers occur
  • Action potential (AP) propagates along the axon
  • Neurotransmitter release at the synapse
• Myelinated nerve fibers:
  • Myelin sheath provides electrical insulation
  • Saltatory conduction occurs, where the AP jumps from node to node
  • Thicker nerve fibers have faster conduction

Erythropoiesis

• Process of red blood cell production
• Stimulated by:
  • Decreased partial pressure of oxygen in blood plasma
  • Increased erythropoietin in blood plasma
  • Androgens, thyroxine, and somatotropic hormone
• Vitamins and minerals essential for RBC maturation:
  • Vitamin PP (niacin)
  • Vitamin B12
  • Iron, copper, and cobalt
• Erythropoietin production is stimulated by renal hypoxia or extirpation, increased lactic acid, and anemia

Neural Regulation

• More precise and faster than humoral regulation
• Uses nerve fibers to send information to the tissue response group
• Reflex arc consists of:
  1. Sensory receptor
  2. Sensory (afferent) neuron
  3. Internouron in the central nervous system
  4. Motor (efferent) neuron
  5. Effector (target organ)

Reflexes

• Inborn (unconditioned) reflexes:
  • Autonomic (related to internal organs)
  • Somatic (related to skeletal muscles)
• Acquired (conditioned) reflexes:
  • Developed through temporary connections in the cerebral cortex
  • Serve as mechanisms for adaptation to changing environmental conditions

Hemolysis

• Breakdown of red blood cells
• Physiological hemolysis:
  • Occurs mainly in the spleen and liver
  • Damaged erythrocytes are identified and phagocytized by macrophages
  • Hemoglobin is released and broken down
• Pathological hemolysis:
  • Can lead to jaundice and anemia
  • Causes include genetic defects, infections, and medications

Mechanism of Excitation in Chemical Synapses

• Excitation in chemical synapses occurs when Ca2+ enters the presynaptic cell due to the concentration gradient, being higher outside the cell than inside.
• The entering Ca2+ binds with calmodulin, a multifunctional intermediate calcium-binding messenger protein, triggering the migration of vesicles filled with neurotransmitters towards the presynaptic membrane.
• The vesicles release the neurotransmitters, which then travel across the synapse to the postsynaptic membrane.

Transmission of Excitation

• The neurotransmitters bind to their specific receptors located only on the postsynaptic membrane, allowing the excitation to be transmitted.
• The transmission of excitation occurs in one direction, from the presynaptic membrane to the postsynaptic membrane.

Synaptic Delay

• The time period between the release of the neurotransmitter and its binding to the receptor channel is less than a millisecond, referred to as the synaptic delay.
• The synaptic delay is the brief period during which the excitation spreads through the synapse.