Physiology exam prep 3

Urine Characteristics and Composition

• Urine volume can vary, with polyuria (increased urine output) often accompanied by polydipsia (excessive thirst)
• Oliguria (decreased urine output) and anuria (no urine output) can occur in cases of severe dehydration, shock, urinary tract obstruction, acute kidney failure, and hypoadrenocorticism

Urine Color

• Red or reddish-brown urine can indicate hematuria (blood in urine)
• Timing of red color during urination can indicate source of bleeding: end of urination (bladder), beginning (urethra or genital organs), or entire urination (kidneys, hemoglobinuria, or myoglobinuria)
• Yellowish-green urine can indicate bilirubinuria (bilirubin in urine)

Urine Transparency

• Fresh urine is typically transparent
• Cloudy urine can indicate pathological components, such as pus
• Horse urine is normally cloudy
• Urine can become cloudy during storage due to crystal formation and bacterial growth

Urine Smell

• Fresh urine with an ammonia smell can indicate pathology, such as cystitis, pyelitis, pyelonephritis, or urinary retention
• Fresh urine with an acetone smell can indicate hyperketonemia due to ketosis or diabetes
• Fresh urine with a putrid smell can indicate gangrenous processes in the urinary tract

Urine Density

• Hypersthenuria: increased urine density due to high salt concentration, with less impact from proteins
• Hyposthenuria: decreased urine density

Urine Characteristics and Composition

• Urine volume can vary, with polyuria (increased urine output) often accompanied by polydipsia (excessive thirst)
• Oliguria (decreased urine output) and anuria (no urine output) can occur in cases of severe dehydration, shock, urinary tract obstruction, acute kidney failure, and hypoadrenocorticism

Urine Color

• Red or reddish-brown urine can indicate hematuria (blood in urine)
• Timing of red color during urination can indicate source of bleeding: end of urination (bladder), beginning (urethra or genital organs), or entire urination (kidneys, hemoglobinuria, or myoglobinuria)
• Yellowish-green urine can indicate bilirubinuria (bilirubin in urine)

Urine Transparency

• Fresh urine is typically transparent
• Cloudy urine can indicate pathological components, such as pus
• Horse urine is normally cloudy
• Urine can become cloudy during storage due to crystal formation and bacterial growth

Urine Smell

• Fresh urine with an ammonia smell can indicate pathology, such as cystitis, pyelitis, pyelonephritis, or urinary retention
• Fresh urine with an acetone smell can indicate hyperketonemia due to ketosis or diabetes
• Fresh urine with a putrid smell can indicate gangrenous processes in the urinary tract

Urine Density

• Hypersthenuria: increased urine density due to high salt concentration, with less impact from proteins
• Hyposthenuria: decreased urine density

Factors Affecting Vascular Resistance

• Blood viscosity: thicker blood increases resistance and decreases flow
• Blood vessel diameter: smaller diameters increase resistance and decrease flow
• Blood vessel length: longer vessels increase resistance and decrease flow
• Vascular wall properties: more elastic walls lower resistance, while more contractile walls increase resistance
• Total cross-sectional area: larger areas reduce resistance

Types of Resistance

• Elastic resistance: due to elasticity of large arteries, maintains continuous blood flow and reduces heart workload
• Peripheral resistance: in smaller arteries and arterioles, changes in diameter greatly impact blood flow
• Aging and vascular resistance: decreased elasticity with age increases resistance and affects continuous blood flow

Blood Flow

• Flow rate determined by pressure difference and resistance (Q = (P1 –P2) / R)
• Greater pressure drop and lower resistance result in higher blood flow velocity
• Blood flows in the direction of lowest pressure

Unconditioned and Conditioned Reflexes

Unconditioned Reflexes

• Innate adaptive responses, same among species
• Examples: suckling reflex in newborns, patellar (knee-jerk) reflex, startle reflex in humans, blinking reflex
• Stable adaptation reactions that persist throughout life
• Realized through any part of the CNS

Conditioned Reflexes

• Acquired adaptive responses during life
• Examples: salivating at the sound of a bell (Pavlov's dogs), fear of a specific sound after a traumatic event
• Labile responses that last only as long as the conditions exist
• Realized only through the highest parts of the CNS

Blood Composition and Functions

• Composed of plasma and cells (red blood cells, white blood cells, platelets)
• Functions:
  • Transport function (respiratory gases, biologically active compounds)
  • Ensuring metabolism (supplying nutrients, removing waste products)
  • Thermoregulatory function (transferring heat, equalizing temperature)
  • Maintaining homeostasis (regulating pH, temperature, solute concentration)
  • Protective function (antibodies, antitoxins, immune cells)

Saliva Composition and Functions

• Composed of water, enzymes, mucin, lysozyme, albumins, and urea
• Functions:
  • Dissolves food, helps determine taste, and facilitates swallowing
  • Rinses and cleans the mouth cavity
  • Begins to break down carbohydrates
  • Maintains pH in the forestomachs
  • Performs a protective function (lysozyme)

Saliva Regulation

• Caused by unconditioned and conditioned irritants
• True secretory nerves are parasympathetic, causing a rich secretion of watery saliva
• Sympathetic nerves cause weak secretion, resulting in thick saliva and dry mouth

Physiological Roles of Water in the Body

• Forms the major part of body fluids
• Acts as a solvent
• Acts as a medium for enzymatic reactions
• Thermoregulation
• Component of digestive juices
• Moisturizes air in the respiratory tract
• Moisturizes mucous membranes
• Acts as a lubricant for joints
• Acts as a shock absorber protecting organs

Fluid Compartments

• Extracellular fluid (ECF): outside of cells, 20% of the total amount of fluid in the body
• Intracellular fluid (ICF): inside cells, 40% of the total amount of fluid in the body
• Transcellular fluid (TCF): lies in serous cavities, low amount of fluid in the body, variable

Lipid Absorption and Transport

• Lipids broken down to fatty acids and glycerol by lipases
• Fatty acids absorbed with bile acids
• Formed into chylomicrons in the intestinal mucosa
• Chylomicrons absorbed into lymph and blood, and transported to liver
• In liver, used for synthesis of sterols (cholesterol, phosphatides) or oxidation

Nephron Loop Functions

• The nephron loop is responsible for producing concentrated urine found in the collecting ducts.
• The descending loop is highly permeable to water, but slightly permeable to sodium (Na) ions, leading to water reabsorption.
• The ascending loop is permeable to Na and Cl ions, but not to water, promoting the reabsorption of Na ions.
• The countercurrent mechanism in the nephron loop is an active process that maintains the concentration gradient in the renal medulla.
• If the countercurrent mechanism is "turned off," urine concentration will not occur, leading to kidney failure.

Neuro-Humoral Regulation of Kidneys

• Osmotic pressure regulation occurs through osmoreceptors and blood vessel volume receptors.
• Osmoreceptors respond to changes in blood osmotic pressure, increasing ADH and promoting water reabsorption in nephron tubules when osmotic pressure increases.
• Blood vessel volume receptors respond to changes in blood volume, increasing ADH and promoting water retention when blood volume increases.
• The nervous system regulates kidney function through the hypothalamus, which responds to changes in blood osmotic pressure and volume.

Nervous System Classification

• The nervous system is divided into two subdivisions: the central nervous system (CNS) and the peripheral nervous system (PNS).
• The CNS consists of the brain and spinal cord, while the PNS consists of nerves that connect to the CNS and internal organs.
• The PNS is further divided into the somatic nervous system, which innervates skeletal muscles, and the autonomic nervous system, which innervates internal organs and blood vessels.
• The autonomic nervous system is divided into sympathetic and parasympathetic systems, which have opposing effects on the body.

Neuron Classification

• Neurons can be classified into unipolar, bipolar, and multipolar neurons based on their shape.
• Unipolar neurons have one process that includes both an axon and a dendrite, and are exclusively sensory neurons.
• Bipolar neurons have two processes, an axon and a dendrite, and are mainly found in the olfactory epithelium and retina.
• Multipolar neurons have more than two processes, an axon, and two or more dendrites, and are the majority of CNS neurons.

Nerve Fiber Classification

• Nerve fibers can be classified by function, structure, and type of synapse and neurotransmitter.
• By function, nerve fibers can be classified into somatic, autonomic, secretory, sensory, motor, and interneurons.
• By structure, nerve fibers can be classified into myelinated or unmyelinated fibers.
• By type of synapse and neurotransmitter, nerve fibers can be classified into adrenergic, cholinergic, and peptidergic fibers.

Parathyroid Glands

• The parathyroid glands produce parathyroid hormone (PTH), which regulates blood calcium levels.
• PTH increases blood calcium levels by promoting calcium absorption in the gastrointestinal tract, reabsorption in the nephron tubules, and activation of osteoclast activity.
• PTH also regulates phosphorus levels and maintains an optimal calcium-to-phosphorus ratio in the body.
• The parathyroid glands are necessary for life, and their removal can lead to death due to severe calcium deficiency.

Blood Circulatory System

• The blood circulatory system is divided into the heart, arteries, capillaries, and veins.
• The heart functions as a pump, ensuring blood flow through the circulatory system.
• Arteries are resistance blood vessels that regulate blood flow, while capillaries are metabolic blood vessels where substances are exchanged between the blood and intercellular fluid.
• Veins are capacitance/volume blood vessels that regulate blood flow to the heart.
• Blood flow velocity changes throughout the circulatory system, with the highest velocity in large arteries and the lowest velocity in capillaries.
• Blood flow volume remains constant throughout the circulatory system, ensuring equal oxygen and nutrient delivery to all tissues.

Physiological Functions of the Skin

• The skin is an excretory organ, regulating sweat excretion through sweat glands
• The skin has several functions:
  • Mechanically protects the organism from the external environment
  • Distributes substances between the organism and the environment
  • Protects against UV radiation
  • Has bactericidal function
  • Participates in body thermoregulation
  • Has receptor function
• Exocrine glands, such as sebaceous and sweat glands, have ducts and secrete to the surface

Sweat Glands

• There are two types of sweat glands:
  • Atrichial (formerly Eccrine) sweat glands, found in the skin, function for thermoregulation and excretion
  • Epitrichial (formerly Apocrine) sweat glands, found in the armpits and around the anus, secrete oily substance and release pheromones
• Sweat glands have two structural parts:
  • Secretory part, consisting of spindle-shaped myoepithelial cells and two secretory cell types
  • Excretory part, consisting of cells that ensure the reabsorption of Na, K, and Cl from sweat into the blood

Hypothalamo-Hypophyseal System

• The hypothalamo-hypophyseal system consists of the hypothalamus and pituitary gland, which are closely interconnected
• The system has neural and humoral connections, with the hypothalamus secreting hormones that affect hormone synthesis in the pituitary
• The hypothalamus regulates the release of hormones from the pituitary, which in turn affects various endocrine organs throughout the body
• The hypothalamo-hypophyseal system regulates the following endocrine organs:
  • Anterior pituitary (Adenohypophysis)
  • Posterior pituitary (Neurohypophysis)
  • Thyroid gland
  • Adrenal cortex
  • Gonads (Ovaries and Testes)
  • Growth hormone

Blood Types and Rhesus Factor

• Blood types are determined by the presence or absence of antibodies (agglutinins) in the blood plasma and the presence or absence of inherited antigenic substances (agglutinogens) on the surface of red blood cells (RBCs)
• There are four blood groups: A, B, AB, and 0
• The Rhesus factor is an additional antigen on the surface of RBCs, with 85% of people having the Rhesus factor (Rh+) and 15% lacking it (Rh-)
• Determining the Rhesus factor is important, as Rh- individuals can synthesize anti-Rhesus antibodies if exposed to Rh+ blood

Digestion

• There are two types of digestion: intracellular and extracellular
• Intracellular digestion occurs in unicellular and lower multicellular organisms, where food is digested in a digestive vacuole
• Extracellular digestion occurs in highly developed animals, where digestion takes place in the cavities of the digestive tract
• There are two types of extracellular digestion: cavity digestion and membranal digestion
• Cavity digestion occurs in the stomach and intestines, where digestive juices are mixed with food
• Membranal digestion occurs in the small intestine, where enzymes are fixed on the microvilli and break down partially digested nutrients

Food Digestion in the Gastrointestinal Tract

• Mechanical digestion occurs through the motor function of the digestive tract, where food is crushed, dissolved, mixed with digestive juices, and moved forward
• Chemical digestion occurs through enzymes, which break down polymers into monomers
• Biological digestion occurs through microflora and microfauna, which break down organic matter
• The enteric nervous system (ENS) controls the digestive process, with two main plexuses: the myenteric (Auerbach's) plexus and the submucosal (Meissner's) plexus

Urine Formation

• Urine is formed from blood plasma through three basic physiologic processes: filtration, reabsorption, and secretion
• All parts of the nephron are involved in the formation of urine
• Neuro-humoral regulation of renal functions:
  • Filtration: regulated by neural way
  • Reabsorption: regulated by humoral way
  • Secretion: self-regulated

Filtration

• First process performed by the nephron: filtering the blood (glomerular filtration)
• Physical process where semipermeable biologic membrane filters out formed elements of blood and plasma proteins, allowing water, electrolytes, acids, and bases to enter the glomerular capsule
• Filtration intensity depends on blood pressure, oncotic pressure, and pressure in the nephron capsule

Reabsorption

• Occurs in the proximal tubule and nephron loop
• Both physical and physiological process: substances transported back to the blood from nephron tubules using energy (active process) and diffusion/osmosis (passive process)
• Substances reabsorbed: water (85%), electrolytes (sodium, chloride, potassium, sulfate, phosphate ions), bicarbonate ions, and nutrients (glucose, amino acids, organic substances)

Secretion

• Active physiological process: epithelial cells transfer substances from blood to urine for excretion
• Occurs along the tubule, with different substances secreted at different areas
• Helps maintain electrolyte and acid-base homeostasis

Countercurrent Mechanism

• Active process in the loops of Henle responsible for producing concentrated urine
• Water reabsorption occurs in the descending loop, increasing osmotic pressure and attracting Na ions
• Na ions are absorbed in the ascending loop, creating a high osmotic pressure and promoting water reabsorption

Urine Concentration

• No osmotic gradient between the filtrate and interstitial fluid in the cortical collecting duct, so no water is reabsorbed
• In the presence of ADH, concentrated medullary interstitial fluid creates a gradient for water reabsorption from the filtrate
• Deeper in the medulla, interstitial fluid is more concentrated, so water reabsorption continues from the medullary collecting duct
• Concentrated urine is produced when the filtrate reaches the end of the papillary duct

Reabsorption Threshold

• The concentration of a substance in the blood above which the kidneys begin to excrete it into the urine
• Threshold substances have a maximum amount that can be completely reabsorbed back into the bloodstream from the ultrafiltrate
• Examples: glucose
• Threshold-free substances are never reabsorbed back into the bloodstream, regardless of their concentration in the blood
• Examples: creatinine

Food Assessment in the Mouth Cavity

• Food intake, chewing, and swallowing occur in the mouth cavity, the beginning of the digestive tract.
• Food sorting and initiation of reflexes occur in the mouth cavity due to the presence of chemical, tactile, thermo, pain, and taste receptors.
• Reflexes initiated in the mouth cavity include motor reflexes (e.g., milk suckling, swallowing, chewing, spitting, motility of digestive tract) and secretory reflexes (e.g., salivary, gastric acid, pancreatic juices, bile secretion).

Physiological Roles of Calcium in the Body

• Calcium is the most abundant mineral in the animal body, present mainly in bone tissue (up to 99%) and teeth.
• Calcium is essential for:
  • Bone and cartilage formation
  • Blood clotting
  • Activating enzymes (e.g., pancreatic lipase, cholinesterase)
  • Muscle contractions
  • Transmission of nerve impulses
  • Reducing nervous system and muscle excitability
  • Nutrient absorption into cells
  • Vitamin B12 absorption
  • Enhancing phagocytic function of leukocytes
  • Increasing resistance to toxins and poisons
• Calcium deficiency can cause:
  • Increased muscle and nerve excitability
  • Cramps
  • Bone deformations (e.g., rickets, osteomalacia)
• Signs of calcium deficiency include:
  • Curved legs
  • Rachitis
  • Enlarged joints
  • Osteoporosis
  • Thin eggshells
  • Milk fever
• Calcium toxicity can interfere with mineral absorption, especially zinc.

Digestion Processes in the Stomach

• The stomach is a reservoir that holds food for 0.5-3 hours, allowing for chemical processing and incretory function.
• Gastric juice has a colorless, clear appearance, with a pH range of 1.0-2.5 in monogastric animals and 2.2-2.8 in ruminants.
• The main components of gastric juice are:
  • Enzymes (e.g., gastric proteases, pepsins)
  • Hydrochloric acid (HCl)
• Gastric juice properties and action:
  • Breaks down proteins into peptides and amino acids
  • Has a weak absorption function for drugs and alcohol

Regulation of Action of the Heart

• Heart rate and contractile force of the heart muscle are regulated by humoral mechanisms
• Humoral regulation involves biologically active substances, including:
  • Epinephrine (increases heart rate and contractile force)
  • Acetylcholine (decreases heart rate and contractile force)
  • Electrolytes (Ca²⁺ increases and K⁺ decreases contractile force)
  • Thyroxin (T4) and triiodothyronine (T3) (increase heart rate and contractile force)
• Autoregulatory mechanism involves intrinsic mechanisms within the heart, including:
  • Frank-Starling mechanism (regulates heart muscle contraction and relaxation)
  • Homeometric regulation (regulates contractile strength of cardiac muscle)
• Neural mechanism of regulation involves extrinsic mechanisms, including:
  • Parasympathetic nervous system (decreases heart rate and contractile force)
  • Sympathetic nervous system (increases heart rate and contractile force)

Regulation of Ca and P Levels in the Body

• Parathyroid glands produce parathyroid hormone (PTH), which regulates blood Ca levels
• PTH increases Ca levels in the blood by:
  • Promoting Ca absorption in the gut
  • Stimulating Ca release from bones
• Calcitonin (thyrocalcitonin) acts in the opposite way, lowering Ca levels in the blood
• Importance of Ca in the body:
  • Excitability of nerve cells
  • Muscle contraction and relaxation
  • Blood clotting

Motility of Forestomach and Rumination

• Forestomach motility is regulated by the nerve center in the medulla oblongata
• Parasympathetic nerves stimulate motility, while sympathetic nerves reduce it
• Forestomach contractions occur in two separate systems:
  • Rumen anteroom and reticulum contractions
  • Dorsal sac and ventral sac contractions
• Rumination (cud-chewing) involves regurgitation of incompletely chewed feed masses to re-chew and facilitate microbial fermentation
• Forestomach motility is promoted by receptor irritation in the forestomarchs and digestive tract

Metabolism and Excretion

• Metabolism is the sum of physical and chemical processes in an organism
• Excretion is the process of removing metabolic waste products from the body
• Excretion organs include:
  • Lungs (remove CO₂ and volatile substances)
  • Sweat glands (remove water, salts, and end products of protein metabolism)
  • Gastrointestinal tract (remove undigested parts of food, end products of digestive juices, and minerals)
• Liver transforms ammonia into urea, which is filtered from the blood by the kidneys and excreted in urine

Respiration

• Respiration is the process of exchanging gases between the body cells and the environment
• There are three types of respiration: internal, external, and cellular
• External respiration involves inhalation and exhalation of gases
• Internal respiration involves gas exchange between the blood and body cells
• Cellular respiration involves the conversion of food to energy
• Anatomic dead space refers to the airways that do not participate in gas exchange
• Functional dead space refers to alveoli that do not act in gas exchange due to collapse, obstruction, or other factors

Digestion Particularities in Horses, Pigs, and Birds

• Horses have a unique stomach anatomy, with a blind sac for bacterial fermentation and amylolysis
• Pigs have a large zone of cardiac glands in the stomach, where carbohydrate degradation and amylolytic processes occur
• Birds have a crop for maceration of food and digestion of carbohydrates, and a glandular stomach (proventriculus) and a muscular stomach (gizzard) for protein digestion

Thermoregulation

• Heat production occurs through muscle activity, liver function, and other organs

• Heat loss occurs through evaporation, convection, radiation, and conduction

• Temperature-sensitive receptors are localized in the CNS, skin, and internal organs

• The skin, liver, and muscles play important roles in thermoregulation### Oncotic Pressure and Blood Plasma Proteins

• Oncotic pressure, also known as colloid osmotic pressure, is a form of osmotic pressure exerted by proteins that pulls water into the circulatory system.

• Osmotic pressure is the minimum pressure needed to prevent the inward flow of water across a semipermeable membrane.

Functions of Blood Plasma Proteins

• Create oncotic pressure in the blood plasma, ensuring normal exchange of water and salts in the capillaries (e.g., mechanism of edema).
• Play a protective role, especially for globulins.
• Help maintain a relatively constant blood pH.
• Transport various substances in the blood (e.g., Fe, lipids, hormones, vitamins).
• Act as the only protein reserve in the body.

Blood Plasma Osmotic Pressure

• Is determined by the osmolar concentration of dissolved salts and ions in the blood plasma.
• Provides a pH level and irritability.
• Remains relatively constant and equal in intracellular and extracellular environments.
• Determines the flow of solvent through semipermeable membranes, keeping water in the extracellular fluid.
• Is maintained by the excretory organs (kidneys, sweat glands) and monitored by osmoreceptors.

Capillaries and Blood Plasma Proteins

• Capillaries are blood vessels where metabolic processes take place.
• Blood plasma proteins in capillaries are involved in filtration and reabsorption (attracting H2O), pH level regulation, and transport of substances.
• Blood colloid osmotic pressure is determined by blood plasma proteins (1/220) together with inorganic electrolytes, and its main function is to control blood plasma filtration and reabsorption processes in capillaries.