Physiology exam prep 1

Blood Plasma Composition

• Blood plasma makes up about 60% of the whole blood
• It is a straw-colored liquid consisting of: • Organic substances (electrolytes, nutrients, proteins, hormones, etc.) • Inorganic substances (electrolytes, salts, etc.) • Dissolved blood gases
• Plasma proteins (7%): • Albumins (~59%): main protein reserve, create colloid osmotic (oncotic) pressure, regulate water exchange, and act as carrier proteins • Globulins (~30%): diverse group of proteins, divided into three groups (α, β, and γ), act as carrier proteins and antibodies • Fibrinogen (3 g/L): plasma protein involved in blood clotting
• Other components: • Nutrients (amino acids, lipids, glucose) • Vitamins, microelements (trace elements) • Metabolic end products (urea, lactic acid, creatinine, bilirubin, CO2, etc.)

Protein Functions in Blood Plasma

• Functions of blood plasma proteins: • Supply of nutrients for the body's plastic and energetic processes • Transport of many substances (bilirubin, fats acids, exogenous substances, including drugs) • Creation of colloid osmotic (oncotic) pressure in the blood plasma • Protective role, especially for globulins • Help to maintain relatively constant blood pH • Plasma proteins transport various substances in the blood • Take part in blood coagulation – fibrinogen

Colloid Osmotic (Oncotic) Blood Pressure

• Created by proteins in the blood plasma
• About 80% results from the albumin fraction, 20% from the globulin, and a tiny amount from the fibrinogen
• Oncotic blood pressure affects: • In capillaries: filtration decreases and reabsorption of H2O increases • pH level: acts as a buffer • Transport: Fe, lipids, hormones, vitamins, etc. • Protective function: immunity, blood clotting factors, etc.

Muscle Contraction

• Muscle cells (fibers) consist of: • Sarcolemma: muscle fiber cell membrane • Sarcoplasm: muscle fiber cytoplasm • Sarcoplasmic Reticulum: smooth endoplasmic reticulum (SER) in the muscle fiber • Transverse Tubules: formed by invaginations of the sarcolemma • Myofibril: bundle of thread-like contractile elements consisting of myofilaments
• Myofilaments: • Thick filaments (myosin): 16nm, during muscle contraction, the myosin heads link the thick and thin filaments together • Thin filaments (actin): 8nm, provide active sites where myosin heads attach during contraction • Elastic filaments (titin): connect myosin to the Z discs • Non-elastic filaments (nebulin): an actin-binding protein, determines the length of thin filaments
• Sliding Filament Theory: actin and myosin filaments within the sarcomeres of muscle fibers bind to create cross-bridges and slide past one another, creating a contraction

Homeostasis

• Definition: the relative constancy of an organism's structure, genetics, and internal environment, and the mechanisms that maintain it
• Types of homeostatic regulation: • Thermoregulation: maintaining the core body temperature • Chemical regulation: balancing the concentration of chemicals like glucose, calcium, acid-base balance, etc. • Osmoregulation: maintaining a constant osmotic pressure inside the body by balancing the concentration of fluids and salts

Urinary System and Homeostasis

• The kidneys perform the following functions: • Filter the blood by removing metabolic wastes • Regulate blood solute concentration (osmolarity) • Assist in the long-term regulation of blood pH • Directly influence systemic blood pressure through their control of blood volume
• The urinary system maintains fluid homeostasis in the body, regulates blood pressure, controls red blood cell production, and maintains proper pH of the blood

Synapses

• Definition: a junction between a nerve and a muscle or two nerves where impulses are transmitted by the help of a neurotransmitter
• Types of synapses: • Electrical synapses: transmit impulses through channels in the presynaptic and postsynaptic membrane, use sodium ions to transmit an electrical signal • Chemical synapses: transmit impulses through the release of neurotransmitters, types: axodendritic, axosomatic, axoaxonic, dendrodendritic, and dendrosomatic

pH Changes in the Digestive System

• In the mouth, the pH is slightly acidic to neutral (pH 6.5-7.5) due to the presence of saliva and enzymes like amylase, which initiate the breakdown of carbohydrates.
• In the stomach, the pH is very acidic (pH 1.5-3.5) due to the secretion of hydrochloric acid (HCl), which denatures proteins, activates pepsinogen, and kills pathogens.
• In the small intestine, the pH is slightly acidic to slightly alkaline (pH 6-7.4) due to the neutralization of acidic chyme by bicarbonate ions secreted by the pancreas, allowing for the proper functioning of digestive enzymes.

Mechanism of pH Maintenance in the Forestomachs of Ruminants

• In ruminants (e.g., cows, sheep, and goats), the forestomachs (rumen, reticulum, and omasum) have specific mechanisms to maintain an optimal pH for microbial fermentation.
• The rumen has an optimal pH range of 6.2-7.2, maintained through buffering agents in saliva, absorption of volatile fatty acids (VFAs), and regular motility.
• Reticulum and omasum have similar buffering and mixing mechanisms to maintain a stable pH.

Inhibition Processes in the Nervous System

• Inhibition is a reversible change in the excitability of a nerve cell, decreasing its functional activity.
• Types of inhibition: presynaptic (indirect) and postsynaptic (direct), by localization; and hyperpolarization (and strong depolarization), by the nature of the process.
• Presynaptic inhibition occurs when an inhibitory synaptic knob releases a neurotransmitter that inhibits the release of an excitatory neurotransmitter.
• Postsynaptic inhibition occurs when an inhibitory neurotransmitter connects with a postsynaptic receptor, causing hyperpolarization (inhibitory postsynaptic potential, or IPSP).

Stages of Gas Exchange in the Body

• Stage I: External Respiration or Lung Ventilation: the process of breathing (inhalation and exhalation), which occurs in the respiratory organs, including the nose, pharynx, larynx, trachea, bronchi, and bronchioles.
• Stage II: Gas Exchange and Transport: the exchange of oxygen and carbon dioxide between the lungs and bloodstream.
• Stage III: Internal or Tissue Respiration: the exchange of oxygen and carbon dioxide between the bloodstream and body cells.

Physiological Maturity

• Depends on animal species, breed, feeding and housing conditions, heredity, and animal sex
• Occurs before breeding maturity
• Females: follicles develop in ovaries, eggs mature, and first estrus cycle starts
• Males: spermatozoa form in testicles, mature in epididymis, and are discharged during sexual arousal
• Breeding maturity: body has matured, reached ≈ 70-80% of adult body weight

Functions of Water in the Body

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

Selectively Permeable Biological Membrane

• Determines the unequal distribution of ions inside and outside the cell
• Selectively receives substances important for life support and plasticity
• Permeability depends on substance size, solubility, charge, and molecular properties

Humoral Regulation of Water and Salt Metabolism

• Antidiuretic hormone (vasopressin) from neurohypophysis: intensifies water reabsorption from nephron tubules
• Aldosterone from adrenal gland cortex: intensifies Na reabsorption from nephron tubules
• Epinephrine (adrenalin) from adrenal gland medulla: narrows blood vessels of nephron tubules

Biological Effects of Testosterone

• Produced in and secreted from Leydig cells outside seminiferous tubules
• Increases muscle mass, bone mass, and sex drive
• Develops male secondary sex characteristics
• Influences behavioral effects, such as aggression and territorial marking

Link between Respiratory and Cardiovascular Systems

• Respiratory system influences venous return to the heart (respiratory pump)
• Pulmonary circulation: all blood leaving the right ventricle must pass through the lungs
• Both systems participate in the regulation of acid-base balance
• The renin-angiotensin-aldosterone system involves the respiratory system in blood pressure regulation

Liver Functions

• Bile production and fat absorption
• Excretory function (cholesterol, bilirubin) and detoxification
• Participates in blood clotting, hematopoiesis, and thermoregulation
• Synthesizes hormone precursors and inactivates hormones
• Participates in carbohydrate, protein, and lipid metabolism

Characteristics of Myocardium

• Works continuously
• Automaticity: can depolarize spontaneously without external stimulus
• Different parts of the conduction system have varying self-excitation abilities (gradient of automaticity)
  • Sinuatrial node: 70-80 imp/min
  • Atrioventricular node: 40-60 imp/min
  • Purkinje fibers: 15-30 imp/min
• Muscle fibers are short, branched, and bound to meshwork
• All myocardial cells have the same excitability
• Not under voluntary control

Properties of Cardiac Muscle

• Conductivity: able to conduct excitation
• Contractility: able to contract, with force depending on blood supply and distension
• Excitability: able to respond to stimuli, changing with phases of the cardiac cycle

Cardiac Cycle Phases

• Absolute Refractory Period (ARP): unable to respond to stimuli during systole and 1/3 of diastole
• Effective Refractory Period (ERP): ARP plus short segment of phase 3
• Relative Refractory Period (RRP): middle of diastole, myocardium relaxes and responds to strong stimuli
• Supernormal Phase (SNP): end of diastole, excitability increases, and weaker stimuli can trigger an action potential

Action Potential Phases

• Phase 0: Depolarization, rapid Na+ influx
• Phase 1: Early repolarization, K+ efflux
• Phase 2: Plateau phase, Ca2+ influx balanced by K+ efflux
• Phase 3: Repolarization, Ca2+ channels close, and K+ channels remain open
• Phase 4: Resting phase, K+ channels keep transmembrane potential stable

Digestion

• Mechanical food processing: crushing, dissolving, mixing with digestive juices, and movement through the digestive tract
• Chemical food processing: enzymes break down polymers into monomers
  • Proteases: proteins to amino acids
  • Lipases: fats to glycerin and fatty acids
  • Amylases: carbohydrates to monosaccharides
• Biological food processing: microflora and microfauna break down cellulose, carbohydrates, and nitrogen compounds

Insulin and Glucagon

• Insulin: lowers glucose level in blood, produced by β cells in pancreas
  • Actions:
    • Stimulates glycogen production in skeletal muscles
    • Activates lipoprotein lipase in adipose tissues
    • Activates hexokinase, glycogen synthesis, and glucose to fatty acid transformation in liver cells
• Glucagon: raises glucose level in blood, produced by α cells in pancreas
  • Actions:
    • Stimulates glycogenolysis and gluconeogenesis in liver
    • Increases glucose release from liver
    • Acts on adipose tissue cells to provide substrate for gluconeogenesis

Smooth Muscle

• Not under voluntary control
• Two types:
  • Visceral (single-unit) smooth muscle:
    • Found in hollow and tubular organs
    • Can respond to humoral irritants
    • Rhythmicity and gap junctions allow for coordinated contraction
  • Multi-unit smooth muscle:
    • Found in irises, lungs, hair follicles, and large arteries
    • Does not react to humoral irritants
    • Each fiber requires its own electrical impulse

Glucocorticoids

• Short-term effects: similar to the sympathetic nervous system
  • Increases heart rate, dilates pupils, boosts metabolism, and more
• Long-term effects:
  • Alarm stage: sympathoadrenal system activates, producing epinephrine and ACTH
  • Resistance stage: body resists harmful factors
  • Exhaustion stage: body's ability to produce ACTH and glucocorticoids is depleted, leading to illness

Thirst

• A sensation of dryness in the mouth and throat associated with a desire for liquids
• Regulation mechanism:
  • Central thirst center in the hypothalamus
  • Stimulation by increased osmoconcentration and angiotensin II
  • Neural and humoral regulation of water and salt metabolism

Skeletal Muscle Functions

• Ensuring movements (dynamic and static)
• Control of body posture
• Support
• Heat production
• Defense function

Transport of CO2

• CO2 is transported in three forms: dissolved CO2, bicarbonate ions, and carbaminohemoglobin
• CO2 combines with Hb to form carbaminohemoglobin
• Carbonic acid dissociates into hydrogen ions and bicarbonate ions
• Bicarbonate ions diffuse out of RBCs and chloride ions diffuse in (chloride shift)
• Hydrogen ions combine with Hb, promoting O2 release

Digestive Tract Functions

• 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: receptors in the digestive tract induce various functions

Action Potential

• Action potential is a reversible change in polarization of the cell membrane
• Stages of action potential:
  • Depolarization: rapid rise in membrane potential, opening of Na+ channels
  • Repolarization: decrease in membrane potential, closing of Na+ channels
  • Hyperpolarization: change in potential that makes the membrane more polarized
• Absolute refractory period: period of time when the cell is incapable of repeating an action
• Relative refractory period: period of time when the cell is partially capable of repeating an action

Growth Hormone (GH)

• GH, also known as somatotropin, promotes growth, metabolism, and bodily development
• Physiological roles of GH:
  • Promoting growth in children and adolescents
  • Regulating metabolism
  • Promoting tissue repair and regeneration
  • Maintaining organ function and size
  • Modulating the immune system
  • Potential anti-aging effects

Carbohydrate Metabolism

• Meaning of carbohydrates:
  • Energy source
  • Cell component (glycoproteins)
  • Needed for muscle contractions and relaxation
  • Needed for the action of the myocardium and nervous system
• Liver's role in carbohydrate metabolism:
  • Processes most of the glucose
  • Stores glycogen
  • Converts glucose to lipids
• Glycogen:
  • Polysaccharide stored in the liver and muscles
  • Synthesized from glucose, glycerin, fatty acids, amino acids, and volatile fatty acids
  • Benefits of storing glucose as glycogen: large molecule, insoluble, compact, and easily broken down

Carbohydrate Metabolism in Ruminants

• Herbivores convert most carbohydrates to volatile fatty acids (VFAs) in the forestomachs
• Ruminants use VFAs as an energy source; blood glucose is used in lower amounts
• Glucose is mainly broken down to VFAs, which are absorbed through the forestomach walls
• The level of glucose in the blood is lower in ruminants compared to other animals and humans

Inspiration

• Normal inspiration occurs by contraction of the respiratory muscles
• Diaphragm contractions decrease pressure in the pleural cavity, causing the lungs to expand
• Air is sucked into the lungs until the pressure in the lungs and external environment becomes equal
• Self-regulation of inspiration:
  • Stretch receptors in the lungs do not send impulses to the respiratory center
  • Inspiratory neurons are activated, sending impulses to the spinal cord and respiratory muscles

Osmotic Pressure

• Osmotic pressure is the pressure that develops due to a concentration gradient of dissolved salts across a biological membrane
• Physiological roles of osmotic pressure:
  • Maintaining cell volume
  • Regulating fluid balance
  • Kidney function and urine concentration
  • Nutrient and waste exchange
  • Gastrointestinal absorption
  • Production of bodily fluids
  • Maintenance of blood pressure

Cardiac Cycle

• Changes in pressure in the heart chambers and nearby blood vessels during the cardiac cycle:
  • Ventricular systole: highest pressure in the left ventricle and aorta
  • Total diastole: pressure drops sharply in the left ventricle, but remains high in the aorta
  • Right side pressure pump: reaches a maximum of 25 mm Hg in the right ventricle and pulmonary artery

Muscle Fatigue

• Muscle fatigue is a temporary decrease in muscle work capacity that disappears during rest.
• It is indicated by a decrease in the amplitude of muscle contraction.
• In the nerve/muscle preparation, the nerve gets tired first due to the depletion of resources (neurotransmitter, energy, etc.).
• Muscle fatigue occurs only in the 2nd stage, due to the decrease of energy resources (ATP) in the muscle, accumulation of metabolic end products (lactic acid, etc.), and changes in the distribution of ions in the cell.
• A muscle can stop contracting when it runs out of ATP and becomes fatigued.

Anaerobic Glycolysis

• It is a chemical process that renews ATP from glycogen (glucose) in an anaerobic way (without oxygen).
• This energy system produces 2 molecules of ATP and 2 molecules of pyruvic acid, which can be used in aerobic respiration or converted to lactic acid.
• Lactic acid is generated in muscles, causing fatigue and soreness, especially during strenuous exercise when oxygen cannot be sufficiently delivered to muscle.

Estrogen

• Estrogen hormones stimulate the growth and development of female gonads, genital organs, and female-specific secondary sex characteristics.
• They promote the proliferation of the uterine mucosa, thickening, and gland development.
• Estrogens have an important role in the estrus cycle and inhibit the development of atherosclerosis in blood vessels.
• They stimulate the growth and development of mammary glands, especially during puberty, pregnancy, and lactation.
• Estrogen prepares genitalia for copulation and transportation of spermatozoa, creates favorable conditions for fetal development, and triggers the onset of parturition.

Physiological Effects of Estrogen

• Estrogen stimulates follicular growth, participates in the regulation of LH and FSH release, and initiates sexual receptivity.
• It prepares the genitalia for copulation and transportation of spermatozoa, and creates favorable conditions for fetal development.
• Estrogen contributes to the growth and development of mammary glands and triggers the onset of parturition.
• It promotes the development of secondary sex characteristics, including skeletal features, body hair, and voice.