Physiology Unit 1 PDF

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Homeostasis = same condition, not a static state Variables under homeostatic control: o Environmental factors affecting cells - Osmolarity - pH - temperature o Materials for cell needs - Nutrients - Water - Na+, Ca+, ions - Oxygen - Secretions Pathophysiology = how the body functions in a disease state o Example: increase blood glucose NEGATIVE FEEDBACK  glucose molecules enter beta cells in pancreas  beta cells secrete insulin  insulin binds to receptors on tissue/organ  tissue cells take in more glucose to make glycogen o Example: decreased glucose  alpha cells in pancreas release glucagon hormone  glucagon binds to receptors on tissue/organ cells  tissue cells break down glycogen to make glucose Extracellular fluid maintains normal functions Law of mass balance = balanced sodium load Total substance = (intake + production) – (excretion + metabolism) urine, feces, sweat, CO2

Changing/ secreting stuff

Mass flow (x/min) = (X concentration) x (volume flow) (X / volume)

(volume / minutes)

Clearance = volume of blood cleared of x over time Blood = ECF (plasma) + heavy blood cells Steady state (net movement between compartments) ≠ Equilibrium (identical compartments) Disequilibrium occurs when: 1) increase in Na+ or Cl- in ECF 2) increase in K+ in ICF

Control Systems  Input stimulus  Integrating center that initiates response  Output signal response Local Control = restricted to one tissue o Example: decrease in oxygen in tissue  chemical signaling  nearby muscles in blood vessel wall told to relax  vessels widen  increased blood to tissue Long Distance/Systemic Control 1) Response Loop ≈ local control  Stimulus  Sensor  Integrating center  Output signal  Target response 2) Feedback loop = response of target modulates input portion of pathway a. Negative feedback = response opposes or removes the stimulus signal – can cause a return to normal state but cannot prevent the disturbance (example is shivering in response to cold) b. Positive feedback = response reinforces stimulus so outside factors are need to shut off system (example is baby pushing against cervix send signal to mom’s brain to release more oxytocin which contracts the uterus more until baby is born) Sensitivity matters because blood concentration can be ±3% but O2 can be ±40% Feed Forward Control = predicts a change is about to occur and starts a response loop for it o Example: salivation by only seeing or smelling food which causes increased acidity in the stomach Set/Normal Point Changes Biorhythms affected by set point changes 1. Circadian rhythm involves body temperature and plasma cortisol levels: temperature is low in early morning and high in afternoon, cortisol is low while sleeping and highest during awakening 2. Environmental conditions: acclimatization (natural occurrence) or acclimation (artificially done in a lab), northerners go south for winter and are wearing shorts while local southerners are cold

Compartments Anatomical compartments: 1) cranial 2) thoracic - pleural sac - pericardial sac 3) abdominopelvic - abdominal cavity - pelvic cavity Functional compartments:

1) ECF - blood plasma - interstitial fluid 2) cells

Hollow organ = lungs, heart, blood vessels, intestines Lumen = inside of a hollow organ filled with air or fluid Membranes More metabolically active membranes need more proteins Membranes are made of: Cholesterol phospholipid carbs “glycol” protein |lipid bilayer| |glycolipid| |glycoprotein| selective barrier structure, immune signaling, recognition Cholesterol in the membrane helps to maintain shape when it is stretched or contracted Phospholipid has a polar head and non polar tail

Membrane proteins: 1) Integral proteins = bound strongly by lipids, transmembrane, can be removed by disrupting force 2) Peripheral proteins = non covalent interactions that can be removed chemically by enzymes or binding

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Tissues Differentiation = process of transforming an unspecialized cell into a specialized cell Cell junctions are created by cell adhesion molecules (proteins) Junctions: 1) Gap = communicating = cell to cell communication 2) Tight = occluding = blocks movement between cells 3) Anchoring = holds cells together Proteins: 1) Cadherins = cell to cell involving Ca2+ 2) Integrins = cell matrix junctions involving signaling 3) Immunoglobulins = nerve to cell in nervous system 4) Selectins = temporary cell to cell Epithelial Connective = blood (mobile) AND = support tissues/organs, cartilage, bone (fixed) Connective tissue provides provide support/barrier Scattered cells secrete and modify matrix Extracelular matrix (ECM) = mixture of proteins, polysaccharides, and minerals = ground substance made of proteoglycans (heavily glycosylated proteins) - Blast = build up matrix - Clast – break down matrix Matrix fibers: 1) Collagen = flexible and inelastic 2) Elastin = coiled and elastic 3) Fibrillin = thin and straight 4) Fibronectin = connects and adheres for healing Types of connective tissue: Tissue Function Loose Small gland support Dense Strength and flexibility Bone/cartilage Support Adipose Adipocytes Blood Watery ECF Neural

Location Under the skin Tendons (muscle to bone), ligaments (bone to bone) Cartilage (no blood supply), bone (minerals) White (1 enormouse lipid droplet), brown (many droplets) Plasma

Neuron = specialized cell of nervous system initiates, integrates, and conducts electrical signals to other cells; sometimes over long distances Glial = support Nerve = cellular extensions of many neurons packaged with connective tissue (carries signals from many neurons between nervous system and other parts of body Signals carried by nerves: - initiate new electrical signal - stimulate gland cell to secrete substances - stimulate muscle cell to contract Muscle

MUSCLE AND NEURAL are excitable tissues - Minimal ECM - Lamina for support - Gap junctions

Produces force and movement 1) Skeletal a. attached to skin (facial muscles) b. attach to bones (produce limb + trunk movement) c. contract under voluntary control 2) Cardiac: a. only found in heart b. cause heart to contract and pump blood into circulation c. involuntary control 3) Smooth a. surround tubes of body (blood vesses + gi tract tubes) b. their contraction ↓diameter or shortens tube length i. contraction helps “squeeze” good down esophagus to stomach c. involuntary control Epithelial = covers a surface to protect, transport, absorb, secrete, excrete, sensory reception - avascular (diffusion of nuterients) - basal lamina under rest - little intracellular space Classification 1) simple = single layer a. Cuboidal: cube-shaped b. Columnar: elongated c. Squamous: flattened d. Ciliated: cells that line inner surface of trachea to propel mucus →mouth 2) stratified = multi layer but labeled by top layer

Epithelium = epithelial tissue that may form any type of epithelial cell located at surfaces that cover body or organs; line inner surfaces of tubes and hollow structures, and rest on basement membrane Basement membrane = extracellular protein layer anchors epithelial tissue Tight junctions enable epithelia to form boundaries b/w body compartments + function as selective barriers regulating molecule exchange - basal side is anchored to basement membrane – transport glucose out of cell into surrounding - apical side is top edge, facing lumen (interior) - in kidney tubules: transport solutes like sugar glucose from tubule lumen into epithelial cell (tight junction prevents glucose backflow Examples o nose = pseudostratified ciliated columnar o throat = stratified squamous o lungs = simple squamous o liver = simple cuboidal o intestine = simple columnar o anus = stratified columnar o bladder = transitional…can stretch Tissue Remodel Necrosis = cell death by trauma, toxen or decreased O2 Apoptosis = cell suicide – cell moves away from neighbors, chromatin shrink, breaks apart so others can eat up their parts Differentiation leves 1) totipotent = earliest cells that can become anything 2) pleuripotent = after day 4, can become many things but not just anything  specific tissue 3) multipotent = undifferentiated cells that can still decide = stem cells (less specialized cells that create new cells for a specialization) In a lab setting, you can revert specialized cell back to their pleuripotent form = “induced pleuripotent” Organs Organs are made up of 2+ of the 4 tissue types and arranged in sheets, tubes, layers, bundles, strips Examples: o Kidney: small tubes of simple epithelium o Blood vessels: walls contain smooth and connective tissue o Neuron extensions: epithelial and muscle cells o Protective capsule around Kidney: loose network of connective tissue Functional unit = subunit of organ performing function of organ (like a nephron of a kidney)

Diffusion Rate of diffusion = (available surface area) x (concentration gradient) (Fick’s law) (resistance of membrane) x (thickness) Lipid soluble and small molecules go through membrane easiest Passive transport

Simple diffusion Facilitated diffusion

Active Transport

Primary = uniport and antiport = exchanges ions using energy like the Na+K+ pump

Vesicular

Secondary = symport = organic substrate moves into the cell with ion Phagocytosis

a. Integral membrane proteins help facilitate diffusion like channels (gated)  Voltage gated  Ligand gated  Mechanically gated  Temperature gated  Light sensitive b. Carrier proteins undergo conformational change to carry ions  Protein binds and moves through  Protein spans whole membrane and just conforms c. Gap junction channels = series of proteins making channels with adjacent cells (ions may get more diluted as they pass) Na+ inside the cell enter enzyme  ATP phosphorylates enzyme to make it pump out the Na+  2 K+ enter the enzyme from outside  Unphosphorylated enzyme lets K+ into the cell 3+ out and 2+ in always helps make interior more negative so that the cell can do work like a battery Organic substrate needs this because it is flowing against its concentration gradient      

Ligand molecule binds to surface at clathrin pit Clathrin coated pit invaginates Vesicle is formed Vesicle fuses with vacuole that sheds clathrin Fused complex undergoes further processing Clathrin and receptor moleculres are recycled to membrane

Endocytosis Epithelial diffusion: Paracellular transport = transfer through intercellular compartment Transcellular transport = transfer through cell membrane Transcytosis = types of transcellular used on macromolecules Diffusion = 1) passive 2) Molecules move down concentration gradient 3) Molecules move until equilibrium 4) Slow over long distances (time ~ distance2) 5) Directly related to temperature 6) Inversely related to weight and size 7) Happens in open or across compartments

Excitable Tissues Resting membrane potentials are a characteristic of all cells in the body. The difference in charges between inside and outside of the cell exists in equilibrium chemically but, as long as ions continue to move, there is actually resting membrane disequilibrium – to have a resting potential, ECF must be positively charged Na+/K+ pump is powered by ATP: 3 Na+ go out and 2 K+ go in (against their gradient) K+ leak channels allow some K+ out K+ movement is integral to determining resting membrane potential Chemically: ions move down their concentration gradient except with the pump which goes against the concentration gradient Electrically: in the Na+/K+ pump, the inside of the cell is becoming more negative so the electrical gradient opposes the chemical gradient g = conductance = ease with which ion flows through a channel gK >> gNa In neurons, Na+ is mostly outside the cell and K+ is mostly inside the cell with protein anions Cell membrane is less permeable than capillary membrane where ions flow freely Action potential = disturbance of resting membrane potential  At resting potential (negative mV), disturbance causes temporary depolarization (move towards neutrality) – depolarization represent a change in membrane conductance so some ions have “g” changes  repolarization  hyperpolarization when it becomes more negative than resting Connective Tissue Cells that can form tissue are divided into: 1) Parenchymal o goblet cells secreting mucous 2) Supporting o Blood, bone, lymph o Proper = cells + ECM (fibers, ground substance) Immigrant cells migrate through connective tissue like blood Resident cells - Macrophage = euchromatic nucleus with inclusions (ingesting material) - Mast cell = vesicles containing vasoactive substances like heparin and histamine - Fibroblast = make collagen and ECM to support epithelial cells  Most common types are I, ii, iii, iv

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Made of small subunits that are bound together thickly (collage fibrils that form tendons) or thinly (elastic fibers that can also come in fenestrated sheets)

Ground substance surrounds and supports fibers and is mostly made of fibronectin (very common) and laminin (major component of basal lamina) Classifications of connective tissue: 1) Loose = few fibers in ECM – found under the skin “areolar” 2) Dense = many fibers in ECM (but few cells and ground substance) a. Dense irregular = all directions (example: mammary gland) b. Dense regular = support in one direction (example: tendons)

Action potentials are generated and propagated if threshold is reached More intense stimulus means action potentials generated at higher frequency Higher frequencies means more neurotransmitter released Excitatory synapse: chemical neurotransmitter bind to receptors causing ion channels to open, resulting in depolarization towards threshold for an action potential in the axon This is graded in amplitude (Depending on the amount of neurotransmitter and the number of channels that open) In the axon, amplitude of the potential is coded as the frequency of action potentials. Ca2+ ions control axon terminal synaptic releases – at the target, neurotransmitter binds to receptor proteins, causes membrane channels to open or close and causes a change in membrane potential Mg2+ competes with Ca2+ and blocks calcium channels in the axon terminal

K+ ions control resting membrane potential Na+ ions controlled by voltage gated channels in conduction of nerve impulses Graded potentials

Action potentials

can be depolarizing or hyperpolarizing

always lead to depolarization of membrane and reversal of the membrane potential

Amplitude is proportional to the strength of the stimulus.

Amplitude is all-or-none; strength of the stimulus is coded in the frequency of all-or-none action potentials generated.

Amplitude is generally small (a few mV to tens of

Large amplitude of ~100 mV.

mV). Duration of graded potentials may be a few milliseconds to seconds.

Action potential duration is relatively short; 3-5 ms.

Ion channels responsible for graded potentials may be ligand-gated (extracellular ligands such as neurotransmitters), mechanosensitive, or temperature sensitive channels, or may be channels that are gated by cytoplasmic signaling molecules.

Voltage-gated Na+ and voltage-gated K+ channels are responsible for the neuronal action potential.

The ions involved are usually Na+, K+, or Cl−.

The ions involved are Na+ and K+ (for neuronal action potentials).

No refractory period is associated with graded potentials.

Absolute and relative refractory periods are important aspects of action potentials.

Graded potentials can be summed over time (temporal summation) and across space (spatial summation).

Summation is not possible with action potentials (due to the all-or-none nature, and the presence of refractory periods).

Graded potentials travel by passive spread (electrotonic spread) to neighboring membrane regions.

Action potential propagation to neighboring membrane regions is characterized by regeneration of a new action potential at every point along the way.

Amplitude diminishes as graded potentials travel away from the initial site (decremental).

Amplitude does not diminish as action potentials propagate along neuronal projections (nondecremental).

Graded potentials are brought about by external stimuli (in sensory neurons) or by neurotransmitters released in synapses, where they cause graded potentials in the post-synaptic cell.

Action potentials are triggered by membrane depolarization to threshold. Graded potentials are responsible for the initial membrane depolarization to threshold.

In principle, graded potentials can occur in any region of the cell plasma membrane, however, in neurons, graded potentials occur in specialized Occur in plasma membrane regions where voltageregions of synaptic contact with other cells (postgated Na+ and K+channels are highly concentrated. synaptic plasma membrane in dendrites or soma), or membrane regions involved in receiving sensory stimuli.

Nerve Fibers FIBER Thickness Conduction velocity Myelination Diameter

A Thickest (fastest) 4-120 m/sec myelinated 1.5-20 micron

B Medium 3-15 m/sec Myelinated 1.5-3.5 microns

C Thinnest (slowest) 0.5-4 m/sec 0.1-2 microns

Examples

skeletomotor fibers, fusimotor fibers and afferent fibers to skin.

preganglionic autonomic efferents

postganglionic autonomic efferents and afferent fibers to skin...