Human Physiology: Body Fluids and Homeostasis

• Human physiology is the study of the human body and its functions.
• The human body is an integrated system where all organs work together to maintain homeostasis.
• Homeostasis: the maintenance of a constant internal environment through the integrated functions of organ systems.
• The cardiovascular and respiratory systems work together to provide oxygen.
• Fluctuations in blood pressure are normal and meant to be within a certain range.
• Homeostasis is achieved through physiological processes mediated by body fluids.
• Total body water (TBW) refers to the total amount of water in the body, both inside and outside of cells.
• Water is located in two major compartments with a 2:1 ICF to ECF ratio.
• TBW totals approximately 42L of water.

Extracellular Fluid

• Extracellular fluid (ECF): water outside the cells.
• Plasma, or intravascular fluid, is approximately 3.5L.
• Interstitial Fluid is approximately 10.5L and is found between cells and tissues and outside of organ cells.

Intracellular Fluid

• Intracellular fluid (ICF): the water located inside the cells.
• ICF is approximately 28L.
• Interactions between different body parts occur through body fluids.
• Water intake is necessary to maintain TBW.
• Communication between organ systems allows the body to perform its functions.
• The body uses a complex communication system.
• Communication occurs through the TBW.
• Molecular movement between fluid compartments is required for bodily functions.
• Molecular oxygen moves from the mouth to the lungs to the plasma/ECF, then to the organ tissues and tissue cells. The plasma crosses the cell membrane to get to the ICF.
• Substances like oxygen, glucose, sodium, and potassium ions move between TBW compartments.
• Substances must cross both layers of the cell membrane to enter the cell.
• The cell membrane acts a selective barrier for substances.

Cell Membrane Structure

• The cell membrane regulates which substances enter and cross.
• Substances must pass through the cell membrane to go from the ECF to the ICF.
• The cell membrane is composed of a phospholipid bilayer made of fatty acid chains.
• Fatty acid chains are hydrophobic, neutral, and nonpolar.
• Phosphate groups are hydrophilic and polar.
• Nonpolar substances merge with fatty acids to pass through the membrane.
• Hydrophobic molecules easily cross the cell membrane due to the phospholipid bilayer.
• Oxygen is a hydrophobic, neutral molecule that can cross the cell membrane, moving from the ECF to the ICF.
• Polar and charged hydrophilic molecules do not easily cross the cell membrane.

Passive Transport

• Passive transport: movement across the cell membrane that doesn't require energy.
• Simple diffusion is a type of passive transport.
• During diffusion, molecules move from areas of high concentration to areas of low concentration until equilibrium is achieved.
• Equilibrium is reached when the concentration is equal in both areas. Diffusion is then complete.
• Diffusion is goal-oriented, where concentrations equalize.
• Diffusion is driven by the concentration gradient or the driving force.
• When one area has a higher concentration than another, diffusion will occur.
• Breathing in oxygen creates a concentration gradient between the lungs (high) and the blood (low); oxygen then diffuses from lungs to blood. Increasing oxygen levels also increases the concentration gradient. This will result in greater diffusion since it is based on the concentration gradient.
• Diffusion is an energy-independent and spontaneous process propelled by the concentration gradient.
• Proteins aren't needed to assist in diffusion.
• Oxygen is capable of simple diffusion and can cross by itself due to the gradient.

Facilitated Diffusion

• Requires assistance from a transport protein because the substance is unable to diffuse on its own.
• Facilitated diffusion is still affected by the concentration gradient, but something is interfering with its ability to cross, necessitating physical movement.
• Glucose, containing polar hydroxyl groups, is hydrophilic; it cannot cross the nonpolar fatty acid chains of the cell membrane.
• Glucose crosses the cell membrane through the cell membrane via transport proteins.
• Glucose is transported via transport proteins.
• Insulin, a protein molecule produced by the pancreas, responds to hyperglycemia.
• Insulin lowers blood glucose levels by enabling glucose uptake by cells, exiting the blood, and entering cells (ECF --> ICF), which allows it to aid in cellular respiration.
• If transport proteins are not available, they need to be inserted into the cell membrane for glucose to enter the cell.
• Insulin stimulates transport proteins specific to glucose insertion into the cell membrane, allowing uptake in the process of facilitated diffusion.
• Each molecule has its own specific transport proteins.

Active Transport

• Active processes require energy and a protein molecule.
• Involves movement from an area of low concentration to an area of high concentration.
• Maintains a gradient and doesn't reach equilibrium.
• Concentrates substances in one area.
• Opposes the concentration gradient, therefore requiring energy.

Ions

• Examples include sodium ions (Na+) and potassium ions (K+).
• Na+ exists in both ICF and ECF, but primarily in ECF.
• K+ exists in both ICF and ECF, but primarily in ICF.
• An imbalanced potassium/sodium concentration can be medically dangerous.
• Sodium ions are expected to diffuse out of the cell, Potassium ions are expected to diffuse into the cell.
• The diffusion of Na+ and K+ across the cell membrane: Na+ and K+ are polar, positively charged, hydrophilic particles; therefore incapable of diffusing through the fatty acid chains.
• Ions diffuse through ion channels (proteins).
• Ion channels and transport proteins are dissimilar in their respective energy input.
• Ion channels let ions get around the phospholipid bilayer of the cell membrane.
• Specific ion channels exist for each type of ion.
• Sodium ions travel in their designated ion channels to diffuse out of the cell.

Electrical Gradient

• There is more negative charge inside the cell (ICF) compared to the outside (ECF).
• Sodium ions diffuse into the cell due to its attraction to the negative charge, or electrical gradient, combined with the existing concentration gradient.
• The electrochemical gradient, which takes electrical and concentration gradients into account, drives sodium into the cell.
• Potassium's concentration gradient drives diffusion from outside to inside of the cell but it does not apply here.
• Active transport prevents diffusion, Every cell membrane has Na-K-ATPase Pumps that keep Na+ out of the cell and K+ in the cell.
• Na+-K+ ATPase Pump is the transport protein that pumps K+ into the cell and Na+ out.
• ATPase is an enzyme that breaks down ATP for the pump's energy.

Osmosis

• Osmosis is the movement of water from a hypotonic solution to a hypertonic solution in order to dilute the hypertonic area to equalize solute concentrations.
• Water can move across the cell membrane because its solutes (Na+ and K+ ions) cannot.
• Tonicity: the measurement of non-penetrating solute concentration, relative of one solution to another.
• Solute: the amount of solute in a volume of solvent
• Water moves from hypotonic solution to the hypertonic solution If a solute is unable to penetrate a selective barrier.
• Na+ is a non-penetrating ion in ECF, and K+ is in ICF.
• Solution B is hypertonic relative to A, and Solution A is hypotonic relative to B.
• Both ICF and ECF contain ions and nonpenetrating solutes; however, the cell membrane functions as a selective barrier.
• Hypertonic: more solute than solvent
• Hypotonic: more solvent than solute
• Isotonic: equal amounts

Hypernatremia

• Hypernatremia: an elevated concentration of sodium ions in the ECF (plasma) caused by dehydration (water loss).
• Dehydration is an imbalance between water loss and water intake.
• Hypernatremia occurs when water volume decreases but sodium stays the same, increasing Nat concentration. If plasma water is deficient, osmosis from the cells to the ECF occurs causing the cells may shrivel.
• Hypernatremia happens because there may be a water imbalance resulting from decreased water intake or heightened water loss (dehydration). There is normally a balance.
• If a brain cell loses water, abnormal functioning can result, producing lethargy, somnolence, coma, or death.

Nervous System

• Nervous system:
  • Central nervous system (CNS): brain and spinal cord.
  • Peripheral nervous system (PNS): nerves connecting to the CNS.
    • Afferent division: sensory neurons transmit info to the CNS.
    • Efferent division:
      • Somatic nervous system: transmits commands to skeletal muscle.
      • Autonomic nervous system:
        • Sympathetic branch.
        • Parasympathetic branch.
        • Transmits commands to cardiac and smooth muscle and various glands.
• Motor neurons/efferent neurons transmit information away from the CNS.
• Neurons are individual nerve cells that carry out the nervous system's basic functions.
• Basic neuron structure: cell body, dendrites, axon, and axon terminal.
• The two regions of a neuron: receptor zone and transmitting zone.
• Sensory signals provide information, whereas motor signals transmit commands.
• Signals travel from the receptor zone down the axon through the transmitting zone.

Action Potentials

• Occur in excitable tissues: nervous tissue and muscle tissue.
• The physiologic mechanisms by which signals are received and transmitted relies on a stimulus.
• The stimulus allows the receptor zone to receive a signal.
• Cell body and dendrites accept signals as a stimulus, leads to the receptor zone generating the action potential.
• The receptor zone allows action potentials to be sent in the transmission zone.
• Two phases of Action Potential; Depolarization and Repolarization phases.
• Inside of the cell becomes less negatively charged during the depolarization phase.
• An increase in open Na+ ion channels moderately, then it rapidly becomes positive Na+ ions diffuse into the cell, decreasing cell's negative charge = threshold depolarization.
• This event triggers an opening of much more additional Na+ ion channels.
• The cell becomes more positive, so there is a reversal of charge difference.

Resting Membrane Potential

• During, the inside of the cell is negative, and the outside is positive (Na+ and K+ gradient).
• Negatively charged molecules in the ICF (cytoplasm) become 'stuck'
• There are more K+ open ion channels than Na+ open ion channels.
• Channels can closed or opened.
• There is more positive charge lost out of the cell, then entering in; which leads to more diffusion of K+ out then Na in. Resultion: Cell looses more positive charge than its receiving.
• A Na+-K+ ATPase pump that transports three Na+ out and two K+ in.
• Removes three cations and restoring two cations.
• Electrical potential: different charge across the cell creates potential.
• Threshold: A minimum depolarization amount can overcome the threshold and concludes with depolarization.
• The stimulus causing sodium ion channels to open allows diffusion inward (electrochemical gradient) and triggers a larger amount of sodium ion channels to open with each stimulus.
• A stronger stimulus will not continue to increase the action potential.
• Action potentials occur very rapidly. Meaning the NS are Rapid depolarization and repolarization Resultion: Allows more AP to follow soon if stimulus is in place. Lastly Repolarization can be accomplished.
• A neuron can be stimulated again, but can not be while repolarization is occuring.
• Reestablishing the resting membrane potential (ICF negative and ECF positive) is the cause of repolarization, Closing and eventually opened K+ ion channels are involved and result in the cell is becoming negative again.

Action Spread

• The Na+ are restored to ECF and K+ are restored to ICF (correct positions).
• Occurs with Na+ K+ ATPase pump
• First receptor zone undergoes depolarization.
• Secondly the transmission zone experiences the action potential.
• The action potential happens on the axon starts out in cell body and dendrites.
• Lastly propogates down the axon and then each segments experiences it.
• Receptors trigger depolarization with neuron to trigger initial axon segment and another segment.
• While another next segment goes thru depolarization, the other segment starts its repolarization
• Myelin sheath that envelops nerve tissue has gaps- known as a node of ranvier.
• Axons have this myelination that are covered in the sheaths.
• It Deviods it of the sheath.
• The sheaths can not allow actipotential to be transmitted.
• Action potential generated at the initial segment of the axon and then at Node of Ranvier through Action potential that skips segments to nodes of ranvier which quickens this jumping transmission. Transmitted not continuously.
• This action= transmission is saltatory.
• Finally. Myelin increases speed as a result.

Multiple Sclerosis

• Demyelinating disease and the destruction of Myelin that's not curable/ gets worse that expresses itself with Muscular systems.
• This muscular system can be progressive, relapsing (Reocurrs and comes again).
• Abnormailuty that is most felt in the CNS slowing actipotential in axonal
• Almost an absent Actipotential because slow.
• Symptoms can be Muscle weakness, walking; or Urination/ Vision disturbance such as double vision. It is an Autoimmine. And the Efferent signals tells SNS to relax.
• Commmands are the transmitted signials!
• The one neuron the extends from spinal cord that gets transmitted to Skeletal msucles. Some are very extensive

SNS and the Somatic System

• Process to to command and transmit recieves; Step 1 Actipotential propagrates down the axon and the channels open the ion Channels.
• There are steps when these neurons in process that open Ion channels/ exocytosis that release neurotrans
• In SN where there are some steps to releases the axon terminas
• This action= transmission is saltatory. Finally. Myelin increases speed as a result. 1 acetylcholine that released from the terminal gets across the cell synapse and is received after 7 steps

Myashtenia Gravis

• Severe weakmesses that are invovled with CNS and damage to skeletal muscel cells (autoimmine0 with antiboies.
• Anti bodies attack receptors to damage those limted receptors. With cure: prevent action of achetylocholine by the cure acthetylcholinesterase.
• SNS is versus the ANS the skeletonus and SMOOOTH heart/cartiac musecls that is controlled
• Different with the control autotonic for free but hands of signal-2neurons vs sns single neurons .

Dual Innervation/Nervous System

• Dual innvervation has PNS collection and cell botidies with pre and prost.
• ANS does acetycholinesterase,
• SNS/Sympethatic starts with presymethatic upto PNS AND RELEASES NEUROTRANS for the neuron to reciev with ADRENERGIC REceptrors is NE that gets REUPCAKE MEchnaizMS .
• NE is TYROSINE withkidneys

Autonomic Nervous System

• Has the adrenal Grand that releases the gland hormone that can be epipen also uses has dual invveraations-and syathemptic/psysyntethicthat contorl and infulencae organ.
• Energt using uses para branch/ energy using processs is sympatheti and the best way is to acivate and dcativte .

The Body's Response to Breathing

• When running away, the sym controls heart increasing! But psym will dominate too control the decrsaing rate. Not Opposing each other but workint with the rest.
• Adregenic receptors! S/B. A1 present in cartiat structures and vascular smooth muscel that constict vessels. So in result causes not much blood.
• Ne is no the epinephrine.
• B! are candiac muscel. Lastly B2present the smooth.
• Ex smooth muscles will airway with lungs. The sa,e cant contract, and the receoptors are responsible to do tha AnaphyalxicShock triggered by droppiness Blood prressue is lost a lot. Must Reverse constrict to make The body can make constriction that will flow and build if the body can not do. Bronchoconstriction is caused by the mechanism is also lost. Epienph causes increase and the cause flows ot vitals S/B IN sMOOTH MUSCES IS 2 RECEPTOR> ne CANT DO airway/ne CANT INcrease BP BUt EPYNN CANT

Beta-2 and cardio

• Beta 2 is inliver and gyco!
• glycogen
• cardio

Explore the principles of human physiology with a focus on body fluids and homeostasis. Learn how the body maintains a stable internal environment through the coordinated functions of organ systems. Understand the distribution of water within intracellular and extracellular fluid compartments.