INB365S Exam 1 Review

0.9% saline/normal saline (NS)

• isosmotic (300 mOsM NP)

• isotonic (300 mOsM NP)

• fixes hemorrhage

5% dextrose in 0.9% saline/D5-normal saline (D5NS)

• hyperosmotic (300 mOsM NP + ~300 mOsM PP)

  • technically 278 mOsM PP

• isotonic (300 mOsM NP)

5% dextrose in water/D5W

• isosmotic (300 mOsM PP)

• hypotonic (dextrose is PP)

0.45% saline/half-normal saline (1/2NS)

• hypoosmotic (150 mOsM NP)

• hypotonic (150 mOsM NP)

• fixes dehydration (hydrates cells but keeps some fluid in the plasma)

5% dextrose in 0.45% saline/D5-half-normal saline (D5 1/2NS)

• hyperosmotic (150 mOsM NP + ~300 mOsM PP)

  • technically 278 mOsM PP

• hypotonic (150 mOsM NP + dextrose is PP)

Cell membrane functions

• physical isolation

• regulation of exchange with the environment

• communication between the cell and the environment

• structural support

what can diffuse across the membrane without help?

• small hydrophobic/lipophilic molecules (O2, CO2, N2)

• small uncharged polar molecules (urea, water (slowly))

• cholesterol-based molecules (lipophilic) (steroid hormones)

types of peripheral proteins

• structural

• enzyme

types of integral proteins

• structural

• transporters

• enzymes

• receptors

simple diffusion

• movement of a molecule directly across the lipid bilayer

• passive transport - no outside energy source required (uses energy from gradients)

• molecules move down a concentration gradient (high → low)

• rate increases with increased temperature

• rate decreases with increased molecular size and distance from the initial site

• stops at equilibrium (uncharged molecules)

Fick’s law of diffusion across membranes

channels

• integral membrane transport protein

• continuous, water-filled pore

• strictly facilitate passive transport

• transport smaller molecules and ions

• rapid transport rate

• can be open channels (pores) or gated channels

  • ligand-gated, mechanically gated, and voltage-gated

carriers

• integral membrane transport protein

• never form an open channel (must undergo a conformational change)

• facilitate both passive and active transport

• transport larger, polar organic molecules

• slower transport rate

  • has specificity, competition, and saturation

• can be uniporters (one solute) or cotransporters

  • symporters (same direction)

  • antiporters (opposite directions)

how are carriers similar to enzymes?

• catalyze transport processes

• have specific substrates (specificity)

• undergo conformational change

• affected by temperature, pH, etc.

• subject to competition and saturation

• have allosteric sites

• have an active site where substrate binds

which substance is also transported by a carrier?

a competitor

what characteristic of mediated transport is illustrated by the 2nd graph?

specificity (the presence of molecule Y has absolutely no effect on the transport of molecule X)

what is the adaptive significance (benefit) or specificity in physiology?

can manage what goes in and out of the cell

what is the term for a substance that inhibits transport of another substance, but is not actually transported?

competitive inhibitor

for a single carrier, saturation of transport depends on ____. for a whole cell or tissue, saturation depends on ____

substrate concentration; substrate concentration and the number/density of carrier proteins present

can a substrate outcompete a competitive inhibitor?

yes

can a substrate outcompete a noncompetitive inhibitor

no

where are the higher concentrations of ions in the ICF and ECF?

• ICF: K+, A-

• ECF: Na+, Cl-, Ca2+

primary active transport

uses ATP to go against the concentration gradient

secondary active transport

uses the gradient established by a primary active transporter + uses the kinetic energy of a molecule going down its concentration gradient

which carriers use primary active transport?

• uniport

• antiport

which carriers use secondary active transport?

• antiport

• symport

what is not categorized as a “means/mode/method” of movement?

symporter, uniport, antiport (must describe the energy used)

which way is secretion?

ECF/basolateral → lumen/apical

which way is absorption?

lumen/apical → ECF/basolateral

what is the formula for concentration?

C = S/V

osmosis

water moves from low solute concentration to high solute concentration (dilutes)

what are the common penetrating, non-penetrating, and partially penetrating solutes?

• P: urea

• NP: ions

• PP: glucose

osmolarity vs molarity

• osmolarity takes into consideration the dissolution of the solute in solution

• ex: 1 M NaCl is 2 OsM

osmolarity vs tonicity

• osmolarity: compares any 2 solutions (even a cell)

  • describes a solution’s concentration compared to another

  • mechanism of equilibrium: diffusion

  • nature of solutes does not matter

• tonicity: describes a solution compared to a cell

  • describes how that solution will affect the behavior of the cell - whether the solution will cause water to move out of the cell or not

  • mechanism of equilibrium: osmosis

  • only NP solutes matter

total body water

• 60% of body weight (in kg)

• ICF = 67% of TBW

• ECF = 33% of TBW

  • interstitial fluid = 25% of TBW/75% of ECF

  • plasma = 8% of TBW/25% of ECF

markers of body compartments (indicator substances of volume)

• deuterium oxide (D2O) - TBW

• inulin - ECF

• Evan’s blue - plasma

physiological reference man values

• weight: 155lb or 70kg

• TBW: 42L (60% of weight)

• plasma osmolarity: 300 mOsM

• volumes of distribution: 28L ICF; 14L ECF

dehydration

• lose hypoosmotic solution (mostly water) → increase solute concentration in ECF and ICF

• fix with a hypotonic solution (causes cell to swell and restore water lost)

• all solutes lost come from ECF

hemorrhage

• lose isosmotic solution only from ECF → same solute concentration as before

• fix with isotonic solution (restore plasma volume)

assumptions for RBC problems

• cell contents are NP

• water moves to dilute

• water moves faster than solutes

• the solute and volume of the external solution are infinite compared to the solute and volume of the cell

• only the relative concentration of NP is important

osmolarity initial cell response

• hyperosmotic = cell will shrink

• isosmotic = cell will not change

• hypoosmotic = cell will swell

tonicity ultimate cell response

• hypertonic = cell will shrink

• isotonic = no net change in cell

• hypotonic = cell will swell

  • is NP outside = 0, cell will burst/hemolyze

what are the isotonic IV solutions?

• normal saline

• D5-normal saline

what are the hypotonic IV solutions?

• D5W

• 1/2-normal saline

• D5-1/2-normal saline

which IV solution do you use to correct dehydration?

hypoosmotic and hypotonic solution (1/2-normal saline)

which IV solutions do you use to correct hemorrhage?

• normal saline (isosmotic and isotonic)

• D5-normal saline

what is a potential side effect of D5-1/2-normal saline?

cellular edema (IV solution is hypotonic, which causes water to move into cells)

why should you not give free water to collect for dehydration?

water is hypotonic with an NP = 0, so the RBCs hemolyze and can kill the patient

types of local cell-cell communication

• gap junctions - direct cytoplasmic connects between adjacent cells

• juxtracrine (contact-dependent signals) - require interaction between membrane molecules on 2 cells

• autocrine signals - act on the same cell that secreted them

• paracrine signals - secreted by one cell and diffused to adjacent cells

types of long cell-cell communication

• endocrine system - hormones are secreted by endocrine glands/cells into the blood. only target cells with receptor for the hormone respond to the signal

• nervous system:

  • neurotransmitters - chemicals secreted by neurons that diffuse across a small gap to the target cell

  • neurohormones - chemicals released by neurons into the blood for action at distant targets

intracellular receptors

• cytosolic or nuclear

• bind steroid or thyroid hormones

• act as transcription factors

cell membrane receptors

• integral membrane proteins

• bind peptide hormones and other lipophobic signals

• usually activate a secondary messenger

homeostasis

• maintain bodily functions within specific livable ranges, adjusting to internal and external changes

• requires physiological control systems

  • a sensor/detector → an integrating center/controller → an output signal and target

• uses negative feedback loops

why is a transporter exporting more of a molecule in response to increased concentration not a homeostatic response?

• it is driven by mass action kinetics, not reflex control

• there is no dedicated sensory and control system

• there is no negative feedback loop or set point regulation

local control systems

• paracrines

• restricted to the tissue/cell involved

• ex: low oxygen in the tissue = dilate blood vessel

reflex/systemic/long control systems

• cells at a distant site control the response

• response loops

• feed-forward

• feedback loops

  • negative feedback

  • positive feedback

what are the 3 components of a control system (local or long)

• a sensor/detector → an integrating center/controller → an output signal and target

response loop

• stimulus → sensor → input signal → controller → output signal → target → response

• ex: knee jerk reflex

feedback loops

• regulates the response loop

• the response becomes the stimulus

• response loop + feedback

• negative feedback loop - inhibits the response (homeostasis!)

• positive feedback loop - upregulates the response (not homeostasis)

feed forward loop

• anticipates change

• response loop + no stimulus

• not homeostasis

neural response loop

• separate sensor and controller (CNS)

• output signal - motor efferent neurons

endocrine response loop

• sensor and controller are the same (endocrine gland)

• output signal - hormone

simple endocrine reflex general components

• stimulus

• receptor - endocrine cell/gland

• afferent path

• integrating center - endocrine cell/gland

• efferent path - hormone

• effector - cell with receptor

• response - tissue response, systemic response

insulin release pathway

• stimulus - increased plasma glucose

• receptor - pancreatic beta cell

• afferent path

• integrating center - pancreatic beta cell

• efferent path - insulin

• effector - adipose and muscles cells

• response - decreased plasma glucose

simple neural reflex general components

• stimulus

• receptor - cell ending, whole cell, multicellular

• afferent path - afferent/sensory neuron

• integrating center - brain and/or spinal cord (CNS)

• efferent path - efferent motor neuron

  • somatic motor neurons

  • autonomic motor neurons

• effector

  • somatic: skeletal muscles

  • autonomic: smooth muscle, cardiac cells, glands

• response

  • somatic: contraction

  • autonomic: heart range, blood pressure, etc.

knee jerk pathway

• stimulus - striking patellar ligament

• receptor - mechanoreceptor

• afferent path - sensory/afferent neuron

• integrating center - spinal cord

• efferent path - somatic motor neuron

• effector - skeletal muscle

• response - muscle contraction

the efferent in the baroreceptor reflex in response to high BP is ______

parasympathetic

hormones

• hormone - substance released into the blood stream to target a distant cell/organ

• neurohormone - hormone released from a neuron

• trophic hormone - hormone that targets another endocrine gland

• trophic neurohormone - hormone released from a neuron that targets another endocrine gland

3 major classes of hormones

• amine - synthesized from either tyrosine or tryptophan

  • catecholamines (norepinephrine) (behave like peptides) and thyroid hormones (tetraiodothyronine) (behave like steroids)

• steroid - made from cholesterol

  • adrenal cortex and gonads (aldosterone)

  • -sterone

  • bound to carrier proteins in plasma

  • can act as transcription factors

• peptide - synthesized by linking amino acids

  • most hormones (secretin, CRH)

  • dissolved in plasma

anterior pituitary

• endocrine gland that receives trophic hormones from the hypothalamus

• connected to the hypothalamus via a portal system

posterior pituitary

• stores neurohormones from the hypothalamus (derived from neural tissue)

• has a neural connection to the hypothalamus

what are the left labels of the image?

• hypothalamic hormones

• anterior pituitary hormones

• endocrine targets and the hormones they secrete

• nonendocrine targets

long loop negative feedback

• occurs when endocrine gland hormones are high and inhibit the anterior pituitary and hypothalamus

• the primary and most influential regulatory mechanism controlling the overall pathway

short loop negative feedback

occurs when anterior pituitary hormones are high and inhibit the hypothalamus

where do primary, secondary, and tertiary pathologies integrate?

• primary - endocrine gland

• secondary - anterior pituitary

• tertiary - hypothalamus

synergism

• effect of 2 or more hormones on the same parameter is greater than additive

• 1 + 1 > 2

• ex: in stressful situations, cortisol, epinephrine, and glucagon cause plasma glucose to skyrocket

permissiveness

• one hormone is needed for another to exert its full effect

• first hormone has no direct effect on the parameter

• 1 + 1 = 1 (or 2 + 0 > 2)

• ex: in development, thyroid hormone is necessary for normal growth

• ex: thyroid hormone increases epinephrine receptors on cell surfaces

antagonism

• hormones have opposing effects

• 1 + 1 = 0

• ex: ADH increases blood volume and BP; ANP causes Na+ and water excretion

• ex: hormone A breaks down bone; hormone B builds bone

mechanisms of hormone interactions

• separate pathways

  • e.g. antagonism; insulin increases glucose uptake by muscle and adipose while glucagon increases gluconeogenesis by the liver

• crosstalk between secondary messenger pathways

  • parallel actions - increasing Na+ vs increasing Ca2+

  • convergent actions - phosphorylating the same protein

  • antagonistic actions - one upregulates, one downregulates cAMP

• regulate synthesis or release of hormone or receptor

  • permissiveness