Exam #1: 2015 Flashcards
______ is the only neurotransmitter that is utilized at the neuromus-cular junction.
ACh is the only neurotransmitter that is utilized at the neuromuscular junction.
What elicits an action potential in a skeletal muscle fiber?
Depolarization of the motor end-plate (NO AP AT THE ACTUAL END-PLATE)
What is Intracellular Fluid (ICF)? What fraction of tbw is it?
Water within the cells. 2/3 TBW.
What is extracellular fluid? What fraction of TBW is it?
Water outside of cells. 1/3 TBW.
What is interstitial fluid, where is it found, and what forces create it? What fraction of TBW?
The fluid that actually bathes the cells. It is an ultrafiltrate of plasma (no proteins b/c they can’t cross capillary wall). It is created by the hydrostatic of the capillaries.
It is 3/4 of ECF and, thus, it is 1/4 of TBW
What is plasma, where is it found, and what forces create it? What fraction of TBW?
Plasma is the fluid circulating in blood vessels created by osmotic pressure. It is 1/4 of the ECF and, thus, 1/12 of TBW
Moles represent what?
The NUMBER of PARTICLES.
Osmoles represent what?
The number of particles into which a solute dissociates in solution.
Three moles of CaCl2 = ____ Osmoles?
9 osmoles, b/c 1 moles of CaCl2 = 3 osmoles (1 Ca + 2 Cl)
What is osmolarity?
The concentration of particles in solution expressed as OSMOLES per LITER (or other unit volume, e.g. Milliosmoles = osmoles per milliliter).
If a solute dissociates into more than one particle in solution, then its osmolarity equals…
The molarity (i.e. amount per volume —mol/L, mmol/L, etc.) X the number of particles in solution (its # of osmoles).
What is the osmolarity of a solution containing 6 mmol/L of CaCl2?
18 mOsm/L, because CaCl2 dissociates into three particles.
What is the distribution of TBW in men and women?
Men = 60% Women = 50%
What are the three typical ways AMOUNTS of a solute are expressed and what do they mean?
- Moles: Number of MOLECULES.
- Equivalents: The amount of charged (ionized) solute; the # of moles of solute X its valence (e.g. 1 mole of CaCl2 = 2 Eq of calcium, and 2 Eq of Cl).
- Osmoles: Number of particles in solution.
A CaCl2 concentration of 6 mmol/L corresponds to ____ mEq/L?
24 mEq/L
Define the principle of electroneutrality. How does membrane potential affect this?
Each bodily fluid compartment must have the same concentration (in mEq/L) of cations and anions. There can be no more cations than anions, or vice versa.
Membrane potential does not affect the BULK solution, because the separation of charges occurs only in the small area directly adjacent to the cell membrane. This small separation of charges is not enough to appreciably change the overall concentrations.
Given the difference in individual solute concentrations between the ICF and ECF, what keeps the total solute concentration (osmolarity) the same?
Water flowing freely across the membranes. Any transient differences in osmolarity are quickly dissipated by water movement.
What are the three most notable individual solute concentration differences between the ECF and ICF?
K+, Na+, and Ca2+ (!!!!!!)
ECF: K+ = 4, Na+ = 140, Ca2+ = 2.5
ICF: K+ = 120, Na+ = 14, Ca2+ = 0.0001 (!!!!!!)
What is the relative difference in pH between ECF and ICF?
ICF (pH 7.1) is slightly more acidic than ECF (pH 7.4)
- Define partition coefficient (K) and give equation.
- Describe what increases/decreases ‘K’
- Describe the partition coefficient for polar vs nonpolar molecules.
-The partition coefficient, by definition, describes the solubility of a solute in oil relative to its solubility in water.
K = (concentration in olive oil)/(concentration in water) –
- The greater the relative solubility in oil, the higher the partition coefficient and the more easily the solute can dissolve in the cell membrane’s lipid bilayer.
- Nonpolar solutes tend to be soluble in oil and have high values for partition coefficient, whereas polar solutes tend to be insoluble in oil and have low values for partition coefficient.
- Define diffusion coefficient, give its equation and define the terms.
- What does diffusion coefficient correlate with?
-Describes how readily a molecule will diffuse across a membrane — D= KT/6πrη, where: D = Diffusion coefficient, T = absolute temperature (Kelvin), r = molecular radius, and n = viscosity of medium. K is Bolztmann’s constant.
- Correlations are apparent in the formula.
p. 7
To calculate osmolarity, it is necessary to know the _____ of solute, and whether ________.
- concentration
- the solute dissociates in solution.
p. 12
Give the equation for osmolarity and define the variables
Osmolarity = g C – where: Osmolarity = Concentration of particles (mOsm/L) g = Number of particles per mole in solution (Osm/mol) C = Concentration (mmol/L)
Give the definition of osmolality
The concentration of osmotically active particles, expressed as osmoles (or milliosmoles) PER KG of water (as opposed to osmolarity, which is PER LITER).
For a given solution,osmolarityis slightly less than osmolality, why?
Because the total solvent weight (thedivisorused for osmolality) excludes the weight of any solutes, whereas the total solution volume (used for osmolarity) includes solute content.
-see osmoLality in L4
The pressure required to stop the flow of water in an osmotic solution is…
the osmotic pressure of Solution 1.
Give the formula for osmotic pressure (van’t Hoff’s law) and define variables.
π = g C σ RT Where... • π = osmotic pressure • g = # of particles in solution • C = concentration • σ = Reflection coefficient p.13
What is a reflection coefficient, RC?
It describes the ease with which a solute crosses a membrane.
(#12, p.13)
- ) What does it mean if RC = 1? Give examples.
2. ) What does it mean if RC = 0? Give examples.
- ) It means that the membrane is impermeable to solutes, however, the water still comes.
- Since 100% of the solutes stay on one side, the solutes are exerting 100% pull on the water.
- Thus, 100% osmotic pressure/100% pull/100% osmotic pressure retained.
e. g. Albumin in blood, intracellular proteins, Dextran (a carbohydrate used to increase blood volume). - ) There is 100% permeability. Thus, the solute achieves equilibrium across the membrane and exerts NO PULL.
- No osmotic draw.
- e.g. Urea, free water.
What creates hydrostatic pressure in a U-shaped tube open to the atmosphere?
Because of the unequal solute concentrations, fluid will move to the side with the higher solute concentration (right side of tube), against the GRAVITATIONAL FORCE (hydrostatic pressure) that opposes it, until the hydrostatic pressure generated is equal to the osmotic pressure.
p.7 Netter
Give the Nernst equation and how it relates to equilibrium potential.
Ex = (60/z) log10([X]o/[X]i)
- where, Ex = equilibrium potential of ion ‘x’ (in mV), z = the valence of the ion, [X]o = ECF concentration, and [X]i = ICF concentration.
- The equilibrium potential in inversely proportional to the valence of the ion (which is usually either 1 or 2), and the sign and magnitude of the potential is determined by the relative concentration of the ion in the ECF and ICF.
- The sign of the Vm is in reference to the inside of the cell.
Resting membrane potential (Vm) is dependent upon a ____ gradient in the _____.
K+ gradient in the extracellular fluid (ECF).
p.46 Lipp
In the SNS, _____ is released from presynaptic terminals of the motoneurons and activates ______ receptors on the _____ of skeletal muscle.
Ach
nicotinic receptors
MEPs
All preganglionic neurons of the ANS release _____.
Postganglionic ANS neurons release either _____ or _____.
Preganglionic = ACh Postganglionic = ACh or norepinephrine
Adrenergic neurons release _____, their receptors are called ______.
Norepinephrine
Adrenoreceptors
- What is the one target within the SNS that uses ACh at the postsynaptic neuron?
- What type of sympathetic cholinergic receptors are these?
- Sweat glands
2. MUSCARINIC cholinoreceptors
Preganglionic neurons of the SNS are always ______, and they release _____ which interacts with ______ receptors on the cells of postganglionic neurons.
Cholinergic
release ACh
nicotinic receptors
p.49 Cos
Postganglionic neurons of the SNS are _____ in all of the effector organs EXCEPT in the _____, where they are ______.
Adrenergic
except in the sweat glands where they are CHOLINERGIC.
ALL preganglionic neurons are _____ i.e. they release _____.
Cholinergic, i.e. they release ACh.
Parasympathetic postganglionic neurons are mostly ______.
Cholinergic.
Sympathetic postganglionic neurons are mostly _____, except for ______, which use ______ as a neurotransmitter.
Mostly ADRENERGIC.
Except sweat glands, which use ACh as an NT.
When ACh is used in the postganglionic ANS, the receptor is ________.
Muscarinic (sudomotor, i.e. sweat glands).
Sympathetic dilates and dries, except _____ and _____.
Except sweating and ejaculation.
Give three characteristics of ALL presynaptic nerves of the SNS
- All are short.
- All release ACh.
- All activate nicotinic receptors.
In the PSNS, ACh receptors are _____ at the ganglia, and _____ at the effector organ.
Nicotinic at ganglia
Muscarinic at effector organs
What are the non-cholineric NTs of the PSNS?
Vasoactive intestinal peptide (VIP) Nitric oxide (NO)
Which organs have ONLY sympathetic innervation (6)?
Sweat glands, vascular smooth muscle, pilomotor muscles of the skin, liver, adipose tissue, and kidney.
What types of functions are β1 receptors are involved in? Give four examples,
Metabolic functions: Such as gluconeogenesis, lipolysis, renin secretion, and in all functions in the heart.
p.56 Cos
In general, what do β2 receptors cause? -e.g. ______ in three things.
They cause relaxation of smooth muscle in bronchioles, wall of the bladder, and wall of the gastrointestinal tract.
p.53
In tissues with sympathetic cholinergic innervation, the receptors are _______.
Muscarinic
Adrenoreceptors are found in ______ of the ______ nervous system and are activated by ________.
- Target tissues
- sympathetic
- the catecholamines norepinephrine and epinephrine.
p. 58 Cos
α1 Receptors are found in…5 places
- vascular smooth muscle of the skin
- skeletal muscle
- (splanchnic region for 3-5) the sphincters of the GI tract
- the sphincters of the bladder
- the radial muscle of the iris.
p. 58
Norepinephrine is a catecholamine released from _____________ nerve fibers, while epinephrine is a catecholamine released from _______.
- postganglionic sympathetic adrenergic nerve fibers
- the adrenal medulla
p. 61 Cos
Muscarinic receptors are found in all ______ organs of the _______ division and in a few ______ of the ______ division.
p.62 Cos
- all effector organs of the parasympathetic division.
- effector organs of the sympathetic division.
Nicotinic receptors are found on all ________ of _______, and on the _____ cells of the adrenal medulla.
- postganglionic neurons
- both sympathetic and parasympathetic nervous systems
- chromaffin cells
p. 61
Describe the effects of hexamethonium on both the motor end plates and autonomic ganglia.
- ) MEP: Does not block receptor.
- ) Ganglia: Blocks receptor.
p. 61
Give the mechanisms for the following taste buds:
- ) Bitter and Sweet
- ) Sour
- ) Salty
- ) Bitter and Sweet: Inositol Triphosphate (IP3), Ca2+
- ) Sour: Acid (H+) closes K+ channels.
- ) Salty: Salt (Na+) directly depolarized the receptor.
- ) Give the cranial nerve innervation for the tongue/taste buds.
- ) What course do they travel?
1.) 7th CN: Anterior 2/3’s of tongue. Sweet and salty.
9th/10th CN: Bitter and the posterior tongue.
- ) CNs VII, IX, and X:
- Ascend in solitary tract.
- Terminate in the solitary nucleus of medulla.
- Nerves travel to thalamus.
What do type 1A afferent nerves innervate and what do they detect?
Type 1A: Innervate central region of both the nuclear bag fibers and the nuclear chain fibers.
-Senses velocity of change in length of spindle fibers.
What do type 2 afferent nerves innervate and what do they detect?
Type 2: Primarily innervate nuclear chain fibers.
Detects the length of spindle fibers.
ANS effector neurons communicate with their target cells via ________ receptors and, thus, may have an array of consequences.
G protein–coupled
Most postganglionic parasympathetic neurons are ______.
cholinergic
In the parasympathetic division, effector organs have only ________ receptors.
muscarinic receptors
in tissues with sympathetic cholinergic innervation, there are _______ receptors.
muscarinic receptors (sweat glands)
The β1 receptors are involved in _______ functions such as _______ (4).
- metabolic functions
- gluconeogenesis, lipolysis, renin secretion, and in all functions in the heart.
The β1 receptors are involved in metabolic functions such as _______ (4).
-gluconeogenesis, lipolysis, renin secretion, and in all functions in the heart.
α2 Receptors are ______, are located both ______ and ______.
- inhibitory
- presynaptically and postsynaptically
α2 receptors are found on ______ and ______ nerve terminals and in the _______.
- presynaptic adrenergic and cholinergic nerve terminals
- gastrointestinal tract
α2 receptors present on sympathetic postganglionic nerve terminals are called _______. What is their function?
- autoreceptors
- to conserve norepinephrine in states of high stimulation of the sympathetic nervous system by inhibiting further release of NE from the same terminal.
α2 Receptors present on ________ are called heteroreceptors.
What is their function?
- parasympathetic postganglionic nerve terminals of the gastrointestinal tract
- Norepinephrine is released from sympathetic postganglionic fibers that synapse on these parasympathetic postganglionic fibers. When activated by norepinephrine, the α2 receptors cause inhibition of release of acetylcholine from the parasympathetic postganglionic nerve terminals.
Why is it possible for the adrenal medulla to become depleted of catecholamines during periods of prolonged stress?
The adrenal medulla does not have α2 receptors and, therefore, is not subject to feed-back inhibition.
What are the G-protein enzymes and their second messengers? (2)
Adenylyl cyclase and phospholipase C, which, when activated, generate a second messenger (cyclic adenosine monophosphate [cAMP] or IP3, respectively).
Vascular smooth muscle has only ______ innervation, which causes _______.
- sympathetic
- vasoconstriction
Which actions have ONLY parasympathetic innervation and what is the effect(s) of stimulation?
Gastric acid secretion (increases), Pancreatic secretion (increases), lacrimal glands (secretion).
Which actions have ONLY parasympathetic innervation (3) and what are the effects of stimulation?
- Gastric acid secretion (increases)
- Pancreatic secretion (increases)
- Lacrimal glands (secretion).
Describe the SNS effects of alpha-1 and beta-2 stimulation on the vasculature.
Alpha-1: Constriction of vessels to skin, splanchnics, resting muscle, and kidney.
Beta-2: Dilates exercising muscle.
Best initial therapy for ER patient with lightheadedness, hypotension, and bradycardia?
Atropine, ACh inhibitor (M/PSNS inhibitor). Increases SNS innervation.
Patient with ventricular fibrillation does not respond to two attempts at defibrillation; best initial therapy?
Epinephrine; constricts cutaneous blood vessels to shunt blood to heart –Skin is largest organ in the body.
What type of drug will help with trouble urinating?
Alpha-adrenergic antagonist; opens the internal urinary sphincter.
What medication for an unresponsive bladder (difficulty urinating due to this)?
Acetylcholine for the bladder
What treatment for urinary urge incontinence?
Anticholinergic
What is an effective anticholinergic to prevent salivation, lacrimation, urination, and defecation?
Atropine
ACh receptors are ____ at ganglia, and _____ at effector organs.
Nicotinic at ganglia, muscarinic at effector organs.
What are the levels of PSNS innervation?
Craniosacral –CNs 3, 7, 9, and 10.
Sacral: S2-S4
What are the paired actions of alpha and beta stimulation (2)?
- ) Relaxation of smooth muscle walls of GI tract (beta-2 and alpha-2).
- ) Stimulation of glycogenolysis and gluconeogenesis in the liver (beta-2, and alpha).
Higher concentrations of catecholamines are necessary to activate _____ receptors than to activate ______ receptors.
Higher concentrations of catecholamines are necessary to activate ALPHA-1 receptors than to activate BETA receptors.
What are the non-cholinergic PSNS NTs? (2)
- ) Vasoactive intestinal peptide (VIP)
2. ) Nitric oxide (NO)
Name two alpha-2 agonists
CLONODINE and METHYLDOPA are ALPHA-2 AGONISTS
Name an alpha-1 agonist that opens the bladder
Tamsulosin
Name an alpha-1 antagonist that opens the bladder
Tamsulosin
Which organs have ONLY sympathetic innervation? (6)
Sweat glands, vascular smooth muscle, pilomotor muscles of the skin, liver, adipose tissue, and kidney.
Explain the role of cortisol in catecholamine formation. What is the consequence of a pheochromocytoma?
How to treat pheochromocytoma?
- Cortisol is needed, in conjunction with PNMT, to convert NE to epinephrine.
- In the case of a pheochromocytoma, it secretes mainly NE. if the tumor is too far from the adrenal cortex to receive cortisol required by PMNT, it will only secrete NE.
- Alpha and beta blockers.
Explain the SNS effects on salivary secretions
Less salivary secretions than PSNS, but more than no innervation: Low volume, high viscosity salivation.
Explain the SNS effects on salivary secretions
Less salivary secretions than PSNS, but more than no innervation.
• SNS = Low volume, high viscosity, high amylase salivation.
What is unitary smooth muscle and where would you find it? (4)
Capable of sustained and powerful contractions. Has gap junctions between cells which allow fast spread of electrical activity (coordinated contraction). Because of this, many smooth muscle cells act as a single unit. Present in GI tract, bladder, uterus, and ureter.
What is the cause of IBS?
Abnormal pacemaker function of smooth muscle in bowels that causes pain.
List three characteristic features of multiunit smooth muscle
- ) Each fiber behaves as a separate motor unit.
- ) Little or no coupling between cells – Fibers not coupled together; need lots of individual nerve fibers
- ) Multiunit SM cells are densely innervated by POSTGANGLIONIC fibers of the PARASYMPATHETIC NERVOUS SYSTEM and SYMPATHETIC NERVOUS SYSTEM.
What type of smooth muscle is present in vascular smooth muscle?
A third type, which is a mixture of unitary and multiunit.
Where is multiunit smooth muscle found? (3)
Iris, ciliary muscles of the lens, and in the vas deferens.
What is a prime difference in calcium acquisition between smooth and skeletal muscle?
Recall that in skeletal muscle, the rise in intracellular Ca2+ concentration is caused EXCLUSIVELY by release from the sarcoplasmic reticulum—Ca2+ does not enter the cell from the ECF as it does in smooth muscle.
List two additional mechanisms for increasing intracellular [Ca2+] –one by acquisition from ECF, and one from within the cell.
- ) Ligand-gated Ca2+ channels in the sarcolemmal membrane; may be opened by various hormones and neurotransmitters, permitting entry of additional Ca2+ from the ECF.
- ) IP3 -gated Ca2+ release channels in SR membrane may be opened by hormones and neurotransmitters. Either of these may augment rise in [Ca2+] intracellularly.
The amount of tension in smooth muscle is proportional to what?
Ca2+ concentration.
Because myosin phosphorylation is required for smooth muscle contraction, it is said to be ______ regulated as opposed to ______ regulated in striated muscle.
thick-filament regulated as opposed to thin-filament regulated in striated muscle. p.313 Lipp
What prompts relaxation in smooth muscle? Describe the FIVE mechanisms by which this occurs.
Relaxation occurs when [Ca2+] fall below levels that can form Ca2+–Calmodulin complexes.
- ) Hyperpolarization (closes voltage-gated Ca2+ channels).
- ) Direct inhibition of Ca2+ channels by ligands such as cAMP, cGMP.
- ) Inhibition of IP3 production and decreased release of Ca2+ from SR.
- ) Increased Ca2+ ATPase activity in the SR.
- ) Activation of myosin-light-chain phosphatase; which dephosphorylates myosin light chain, leading to inhibition of myosin ATPase.
How can osmotic pressure be measured physically?
Osmotic pressure can be measured physically as the amount of pressure required to precisely counter water movement between two solutions with dissimilar solute concentrations.
How would you stimulate smooth muscle contraction without altering the membrane potential?
Binding of NE or Epi to alpha-adrenergic receptors.
What releases Ca2+ from intracellular stores during pharmacomechanical coupling?
IP3 –Ligand binding activates membrane PLC, which cleaves PIP to produce IP3.
What is the most common treatment for episodic bouts of myasthenia gravis?
Cholinesterase inhibitor (e.g. NEOSTIGMINE) –Allows ACh to be present longer/in greater concentration at the neuromuscular junction.
What unit of muscle is covered by SR, and invaginated by T-tubules?
What are its constituent parts?
Myofibrils –Thick and thin filaments arranged as sarcomeres.
If muscle contraction is to occur, ______ must be moved out of the way so that actin and myosin can interact.
tropomyosin
What is troponin and what are the three types?
Troponin is a complex of three globular proteins (troponin T, troponin I, and troponin C) located at regular intervals along the tropomyosin filaments.
Troponin T (T for tropomyosin) attaches the troponin complex to tropomyosin. Troponin I (I for inhibition), along with tropomyosin, inhibits the interaction of actin and myosin by covering the myosin-binding site on actin. Troponin C (C for Ca2+) is a Ca2+-binding protein that plays a central role in the initiation of contraction. When the intracellular Ca2+ concentration increases, Ca2+ binds to troponin C, producing a conformational change in the troponin complex.
What runs down the middle of each I-band?
Z-discs
- ) What comprises each A-band?
2. ) Describe their delineation
- ) Thick filaments = myosin = potential overlap of actin and myosin –cross-bridge formation.
- ) Run from I-band to I-band
Describe the bare zone
- ) Center of each sarcomere
- ) No thin filaments
- ) No overlap of thick and thin, thus…
- ) No cross-bridge formation
Titin extends from _____ to _____, running through _____.
Z-disc to M-line, running through the thick filament.
Describe the association and function of nebulin (3)
Associated with thin filaments.
- ) Holds G-actin together while they form into F-actin, i.e. nebulin is the lattice work around which actin attaches.
- ) Actin + Globules form around the nebulin to make filamentous actin (F-actin).
- ) A “molecular ruler” setting the length of thin filaments during their assembly.
Alpha-actin anchors the ________ to the Z disk.
thin filaments.
Give the three steps of troponin action
Action of troponin: Troponin I covering actin-myosin binding sites.
- ) Ca2+ binds to troponin C.
- ) Troponin T moves tropomyosin.
- ) Myosin heads can now bind actin.
At rest, why is the INTRAsarcoplasmic reticulum free-[Ca2+] very low?
Because it is stored in BOUND form by calsequestrin; a low-affinity high-capacity Ca2+ -binding protein.
In order for this force to be transmitted to the muscle surface, what must first happen?
the series elastic elements (e.g., titin) must first be stretched out.
Describe the activity of heat receptors, i.e. when they are active and inactive, and any substances that produce a reaction.
Become inactive below 36˚C, and inactive above 45˚C (activates nociceptors – pain…same for freezing temps).
-Transduction also by Transient Receptor Potential (TRP) channels – activated by capsaicin.
At what temperature will both heat and cold sensors be active?
36˚C
- ) When the skin is cooled below ____˚C, cold sensors become active and heat sensors become quiescent.
- ) Below what temperature are nociceptors activated due to cold?
- ) below 36˚C
2. ) 0˚C (freezing)
What type of sensation is present on the Dorsal column system? Describe its ascent in the CNS
Dorsal column = fine touch, pressure, proprioception.
Ascends on ipsilateral side to the brainstem, CROSSES AT THE BRAINSTEM, and travels on the contralateral side to the somatosensory cortex.
What type of sensation is present on the Anterolateral/spinothalamic System? Describe its ascent.
Anterolateral System = pain, temp, light touch.
Crosses at the level of the spinal cord, then travels to the somatosensory cortex.
Where are the 2nd order neuronal cell bodies located for both the upper and lower body in the Dorsal Column System?
Upper = Nucleus Cuneatus Lower = Nucleus Gracilis
Describe the process of edema after injury; what substance triggers edema?
- Nociceptors carry heat and mechanical pain information on UNMYELINATED (slow) C-fibers.
- SUBSTANCE P released in the skin causing vasodilation, and capillary permeability (redness, warmth).
What are three ways stimulus intensity can be encoded?
- ) Number of receptors that are activated
- ) Firing rates of sensory neurons in the pathway
- ) Activating different types of receptors, e.g. mechanoreceptors and nociceptors.
Receptor potentials are ________, whose amplitude correlates with ________.
- graded potentials
- size of stimulus.
- ) What type of treatment should be used to treat glaucoma (i.e. what receptors)?
- ) What does it act upon?
- ) ß-adrenergic antagonists reduce IOP by decreasing aqueous humor production and allowing it to drain more easily by relaxing the ciliary body p.186 Lipp.
- ) Targets the ciliary body
What is the visible spectrum?
450-700nm
What eye structure creates aqueous humor?
Epithelium of ciliary body.
Light enters the eye via the ______, which is continuous with the ______.
- cornea
- sclera
Describe the flow of aqueous humor from its production to draining (3 steps).
- ) Secreted into posterior chamber by specialized ciliary epithelium over the ciliary body.
- ) Flows through pupil, into the anterior chamber
- ) Drains via canals of Schlemm to the venous system.
The middle layers of the cornea are composed of collagen fibers along with supportive ______ and an extensive sensory nerve supply.
keratinocytes
Rings of ______ muscles that are controlled by ______ fibers from the ciliary ganglion decrease pupil diameter when they contract (an action called _______)
- sphincter
- postganglionic parasympathetic
- miosis
What is the purpose of sympathetic innervation of the ciliary body?
When a person is startled, their eyes automatically adjust for distant vision; relaxing the ciliary muscle and tightening the lens and suspensory ligaments.
Decreasing light levels stimulates _____ innervation, causing ______ of the _______ muscle and _____ of the pupil; what is this state/action called?
- Sympathetic innervation
- Causing constriction of radial muscle and dilation of the pupil.
- Mydriasis
Tensing the ciliary muscle does what to the focal length?
Decreases; near vision
The fovea is ___% of retinal size but accounts for _____% of the visual cortex. It contains only _____ (what kind of receptor cell?).
- 1% of retinal size, 50% of visual cortex.
- Contains ONLY CONES – no rods.
_____ are specialized to detect single photons of light.
Rods.
- ) Radial muscles controlled by _____ fibers originating in the _________.
- ) What is the affect on the pupil?
- ) PG SNS, superior cervical ganglion
2. ) widen the pupil (dilation) = MYDRIASIS.
The fovea’s lack of rods means that it cannot participate in _______.
night vision.
Describe the synapsing in the fovea
ONE cone synapsing on ONE bipolar cell, synapsing on ONE ganglion cell.
The highest concentration of cones is in the _____.
Fovea
What prevents the scattering of light in between the photoreceptors?
Pigment layer has tendrils into the photoreceptors to prevent scatter of light between photoreceptors.
Describe where the pigment layer is
Begins the retina begins just inside the choroid with a layer of pigment epithelium.
What would increase a photoreceptors sensitivity to light?
More photopigment (rhodopsin) = greater sensitivity to light.
Describe how rhodopsin is incorporated into 1.) Rods, and 2.) Cones
- ) In the rods, rhodopsin is inserted in new membrane discs, which are displaced toward the outer segment; eventually they are shed and phagocytosed by the pigment cell epithelium, giving the outer segments their rodlike shape.
- ) In the cones, rhodopsin is incorporated randomly into membrane folds, with no shedding process.
Describe the contents are actions of the inner and outer segments of rods and cones
Outer segments: Contains rhodopsin.
- Rods: Long stacks of discs.
- Cones: Short, single infolded.
Inner Segments: Connected to the outer segments by a SINGLE CILIUM.
- Contain mitochondria for power.
- Synthesizes rhodopsin.
- ) Axons from ______ cells form optic nerves and optic tracts.
- ) These axons synapse in ________, and end in the ________ in the _______.
- ) Retinal ganglion cells
2. ) lateral geniculate bodies, and end in the visual cortex in the occipital lobe.
Describe the relative amounts of rhodopsin in rods vs cones and the implication of these amounts.
Rods: LOTS
Cones: Less amount
-This means that rods are much more sensitive to light (only takes one photon to activate, whereas cones takes 100s of photons to activate).
Where is rhodopsin synthesized?
The inner segments, where the mitochondria are.
How are both rods and cones refilled with rhodopsin?
Rods: New rhodopsin discs made, pushed towards outer segment, with the end discs dropped off and discarded.
Cones: Rhodopsin inserted into membrane folds randomly with no shedding.
What allows for 3D vision?
The decussation at the optic chiasm.
The choroid runs up against the _____ in front, and the _____ in back. The ____ is the visible portion.
Ciliary body in front, Optic nerve in back.
Iris is the visible portion.
What is the choroid and what is its main role?
A thin membrane of BVs that nourish the outside of the retina.
The macula does not have a _______.
Blood supply; needs it from the choroid.
Aqueous humor forms in the _____ and is drained into the ______ where it exits via the ______.
Forms in the posterior chambers (from the ciliary body epithelium), drains into the anterior chamber, and exits via the canal of Schlemm.
Regeneration of 11-cis retinal requires ______, deficiency of which causes _______.
- requires VITAMIN A
- deficiency of which causes night blindness.
Horizontal cells do what?
Connects the surround of the bipolar cells and spreads the light out.
What do amacrine cells do?
Receive from multiple bipolar cells; mixes the ON and OFF patterns.
What would you find in the following retinal layers?
- ) Outer nuclear
- ) Outer plexiform
- ) Inner nuclear
- ) Inner plexiform
- ) Ganglion layer
1.) Photoreceptor nuclei
2.) Synaptic layer of pre- and postsynaptic elements from photoreceptors (postsyn), bipolar cells (presyn), and horizontal cells (pre- and postsyn).
3.) Cell bodies of Bipolar, horizontal, and amacrine cells.
4.) Second synaptic layer; Bipolar (postsyn), amacrine (pre- and postsyn), ganglion (presyn).
5.) Ganglia cell bodies.
DRAW THIS!
What accounts for the difference in acuity of the rods and cones?
- Many rods synapse on single bipolar cell = Light striking any of the rods will activate the bipolar cells.
- A single cone synapses on a single bipolar cell = many photons required to activate the bipolar cell.
Plasma and interstitial fluid are separated by _______.
the capillary wall.
What is the Gibbs-Donnan ratio? Give two examples
- ) Gives [plasma] relative to [IF] for anions – P.I.ANIONS (pianions).
e. g. GDR for Cl- = 0.95, because [Cl-]plasma/[Cl-]IF = 0.95 - ) Gives [IF] relative to [plasma] for cations.
e. g. Same number, but opposite ratio for Na+.
Diffusion is the only form of transport that is not _______.
Carrier mediated.
Give the five things diffusion depends upon
- Partition coefficient, ‘K’ (p.7, #13): Describes the solubility of a solute in oil relative to its solubility in water.
K = (Concentration in olive oil)/(Concentration in water) - Diffusion coefficient, ‘D’ (p.7): Correlates inversely with the solutes molecular radius (size) and the viscosity of the medium. Thus, small solutes in nonviscous solutions have the greatest diffusion coefficient and diffuse most readily.
- Concentration gradient = CA – CB
- Thickness of membrane (∆x): thicker membrane = slower diffusion.
- Surface area available for diffusion (A, in cm2): More SA = quicker diffusion.
Give the formula for Permeability (P, in cm/sec) and define variables
P = KD/∆x
where K is the partition coefficient
D is the diffusion coefficient,
and ∆x is the membrane thickness
Give the formula for Net diffusion (J, in mmol/sec) and define variables
J = PA(CA – CB)
P is the permeability
A is the SA available for diffusion
and Ca - Cb is the concentration gradient.
What is a lipid membrane highly permeable to? (name 4 things)
- ) CO2
- ) O2
- ) FAs
- ) Steroid Hormones
Fast pain (e.g. pin prick) is carried on______, ______, and ______ fibers, has a ______ onset and offset, and is _____ localized.
- A delta, group II, and group III fibers
- Rapid onset and offset
- precisely localized
For a long stimulus duration; the longer the stimulus, the longer the period in which the receptor potential ________.
exceeds threshold
What is the composition of the fluid in the scala media?
What is it similar to?
Endolymph –high [K+] and low [Na+]
•Similar to INTRAcellular fluid, but technically it is extracellular fluid.
Give two pertinent negatives for vertigo and nystagmus. What are they caused by (3)?
No hearing loss, no tinnitus.
•Caused by stroke, MS, toxicity (phenytoin)
- What causes BPV (benign paroxysmal vertigo)?
- When don’t symptoms occur?
- Treatment?
- Immobility of otoliths
- No symptoms while standing still
- Meclizine: antihistamine that stops endolymph production in the SCALA MEDIA and relieves pressure on hair cells.
For labyrinthitis:
- Two characteristics of the disease (not symptoms)
- Two associated symptoms
- What is the etiology?
- Acute, self-limiting
- Nystagmus and vertigo
- Infection of the vestibular system
For Meniere’s Disease:
- Two characteristics of the disease (not symptoms, but how/when it occurs)
- Four associated symptoms
- Etiology?
- Treatment? (3)
- Chronic, recurring (symptoms come and go)
- Nystagmus, vertigo, tinnitus, and hearing loss.
- Chronic overproduction of endolymph
- Treat with salt restriction and diuretics, may need surgical ablation.
For Acoustic Neuroma/Vestibular Schwannoma:
- Etiology?
- Associated symptoms? (4)
- Treatment?
- CN VIII lesion; pressure/crushing of CN VIII
- Tinnitus, vertigo, ataxia (the loss of full control of bodily movements), nystagmus
- Surgical removal (diagnose with MRI)
For Perilymph Fistula:
- Give one VERY IMPORTANT clinical finding
- Etiology
- Common cause
- Symptoms (4)
- Cannot directionalize sound with one ear
- Hole in oval or round window; leaks endolymph/perilymph. Results in a constant abnormal current
- Explosion/bomb
- Hearing loss, tinnitus, vertigo, nystagmus
What are two things that ONLY the PSNS controls?
- Lacrimation
- Gastric and pancreatic secretions (ACh increases)
•This is intuitive, as “resting and relaxing” is the only time you really want to digest food.
Explain the effect that the sympathetic NS has on salivation (including receptor)
Salivation decreased in relation to PSNS innervation (but with increased viscosity and decreased volume), but increased relative to zero innervation.
•Mediated by Beta-1 receptor
What are two metabolic functions controlled exclusively by beta-1 receptors?
Renin production and lipolysis
What are the spinal cord levels controlling sympathetic innervation for the adrenal medulla and via which nerve?
L5-T9 via the Greater Splanchnic nerve
Where are the pre-ganglionic cell bodies for both the SNS and PSNS?
SNS: IMLs at the T1-L3 cord levels
PSNS: Cranial nerves 3, 7, 9, and 10, and S2-S4
What are the exceptions to the “Sympathetic dilates and dries” rule? (2)
- Sweating (Muscarinic)
2. Ejaculation (alpha-1 and -2)
Parasympathetic innervation DOES NOT affect _______.
VASCULATURE
How to treat pheochromocytoma and why (i.e. what is pheochromocytoma)?
With alpha- and beta-blockers.
•Pheochromocytoma is a tumor on, around, or distant from adrenal medulla. Unlike post-ganglionic nerves which release only NE, the adrenal medulla produces mainly epinephrine (80%). It converts NE to its main product Epi via an enzyme produced in the adrenal medulla called PMNT. PMNT requires cortisol produced in the adrenal cortex to function. The tumor, unlike the adrenal medulla, secretes mainly NE because it is too far from the cortex to receive the cortisol required for the operation of PMNT.
p.50 cos (p.61 too)
What are the two best initial tests for a pheochromocytoma?
Urine catecholamines and metanephrines
What are the non-cholinergic PSNS neurotransmitters?
Vasoactive intestinal peptide (VIP) and nitric oxide.
Where are the ganglia located for PSNS preganglionic neurons to synapse on?
On top of target organs –> Long presynaptic axons, short post-synaptic axons.
What is the main anti-cholinergic drug?
Atropine –decreases secretions: Dry mouth, urine retention, constipation.
Which type of receptor controls erections?
Muscarinic
Which type of receptor controls erections?
Muscarinic
- What is the approximate value of threshold potential?
- What potential does is approached at the peak of AP?
- What is the actual value for the peak of AP?
- Threshold potential (Vth) ≈ -45mV
- Approaches, but doesn’t reach, Na+ equilibrium potential of +65mV
- +40mV
What is the effect of tetrodotoxin and lidocaine on APs?
They block voltage-gated Na+ channels and, therefore, inhibit APs.
- What is the best initial therapy for myasthenia gravis?
2. What are two diagnostic tests (and which is the best)?
- Acetylcholinesterase inhibitors, e.g. NEOSTIGMINE
- Edrophonium and test for ACh receptor antibodies (best initial test).
• A person tests positive for myasthenia gravis if their muscles get stronger after being injected with edrophonium.
- What is an EPSP and what does it do?
2. Give five neurotransmitters that elicit EPSP’s
- Excitatory post-synaptic potential: Brings membrane closer to threshold/depolarization by opening Na+ and K+ channels – i.e. makes the membrane more positive (close to a potential halfway between eq. potentials of Na+ and K+, ≈ 0mV).
- ACh, epinephrine, dopamine, glutamate, serotonin
* SAGED*
- What is an IPSP and what does it do?
2. Give two neurotransmitters that elicit IPSP’s
- Inhibitory post-synaptic potential: Takes membrane further away from threshold by opening Cl- channels (Cl- into cell), or opening K+ channels (K+ out) and hyperpolarizing membrane (makes membrane more negative).
• Drives membrane towards eq. potential of Cl- (≈ -90mV) - GABA, glycine
- What are the three amine NTs?
2. All biologic amine NTs are derived from what?
- Epi, NE, dopamine
2. Tyrosine
- What is serotonin made from?
- It is degraded by _____ to make _________.
- Turned into ______ by the ______ gland.
- Tryptophan
- MAO into 5-hydroxyindolacetic acid
- Melatonin by the pineal gland
