Physiology Basics Flashcards
What percent of body weight is water? Extracellular fluid? Plasma? Interstitial?
Water: 60%
Extracellular: 20%
-Plasma: 4%
-Interstitial: 16%
What % of the blood is blood cell volume?
45%
What molecules can cross the cell membrane? Which ones can’t?
Can: hydrophobic molecules, small uncharged polar molecules
Can’t: large uncharged polar molecules, ions
What is Fick’s law and what does it measure?
It’s measures flux(diffusion)
J (out—>in) = -P(deltaC)
What happens to permeability as the width of the membrane increases?
Molecules becomes less permeable
What is the equation for CHEMICAL potential energy?
DeltaU = RTln (Cin/Cout)
DeltaU = 61log (Cin/Cout) @ 37 degrees
DeltaU = 58log (Cin/Cout) @ 20 degrees
What is the equation for ELECTRICAL potential energy?
ZFdeltaV
What is the equation for Gibb’s free energy (electrochemical potential)? What does it mean?
DeltaU = 61 log (Cin/Cout) + zFdeltaV
+ means work is done
- means no work is done
What are the two types of passive transport?
Diffusion
Facilitated diffusion
What are primary active transporters?
Systems linked directly to the cell’s metabolic energy
What are ABC transporters?
ATP-binding cassette transporter
May or may not actually use energy of ATP to transport molecules but needs ATP to be bound
What is secondary active transport?
Uses the gradient of an ion to drive the transport instead of ATP energy (Ex. Na-Glucose transporter)
What is the equation for the equilibrium potential of a single ion across a membrane?
Eion = 61/z log ([IONout/IONin])
What is the equation for the conductance of an ion?
I(ion) = g(ion)(Vm-Eion)
What does ouabain block and what are its affects?
Na/K ATPase - distrusts cell membrane potential
What does the pufferfish poison TTX affect?
It blocks Na+ voltage-gated channels in cells
What channels does TEA block?
K+ voltage-gated channels
What are gap junctions made out of?
Connexins
A temporal lag in relaying the message from one cell to the next via a synapse
Synaptic delay
Why is calcium ideally suited to be a second messenger within synaptic clefts?
It’s intracellular concentration is extremely low under resting conditions
Which SNARE protein is responsible for the tethering the vesicles to cytoskeleton structures to maintain a readily available reserve pool of neurotransmitters?
Synapsin
Which SNARE proteins mediate the docking of a vesicle to the specific release site (active zone)?
Synaptobrevin
Syntaxin
SNAP-25
Which SNARE protein senses the elevation of calcium and triggers the formation of the fusion pore to release intra-vesicular contents?
Synaptotagmin
How does botulinum toxin lead to paralysis?
It inhibits neurotransmitter release by causing proteolysis of synaptobrevin, syntaxin, and SNAP-25
Na/K ATPase inhibitor
Ouabain
A toxin that blocks voltage-gated sodium channels
Tetrodoxin
A toxin that blocks voltage-gated potassium channels
TEA
The result of hundreds of vesicles in a neuron fusing
EPP
The results of only one vehicle in a neuron fusing
MEPP
Describe the orientation of the activation and inactivation gates of the VGNaC at each step of the action potential.
Prior AP - A closed, I open
Depolarization - both open
Repolarization- A open, I closed
Undershoot - both closed
Return to baseline - A closed, I opens
Receptor molecule that is itself also an ionic channel
Ionotropic receptor
When the receptor is a separate entity from the ionic channels whose activity it controls; needs a “second messenger”
Metabotropic
How do IPSPs inhibit an action potential?
The STABILIZE the membrane at or near resting potential via increased permeability to Cl- —> antagonizes excitatory responses
Rapid burst of EPSPs in one neuron leading to an action potential
Temporal summation
Concurrent activation of two or more excitatory synapses converging on the same neuron to trigger an action potential
Spatial summation
How does increasing diameter of the axon affect the AP?
Less resistance
Receptors that bind ACh
Cholinergic
Receptors that bind EPI and NE
Adrenergic
What two receptors does ACh bind? Where are they found in the body?
Nicotinic - skeletal muscle and ANS ganglions
Muscarinic - smooth and cardiac muscle, glands
What are the two types of nicotinic receptors and where are they found?
N1 - skeletal muscle
N2 - autonomic nervous system ganglions
What inhibits N1 receptors?
Curare
What inhibits N2 receptors?
Hexamethonium
What inhibits muscarinic receptors?
Atropine
What receptors does NE bind to?
Alpha
Beta
What are the two types of alpha receptors and what are their functions?
A1 - constriction of blood vessel smooth muscle
A2 - regulatory; inhibits release of NE
What are the two types of beta receptors and what are their functions?
B1 - increases heart rate and force of contraction
B2 - relaxes GI tract and some vascular smooth muscle
What are the functions of the beta-2 and alpha-1 receptors in blood vessels?
Alpha 1 - constricts
Beta 2 - dilates
When lens cannot bring objects at close distance into focus; farsighted
Hyperopia
When lens cannot bring objects at far distance into focus; nearsighted
Myopia
When lens loses elasticity with age and ability to focus on close objects declines
Presbyopia
Photoreceptors that are extremely sensitive to light; respond to single photon; night vision
Rods
Photoreceptors that can discriminate between colors; respond maximally to light at a specific wavelength; day vision
Cones
Cones are highly concentrated where? What are they responsible for?
Fovea
High visual acuity
How does rhodopsin work and what is the cascade that follows it?
Photon absorption —> 11-cis retinal isomerizes to 11-trans retinal —> this detaches from opsin (“bleached”) —> GTP —> cGMP —>opens cGMP-gated channel —> influx of Na+ —> depolarization
What causes light adaptation?
A calcium feedback mechanism that leads to reduced light sensitivity
Cells that respond maximally to a bright dot in the center of their receptive field surrounded b an area of darkness
ON-center cells
Cells that respond maximally to a dark spot surrounded by an area of brightness
OFF-center cells
What cells are responsible for the lateral inhibition that allows for ON-center and OFF-center cells to function?
Horizontal cells
What happens if the optic chiasm is damaged?
Loss of peripheral vision
What happens if the left optic tract is damaged?
Loss of right visual field
What happens if the left optic nerve is damaged?
Loss of vision from left eye (left peripheral and right center)
What are the two different type of layers in the LGN and what kind of information do they provide?
Magnocellular (inner two layers) - high temporal resolution/rapidly changing or moving stimuli
Parvocellular (outer 4 layers) - high spatial resolution and color
What are the two types of cells in the visual cortex and what type of information do they respond to?
Simple - respond to bars/edges are particular orientations
Complex - respond to complex patterns or objects moving in a particular direction
How does the ear detect pitch?
High-pitched sounds will stimulate the baseball membrane near the oval window while low pitched sounds will stimulate the membrane near the apex
Influx of what ions depolarizers the hair cells of the ear?
K+ and Ca+2 ions
Involved in amplification and tuning of the movement of the basilar membrane
Outer hair cells
How is loudness measured in the ear?
By the rate of APs generated by the inner hair cells
What are the 3 bones in the middle ear?
Malleus
Incus
Stapes
What do the semilunarcanals of the vestibular system measure?
Angular accelerations and angular velocity of the head (orientation, rotation, and posture)
What do the utricle and saccule respond to?
Saccule - horizontal positioning
Utricle - vertical positioning
Where is the Ruffini ending located, what does it detect, and what kind of receptor is it?
- Cutaneous tissue
- Sustained pressure and temp
- Slow adapting
Where is the Pacinian corpuscle located, what does it detect, and what kind of receptor is it?
- Subcutaneous layer
- Pressure and vibration
- Rapid adapting
Where is the Merkel’s disk located, what does it detect, and what kind of receptor is it?
- Epidermis
- pressure, position, and deep static touch
- Slow adapting
Where is the Meissner’s corpuscle located, what does it detect, and what kind of receptor is it?
- Epidermis
- Touch and vibrations
- Rapid adapting
What do pain receptors do instead of adapting?
They sensitize —> leads to hyperalgesia
What are the two types of A pain fibers? What do they measure? What is a unique characteristic of them?
- fast, stinging pain
- myelinated
- A-delta (fastest)
- A-beta
What do the C pain fibers measure? What is a unique characteristic of them?
- slow burning pain
- unmyelinated and outnumber A fibers
What does the DCML tract measure? Where does is cross over? How many/what neurons are involved? Where does is terminate?
- sensory (fine touch, vibration, proprioception)
- medulla
- 3 neurons, A-alpha/A-delta
- somatosensory cortex
What does the spinothalamic tract measure? Where does is cross over? How many neurons are involved? Where does is terminate?
- pain + temp
- crosses at the level of entry in the spinal cord
- 2 neurons (A-delta and C neurons)
- somatosensory cortex
What are the three main differences between the neospinalthalamic and paleospinalthalamic pain pathways?
Neospinalthalamic - A-delta fibers; synapse in Laminae I and V; fast/stinging pain
Paleospinalthalamic - C fiber; synapse in Laminae V/VI-VIII; slow/burning
What are the collateral pathways of the pain pathways? Where do they project?
Spinomesencephalic - collateral of the neospinothalamic; projects to PAG/NRM in midbrain
Spinoreticular - collateral of the paleospinothalamic; projects to the thalamus through reticular formation
How do opiates (poppy seeds) and opioids (synthetic) disrupt the pain pathway?
- block cAMP formation
- block Ca+2 influx
- increase K+ efflux
What are come characteristics of red muscle?
- small alpha motor neuron
- high mitochondrial ATPase
- low glycogen
- high resistance to fatigue
- large blood supply
- tonic nerve activity
SMALL, SLOW TWITCH —> POSTURE
What are some characteristics of white muscle?
- large alpha motor neuron
- low mitochondrial ATPase
- high glycogen
- low resistance to fatigue
- small blood supply
- physic nerve activity
LARGE FAST TWITCH —> FIGHT/FLIGHT
Arranged in PARALLEL with muscle fibers —> measure muscle length; INTRAFUSAL
Muscle spindle
Embedded in series with the muscle fibers —> measure muscle tension; EXTRAFUSAL
Golgi tendon organs
Describe the homunculus on the cerebellum and the spinal cord.
Cerebellum - extremities are medial; face and trunk are lateral
Describe muscle spindle fibers and their mechanism of action.
Nuclear bag fibers/nuclear chain fibers sense stretch —> Ia afferent fibers send sensory info to spine/brain (stretch reflex) while gamma fibers send motor info to muscle spindle to maintain stretch
Keeps stretch receptors in tune and allows Ia afferent fibers to supports alpha motor neuron discharge
Compensatory loading
Describe Golgi tendon organs and their mechanism of action.
Stretch by an eternal load —> activated Ib afferent fibers —> reflex to counteract muscle action
Explain the nociceptive reflex.
Noxious stimuli —> relaxation of extensors and contraction of flexors of AFFECTED limb —> relaxation of flexors and contraction of extensors on OPPOSITE limb
What occurs during Brown-Sequard Syndrome (hemisection of the spinal cord)?
- below lesion: loss of motor control on ipsilateral side (corticospinal)
- below lesion: loss of pain/temp sensation on contralateral side (spinothalamic)
- below lesion: loss of fine touch/vibration sensation on ipsilateral side (DCML)
What is the cortico-bulbar tract and what does it control?
Motor neurons that project from primary motor cortex to brain stem —> controls muscles of face, tongue, and eyes
What is the difference between the lateral and anterior/medial corticospinal tracts?
Lateral - controls extremities and distal muscles
Anterior - controls axial muscles that maintain posture
The basal ganglia are associated with which two major types of action?
Reward and habitual actions
What is the role of dopamine in the direct and indirect pathways of the basal ganglia?
OVERALL GOAL = stimulate moment
It stimulates the direct pathway (D1) and inhibits the indirect pathway (D2) via striatum
What occurs during Parkinson’s disease?
Dopamine neurons degenerate so decrease in opamine —> inhibition of voluntary movements
Controls coordination and accuracy of voluntary movements
Cerebellum
What is Lambert Eaton Myasthenia Syndrome?
Antibodies against the voltage-gated calcium ion channels
What is myasthenia gravis?
Antibodies target ACh receptor (only N1 in muscle though! — no effect on autonomic system)
Breaks down acetylcholine
MAO
