Physio 1 Exam 2 - General

How does the Nernst Potential equation reflects the steady state equilibrium of two solutions with charged ions separated by a semipermeable membrane?

-The Nernst equation shows how charged ions distribute themselves across a semipermeable membrane at equilibrium.

-Electrical forces exactly balance diffusion.

-As cells move down their concentration gradient, they carry their charges with them, which creates a current in the opposite direction.

What is the driving force across a membrane?

-Driving force is the difference between the measured potential (Em) and the equilibrium potential (Ex).

-Ex is the lowest energy state.

-Equilibrium is when the driving force is zero. There is still movement across the membrane, but no bulk movement.

What is a negative driving force?

-When cations enter the cell and anions exit.

-Inward current.

What is a positive driving force?

-When cations exit the cell and anions enter.

-Outward current.

What is the circuit model for a cell membrane (R-C circuit), and how does current propagate down an axon?

-The membrane can be modeled as resistors (ion channels) and capacitors (lipid bilayer) in parallel, hooked up in series.

-Nerves have long axons that propagate action potentials.

-Depolarization passively spreads to adjacent areas of the membrane.

-Capacitance and Resistance aspects of the membrane determine the time and distance of depolarization spread.

What are the similarities and differences between the Goldman-Hodgkin-Katz (GHK) and Chord Conductance equations?

-Both equations find the measured potential.

-The Goldman-Hodgkin-Katz equation weighs the equilibrium potential of each ion by the relative permeability of each ion across the membrane.

-The Chord Conductance equation weighs the equilibrium potential of each ion by relative conductance.

How do you interpret plots of current vs voltage for specific ionic currents?

-Reversal potential is when the current changes from negative to positive.

-Negative current is when positive charges enter the cell.

-Positive current is when positive charges exit the cell.

-Cord conductance (Ii) is the slope of the line connecting the curve to its reversal potential.

-Slope conductance (g) is the slope of the curve at any Em.

What are the stages of an action potential?

-Stimulus-response latency is the time lag of the change in membrane potential for the stimulus.

-Absolute refractory period is about 1-2 ms, when it is impossible to have a second action potential.

-Relative refractory period is about 4 ms, when it's possible to have a second action potential, but it is more difficult than in the resting cell.

-Overshoot is a period of action potential where the membrane potential is positive.

-Hyperpolarizing after potential is when the membrane potential becomes more negative.

What are the underlying ionic currents that cause action potential?

-1. Resting membrane potential: ~-70 mV, K+ and Cl- conductance and permeability are high, ion channels are open, and they are near equilibrium potential. Na+ conductance and permeability are low, and ion channels are closed.

-2. Upstroke of action potential: ~-60 mV, threshold depolarizes, and Na+ channels open, causing an inward Na+ current.

-3. Repolarization: Na+ channels close after a set time, and the upstroke is terminated, and the membrane repolarizes. K+ channels open due to depolarization and cause a net outward K+ current.

What is rheobase?

Rheobase (Irh) is the strength of the stimulus current; the current that requires infinite time to elicit an action potential.

What is chronaxie?

Chronaxie (Tsd) is the strength-duration time constant; the time at which the threshold current is twice the rhinobase.

How do the Na+ inactivation and activation gates work to time the phases of an action potential?

-Na+ channels are selective for Na+ by size and concentration.

-The activation gate has voltage-dependent opening and opens during depolarization. It is closed during rest.

-The inactivation gate closes at a prescribed time after the membrane depolarizes. It is open during rest.

-Both gates must be open for Na+ conductance.

What are the 2 major reagents used to experimentally block Na+ and K+ channels?

-Tetrodotoxin (TTX) comes from puffer fish toxin and blocks Na+ conductance by binding to Na+ channels. An action potential does not occur.

-Tetraethylammonium (TEA) blocks K+ channels so that repolarization cannot occur.

What is the difference in the stochastic behavior of single Na+ ion channels and the more predictable, collective behavior of many Na+ ion channels?

Stochastic is the fact that the behavior of the average of channels is predictable, but the behavior of individuals is erratic.

What is the concept of patch clamping to measure single-channel ionic currents?

-Patch clamping is the method to study single channels.

-You apply a voltage over a membrane 'patch' and measure the current.

-You use inhibitors to look at specific channels.

What does the time constant tell you about nerve conduction velocities?

The time constant (T) is the amount of time for a current to cause the potential to reach 63% of its final value. How fast the membrane depolarizes.

What does the length/space constant tell you about the current spread?

The length constant (lambda) is the distance for the current to cause the potential to fall to 63% of its final value. How far the current spreads down the nerve.

How does myelin increases the conduction velocity of nerves?

-Myelination allows signals to propagate faster.

-Increases membrane resistance and the length constant (lambda).

-The current travels faster due to low resistance and a large size.

-Less current is required for depolarization.

How do nodes of Ranvier help to propagate current down myelinated axons?

-These nodes are periodic gaps in myelin wrapping.

-Saltatory conduction is when the current jumps from node to node.

-Nodes are rich in voltage-gated sodium channels that allow the action potential to regenerate.

-Leapfrogging increases the speed of transmission.

How does axon diameter relate to conduction velocity?

-A higher axon diameter means a higher conduction velocity.

-A lower axon diameter means a lower conduction velocity.

What are the general steps in synaptic transmission on the cellular level?

1. Neurons are stored in vesicles (small synaptic or large dense core vesicles).

2. The action potential opens voltage-gated Ca2+ channels.

3. Ca2+ binds to synaptotagin and causes vesicles to open.

4. Neurotransmitters diffuse through the gap.

5. Neurotransmitters bind to receptors on the post-synaptic terminal and include something.

6. The neurotransmitter signal is shut off by destruction, diffusion, or reuptake.

What are the parts of a neuron - soma, dendrites, axons, and how are these parts arranged in synapses?

-Soma is the cell body.

-Dendrites are extensions of the soma that receive signals from other neurons.

-Axon is the long projection that transmits electrical impulses.

-A synapse is the junction between two neurons where communication occurs.

-The presynaptic neuron sends the signal through its axon.

-The postsynaptic neuron receives the signal through its dendrites.

-The Synaptic cleft is the gap between the presynaptic terminal and postsynaptic dendrite.

What are the differences between excitatory and inhibitory post-synaptic potentials?

-Excitatory postynaptic potentials depolarize post-synaptic cells. Uses Na+ (+65 mV) and K+ channels (-85 mV).

-Inhibitory postsynaptic potentials hyperpolarize post-synaptic cells. Use Cl- channels (-90mV).

What is temporal summation?

When two or more presynaptic inputs arrive at a single post-synaptic cell in rapid succession.

What is spatial summation?

When two or more presynaptic inputs arrive at a single post-synaptic cell simultaneously.

How is long-term potentiation induced in the hippocampus, and what is its role in memory formation?

-Long-term potentiation is a persistent strengthening based on recent patterns of activity.

-Triggered by rapid, repeated stimulation that increases the rate of neurotransmitter release and receptor sensitivity.

-Same input produces a stronger response.

-Important in the formation of memories.

What are the basic divisions in the nervous system?

1. Central nervous system (behind the blood-brain barrier). Brain and spinal cord.

2. Peripheral nervous system [somatic (voluntary) and automatic (involuntary)]. Efferent and afferent signals.

3. Effector organs (muscles and organs)

What are the major differences between the peripheral and central nervous systems?

-The central nervous system includes the brain and spinal cord. They are encased in bone for protection and are behind the blood-brain barrier.

-The peripheral nervous system is everything outside the blood-brain barrier. Afferent nerves send signals to the CNS. Efferent nerves send signals away from the CNS. Includes the somatic sensory system, somatic motor system, and autonomic nervous system.

What are glial cells?

-Non-neuronal cells in the nervous system that support, nourish, and protect neurons.

-The 'glue' of the nervous system.

Which cells myelinate axons in the peripheral system?

-Schwann cells are in the PNS and form myelin sheaths.

-Each cell wraps around a single segment of an axon.

Which cells myelinate axons in the central

nervous system?

-Oligodendroglial cells are in the CNS and form myelin sheaths.

-One cell can myelinate multiple cells.

What is the structure and function of the blood-brain barrier?

-The BBB is a highly selective, semipermeable boundary between the bloodstream and the brain's extracellular fluid.

-Astrocytes cover brain capillaries and parts of neurons. They help form the BBB and take up ions and neurotransmitters.

-The BBB protects the brain from toxins, maintains homeostasis, supports neural function, and prevents immune cell infiltration.

What are the major types of chemical transmitters in the synapse (neurotransmitters)?

-The main things that release signals.

-They are synthesized near the axon terminal and are released by the presynaptic cell to act on the postsynaptic cell.

-They are degraded and recycled.

What are the major types of chemical transmitters in the synapse (neuropeptides)?

-Synthesized in the soma and transported down the axon.

-Neuromodulators act on presynaptic cells to alter neurotransmitter release.

-Neurohormones are released into the blood.

What are the major types of chemical transmitters in the synapse (nitric oxide)?

-A gas that diffuses across the synaptic terminals.

-Produced at the membrane and is important in smooth muscle cells.

What are the major types of chemical transmitters in the synapse (purines)?

-Include as ATP and adenosine.

-Act on smooth muscle contraction.

-They are co-secreted with neurotransmitters

What are ionotrophic receptors?

-Ligand-gated ion channels.

-They have rapid action (0.1 -0.2 ms).

What are metabotropic receptors?

GPCRs that have longer activation and effect times.

What are the receptors of Dopamine, and do they induce ESPSs or ISPs?

-D1 and D2 G protein-coupled receptors (GPRCs).

-D1 activates protein kinase A (PKA) and induces depolarization (ESPSs).

-D2 induces hyperpolarization (ISPSs).

What are the receptors of Glutamate, and do they induce ESPSs or ISPs?

-NMDA receptors (increase Ca2+ flux, ionotropic) that induce EPSP.

-AMPA receptors (increase Na+ and K+ flux, ionotropic) induce EPSP too.

What are the receptors of gamma-aminobutyric acid (GABA), and do they induce ESPSs or ISPs?

-GABAa receptors (increase Cl- flux, ionotropic) that induce ISPS.

-GABAb receptors (increase K+ efflux, metabotropic) induce ISPS.

What are the receptors of Serotonin, and do they induce ESPSs or ISPs?

5-HT receptors (5-HT1 - 5-HT7, 5-HT3 is ionotrpic, rest are metabotropic) that induce EPSPs.

What are the basic functions of the frontal lobe?

Foresight, planning, and motor tasks.

What are the basic functions of the Parietal Lobe?

Process sensory input, understanding speech (Wernicke's area)

What are the basic functions of the Temporal Lobe?

Process sensory input for retention of visual memory, language comprehension, and emotional association.

What are the basic functions of the Occipital Lobe?

Processing vision.

What are the basic functions of the Pons?

Balance, posture, regulation, and breathing.

What are the basic functions of the Medulla?

Automatic control of breathing and blood pressure; coordination of swallowing, coughing, and vomiting reflexes.

What are the basic functions of the Spinal Cord?

Relays signals between the brain and the body.

What are the basic functions of the Cerebellum?

Movement (coordination, planning, and execution) and posture maintenance.

What are the basic functions of the Amygdala?

-Emotions

-Communicates with the autonomic nervous system through the hypothalamus.

What are the basic functions of the Hippocampus?

Learning and memory.

What are the basic functions of the Basal Ganglia?

-Nerve centers that regulate movement.

-Receives input from all cerebral lobes and projects to the frontal cortex via the thalamus.

What are the basic functions of the Thalamus?

-Processes sensory information going to the cortex.

-Processes motor information coming from the cortex to the brain stem and spinal cord.

What are the basic functions of the Hypothalamus?

Regulates body temperature, food intake, and water balance by communicating with the pituitary gland.

What are the basic purposes of cerebrospinal fluid?

-Lacks protein content in plasma, so it has increased ions to maintain osmolarity.

-Density is similar to brain, so brain 'floats.'

-Protects and cushions the brain (shock absorber), reduces the effective weight of the brain (floating), delivers nutrients, removes waste, and maintains homeostasis (stable chemical environment).

-Completely replaced 3-4 times per day.

What are enteroreceptors and examples?

-Sense external stimulus.

-Examples include eyes, cochlea, vestibular apparatus (balance), olfactory epithelium, taste buds, touch receptors, temperature, pressure, nociceptors (pain), and skin stretch receptors.

What are interoreceptors and examples?

-Sense internal stimulus.

-Examples include stretch receptors (blood vessels, intestines, and bladder), chemosensors (CO2, O2, and glucose), pH sensors, nociceptors, muscle length, muscle tension, proprioceptors (position and movement), temperature, and osmoreceptors (osmotic pressure).

What is the general structure of synaptic relays?

-Synaptic relays relay information to the brain that leads to changes in behavior.

-Relay nuclei are synapses that integrate converging information an (integrated bundle where synapses converge).

-Interneurons form shorter-range synapses in relay nuclei.

-Projection neurons extend long axons to synapse at farther sites.

-1st order neurons have soma in the dorsal root or spinal cord ganglia. May be the same or separate from the receptor.

-2nd order neurons have soma in the real nucleus in the spinal cord or brain stem. They process and modify information and cross at the midline.

-3rd order neurons have soma in relay nuclei in the thalams. They process and modify information.

-4th order neurons have soma in the sensory area of the cortex. They integrate complex sensory information.

What is the role of the dorsal column system, and what is its path in the spinal cord and brain?

-The dorsal column system is responsible for discriminative touch, pressure, vibration, and proprioception. The lower body and upper body have different paths.

-1st order (dorsol root/cranial ganglia) -> 2nd order (medaulla, cross midline) -> 3rd order (thalamus) -> 4th order (somatosensory cortex).

What is the role of the anterolateral column system, and what is its path in the spinal cord and brain?

-The anterolateral column system is responsible for pain, temperature, and light touch. Skips medualla. 1st order and 2nd order on same vertebrae.

-1st order (dorsol root/cranial ganglia) -> 2nd order (spinal cord, cross midline) -> 3rd order (thalamus) -> 4th order (somatosensory cortex).

What does Ipsilaterally mean?

Ascending on the same side as the signal.

What does Controlaterally mean?

Ascending on the opposite side of the signal.

What are the basic concepts of the somatosensory homunculus?

-The somatosensory cortex maps back to the locations it takes information from.

-The somatosensory homunculus is how big a part of the body would be if it were mapped to the size of the area in the somatosensory cortex.

-The face, tongue, legs, and hands take over more area than other body parts, such as internal parts.

What is the sensation, nerve fiber, and the relative conduction velocity of the Pacinian corpuscle?

Vibration, large myelinates (Abeta), and 30-70 m/s.

What is the sensation, nerve fiber, and the relative conduction velocity of the Meissner's corpuscle?

Flutter and tapping, large myelinated (Abeta), and 30-70 m/s.

What is the sensation, nerve fiber, and the relative conduction velocity of the Merkel's disks?

Touch and pressure, small myelinated (Adelta), and 12-30 m/s.

What is the sensation, nerve fiber, and the relative conduction velocity of the Ruffini's corpuscles?

Touch, pressure, and proprioception, large myelinated (Abeta), and 30-70 m/s.

What is the sensation, nerve fiber, and the relative conduction velocity of the Nerve ending?

Touch, large myelinated (Abeta), 30-70 m/s.

What is the sensation, nerve fiber, and the relative conduction velocity of the Cold receptor?

Cold, small myelinated (Adelta), 12-30 m/s.

What is the sensation, nerve fiber, and the relative conduction velocity of the Warm receptor?

Warmth, small unmeylinated (C), 0.5-2 m/s.

What is the sensation, nerve fiber, and the relative conduction velocity of the Nociceptors (1st pain)?

1st pain, small myelinated (Adelta), and 12-30 m/s.

What is the sensation, nerve fiber, and the relative conduction velocity of the Nociceptors (2nd pain)?

2nd pain, small unmyelinated (C), and 0.5-2 m/s.

What is epicritic pain?

-First pain.

-It is immediate, sharp, and highly localized.

-Small myelinated (Adelta).

What is protopathic pain?

-Second pain.

-It has a 1 s delay, throbbing, and polymodal (can sense many different stimuli that cause pain).

-Small unmyelinated (C).

What are receptive fields?

-Areas of the body that, when stimulated, result in a change in the firing rate of sensory neurons.

-Can be excitatory or inhibitory.

-Smaller fields indicate locations of the stimulus more precisely.

How does lateral inhibition work?

-Lateral inhibition is how the body gets smaller receptor fields.

-Consists of inhibitory receptive fields bound to excitatory receptive fields.

-The activated neurons inhibit neighboring neurons.

How do modality, location, and duration of stimulus affect sensory encoding?

-Sensory encoding is how the brain knows where the stimulus is and what type it is.

-Modality: Encoded by dedicated pathways (Ex: pain always goes through the same pathway).

-Location: Encoded by the receptive field.

-Duration: Duration of firing of sensory neurons.

What is frequency encoding?

-A time of temporal coding.

-The frequency of a sensory receptor firing encodes the intensity of the stimulus (higher frequency = higher stimulus).

What is population encoding?

-When the number of sensory receptors firing within a time frame encodes the stimulus intensity.

-(more neurons = higher stimulus; spatial summation).

What is Steven's Power Law?

-A logarithmic relationship between stimulus and response.

-How heavy a weight actually is versus how heavy you feel it is.

What are the two types of adaptation - phasic and tonic?

-Adaptation is when the frequency of an action potential declines over time when a constant stimulus is applied.

-Tonic receptors respond continuously to a stimulus as long as it is present. They are slow to adapt.

-Phasic receptors respond quickly to changes in stimulus intensity and stop firing if the stimulus remains constant. They rapidly adapt.

How do the neural maps of the body relate to spinal segments (dermatome,

myotome, sclerotome)?

-The body is divided into segments that relate to areas in the spinal cord.

-Dermatome is the skin element (sensory nerves).

-Myotome is the muscle element (efferent motor nerves).

-Sclerotome is the bone element (vertebrae).

What are the qualities of sound perception, including pitch, timbre, and

loudness.?

- Pitch is the perceived counterpart of tones (higher frequency = higher pitch).

-Timbre is the presence of a mixture of frequencies.

-Loudness is intensity.

What are decibels?

Sound waves are compression waves measured in decibels (dB).

What are the functions of the outer ear, middle ear, and inner ear?

-The outer ear helps focus sound into the ear and helps with sound localization.

-The middle ear contains the auditory ossicles (small bones) that provide a medium to transfer vibrations (concentrate sound). Converts sound waves into mechanical vibrations.

-The inner ear converts pressure waves to stimuli (hyperpolarization and depolarization) using the cochlea and hair cells. Mechanical vibrations are transformed into electrical signals.

Why is the tympanic membrane much larger than the oval window?

-The tympanic membrane is larger than the oval window to amplify sound vibrations.

-When sound waves hit the tympanic membrane, the force is concentrated onto the smaller oval window through ossicles, increasing pressure.

What is the afferent and efferent innervation of outer and inner hair cells? Why does this mean that the inner hair cells form the sensory response to sound?

-Inner hair cells receive ~20% of efferent fibers and are innervated by ~20 unbranched afferent fibers.

-Outer hair cells receive ~80% of efferent fibers and are innervated by branched afferent fibers (each hair cell has ~4, and each fiber connects to ~10 cells).

-Because of their dense afferent innervations, inner hair cells form the sensory response to sound (the main transducer of mechanical sound vibrations into electrical signals).

What are the cochlea, oval window, and round window?

-The cochlea consists of 3 compartments in a spiral shape with different fluids to convert pressure into electrical signals.

-The oval window leads to the cochlear (connects the middle ear to the inner ear). The stapes bone touches it.

-The round window is at the base of the cochlea and ensures proper fluid movement for accurate sound transmission.

What is "tonotopic mapping?"

-Tonotopic mapping is that signals are spatially processed in different areas based on frequency. -Higher frequency sounds stimulate hair cells at the base of the cochlea (closer to the round window).

-Low-frequency sounds stimulate hair cells near the apex (tip).

-allows the brain to decode complex sounds by analyzing where along the cochlear nerve the vibration occurs.

How do hair cells transduce sound waves?

-Perilymph fluid in the basolateral side has high Na+ and low K+ (enables action potential propagation).

-Endolymph fluid has high K+ and low Na+ (raises membrane equilibrium potential to +80mV).

-Bending cilia in one direction raises K+ conductance and causes depolarization.

-Bending cilia in the other direction lowers K+ conductance and causes hyperpolarization.

-Ca2+ channels open in the presynaptic terminals of depolarized cells, triggering glutamate release (excitatory neurotransmitter).

-Oscillating depolarization and hyperpolarization cause intermittent release of glutamate, firing of afferent cochlear nerves.

How is auditory sensory information traced from the spiral ganglia to the cochlear nuclei to the midbrain to the thalamus to the auditory cortex?

-1st order neuron (signals from spiral ganglia in modiolus go to cochlear nucleus in medulla). Where the audio and vestibular nerves join.

-2nd order neuron (midbrain). Ascend contalaterally (same side).

-3rd order neuron (thalamus)

-4th order neuron (auditory complex)

What is Broca's area?

-In the frontal lobe, near the motor cortex, and is responsible for motor control of the face, lips, jaw, tongue, pharynx, and larynx.

-Damage causes an inability to talk.

What is Wernicke's area?

-The posterior part of the temporal lobe adjacent to the second auditory cortex.

-Damage causes an inability to understand speech.

Where is the olfactory epithelium?

The bottom part of the cribifrom plate facing downwards towards the naval cavity.

What are the nerve tracts/synaptic relays involved in olfactory sensory transduction?

-2nd-order neurons send processed signals to the primary olfactory cortex (mostly in the temporal lobe, some in the cerebral cortex).

-Only sensory connection that does not travel through the thalamus before connecting with the cortex.

What is the cellular mechanism of olfactory sensory transduction (Gs mechanism linked to increased Cl- conductance)?

-Olfactory receptors are activated G-proteins (Golf)

1. Alpha subunit stimulates adenyl cyclase, which converts ATP to CAMP

2. CAMp binds to the ion channel and raises Ca2+ conductance.

3. Ca2+ influx raises local Ca2+ concentrations, activating Cl- channels.

4. Cell depolarizes, releasing odorant binding and stopping Golf.

5. Alpha subunit associates with beta.

6. Cyclic AMP phosphodiesterase makes CAMP into AMPt.

7. Ca2+ channels deactivate and Ca2+ in cytosol is removed.

How does increased Cl- conductance lead to depolarization in olfactory ensheathing cells?

Olfactory cells have a high intracellular Cl- concentration, so Cl- effluxes.

What are the parts of the tongue and papillae innervated by the glossopharyngeal nerve (CN IX), facial nerve (CN VII), and vagus nerve (CN X)?

-Circumvallate Papillae (back of tongue) - CNIX

-Folate Papillae (back and side or tongue) - CNIX

-Fungiform Papillae (front 2/3rds of tongue) - CNXII

-Pharynx and Epiglottis (block food from lungs) - CNX

What are the nerve tracts/synaptic relays involved in gustatory sensory transduction?

-Taste receptor cells release neurotransmitters (not neurons).

-1st order neurons (in CNVII, CNIX, and CNX) -> 2nd order neurons (medulla) -> 3rd order neurons (thalamus) -> 4th order neurons (primary gustatory cortex)