Physiology Study Guide

What is sensory transduction and why does it matter

It converts stimulus energy into receptor potentials so the nervous system can interpret the world

How does receptor adaptation help survival

It reduces response to constant stimuli so novel signals stand out

Why do mechanoreceptors need specialized structures

They shape stimulus filtering and sensitivity so only relevant forces trigger signals

How would damage to cilia on a sensory pit affect detection

It would blunt mechanotransduction and reduce sensitivity to ripples and pressure

Why does stimulus intensity encode as frequency not amplitude

Spike amplitude is fixed while higher intensity drives higher firing rates

How do receptive fields influence acuity

Smaller fields and higher density allow finer spatial discrimination

Why do lateral inhibition circuits increase contrast

Inhibitory interneurons suppress neighbors so edges appear sharper

What tradeoff exists between sensitivity and specificity in receptors

High sensitivity risks false alarms while high specificity may miss weak signals

How would cold water shift thermoreceptor activity

Cold receptors increase firing and warm receptors decrease firing to signal temperature drop

Why does multimodal integration improve detection

Combining cues reduces ambiguity and noise so perception is more reliable

How do hair cells convert motion into voltage changes

Stereocilia deflection gates ion channels and changes membrane potential

Why does stimulus duration affect coding strategy

Phasic receptors signal change while tonic receptors signal persistence

How would increased background noise in water affect ISO function

Signal to noise falls so the animal relies more on temporal patterns and integration

Why do threshold and dynamic range both matter

Threshold sets detection limits and dynamic range preserves differences across intensities

How does adaptation speed relate to stimulus statistics

Fast adaptation suits transient cues while slow adaptation suits sustained cues

Why are labeled lines useful for the brain

Dedicated pathways preserve modality identity from periphery to cortex

How would damage to the trigeminal branch alter perception

Facial mechanosensation and electroreception would be impaired

Why does spatial summation help weak stimuli be detected

Multiple subthreshold inputs add to cross threshold for spiking

How do temporal patterns encode stimulus features

Burst timing and interspike intervals carry information beyond rate

Why are chemoreceptors vital in aquatic habitats

Chemical plumes carry prey and danger information when vision is limited

How would an increase in water viscosity change mechanosensation

Ripple propagation changes and receptors may need closer range to detect movement

Why is adaptation reversible in healthy receptors

Molecular mechanisms reset channels and synapses to baseline

How do amplification mechanisms improve detection

Mechanical and electrical gain boosts small inputs into usable signals

Why is receptor distribution across the body uneven

Functional hotspots concentrate sensors where they are most useful

How does expectation modulate sensory gain

Top down input can increase or decrease sensitivity for task goals

Why are slow and fast mechanoreceptors both needed

They extract complementary features of the same stimulus

How would partial blockage of ion channels affect sensitivity

It raises threshold and narrows dynamic range

Why does the nervous system need noise tolerance

Biological sensors are noisy and robust coding preserves key information

How can redundancy improve reliability

Multiple sensors of the same type allow error correction

Why are internal states able to change perception

Neuromodulators alter receptor and circuit gain to match context

How are the central and peripheral nervous systems divided by function

The PNS gathers and delivers signals while the CNS integrates and commands

Why are glial cells essential and not passive

They support metabolism maintain ions modulate synapses and shape plasticity

How does myelination speed conduction

It increases membrane resistance and enables saltatory conduction at nodes

What determines conduction velocity in an axon

Axon diameter myelination and temperature set speed

How would demyelination change reflexes

Conduction slows and temporal dispersion weakens synchronous activation

Why do neurons have axon hillocks for spike initiation

Channel density and geometry create the lowest threshold region

How does the Nernst potential define ionic driving force

It sets the equilibrium voltage so differences drive current when open

Why is the resting membrane potential negative

Selective permeability to potassium and pumps create a negative interior

How do voltage gated channels create action potentials

Rapid sodium activation followed by potassium activation makes a spike

Why do refractory periods enforce directionality

Inactivated sodium channels prevent immediate reexcitation behind the wave

How does divergence and convergence support computation

Divergence broadcasts signals and convergence enables integration

Why are circuits organized into feedforward and feedback loops

Feedforward drives responses and feedback refines gain and stability

How would increasing extracellular potassium affect excitability

Higher potassium depolarizes cells and may trigger spontaneous firing

Why are sensory maps topographic

Ordered projections preserve spatial relationships for efficient processing

How do spinal reflexes illustrate sensorimotor integration

Afferents synapse on motor neurons for rapid automatic responses

Why does the autonomic system have dual divisions

Sympathetic and parasympathetic balance arousal and recovery

How do neuromodulators reconfigure circuits

They change channel properties and synaptic efficacy to shift network state

Why is energy supply crucial for neural coding

Spiking and pumping are ATP intensive so metabolism limits activity

How would hypoxia affect neural function

Reduced ATP impairs pumps and transmission causing failure of coding

Why do inhibitory neurons sharpen tuning

Inhibition sculpts timing and contrast to increase selectivity

How do central pattern generators produce rhythmic behavior

Reciprocal inhibition and intrinsic currents yield oscillations

Why are sensory afferents organized by modality and speed

Parallel pathways optimize timing and processing needs

How does plasticity in development shape circuits

Activity dependent pruning and strengthening refine connectivity

Why are the meninges and CSF important for function

They protect nourish and clear waste to preserve neural health

How would increased intracranial pressure impact signaling

Axonal and synaptic function degrade due to compression and reduced perfusion

Why do projection neurons and interneurons differ in roles

Projections carry information long distances while interneurons compute locally

How does the blood brain barrier support stable signaling

It regulates entry of molecules and shields circuits from toxins

Why are nodes of Ranvier spaced optimally

Spacing balances speed energy cost and reliability

How would temperature drops influence speed

Cooler temperatures slow kinetics and reduce conduction velocity

Why does redundancy appear in parallel pathways

It adds robustness and allows specialization for context

How do graded potentials differ from action potentials in function

Graded signals are analog and local while spikes are digital and long range

Why is the synapse often the limiting step for speed

Neurotransmitter release and diffusion add delay compared with conduction

How does calcium trigger vesicle release at synapses

Calcium binds sensors and drives vesicle fusion with the membrane

Why do SNARE proteins matter for transmission

They assemble the fusion machinery that releases transmitter

How would lowering extracellular calcium affect synaptic strength

Release probability falls and EPSPs weaken

Why does temporal summation depend on membrane time constant

Longer time constants allow EPSPs to overlap and add

How do spatial and temporal summation enable decisions

Multiple inputs integrate to reach threshold or fail

Why is inhibition not just the opposite of excitation

It controls timing gain and subthreshold dynamics to shape codes

How do metabotropic receptors alter network state

They change intracellular cascades and modulate channels for seconds

Why does short term plasticity encode recent history

Facilitation and depression adjust strength based on prior activity

How would synaptic depression influence sensory adaptation

Prolonged input weakens synapses and reduces response

Why does long term potentiation support learning

Hebbian pairing strengthens synapses to store associations

How does spike timing dependent plasticity add precision

Relative timing of spikes sets direction and magnitude of change

Why are axo axonic synapses powerful for control

They modulate release probability without changing postsynaptic gain

How do electrical synapses aid synchrony

Gap junctions pass current directly to align timing

Why would shunting inhibition change integration without big IPSPs

It increases conductance and reduces EPSP amplitude by division

How do neuromodulators bias plasticity rules

They gate kinase pathways and set whether potentiation or depression occurs

Why does dendritic location of synapses matter

Distance and branch properties shape local boosting and attenuation

How do backpropagating action potentials inform learning

They signal dendrites about outputs and enable coincidence detection

Why does receptor desensitization protect circuits

It limits overstimulation and preserves dynamic range

How would antagonists at receptors alter computation

They block channels or cascades and reweight circuit balance

Why do synapses use release probability rather than fixed output

Stochastic release supports flexibility and encoding of uncertainty

How does synaptic pruning improve efficiency

It removes weak or redundant connections to streamline processing

Why is homeostatic plasticity necessary

It stabilizes activity around set points despite perturbations

How do inhibitory plasticity rules support balance

They tune inhibition to track excitation and prevent runaway firing

Why are neuromodulatory systems good drug targets

Small changes can reconfigure large scale network dynamics

How would chronic stress alter synaptic function

It changes receptor expression and dendritic structure reducing plasticity

Why is coincidence detection central in sensory brain areas

Precise timing links features into coherent percepts

How do ensemble level dynamics emerge from synapses

Population interactions create oscillations and codes richer than single neurons

What is a circadian rhythm and why is it adaptive

It is a near 24 hour cycle that anticipates daily changes to optimize physiology

How does the SCN coordinate body clocks

It synchronizes peripheral oscillators via neural and hormonal signals

Why are zeitgebers important for alignment

External cues like light and feeding reset internal clocks to local time

How would constant dim light affect rhythms

Amplitude falls and phase drifts leading to internal desynchrony

Why does melatonin signal darkness not sleep

It conveys night timing and modulates systems that enable sleep propensity

How do clock genes create oscillations

Feedback loops of transcription and translation generate stable cycles

Why are peripheral clocks necessary

Local tissues time metabolism and function to their specific demands

How would night feeding shift liver clocks

Feeding time resets hepatic rhythms and may misalign with the SCN