Neurophysiology and Communication
What is synaptic transmission?
The process that occurs at synapses and transfers information between neurons with neurotransmitters.
How do rods and cones differ in function and distribution?
Rods are highly sensitive to light and dominate the peripheral retina; cones are responsible for color vision and are concentrated in the fovea.
What structural feature distinguishes ionotropic from metabotropic receptors?
Ionotropic receptors form ligand-gated ion channels that open directly upon neurotransmitter binding, while metabotropic receptors are G-protein-coupled receptors (GPCRs) that initiate slower, second-messenger cascades.
What embryonic structure gives rise to the forebrain, midbrain, and hindbrain?
The neural tube
What is the tonotopic mapping in the cochlea and cortex?
Sound frequencies resonate at specific regions of the basilar membrane, projecting in an orderly fashion to auditory cortex.
How does TTX (tetrodotoxin) affect neuronal excitability?
TTX blocks voltage-gated Na⁺ channels, preventing the initiation and propagation of action potentials.
What type of receptor is used to detect odorants in the nasal epithelium?
G-protein-coupled receptors (GPCRs)
What are the 3 criteria for a chemical to be classified as a neurotransmitter?
It must be synthesized and stored in presynaptic neurons, released upon stimulation, and produce a specific effect on postsynaptic cells via receptors.
What is the significance of the sulci and gyri on the cerebral cortex?
They increase cortical surface area, allowing for greater cognitive capacity within a limited skull space
How does the vestibulo-ocular reflex (VOR) maintain visual stability?
It uses semicircular canal input to drive compensatory eye movements opposite to head rotation, stabilizing gaze.
What is the role of motor proteins in axonal transport? and what are they?
Kinesin moves anterogradely, and dynein moves retrogradely along microtubules to deliver proteins, organelles, and vesicles.
What are the three main parts of the ear and their primary functions?
The outer ear collects sound, the middle ear amplifies it via ossicles, and the inner ear transduces sound waves into neural signals.
What is the difference between an agonist and an antagonist at a neurotransmitter receptor?
Agonists activate the receptor to produce a biological response; antagonists bind without activating and block the receptor’s function.
What are the meninges and what layers compose them?
Protective coverings of the brain: dura mater (outer), arachnoid mater (middle), and pia mater (inner)
How do the pain and touch pathways differ?
Pain (spinothalamic) crosses in spinal cord and ascends contralaterally; touch (dorsal column) ascends ipsilaterally to medulla.
Describe the process of the action potential starting from the threshold
Once the threshold is reached by stimulus, Na+ voltage-gated channels open allowing in Na+ ions, causing depolarization. This is followed by the delayed opening of voltage-gated K+ channels causing K+ ions to leave the cell, resulting in repolarization and leading to hyperpolarization. Na+/K+ pumps then restore the resting membrane potential.
How does gustatory signal transduction differ for salty, sour, sweet, and bitter tastes?
Salty/Sour: Directly affects ion channels; Sweet/bitter/umami: GPCRs activate second messengers (IP₃/Ca²⁺ pathways).
What is the precursor molecule for dopamine synthesis, and which enzyme catalyzes its conversion to dopamine?
Tyrosine; converted by tyrosine hydroxylase to L-DOPA, then to dopamine by DOPA decarboxylase.
What are the four lobes of the cerebral cortex, and what primary function is associated with each?
Frontal (motor/executive), parietal (somatosensory), temporal (auditory/language/memory), occipital (vision)
What is the complete ascending pathway of auditory information from the cochlea to the primary auditory cortex, including key brainstem and thalamic relays?
Cochlea → cochlear nerve → cochlear nuclei (in medulla) → superior olivary complex (pons) → inferior colliculus (midbrain) → medial geniculate nucleus (thalamus) → primary auditory cortex
What is the functional difference between temporal and spatial summation in neurons?
Temporal summation integrates signals over time from one synapse; spatial summation integrates simultaneous inputs from multiple synapses.
How is head tilt detected in the vestibular system?
The otolith organs (utricle and saccule) contain hair cells embedded in a gelatinous layer topped with calcium carbonate crystals that shift with gravity.
What happens when glutamate binds to both AMPA and NMDA receptors during synaptic transmission?
AMPA receptors depolarize the membrane; if sufficiently depolarized, NMDA receptors unblock their Mg²⁺ and allow ion movement.
How does cerebrospinal fluid (CSF) flow through the ventricular system?
Lateral ventricles → third ventricle → cerebral aqueduct → fourth ventricle → subarachnoid space
What is the phototransduction cascade in rods?
Light activates rhodopsin → transducin → phosphodiesterase → cGMP breakdown → Na⁺ channels close → hyperpolarization.