Physiology Laboratory: Reflexes and Sensory Systems

This set of vocabulary flashcards covers concepts related to sensory physiology, reflex arcs, the vestibular system, and the mammalian dive reflex as discussed in the lecture transcript.

Refraction

The bending of light as it travels through a medium that is denser than air.

Transduction

The conversion of any type of energy into action potentials, also more properly known as signal transduction.

Cones

Photoreceptors that require the stimulation of bright light and can detect millions of colors.

Hyperopia

A condition in which an individual can focus on far objects but not on near objects.

Astigmatism

A condition resulting from an irregular shaped cornea, often described as a fuzziness in vision.

Reflex

A rapid, unconscious, stereotyped response to a stimulus.

Dyssynaptic Reflex Arc

A reflex arc involving multiple synapses, typically used in pain withdrawal reflexes like pulling a finger away from a hot pan.

Monosynaptic Reflex Arc

A reflex arc involving only one synapse, also known as a stretch reflex.

Five Components of a Reflex Arc

A receptor, a sensory (afferent) neuron, an interneuron (association neuron), a motor (efferent) neuron, and an effector.

Interneuron

A type of neuron always found within the central nervous system that interfaces between sensory and motor neurons.

Synapse

A term meaning "gap," describing the interaction or interface between different parts of neurons.

Terminal Boutons

Also known as synaptic bulbs or synaptic termini, these structures release neurotransmitters at the end of an axon.

EPSP

Stands for Excitatory Postsynaptic Potential, which is an electrical change that excites the postsynaptic cell (the second cell after the gap).

Effector

The final component of a reflex arc, which can either be a muscle (which contracts) or a gland (which secretes).

Extrafusal Muscle Fibers

The typical contracting muscle cells that make up about $98\%$ to $99\%$ of all muscle cells.

Intrafusal Muscle Fibers

Also known as stretch fibers or spindle fibers, these make up about $1\%$ to $2\%$ of a muscle and are built like a spindle (fat in the middle and tapered at the ends).

Alpha Motor Neuron

The specific motor neurons that innervate every extrafusal fiber in the body.

Gamma Motor Neuron

A motor neuron that increases the sensitivity of intrafusal fibers by stimulating the contractile region to maintain stretch.

Alpha-Gamma Coactivation

The process where gamma motor neurons maintain constant stretch in muscle spindles throughout an action to prevent them from becoming flaccid during muscle contraction.

Consensual Response

A reflex where both sides of the body react to a stimulus applied to only one side, such as both eyes blinking when only one is stimulated.

Facilitation

The process of helping a reflex occur more strongly, often achieved by pre-stretching the spindle fibers of the body.

Babinski Reflex

A reflex tested on the bottom of the foot; a positive (present) response is toe extension (found in babies), while a negative (absent) response is toe curling (found in adults).

Cerebellum

The part of the brain that helps coordinate gross muscle movements, balance, and posture by integrating info from the inner ear.

Vestibular Apparatus

A weird apparatus in the inner ear used for balance, coordination, and posture, consisting of the utricle, saccule, and semicircular canals.

Utricle and Saccule

Components of the vestibular apparatus containing hair cells in endolymph that detect head position and linear acceleration.

Semicircular Canals

Three canals oriented in the x, y, and z planes that detect rotational movements.

Proprioception

The body's ability to detect its position and movement, contributing to eye-hand coordination.

IPSP

Stands for Inhibitory Postsynaptic Potential, which works through hyperpolarization to inhibit or stop a motion.

Vestibulo-Ocular Reflex

The brain connections between the vestibular apparatus and vision that allow eyes to maintain focus on a point while the head is moving.

Post-Rotatory Nystagmus

The tracking movement of the eyes in the opposite direction of spinning after the body has stopped rotating, caused by the continued movement of endolymph.

Cupula

A dome-shaped matrix of fibrous, elastic material located at the base of semicircular canals that deforms to trigger hair cells.

Depolarization

A process where neurons fire after reaching a threshold potential, causing transduction and nerve impulses.

Hyperpolarization

A process that moves the membrane potential away from the threshold, acting as the mechanism for inhibitory neurons.

Mammalian Dive Reflex

A reflex where immersion of the face in cold water (less than $10^\circ C$) causes a significant decrease in heart rate to conserve oxygen.

Parasympathetic Division

The homeostatic division of the autonomic nervous system, often called "rest and digest," that brings the body back to normal.

Sympathetic Division

The division of the autonomic nervous system responsible for the "fight or flight" response, taking the body away from homeostasis during stress or emergencies.