High Yield Final Exam Content

Physiology

The study of how living organisms and their parts function

Epithelial tissue

Tissue that covers body surfaces, lines cavities, and forms glands; acts as a barrier

Connective tissue

Tissue that supports, binds, and connects other tissues; includes fat, bone, cartilage, and blood

Muscle tissue

Tissue specialized for contraction; includes skeletal, cardiac, and smooth muscle

Nervous tissue

Tissue composed of neurons and glial cells; specialized for conducting electrical signals

Homeostasis

The maintenance of a stable internal environment despite changes in external conditions

Negative feedback

A regulatory mechanism where the response reverses the original stimulus to restore balance

Stimulus

The initial change that disrupts homeostasis and triggers a response

Sensor

The component that detects a stimulus and reports it to the control center

Effector

The organ or tissue that carries out the corrective response directed by the control center

Response

The action taken by the effector to counteract the stimulus and restore the set point

Bulk transport

Movement of large volumes of fluid driven by pressure gradients over long distances

Form vs. function

The principle that the physical structure of a tissue or organ predicts its biological role

Ganglia

Clusters of neuron cell bodies located outside the CNS

Cephalization

The evolutionary trend toward concentration of nervous tissue and sensory organs at the anterior end

PNS (Peripheral Nervous System)

All nerves and ganglia outside the brain and spinal cord; connects CNS to the body

CNS (Central Nervous System)

The brain and spinal cord; integrates and processes information

Neuron

A nerve is a bundle of axons; a neuron is a single cell that transmits electrical signals

Sensory neuron

A neuron that carries signals from sensory receptors toward the CNS (afferent)

Interneuron

A neuron within the CNS that connects sensory and motor neurons; involved in integration

Motor neuron

A neuron that carries signals from the CNS to effectors like muscles and glands (efferent)

Dendrite

Branched extensions of a neuron that receive incoming signals

Axon hillock

The region of the neuron where the axon meets the cell body; where action potentials are initiated

Axon

A single elongated extension of a neuron that conducts action potentials away from the cell body

Axon terminal

The end of the axon where neurotransmitters are released into the synapse

Presynaptic cell

The neuron that releases neurotransmitters into the synaptic cleft

Postsynaptic cell

The neuron or cell that receives neurotransmitter signals across the synapse

Synapse

The junction between two neurons or a neuron and its target cell where signals are transmitted

Neurotransmitter

A chemical messenger released from a presynaptic neuron that binds to receptors on the postsynaptic cell

Membrane potential

The voltage difference across a cell membrane due to unequal distribution of ions

Resting potential

The membrane potential of a neuron at rest; approximately -70mV

Action potential

A rapid, all-or-nothing electrical signal that travels down an axon

Threshold potential

The membrane voltage (~-55mV) that must be reached to trigger an action potential

Equilibrium potential

The membrane voltage at which the electrical force on an ion exactly balances its concentration gradient

Depolarization

A shift in membrane potential toward a less negative (or positive) value; caused by Na+ influx

Repolarization

The return of membrane potential toward resting after depolarization; caused by K+ efflux

Hyperpolarization

A membrane potential more negative than resting potential; occurs after repolarization due to slow K+ channel closing

Refractory period

The period after an action potential during which a neuron cannot fire again; ensures one-directional signal travel

Voltage-gated Na+ channel

Ion channel that opens in response to depolarization, allowing Na+ to rush in and drive the action potential

Voltage-gated K+ channel

Ion channel that opens after Na+ channel inactivation, allowing K+ to rush out and repolarize the membrane

Voltage-gated Ca2+ channel

Ion channel at axon terminals; Ca2+ influx triggers vesicle fusion and neurotransmitter release

Inactivation gate

The 'ball-and-chain' portion of a Na+ channel that plugs the channel milliseconds after it opens

Na/K pump

Transporter that actively pumps 3 Na+ out and 2 K+ in per cycle; maintains resting ion gradients

Leak channels (Na+ & K+)

Ion channels that are always open; K+ leak channels are much more numerous, contributing to the -70mV resting potential

Glial cell

Non-neuronal support cells of the nervous system

Node of Ranvier

Gaps in the myelin sheath where action potentials are regenerated during saltatory conduction

Saltatory propagation

The 'jumping' of action potentials from node to node along a myelinated axon; increases speed

Myelin sheath

Insulating layer of lipid-rich membrane wrapped around axons by oligodendrocytes or Schwann cells; speeds signal conduction

Vesicles (neurotransmitter storage)

Membrane-bound sacs in axon terminals that store and release neurotransmitters

Ligand-gated ion channel

An ion channel that opens when a specific neurotransmitter (ligand) binds to it

Synaptic cleft

The narrow fluid-filled gap between the presynaptic and postsynaptic membranes

EPSP

Excitatory PostSynaptic Potential; a depolarization of the postsynaptic membrane that moves it closer to threshold

IPSP

Inhibitory PostSynaptic Potential; a hyperpolarization of the postsynaptic membrane that moves it further from threshold

Temporal summation

Integration of multiple signals from the same neuron arriving in rapid succession

Spatial summation

Integration of simultaneous signals from multiple neurons converging on one postsynaptic cell

Afferent neurons

Neurons that carry sensory signals toward the CNS ('Afferent Arrives')

Efferent neurons

Neurons that carry motor commands away from the CNS ('Efferent Exits')

Somatic nervous system

Division of the PNS that controls voluntary skeletal muscle movement

Autonomic nervous system

Division of the PNS that controls involuntary functions like heart rate, digestion, and glands

Sympathetic nervous system

'Fight or flight' division of the autonomic NS; prepares body for stress and physical activity

Parasympathetic nervous system

'Rest and digest' division of the autonomic NS; promotes energy conservation and recovery

Motor endplate

The specialized region of a muscle fiber membrane where a motor neuron synapses

Acetylcholine (ACh)

Neurotransmitter released at the neuromuscular junction and by parasympathetic neurons

Reciprocal inhibition

In a reflex circuit, the simultaneous activation of one muscle and inhibition of its antagonist

Signal transduction pathway

A cascade of molecular events triggered by a receptor binding its ligand, converting an extracellular signal into a cellular response

Sensory receptor cell

A specialized cell that detects a specific type of stimulus and converts it into an electrical signal

Sensory transduction

The conversion of a stimulus (light, sound, chemical) into an electrical signal the nervous system can process

Chemoreceptor

A sensory receptor that detects chemical molecules (e.g., olfactory and taste receptors)

Mechanoreceptor

A sensory receptor that detects physical deformation such as pressure, touch, vibration, or sound

Photoreceptor

A sensory receptor that detects light (photons); includes rods and cones in the retina

Thermoreceptor

A sensory receptor that detects temperature changes

Nociceptor

A sensory receptor that detects painful or damaging stimuli

Lateral inhibition

A process where a strongly activated sensory neuron inhibits adjacent neurons, sharpening edge and contrast detection

G-protein coupled receptor (GPCR)

A receptor protein that activates an intracellular G-protein upon ligand binding, triggering a second messenger cascade

G-protein

An intracellular signaling protein activated by GPCRs; relays the signal to downstream effectors

Olfactory epithelium

The specialized tissue lining the nasal cavity that contains olfactory receptor neurons

Olfactory sensory neuron (ORN)

A sensory neuron in the nasal cavity that detects odorant molecules and sends signals to the olfactory bulb

Taste bud

A sensory organ on the tongue containing taste receptor cells that detect dissolved tastants

Five flavors

Sweet, salty, sour, bitter, umami; sweet, bitter, and umami use GPCRs; salty and sour use direct ion channels

Stereocilia

Hair-like projections on mechanoreceptor hair cells; deflection opens ion channels for mechanotransduction

Mechanoreceptor hair cell

A sensory cell in the inner ear that converts mechanical movement into electrical signals via stereocilia and tip links

Vestibular system

The sensory system in the inner ear that detects head position, gravity, and rotational movement

Semicircular canals

Three fluid-filled loops in the inner ear that detect rotational (angular) acceleration

Outer ear

Pinna and ear canal; collects and funnels sound waves to the eardrum

Middle ear

Malleus, incus, and stapes (ossicles); amplifies and transfers vibrations from the eardrum to the oval window

Inner ear

Contains the cochlea (hearing) and vestibular organs (balance); where mechanotransduction occurs

Malleus, incus, stapes

The three ossicles of the middle ear that mechanically amplify and transmit vibrations

Cochlea

The spiral, fluid-filled structure of the inner ear where sound is transduced into electrical signals

Eardrum (tympanic membrane)

Membrane that vibrates in response to sound waves; converts air pressure waves into mechanical vibrations

Oval window

The membrane-covered opening between the middle and inner ear where the stapes transmits vibrations into cochlear fluid

Basilar membrane

The membrane inside the cochlea that vibrates in response to sound; different regions respond to different frequencies (tonotopy)

Tectorial membrane

The membrane above the hair cells in the organ of Corti; stereocilia push against it, creating shear force

Organ of Corti

The structure on the basilar membrane that houses the hair cells responsible for hearing

Retinal

A light-absorbing pigment (vitamin A derivative) inside opsin proteins; changes shape from 11-cis to all-trans when hit by a photon

Opsin

A membrane protein that contains retinal; acts as a GPCR activated by light

Fovea

The central region of the retina with the highest density of cones; responsible for sharp, detailed vision

Retina

The light-sensitive tissue lining the back of the eye; contains photoreceptors, bipolar cells, and ganglion cells

Rod

A photoreceptor specialized for low-light and peripheral vision; does not detect color

Cone

A photoreceptor specialized for color vision and fine detail; requires brighter light than rods

Phototransduction cascade

The series of molecular events triggered by light hitting a photoreceptor, leading to hyperpolarization and reduced glutamate release