Nervous system

Afferent Neurons

Nerve cells that carry sensory information toward the central nervous system.

Efferent Neurons

Nerve cells that transmit motor commands from the central nervous system to the muscles.

Central Nervous System (CNS)

Comprises the brain and spinal cord.

Peripheral Nervous System (PNS)

Comprises all the nervous system structures outside the CNS.

Dendrites

Parts of a neuron that receive signals from other neurons.

Axon

Long projection of a neuron that transmits electrical impulses away from the cell body.

Myelin Sheath

Insulating layer around some axons that increases the speed of signal transmission.

Glial Cells

Supportive cells in the nervous system that assist and protect neurons.

Ion Channels

Protein structures that allow ions to pass through the neuron's membrane, opening in response to stimuli.

Resting Membrane Potential

The electrical charge of a neuron when it is not active, typically around -70 mV.

Action Potential

A rapid change in membrane potential that occurs when a neuron fires.

Graded Potential

A change in membrane potential that varies in size, unlike the all-or-nothing action potential.

Temporal Summation

The process of adding up graded potentials over time to increase the likelihood of an action potential.

Spatial Summation

The process of adding up graded potentials from different locations to affect the neuron's membrane potential.

Absolute Refractory Period

Time during which a neuron cannot fire another action potential regardless of the strength of incoming stimuli.

Relative Refractory Period

Time following an action potential during which a neuron can fire again, but requires a stronger stimulus.

Saltatory Conduction

The rapid transmission of impulses along a myelinated axon by jumping from node to node.

Continuous Conduction

Slow transmission of impulses along unmyelinated axons, which occur continuously along the membrane.

Synapse

The junction where two neurons meet and communicate.

Neurotransmitter

Chemicals that transmit signals across a synapse from one neuron to another.

EPSP (Excitatory Post-Synaptic Potential)

A depolarizing potential in the postsynaptic neuron that increases the likelihood of an action potential.

IPSP (Inhibitory Post-Synaptic Potential)

A hyperpolarizing potential in the postsynaptic neuron that decreases the likelihood of an action potential.

Cholinergic Neurons

Neurons that use acetylcholine as their neurotransmitter.

Gray Matter

Areas of the CNS rich in neuronal cell bodies.

White Matter

Areas of the CNS composed mainly of myelinated axons.

Dermatomes

Areas of skin supplied by sensory neurons from a single spinal nerve root.

Lobes of the Brain

Regions of the brain (frontal, parietal, temporal, occipital) associated with specific functions.

Diencephalon

Part of the brain that includes the thalamus and hypothalamus, playing key roles in sensory processing and homeostasis.

Brainstem

Part of the brain responsible for basic life functions like breathing and heart rate.

Cerebellum

Brain region that coordinates movement and balance.

Reflex Arc

The neural pathway that mediates a reflex action.

Sleep Stages

Different phases of sleep including REM and NREM, each with distinct brain activity patterns.

Brain Waves

Electrical impulses in the brain categorized as delta, theta, alpha, beta, or gamma waves.

Sensory Receptors

Specialized cells that detect stimuli from the environment.

1st Order Neuron

Sensory neuron that transmits signals from sensory receptors to the spinal cord.

2nd Order Neuron

Neuron that transmits sensory signals from the spinal cord to the thalamus.

3rd Order Neuron

Neuron that carries sensory information from the thalamus to the cerebral cortex.

Referred Pain

Pain perceived at a location other than the site of the painful stimulus.

Accommodation

The process by which the eye adjusts its focus for viewing at different distances.

Visual Reflection

The bending of light rays when they hit a surface.

Control of the Iris

Regulation of pupil size to control the amount of light entering the eye.

Retina Cells

Photoreceptor cells in the retina (rods and cones) that detect light.

Visual Pathway

The route that visual information takes from the retina to the visual cortex.

Hair Cells in the Ear

Sensory cells in the cochlea that transduce sound vibrations into neural signals.

Pathway of Sound in the Ear

The route sound waves take from the outer ear, through the middle ear, to the inner ear.

Taste Modalities

The basic taste sensations: sweet, sour, salty, bitter, and umami.

Nerves of Taste

Cranial nerves that transmit taste information from the tongue to the brain.