neuro exam2

Neuron

The main communication cell of the nervous system.

Dendrites

Receive signals (input) for the neuron.

Cell body (soma)

Processes information within the neuron.

Axon

Sends electrical signals away from the soma.

Axon terminals (boutons)

Release neurotransmitters to communicate with the next neuron.

Action potential

An all-or-none electrical signal that travels down the axon.

Graded potential

A small change in membrane potential that can build up.

Depolarization

Process where sodium (Na⁺) channels open and the inside of the cell becomes more positive.

Repolarization

Process where potassium (K⁺) leaves the cell returning it to a negative state.

Sodium-potassium pump

Restores resting potential by moving 3 Na⁺ out and 2 K⁺ in.

Synapse

Junction between two neurons where neurotransmitters are exchanged.

Excitatory neurotransmitter

Increases the likelihood of the next neuron firing (e.g., glutamate).

Inhibitory neurotransmitter

Decreases the likelihood of the next neuron firing (e.g., GABA).

Acetylcholine (ACh)

Neurotransmitter involved in motor control and muscle contraction.

Dopamine

Neurotransmitter associated with reward, movement, and motivation.

Serotonin

Neurotransmitter involved in mood and sleep regulation.

Norepinephrine

Neurotransmitter related to alertness and stress.

Multipolar neurons

Neurons with many dendrites and one axon; most common type.

Bipolar neurons

Neurons with one dendrite and one axon; found in retina and olfactory system.

Unipolar neurons

Neurons with a single projection; primarily sensory neurons.

First-order neuron

Neurons that detect stimulus in skin or sense organs.

Second-order neuron

Located in spinal cord or brainstem; sends information to the thalamus.

Third-order neuron

Located in the thalamus; sends information to the cortex.

Dorsal column–medial lemniscus

Sensory tract responsible for fine touch, vibration, and proprioception.

Spinothalamic tract

Sensory tract that transmits pain and temperature information.

Trigeminothalamic tract

Sensory tract that carries information from the face to the thalamus.

Optic chiasm

Crossing point of nasal retinal fibers that allows both eyes to share vision.

Tonotopic organization

Auditory system arrangement where specific frequency sounds are represented in specific areas.

Perilymph

Fluid in the scala vestibuli and scala tympani of the cochlea.

Endolymph

Fluid in the scala media of the cochlea.

Motor unit

A motor neuron and all the muscle fibers it controls.

Neuromuscular junction

The site where a motor neuron communicates with a muscle fiber.

Upper Motor Neuron (UMN)

Neurons that project from the cortex to the brainstem or spinal cord.

Lower Motor Neuron (LMN)

Neurons that project from the brainstem or spinal cord to the muscle.

Pyramidal System

System responsible for voluntary movement controlled directly from the cortex to muscles.

Corticospinal tract

Pathway that controls limbs and body from the cortex to spinal cord.

Corticobulbar tract

Pathway that controls face and speech muscles from the cortex to cranial nerves.

Extrapyramidal System

System involved in automatic control of movement, posture, and reflexes.

Cerebellum

Brain structure responsible for coordinating timing, precision, and balance of movement.

Projection neurons

Neurons that send signals over long distances.

Local neurons

Neurons that communicate within a specific region.

Afferent

Refers to sensory neurons that carry information to the central nervous system.

Efferent

Refers to motor neurons that carry information away from the central nervous system.

LMN lesion

Causes weakness, atrophy, and fasciculations in affected muscles.

UMN lesion

Leads to spasticity and hyperreflexia in affected areas.