General Biology II: Chapter 35

Neuron

Specialized cell that receives and transmits electrical and chemical signals.

Glia (Glial cells)

Support cells for neurons; provide nutrients, protection, and insulation.

Astrocyte

CNS glial cell that provides nutrients, maintains extracellular balance, and forms the blood-brain barrier.

Oligodendrocyte

Glial cell that forms myelin sheaths around axons in the CNS.

Schwann cell

Glial cell that forms myelin around PNS axons.

Microglia

Glial cells that act as immune defenders and remove debris.

Ependymal cell

Lines brain ventricles and spinal cord canal; produces cerebrospinal fluid (CSF).

Satellite cell

Glial cell in PNS that supports and nourishes neuron cell bodies.

Dendrite

Receives messages from other neurons.

Cell body (Soma)

Contains the nucleus; integrates signals.

Axon

Long projection that carries impulses away from the cell body.

Axon hillock

Region where signals are integrated and action potentials start.

Axon terminal

End of axon; releases neurotransmitters into the synapse.

Myelin

Fatty insulation that speeds electrical transmission.

Nodes of Ranvier

Gaps in myelin where action potentials 'jump.'

Resting potential

The -70 mV charge difference across a neuron's membrane at rest.

Action potential

Rapid, temporary change in membrane potential that travels along the axon.

Depolarization

Membrane potential becomes less negative (Na⁺ enters).

Repolarization

Return to resting potential (K⁺ exits).

Hyperpolarization

Membrane potential becomes more negative than resting state.

Threshold of excitation

Level of depolarization needed to trigger an action potential (~ -55 mV).

Voltage-gated ion channels

Open/close in response to voltage changes across the membrane.

Sodium-potassium pump

Uses ATP to maintain ion gradients (pumps 3 Na⁺ out, 2 K⁺ in).

Refractory period

Time after an action potential when the neuron cannot fire again.

Saltatory conduction

'Jumping' of action potentials from node to node in myelinated axons.

Synapse

Junction where neurons communicate.

Synaptic cleft

Space between pre- and postsynaptic cells.

Synaptic vesicle

Structure that holds neurotransmitters in the presynaptic neuron.

Neurotransmitter

Chemical messenger released at a synapse (e.g., acetylcholine, norepinephrine).

EPSP (Excitatory postsynaptic potential)

Depolarization caused by excitatory neurotransmitters.

IPSP (Inhibitory postsynaptic potential)

Hyperpolarization caused by inhibitory neurotransmitters.

Summation

Combining multiple EPSPs to reach threshold and trigger an action potential.

Central Nervous System (CNS)

Brain and spinal cord.

Peripheral Nervous System (PNS)

Nerves outside the CNS; carries signals to/from the body.

Somatic Nervous System

Controls voluntary skeletal muscle movement.

Autonomic Nervous System

Controls involuntary functions (heart rate, digestion).

Sympathetic Nervous System

Activates 'fight or flight.'

Parasympathetic Nervous System

Activates 'rest and digest.'

Brainstem

Connects brain to spinal cord; controls breathing, heart rate, swallowing.

Cerebellum

Coordinates balance, posture, and fine motor control.

Cerebrum

Largest brain part; controls reasoning, movement, and sensory processing.

Cerebral cortex

Outer layer responsible for higher cognitive functions.

Thalamus

Relays sensory information to the cortex.

Hypothalamus

Maintains homeostasis; regulates hormones, hunger, temperature.

Hippocampus

Processes and stores memories.

Frontal lobe

Planning, decision making, motor control, and language.

Parietal lobe

Touch, spatial awareness.

Temporal lobe

Hearing, language, memory, emotion.

Occipital lobe

Vision processing.

Meninges

Three protective membranes surrounding the CNS.

Cerebrospinal fluid (CSF)

Cushions brain/spinal cord; circulates nutrients and waste.

Ventricle

Cavity in the brain containing CSF.

Spinal cord

Connects brain to body; coordinates reflexes.

Spinal nerve

Nerve connecting spinal cord to skin/muscles.

Dorsal root

Carries sensory input to spinal cord.

Ventral root

Carries motor output to muscles.

Ganglion

Cluster of neuron cell bodies in the PNS.

Reflex action

Rapid, involuntary response to a stimulus.

Alzheimer's disease

Degenerative disorder causing memory and cognitive loss.

Parkinson's disease

Neurodegenerative disorder affecting movement control.

Neurodegenerative disorder

Progressive neuron loss leading to loss of nervous system function.