Neuroscience: Brain Structures, Planes, and Nervous System Functions

Neuraxis

An imaginary line through the CNS that defines orientation; differs between humans and animals

Sagittal Plane

Vertical plane dividing the body into left and right sides

Coronal (Frontal) Plane

Vertical plane dividing the body into anterior and posterior sections

Transverse (Horizontal) Plane

Horizontal plane dividing the body into upper and lower portions

Plane vs Section

A plane is an imaginary orientation; a section is an actual cut

Anterior

Toward the nose or front

Posterior

Toward the tail or back

Dorsal

Toward the back

Ventral

Toward the chest or belly

Medial

Toward the midline

Lateral

Away from the midline

Rostral

Toward the head

Caudal

Toward the feet

Ipsilateral

Same side of the body

Contralateral

Opposite side of the body

Peripheral Nervous System (PNS)

Nervous system structures outside the brain and spinal cord

Afferent Neurons

Sensory neurons that carry information toward the CNS

Efferent Neurons

Motor neurons that carry information away from the CNS

Somatic Nervous System (SNS)

Voluntary system controlling skeletal muscles

Autonomic Nervous System (ANS)

Involuntary system regulating internal organs

Sympathetic Nervous System

Fight-or-flight system; mobilizes energy

Parasympathetic Nervous System

Rest-and-digest system; conserves energy

Two-Stage Neural Pathway

ANS pathway where neurons synapse before reaching target organs

Cranial Nerves

12 pairs of nerves projecting from the brain

Central Nervous System (CNS)

Consists of the brain and spinal cord

Meninges

Three protective membranes surrounding the CNS

Dura Mater

Tough outer meningeal layer

Arachnoid Membrane

Spider-web-like middle meningeal layer

Pia Mater

Innermost meningeal layer adhering to CNS surface

Subarachnoid Space

Space containing cerebrospinal fluid and blood vessels

Cerebrospinal Fluid (CSF)

Cushions and protects the brain and spinal cord

Ventricles

Fluid-filled cavities that produce and circulate CSF

Spinal Cord

Dorsal side receives sensory input; ventral side sends motor output

Medulla Oblongata

Controls vital survival functions like breathing and heart rate

Pons

Bridge between brain regions; involved in sleep and arousal

Cerebellum

Coordinates movement, balance, and motor learning

Midbrain (Mesencephalon)

Involved in movement and sensory processing

Tectum

Contains superior (visual) and inferior (auditory) colliculi

Tegmentum

Contains reticular formation, substantia nigra, and pain regulation areas

Thalamus

Major sensory relay station of the brain

Hypothalamus

Regulates homeostasis, hormones, and the 4 Fs FLIGHT, FIGHT, FOOD, F**KING

Limbic System

Emotion, motivation, and memory system

Cerebral Cortex

Outer layer of the brain responsible for higher cognition

Frontal Lobe

Planning, decision-making, and voluntary movement

Parietal Lobe

Somatosensory processing

Temporal Lobe

Auditory processing and memory

Occipital Lobe

Visual processing

Primary Motor Cortex

Controls voluntary movements

Primary Sensory Cortex

Receives sensory input from the body

Association Cortex

Higher-order thinking, planning, and personality

Glial Cells

Support cells that nourish and protect neurons

Astrocytes

CNS glial cells that regulate environment and supply nutrients

Oligodendrocytes

CNS glial cells that form myelin

Schwann Cells

PNS glial cells that form myelin

Satellite Cells

PNS glial cells surrounding neuron cell bodies

Dendrites

Receive incoming neural signals

Soma (Cell Body)

Integrates incoming signals and maintains cell metabolism

Axon

Conducts electrical impulses away from the soma

Terminal Buttons

Release neurotransmitters into synapse

Nodes of Ranvier

Gaps in myelin enabling saltatory conduction

Resting Potential

Neuron's resting charge (~ -70 mV)

Diffusion

Movement from high to low concentration

Electrostatic Pressure

Opposite charges attract; like charges repel

Sodium-Potassium Pump

Moves 3 Na+ out and 2 K+ in to maintain resting potential

Threshold of Excitation

Minimum voltage needed to trigger an action potential

Action Potential

All-or-none electrical signal traveling down the axon

All-or-None Principle

Action potentials either fire completely or not at all

Depolarization

Sodium enters neuron making it more positive

Repolarization

Potassium exits neuron restoring resting potential

Hyperpolarization

Membrane becomes more negative than resting potential

Refractory Period

Time after firing when neuron cannot fire again

Synapse

Junction between two neurons

Presynaptic Membrane

Sending side of the synapse

Postsynaptic Membrane

Receiving side of the synapse

Synaptic Cleft

Gap between neurons at synapse

Calcium Ions (Ca2+)

Trigger neurotransmitter release

Exocytosis

Release of neurotransmitters into synaptic cleft

Postsynaptic Receptors

Bind neurotransmitters on receiving neuron

Excitatory Postsynaptic Potential (EPSP)

Increases likelihood of action potential

Inhibitory Postsynaptic Potential (IPSP)

Decreases likelihood of action potential

Temporal Summation

Signals from one synapse over time combine

Spatial Summation

Signals from multiple synapses combine

Reuptake

Neurotransmitter taken back into presynaptic neuron

Enzymatic Breakdown

Neurotransmitters chemically broken down