Neuroanatomy and Neuronal Communication Study Notes

INTRODUCTORY PSYCHOLOGY NOTES

LAST CLASS

• Covered topics:

  • Research methods

  • Central tendency

  • Normal distribution

TODAY'S FOCUS

• Biological bases of behaviour

• Neuroanatomy

• Overall structure of the brain

• Hemispheres

• Gyri & Sulci

• Gray matter & White matter

• Ventricles

• Cell types in the brain

• Neurons & Neurotransmission

NEUROANATOMY

THE NERVOUS SYSTEM

• Divisions:

  • Central Nervous System (CNS)

  • Peripheral Nervous System (PNS)

Peripheral Nervous System (PNS)

• Comprises all nerves outside the brain and spinal cord.

• Responsible for interactions with the external environment and executing motor commands.

Central Nervous System (CNS)

• Comprises the brain and spinal cord.

• PNS consists of nerves outside these regions.

• Many terms for brain regions come from embryology.

BRAIN DEVELOPMENT

• Textbook terms: Forebrain, Midbrain, Hindbrain.

• Embryology: The study of development from fertilization to birth/hatching.

• Confusing/poor descriptors stemming from embryological brain development to adult neuroscience.

EMBRYONIC BRAIN REGIONS

• 1 month embryo:

  • Midbrain

  • Hindbrain

  • Forebrain

• 5 weeks embryo:

  • Mesencephalon (Midbrain)

  • Metencephalon (Hindbrain)

  • Diencephalon (Forebrain)

  • Myelencephalon (Hindbrain)

  • Telencephalon (Forebrain)

  • Spinal cord

NEURODEVELOPMENT

• Sutures: Ossified tissue between skull plates; allow passage through the birth canal and solidify with age.

BENEATH THE SKULL

• Meninges: Layers of protective tissue below the skull

  • Dura mater

  • Arachnoid mater

  • Pia mater

• Subarachnoid space: Filled with cerebrospinal fluid.

VENTRICLES

• Cerebrospinal fluid (CSF): Clear fluid that surrounds brain and spinal cord, providing protection, nutrients, and waste removal.

• Ventricles: Fluid-filled cavities in the brain that produce and circulate CSF.

THE CEREBRUM

GENERAL STRUCTURE

• Known as telencephalon, makes up the visible surface of the brain.

• Primary Cortices: Located in gyri, responsible for cognition, especially perception and higher mental functions.

GYRI AND SULCI

• Cerebrum is not smooth; has gyri (ridges) and sulci (depressions/fissures).

• Sulcus (pl. Sulci): Depression or fissure in brain surface.

• Gyrus (pl. Gyri): Ridge on brain surface.

LANDMARK SULCI AND GYRI

• Central sulcus: Separates frontal and parietal lobes.

• Sylvian fissure (lateral sulcus): Separates temporal lobes.

LOBES OF THE CEREBRUM

• Frontal Lobe: Executive function, decision making, and problem-solving.

• Temporal Lobe: Auditory information, language processing.

• Parietal Lobe: Sensory processing, spatial awareness.

• Occipital Lobe: Visual processing, pattern, and color recognition.

HEMISPHERES

• Longitudinal Fissure: Separates left and right hemispheres.

• Corpus Callosum: Connects the two hemispheres.

• Commissures: Structures connecting the hemispheres.

IMPORTANT BRAIN REGIONS

• Thalamic Regions: Thalamus and hypothalamus.

  • Thalamus: Relays sensory signals to respective cortices.

  • Hypothalamus: Regulates basic biological needs and hormone secretion.

LIMBIC SYSTEM

UNDERNEATH THE CEREBRUM

• Hippocampus: Critical for the formation and consolidation of new memories, especially declarative or episodic memories.

• Amygdala: Central in processing emotions, notably fear, and emotional memories.

• Part of the Limbic System.

THE CEREBELLUM

• Posterior portion of the brain.

• Coordinates fine movement and balance, consists of deeply folded structure.

CELL TYPES IN THE BRAIN

NEURONS

• Neurons: Specialized cells transmitting electrical and chemical signals, enabling communication within the brain and body.

  • Major parts:

  • Soma (cell body)

  • Nucleus

  • Membrane

NEURONAL STRUCTURE

• Soma: Contains nucleus and organelles, serves as a manufacturing site for proteins and neurotransmitters.

• Nucleus: Contains genetic material.

• Membrane: Lipid bilayer controlling ion flow and signal reception.

• Specialized parts:

  • Axons

  • Dendrites

  • Myelin sheath

  • Axon terminals

DENDRITES

• Gather information from other cells.

• Branch out to increase neuron surface area.

• Dendritic Spines: Small structures on dendrites, serve as receiving points for chemicals from other neurons.

AXONS

• Transmit electrical signals away from the cell body.

• Only one axon per neuron.

• Axon terminals located at the end of the axon.

MYELIN SHEATH

• Coats neuronal axons, derived from glial cells.

• Insulates axons, speeding up action potentials.

• Degeneration leads to multiple sclerosis (MS).

NODES OF RANVIER

• Gaps in myelin sheath that are regularly spaced.

NEURONAL ELECTRICAL PROCESSES

RESTING POTENTIAL

• Baseline electrical charge of a neuron when at rest; approximately -70 millivolts.

MAINTENANCE

• Maintained by:

  • Ion Channels: Allow specific ions to pass through cell membrane.

  • Sodium-Potassium Pump: Actively transports sodium out and potassium into neurons.

ACTION POTENTIAL

• Brief shift in neuron's electrical charge that travels along the axon.

• Charge changes from about -70mv to +30mv.

PROPAGATION

• Begins near soma and rapidly propagates down the axon, aided by myelin.

ALL-OR-NONE LAW

• Describes action potentials' nature; once triggered, they are fully executed.

• No partial action potentials.

INTENSITY CODING

• Intensity of stimulus encoded by the rate of action potentials: faster firing indicates more intense stimuli.

REFRACTORY PERIOD

• Absolute refractory period: A time after an action potential during which another cannot begin.

NEURONAL COMMUNICATION

SYNAPSES

• Neurons connect at synapses.

• Pre-synaptic neuron: Sends the signal.

• Post-synaptic neuron: Receives the signal.

• Synapse: Junction allowing transfer of electrochemical signals.

SYNAPTIC GAP

• Space between pre-synaptic and post-synaptic neurons where chemical communication occurs.