Nervous System Organization Notes

Nervous System Organization

Chapter 3: Neuroanatomy

  • Title: "It Makes Kittens and Med Students Cry"

Learning Objectives

  • Describe how neurons communicate using electrical and chemical signals.

  • Outline key functions of the frontal, parietal, temporal, and occipital lobes.

  • Describe key subcortical structures and their functions in cognition and behavior.

  • Identify major arteries supplying the brain and explain the importance of cerebral blood flow.

  • Explain the role of the spinal cord in neural communication.

A Few Helpful Tools

  • Apple/Android apps:

    • 3D Brain

    • Brain Tutor

    • Neuroanatomy - SecondLook

    • Pocket Brain

Regions of the Brain

  • Platforms: (Dr Matt & Dr Mike)

    • YouTube Channel: MATT&MIKE

    • Interactive Modules and Videos available for functional neuroanatomy

Nervous System Overview

Central Nervous System (CNS)

  • Comprises the brain and spinal cord.

  • Encased in bone.

Peripheral Nervous System (PNS)

  • Comprises nerves carrying information to and from the CNS.

  • Not encased in bone.

Nervous System Structure

Central and Peripheral Divisions

  • Autonomic Nervous System (ANS)

    • Self-regulated action of internal organs and glands.

    • Sympathetic: Arousing effects.

    • Parasympathetic: Calming effects.

  • Somatic Nervous System

    • Controls voluntary movements and sensory input.

The Brain

  • Weight: Approximately 3 lbs

  • Contains 50-100 billion neurons and 1 quadrillion connections.

  • Described as unorganized, layout often does not make logical sense (e.g., visual system located at the brain's back).

Variability in Brain Description

  • Variability between brains; differing descriptions based on structure, location, and function.

    • Example: Cortex is called the “bark” of the brain; amygdala is almond-shaped.

    • Structures may have multiple names (e.g., Auditory cortex and Heschl’s gyrus).

Cells of the Brain

Neurons

  • Functions:

    • Communication cells that respond to stimuli.

    • Capable of learning and storing environmental information.

Glial Cells

  • Type of support cell providing structural support and essential services for neuron function.

  • Three types:

    • Astrocytes: Fill gaps between neurons and regulate neurotransmitter spread.

    • Oligodendrocytes: Produce myelin.

    • Microglia: Remove cellular debris from the nervous system.

The Neuron

Main Components

  • Dendrites: Receive information from other neurons.

  • Soma (Cell Body): Contains genetic information.

  • Axon: Carries electrical impulses to transmit information.

  • Terminal Buttons: Release neurotransmitters into synaptic cleft.

Neurotransmitters

  • Chemical messengers in the body that transmit signals between neurons or between neurons and muscles.

  • Over 100 neurotransmitters identified (e.g., glutamate, GABA, dopamine, serotonin).

Neural Communication Process

  1. Neuron receives a signal from another neuron.

  2. Action potential fires, traveling down the axon.

  3. Neurotransmitters are released at the axon terminal into the synaptic cleft.

  4. Neurotransmitters cross the synaptic gap.

  5. Receptors on the next neuron receive the signal.

Brain Geography Terminology

  • Anterior: front

  • Posterior: back

  • Superior (dorsal): above or topmost

  • Inferior (ventral): below or bottommost

  • Rostral: towards the head

  • Caudal: towards the tail

  • Medial: middle

  • Lateral: outside

  • Ipsilateral: same side

  • Contralateral: opposite side

  • Afferent: movement toward CNS

  • Efferent: movement away from CNS

Brain Surface Features

  • Sulcus: A groove or “valley” in the brain's surface.

  • Gyrus: A ridge or “hill” between two sulci.

  • Fissure: A deep, prominent sulcus.

  • Tract: A bundle of axons acting as a “highway” for information between brain regions.

Hemispheric Connections

Corpus Callosum

  • A large bundle of myelinated nerve fibers connecting the two brain hemispheres, facilitating communication between right and left sides of the brain.

Major Divisions of the Brain

Forebrain

  • Diencephalon:

    • Procedural and sensory signal relay to the cortex, regulation of sleep and awareness.

    • Hypothalamus: Regulates temperature, hunger, thirst, mood, sex drive, blood pressure, and sleep.

  • Telencephalon:

    • Comprises the cerebral cortex and basal ganglia, involved in cognitive functions and movement, respectively.

  • Limbic System: Involved in emotional regulation and memory formation.

Midbrain (Mesencephalon)

  • Contains the Superior Colliculus (directs object-oriented behavior) and Inferior Colliculus (auditory processing center).

Hindbrain

  • Metencephalon:

    • Cerebellum: Coordinates movement and balance.

    • Pons: Links the brain to the spinal cord; manages unconscious processes.

  • Myelencephalon:

    • Contains the Medulla Oblongata regulating breathing, heart rate, blood pressure, and other autonomic functions.

Spinal Cord

  • Primary role: Transmits sensory information to the brain and motor commands from the brain to the body.

  • Composed of 31 pairs of spinal nerves categorized by vertebral region:

    • Cervical: 8 pairs (C1-C8)

    • Thoracic: 12 pairs (T1-T12)

    • Lumbar: 5 pairs (L1-L5)

    • Sacral: 5 pairs (S1-S5)

    • Coccygeal: 1 pair

Blood Flow to the Brain

  • Major Arteries:

    • Vertebral Arteries

    • Internal Carotid Arteries

  • Form the Circle of Willis, providing redundant blood supply—gives rise to anterior, posterior, and middle cerebral arteries.

Cranial Nerves

  • There are 12 pairs of cranial nerves that emerge from the brain and brainstem, with roles in sensory and motor function.

    • Examples:

    • Oculomotor Nerve (CN III): Eye movement.

    • Trigeminal Nerve (CN V): Facial sensations and movements.

Take Home Message

  • Neural communication amalgamates electrical signals (action potentials) and chemical messengers (neurotransmitters) to convey information.

  • Neurotransmitters are pivotal in regulating emotions, movement, learning, and mental health disorders.

  • Each brain lobe has specialized functions critical for cognition, perception, and bodily control.

  • Cranial nerves govern head and facial movements, along with sensory inputs like vision and sound.

  • The spinal cord acts as a vital communication channel between the brain and body, transmitting both sensory information to the brain and motor commands to the body.