Neuroanatomy

Overview of the Nervous System

• mediates a wide range of functions

  • detection of environmental stimuli

  • control of muscle contraction

  • problem solving

  • language

  • memory

• divided into 2 parts

  • central = brain and spinal cord

  • peripheral = everything else

Functional Divisions of the Nervous System

Central Nervous System

• brain

• spinal cord

Peripheral Nervous System

• ganglia: communication of brain and peripheral

• cranial and spinal nerves

Somatic Division

• sensory neurons = sensory information form skin, skeletal muscles, and joints to CNS

• motor neurons = motor impulses from CNS to skeletal muscles 

Autonomic Division

• sensory neurons = sensory information from visceral organs to CNS

  • regulate body system

  • area where drugs manipulate things

• motor neurons = motor impulses from CNS to smooth muscle, cardiac muscle, and glands

Enteric Division

• tummy

Central Nervous System (CNS)

• brain enclosed within cranial cavity

  • protected by cranium and meninges

  • has 3 main regions:

    • cerebrum: 2 hemispheres (right and left); receives sensory information and generate outgoing motor information; site of executive and cognitive function

    • brainstem: contains medulla, pons, and midbrain; connects cerebruma nd cerebellum to spinal cord relaying information; regulate vital functions (CV regulation, breathing, consciousness)

    • cerebellum: involved in control and coordination of movement

  • highly vascularized

    • blood brain barrier

  • contain ventricles

    • ventricles: network of interconnected fluid-filled cavities

      • choroid plexus produces cerebrospinal fluid (CSF)

  • focus on 5 lobes:

    • frontal lobe → voluntary motor control, production of language, short-term working memory, attention, behavioral control, and executive functions

    • temporal lobe → receives and processes and olfactory information, processing to establish face recognition; interpreting visual stimuli

    • parietal lobe → contains somatosensory cortex; receives and processes touch, temperature, pain, and conscious proprioceptive information from the body; some motor control

    • occipital lobe → contains visual cortex; involved in visual reception, visual-spatial processing, motion perception, and color recognition

    • cerebellum → coordinates smooth and precise and balanced movements; regulates posture, gait, and fine motor skills; maintains balance

• spinal cord

  • emerges from the brain stem

    • relay between brain and peripheral nerves

  • sits within the spinal canal and is protected by the vertebral column and meninges

  • compromised of white and gray matter

    • white = nerve tracts and glia

      • contains ascending sensory and descending motor tracts

    • gray = neuronal cell bodies, dendrites, and glia

      • sensory information carried by afferent axons of spinal nerves

Peripheral Nervous System

• compromised of ganglia and nerves

  • both ganglia and nerves transport information from the periphery to the brain and from the brain to the periphery

    • ganglia: clusters of functionally related neuronal cell bodies

    • nerves: bundles of axons ensheathed in connective tissue that innervate all parts of the body

Peripheral Nerves

Cranial Nerves

• 12 pairs total

  • 10 are part of peripheral nervous system

    • neuronal nerve nuclei located in brain stem and travel outside the CNS

  • 2 remain in the CNS (nuclei and nerves)

  • some are mixed nerves → contain both motor efferents and sensory afferents and both somatic and autonomic componenets

    • afferent = sensory neurons carry signal to the brain

    • efferent = motor neurons carry signal away from the brain

Spinal Nerves

• 31 pairs

  • emerge from the spinal cord and named for the spinal cord segment from which they connect

  • mixed nerves

Autonomic Nervous System

• unconscious/involuntary control of cardiac muscle, smooth muscle, and glands

• “visceral” sensory system: provides information from the viscera, internal organs, and vasculature

• divided into sympathetic (fight or flight) and parasympathetic (rest and digest)

• uses 2 neuron chain model

Somatic Nervous System

• mediates conscious/voluntary movement

• regulates skeletal muscle contraction

• provides sensory information from skin, muscles, and joints

• uses 1 motor neuron from CNS to skeletal muscle

  • signals at a neuromuscular junction to generate muscle contraction

Enteric Nervous System

• governs GI system under involuntary control and functions independently

• receives significant input from autonomic nervous system

Cellular Components of Nervous System

CNS

Neurons

• signaling cells that transmit electrical and chemical signals

• most are excitable → generation of action potential

• morphologically:

  • extend axons to send information

  • dendrites/dendritic spines receive information

  • synapse = site of information relay

• classification:

  • sensory, motor, and interneurons

Glia

• gray matter = astrocytes, microglia, oligodendrocytes

  • astrocytes: help form blood-brain barrier; regulates interstitial fluid composition; provide structural support to CNS; assists with neuronal development; replicate to occupy space of dying neurons

• gray matter adjacent = ependymal cells

  • ependymal cells: line ventricles of brain and central canal of spinal cord; assist in production of CSF

• white matter = oligodendrocytes, astrocytes, microglia

  • microglia: phagocytic cells that move throughout CNS; engulf infectious agent and other harmful substances

PNS

• satellite cell: electrically insulates PNS cell bodies; regulate nutrient and wast exchange for cell bodies

• schwann cell: surround and insulate PNS axons and myelinated those with large diameters; allows for faster AP propagation along axon in the PNS