Nervous Tissue and Neuron Anatomy Study Notes

Nervous Tissue & Neuron Anatomy

Lab Overview

  • Course: BSC2085L - Anatomy and Physiology I Lab

Study Tips

  • Start Early: Begin studying as soon as possible; the material is comprehensive and needs ample time for understanding.
  • Utilize Study Guides and Flashcards: Active engagement with guides and flashcards for key concepts enhances memory reinforcement.
  • Stay Organized: Track assignment due dates, lab notes, diagrams, and exercises to reduce exam preparation stress.
  • Practice Regularly: Implement regular quizzes and review sessions to solidify understanding.
  • Seek Help When Needed: Ask questions and seek clarification from instructors, peers, or tutors for complex concepts.
  • Manage Time Effectively: Allocate 2-3 hours daily for assignments and studying with breaks for repetition, which is key for memorization.
  • Review Medical Terminology: Familiarity with medical terminology is essential for understanding anatomy and physiology.

Nervous Tissue

  • Division of the Nervous System:
    • Central Nervous System (CNS): Includes the brain and spinal cord.
    • Peripheral Nervous System (PNS): Comprises peripheral nerves that innervate skin, muscles, and visceral organs.
    • Function of Nervous Tissue: Composed of neurons that send electrical signals for muscle innervation and sensory communication.

Central Nervous System (CNS)

  • Components:
    • Brain
    • Spinal Cord
  • Brain Structure: Divided into hemispheres and lobes with functional areas including:
    • Diencephalon
    • Brainstem
    • Cerebellum
  • Functional Determinants: The structure’s location influences its function.

Neurons and Neuroglia

Major Cell Types in Nervous Tissue

  • Neuroglia (Support Cells):
    • Astrocytes: Regulate electrical impulses, supply nutrients, and form scar tissue post-injury.
    • Oligodendrocytes: Produce myelin in the CNS.
    • Ependymal Cells: Line brain ventricles, produce, and circulate cerebrospinal fluid (CSF).
    • Microglia: Act as macrophages to clean up debris and pathogens.
    • Schwann Cells: Form myelin sheaths in the PNS.
Neuron Types
  • Neurons (Nerve Cells):
    • Functions:
    • Receive Stimuli: Gather sensory information (visual, auditory, olfactory, etc.).
    • Conduct Impulses: Initiate action by innervating muscles to contract.

Structure of Neurons

Components of Neurons

  • Cell Body (Perikaryon):
    • Typically located in the CNS, forming gray matter; also found in ganglia of the PNS.
    • Components:
    • Nucleus: Contains DNA and nucleolus for ribosome production.
    • Neuroplasm: Cytoplasm of the neuron.
    • Neurofibrils: Cytoskeleton components.
    • Nissl Bodies: Rough endoplasmic reticulum for protein synthesis.
    • Smooth ER: Functions in detoxification, storing Ca²⁺, and lipid production.
    • Mitochondria: Energy production via ATP synthesis.
    • Lysosomes: Digestive enzymes for cellular waste breakdown.
Anatomical Details
  • Dendrites: Receive incoming signals, act as recipient branches of neurons.
  • Axon: Generates and transmits nerve impulses.
  • Axon Hillock: Site just distal to the cell body where action potentials are generated.
  • Axon Terminals: Release neurotransmitters at synapses.
  • Myelin Sheath: Insulating layer on long neurons increasing impulse speed.
  • Nodes of Ranvier: Gaps in myelin sheath allowing ion exchange, enhancing impulse speed.
  • Endoneurium: Protective layer around the axon.

Spinal Cord Anatomy

  • Types of Neurons:
    • Sensory Neurons: Convey sensory information.
    • Motor Neurons: Relay impulses to muscles.
  • White Matter: Contains myelinated axons.
  • Gray Matter: Contains unmyelinated axons and cell bodies.
    • Horns:
    • Ventral (anterior) Horn: Houses motor neuron cell bodies.
    • Dorsal (posterior) Horn: Houses sensory neuron cell bodies.

Gray Commissure and Central Canal

  • Central Canal: Circulates CSF; connects gray matter sides.
  • Dorsal Roots: Contain sensory fibers and interneurons.
  • Dorsal Root Ganglion: Collection of sensory neuron cell bodies.
  • Ventral Roots: Comprise motor neurons.

Reflexes and Reflex Arcs

  • Definition: Rapid involuntary motor responses to stimuli; often subconscious.
  • Categories:
    • Autonomic Reflexes: Involve autonomic nervous system, activating smooth/cardiac muscles and glands.
    • Somatic Reflexes: Involve skeletal muscles.
  • Examples:
    • Patellar Reflex
    • Achilles Reflex
    • Plantar Reflex

Components of a Reflex Arc

  1. Receptor: Site of stimulus detection.
  2. Sensory Neuron: Transmits afferent impulses to the CNS.
  3. Integration Center: Comprises one or more CNS neurons.
  4. Motor Neuron: Conducts efferent impulses.
  5. Effector: Responds to impulses (muscles or glands).
Steps in a Simple Neural Reflex
  1. Stimulation of a Receptor: Activates pain receptors.
  2. Activation of a Sensory Neuron: Dendrites generate graded polarization leading to action potentials.
  3. Information Processing in CNS: Sensory neuron releases neurotransmitters at interneuron synapse, creating excitatory postsynaptic potential (EPSP).
  4. Activation of Motor Neuron: Stimulation leads to action potentials carried to effector.
  5. Response of Peripheral Effector: Effector (muscle) contracts to remove stimulus.

Brain Anatomy

Main Brain Regions

  • Cerebrum: Responsible for higher functions (sight, emotion, memory).
  • Diencephalon: Contains thalamus, hypothalamus, and pituitary gland; regulates hormone production.
  • Brain Stem: Comprises midbrain, pons, and medulla oblongata; controls basic involuntary functions.
Diencephalon Components
  • Thalamus: Major sensory integration center, regulates consciousness and sleep.
  • Hypothalamus: Controls autonomic functions (thirst, hunger, temperature).
  • Pituitary Gland: Hormonal control center.
  • Pineal Gland: Produces melatonin; regulates circadian rhythms.
Brain Stem Functions
  • Midbrain: Controls vision and hearing, regulates temperature.
  • Pons: Relays information between cerebrum and cerebellum.
  • Medulla Oblongata: Manages involuntary functions (blood pressure, heart rate).

Categories of Cranial Nerves

  1. Olfactory (I): Sensory (smell).
  2. Optic (II): Sensory (vision).
  3. Oculomotor (III): Motor (eye muscles).
  4. Trochlear (IV): Motor (eye muscles).
  5. Trigeminal (V): Mixed (sensory to face/motor for chewing).
  6. Abducens (VI): Motor (eye muscles).
  7. Facial (VII): Mixed (facial expression/taste).
  8. Vestibulocochlear (VIII): Sensory (hearing/balance).
  9. Glossopharyngeal (IX): Mixed (swallowing/blood pressure monitoring).
  10. Vagus (X): Mixed (organ sensation, heart rate control).
  11. Accessory (XI): Motor (neck movement).
  12. Hypoglossal (XII): Motor (tongue movements).