W1: Fundamentals of Nervous Tissue Flashcards
Central Nervous System (CNS)
The command center consisting of the brain and spinal cord. It receives sensory signals, interprets them, and dictates motor responses.
Peripheral Nervous System (PNS)
Nervous system outside of the CNS. Consists of nerves extending outside of the brain and spinal column.
Afferent Neurons
Have axons that carry information toward the CNS.
Efferent Neurons
Have axons that carry information away from the CNS.
Interneurons
Neurons that connect to other neurons within the same general area (i.e. spinal cord)
Somatic Motor Neurons
(Voluntary) innervation to skeletal muscle.
Somatic Sensory Neurons
CNS > Skeletal muscles. Touch, pain, pressure, vibration, temperature, proprioception from skin, body wall, and limbs. Special: Hearing, equilibrium, hearing.
Visceral Motor Neurons
(Involuntary - ANS) Innervation to smooth & cardiac muscle and glands.
Visceral Sensory Neurons
CNS > Smooth, cardiac muscles and glands. Stretch, pain, temperature, chemical changes, irritation of viscera, nausea and hunger. Special: Taste and smell.
General Characteristics of a Neuron:
- excitable cells
- do NOT divide after birth, but some neurogenesis from adult stem cells.
- Normally live a long life
- High metabolic rate - require large amounts of glucose and oxygen.
- Have 2 types of processes (dendrites/receivers & axons/senders)
Proprioception
Sensing one’s own body.
What structures make up the soma/cell body?
- Plasma membrane
- Nucleus/nucleolus
- Nissl bodies/rough ER
- Golgi Apparatus
- Neurofilaments
Dendrites
Intermediate filaments that provide structural integrity. They receive synapic contact from other neurons. Types: Multipolar & bipolar.
Dendritic Spines
Enlarge the surface area of the plasma membrane
Axon
Cell signaling between neurons.
Axon Hillock
Where the axon tappers from the cell body; site where action potentials are generated. (Decision Maker)
Axonal Neurotubules
Parallel arrays of processes that help axon retain shape.
Axon Collateral
Sideways branches off of an axon.
Axonal Transport
- Anterograde
2. Retrograde
Anterograde Axonal Transport
Tracer: Phaseolus vulgaris (Phal), Biotinylated DextranAmine (BDA), Triated Amino Acids (H^3 amino acids)
Injection of tracer into CNS and taken up by cell bodies then transported down the axon. Tracer accumulates in axon terminals labeling terminal boutons. Tells you which regions of the CNS receive neuron projections.
Retrograde Axonal Transport
Tracer: Horseradish Peroxidase (HRP)
Injection of tracer into the CNS and taken up by terminals and transported back to the cell body. This labels which cell bodies that project to the area of of your injection site.
Types of Synapses:
- Axosomatic synapses
- Axoaxonic synapses (axon-axon)
- Axodendritic synapses
Where do synapses occur?
Between an axon terminal and a postsynaptic structure.
What are the primary structures of an axon terminal?
- Presynaptic terminal
- Synaptic Cleft
- Postsynaptic terminal
Information flow in neurons…
is ALWAYS in one direction.
Excitatory Neurotransmitter causes:
target neuron to depolarize and fire.
Inhibitory Neurotransmitter causes:
target neuron to hyperpolarize and NOT fire.
What postsynaptic elements can axon terminals form synapses with?
- axosomatic
- axodendritic/axospinous
- axoaxonic
How do you identify the different types of synapses?
Electronmicroscope
What is the neurotranmitter for any neuromuscular junction?
acetylcholine
Characteristics of glial/supporting cells and how they differ from neurons:
- Can divide throughout life
- Have only one type of process (rather than two)
- Each type of glia has specific functions that support neurons.
- Smaller in size and have darker staining nuclei.
- Different kinds of glia in CNS and PNS.
Types of Glial/Supporting cells in the CNS:
- Astrocytes
- Oligodendroglia
- Microglia
- Ependymal Cells
Astrocyte
“Star”
- Glia
- Cause tumors in the brain
- They control the environment surrounding the neuron by metabolizing and recylcing neurotransmitters.
- Release growth factors
- Promote neural survival
Oligodendroglia
“Few”
- Myelin generating glia
- Degradation causes MS
- They line axons and wrap think axons to form myelin in CNS
- Speed up action potentials (insulators)
- Can degrade over lifetime
- Can wrap many axons at once
Microglia
“Small”
- Glia
- Immune system cell in CNS
- Act as phagocytes by removing debris
- hard to find in healthy brains but divide and multiply quickly in sick brains
Ependymal Cell
- NOT glia
- Found in only one place = lining of neural tube
- Divide CNS and fluid of ventricular tissue
Supporting cells of the PNS
- Schwann Cells
- Nodes of Ravier
- Myelin from Schwann cells
Schwann Cell
- Myelin generating glia
- increase speed of action potentials
- surround large axons 6-10 times with lipoprotein
Node of Ranvier
- Space of exposed axon between myelin
- current jumps between nodes to increase action potential speed
Features of a nerve:
- Axons
- Myelin Sheaths
- Fascicle
- Blood vessels
What types of nerves are considered peripheral nerves?
- Collection of axons traveling together
- Motor, sensory, and mixed nerves
- Nerve fascicles covered in layers of connective tissue
Golgi Stain
- Inconsistent
- Best way to show full neuron
- Works well to study neurons in development but not on myelinated cells
- Soak in potassium dichromate then silver nitrate
- Good for comparative, classification, and developmental studies
Nissl Stain
-Basic stain that differentiates gray matter easily
-High pH stain; attracted to nucleic acids of nucleus and rough ER.
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Immunocytochemistry
Anatomical technique used to characterize the presence of chemicals in cells.
-The rate limiting synthesizing enzyme indicates the appropriate neurotransmitter made by a cell.
ChAT
Choline acetyltransferase
=the sunthesizing enzyme
Acetylcholine
major excitatory neurotransmitter at both CNS synapses and neuromuscular junctions.
Acetyl Cholinesterase
enzyme that degrades the neurotransmitter in the synaptic cleft.
