Flashcards in Lecture 7 - Nervous Tissue Deck (60):
How many neurons do you have at birth?
What are the two parts of the nervous system?
CNS - Brain, Spinal Cord
PNS - Outside of dura mater
Collections of nerve cell bodies outside of the CNS (surrounded by satellite cells
Two types of ganglia
Dorsal root ganglia - sensory (afferent nerves)
Sympathetic ganglia - cell bodies of the sympathetic nerves
Afferent (sensory) nerves
Convey impulses to CNS
Efferent (motor) nerves
Convey impulses away from CNS
What two types of cells do nerve tissue contain?
Supporting cells and Neurons
protection, insultation repair, metabolic exchange, clearance of neurotransmitters, maintenance of fuild environment in CNS (there are many types that belong only in CNS or PNS)
functional unit; receive stimuli and conduct impulses (nothing else!)
What are the four types of glial cells? (Unique to CNS)
myelination of CNS (myelinate multiple processes). Similar to Schwann cells, but this one does NOT form sheath. Oligodendrocytes are also bigger and reach out to multiple axons, while Schwann cells line one axon each.
important for blood-brain barrier, involved in physical and metabolic support (provide nutrients and remove wastes); star-shaped
Phagocytotic (formed in bone marrow)
What are the two supportive cells unique to PNS?
1. Schwann cells
2. Satellite cells
myelinate a single process, or protect several w/out myelinating. Associated with nerve fibers. Involved in regeneration of injured nerves.
associated w/ ganglia (protect, provide nutrition, insulate)
What are the three classifications of nerve cells?
Classified based on the number of processes extending from the cell body
A. Bipolar Neurons
B. Multipolar Neurons
C. Pseudounipolar Neurons
one axon + one dendrite
-Not very common; present only in special sensory organs
Ex. Olfactory neurons, retina, neurons in spiral ganglion of inner ear
one axon + two or more dendrites
-Most neurons, including motor neurons in the spinal cord
-Dendrite is receptor portion of cell and axon is the conducting portion.
one axon/process that branches into axon and dendrite, to transmit and receive signal, respectively
-They are the primary sensory neurons, found in dorsal root ganglion
Characteristics of the cell body.
contains nucleus and most of cytoplasm; is receptive to stimuli.
Characteristics of a protein-producing cell
- Pale nucleus and distinct nucleolus – lots of euchromatin, active transcription
- Lots of rER; appear as clumps under LM and most abundant in large motor neurons
- Well-developed Golgi (stays around nucleus), lots of mitochondria
start of axon, “empty space” looking under LM; is mainly free of large cytoplasmic organelles but mitochondria may move into axon.
patches of ribosomes and rER (LM – dark bodies)
Short, elongated processes that receive impulses from the periphery (i.e. other neurons) and transmit them toward the cell body. They are Receptor Processes.
Difference between dendrite and axon
Have greater diameter than axons, but are hard to differentiate from axons.
single effector process that transmit stimuli; originates from axon hillock (pyramidal-shaped area)
are microtubules that form railroad tracks. Can transport mitochondria which gives energy to nerves far away from cell body
are intermediate filaments composed of three intertwining polypoeptide chains; run throughout the soma cytoplasm and axon
Away from perikaryon, driven by kinesin (slow and fast)
Towards perikaryon, driven by dynein (one speed, moved endocytosed materials)
Slow Anterograde Transport
Structural elements, tubulin and actin molecules, cytoplasmic proteins
Fast Anterograde Transport
Neurotransmitters, synaptic vesicles, mitochondria, nutrients
What structures are involved in relocation of virus from the cell body to distal nerve processes?
KINESIN! Microtubule-associated motor protein that allows substances to move within axon away from cell body! Neurofilaments are more structural and actin is a microfilament-associated motor protein.
neuromuscular junction aka motor end plate
nerve and muscle fibers that the neuron innervates
Peripheral Nerves are composed of:
-Nerve Processes (axon and dendrites)
-Supporting cells (Schwann cells)
-Fibroblasts (producing connective tissue fibers; Schwann cells can also produce CT)
-Blood Vessels (vasa nervosa)
Where are the cell bodies of the peripheral nerves?
Spinal cord (motor nerves)
Dorsal root ganglia (sensory nerves)
external connective tissue (dense irregular CT). Also fills space between bundles of nerve fibers.
specialized CT that surrounds nerve fasicles, blood-nerve barrier. Consists of flattened epithelial-like cells that possess contractile elements (actin)
loose CT that covers Schwann cell-covered nerve fibers
Made by Schwann cells in PNS, lipid-rich layer which insulate and protect axons or dendrites from the extracellular space. Schwann cell wrap around ONE nerve process when forming myelin sheath.
regulates the thickness of the myelin sheath.
What determines thickness of the myelin sheath?
Amount of Ngr1
What is myelin made of?
Compact myelin and transmembrane myelin-specific proteins (80% lipid and 20% protein)
Nodes of Ranvier
spaces between Schwann cells that expose axolema
What are in axolema
Lots of ion concentration channels
Propagation of action potential along myelinated axons between nodes of Ranvier. Depolarization at one end of the node of Ranvier cause an action potential in the adjacent node and so on.
What are unmyelinated axons covered in?
Simple clefts of the Schwann cell (either open, exposing axolemma, or closed, forming a mesaxon)
What type of stain do you use to see a synapse?
carries impulse to synapse
At the end of an axon where neurotransmitters are released. Characterized by presence of synaptic vesicles that contain neurotransmitters
An ATP-binding protein found on the membrane of synaptic vesicles; required for formation, targeting, and fusion of vesicles with the presynaptic membrane
small mitochondria and other things near plasma membrane.
Two theories of how vesicles release neurotransmitters:
1. Excitatory Neurotransmitters: stimulate propagation of impulse, open ligand-gated Na+ channel produces postsynaptic membrane depolarization (excitatory postsynaptic potential; EPSP)
-Ex. Acetylcholine (Ach), glutamate, serotonin, norepinephrine, dopamine, nitric oxide (NO)
2. Inhibitory Neurotransmitters: React w/ receptors to open ligand-gated Cl- channels produces hyperpolarization of post synaptic membrane (inhibitory postsynaptic potential; IPSP) suppresses nerve firing. -Ex. Glycine, GABA
Skeletal muscle paralysis from botulism is due to..?
Toxin forming barrier to the release of acetylcholine at PRESYNAPTIC membrane of motor nerve terminals
glial cells + nerve cell bodies