Nervous Tissue Flashcards
Nervous Tissue
Communication, information gathering, integration, control = rapid response!
How is nervous tissue excitable?
Membrane potentials
Where does nervous tissue originate?
Neuroectodermal origin
How is nervous tissue similar to muscle tissue?
- Can be both a tissue and a cell
- Neuron = cell (axons = nerve fibers)
- Tissue = neurons + supportive tissue
Components of nervous tissue
- Endoneurium
- Perineurium
- Epineurium
Central Nervous System
- Brain: Cerebrum, Cerebellum, Brain Stem
- Spinal cord
Peripheral Nervous System
- Cranial and spinal nerves
- Ganglion (-a)
Neurons
- Sensory (afferent)
- Motor (efferent)
- Interneurons (most)
Neuron composition
- Cell body (afferent)
- Dendrites (afferent)
- Axon (efferent)
- Synaptic junction (efferent)
Supporting cells
- Schwann cells
- Satellite cells
- Glial cells
Types of Neurons
- Multipolar
- Bipolar
- Unipolar (aka psudounipolar)
Can you see nerve cells histologically?
No
Somatic
- Sensory
- Motor
Autonomic
Visceral, sympathetic, parasympathetic
- Smooth muscle (hormonal too)
- Cardiac stimulation (+/-)
- Glandular epithelium
How do you tell somatic cells from autonomic?
You cannot tell them apart histologically, but can determine which is which based on the location
Nerve cell body components
Typical of protein-producing cells
- Nucleus/nucleolus
- RER
- Nissl bodies (substance)
- Mitochondria
- Golgi
Axonal hillock
Widened trunk leading out to a neuron
- where nerve impulses originate
- where depolarization occurs
Can you see nerve cell bodies histologically?
Yes
Processes
Dendrites –> receptors
- Environment
- Other neurons
Axons –> effectors
- Other neurons
- Effector structures
Axonal transport
Neurotransmitters
- Slow vs. rapid transport
Neurotransmitters
- Formed in nerve cell body
- Kinesin: anterograde microtubules
- Dynein: retrograde mictotubules
Synapse
- Junction neuron and effector
- Chemical or electrical gap junctions
- Degradation or re-uptake
Types of neurotransmitters
- Acetyl choline
- Norepinephrine
- Epinephrine
- Dopamine
- Serotonin
- GABA
Nerves are ____
Collections of hundreds of thousands of neurons
Fascicles
- Epineurium: upon the nerves (outer layer) –> can see grossly
- Perineurium
- Endoneurium: layer right around the axon
Neuroglia
Connective tissue cells that support the nerves in the CNS
- Astrocytes, Oligodendrolgia, Microglia, Ependyma
Astrocytes
Support, modulate activity, form scar tissue in brain after damage
*principle cell type in the CNS
Oligodendroglia
Myelin
Microglia
Local phagocytes
Ependyma
Line the central canal in the brain and spinal cord
Connective cells in the PNS
- Schwann cells (make myelin)
- Satellite cells
Myelination
Provide insulation –> high lipid content, very little cytoplasm
Allows multiple axons to run in the same fascicle and not cross signals
- Schwann cells (completely wrap around the axon) and oligodendroglia
Unmyelinated fibers
- Slower conduction
- Still “invested” in Schwann cells –> Schwann cells still wrap around axons, but not in multiple layers
______ is necessary for the creation of myelin
Multiple layers of Schwann cells
Action potential
- Electrochemical depolarization
- Axonal hillock toward synapse
- Nodes of Ranvier: where a Schwann cell meets the next Schwann cell
Organization of CNS
- Gray matter vs. white matter
- Brain
- Spinal cord
Gray and white matter in the CNS
Gray: nerve cell bodies
White: axons
What are the 3 components of the brain?
- Cerebrum
- Cerebellum
- Brain stem/ medulla oblongata
Meninges
- Dura mater: just underneath the skull, tightly adhered
- Arachnoid mater: loose, web like space
- Pia mater: innermost layer, really loose connective tissue that distributes blood vessels across the brain/spinal cord
Blood brain barrier
Keeps blood off of neurons
- endothelium
- pericyte: invest connective tissue around the vessels
- astrocyte: helps to form BBB
Can you see the BBB histologically?
Hard to distinguish capillaries at a histological/ultrastructure level
Cerebrum
Higher centers
- Gray matter: outer/cortical surfaces
- White matter: central area/medulla
Gyrus
Multiple outer folds of the brain
–> gyri: one fold on the outside of the brain
Sulcus
Grooves separates right from left side of the brain
–> sulci: multiple grooves
What animals have no gyri or sulci
Avians
Cerebellum
- Coordination
- Folia
- Gray –> cortex
- White –> medulla
Molecular layer vs granular layer
Molecular: outermost layer of the cerebellum
Granular: inner layer of gray matter in the cerebellum
Purkinje fibers
Proms that extend from the molecular layer into the granular layer
–> interneurons that communicate between layers
Brain stem (medulla oblongata)
Subconscious control
- -> reptilian brain
- -> nuclei collections of nerve cell bodies
Spinal cord
Named by vertebrae
- Cortex: white matter
- Medulla: gray matter
- -> switch occurs in lower portion of the brain stem
