Nervous Tissue Flashcards
Structure of a typical neuron: Cell body
Also called: perikaryon/soma
Portion of the cell with the nucleus and other organelles (Nissl bodies-rER)
Structure of a typical neuron: Nerve fibers-Dendrite
- Unmyelinated extension from a cell body
- Receive stimulus from the environment
- Contains cytoplasmic contants
Structure of a typical neuron: Nerve fibers- Axon
- Myelinated neuronal process
- Output portion
- Contains microtubules, microfilaments, mitochondria, vesicles with proteins (NTs)
Classification of Neurons by Function: Motor-Efferent
- Conveys impules to effector cells
- Somatic-voluntary OR
- Visceral: smooth cardiac muscle
- Typically multipolar
Classification of Neurons by Function: Sensory-Afferent
- Conveys impules from receptors for integration
- Somatic: pain, temp, touch, pressure, proprioception
- Visceral: distention, ischemia, inflammation-Glands, BVs
- Typically pseudounipolar for general senses
- Bipolar special senses
Classification of Neurons by Function: Interneurons
- Communication and Integration between sensory and motor neurons (tendon reflexes)
- Multipolar
Axonal Transport definition
Bidirectional movement of material between the cell body and process
Axonal Transport Anterograde
- Towards synapse
- Kinesin
- Can be slow or fast
- Flow of synpatic vesicles, organelles
Axonal Transport: Retrograde
- FAST ONLY
- Towards the cell body
- Dynein
- Flow of recycled membrane vesicles, neuromodulators
Route used by toxins/viruses to enter the nervous system
Ganglia
Clusters of nerve cell bodies in the PNS
Sensory ganglia:
1. Carry data into the CNS
2. Location: craniospinal DRG, cranial nerves
Autonomic Ganglia
Carry data to smooth muscle, cardiac muscle, and glands
Subclasses of Sympathetic, Parasympathetic, Enteric
Sympathetic Ganglia
- Location: Prevertebral (anterior to the aorta), paravertebral (in the sympathetic chain)
- Dispersed multipolar cell bodies
- Random bundles of fibers mingled w/ soma
- Synapsing occurs BETWEEN neurons
Parasympathetic Ganglia
- Located close to organs-innervated by postsynaptic neurons
- Cell bodies clumped together
- Afferent/Efferent nerve fibers present
- Large-Euchromatic nuclei w/ prominent nucleolus
Neuroglia
Non-neuronal support cells
Fx: support, insulate, or nourish neurons
Can be found in both CNS/PNS
Schwann Cells
Myelinated neurons in PNS-ONE axon
Fx:
1. Provide support for both myelinated and unmyelinated axons
2. Clean up debris
3. Scaffolding for regeneration of nerve tissue
Satellite Cells
- Small cuboidal cells that surround cell body of neurons in PNS
- Regulated metabolic exchange
- Electrical insulator
Does NOT make myelin
Demyelinating Disease in the PNS name and key characteristics
Guillain-Barre Syndrome
1. Post-infectious peripheral polyneuropathy
2. Large accumulation of lymphoctyes, macrophages and plasma cells
3. Ascending muscle weakness and loss of coordination.
Demyelinating Disease in the CNS name and key characteristics
Multiple Sclerosis
1. Myelin is detached from the axon and destroyed (oligodendrocytes)
3 main histological stages:
1. Plaque formation-myelin breakdown causes lymphocytes and macrophages to come to infected area
2. Proliferation of astrocytes
3. Reduced cellularity, astrocytes reduce in size
What is a collection of axons in the CNS called?
Tract
What is so unique about th Perineurium?
Sheath of unique connective tissue cells called epithelioid myofibroblasts.
They have contractile propery-numerous actin microfilaments.
Restrict passage to form BNB
BNB=Blood nerve barrier
What is the Cerebrum covered by?
PIA mater
Connective tissue of the CNS-deep to superficial (3)
THINK “PAD”
1. Pia Mater: lies directly on brain and spinal cord. Interacts w/ ependymal cells to form choroid plexus. LCT
2. Arachnoid Mater LCT. Lined by back to back simple squamous epithelium. Avascular. Projects into the sinus to drain CSF into the blood stream
3. Dura Mater. DCT. Vascular. In the cranium forms the dural venous sinuses. Innervated
LCT=loose connective tissue
Astrocytes: Protoplasmic
- Prevalent in the gray matter
- Branching cytoplasmic processes
3.Maintain the blood-CSF barrier
Astrocytes: Fibrous
- Prevalent in white matter
- Straight cytoplasmic processes
Astrocytes: BOTH types
- Contain GFAP to provide structural support/strength to cells
- Maintain Blood-brain barrier
- Protect bare areas of neurons
- Support/regulate movement of metabolites/waste
Microglia
- Smallest type of central neuroglia
- Originate from blood cell line
- Phagocytic properties
- Cytoplasm contains lots of lysosomes, vesicles and inclusion bodies
Ependymal Cells
- Epithelium lining of the CNS cavaties-ventricles of the brain, central canal of the spinal cord
- Single layer of cuboidal to columnar
- Found in choroid plexus: secrete CSF
-
Well developed apical complexes: have cilia, microvilli, basal infoldings for transport, absorption, secretion
5.
Oligodendrocytes
- Myelinate axons in the CNS
- One oligodendrocyte myelinates portions of SEVERAL axons
- Larger nodes of Ranvier-increases efficiency of nerve conduction
Brain/Cerebrum: White Matter/Medulla
- Inner core of brain tissue
- Contains: Axons (tracts)-associated with glial cells, BV
Brain/Cerebrum: Gray Matter/Cerebral Cortex
- Outer layer/periphery of brain
- Site of synapses
- Contains: Cell bodies, axons, dendrites, central glial cells
- Nuclei: collection of nerve cell bodies in the CNS
What is the main cell type in the Cerebral Cortex?
Pyramidal Cells
Found in layers III, V
What are the 6 layers of the Cerbral Cortex?
- Molecular layer
- External granular layer
- External pyramidal cell layer
- Internal granular layer
- Ganglionic Layer (internal pyramidal cells)
- Multiform (polymorphic cell layer)
What are the 3 layers of the Cerebellum?
In Grey Matter
- Molecular layer (outer): stellate and basket cells
- Purkinje Cell Layer (middle): single layer of motor neurons
- Granular cell layer (inner): granule cells, type II Golgi cells
White matter: Inner core, axons forms tracts to other parts of the CNS
Cerebellar Cotex: Purkinje Cells
- Middle layer
- An apical dendrite that arborizes in the molecular layer
- Single axon that extends into the granular layer
Arborizes: branch freely
Cerebellar Cortex: Granule Cells
- Located in the innermost layer
- Project into molecular layer and connect with dendrites of Purkinje cell via parallel fibers in the molecular layer
- Carry excitatory signals to the cerebellum
Choroid Plexus
- Vascularized structure: invaginated folds of pia mater containing tufts of fenestrated capillaries
- Covered by simple cuboidal ependymal cells
- Aries from the walls of four ventricles of the brain
-
RESPONSIBLE FOR CSF production
5.
Tight junctions between the ependymal cells form what?
Blood-CSF barrier
Blood-Brain-Barrier Components and importance
Components:
1. Continuous capillaries w/ tigh junctions between endothelial cells. Continuous basal lamina. NO fenestrations
2. Foot processes of astrocytes: surround the basal lamina of the capillaries and neurons
3. Neuronal processes: mostly in contact w/ astrocytes
Spinal Cord Gray/White Matter
Gray Matter: inner core, butterfly-shaped. Cell bodies of motor neurons, dendritic and axonal prcoesses and glial cells (neuropil)
White Matter: Peripheral tissue. Unmyelinated/myelinated fibers form tracts
Where are each of the neurons present in. Bipolar? Pseudounipolar? Multipolar?
Bipolar: Special senses
Pseudounipolar: Ganglion
Multipolar: motor/interneurons
Interneurons found in CNS
