Nervous Tissue Flashcards
What are the 2 parts of the nervous system from an anatomical perspective and from a histological perspective?
Anatomically:
CNS → Brain, Cerebellum, Spinal cord (Gray and white matter)
PNS → Nerve Ganglia, Nerve Fibers
Histologically:
Neurons (Nerve cells)
Neuroglial → Glial cells equivalent to the CT; involved in support, neuron protection, defense and nutrition
What is the gray and white matter of the CNS composed of?
Gray matter → Cell bodies of neurons, neuroglia
White matter → Neuronal processes (axons), Neuroglia
What is the functional unit of the nervous system?
Neuron
What are the 3 main structures of the neuron?
- Dendrites
- Receive signals - Cell Body
- Integrates incoming signals from dendrites
- And outgoing signals to axons - Axons
- Transmits signal to another neuron or effector cell
WHat are 2 alternate names for the cell body of a neuron?
Soma
Perikaryon
What are the different ultrastructures of the cell of body of a typical neuron?
- Lysosomes
- Lipofuscin Body
- Centrally located nucleus (with a prominent nucleolus)
- Nissl bodies (free RER and free ribosomes) at the entries of the dendrites, but not of the axon!
- Axon Hillock (no Nissl Bodies)
- Mitochondria
*Axon and dendrites have Intermediate filaments (Neurofilaments) and Microtubules
What are different types of neurons based on their morphology?
What are multipolar neurons?
- Pyramidal cells (brain cortex)
- Purkinje (Cerebellum)
- Motor Neurons (Spinal cord)
- Pseudo Unipolar (Spinal Ganglia)
- Bipolar (Retina, Olfactory Mucosa)
*Multipolar neurons have more than 2 processes
What shapes can take the perikaryons?
- Spherical
- Ovoid
- Angular
What are the 3 main structures of the CNS?
Ant their functions?
- Cerebrum → integration of sensory information (from PNS) + Initiation of voluntary motor responses
- Cerebellum → Intergation of sensory information (from PNS) + Fine-tuning of voluntary motor responses
- Spinal Cord:
- Relay messages from brain to body
- Pass sensory information from sensory receptors to the brain
- Coordinate reflexes that are managed by the spinal cord alone (patellar/knee jerk reflex)
What is the difference between gray and white matter?
Gray matter → contains neuronal cell bodies and neurglial cells
White matter → contains acons and neurglial cells
- appears white due to the presence of myelin around the axons
Spine = gray inside/white outside
Cerebellum = white inside/gray outside
Cerebrum = white inside/gray outside
What is the histology of the cerebrum like?
White + Gray matter
Gray matter:
- 6 layers in the cerebral cortex
- Pyramidal neurons are the most prominent (arranged in parallel with on another + larger than surrounding glial cells)
What is the histology of the cerebellum like?
The gray matter has 3 layers:
1. Molecular Layer:
- Sparse neurons
2. Purkinje Layer:
- Very large purkinje neurons
- Dendrites project → molecular layer + Axons project → granular layer
3. Granular Layer:
- Very small, densly packed neurons
- Axons are unmyelinated, project into molecular layer where they synapse with dendrites of purkinje cells
What are the different subdivision of the PNS?
Somatic PNS:
- Sensory nerve fibers → CNS (afferent)
- Motor nerve fibers ← CNS (efferent)
Autonomic PNS:
- Controles smooth muscle of the internal organs and glands
*Sensory and Autonomic neurons have their cell bodies in ganglia. Neuron cell bodies of motor neurons are located in the spinal cord
Which cells are responsible for axon myelination in the CNS vs PNS?
CNS → Oligodendrocytes
- Multiple axons for 1 oligodendrocyte
PNS → Schwann cells
- 1 Schwann: 1 axon
Functions of myelination → electric insulation + faster condution of nerve impulse
*Myelin makes the white in white matter
What are Nodes of Ranvier?
Gaps in the myelin sheath that promote transmission of the action potential
