3 Introduction to Nerve and Glial cells Flashcards
Describe the Central Nervous system
Central Nervous System (CNS)
- composed of the Brain and Spinal Cord
- located in the cranial cavity and spinal cavity
Function:
- to interpret incoming sensory information and issue outgoing instructions
Describe the peripheral nervous system
Nerve fibres:
- Spinal nerves - carry impulses to and from the spinal cord
- Cranial nerves - carry impulses to and from the brain
And cell bodies outside of the CNS
- Ganglia (functions as a relay station)
Function: to conduct impulses to and from CNS
- afferent (sensory) nerves go towards CNS
- efferent (motor) nerves go away from CNS
Describe the branches of the PNS
PNS:
- Efferent (motor)
- Afferent (sensory)
Describe the branches of the Efferent (motor) nervous system
Efferent (motor): - Somatic (voluntary) - Autonomic nervous system > Parasympathetic NS > Sympathetic nervous system
Name the 2 types of nerve tissue cells
- Neuron/nerve cell
- Neuroglia
Describe a neuron/nerve cell
The structural and functional unit of nerve tissue
- Specialised to receive stimuli and conduct impulses
A neuron is composed of a cell body with processes called:
- Dendrites: receives impulses
- Axon: transmit impulses away from the cell body
Name the different types of neurons:
Neurons have different shapes reflecting differing functions:
- Motor neurons
- Sensory neurons
- Interneurons
Describe motor neurons
Motor neurons
- have a large cell body to support the axon
- and because of their numerous dendritic processes, classes as multipolar neurons
Describe sensory neurons
Sensory neurons
- commonly pseudo-unipolar
- characterised by a short process from their cell body, which later divides into a peripheral branch (conducting impulses from the receptor organ toward the cell body)
- and a central branch that continues from the cell body into the CNS
Describe interneurons
Interneurons
- Small, simple cells with short processes that provide local connection within the CNS
Discuss the histology of neurons
Neurons are highly metabolically active:
- maintenance of massive area of the cell membrane and developing electrochemical gradients
This is reflected in the histological appearance:
- Nucleus is large and rounded with a large nucleolus reflecting a high degree of transcriptional activity
- Abundance of RER for protein synthesis seen in H&E staining as blue-stained granules: Nissl substance
- Nissl substance is found in the cell body (aka perikaryon) and dendrites, but not the axon
The start of the axon (as it leaves the cell body) is called the Axon hillock
- this is where the AP is first generated
Describe neuroglia
These are the non-neuronal, non-excitable cells of the nervous system
- Their function is to support, insulate, and nourish the neurons
They are found in CNS and PNS, as different types
Name the peripheral neuroglial cells
- Schwann Cells
- Satellite cells
Describe Schwann cells
as peripheral neuroglia
Schwann Cells
- Responsible for myelinating the axons
- One Schwann cell myelinates only one axon
- Their product (myelin) can be seen in histological samples surrounding the axons and Schwann cell nucleus
Myelin is an insulating sheath wrapped around the axons
- functioning to increase the speed of conduction along axons
- NCV is increased even further with gaps called Nodes of Ranvier
Describe Satellite Cells
as peripheral neuroglia
Satellite cells
- they surround neuron cell bodies within a ganglion
- and are responsible for regulating the environment
