Cells and Tissues of the Nervous System Flashcards
What are the divisions of the nervous system?
CNS (brain and spinal cord)
PNS (cranial and spinal nerves)
What are the divisions of the PNS?
- Sensory (afferent) division
- Motor (efferent) division
What are the divisions of the motor (efferent) division?
- Somatic motor
- Autonomic
What are the divisions of the ANS?
- Sympathetic
- Parasympathetic
What are neurons?
Structural and functional units which are excitable cells
What are impulses carried as in neurons?
Action potentials
What are glial cells?
Non excitable supporting cells which are much smaller than neurons
What is the structure of a typical neuron?
Multiple dendrites with one axon
How do the impulse transmissions travel in neurons?
Impulse transmission is by action potentials which can travel in only one direction from cell body to synaptic terminal
What is found inside the nucleus of an axon?
- Loose chromatin
- Prominent nucleolus
What cell organelles are present in neurones?
- Mitochondria
- rER (Nissl bodies)
- Diffuse Golgi apparatus
What is the metabolic rate of axons?
High
What is the cytoplasm in the cell body of neurons?
Perikaryon
What is the cytoplasm in the axon of neurons?
Axoplasm
What is meant by neurons being long living and amitotic?
After development they will persist. If it dies it will not regenerate however, the axon can regrow.
What part of the neuron can grow back if damaged?
Axon
What happens if the cell body of a neuron is damaged?
The loss is irreversible
What is the function of the myelin sheath?
Increase conduction speed in axons by ‘salutatory conduction’
What is the myelin sheath formed by in the PNS?
Schwann cells
What is the myelin sheath formed by in the CNS?
Oligodendrocytes
In myelinated axons, what is formed?
Mesoaxon
What happens when Schwann cells wrap around axons?
The cytoplasm of the cell gets extruded leaving only the cell membrane
Give an example of a condition which involves demyelination.
Multiple sclerosis
What happens to the myelin sheath in MS?
Patchy loss/scarring of myelin sheath (demyelination)
What does demyelination cause?
Nerve conduction across affected axons becomes abnormal
What is the cause of MS?
Cause is unknown
May be linked to autoimmunity or viral illness
What can be seen on MRI of MS?
Whitish plaques of demyelination
What country has the highest prevalence of MS in the world?
Scotland
What is the prognosis of MS?
Variable
What types of neuron are there?
- Multipolar
- Bipolar
- Pseudounipolar