Nerve Practical Flashcards
What are the components of a typical nerve cell
Nerve cell body, dendrites, Schwann cell, node of Ranvier, nerve cell nucleus
What is epineurium
A connective tissue sheath that surrounds each nerve
What is perineurium
Each bundle of nerve fibres is called a fasicle which is surrounded by a layer of perineurium
What is endoneurium
Within the fasicle each individual nerve fibre is surrounded by connective tissue called the endoneurium
What are the main functions of the connective tissue dheaths
Support and protection
What are the key differences between a sensory and effector (motor) nerve endings
Motor neurones- multipolar; sensory neurones- unipolar. Sensory neurones are situated in the DRG of the spinal nerve; motor neurones are situated in the ventral root ganglion of the spinal cord. Sensory neurones follow afferent pathways while motor meurones follow efferent pathways. Adult- 10 million sensory but 500,000 motor neurones. Sensory neurone has afferent fibre, motor neurone has efferent fibre
High magnification light microscopic image of a ‘multipolar efferent motor neuron, the surrounding neuroglia and axons in the anterior horn of the spinal cord’.
Why does the cytoplasm of the cell body appear granular
Nissl granules represent masses of ribosomes and rough ER
High magnification light microscopic image of a ‘multipolar efferent motor neuron, the surrounding neuroglia and axons in the anterior horn of the spinal cord’.
What are the filaments in the cytoplasm axons
Neurofibrils
What are glial cells and what is their function in the spinal cord
The CNS consists of neurones and glial cells. Half the violume of the CNS are glial cells. Provide support and protection for neurones. 4 main functions: surround neurones and hold them in place, to supply nutrients/ O2 to neurones, to insulate one neurone from another, to destroy/ remove dead neurones
Why are some axons unmyelinated
C fibres are sensory neurones in the PNS that are unmyelinated with a slow velocity 2 m/s. Conducting pain slowly gives an advantage because we can respond to the source of pain before the pain sensation becomes intense. Sometimes it is beneficial for a signal to reach our brains because we can respond to the source of pain before the pain sensation becomes intense.
What is myelin and what primary function does it serve
Myelin consists of several types of lipids and proteins giving the Schwaan cells a higher proportion of lipid than other membranes. The parts of Scwann cells that contain most of the cytoplasm and nuclei remain outside the myelin sheath= saltatory conduction
What is one important demyelinating disease
Multiple sclerosis
What happens in multiple sclerosis
Features include weakness, paraesthesia or focal sensory loss, optic neuritis, diplopia, ataxia and vertigo. Autonomic motor abnormalities of bladder, bowel and sexual function are common. Other manifestations can include painful muscle spasms, trigeminal neuralgia, fatigue and depression, subtle cognitive difficulties, psychiatric disturbances and seizures. Lesions are usually seen on MRI. Neurophysiological investigation often shows delayed visual or other sensory-evoked responses. Typically, multiple sclerosis follows a RELAPSING and REMITTING course but it can be progressive from the outset or can become progressive after initial remissions
What happens in Tay-Sachs disease
Excess myelin seriously impairs nervous system functioning. In Tay-Sachs disease, an inherited lysosomal enzyme defect causes myelin to accumulate, burying neurons in lipid. The child shows symptoms around six months - losing sight, hearing, and muscle function until death occurs by age four.
What is osmium staining of a neurovascular bundle revealing
Osmium binds to lipids so reveals lipid rich areas such as the adipocytes and the myelin sheaths
