Peripheral nervous system Flashcards
What is the peripheral nervous system divided into?
Somatic and autonomic nervous systems
Which neurones transmit information towards the CNS?
Sensory afferent nerves
Which neurones transmit information away from the CNS?
Motor efferent nerves
How many pairs of spinal nerves are there?
31
What is a neural plexus?
Derived from multiple spinal cord segments, and is an intricate network of nerves
Which layer sheaths the entire nerve?
Epineurium
Which layer surrounds the bundles of nerve fibres?
Perineurium
Which layer is intermediate of individual nerve fibres?
Endoneurium
Which meningeal layer is continuous with the epineurium?
Dura mater
Which two meningeal layers are continuous with the endoneurium and the perineurium?
Pia mater and the arachnoid layer
What is a dermatome?
An area of skin that is supplied by a single spinal nerve (strips of skin consists of a single nerve)
What is a myotome?
Group of muscles innervated by a single spinal nerve
What nerves conduct sensory impulses from the viscera?
Visceral afferent nerves
Do parasympathetic efferent nerves innervate the blood?
No
Which structure contains multiple cell bodies existing outside the CNS?
Ganglia
Which structure contains a collection of cell bodies inside the CNS?
Nucleus
Where are afferent somatic and visceral fibre cell bodies?
Reside within spinal ganglia
Which nerve fibres synapse with the peripheral ganglion?
Peripheral nerves
How are peripheral nerves arranged?
Bundled in fasiciuli, comprised of three connective tissue layres: (Epineurium, perineurium, and endoneurium)
Which layer sheaths individual fasicules?
Perineurium
Which layer sheaths individual axons?
Endoneurium
What two parameters are used to classify peripheral nerves?
Based on conduction velocity
Based on axonal diameter
What classification system is used to classify nerves based on conduction velocity?
Letters (ABC)
A- fastest
Which classification system is used to classify nerves based on axonal diameters?
Roman numerals (I-IV) 1 fastest
Which nerves are classified under the axonal diameter system?
Sensory nerves exclusively
What effect does myelination have on conduction velocity?
Increases conduction velocity due to the principle of saltatory conduction
What are exteroceptors
Detect pain, touch, pressure and temperature
Which receptors detect movement and joint position?
Proprioceptors
Which receptors detect the internal environment (Blood pH,and gastrointestinal movement)?
Interoceptors
What are chemoreceptors?
Specialised sensory receptors transduce a chemical substance and subsequently generates an electrical
signal
Where are chemoreceptors located?
Medulla = environmental pH
Peripheral= Aortic arch and carotid sinus
Olfactory bulb
Which receptors detect light in retina (rods and cones)?
Photoreceptors
What are mechanoreceptors?
Detects opening of ion channels
What are nociceptors?
Detects signals from damaged tissue or threat of damage indirectly respond to chemicals released from damage tissue
Which proprioceptor in muscle detect changes in length?
Muscle spindles
What happens during muscle stretch in terms of electrical transmission? (reflex)
Stimulates reflexively, a muscle contraction to counteract overstretching and muscle fibre damage (Myotatic reflex)
Stretching causes the muscle fibre to transmit an electrical impulse to the spinal cord to stimulate a muscular response.
What is the static component of myotatic reflex?
Persists during the time of muscular stretch
What is the dynamic component of the myotatic reflex?
Lasts momentarily in response to the initial sudden increase in muscle length
Which proprioceptor detects changes in tension in tendons?
Golgi tendon organs
Which neurotransmitter is released at an inhibitory interneuron?
Glycine, hyperpolarises motor neurone, causes muscle to relax
What is a neuromuscular junction?
Specialized synapse between a motor neuron and a muscle fibre
Motor neurone axon approaches innervated muscle
What is a motor unit?
Single motor neurone in conjunction with corresponding muscle fibres that it innervates.
Smallest functional unit to produce force
What is a motor pool?
Collection of motor neurones collectively coordinate together to stimulate contractions of a single muscle, all of the motor units within a muscle is considered as a motor pool.
Where do sympathetic neurones arise?
Thoracolumbar
What effects does sympathetic innervation have on the body?
Direct blood to muscles, dilation of pupils, increases respiratory rate, dilation of airways, increased heart rate
What effect does parasympathetic innervation have?
Rest, increased gastric secretions decreased respiratory and heart rate
Where do preganglionic efferent axons leave the spinal cord?
Through the ventral nerve roots joining the mixed spinal nerve
How do preganglionic sympathetic fibres enter the sympathetic chain of ganglia?
Through the white ramus communicans
What do paravertebral trunks contain?
Post-ganglionic neurone cell bodies
Fibres concerned with innervation of structures in the head and thorax terminate where?
Terminate in synaptic contact with postganglionic celll bodies in the sympathetic chain
Fibres concerned with innervation of structures of pelvic and abdominal viscera terminate where?
Pass uninterrupted through the sympathetic chain and travel to plexuses
What does the mixed spinal nerve contain?
Mixed spinal nerve contains pre and post-ganglionic fibres. Synapse, postganglionic neurone can ascend or descend
Where do postganglionic nerve fibres leave the sympathetic chan?
Gray ramus communicans
Why is the gray ramus communicans gray?
Unmyelinated
