WEEK 8 NERVOUS SYSTEM Flashcards
What does the PNS consist of ?
Cranial nerves (12 pairs)
Spinal nerves (31 pairs) : 8 cervical 12 T, 5L, 5S, 1coxygeal
Ganglia
Plexuses
How are spinal nerves named?
Based on the segment or region of body they supply
What are ganglia?
Discrete clusters of neurons distributed outside the CNS and occur across body
What is special about the cervical vertebrae and nerves?
There are 8 cervical nerves but only 7 cervical VERTEBRAE
What is the input part of nervous system and what does it do?
Sensory division, transmits stimuli from receptors (secialised ends on neurons)
What are the two components that sensory can be divided into?
Somatic sensory and visceral sensory
What does the somatic sensory component do?
Transmits sensory inputs from strucutres in body wall (anything that isn’t an organ) - touch and temperature, pain, pressure, vibration
What does the visceral sensory component do?
Transmits impulses from blood vessels, viscera to the CNS (temperature and stretch) and sensory input from visceral organs like heart blood vessels GI tract.
- has much narrower range of receptors so can only receive certain types of stimuli
What is the output part of the CNS?
Motor division
What does the Somatic Motor system do?
Transmits nerve impulses to skeletal muscles
What is the ANS associated with and what does it innervate?
Visceral organs and vessels
- Innervates smooth & cardiac muscle tissue, and glands
What is nervous tissue?
Its own type of tissue that comprises of neurons and glial cells
What are glial cells?
Non excitable cells (support and protect neuron)
What does the soma do?
(body) receives, integrates, and initiates impulseds
What do dendrites do?
Contain the synapses (communication b/w individual neurons) - receptive region of neuron
What do axons do?
Transmission pathway for impulses generated by the soma, towards other neurons or target organ
What are multipolar axons?
Have one single axonal process e.g. motor neurons
What are unipolar neurons?
Have two exonal processes extening from soma .e.g. sensory neurons
What are examples of bipolar neurons?
In the special sensory crainial nerves such as ganglion of vestribulocochlear nerve
Are dendrites, synaptic nobs, and soma myelinated or unmyelinatetd?
unmyelinated to receive and transmit signals
Why are myelinated parts of neurons white?
Because of fats within neurolimicytes
What colour areunmyelinated parts?
Gray
What is the ventral horn of gray matter for?
Motor division
What is the dorsal horn of gray matter for?
Sensory division
What does ventral white matter represent?
Motor axons and descending pathways
What does dorsal white matter represent?
Sensory axons and ascending pathways
What types of nerves are spinal nerves?
Mixed nerves composed of both motor and sensory components
What are the roots of the spinal cord?
Myelinated axons (dorsal and ventral) that are EITHER motor or sensory- no mixing of motor and sensory unitl further down
What does the dorsal root ganglion function as?
To house the first order neurons (unipolar neruons), have long axonal processes in peripheri detecting sensations and the shorter axonal process extending from dorsal root ganglion to dorsal horn of spinal cord
Where is the mixed spinal nerve found?
Just lateral to the spinal cord
Which structure is the first to house mixed nerves?
The dorsal and venrtral rami (ramus for singular)
What is endonerium?
Delicate layer of loose connective tissue -each myelinated nerve is wrapped around this
What is perinerium?
Bundles of nerve fibre wrapped in this (cellular and fibrous layer) to form fascicles
What is epinerium?
Wraps around the fascilcles (dense irregulave connective tissue covering the ENTIRE NERVE)
Do nerves contain blood vessels?
YES they require vascularisation
What is the brain continuous with?
The brainstem
What does the ectoderm becom after development?
epidermis of skin and CNS
What does the endoderm become?
Lining and inside of GI tract
What does the mesoderm form?
Most of the tissues–> in development, turns into series of blocks called somites (31 pairs) which becomes the mixed spinal nerves - dermatomes- strips of segments
Why does segmentation become difficult with limbs?
Because limbs are outgrowths from the midline axis
What does the sclerotome (division of somite) form?
Bone (tough part)
What does the myotome (division of somite) form?
Forms skeletal muscle
What does the dermatome (division of somite) form?
The dermis (deep to epidermis)
What happens when the nervous system is formed?
The axon is grown out from CNS to reach target which could be a sclerotome