topic 2: lesson 1 Flashcards
(18 cards)
define CNS
control centre. consists of the brain and the spinal cord.
define PNS
the nerve fibres that connect the CNS to all the muscles, receptors and glands throughout the body.
the nerve fibres of the PNS are ….
arranged into nerves (bundles of fibres) which arise from the brain and spinal cord
what are the two types of the nerves in the peripheral nervous system?
cranial nerves
spinal nerves
explain cranial nerves:
-arise from the brain (12 pairs, e.g. optic nerve)
-some are sensory fibres-carry signals into CNS
-some are motor fibres-carry signals away from CNS
-most are mixed fibres- carry sensory and motor impulses
explain spinal nerves:
arise from spinal cord (31 pairs)
-they are all mixed fibres
-each spinal nerve is joined to the spinal cord by 2 roots
define dorsal root
contains the axons of sensory neurons- takes info into spinal cord
(afferent sensory fibres)
define ventral root
contains the axons of motor neurons- takes away info from spinal cord
motor neurons have cell body within spinal cord
(efferent motor fibres)
define dorsal root ganglion-
contains the cell bodies of the sensory neurons
Nervous tissue is not good at repairing itself: there are three structures that protect the CNS, what are they?
1.Bone
2. series of membranes called meninges
3. fluid called cerebrospinal fluid (CSF)
explain how Bone protects the CNS:
bone is the outermost layer
-cranium= part of the skull which houses and protects the brain
-vertebra= protect the spinal cord which run through an opening in the middle called the vertebral canal
explain how Meninges protects the CNS:
3 membranes found inside the bones and covering the surfaces of the brain and spinal cord. they cover the entire CNS.
outer meningeal layer= Dura mater = tough and fibrous
-sticks closely to bottom of cranium but does not stick closely to the vertebral canal
-middle meningeal layer= arachnoid mater= a lose mesh of fibres with fluid flowing between the fibres (CSF)
-Inner meningeal layer= pia mater= very delicate
-sticks closely to the brain and spinal cord
-contains many blood vessels
explain Cerebrospinal fluid in the CNS:
-clear, watery fluid- contains few cells and glucose, protein, urea and salts
-occupies the space between the middle and inner layer of the meninges. also circulates through cavities in the brain and through a canal in the very centre of the spinal cord
-formed by/from the blood and it curculates around and through the central NS before reentering the blood capillaries
explain the three roles of Cerebrospinal Fluid in protecting the CNS:
-protection= acts as a shock absorber, cushioning the CNS from any shocks
-support= the brain is suspended in the cranium and floats in the fluid that surround its
-transport= as the CSF circulates through the CNS it carries nutrients to the cells of the brain and spinal cord and carries away their waste
give some detail about spinal cord
-extends from Foramen magnum to the L2 vertebrae
-thought of as an extension of the medulla oblongata
enclosed in the vertebral canal, and surrounded by 3 meningeal layers
-fat, connective tissue and blood vessels act as padding around the spinal cord and allows for movement
define grey matter; spinal cord:
-composed of nerve cell bodies and unmyelinated nerve fibres
-forms a shape that looks roughly like a H
-in the middle of the H is a small space called the central canal- which contains CSF
define white matter; spinal cord:
myelinated fibres
bundles of these fibres are arranged into ascending and descending tracts
functions of the spinal cord:
-carries impulses to and from the brain (via ascending and descending tracts in the white matter)
-integrate certain reflexes
allows responses to be faster as it does not have to be sent all the way to the brain
