Transcript The big picture:

The big picture:
The organisation of the nervous
system
Revision:
Do you understand the neuropathology of the following
at the level of the cell, synapse, motor unit ?
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Multiple sclerosis
Motor neurone disease
Myasthenia gravis
Muscular dystrophy
Parkinson’s disease
Polyneuritis: Guillain Barre
Alzheimer’s disease
• And if there are drugs to assist, how do they work?
Anatomical and functional divisions of
the nervous system
• Anatomically:
– Central nervous system:
• Brain and spinal cord
– Peripheral nervous system:
• Cranial nerves
• Spinal nerves
• Functionally:
– Somatic
• Motor and sensory
– autonomic
• General visceral sensory (afferent)
• General visceral motor (efferent)
Anatomical organisation of the
nervous system
Nervous
system
Central
nervous
system
brain
Peripheral
nervous
system
Spinal cord
Cranial nerves
Spinal nerves
Anatomical divisions of
the nervous system
White and grey matter
Cerebromente.org.uk
Antranik.org
Histology.leeds.ac.uk
White matter pathways…
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Consist of bundles of axons
Connect different paths of the CNS together
Go by a number of names:
Tracts
Fasciculi
Peduncles
Lemniscus
Capsule
Ganglia and Nuclei
• Cell bodies are grouped together
• MAINLY called ganglia in the PNS
• ….and nuclei in the CNS
• One exception = the basal ganglia
The Peripheral Nervous System
• The peripheral nervous system consists of the cranial
and spinal nerves which are connected to the central
nervous system
• There are 12 pairs of cranial nerves arising from the
base of the brain – numbered using Roman
numerals.
• There are 31 pairs of spinal nerves, each pair
numbered according to the level of the spinal cord
from which it arises.
• The cranial and spinal nerves branch to form a
network that covers all parts of the body.
Cranial
Nerves
Spinal Nerves
• Each spinal nerve is
attached to the spinal cord
by two roots.
• Dorsal root provides the
input for sensory nerves.
• Ventral root provides the
output for motor nerves
supplying glands and
muscles.
• In some places the nerve
branches interlace to form
nerve plexuses.
Transverse section of the spinal cord:
http://www.spineuniverse.com/sites/default/files/legacy-images/vert_body-BB.jpg
Quiz: chose one answer
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Sensory = afferent/efferent
Motor = afferent/efferent
Grey matter = cell bodies/axons
Cranial nerves =12 pairs/31 pairs
Spinal nerves = 12 pairs/31 pairs
Cranial nerves = motor/sensory/motor &
sensory/all of the above
• Dorsal root =motor/sensory root
• Ventral root =motor/sensory root
Functional division of the nervous system:
Nervous system
Peripheral
nervous system
Central nervous
system
Somatic
sensory
Autonomic
motor
sympathetic
parasympathetic
• Sensors: means by which the NS translates
info about the internal and external
environment into a form that is usable by the
brain
• Effectors: means by which the body responds
to changing internal and external conditions
Somatic nervous system
• Somatic motor efferent nerves leave CNS and carry info to
striated voluntary muscles
– Motor aspects are under our conscious and voluntary
control
– CNS control of somatic muscles: arises in pre-central
region of the cortex
– Then via cranial nerves and spinal nerves to all skeletal
muscles
• Somatic sensory afferents
– Sensory aspects monitor incoming information from
sensory receptors in skin, mucosa, muscles, deep organs
(viscera). Travel via thalamus to sensory cortex in parietal
lobe of cortex.
Autonomic nervous system:
• Regulates the activity of smooth muscle,
cardiac muscle and some glands
• Operates outside of our conscious control
• Is regulated by brain centres: the
hypothalamus and medulla
• Sensory input = general visceral sensory
(afferent) neurons
• Motor output = general visceral motor
(efferent) neurons
Sensory input = general visceral
sensory (afferent) neurons
Receptors inside organs or blood vessels (called
interoreceptors)
Relay information re CO2 levels, stretch or
pressure on organs/blood vessels
Motor output = general visceral motor
(efferent) neurons
• Regulate visceral activities by either exciting
or inhibiting
• The effector tissues are cardiac muscle,
smooth muscle, and glands.
• These activities lie beyond conscious control
• This output part has 2 divisions: the
sympathetic and parasympathetic nervous
systems
Sympathetic and parasympathetic
nervous systems
• The autonomic nervous system controls bodily
functions that re beyond our conscious control
• The efferent portions are divided into the
sympathetic and parasympathetic divisions
• Some organs receive input from both
branches of the ANS
• Branches usually act antagonistically..but
sometimes work synergistically
Autonomic pathways….
• The actions of the sympathetic and
parasympathetic divisions are usually
antagonistic in any tissue that is supplied by
both divisions (i.e. one division stimulates
whilst the other inhibits).
• A good example is the heart:
• sympathetic activity …………. heart rate and
parasympathetic activity …………… heart rate.
The autonomic nervous system:
http://zaccupples.files.wordpress.com/2013/04/autonomic-nervous-system.gif
The diagram shows the
arrangement of
sympathetic neurons and
the involvement of the
sympathetic chain of
ganglia.
Actions of Sympathetic & Parasympathetic
Nerves
Parasympathetic
“Rest – Relaxation”
Pupils
Sympathetic
“fight or flight”
Dilation
Heart
Increased rate
Decreased rate
Bronchi of lungs
Dilation
Constriction
Digestive muscles
Decreased contraction Increased contraction
Bladder
Relaxation
Contraction &
emptying
Kidneys
Decreased activity
none
Liver
Increased glucose
release
none
Constriction
Specificity of activity of the 2 divisions
of the autonomic nervous system
• Sympathetic activity is very generalised.
– Fight, flight..or frolic ;)
• Parasympathetic activity is very discrete.
Parasympathetic preganglionic nerves
• Travel with CN III, VII, IX and X, and the sacral
spinal nerves
• CN II, IX and X supply head and neck
structures…and sacral supplies pubic organs…
• The ‘gap’ in the middle is filled by the
wanderer –the Vagus or CN X
• Travels down thorax and abdomen and
supplies viscera in these regions
www.med.umich.edu
www.med.umich.edu
Parasympathetic ganglia:
• Lie in or near the target organ eg the parotid
salivary gland
• There, they synapse with the post-ganglionic
nerve
• These tend to be quite short and either
branch (ramify) or spread out over the organ,
or join a somatic nerve and enter that way
Chemical transmitters for the sympathetic
and parasympathetic systems:
• In both the sympathetic and parasympathetic
NS, acetylcholine acts at the ganglia and at
synapses between parasympathetic nerves
and their targets
• In the sympathetic NS, norepinephrine and
epinephrine (noradrenalin and adrenalin)
operates at four major receptor types ,
collectively called adrenoreceptors.
N
N
A
A
N
N
M
N = Nicotinic acetylcholine receptor; M= Muscarinic Ach
receptor; A= unspecified adrenergic receptor
Recall……
www.biologycorner.com
Acetylcholine
• A key neurotransmitter in the PNS and also
found in the CNS
• Drugs to treat a number of the conditions
which we are interested in as SLT have their
action on Ach
• If they reduce the action of Ach they are
called anticholinergics (PD, CPOD)
• If they prevent the breakdown of Ach they are
called cholinesterase inhibitors (MG, AD)
So..you are going into the bioscience
exam
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Your palms are sticky
Your heart is thumping
Your mouth is dry
Your skin is pale and clammy..
Which division of the nervous system is acting
on your body?
• Which neurotransmitter is at play?
Parasympatheticomimetic drug…
• What unwelcome effects might such a drug
have?
Officemum.blogspot.com
The brain
http://science.nationalgeographic.com/science/photos/brain/
lissencephaly
The brain viewed from the left side
Q: why is the left side of the brain of such interest to SLTs?
Functional zones in the cortex
http://www.sofiatopia.org/equiaeon/ibrain12.jpg
Outline of the major regions of the brain and their functions
The membranous coverings of the brain – the cranial meninges
Meninges:
http://www.advanced-neurosurgery.com/communities/2/004/010/235/862/images/4572895002.jpg
Student task:
• Write short notes on the meninges ie
• The dura mater
• The arachnoid mater
• The pia mater
The Dura Mater has a number of folds –
between the cerebral hemispheres and
above and around the cerebellum – which
stabilize the position of the brain within
the cranium – the falx cerebri – tentorium
cerebelli, falx cerebelli & diaphragma sella.
(a) Lateral view of brain within cranium (b) brain removed to show position of dural folds.
The ventricles of the brain:
(a) Lateral view (b) Frontal view
http://justanothersciencenerd.files.wordpress.com/2012/11/ventricles-of-brain.png
The circulation of cerebrospinal fluid
(a) Pattern of circulation through and around the brain and spinal cord
(b) Reabsorption of CSF into venous sinus through arachnoid granulations
www.en.wikipedia.org
Diencephalon
• This is the base of the forebrain (normally
covered above and to the sides by the cerebral
hemispheres).
Comprises:
• epithalamus (links limbic system to rest of the
brain)
• hypothalamus
• thalamus
• subthalamus
• Pineal gland
The thalamus
The thalamus is the final relay
point for ascending sensory
information.
It also plays a major role in
coordinating the activities of
the cerebral cortex, basal
ganglia and cerebellum
(a) Lateral view of brain from left side
(b) Detail of the various thalamic nuclei
The brainstem
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Brainstem =
Medulla oblongata
Pons
midbrain
The mesencephalon or mid-brain
(a) View from above (b) section viewed from anterior surface
Hind brain (diencephalon) and brain stem showing major structures and the
origins of the cranial nerves
The medulla oblongata and pons
The medulla oblongata and pons
THE BRAIN IN SECTION : what kind of section is this?
The brain in section: _______ section
What to do now: directed study
• Read about the embryological origins of the brain, to
embed your understanding of the terms below, and
their significance:
• Encephalon
• Prosencephalon
– Telencephalon
• Rhinecephalon
– Diencephalon
• Mesencephalon
• Metencephalon
• Rhombencephalon
https://www.dana.org/uploadedImages/Images/Spotlight_Images/DanaGuide_CH05_P065a_spot.jpg