Download Nervous System1

Nervous system
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The nervous system has two divisions.
The central nervous system (CNS)
consists of the brain and spinal cord.
The peripheral nervous system (PNS)
consists of cranial nerves and spinal
nerves. The PNS includes the
autonomic nervous system (ANS).
Anatomy of the brain
The brain weighs one and half kilo
It receive 15% of cardiac output
The brain is four regions
• Cerebral hemispheres
• Diencephalon
• Brain system
• Cerebellum
Cerebral hemispheres
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Most superior part of brain
Two cerebral hemispheres, RT lt.
Elevated ridges called gyri
Shallow grooves called sulci
Deep grooves called fissures
Fissures divide the brain to lobes
Divided two two halfs by one
longitudinal fissure
Other fissured divide brain to lobes
Somatic sensory area
 Parietal lobe
 Posterior to central sulcus
 Sensation from all over the body
 Opposite side
 Up side down
Primary motor area
Anterior to frontal sulcus in frontal lobe
Movements to all parts of body muscles
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Visual area
• Posterior part of occipital lobe
Auditory area
• Temporal lobe, near lateral sulcus
Olfactory area
• Deep in temporal lobe
Broca’s area
Speech center, base of precentral gyrus
Located in one cerebral hemisphere LT
Damage to this area lead to inability to say
words
Grey matter is composed of neuron cell bodies, in outer
most part of cerebrum
White matter is composed of nerve fibers, in deeper
region
Corpus callosum
Large fibrous tract connect the two cerebral hemispheres
together
Arch above structures of brain stem, allow cerebral
hemispheres to communicate together
Basal nuclei of grey mater
Present in white mater,help regulate voluntary motor
activities, by modifying instructions from CC
Diencephalon
Sit on top of brain stem
Enclosed by cerebral hemispheres
Formed of
Thalamus: relay station for sensations
going up to cerebral cortex
Enclose shallow third ventricle
Give us a crude recognition of sensation
Hypothalamus:
Important autonomic nervous center, play a role in
regulation of body temperature, water balance and
metabolism
Center of many drived emotion
Limbic system Emotional –visceral brain
Thirst, appetite sex,pain and pleasure
Regulate pituitary gland, which hang from its anterior
floor
Epithalamus: formation of cerebrospinal fluid
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Brain stem
Is the size of a thumb,3 inches long
is divided into
Pathway for ascending and descending
tracts
Midbrain, pons and medulla:
contain centers which regulate blood
pressure, heart rate, respiration,
swallowing
Cerebellum
Important for balance, equilibrium,
coordination.
Meninges: are the covering and
protectors of CNS.
Three layers
Dura mater: hard formed of two layers,
one encloses the the inner surface of
skull, forming the periosteum, the inner
called meningeal layer, form the outer
most covering of brain
Continue as dura mater of spinal cord
Arachnoid mater: is the middle
layer, has spider like projections
Subarachnoid space filled with
cerebrospinal fluid.
Pia mater: third layer fixed to
surface of brain
Cerebrospinal fluid
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150ml
Is like blood plasma,but contain less protiens,more
vit C,ion composition different
Formed in choroids plexus, it forms water cushion
protecting the brain.
Circulate the subarachnoid space, and absorbed
into blood through arachnoid villi.
Inside brain it is continuously moving in, and
around brain, and spinal cord.
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It circulate from two lateral ventricles in
cerebral hemispheres, then to third
ventricle in dincephalon,,then through
cerebral aqueduct of mid brain to fourth
ventricle
Most circulate through subarachnoid
space through three opening in fourth
ventricle
25% reach spinal cord through central
canal of spinal cord
• Blood-brain barrier: is impermeable
capillaries which allow only water,
glucose, and essential amino acids to
diffuse to brain surface
Spinal cord:
Is 42cm long?
Start at foramen magnum
End at level of L1-L2.
31 pair of spinal nerve leaves it.
Collection of nerves at distal end
called cauda equine, after the
spinal cord end.
Spinal nerves and nerve plexuses
31 Pairs of mixed nerves
Four plexuses
Cervical CI-C5
Brachial C5-C8,T1
Lumbar
L1-L4
Sacral
L4-L5,S1-S4
Important nerves
Phrenic diaphragm
Radial arm, fore arm extensors
Median flexors of forearm, thumb
muscles
Ulnar wrist, and hand muscles
Femoral anterior thigh and hip
muscles
Sciatic lower trunk, back thigh, leg
foot muscles
STRUCTURE OF NEURON
• Cell body
• Axon
• dendrite
GLIAL CELLS
• CNS
• Oligodendrocytes
• Ependymal cells
• Astrocytes
• Microglial cells
• PNS
• Neurolemmocytes
(Schwann cells)
• Saltellite cells
NERVE FIBERS
TYPES OF NEURONS
Nerve cells are called neurons, or nerve fibers.
• Neurons may be classified into three groups: sensory neurons,
motor neurons, and interneurons .
• Sensory neurons (or afferent neurons) carry impulses from
receptors to the central nervous system. Receptors detect
external or internal changes and send the information to the
CNS in the form of impulses by way of the afferent neurons. .
Sensory neurons from receptors in skin, skeletal muscles, and
joints are called somatic; those from receptors in internal
organs are called visceral sensory neurons.-
• Motor neurons (or efferent neurons) carry impulses from
the central nervous system to effectors.
• The two types of effectors are muscles and glands.
• In response to impulses, muscles contract or relax and
glands secrete.
• Motor neurons linked to skeletal muscle are called
somatic; those to smooth muscle, cardiac muscle, and
glands are called visceral.or
(ANS).
• ANS include the sympathetic&parasympathetic nervous
system.
ANS
Sympathetic
parasympathetic
thoracolumbar
craniosacral
Fight or flight
Sressfull conditions(fright)
Rest&digest
Normal resting conditions
Increase HR &RR
Decrease HR
Vasodilatation in skin
&skeletal muscles
Decrease GIT
secretions&peristalsis
Increase GIT
secretions&peristalsis
Urination&defecation
reflexes
Only symp. Supply to:
Sweat glands
Blood vessels
Thruogh cranial nerves :
3,7,9,10
• A nerve is a group of axons and/or dendrites of
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many neurons, with blood vessels and connective
tissue.
Sensory nerves are made only of sensory neurons.
The optic nerves for vision and olfactory nerves for
smell are examples of nerves with a purely sensory
function.
Motor nerves are made only of motor neurons;
autonomic nerves are motor nerves.
A mixed nerve contains both sensory and motor
neurons. Most of our peripheral nerves, such as the
sciatic nerves in the legs, are mixed nerves.
Isolated functional groupings of nerve cell bodies in the
CNS are called
"nuclei."
• Outside the brain & spinal cord, nerve cell bodies are grouped
into Ganglia, i.e., dorsal root ganglia (sensory neurons) and
sympathetic chain ganglia of the autonomic system
• Tract  group of axons that have similar origin, termination
and course and transmit the same information