Transcript Nervous system

Nervous System
By the end of the lesson you should be able to
 Describe the transmission of impulses from
senses to central nervous system and back to
muscles.
 Describe the reflex action and the pathway
of the reflex arc.
 Describe the function of reflex response.
 Describe the role of the central nervous
system.
nervous system
Cells of the Nervous System
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Neurontransmit
impulses,
amitotic( Lack
centrioles)
Neuroglia/
“Glial”- hold the
functioning
neurons
Basic nerve cell structure
Cross section of myelin sheaths
that surround axons
3 main types of nerve cells
sensory
neuron
relay
neuron
motor
neuron
Sensory neurons
Carries impulses from receptors e.g pain
receptors in skin to the CNS( brain or spinal
cord)
Relay neuron
Carries impulses from sensory nerves to
motor nerves.
Motor neuron
Carries impulses from CNS to effector e.g.
muscle to bring about movement or gland to
bring about secretion of hormone e.g ADH
Types of Glial Cells
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Astrocytes- hold
neurons and blood
vessels
Microglia- capable
of phagocytosis,
“Police force and janitorial
service”
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Oligodendrogliahold nerve fibers
together, produce
myelin sheath
Transmission of signals
The Synapse
Neurotransmitters
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small molecules, some are even hormones.
The time for neurotransmitter action is between
0,5 and 1 millisecond.
Neurotransmitters are either destroyed by specific
enzymes in the synaptic cleft, diffuse out of the
cleft, or are reabsorbed by the cell.
More than 30 organic molecules are thought to
act as neurotransmitters. The neurotransmitters
cross the cleft, binding to receptor molecules on
the next cell, prompting transmission of the
message along that cell's membrane.
neurotransmitters are active for only a short time.
Enzymes in the cleft inactivate the
neurotransmitters. Inactivated neurotransmitters
are taken back into the axon and recycled.
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Main parts of the Brain
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cerebrum (seat of consciousness),
cerebellum, and the medulla
oblongata (these latter two are
"part of the unconscious brain").
The major brain areas and lobes
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The occipital lobe (back of the
head) receives and processes
visual information.
The temporal lobe receives
auditory signals, processing
language and the meaning of
words.
The parietal lobe is associated
with the sensory cortex and
processes information about
touch, taste, pressure, pain, and
heat and cold.
The frontal lobe conducts three
functions:
-motor activity and
integration of muscle
activity
-speech
-thought processes
Cerebrum
Cerebral
hemispheres are
divided by the
corpus callosum .
. governs
intelligence and
reasoning,
learning and
memory.
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Cerebellum
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The cerebellum is the third part of
the hindbrain, but it is not
considered part of the brain stem.
Functions of the cerebellum include
fine motor coordination and body
movement, posture, and balance.
Midbrain and pons
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The midbrain and
pons are also part
of the
unconscious
brain.
Thalamus
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The thalamus serves as a central
relay point for incoming nervous
messages.
Hypothalamus
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regulates
homeostasis
It has regulatory
areas for thirst,
hunger, body
temperature, water
balance, and blood
pressure, and links
the Nervous System
to the Endocrine
System.
The Spinal Cord
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The gray matter of the
spinal cord consists mostly
of cell bodies and
dendrites.
The surrounding white
matter is made up of
bundles of interneuronal
axons (tracts). Some tracts
are ascending (carrying
messages to the brain),
others are descending
(carrying messages from
the brain).
The spinal cord is also
involved in reflexes that do
not immediately involve the
brain.
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1Spinal Nerve
5Central Canal
2Dorsal Root Ganglion
6Grey Matter3Dorsal Root
(Sensory)
7White Matter
4Ventral Root (Motor)
Protective membranes of the Spinal Cord
Dura Mater- tough tube that encases the
two inner membranes
(arachnoid and pia mater)
•spinal fluid, commonly called
cerebrospinal fluid (CSF).
•cushions, protects and nourishes the
spinal cord and nerve roots.