CENTRAL NERVOUS SYSTEM

2. NERVOUS SYSTEM
The nervous system is the part of an animal's
body that coordinates its voluntary and
involuntary actions and transmits signals
between different parts of its body. Nervous
tissue first arose in wormlike organisms about
550 to 600 million years ago. In most animal
species it consists of two main parts, the
Central Nervous System (CNS) and the
Peripheral Nervous System (PNS). The CNS
contains the brain and spinal cord. The PNS
consists mainly of nerves, which are enclosed
bundles of the long fibers or axons, that
connect the CNS to every other part of the
body.

3. Your Nervous System
Credit Medical Art Service, Munich /, Wellcome Images
Is divided into the central
nervous system (CNS)
Which is the brain and
spinal cord
And the
peripheral nervous system
(PNS)
Which connects everything
to the brain and spinal cord

4. Central Nervous System
– CNS: brain and spinal cord
– Necessary for the maintenance of homeostasis
– Contains 1011 neurons
– Contains 1014 synapses
– Responsible for everything we perceive, do, feel,
and think

5. PARTS OF CNS
The Spinal Cord
The Brain

6. The Brain
• The brain is the control
center of the body
• It is about 2% of your
body weight and uses
20% of your body’s
oxygen

7. Parts of the Brain
Divided into
three parts
Cerebrum Cerebellum Brain Stem

9. Cerebrum
1. Largest part of the brain
– Learning and Senses
– 2 hemispheres- Right and Left
– Connected by the Corpus Callosum
– Right side controls- left side
– Left side controls – right side of body
– Four sections - LOBES
1. Frontal Lobe 2. Parietal Lobe
3. Occipital Lobe 4.Temporal Lobe

10. Premotor cortex
(coordinates
voluntary
movements)
Primary somatosensory
cortex (somesthetic sensations
and proprioception)
Sensory association
areas (integration of
sensory information)
Primary motor cortex
(voluntary movement)
Central sulcus
Prefrontal
association
areas (idea and
plan for voluntary
movement, thoughts,
personality)
Broca’s area
(speech formation)
Olfactory cortex
(smell)
Limbic association
cortex (emotions,
learning, and memory)
Visual association
areas (higher vision
processing)
Wernicke’s area
(language
comprehension)
Auditory
association
areas
Primary auditory
cortex (hearing)
Primary visual cortex
(vision)
Figure 9.14
Functional Areas of Cerebrum

11. Cerebellum
– Second largest
– located below the
cerebrum at back of
skull
– This part is responsible
for the balance and
muscle coordination

12. Other Structures inside the Brain
• Thalamus – receives messages from sensory
receptors; relays information to proper
regions of cerebrum
• Hypothalamus - Regulates hunger, thirst,
fatigue, anger, etc…
– Control of pituitary for endocrine function

13. Spinal Cord
• Link between brain and rest of body (PNS)
• 31 pairs of spinal nerves
• Reflexes processed directly by spinal cord
• Reflex – quick, automatic, unconscious
responses
• Result of reflex arcs – shortest nerve pathways

15. Spinal Cord and Spinal Nerves
• Dorsal: sensory functions
• Ventral: motor functions
Gray matter:
functional halves
Spinal nerves are
mixed
• Ascending
• Descending
White matter
forms tracts

16. Spinal Cord: Tracts
Figure 9.9

17. Spinal Cord: Ascending Tracts
Figure 9.10a

18. Spinal Cord: Descending Tracts
Figure 9.10b

19. Cross Section of the Spinal Cord

20. CNS: Physical Support
Figure 9.2a

21. Different regions have different
Functions Cerebral cortex
Functions include:
planning; reasoning;
language; recognising
sounds and images;
memory. Corpus
callosum
connects the brain’s
right and left
hemispheres
Cerebellum
important for
coordination,
precision and timing
of movement
Brain stem
regulates heart
rate, breathing,
sleep cycles
and emotions

22. The cells of the nervous system are called Neurones
cell body
dendrites nerve endings
myelin sheath
axon
nucleus
structure of a neurone

23. There are different types of neurons
motor neurone sensory neurone relay neurone
direction of
electrical
signal
sends signals to your muscles
to tell them to move
sends signals from
your sense organs
connects neurones to
other neurones
dendrites
cell body
axon
myelin
sheath
nerve
endings

24. neurones communicate with each other using a
mixture of electrical & chemical signals
cell body
dendrites nerve endings
myelin sheath
nucleus an electrical
axon
signal is
transmitted
along the axon
But what happens when the signal
reaches the end of the axon?

25. cell body
Signals cross between neurones at the Synapse
synapse
dendrites nerve endings
myelin sheath
vesicle
nucleus the signal
axon
neurotransmitter
is transmitted to
another neurone across a
junction called a synapse by
chemicals called
neurotransmitters.
synaptic cleft
receptor

26. Signals cross between neurones at the Synapse
vesicle
the signal
dendrites nerve endings
is transmitted to
myelin sheath
another neurone across a
junction called a synapse by
chemicals called
neurotransmitters.
electrical impulse triggers vesicles
to move to the synapse membrane
cell body
axon
nucleus
synapse
neurotransmitter
synaptic cleft
receptor
1
vesicles fuse with the membrane and
release neurotransmitter into the
synaptic cleft
2
neurotransmitter diffuses across
the cleft and binds to receptors
on the other side
3
Once enough receptors have
neurotransmitters bound to
them, the signal is
transmitted…
4

27. The point where your muscles and nervous system meet is called the
neuromuscular junction (NMJ)
Signals sent from your central nervous
system to the NMJ tell muscles to move
The synapses at the NMJ
use a neurotransmitter
called acetylcholine

28. THANK YOU