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1. Nervous System

2. Content
o Introduction of nervous system
o Organization of nervous system
o Nervous tissue
o Neurons and its types
o Supporting cells
o Ascending tract and descending tract
o Reflex

3. Introduction
 Nervous system is:
 A physically connected network of cells, tissues and organs
that allow us to communicate with and react to the
environment and perform life activities.
 Master controlling and communicating system
 Has two main division
 Central nervous system
 Peripheral nervous system

4. FOUR PRIMARY FUNCTIONS OF
NERVOUS SYSTEM
 Sensing the world
 Vision, Hearing, Smell,
Taste, Touch
 Transmitting information
 Processing information
 Producing a response

5. Organization
A. Central Nervous System (CNS)
▫ Brain & spinal cord
▫ Integrative and control centers
-Receives, interprets and sends signals to PNS
B. Peripheral Nervous System (PNS)
▫ Nerves (31 pairs of spinal nerves,12 pairs of cranial nerves)
▫ Communication lines between CNS and rest of body
▫ Two Divisions:
1. Sensory (afferent) Division: Sensory receptors --
CNS
2. Motor (efferent) Division: CNS -- effectors (muscles &
glands)

6. Motor Division
 Somatic nervous system (voluntary)
- control skeletal muscles
 Autonomic nervous system (ANS) (involuntary)
– regulate smooth muscles, cardiac, glands
▫ Subdivisions:
o Sympathetic :
o “Fight or Flight”
o Activated during emergencies, exercise or vigorous physical activity
o Revs up body to respond to situations that upset homeostasis
o Parasympathetic:
o “Rest & Digest”
o Reduces energy use
o Promotes:
o Storage of energy
o Elimination of wastes
o Homeostasis

10.  The mammalian brain is
highly complex, containing
many specialized regions that
carry out specific functions.
 Generally, the brain is
divided into:
 Hindbrain
 Midbrain
 Forebrain
THE COMPLEX BRAIN

11. Hindbrain
 Medulla:
 Controls autonomic
functions.
 Pons:
 Controls sleep stages.
 Cerebellum:
 Coordinates movement,
stores some motor memory.
 Helps maintain posture,
muscle control, and balance

12. Midbrain
 Located between the hindbrain and forebrain.
 All sensory and motor information that travels
between the forebrain and the spinal cord
passes through the midbrain
 making it a relay station for the central
nervous system.
 the “traffic cops” of the brain.
 Filters sensory input, which allows us to
concentrate.
 Filtering can be affected by higher thoughts.

13. Forebrain
 Thalamus:
 relay station channeling
sensory information.
 Limbic system:
 basic emotions, drives, and
behaviors.
 Cortex:
 higher thought

14. Limbic system
 Hypothalamus:
 Master controller of the
endocrine system.
 Amygdala:
 sensations of pleasure or
fear, recognition of fear
in others.
 Hippocampus:
 formation of memories.
Damage to these areas can lead to
amnesia or emotional disturbances
“controls: emotions and memories”

15. Cortex
 Various areas :
 control
sensory
processing
 motor
control,
 thought,
 memory.
Top layer of the brain
Stores: experiences and/or learning
behavior & emotion
Sensory info
concerning touch
vision
memory & emotion,
speech and hearing

16. Spinal cord
 Grey matter
 mostly made up of cell bodies of neuron
 White matter
 composed of nerve fibers ( ascending and descending tracts )
embedded in neuroglial cells

18. Nervous Tissue
1. Neurons (nerve cells)
• Functional unit of the nervous system
• Transmit message
Anatomy:
 Cell body – contains nucleus; metabolic center
 Dendrite – fiber that conveys messages toward cell body
 Axon – conduct nerve impulses away from the cell body
 Axon terminals – end of axon; contain neurotransmitters&
release them
 Synaptic cleft/synapse – gap between neurons

20. Nervous Tissue
2. Supporting cells (Neuroglia)
 CNS: astrocytes, microglia, ependymal cells,
oligodendrocytes
 barrier between capillaries and neurons protect
neurons
 immune/defense
 line brain and spinal cord cavities wrap nerve
fibers
 produces myelin sheaths (covering)
 PNS: Schwann cells, satellite cells
 surround large neurons protect & cushion

22. Myelin
 Whitish, fatty material that covers nerve fibers to
speed up nerve impulses
Schwann cells
 Surround axons and form myelin sheath
Myelin sheath
• Tight coil of wrapped membranes
Nodes of Ranvier
 Gaps between Schwann cells

23. • Ganglia: collections of cell bodies
• Bundles of nerve fibers = tracts (CNS) or nerves (PNS)
• White matter
• Dense collections of myelinated fibers
• Gray matter
• Unmyelinated fibers & cell bodies
• (nerve cell bodies, dendrites, axon terminals, bundles of
unmyelinated axons and neuroglia (gray color)

24.  Dendrites receive signals.
 The cell body integrates
signals.
 The axon transmits action
potential. The myelin
sheath makes the signal
travel faster.
 Synaptic terminals
transmit signals.
The Neuron

25. Neurons
 Neuron Function
 Irritability:
 ability to respond to stimulus &
convert to nerve impulse
 Conductivity:
 transmit impulse to other neurons,
muscles, or glands
 Classification of Neuron
 Functional Classification
 Structural Classification

26. 1. Functional Classification:
Direction nerve impulse is traveling
Sensory
neurons
Motor
neurons
Interneurons
carry impulses from
sensory receptors to
CNS
carry impulses from
CNS to muscles &
glands
connect sensory &
motor neurons
Vision, hearing,
equilibrium, taste,
smell, pain,
pressure, heat

27. 2. Structural Classification:
Processes extending from cell body
Multipolar Bipolar Unipolar
1 axon, several
dendrites
1 axon, 1 dendrite 1 process
Most common
(99%)
Rare
Short with 2
branches (sensory,
CNS)
Eg. Motor
neurons,
interneurons
Eg. retina, nose,
ear
Eg. PNS ganglia

29. Nerve Impulses
 Cell membrane at rest = polarized
 Na+outside cell, K+inside cell
 Inside is (-) compared to outside
 Stimulus ---excited neuron (Na+rushes in)--
becomes depolarized
 Depolarization activates neuron to transmit an
action potential (nerve impulse)
 All-or-none response
 Impulse conducts down entire axon
 K+ diffuses out ---repolarization of membrane
 Na+/K+ ion concentrations restored by sodium-
potassium pump (uses ATP)
Exciting a Neuron

31. References
 Elaine N. Marieb, Human Anatomy and Physiology 9th Edition .
 Dr. Henry Gray and Dr. Henry Vandyke Carter , Grays Anatomy for
Students 40th Edition.
 Various internet sources.