pppppppppppppppppp

1. Nervous System

2. Content
oIntroduction of nervous system
oOrganization of nervous system
oNervous tissue
oNeurons and its types
oSupporting cells
o Ascending tract and descending tract
oReflex

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”
oActivated during emergencies, exercise or vigorous physical activity
oRevs up body to respond to situations that upset homeostasis
o Parasympathetic:
o“Rest & Digest”
oReduces energy use
oPromotes:
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.