The human nervous system is made up of the central nervous system (brain and spinal cord) and the peripheral nervous system. The nervous system controls and coordinates functions throughout the body using electrical signals called nerve impulses that are carried by specialized cells called neurons. There are three main types of neurons - sensory neurons that carry impulses from sense organs to the CNS, motor neurons that carry impulses from the CNS to muscles and glands, and interneurons that connect sensory and motor neurons. The peripheral nervous system is divided into sensory and motor divisions, and regulates both conscious and involuntary activities.

1. Human Body Systems
Nervous Systems

2. Human Body Systems
• Humans have complex systems
• Cells are grouped for efficiency
• Dynamic equilibrium

3. Levels of Organization
In a multicellular organism levels are:
cells  tissues organs organ
systems
tissues: group of similar cells that perform
same function
organ: group of tissues that work together to
perform complex function (ex: sight)
organ system: group of organs that perform
closely related functions

4. Human Organ Systems
• Nervous System
• Respiratory System
• Digestive System
• Skeletal System
• Muscular System
• Circulatory System
• Excretory System
• Endocrine System
• Lymphatic/Immune
System
• Reproductive System

5. Body Systems Functions
• Although each of the 10 organ systems
has a different set of functions, they all
work together, as a whole, to maintain
homeostasis.

6. Nervous System
• The nervous system controls and
coordinates functions throughout the body
and responds to internal and external
stimuli
• Nearly all multicellular organisms have
communication systems
– Specialized cells carry messages from one
cell to another
– Smooth and efficient communication through
the body

7. Nervous System
• Messages carried by nervous system are
electrical signals called impulses
• Cells that transmit these impulses are
called neurons (basic units of nervous
system)
– 3 types of neurons
1. Sensory
2. Motor
3. Interneurons

8. Neurons
• Sensory: Carry impulses from sense
organs (eyes, ears, etc) to the spinal cord
and brain
• Motor: carry impulses from the brain and
spinal cord to muscles and glands
• Interneurons: connect sensory and motor
neurons and carry impulses between them

9. Parts of a Neuron
• Cell Body
– Largest part; contains nucleus and most of cytoplasm
– Most metabolic activities occur here
• Dendrites
– Short, branched extensions
– Carry impulses from environment or other neuron toward cell
body
– Neurons can have several dendrites
• Axon
– Long fiber which carries impulses away from cell body
– Ends in axon terminals, located a distance away from cell body
– Neurons only have one axon
• Myelin Sheath
– Insulating membrane surrounding axon

10. Neuron

11. Nerve Impulse
• An impulse begins when a neuron is
stimulated by another neuron or the
environment

12. Synapse
• Location where a
neuron can transfer
an impulse to another
cell
• Space between
neurons
• Neurotransmitters are
chemicals used by
neurons to transmit
an impulse across the
synapse

13. Human Nervous System
• Divided into two major divisions:
– Central Nervous System (CNS)
• Relays messages, processes info and
analyzes info
– Peripheral Nervous System
• Receives information from the environment
and relays commands from the CNS to
organs and glands

14. Central Nervous System
• Brain
Cerebrum
Cerebellum
Brain Stem
Thalamus and
hypothalamus

15. Brain
• Made of 50-100 billion neurons
• 4 lobes or regions
– Frontal Lobe- memory, judgment, inhibitions,
personality
– Temporal Lobe- Long term memory, auditory
processing
– Occipital Lobe- Vision processing
– Parietal Lobe- Sensory integration

17. Spinal Cord
• Main communications link between the
brain and the rest of the body
• Certain kinds of info (reflexes) are
processed in spinal cord
• Reflex is a quick, automatic response to a
stimulus
– Sneezing and blinking
– Allows your body to respond to danger
immediately without thinking

18. Peripheral Nervous System
• Lies outside of CNS
• Consists of all the nerves and cells that
are not a part of the brain or spinal cord
– Cranial nerves
– Divided into 2 divisions:
• Sensory
• Motor

19. Peripheral Nervous System
Sensory division:
transmits impulses from sense organs to the
CNS
Motor division:
transmits impulses from CNS to muscles and
glands
1. somatic nervous system- regulates
conscious controlled activities
2. autonomic nervous system- regulates
activities that are automatic or involuntary
~Divided into sympathetic and
parasympathetic nervous system