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Human Body Systems
Nervous /Muscles/Skeleton
Systems
Human Body Systems
• Humans have complex systems
• Cells are grouped for efficiency
• Dynamic equilibrium
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
Human Organ Systems
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Nervous System
Respiratory System
Digestive System
Skeletal System
Muscular System
Circulatory System
Excretory System
• Endocrine System
• Lymphatic/Immune
System
• Reproductive System
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.
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
Nervous System
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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
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
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
Neuron
Nerve Impulse
• An impulse begins when a neuron is
stimulated by another neuron or the
environment
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
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
Central Nervous System
• Brain
Cerebrum
Cerebellum
Brain Stem
Thalamus and
hypothalamus
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
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
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
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
Muscles
• Nerves act on muscles to move the body
and control bodily functions
• Types of muscles
– Skeletal- Usually attached to bones; cause
voluntary movement.
– Smooth-Found in hollow organs; causes
involuntary movement
– Cardiac: Found only in the heart; causes the
heart to beat.
Smooth Muscle Tissue
• Not under voluntary control
• Found in stomach, intestines, blood
vessels, etc.
• Also, your diaphragm-the muscles which
causes your lungs to expand and contract.
Skeletal Muscles
• Skeletal muscles are called striated,
because they are collections of muscle
fibers, or cells.
• Skeletal muscle cells are very large and
complex
– From 1mm to 30 cm long!
– Have many nuclei
How do Skeletal Muscles Work?
• Muscles do their work when the
contract—that’s why each muscle in your
body has two sets, one to contract your
arm or leg in one direction, and another
muscle to contract and move it back.
• But, in order for the muscle to contract,
special steps have to happen inside each
cell.
Inside a Muscle Cell
• Inside a muscle cell, there
filaments, thin and thick
made of protein.
• The thin filament is called
actin.
• The thick filament is called
myosin.
• Myosin grips the actin and
pulls it when the muscle
contracts
Cardiac Muscle
• Cardiac muscle is heart
muscle
– Striated but involuntary
– Always working
– All heart muscle cells have to
contract at once, so a small
patch on the heart tells the
cardiac muscles to contract
Skeletal System
• Muscles can’t cause movement without
something to PULL on
• Functions of the Skeletal System
1.
2.
3.
4.
5.
Supports the body
Protects internal organs
Provides for movement
Stores mineral reserves
Provides site for blood cell formation
Bones
• Bones are protein fibers
and calcium deposits.
– 206 bones in an adult, 215 in
an infant
– Bone cells are called
osteocytes
– Compact bone is solid
– Spongy bone is like a
network of girders, strong but
light
Bone Marrow
• Bone marrow- found within cavities of
bones
– 2 types: yellow  primarily fat cells
red  produces RBC’s, some WBC’s
and platelets
Joints
• Joints are where bones connect with each
other
• Many types of joints
• Three types of connective tissue
– Ligaments-Connect bone to bone
– Tendons-Connect muscle to bone
– Bursa-Small sacs that act as shock absorbers
Disorders
• Osteoporosis-Weakening of bones due to
calcium loss
• Arthritis-Inflammation of the joints, usually
due to the body’s own immune system