35-1 Human Body Systems
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Specialized cell
Epithelial tissue
Connective tissue
Nervous tissue
Muscle tissue
Homeostasis
Feedback inhibition
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The levels of organization in a multicellular
organism include cells, tissues, organs and
organ systems
 Cells  tissues  organs  organ systems
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A cell is the basic unit of structure and
function in living things
 Specialized cells are uniquely suited to perform a
particular function
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A group of cells that perform a single
function
1. Epithelial tissue – covers interior and exterior
surfaces
2. Connective tissue – provides support and
connects parts
3. Nervous tissue – neurons that transmit
impulses throughout body
4. Muscle tissue – movement (smooth, cardiac,
skeletal)
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A group of different types of tissues that
work together to perform a single function
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List the levels of organization of the human
body starting with the smallest.
Give an example of each level.
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A group of organs that perform closely
related functions
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Students know how the feedback loops in the
nervous and endocrine systems regulate
conditions in the body
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Organ systems are working constantly to
maintain a controlled, stable environment
“keeping things in balance.”
Internal conditions are kept constant despite
changes in the external environments
Maintained by FEEDBACK LOOPS
Feedback inhibition: process in which a
stimulus produces a response that opposes
the original stimulus
Requires all organ systems to work together at
all times
1.
2.
3.
4.
What are the levels of organization in the
human body?
The process that keeps internal conditions
relatively constant despite changes in the
external environment is called______.
The basic unit of structure and function in
living things is called a _________.
A group of different types of tissues that
work together to perform a single function
is called an_________.
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Students know the functions of the nervous
system and the role of neurons in
transmitting electrochemical impulses
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Neuron
Cell body
Dendrite
Axon
Myelin sheath
Resting potential
Action potential
Threshold
Synapse
neurotransmitter
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The nervous system controls and
coordinates functions throughout the body
and responds to internal and external
stimuli
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Neurons – cells of the nervous system that
transmit electrical signals (called impulses) to
carry messages throughout the body
1.
2.
3.
Sensory Neurons –
carry impulses from the
sense organs to the
spinal cord and brain
Interneurons –
connect sensory and
motor neurons
(integration/processing
)
Motor Neurons – Carry
impulses from the brain
and spinal cord to the
muscles or glands
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Dendrites – extensions
that carry impulses from
the environment or other
neurons to the cell body
Cell body – largest part of
the neuron that contains
the nucleus and most of
the cytoplasm
Axon – fiber extension
that carries impulses away
from the cell body
Myelin sheath – surrounds
and insulates the axon
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The Resting Neuron (Resting Potential)
 Not transmitting an impulse
 Negative inside; positive outside
 Sodium (Na+) out and Potassium (K+) in
▪ K+ has a tendency to leak out which is why the inside is
more negative
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The Moving Impulse (Action Potential)
 Neuron receives stimulus to start an impulse
 An impulse begins when a neuron is stimulated by
another neuron or by the environment
 Travels down the axon towards the axon terminals
 Na+ flow inside; inside becomes more positive and
outside becomes more negative
▪ This reversal of charges is the nerve impulse, Action Potential
 Restores back to resting potential by allowing K+ to
flow out
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Threshold
 A stimulus must be strong enough to cause a
neuron to transmit an impulse
 The minimum level of a stimulus that is required
to activate a neuron is called a threshold
 Any stimulus stronger than the threshold will
produce an impulse; weaker than the threshold
will not produce an impulse
 All-or-none principal
1.
2.
3.
4.
What is homeostasis?
Which organ systems in the human body
work together to maintain homeostasis?
What is the insulating membrane that
surrounds some axons called?
What are the structures that carry impulses
to the cell body called?
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Location (gap) at which a neuron can
transfer an impulse to another cell
Synaptic cleft – separates the axon terminal
from the dendrites of adjacent cell
Axon terminals contain Neurotransmitters
Neurotransmitters are chemicals used by a
neuron to transmit an impulse across the
synapse to another cell
What are the parts of a neuron?
The __________ __________ occurs when no
impulse is being transmitted and the inside of
the neuron is more negative than the outside.
3. The minimum level of a stimulus that is
required to activate a neuron is called the
_______
4. The reversal of charges from negative to
positive is called an _________ ________ (aka
nerve impulse)
5. __________ are chemicals used by a neuron to
transmit impulses across a synapse.
1.
2.
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35-1 Section Assessment #1-5
35-2 Section Assessment #1-5