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The body’s communication systems
help maintain homeostasis.
• A stimulus is anything that causes a response.
– Responses can be chemical, cellular, or behavioral.
1.
2.
3.
Chemical: insulin, growth hormone, adrenaline
Cellular: White Blood cells
Behavioral: Body temperature, walking into sunlight
– The nervous and endocrine systems respond to stimuli.
• The nervous system
controls thoughts, movement,
and emotion.
• The endocrine system
controls growth, development,
and digestion.
The nervous and endocrine systems
have different methods and rates of
communication.
• The nervous system works
quickly, using chemical and
electrical signals.
– divided into central nervous system
(CNS) and peripheral nervous
system (PNS)
– Central: brain & spinal cord
– Peripheral: all other nerves
spinal
chord
nerves
• The endocrine system works more slowly.
– only chemical signals
– signals move through bloodstream
– physically unconnected organs
target cell
hormone
bloodstream
receptor
not a target cell
Endocrine or Nervous?
• Rate at which your
fingernails grow?
• Blinking?
• Heart Rate?
• Hair growth?
• Knee jerk reflex?
• Amount of Insulin
Released?
• Endocrine
•
•
•
•
•
Nervous
Nervous
Endocrine
Nervous
Endocrine
Neurons are highly specialized cells.
• A neuron has three parts.
– cell body has nucleus and organelles
1 Cell body
Neurons are highly specialized cells.
• A neuron has three parts.
– cell body has nucleus and organelles
– dendrites receive impulses
2 dendrites
Neurons are highly specialized cells.
• A neuron has three parts.
– cell body has nucleus and organelles
– dendrites receive impulses
– axon carries impulses
3 axon
• Neurons have other structures to transmit signals.
– Schwann cell (affected by MS)
• Neurons have other structures to transmit signals.
– Schwann cell
– synapse
synapse
• Neurons have other structures to transmit signals.
– Schwann cell
– synapse
– terminal
axon
termin
al
Neurons receive and transmit signals.
• Resting potential means no signal is being
transmitted.
– more Na+ outside of cell
– more K+ inside of cell
• Inside of cell –
• Outside +
• An action potential is a moving electrical
impulse.
– It is generated by a stimulus.
– Na+ enters, and cell becomes
positively charged.
– K+ leaves, and area of positive
charge moves.
• A chemical signal passes between neurons.
– Impulse reaches terminal.
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lse
• A chemical signal passes between neurons.
– Impulse reaches terminal.
impu
lse
• A chemical signal passes between neurons.
– Impulse reaches terminal.
– Neurotransmitters released into synapse.
impu
lse
• A chemical signal passes between neurons.
– Impulse reaches terminal.
– Neurotransmitters released into synapse.
– Neurotransmitters stimulate next cell.
synapse
impu
lse
vesicl
es
neurotrans
recep
mitter
tor
Neuron Visual Questions (pg. 878)
1. When a neuron is at rest, what is the charge of its inner
membrane?
2. What causes an area of the inner membrane to become
positively charged?
3. How does an area of positive charge, or impulse, move
down the axon of a neuron?
4. How is the negative charge of the axon’s inner membrane
restored?
5. What happens when the impulse reaches the axon
terminal?
6. How do neurotransmitters generate an impulse in an
adjacent neuron?
• The CNS and PNS pass signals between one
another.
1.
2.
3.
4.
5.
6.
Sensory receptor generates impulse.
Impulse travels on sensory neurons
PNS passes impulse to CNS.
CNS interprets impulse.
CNS passes impulse to PNS.
PNS motor neurons stimulate a response.
The CNS processes information.
• The brain has three
parts.
– cerebrum controls
thought, movement,
emotion
– cerebellum allows for
balance
– brain stem controls
Brain
basic life functions stem
midbrain
pons
medulla
oblongata
Lobes of the Brain
• Frontal: responsible for
personality, reasoning,
judgment, coordinates
speech & voluntary
movement
• Temporal: speech
interpretation & hearing
• Occipital: Vision
• Parietal: Interprets
information from sense
of touch
• The brain stem has three parts.
– midbrain controls some
reflexes
– pons regulates breathing
– medulla oblongata controls
heart function, swallowing,
coughing
midbrain
pons
medulla
oblongata
• The spinal cord controls reflexes.
– sensory neuron sends impulse to spinal cord
– spinal cord directs impulse to motor neuron
– does not involve the brain
interneuron
motor neurons
sensory neuron
The PNS links the CNS to muscles and other organs.
• 3 Common Technologies to study the brain
– CT uses x-rays to view structure.
– MRI uses magnetic fields and radio waves to view structure.
– PET detects activity, where glucose is used, in the brain.
• Different neurotransmitters relate to different
functions.
synapse
Normal
receptor
neurotransmitter
– some stimulate impulses
– some prevent impulses
• Addiction is the physiological
need for a substance.
• Tolerance occurs when more
drug is needed to produce an
effect.
• Drugs might cause
desensitization or sensitization.
– desensitization: more
neurotransmitter leads to fewer
receptors
– sensitization: less
neurotransmitter leads to more
When the amount of neurotransmitter
becomes abnormal, the adjacent neuron
receptors.
adapts.
• Stimulants cause more action potentials
– may increase neurotransmitter in synapse
– may decrease removal of neurotransmitter in synapse
cocaine
neurotransmitter
synapse
• Depressants cause fewer action potentials.
– may produce neurotransmitter that prevent impulses
– may slow release of neurotransmitter that generates impulses
• Hormones are chemical signals that influence
cell’s activities.
– produced by glands
– travel through the circulatory system
– affects cells with matching receptors
target cell
hormone
bloodstream
receptor
not a target cell
• There are steroid hormones and nonsteroid
hormones.
– Steroid hormones enter the cell.
– Nonsteroid hormones do not enter the cell.
Steroid hormone
Steroid hormone
diffuses through the
cell membrane
Nonsteroid
hormone binds to
receptor on the cell
membrane.
Non-steroid
hormone
receptor
Steroid hormone binds
to a receptor within the
cell.
receptor
nucleus
The hormone and
receptor enter the
nucleus and bind to
DNA
DNA
Steroid hormone
causes DNA to make
proteins.
proteins
Receptor stimulates a
second messenger with
in the cell.
Second messenger
starts a series of
chemical reactions in
the cytoplasm.
second
messenger
Chemical
reactions
Second messenger
reactions activate
enzymes.
activated
enzymes
Endocrine glands secrete hormones
that act throughout the body.
• There are many glands located throughout the
body.
HYPOTHALAMUS
PITUITARY
THYROID
THYMUS
ADRENAL GLANDS
PANCREAS
FEMALE GONADS
:OVARIES
MALE GONADS : TESTES
– Hormones travel through the bloodstream to cells with
matching receptors.
The hypothalamus interacts with the nervous and endocrine
systems.
The hypothalamus is a gland found in the
brain.
– a structure of both the nervous and
endocrine systems
– produces releasing hormones,
sent to pituitary gland
• The pituitary gland is found below
the hypothalamus in the brain.
– controls growth and water
levels in blood
– Also produces releasing hormones
Negative feedback loops are necessary for homeostasis.
• Feedback compares current conditions to set ranges.
• Negative feedback counteracts change.
Negative Feedback Loop
Holding breath, CO2 levels
rise,
O2 / CO2 level returns to
normal
Control system forces
exhale, inhale
• Positive feedback increases change.
– Torn vessel stimulates release of clotting factors
platelets
blood vessel
fibrin
clot
white blood cell
red blood cell
– growth hormones stimulate cell division
Examples of feedback loops…
Negative or Positive?
1. Your energy level decreases, stomach
growls telling you need nutrition to get
your energy levels back up. NEGATIVE
2. The adrenaline rush you experience in
dangerous situations. POSITIVE
3. You do sprints for an hour and you pass
out. Your body is telling you your oxygen
level is too low. NEGATIVE
Problem Solve
#1 Given Situation. Is it an
Box 2 Given Situation.
example of negative or
positive feedback? Explain
Is it an example of
negative or positive
feedback? Explain
Box 3 Provide your own
Box 4Provide your own
example
of Negative
Feedback
example of
Positive Feedback
Problem Solve
#1
When contractions start during labor,
the hormone oxytocin is released into the
body and causes more contractions to allow
a woman to give birth.
Box 3 Provide your own
example
of Positive
Feedback
Box 2 It’s a hot day and
you start
to sweat.
Box 4Provide your own
example of
Negative Feedback
Label the Brain/Neuron
• On the brain side, label and describe the
function of the following:
– Cerebellum, Frontal Lobe, Medulla Oblongata,
Occipital Lobe, Parietal Lobe, Pituitary Gland,
Pons, Spinal Cord, Temporal Lobe
• On the neuron, label and describe the
function of the following:
– Axon, axon terminal, cell body, dendrites,
nucleus, Schwann cell