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Cells
What are living things made of?
Exam III – November 9th
Assignment 3 – Nov. 9th
Sections of chapters 4, 21, 22, 23, 27
What are living things made of?
• What are cells?
• What technological advance led to the
discovery of cells?
• What is cell theory?
Any way you slice it
Cell Theory
• All organisms are composed of cells
• The cell is the fundamental unit of life
• Cells arise from pre-existing cells
• All the cells in your body arose from one
cell (the fertilized egg)
Living things are made of cells
• Everything your body does is controlled at the
level of the cells
– Muscle cells contract, the muscle contracts
– Cells in salivary glands produce saliva, your mouth
waters
– Cells in nose sense chemicals and send your brain
the signal – chemical smells good, or bad
– Cells in your stomach produce digestive enzymes and
release them inside your stomach
– Anything you can think of in living things is controlled
at the cell level!
Cells
• Maintain a stable internal environment
– Cell membrane separates cell from it’s
external environment and controls the
movement of molecules
• Semi-permeable membrane
Cell membrane
• Fluid-Mosaic model
http://www.susanahalpine.com/anim/Life/memb.htm
Cells
• Have complex structure
– Prokaryotes (bacteria – small simple cells)
– Eukaryotes (animals, plants and fungi – larger more
complex cells)
Cells
• Prokaryotic Bacterial cells only have the one
main compartment, one membrane surrounds
the whole cell.
• Eukaryotic cells (like ours) have many small
compartments (organelles), each has it’s own
membrane.
• Why would it be advantageous to have many
small compartments?
Cells
• At a minimum, cells have a membrane,
DNA, ribosomes and cytosol
• In addition, more complex eukaryotic cells
have organelles such as:
– Nucleus
– Mitochondria
– and Chloroplasts
Cells
• Have complex structure
– Prokaryotes (bacteria – small simple cells)
– Eukaryotes (animals, plants and fungi – larger more
complex cells)
Eukaryotic cells
Plant vs. animal
• Both plant and animal cells are eukaryotic
– Plant and animal cells have same basic
structures
– Plant cells also have cell wall and chloroplasts
Eukaryotic cell
Eukaryotic cell
Prokaryotic cell
Cells
Cell analogies
•
Example: Cell is like a city
1. The cell membrane is to the cell as the
_______________________ is to the city.
2. The nucleus is to the cell as the
_______________________ is to the city.
3. The mitochondria is to the cell as the
_______________________ is to the city.
4. The ribosome is to the cell as the
_______________________ is to the city.
5. The chloroplast is to the cell as the
_______________________ is to the city.
• Inner life of a cell video – how chemicals interact to
create cell structures, state of the art, up-to-date
scientific info.
• www.youtube.com/watch?v=Mszlckmc4Hw
Physiology
The study of maintaining the status quo
“HOMEOSTASIS”
What sort of conditions must
remain constant in your body?
•
•
•
•
•
•
Temperature
Blood sugar
O2, CO2
H2O
Na+ (sodium)
K+ (potassium)
lunch
Example: blood sugar (glucose)
• Must be high enough for cells.
• Must be low enough that it isn’t lost
through urine.
• After meal, glucose is high.
Homeostasis (blood sugar)
High
Glucose
Low
Insulin
Glycogen
Fat
(stored glucose,
(stored glucose,
Easy access)
Long-term storage)
Where fat comes in
• If glycogen stores in cells are too high,
your body transforms it into fat.
• When glucose is low, you get hungry and
also break down glycogen to glucose.
• Eventually, if glycogen remains low, you
break down fat to replenish glycogen.
Ex. Body temperature
• Body is set for 98.6 F (37 C).
• How does it maintain this temperature?
• What does our body do if too cold?
– Shivering.
– Redirect blood from extremities and skin
surface to body core.
– Burn more fat for heat.
Temperature regulation
• What does our body do if too warm?
– Sweat.
– Redirect blood to surface of skin and
extremities to radiate off heat.
– Slow down metabolism
So what are components of this
feedback system?
• sensor -measures the state of the system
• integrator -the 'brain': determines the
appropriate action needed to return to the
desired state
• effector -instructed by integrator to affect
the state of the system
Components in temperature
system
• sensor: nerves
• integrator: brain
• effector: circulatory system, muscles, etc.
• Analogous to a regulating temperature in a
building.
– sensor: thermometer in thermostat
– integrator: thermostat computer
– effector: switch to turn heat or A/C on and off
Negative Feedback Systems
• Body temperature and blood sugar
• tends to maintain constant conditions
• it operates to correct the system when
there is a change
• called negative feedback since it causes a
reversal of the changes that are causing
the state of the system to change.
• In this context, negative does not mean
bad. Homeostasis is good.
Positive Feedback
• In contrast to negative feedback, a
positive feedback system does not
counteract changes, but rather it amplifies
them.
• It leads to a change in the system.
• The dynamics of a positive feedback
system tend to push the state of the
system further from the starting point,
either up or down.
Examples of positive feedback
• Childbirth
The Ocotillo:
-Grows leaves just after
a rain.
-Photosynthesizes
quickly with its nonwaxy leaves, losing a
lot of water in the
process.
-When water levels get
too low, it drops its
leaves and waits for
the next rain.
The water conservation
mechanism in this plant
is an example of a:
a. Negative feedback
mechanism
b. Positive feedback
mechanism
The effector is:
a. the mechanism by which the
plant measures its water
balance
b. the mechanism that holds the
leaves on the plant
c. the mechanism by which the
plant makes the decision on
whether to send out leaves or
drop the leaves
d. the mechanism by which the
plant sends out leaves
e. both b and d
Positive or negative feedback?
• A female becomes amenorheic (stops the
menstrual cycle) when her body is deprived of
food.
• A runner breathes more heavily when
exercising.
• The hormone adrenalin is released by your
adrenal gland when you feel threatened, it
causes your heart to beat faster which makes
you feel anxious, which releases more
adrenalin.
Homeostasis
• The purpose of most of our bodies
functions is to maintain homeostasis.
• We will spend time on different body
systems (organ systems) to understand
how they help maintain a stable internal
environment. Physiology.
• We will also study the anatomy of those
systems. What are the parts and how do
they work.
Circulatory system
Circulatory System
• Anatomy
– Blood
– Vessels
– Heart
• Physiology
– What is the purpose of the circulatory system?
– How does it maintain homeostasis?
Circulatory system
• Blood flows in a circular
path: heart to arteries to
capillaries to veins to
the heart.
• Right side of heart to
lungs to left side of heart.
• Left side of heart to
body and then back to
right side of heart.
• Capillaries not visible,
distribute blood to cells
Observational evidence
• One-way valves
between atria and
ventricles.
• Heart  lungs 
heart (pulmonary
circuit)
• Heart  body 
heart (systemic
circuit)
Comparative evidence
• In animals with 4-chambered heart, left
ventricles is much larger then right one.
• It must, to deliver the blood further.
• Compared hearts of all vertebrates.
Blood Vessels
• If the heart is the body’s “pump,” then the
“plumbing” is the system of arteries, veins,
and capillaries
– Arteries carry blood away from the heart
– Veins carry blood toward the heart
– Capillaries allow for exchange between the
bloodstream and tissue cells
Blood Flow in our bodies:
Heart -> Arteries -> Capillaries -> Veins -> Heart
From heart
To heart
Epithelium
Valve
Epithelium
Epithelium
Smooth
muscle
Connective
tissue
Capillary
Smooth
muscle
Connective
tissue
Artery
Vein
Arteriole
Venule
Figure 23.8
Blood vessels
• What is the purpose of capillary beds?
– Supply the tissues and cells the nutrients they
need
– Take away from tissues and cells the wastes
they produce
Capillary
Red blood cell
(a) Capillaries
Figure 23.9a
• The walls of capillaries are thin and leaky
– As blood enters a capillary at the arterial
end, blood pressure pushes fluid rich in
oxygen, nutrients, and other substances
into the interstitial fluid
– At the venous end of the capillary, CO2
and other wastes diffuse from tissue cells
and into the capillary bloodstream
Tissue cell
Arterial
end of
capillary
Diffusion of O2
and nutrients
out of capillary
and into tissue
cells
Interstitial fluid
(b) Chemical exchange
Diffusion of
CO2 and
wastes out
of tissue
cells and
into capillary
Venous
ends of
capillary
Figure 23.9b
Gas transport
• Oxygen is poorly soluble in blood, so is
helped by the protein hemoglobin.
• Hemoglobin attaches to O2 when O2 is in
high concentration (in lungs)
• Detaches when O2 is in low concentration
(body)
• Some things attach to Hemoglobin and
won't come off (CO, Hg, cyanide)
Nutrient and Gas Exchange
• Nutrients in your blood stream enter the
blood stream at the capillaries in your
intestine (digestive system)
• Oxygen in your blood stream enters at the
capillaries in your lungs
• Carbon dioxide waste leaves your blood
stream at the lungs
• Other wastes are filtered out of your blood
in the kidneys.
Respiratory System
a.k.a “windpipe”
Gas Exchange in the Lungs
To heart
From heart
Oxygen-poor
blood
Oxygen-rich
blood
• Bronchioles dead-end
in clusters of air sacs
called alveoli, which
are the sites of gas
exchange with the lung
capillaries
Bronchiole
Alveoli
Blood capillaries
Figure 23.19
Gas Exchange at the Body Cells
cell
Arterial end
of capillary
Diffusion of
Diffusion of O2
and nutrients
out of capillary
and into tissue
cells
CO2 and
wastes out of
tissue cells
and into
capillary
Venous ends
of capillary
Figure 23.9b
• http://www.northarundel.com/aniplayer/
– Lungs and Breathing: Gas exchange
CO2 in exhaled air
O2 in inhaled air
Alveoli
Capillaries of
lung
CO2–rich,
O2–poor
blood
O2–rich,
CO2–poor
blood
Heart
Tissue capillaries
Tissue cells throughout body
Figure 23.22
Respiratory System
• the diaphragm
contracts, changing
from parachuteshaped to flat
• this sucks air into
your body, down
through your chest
cavity and into your
lungs
• Bottle/Balloon model
Digestive & Respiratory System:
The Big Picture
• Q: What do we do with the O2 that we
breate in?
• A: We use it to oxidize the reduced
carbon molecules that we eat (glucose,
fats…otherwise known as “food”).
• In other words, we’re using it to stoke the
fire, the controlled burn, that we call our
metabolism.
Dysfunction of the circulatory system:
Hypertension (high blood pressure) is the
main cause of heart disease. What causes
hypertension?
•
•
•
•
•
•
Heredity
Race
Exercise
Obesity
Smoking
Alcohol
• Diet: sodium
• Diet: cholesterol
Cholesterol
• Two types of protein
carriers affect
cholesterol.
• LDL: ‘bad’ carrier:
carries cholesterol in
blood and deposits it
on arterial walls.
• HDL: ‘good’ carrier:
picks up cholesterol
from around the body
and carries to your
liver to be destroyed.
• Your liver can modify
cholesterol levels and
synthesizes cholesterol
if necessary.
• Excess cholesterol gets
deposited on arterial
walls by LDL, forming
plaques. Extensive
plaque build-up is
atherosclerosis
(hardening of the
arteries).
What affects LDL/HDL levels?
• What raises LDL?
• Saturated fat
• Partiallyhydrogenated fats
•
•
•
•
What raises HDL?
Some nuts
Exercise
Unsaturated fats
Problems due to high blood
pressure
• Stroke: blood vessel in
the brain is blocked by a
clot (cerebral ischemia) or
bursts due to high blood
pressure (cerebral
hemorrhage).
• A stroke is more likely if
vessels are constricted
and less flexible due to
atherosclerosis
(cholesterol and fatty
plaques on artery walls).
• Heart attack: clot plugs
coronary artery leading to
heart, depriving the heart
of oxygen.
• Bypass operations use
vein from your leg to
bypass clogged coronary
artery feeding your heart.
• In angioplasty, a small
tube with a little balloon is
inserted into your blood
vessels and guided into
your clogged arteries.
Nervous System
ANIMAL NERVOUS SYSTEMS
• The nervous system
– Forms a communication and coordination network
throughout an animal’s body for RAPID communication
A neuron (nerve cell)
Central nervous
system (CNS)
Two main divisions:
• The central nervous
system (CNS)
– Consists of the brain
and the spinal cord
• The peripheral
nervous system
(PNS)
– Is made up mostly of
nerves that carry
signals into and out
of the CNS
Brain
Spinal cord
Peripheral
nervous
sysem (PNS)
Peripheral N. S. - Sensory and
Motor Neurons
• Sensory
neurons
– Convey sensory
input (carry
signals into the
CNS)
• Motor neurons
– Convey motor
output (carry
signals out of the
CNS)
Central
nervous
system (CNS)
Brain
Spinal cord
Peripheral
nervous
system (PNS)
A Typical Nervous System
Response
Sensory input
Sensory neuron
Integration
Sensory receptor
Motor neuron
Motor output
Brain & spinal cord
Effector
Peripheral nervous
system (PNS)
Central nervous
system (CNS)
Figure 27.2
Neurons – A single nerve cell
Signal direction
Dendrites
Axon
Signal direction
Synapse
Nucleus
Myelin sheath cells
surrounding the axon
Figure 27.3
Two types of cells in nervous tissue
• Neuron cells – made of Dendrites and
Axons
– Dendrites receives an incoming message from
other cells and conveys the information toward
the cell body and axon
– The axon conducts the signal toward another
neuron or an effector (which performs the
body’s responses to motor output)
• Supporting (Glial) cells (example: myelin
sheath)
– Protect, insulate, and reinforce neurons
The Action Potential – when a neuron “fires”
• Action potentials in a neuron are all-or-none
events, like a gunshot (either happens or it
doesn’t).
(bang!)
A stimulus
– Is any factor that causes a nerve signal (an
action potential) to be started and sent.
Passing a Signal from
one Neuron to another
• Synapses
– Are the relay points between two neurons, or
between a neuron and an effector cell, which
performs the body’s responses to motor output
– Rely on neurotransmitters to carry information
from one nerve cell to another
Sending neuron
Sending
neuron
Vesicles
1
Action
potential
arrives
Synapse
Synaptic knob
2
Vesicle fuses
with plasma
membrane
Synaptic
cleft
Receiving
neuron
Receiving
neuron
3
Neurotransmitter
is released into
synaptic cleft
4
Neurotransmitter
binds to receptor
Neurotransmitter
Ion
channels molecules
Neurotransmitter broken
Neurotransmitter
down and released
Receptor
5 Ion channel
opens and
triggers a
new action
potential
Ions
6 Ion
channel
closes
Figure 27.6
Neurotransmitters
• A wide variety of small molecules can act
as neurotransmitters
Drugs and the Brain
• Many drugs act at synapses
– By increasing or decreasing the normal effects
of neurotransmitters
• These drugs include:
– Caffeine, nicotine, alcohol, various prescription
drugs (antidepressants), cocaine, LSD, and
marijuana, to name a few
The Nervous System
Central Nervous System
Brain
Spinal
Cord
Peripheral Nervous System
Sensory
Neurons
Motor
Neurons
Somatic
Nervous
System
Autonomic
Nervous
System
Types of Motor Neurons and
their functions
• The motor neurons consist of two systems:
– The somatic nervous system carries signals to
skeletal muscle effectors
This is voluntary- such as you sending nerve
signals to tell yourself to move your arms, lets,
etc.
– The autonomic nervous system controls
smooth and cardiac muscles and the organs
and glands of various body systems
(involuntary)
THE SENSES
• Sensory structures
– Gather information and pass it on to the CNS
Sensory Input
• Sensory transduction
– Is the conversion by sensory receptors of stimuli
into electrical signals
Sugar molecule
• Sensory receptor cells in a taste bud
Ion
Receptor
Sensory receptor
cell membrane
Sugar
molecule
3 Receptor potential
2 Sugar
binding
Taste bud
Tongue
Ion
channels
Sensory
receptor
cells
Sensory
receptor
cell
in sensory receptor
cell
Neurotransmitter
molecule
Sensory
neuron
Sensory neuron
1 Taste bud anatomy
Action potential
4 Synapse with sensory
neuron
Figure 27.15
The Muscular System
• Skeletal muscles
– Pull on bones to produce movements
Biceps
contracted
Biceps relaxed
Triceps
relaxed
Triceps
contracted
Tendon
Figure 27.29
The Cellular Basis of Muscle
Contraction
Muscle
• Skeletal muscle
– Consists of
bundles of
parallel muscle
fibers
Bundle of
muscle fibers
Nuclei
Single muscle fiber (cell)
Myofibril
Light
band
Dark band
Z disc
Sarcomere
Thick filaments
(myosin)
Light
band
Dark band
Light
band
Thin filaments
(actin)
Z disc
Sarcomere
Z disc
Figure 27.30
Spinal cord
Motor
unit 1
Motor
unit 2
• A motor unit
– Consists of a
neuron and all
the muscle
fibers it
controls
Nerve
Motor neuron
cell body
Motor
neuron
axon
Neuromuscular
junctions
Muscle
fibers
(cells)
Nuclei
Muscle
Tendon
Bone
Figure 27.33
SUMMARY OF KEY CONCEPTS
• Organization of Nervous Systems
Sensory
receptor
Sensory input
Integration
Effector
Motor output
PNS
CNS
Visual Summary 27.1