Cells and physiology

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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
  – 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!
• 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
• Have complex structure
  – Prokaryotes (bacteria – small simple cells)
  – Eukaryotes (animals, plants and fungi – larger more
    complex 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

• Why would it be advantageous to have many
  small compartments?
• 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
• 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
  – Plant cells also have cell wall and chloroplasts
 Eukaryotic cell

                   Eukaryotic cell

Prokaryotic cell
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.


The study of maintaining the status quo

      What sort of conditions must
     remain constant in your body?
•   Temperature
•   Blood sugar
•   O2, CO2
•   H2O
•   Na+ (sodium)
•   K+ (potassium)
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)


 Glucose               Glycogen              Fat

Low                  (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
• sensor: nerves
• integrator: brain
• effector: circulatory system, muscles, etc.

• Analogous to a regulating temperature in a
  – 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
• 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          The water conservation
  quickly with its non-    mechanism in this plant
  waxy leaves, losing a    is an example of a:
  lot of water in the      a. Negative feedback
  process.                 mechanism
-When water levels get     b. Positive feedback
  too low, it drops its    mechanism
  leaves and waits for
  the next rain.
The effector is:
a. the mechanism by which the
   plant measures its water
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
• A runner breathes more heavily when
• 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
• 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
• Heart  lungs 
  heart (pulmonary
• Heart  body 
  heart (systemic
       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

                  muscle                             Smooth
                    Connective       Capillary
                    tissue                       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
  – Take away from tissues and cells the wastes
    they produce

                     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

                                              Diffusion of
     Arterial                                 CO2 and
     end of               Diffusion of O2     wastes out
     capillary            and nutrients       of tissue
                          out of capillary    cells and
                          and into tissue     into capillary

  Interstitial fluid                         ends of

(b) Chemical exchange                                          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
• 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


• Bronchioles dead-end
  in clusters of air sacs
  called alveoli, which
  are the sites of gas
  exchange with the lung
                                                     Blood capillaries

                                                               Figure 23.19
Gas Exchange at the Body Cells


                                      Diffusion of
   Arterial end                       CO2 and
   of capillary   Diffusion of O2     wastes out of
                  and nutrients       tissue cells
                  out of capillary    and into
                  and into tissue     capillary

                                     Venous ends
                                     of capillary

                                                      Figure 23.9b
  – Lungs and Breathing: Gas exchange
 CO2 in exhaled air                    O2 in inhaled air


                      Capillaries of

CO2–rich,                                           O2–rich,
O2–poor                                             CO2–poor
blood                                               blood
                      Tissue capillaries

                                              Tissue cells throughout body
                                                                    Figure 23.22
         Respiratory System
• the diaphragm
  contracts, changing
  from parachute-
  shaped to flat
• this sucks air into
  your body, down
  through your chest
  cavity and into your
• 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
      Dysfunction of the circulatory system:
     Hypertension (high blood pressure) is the
    main cause of heart disease. What causes
•    Heredity            • Diet: sodium
•    Race                • Diet: cholesterol
•    Exercise
•    Obesity
•    Smoking
•    Alcohol
• Two types of protein     • Your liver can modify
  carriers affect            cholesterol levels and
  cholesterol.               synthesizes cholesterol
• LDL: ‘bad’ carrier:        if necessary.
  carries cholesterol in   • Excess cholesterol gets
  blood and deposits it      deposited on arterial
  on arterial walls.         walls by LDL, forming
• HDL: ‘good’ carrier:       plaques. Extensive
  picks up cholesterol       plaque build-up is
  from around the body       atherosclerosis
  and carries to your        (hardening of the
  liver to be destroyed.     arteries).
 What affects LDL/HDL levels?
• What raises LDL?    •   What raises HDL?
• Saturated fat       •   Some nuts
• Partially-          •   Exercise
  hydrogenated fats   •   Unsaturated fats
       Problems due to high blood
• Stroke: blood vessel in       • Heart attack: clot plugs
  the brain is blocked by a       coronary artery leading to
  clot (cerebral ischemia) or     heart, depriving the heart
  bursts due to high blood        of oxygen.
  pressure (cerebral            • Bypass operations use
  hemorrhage).                    vein from your leg to
• A stroke is more likely if      bypass clogged coronary
  vessels are constricted         artery feeding your heart.
  and less flexible due to      • In angioplasty, a small
  atherosclerosis                 tube with a little balloon is
  (cholesterol and fatty          inserted into your blood
  plaques on artery walls).       vessels and guided into
                                  your clogged arteries.
Nervous System
• The nervous system
  – Forms a communication and coordination network
    throughout an animal’s body for RAPID communication

  A neuron (nerve cell)
                            Central nervous   Peripheral
                            system (CNS)      nervous
                                              sysem (PNS)

Two main divisions:          Brain

• The central nervous        Spinal cord

  system (CNS)
  – Consists of the brain
    and the spinal cord
• The peripheral
  nervous system
  – Is made up mostly of
    nerves that carry
    signals into and out
    of the CNS
Peripheral N. S. - Sensory and
       Motor Neurons

• Sensory                nervous           Peripheral
                         system (CNS)      nervous
                                           system (PNS)

  neurons                    Brain
                             Spinal cord
  – Convey sensory
    input (carry
    signals into the
• Motor neurons
  – Convey motor
    output (carry
    signals out of the
A Typical Nervous System
                     Sensory input

                      Sensory neuron
Sensory receptor

                      Motor neuron
                       Motor output

                                        Brain & spinal cord

                   Peripheral nervous      Central nervous
                     system (PNS)           system (CNS)       Figure 27.2
   Neurons – A single nerve cell
Signal direction   Dendrites

                    Axon                Signal direction   Synapse


                           Myelin sheath cells
                           surrounding the axon

                                                                Figure 27.3
Two types of cells in nervous tissue
• Neuron cells – made of Dendrites and
  – 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
  – 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

  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                1
Sending                                                 Action
neuron                            Vesicles              potential
                             Synaptic knob                                 Synapse

                                           2               3
                                        Vesicle fuses   Neurotransmitter
                                        with plasma     is released into
                                        membrane        synaptic cleft

Receiving                    Synaptic
neuron                       cleft                                             4
                            Receiving                                binds to receptor
                                       Ion        Neurotransmitter
                                       channels molecules
                                 Neurotransmitter            Neurotransmitter broken
                            Receptor                         down and released

                                Ions                                            6 Ion
            5 Ion channel
              opens and                                                           channel
              triggers a                                                          closes
              new action

                                                                                     Figure 27.6

• 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   Peripheral Nervous System

                         Sensory         Motor
   Brain      Spinal     Neurons         Neurons
                                   Somatic   Autonomic
                                   Nervous    Nervous
                                   System     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,
  – The autonomic nervous system controls
    smooth and cardiac muscles and the organs
    and glands of various body systems
               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

                                 Sensory receptor
                                 cell membrane                     Ion
                                    Sugar                        channels
                                    molecule                        3 Receptor potential
                                                    2 Sugar
                                                      binding          in sensory receptor
                   Taste bud                                           cell
                                     Sensory        Sensory
                                     receptor       receptor
          Tongue                     cells          cell                      Neuro-

                               Sensory neuron                  Action potential

                   1 Taste bud anatomy              4 Synapse with sensory

                                                                              Figure 27.15
            The Muscular System
• Skeletal muscles
 – Pull on bones to produce movements


                                              Biceps relaxed

 Triceps                         Triceps
 relaxed                         contracted
                                                          Figure 27.29
The Cellular Basis of Muscle

• Skeletal muscle
 – Consists of         Bundle of
                       muscle fibers

   bundles of          Single muscle fiber (cell)

   parallel muscle           Myofibril

   fibers                                     band     Dark band
                                                                   Z disc


                                          Light                    Light
                                                       Dark band
                                          band                     band
                     Thick filaments
                     Thin filaments

                                 Z disc                                     Z disc   Figure 27.30
                     Spinal cord
                                         Motor    Motor
                                         unit 1   unit 2

• A motor unit
 – Consists of a                   Nerve

   neuron and all   Motor neuron
                    cell body
   the muscle                          axon

   fibers it             Neuromuscular             Muscle
                         junctions                 fibers
   controls                                        (cells)




                                                             Figure 27.33
• Organization of Nervous Systems
     receptor   Sensory input


     Effector   Motor output

                 PNS            CNS
                                         Visual Summary 27.1

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