AdenosineTriphosphate (ATP)

• Animal cells cannot directly use most forms of energy
  • Most cellular processes require energy stored in the bonds of a molecule, adenosine triphosphate (ATP)
  • ATP is referred to as the energy currency of the cell

It is a nucleotide, formed from:

• the base adenine (the structure with 2 rings),
• the 5 carbon sugar deoxyribose (one ring)
• 3 phosphates

Energy is stored in the bonds between the phosphates and is released when the bonds are broken

Oxygen Transport in Blood: Hemoglobin

A.    Association & Dissociation of Oxygen + Hemoglobin

1.    oxyhemoglobin (HbO₂) - oxygen molecule bound
2.    deoxyhemoglobin (HHb) - oxygen unbound
    
H-Hb     +    O₂  <= === => HbO₂ + H+

3.    binding gets more efficient as each O₂ binds
4.    release gets easier as each O₂ is released

5.    Several factors regulate AFFINITY of O₂

a.    Partial Pressure of O₂
b.    temperature
c.    blood pH (acidity)
d.    concentration of “diphosphoglycerate” (DPG)

B.    Effects of Partial Pressure of O₂

1.  oxygen-hemoglobin dissociation curve

a.    104 mm (lungs) - 100% saturation (20 ml/100 ml)
b.    40 mm (tissues) - 75% saturation (15 ml/100 ml)
c.    right shift - Decreased Affinity, more O2 unloaded
d.     left shift- Increased Affinity, less O₂ unloaded

C.    Effects of Temperature
    
1.    HIGHER Temperature    --> Decreased Affinity (right)
2.    LOWER Temperature        --> Increased Affinity (left)

D.    Effects of pH (Acidity) 

1.    HIGHER pH    --> Increased Affinity (left)
2.    LOWER pH    --> Decreased Affinity (right) "Bohr Effect"
a.    more Carbon Dioxide, lower pH (more H+), more O2 release

E.    Effects of Diphosphoglycerate (DPG)

1.    DPG - produced by anaerobic processes in RBCs
2.    HIGHER DPG    > Decreased Affinity (right)
3.    thyroxine, testosterone, epinephrine, NE - increase RBC metabolism and DPG production, cause RIGHT shift

F.    Oxygen Transport Problems

1.    hypoxia - below normal delivery of Oxygen

a.    anemic hypoxia - low RBC or hemoglobin
b.    stagnant hypoxia - impaired/blocked blood flow
c.    hypoxemic hypoxia - poor lung gas exchange

2.    carbon monoxide poisoning - CO has greater Affinity than Oxygen or Carbon Dioxide 
 

PHYSIOLOGY OF THE BRAIN

• The Cerebrum (Telencephalon) Lobes of the cerebral cortex

   

  1. Frontal Lobe
     1. Precentral gyrus, Primary Motor Cortex, point to point motor neurons, pyramidal cells: control motor neurons of the brain and spinal cord. See Motor homunculus
     2. Secondary Motor Cortex repetitive patterns
     3. Broca's Motor Speech area
     4. Anterior - abstract thought, planning, decision making, Personality
  2. Parietal Lobe
     1. Post central gyrus, Sensory cortex, See Sensory homunculus, size proportional to sensory receptor density.
     2. Sensory Association area, memory of sensations
  3. Occipital Lobe
     1. Visual cortex, sight (conscious perception of vision)
     2. Visual Association area, correlates visual images with previous images, (memory of vision, )
  4. Temporal Lobe
     1. Auditory Cortex, sound
     2. Auditory Association area, memory of sounds
  5. Common Integratory Center - angular gyrus, Parietal, Temporal & Occipital lobes
     1. One side becomes dominent, integrats sensory (somesthetic, auditory, visual) information
  6. The Basal nuclei (ganglia)
     1. Grey matter (cell bodies) within the White matter of cerebrum, control voluntary movements
  7. Cauadate nucles - chorea (rapi, uncontrolled movements), Parkinsons: (dopamine neurons of substantia nigra to caudate nucles) jerky movements, spasticity, tremor, blank facial expression
  8. The limbic system - ring around the brain stem, emotions(w/hypothalamus), processing of olfactory information

• The Diencephalon

   

  1. The Thalamus - Sensory relay center to cortex (primitive brain!)
  2. The Hypothalamus
     1. core temperature control"thermostat", shivering and nonshivering thermogenesis
     2. hunger & satiety centers, wakefulness, sleep, sexual arousal,
     3. emotions (w/limbic-anger, fear, pain, pleasure), osmoregulation, (ADH secretion),
     4. Secretion of ADH, Oxytocin, Releasing Hormones for Anterior pitutary
     5. Linkage of nervous and endocrine systems

• The Mesencephalon or Midbrain -

   

  1. red nucleus, motor coordination (cerebellum/Motor cortex),
  2. substantia nigra
• The Metencephalon
  1. The Cerebellum -
     1. Performs automatic adjustments in complex motor activities
     2. Input from Proprioceptors (joint, tendon, muscles), position of body in Space
        1. Motor cortex, intended movements (changes in position of body in Space)
     3. Damping (breaking motor function), Balance, predicting, inhibitory function of Purkinji cells (GABA), speed, force, direction of movement
  2. The Pons - Respiratory control centers (apneustic, pneumotaxic)
     1. Nuclei of cranial nerves V, VI, VII, VIII

• Myelencephalon

   

  1. The Medulla
     1. Visceral motor centers (vasomotor, cardioinhibtory, respiratory)
     2. Reticular Formation RAS system, alert cortex to incoming signals, maintenance of consciousness, arousal from sleep
     3. All Afferent & Efferent fibers pass through, crossing over of motor tracts
  2. Corpus Callosum: Permits communication between cerebralhemispheres
• Generalized Brain Avtivity
  1. Brain Activity and the Electroencephalogram(EEG)
     1. alpha waves: resting adults whose eyes are closed
     2. beta waves: adults concentrating on a specific task;
     3. theta waves: adults under stress;
     4. delta waves: during deep sleep and in clinical disorders
  2. Brain Seizures
     1. Grand Mal: generalized seizures, involvs gross motor activity, affects the individual for a matter or hours
     2. Petit mal: brief incidents, affect consciousness but may have no obvious motor abnormalities
  3. Chemical Effects on the Brain
     1. Sedatives: reduce CNS activity
     2. Analgesics: relieve pain by affecting pain pathways or peripheral sensations
     3. Psychotropics: alter mood and emotional states
     4. Anticonvulsants: control seizures
     5. Stimulants: facilitate CNS activity
  4. Memory and learning
     1. Short-term, or primary, memories last a short time, immediately accessible (phone number)
     2. Secondary memories fade with time (your address at age 5)
     3. Tertiary memories last a lifetime (your name)
     4. Memories are stored within specific regions of the cerebral cortex.
     5. Learning, a more complex process involving the integration of memories and their use to direct or modify behaviors
     6. Neural basis for memory and learning has yet to be determined.
• Fibers in CNS
  1. Association fibers: link portions of the cerebrum;
  2. Commissural fibers: link the two hemispheres;
  3. Projection fibers: link the cerebrum to the brain stem

Cells, cytoplasm, and organelles:

• Cytoplasm consists of a gelatinous solution and contains microtubules (which serve as a cell's cytoskeleton) and organelles

• Cells also contain a nucleus within which is found DNA (deoxyribonucleic acid) in the form of chromosomes plus nucleoli (within which ribosomes are formed)

• Organelles include:

1. Endoplasmic reticulum : 2 forms: smooth and rough; the surface of rough ER is coated with ribosomes; the surface of smooth ER is not , Functions include: mechanical support, synthesis (especially proteins by rough ER), and transport
2. Golgi complex consists of a series of flattened sacs (or cisternae) functions include: synthesis (of substances likes phospholipids), packaging of materials for transport (in vesicles), and production of lysosomes
3. Lysosome : membrane-enclosed spheres that contain powerful digestive enzymes , functions include destruction of damaged cells & digestion of phagocytosed materials
4.  Mitochondria : have double-membrane: outer membrane & highly convoluted inner membrane
   1. inner membrane has folds or shelf-like structures called cristae that contain elementary particles; these particles contain enzymes important in ATP production
   2. primary function is production of adenosine triphosphate (ATP)
5. Ribosome-:composed of rRNA (ribosomal RNA) & protein , primary function is to produce proteins
6. Centrioles :paired cylindrical structures located near the nucleas , play an important role in cell division
7. Flagella & cilia - hair-like projections from some human cells
   1. cilia are relatively short & numerous (e.g., those lining trachea)
   2. a flagellum is relatively long and there's typically just one (e.g., sperm)

• • Villi  Projections of cell membrane that serve to increase surface area of a cell (which is important, for example, for cells that line the intestine)

Cardiac Control: The Cardiac Center in the medulla.

Outputs:

The cardioacceleratory center sends impulses through the sympathetic nervous system in the cardiac nerves. These fibers innervate the SA node and AV node and the ventricular myocardium. Effects on the SA and AV nodes are an increase in depolarization rate by reducing the resting membrane polarization. Effect on the myocardium is to increase contractility thus increasing force and therefore volume of contraction. Sympathetic stimulation increases both rate and volume of the heart.

The cardioinhibitory center sends impulses through the parasympathetic division, the vagus nerve, to the SA and AV nodes, but only sparingly to the atrial myocardium, and not at all to ventricular myocardium. Its effect is to slow the rate of depolarization by increasing the resting potential, i.e. hyperpolarization.

The parasympathetic division controls the heart at rest, keeping its rhythm slow and regular. This is referred to as normal vagal tone. Parasympathetic effects are inhibited and the sympathetic division exerts its effects during stress, i.e. exercise, emotions, "fight or flight" response, and temperature.

Inputs to the Cardiac Center:

Baroreceptors in the aortic and carotid sinuses. The baroreceptor reflex is responsible for the moment to moment maintenance of normal blood pressure.

Higher brain (hypothalamus): stimulates the center in response to exercise, emotions, "fight or flight", temperature.

Intrinsic Controls of the Heart:

Right Heart Reflex - Pressoreceptors (stretch receptors) in the right atrium respond to stretch due to increased venous return. The reflex acts through a short neural circuit to stimulate the sympathetic nervous system resulting in increased rate and force of contraction. This regulates output to input

The Frank-Starling Law - (Starling's Law of the Heart) - Like skeletal muscle the myocardium has a length tension curve which results in an optimum level of stretch producing the maximum force of contraction. A healthy heart normally operates at a stretch less than this optimum level and when exercise causes increased venous return and increased stretch of the myocardium, the result is increased force of contraction to automatically pump the increased volume out of the heart. I.e. the heart automatically compensates its output to its input.

An important relationship in cardiac output is this one:

Blood Flow =  D Pressure / Resistance to Blood Flow      

Respiration involves several components:

Ventilation - the exchange of respiratory gases (O₂ and CO₂) between the atmosphere and the lungs. This involves gas pressures and muscle contractions.

External respiration - the exchange of gases between the lungs and the blood. This involves partial pressures of gases, diffusion, and the chemical reactions involved in transport of O₂and CO₂.

Internal respiration - the exchange of gases between the blood and the systemic tissues. This involves the same processes as external respiration.

Cellular respiration - the includes the metabolic pathways which utilize oxygen and produce carbon dioxide, which will not be included in this unit.

Ventilation is composed of two parts: inspiration and expiration. Each of these can be described as being either quiet, the process at rest, or forced, the process when active such as when exercising.

Quiet inspiration:

The diaphragm contracts, this causes an increase in volume of the thorax and the lungs, which causes a decrease in pressure of the thorax and lungs, which causes air to enter the lungs, moving down its pressure gradient. Air moves into the lungs to fill the partial vacuum created by the increase in volume.

Forced inspiration:

Other muscles aid in the increase in thoracic and lung volumes.

The scalenes - pull up on the first and second ribs.

The sternocleidomastoid muscles pull up on the clavicle and sternum.

The pectoralis minor pulls forward on the ribs.

The external intercostals are especially important because they spread the ribs apart, thus increasing thoracic volume. It's these muscles whose contraction produces the "costal breathing" during rapid respirations.

Quiet expiration:

The diaphragm relaxes. The elasticity of the muscle tissue and of the lung stroma causes recoil which returns the lungs to their volume before inspiration. The reduced volume causes the pressure in the lungs to increase thus causing air to leave the lungs due to the pressure gradient.

Forced Expiration:

The following muscles aid in reducing the volume of the thorax and lungs:

The internal intercostals - these compress the ribs together

The abdominus rectus and abdominal obliques: internal obliques, external obliques- these muscles push the diaphragm up by compressing the abdomen.

Respiratory output is determined by the minute volume, calculated by multiplying the respiratory rate time the tidal volume.

Minute Volume = Rate (breaths per minute) X Tidal Volume (ml/breath)

Rate of respiration at rest varies from about 12 to 15 . Tidal volume averages 500 ml Assuming a rate of 12 breaths per minute and a tidal volume of 500, the restful minute volume is 6000 ml. Rates can, with strenuous exercise, increase to 30 to 40 and volumes can increase to around half the vital capacity.

Not all of this air ventilates the alveoli, even under maximal conditions. The conducting zone volume is about 150 ml and of each breath this amount does not extend into the respiratory zone. The Alveolar Ventilation Rate, AVR, is the volume per minute ventilating the alveoli and is calculated by multiplying the rate times the (tidal volume-less the conducting zone volume).

AVR = Rate X (Tidal Volume - 150 ml)

For a calculation using the same restful rate and volume as above this yields 4200 ml.

Since each breath sacrifices 150 ml to the conducting zone, more alveolar ventilation occurs when the volume is increased rather than the rate.

During inspiration the pressure inside the lungs (the intrapulmonary pressure) decreases to -1 to -3 mmHg compared to the atmosphere. The variation is related to the forcefulness and depth of inspiration. During expiration the intrapulmonary pressure increases to +1 to +3 mmHg compared to the atmosphere. The pressure oscillates around zero or atmospheric pressure.

The intrapleural pressure is always negative compared to the atmosphere. This is necessary in order to exert a pulling action on the lungs. The pressure varies from about -4 mmHg at the end of expiration, to -8 mmHg and the end of inspiration.

The tendency of the lungs to expand, called compliance or distensibility, is due to the pulling action exerted by the pleural membranes. Expansion is also facilitated by the action of surfactant in preventing the collapse of the alveoli.

The opposite tendency is called elasticity or recoil, and is the process by which the lungs return to their original or resting volume. Recoil is due to the elastic stroma of the lungs and the series elastic elements of the respiratory muscles, particularly the diaphragm.