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Human Physiology
Chapter 12: the study of how living things work
Barron’s Essential 5: #3
Molecules, cells, and organs coordinate
activities for the fitness of the organism as
a whole.
Digestion
A.) Digestion
Is the breakdown, whether mechanical or chemical, of our food,
macromolecules, into smaller useable and absorbable form
B.) Absorption
Diffusion of broken down
molecules into body cells
C.) Egestion
Removal of undigested
waste
1. Mouth
2. Esophagus
Digestive System
3. Stomach
4. Duodenum
5. Latter Small
Intestines
6. Large
Intestines
7. Rectum
8. Anus
http://resources.teachnet.ie/farmnet/Digestive.htm
1. Mouth
Mechanical breakdown of food with
chewing
Chemical breakdown with initiation of
starch breakdown by salivary
amylase secreted by salivary
glands
Note: Specialization of teeth; Incisors
for cutting, Canines for tearing,
Premolars and Molars for grinding
2. Esophagus
Movement of chewed food (Bolus)
to stomach by involuntary muscle
contractions known as Peristalsis
http://resources.teachnet.ie/farmnet/Digestive.htm
3. Stomach
Mechanical digestion in churning
Chemical digestion of proteins
Note: Different types of cells in the
Stomach that coordinate for protein
digestion:
i.) Chief cells secrete inactive
Pepsinogen
ii.) Parietal cells secrete hydrochloric
acid in which providing a pH of
2-3 in the stomach environment
to activate pepsinogen into pepsin
http://resources.teachnet.ie/farmnet/Digestive.htm
.
.
.
4. Duodenum
Complete digestion of molecules
in first 12 inches of small intestines
Note:
Pancreatic amylases hydrolyze
starch and glycogen in maltose
Bile, from liver, stored in gall
bladder emulsifies fat into fat
droplets for further digestion
Lipases breaks down fat
completely
Peptidases, such as trypsin or
chymotrypsin breaks down proteins
Nuclease hydrolyzes nucleic acids
http://resources.teachnet.ie/farmnet/Digestive.htm
5. Small Intestines
Absorption of molecules by villi and
microvilli fingerlike projections to
optimize surface area
Note:
Amino acids, vitamins, and
monossacharides are absorbed
into capillary network of villus
Fatty acids and glycerol go into
lacteal which leads into the
lymphatic system as a small vessel
6. Large Intestines
Responsible for egestion, vitamin
production and removal of excess
water (approx. 90%)
http://resources.teachnet.ie/farmnet/Digestive.htm
Note: Undigested waste is stored in rectum and eliminated through anus as
feces
Hormones Regulating
Digestive System
Hormone
Site of Production
Effect
Gastrin
Stomach wall
Stimulates sustained
secretion of gastric juice
Secretin
Duodenum wall
Stimulates pancreas to
release bicarbonate to
neutralize acid in
duodenum
CCK (Cholecystokinin)
Duodenum wall
Stimulates pancreas to
release pancreatic
enzymes and gall
bladder to release bile
into small intestine
Respiratory System
Main function is for Gas Exchange
(of O2 and CO2 for cell use)
Air Pathway:
1. Nasal Cavity-moistens, warms, and
filters air
2. Larynx
3. Trachea
4. Bronchi
5. Bronchiole
6. Alveoli- diffusion of respiratory
gases
Note: Rib cage expands,
diaphragm contracts and lowers,
and chest cavity (thoracic cavity)
expands which draws air in by
negative pressure
http://antranik.org/the-respiratory-system/
http://blog.vixra.org/2012/02/07/stop-rumours/
Detouring... To fully understand the
respiratory system itself and its role within
the body, we must take recall the
Circulatory System
Circulatory System
A closed circulatory system in humans has the function of transporting
nutrients, gas exchange, and taking away toxic waste through the medium
of blood circulation.
Note: The system consists of the heart, arteries, veins, and capillaries
Arteries-carry blood away from heart; thick walls of elastic smooth muscle
Veins-carry blood back to heart by valves and skeletal muscle contractions that
propels blood to move
Capillaries-allow for diffusion of nutrients and wastes between cells and blood
Content of Blood
Carries
hemoglobin and
oxygen; no
nucleus, 120 day
life span; formed
in bone marrow
and recycled in
liver
Fight infection;
formed in the bone
marrow; die
fighting infection,
pus; B
lymphocytes
produce antibodies
Liquid portion;
contains clotting
factors,
hormones and
antibodies,
dissolved gases,
nutrients, and
wastes.
Maintains proper
osmotic potential.
Cell
fragments;
formed in
bone marrow;
clots blood
[Side] Blood Clotting
• Clotting factors from platelets
• Anticlotting factors in plasma to prevent
thrombus formation
Damaged Tissue->Thomboplastin + Ca2+>Prothrombin (inactive) -> Thrombin
(active) ->Fibrinogen (inactive)->
Fibrin (Clot) (Active)
Heart
Composed of 4 chambers: two atria,
two ventricles; right or left ventricle or
atrium
Note: Cardiac muscle cells can
contract even when removed from heart
--Own innate pacemaker, sinoatrial node
S AA V
http://www.heartandstroke.com/site/c.ikIQLcMWJtE/b.3532069/
SA node then to atrioventricular (AV)
node to contract
Note2: Electrical impulses travel through cardiac and body tissues, where can be
detected by electrocardiogram (EKG)
Pathway of Blood
Right atrium
Right atrioventricular
valve(tricuspid)
Right ventricle
Pulmonary semilunar valve
Pulmonary artery
Lungs (Pulmonary circuit)
Pulmonary vein
Left atrium
Bicuspid (left AV) valve
Left ventricle
Aortic semilunar valve
Aorta
Systemic circuit
http://www.tutorvista.com/content/biology/biology-ii/transportation/circulation.php
Note: Systemic circuit consists of coronary circulaiton, renal circulation, and
hepatic circulation.
Going back...
The medulla in the brain contains the breathing control center—sets rhythm of
breathing and monitors CO2 levels in blood by sensing changes in pH.
CO2 is the by-product of cellular respiration, dissolves in blood to form:
Carbonic Acid
Therefore, higher [CO2], lower pH
Blood pH <7.4 causes medulla to increase rate of breathing
--There are O2 sensors (chemoreceptors) to a lesser degree
Continuing Internal Respiration
Hemoglobin
Oxygen loosely carries 4 oxygen molecules
Unique in having allosteric properties but
also exhibits cooperativity
Once binds to an O2 molecule, it changes
conformation to allow other oxygen molecules
to better bind
A drop in pH alters affinity
for oxygen. This is known as the Bohr shift. CO2 emitted by actively respiring cells
induces an acidic environment as CO2 dissolves to form carbonic acid. As the
hemoglobin approaches to a a more acidic environment, it will release its oxygen
into the cell where needed.
Transport of Carbon Dioxide
Reversible blood buffering carbonic acid-bicarbonate ion system
Excretory System
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Functional unit of the kidney is the nephron
Consists of a cluster of capillaries, the glomerulus, sits inside Bowman’s capsule, and connects to the renal tubule
Nephron carries out filtration, secretion, reabsorption, and excretion
Filtration is passive and nonselective.
Specialized cells in Bowman’s capsule modified into podocytes and along with slit pores, increase the rate of
filtration
Everything small enough to diffuse out of the glomerulus includes glucose, salts, vitamins, waste such as urea,
and other small molecules
Filtrate travels into the proximal tube
Secretion is active and highly selective
Occurs in proximal and distal tubules
Uptake of certain drugs and toxic molecules, secretes ammonia to neutralize the acid
Reabsorption is passive, active, and selective.
Water and solutes are transported back into the body
Process occurs in the proximal convoluted tubule and loop of Henle and collecting tubule
Loop of Henle acts as countercurrent exchange mechanism to maintain steep salt gradient surrounding the loop
Excretion is removal of metabolic wastes, urines passes through the ureter to the urinary bladder and passes out
the body via the urethra.
Aldosterone is hormone released by the adrenal glands in response to a decrease in blood pressure.
ADH, vasopressin, produced by the hypothalamus is stored and released from the posterior pituitary in response
to dehydration.
Nervous System
• Central nervous system consists of the brain and
spinal cord.
• Peripheral nervous system consists of all nerves
outside the CN
• Neuron consists of a cell body which contains the
nucleus, dendrites and axons
• Dendrites are sensory and receive oncoming
messages
• Axons transmit an impulse outward to another cell
• Axons wrapped in a fatty myelin sheath formed by
Schawnn cells
• Sensory neurons receive initial stimulus
• Motor neuron stimulates effectors
• Internueron transfers information directly
to the motor neuron or to the brain for
processing
• Reflex arc is inborn, automatic, and
protective
• Sensory neuron transmits an impulse to
the interneuron in the spinal cord
Neurotransmitters
http://txtwriter.com/Backgrounders/Drugaddiction/drugs1.html
• All living cells exhibit a membrane potential
• Cytoplasm(negatively charged) and extracellular
fluid(positively fluid)
• Stimulus must be enough to overcome the resting potential
• Sodium ion-gated channel, results in depolarized and
easier for the nerve to fire
• Potassium ion-gated channel results in hyperpolarization,
harder for neuron to fire
• Action potential generated in the axon of the neuron
• Sodium channels and potassium channels open
• Wave of depolarization reverses the polarity of the
membrane
• Sodium-potassium pump restores the membrane to its
original polarized condition, refractory period, neuron
cannot respond to stimulus
• The body distinguishes strong and weak stimulus by the
frequency of action potentials
• Impulse crosses a synapse chemically
• Cytoplasm at the terminal branch of the presynaptic neuron
contain many vesicles that contain molecules of
neurotransmitter
• Depolarization cause Ca++ ions to rush through calciumgated channels
• Neurotransmitter released by exocytosis, and bind with
receptors on the postsynaptic side
• Neurotransmitter release into the synapse is destroyed by
esterase
• Neurotransmitter at neuromuscular junction is acetylcholine,
others are serotonin, epinephrine, norepinephrine, and
dopamine
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Cerebrum
Learning, emotion, memory, perception
Cerebellum
Coordinates movement and balance
Receives sensory information
Brainstem
Controls several automatic homeostatic functions, breathing, heart and blood vessel
activity
Integrates sensory information
Sensory phase of vision
Photons of light pass through the lens which focuses light on retina
Light is absorbed by photoreceptors when it strikes the retina in neurons – rods(
black and white) and cones( color vision)
Stimulation of retinal activates a G protein-signaling mechanism that alters the
membrane potential and closes Na+ channels
Each molecule of photoexcited rhodopsin activates enzyme molecules which activate
cGMP closing Na+ channels and causing impulse to be sent to the optic nerve and
cortex of the brain where messages are interpreted
Another opsin molecule has evolved by means of gene duplication and has generally
enhanced our colour vision. However when the gene is nonfunctional it results in redgreen colour blindness in men
Chemical Signals
Two major regulatory chemicals: Hormones and Neurotransmitters
--as seen, neurotransmitters regulated by nervous system while hormones
controlled by excretory system
Hormones
produced in ductless (endocrine glands)
moves through blood to a target cell
short-lived response
*Refer to Barron’s page 235 Overview of Hormones
Hypothalamus
Bridge between the endocrine and nervous
systems– ultimately two functions.
http://www.studyblue.com/notes/note/n/limbic-system/deck/1241563
Stress- Nervous function, sends out
electrical signals to adrenal gland to release
adrenaline
Nervous, when releasing gonadotrpoic-releasing hormone(GnRH) to stimulate
anterior pituitary to secret FSH and LH.
Endocrine, when releasing oxytocin and antidiuretic hormones
Ways Hormone Stimulate
1. Lipid or Steroid Hormone
Diffuse directly through the plasma membrane and bind to receptor
in nucleus to trigger cell response
2. Protein or peptide hormone (nonsteroidal)
cannot dissolve in the plasma membrane, so they bind to a receptor on
of cell, triggering secondary messenger c-AMP inside cell to convert
extracellular chemical signal to a specific response.