Animal Form and Function Flashcards
1
Q
What are tissues?
A
Groups of similar cells performing a common function
2
Q
What are the 4 general categories of animal tissues?
A
1) Epithelial (outer skin layers and internal protective coverings)
2) Connective (bone, cartilage, blood)
3) Nervous
4) Muscle
3
Q
What is an organ?
A
A group of different kinds of tissues functioning together to perform a particular activity (i.e. heart)
4
Q
What is an organ system?
A
Two or more organs working together to accomplish a particular task (i.e. digestive system)
5
Q
What is homeostasis?
A
The maintenance of stable, internal conditions within narrow limits.
6
Q
How does negative feedback work? (What are the key players?)
A
A RECEPTOR detects changes in conditions beyond specific limits. The INTEGRATOR (or control center) evaluates the change and actives an EFFECTOR to correct the condition.
7
Q
What are ectotherms?
AKA, EX
A
Animals that obtain body heat from the environment. They are sometimes referred to as POIKILOTHERMS (“changing temperature”). Examples: most invertebrates, amphibians, reptiles, and fish. Called “cold-blooded” because they may feel cold to the touch.
8
Q
What are endotherms?
AKA
A
Animals that produce their own body heat. Referred to as HOMEOTHERMS because they maintain a constant internal temperature, or “warm-blooded” because they are warm compared to ectotherms.
9
Q
What mechanisms are used by animals to regulate body temperature?
A
1) Cooling by evaporation: sweating or panting
2) Warming by metabolism: muscle contractions (i.e. shivering) and other metabolic activities generate heat
3) Adjusting surface area to regulate temperature: changing the volume of blood flowing to arms, hands, feet, and ears through vasodilation/vasoconstriction to maintain or release heat; countercurrent exchange of heat in blood to/from extremities to conserve heat.
10
Q
What are vasodilation and vasoconstriction?
A
Increasing or decreasing the diameter of blood vessels
11
Q
What is the function of the respiratory system?
A
Delivering O2 and removing CO2. Generally, RESPIRATION is the movement of gases into and out of the organism.
12
Q
What mechanisms are used for gas exchange in animals?
A
1) Direct with environment: Some animals have large enough surface areas to allow gas exchange directly with the outside environment. Diffusion can bring gas to adjacent cells in small animals (i.e. Platyhelminthes, flatworms). Larger animals (i.e. Annelida, segmented worms) also use a distribution system inside the skin.
2) Gills
3) Tracheae
4) Lungs
13
Q
What are gills?
A
Evaginated structures that creates a large surface area for gas exchange to occur. They can be external or internal. A circulatory system inside gills removes oxygen and delivers waste CO2. Countercurrent exchange maximizes diffusion between blood and water.
14
Q
What are tracheae?
A
Chitin-lined tubes that permeate insect bodies. Oxygen enters and CO2 exits the tracheae through openings called SPIRACLES. Diffusion occurs across moistened tracheal endings.
15
Q
What are lungs?
A
Invaginated structures within an animal.
16
Q
What are invaginated structures?
A
Cavities within the body of an animal.
17
Q
What are evaginated structures?
A
Outgrowths from the body
18
Q
What are operculum?
A
Gill covers in fish where water exits after passing over the gills.
19
Q
What are book lungs?
A
Stacks of flattened membranes enclosed in an internal chamber. Present in spiders.
20
Q
What are spiracles?
A
Tracheae openings through which oxygen enters and CO2 exits
21
Q
What structures are involved in gas exchange in humans?
A
1) Nose, pharynx, larynx
2) Trachea
3) Bronchi, bronchioles
4) Alveolus (p: alveoli)
5) Lungs (diaphragm and intercostal muscles)
22
Q
What is the pharynx?
A
Nasal cavity
23
Q
What is the larynx?
A
“voice box” that contains the vocal cords
24
Q
What is the trachea?
A
A cartilage-lined tube through which air passes. The EPIGLOTTIS cover the trachea when swallowing to prevent solids and liquids from entering.
25
What is the epiglottis?
A flap that covers the trachea when swallowing to prevent entrance of solids and liquids.
26
What are bronchi (s: bronchus)?
The trachea branches into 2 bronchi, which enter the lungs and then branch repeatedly into narrower tubes called BRONCHIOLES.
27
What are bronchioles?
Narrower tubes resulting from the branching of bronchi.
28
What is the alveolus (p: alveoli)?
A small sac at the end of each bronchiole. It is densely surrounded by blood-carrying capillaries.
29
How does air enter the lungs? Describe bulk flow of air into and out of the lungs (mechanics of respiration).
When the diaphragm and intercostal muscles contract, lung volume increases, air pressure decreases, and air rushes into the lungs through bulk flow. When the muscles relax, the volume decreases, increasing air pressure, and air rushes out. Air passes through the nose, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli membranes.
30
What is the diaphragm?
A muscle under the lungs
31
What are intercostal muscles?
Muscles between the ribs
32
How does air diffuse into blood?
Oxygen diffuses across the moisture covering the alveolus membrane, then the alveolar wall, through the blood capillary wall, into the blood, and into red blood cells. Carbon dioxide diffuses in the opposite direction.
33
How is oxygen circulated in the body? (Describe the bulk flow of oxygen.)
The circulatory system transports oxygen throughout the blood within red blood cells, where they bind to iron-containing proteins called hemoglobin.
34
How do oxygen and carbon dioxide diffuse from blood to cells?
Oxygen diffuses out of the RBC, across blood capillary walls throughout the body, into interstitial fluids (the fluid surrounding cells), and across cell membranes. Carbon dioxide diffuses in the opposite direction.
35
How is carbon dioxide transported in the body? (Describe the bulk flow of carbon dioxide.)
While most CO2 is transported as dissolved bicarbonate ions (HCO3-) in plasma, some CO2 gas mixes directly with plasma or binds with amino groups of hemoglobin. Formation of bicarbonate ions occurs in RBC, where carbonic anhydrase catalyzes the formation of carbonic acid (H2CO3), and then the ions diffuse back into plasma. CO2 + H2O --> H2CO3 --> H+ + HCO3-
36
How is respiration controlled?
Chemoreceptors in the carotid arteries monitor blood pH. CO2 production increases when the body is active, and as a result, blood pH drops. The chemoreceptors send nerve impulses to the diaphragm and intercostal muscles to increase the respiratory rate, increasing gas exchange to return pH to normal.
37
What are the carotid arteries?
Arteries that supply blood to the brain
38
What is the function of the open circulatory system?
- In insects and most mollusks
- Blood is pumped into an internal cavity called a HEMOCOEL (or cavities called SINUSES), which bathe tissues with an oxygen- and nutrient-carrying fluid called HEMOLYMPH.
- Hemolymph returns to the heart, which is the pumping mechanism of the system, through holes called OSTIA
39
What is the function of the closed circulatory system?
- In members of the phylum Annelida (i.e. earthworms), certain mollusks (octopuses and squids), and vertebrates
- The nutrient-, oxygen-, and waste-carrying fluid, blood, is confined to vessels
40
What vessels carry blood away from the heart in the closed circulatory system of vertebrates?
Vessels moving away from the heart are called ARTERIES, which branch into smaller vessels called ARTERIOLES, which branch into the smallest vessels, called CAPILLARIES.
41
What vessels carry blood back to the heart in the closed circulatory system of vertebrates?
Blood returns to the heart through VENULES, which merge to form larger VEINS.
42
What is the general path of blood in the closed circulatory system of vertebrates?
Heart --> arteries --> arterioles --> capillaries -->cells --> capillaries --> venules --> veins --> heart --> arteries --> arterioles --> capillaries --> lungs/gills --> veins --> heart --> repeat
43
How does blood move through the human heart?
Right atrium --> right ventricle --> lungs--> left atrium --> left ventricle --> aorta --> rest of body
44
What occurs in the right atrium?
Deoxygenated blood enters through 2 veins, the upper SUPERIOR VENA CAVA and the lower INFERIOR VENA CAVA before moving to the right ventricle.
45
What occurs in the right ventricle?
Deoxygenated blood moves from the right atrium through the RIGHT ATRIOVENTRICULAR (AV) VALVE, aka tricuspid valve, into the right ventricle, whose walls are thicker and more muscular than those of the atria. The walls contract and pump blood into the PULMONARY ARTERY, through the PULMONARY SEMILUNAR VALVE, towards the lungs. When the ventricles contract, the AV valve closes and prevents blood moving backward into the atrium. When they relax, the semilunar valve prevents back flow from the pulmonary artery back into the ventricles.
46
What does the pulmonary semilunar valve do?
It prevents blood from the pulmonary artery back into the right ventricle when the ventricle relaxes.
47
What does the right atrioventricular (AV) valve do?
| AKA
AKA tricuspid valve
| Prevents blood from moving backward from the right ventricle to right atrium when the ventricle contracts.
48
What is the pulmonary artery?
The artery that carries deoxygenated blood from the heart to the lungs.
49
What occurs in the left atrium?
Oxygenated blood returns to the left atrium through the PULMONARY VEINS.
50
What is the pulmonary vein?
The vein that carries oxygenated blood from the lungs to the heart.
51
What occurs in the left ventricle?
Blood moves from the left atrium through the LEFT ATRIOVENTRICULAR (AV) VALVE, aka mitral or biscupid valve), into the left ventricle, The ventricle pumps blood into the AORTA, through the AORTIC SEMILUNAR VALVE, and throughout the body. The left AV valve prevents blood from flowing back into the atrium, and the semilunar valve prevents blood from flowing back into the ventricle.
52
What does the left atrioventricular (AV) valve do?
| AKA
AKA mitral or bicuspid valve
| Prevents blood from flowing back from the left ventricle into the left atrium when the ventricle contracts.
53
What does the aortic semilunar valve do?
Prevents blood from flowing back from the aorta into the left ventricle.
54
What is the pulmonary circuit?
The blood pathway between the right side of the heart, to the lungs, and back to the left side of the heart.
55
What is the systemic circuit?
The blood circulation pathway throughout the body (between the left and right sides of the heart).
56
What is the cardiac/heart cycle?
The rhythmic contraction and relaxation of heart muscles, regulated by specialized tissues in the heart called AUTORHYTHMIC CELLS.
57
What are autorhythmic cells?
Specialized tissues in the heart that are self-excitable and able to initiate contractions without external stimulation by nerve cells.
58
What are the steps of the cardiac/heart cycle?
1) The SA (SINOATRIAL) NODE, aka pacemaker, spontaneously initiates the cycle by simultaneously contracting both atria and sending delayed impulse that stimulates the AV (ATRIOVENTRICULAR) NODE.
2) The AV node in the lower wall of the right atrium sends an impulse through the bundle of His, resulting in the contraction of the ventricles.
3) Contraction of the ventricles (the SYSTOLE phase) forces blood through the pulmonary arteries and aorta. When the ventricles relax, it is in the DIASTOLE phase. The closing of the valves produces the "lub-dup" sounds of the heart.
59
What is the SA (sinoatrial) node?
| AKA
AKA pacemaker
Located in the upper wall of the right atrium, it spontaneously initiates the cardiac/heart cycle by simultaneously contracting both atria and sending a delayed impulse that stimulates the AV (atrioventricular) node.
60
What is the AV (atrioventricular) node?
Located in the lower wall of the right atrium, it sends an impulse through the bundle of His, nodal tissue that passes down between both ventricles and then branches into ventricles through the PURKINJE FIBERS. This results in contraction of the ventricles.
61
What is the bundle of His?
Nodal tissue that passed down between both ventricles and branches into ventricles through the Purkinje fibers. Impulses sent from the AV node through it results in the contraction of the ventricles.
62
What is the systole phase?
When the ventricles contract, forcing blood through the pulmonary arteries and aorta. AV valves are forced closed.
63
What is the diastole phase?
When the ventricles relax. The semilunar valves are forced closed.
64
What causes blood to move through the arteries?
Hydrostatic pressure created by the heart
65
What causes blood to move through the veins?
Movement of adjacent skeletal muscles squeeze the blood vessels, and valves in the veins prevent back flow to move blood in the direction of the heart. It is NOT because of the contractions of the heart.
66
What is the lymphatic system?
A network of capillaries and veins that return fluids (wastes and excess interstitial fluids) to the circulatory system and lymph nodes act as filters.
67
What is lymph? How does it move through the lymphatic system?
Lymph is the fluid in lymphatic veins. It moves slowly through lymphatic vessels by the contraction of adjacent muscles, while valves prevent back flow. It returns to the blood circulatory system through two ducts located in the shoulder region.
68
What are lymph nodes?
Enlarged bodies throughout the lymphatic system that act as cleaning filters for lymph and immune response centers that defend against infection.
69
What are the contents of blood?
1) erythrocytes (red blood cells)
2) leukocytes (white blood cells)
3) platelets
4) plasma
70
What do red blood cells do? What is another name for them?
AKA erythrocytes
They transport oxygen attached to hemoglobin and catalyze the conversion of carbon dioxide and water to carbonic acid. Mature RBC lack a nucleus, maximizing hemoglobin content and ability to transport oxygen.
71
What do white blood cells do? What is another name for them?
AKA leukocytes
| They consist of 5 major groups of disease-fighting cells that defend the body against infection.
72
What are platelets?
Cell fragments involved in blood clotting. They release factors involved in converting of the major clotting agent FIBRINOGEN into its active form, FIBRIN. Threads of fibrin protein form a network that stops blood flow.
73
What is plasma?
The liquid portion of blood that contains various dissolved substances.
74
What is fibrinogen?
The major blood clotting agent, in its inactive form.
75
What is fibrin?
The active form of fibrinogen, the major blood clotting agent. Threads of this protein form a network that stops blood flow.
76
What is the main function of the excretory system?
Maintain homeostasis in organisms by regulating water balance and removing harmful substances.
77
What is osmoregulation?
The absorption and excretion of water and dissolved substances (solutes) to maintain proper water balance and osmotic pressure between an organism and its surroundings.
78
What does it mean when an organism is hypoosmotic with its environment?
It is less salty than the surrounding water. An example is marine fish, which constantly drink water, rarely urinate, and secrete accumulated salt through gills.
79
What does it mean when an organism is hyperosmotic with its environment?
It is saltier than the surrounding water. An example is fresh water fish, which rarely drink, constantly urinate, and absorb salts through their gills.
80
What are some important excretory mechanisms?
1) Contractile vacuoles
2) Flame cells (protonephridia)
3) Nephridia (or metanephridia)
4) Malpighian tubules
5) Kidney system
81
What are contractile vacuoles?
Vacuoles that accumulate water and merge with the plasma membrane to release the water to the environment. They are found in the cytoplasm of various protists, such as paramecia and amoebas.
82
What are flame cells (protonephridia)?
Cells that are distributed along a branched tube system that permeates flatworms. Body fluids are filtered through the cells, whose internal cilia move the fluids through the tube system. Wastes (salts and water) are excreted from the tube system through pores that exit the body. Found in faros Platyhelminthes, such as planaria.
83
What are nephridia (or metanephridia)?
A tube-type excretory system that occurs in pairs within each segment of most annelids, such as earthworms. Interstitial fluids enter the nephridium through a ciliated opening called a NEPHROSTOME. Fluids are concentrated as they pass through the COLLECTING TUBULE due to selective secretion of materials into the surrounding coelomic fluid. Blood capillaries reabsorb the materials. The concentrated wastes are excreted through the EXCRETORY PORE.
84
What are malpighian tubules?
Tubes attached to the midsection of insect digest tracts (midgut) and collect body fluids from the hemolymph bathing cells. As the fluid passes through the hind gut of the insect (along with digested food), materials to be retained pass back out through the walls of the digestive tract and wastes continue in the tract and are excreted through the anus. Found in many arthropods, such as terrestrial insects.
85
Describe the kidney mechanism of excretion?
In vertebrates, kidneys consist of a million individual filtering tubes called NEPHRONS. Two kidneys produce waste fluids, or URINE, which pass through URETERS to the BLADDER for temporary storage, and is then excreted through the URETHRA.
86
How are nephrons positioned in the human kidney?
The CONVOLUTED TUBULE winds from the outer portion of the kidney, the CORTEX, down through the MEDULLA, back up through the cortex, then back down through the medulla to train at the center of the kidney, the RENAL PELVIS.
87
What is Bowman's capsule?
A bulb-shaped body at the beginning of the nephron tube, filled with the GLOMERULUS, a dense ball of capillaries from the renal artery (the afferent arteriole).
88
What is the glomerulus?
A dense ball of capillaries branched from the renal artery (the afferent arteriole).
89
What is the convoluted tubule?
A tube inside the nephron. It begins with the PROXIMAL CONVOLUTED TUBULE at the Bowman's capsule, continues with the LOOP OF HENLE, and ends when the DISTAL CONVOLUTED TUBULE joins with the COLLECTING DUCT. It is surrounded by a dense network of capillaries from the efferent arteriole that exits the glomerulus. These capillaries merge with the renal vein as they exit the nephron.
90
What is the collecting duct?
A tube that is shared by numerous nephrons, whose convoluted tubes empty into the duct. The duct descends toward the center of the kidney, into the RENAL PELVIS, which drains into the URETER.
91
What are the 3 processes of the human nephron?
1) Filtration
2) Secretion
3) Reabsorption
92
Describe the filtration process in a human nephron.
When blood enters the glomerulus, pressure forces water and solutes (glucose, salts, vitamins, nitrogen wastes, but NOT RBC and proteins) through the capillary walls into Bowman's capsule. The resulting filtrate, flows into the convoluted tubule.
93
Describe the secretion process in a human nephron.
As filtrate passes through the convoluted tubule, additional material from the interstitial fluids joins the filtrate. The material originates from the capillary network surrounding the nephron, and is selectively secreted by passing and active transport into the convoluted tubule.
94
Describe the reabsorption process in a human nephron.
Filtrate becomes more concentrated as it moves down the loop of Henle because water passively flows out of the tube. It becomes more dilute due to passive and active transport of salts out when moving up the loop of Henle. The filtrate is not more concentrated after it moves through the loop of Henle, but the interstitial fluids surround it are. Water passively moves from the filtrate in the collecting duct to the interstitial fluids, so by the time the filtrate drains into the renal pelvis, it is concentrated urine.
95
What hormones influence osmoregulation?
1) Antidiuretic hormone (ADH)
| 2) Aldosterone
96
What is antidiuretic hormone (ADH)?
A hormone that increases the permeability of the collecting duct to water. As a result, water reabsorption by the body increases when it diffuses form the collecting duct, increasing the concentration of salts in urine.
97
What is aldosterone?
A hormone that increases the permeability of the distal convoluted tubule and collecting duct to Na+. As a result, more Na+ diffuses out of the tubule and duct, with water passively following, increasing both the reabsorption of water and Na+.
98
In what forms is toxic ammonia (NH3) excreted from the body?
1) NH3 or NH4+ in aquatic animals
2) urea in mammals
3) uric acid in birds, insects, and many reptiles
99
What is urea?
A converted form of NH3 in mammals. The conversion takes place in the liver. Urea is less toxic and requires less water to excrete in the urine than ammonia.
100
What is uric acid?
A converted form of urea in birds, insects, and most reptiles. It is mostly insoluble and precipitates in water. It allows secretion as a solid, conserving water. In birds, it allows nitrogen waste to be securely isolated in a special sac in the egg called the ALLANTOIS, apart from the embryo.
101
What is intracellular digestion?
Digestion in an individual cell when a lysosome containing digestive enzymes merges with a food vacuole.
102
What is extracellular digestion?
Digestion that occurs when food is digested in a GASTROVASCULAR CAVITY and then absorbed by individual cells.
103
What four types of molecules are commonly encountered in digestion? What are they broken down into?
1) Starch is broken down into glucose
2) Protein is broken down into amino acids
3) Fats/lipids are broken down into glycerol and fatty acids
4) Nucleic acids are broken down into nucleotides
104
What digestive processes occur in the mouth?
Salivary glands secrete SALIVARY AMYLASE, which breaks starch down into maltose (a disaccharide). Chewing reduces the size of food particles to increase the surface area for amylase and other enzyme to operate. Food is shaped into a ball, or BOLUS, and then swallowed.
105
What digestive processes occur in the pharynx?
When food is swallowed and passed into the PHARYNX, or throat, the epiglottis blocks the trachea so that material only enters the ESOPHAGUS.
106
What digestive processes occur in the esophagus?
Food moves through the esophagus, a tube leading to the stomach, by muscular contractions called PERISTALSIS.
107
What digestive processes occur in the stomach?
The stomach secretes a mixture of digestive enzymes and HCl called GASTRIC JUICE. It is also used for:
- Storage (2-4 liters)
- Mixing food w/ water and gastric juice to produce CHYME
- Physically breaking down food
- Chemically breaking down food
- Controlled release of chyme through the PYLORIC SPHINCTER, a regulated valve
108
What is chyme?
A creamy mixture of food, water, and gastric juice
109
How is food physically broken down in the stomach?
- Churning
| - HCl to denture proteins and loosen substances holding food cells together. The HCl also kills most bacteria.
110
How is food chemically broken down in the stomach?
- Proteins are digested by the enzyme PEPSIN, which is secreted by stomach cells in its inactive form, PEPSINOGEN. It is activated by HCl, produced by other stomach cells.
- Failure of mucus to protect the stomach can lead to lesions called PEPTIC ULCERS, usually caused by bacteria, not stress or diet, as long believed. They can usually be treated by antibiotics.
111
What is the duodenum?
The first 25 cm of the small intestine where digestion of starches and proteins continues and all other food types begins (including fats and nucleotides).
112
What digestive proteins are produced by the small intestine?
- Proteolytic enzymes/proteases, including aminopeptidase
- Maltase and lactase (to digest disaccharides)
- Phosphatases (to digest nucleotides)
113
What are proteolytic enzymes/proteases?
Enzymes that digest proteins
114
What are maltase and lactase?
Enzymes that digest disaccharides
115
What are phosphatases?
Enzymes that digest nucleotides
116
What digestive enzymes are produced by the pancreas?
-Trypsin and chymotrypsin (proteases)
-Lipase (to digest fats)
-Pancreatic amylase (to digest starch)
Along with other enzymes, packaged in an alkaline solution that serves to neutralize HCl in chyme.
Enters the duodenum through the pancreatic duct.
117
What digestive chemicals are produced by the liver?
Bile emulsifies fat so that fat-digesting enzymes (i.e. lipase) can act. Bile is alkaline and serves to help neutralize HCl in chyme. It is stored in the gallbladder, adjacent to the liver, and flows through the bile duct, where it merges with the pancreatic duct.
118
What are villi and microvilli?
Fingerlike projections in the small intestinal wall that increase absorptive surface area.
119
What are amino acids, sugars, fatty acids, and glycerol absorbed by?
- Amino acids and sugars are absorbed into blood capillaries.
- Fatty acids and glycerol are absorbed into the lymphatic system.
120
What is the function of the large intestine?
AKA colon
Reabsorbs water to form solid waste, or feces, which is stored at the end of the colon in the rectum and excreted through the anus.
Various harmless bacteria live in the colon, including some that produce vitamin K, which is absorbed through the intestinal wall. f
121
What is the appendix?
A pouch with fingerlike projection connected at the beginning of the large intestine by a short branch. It may have a possible role in the immune response, but is only significant if it becomes inflamed, causing appendicitis. In herbivores, the pouch is much enlarged and called the CECUM, which harbors bacteria that help in the digestion of cellulose.
122
What is the cecum?
A pouch like the appendix in herbivores. It contains bacteria that aid in the digestion of cellulose.
123
What hormones are involved in the digestive process?
1) Gastrin
2) Secretin
3) Cholecytoskinin
124
What is gastrin?
A digestive hormone produced by cells in the stomach lining when food reaches the stomach or the nervous system senses the availability of food through smell or sight. It enters the bloodstream and stimulates other stomach cells to produce gastric juices.
125
What is secretin?
A digestive hormone produced by cells lining the duodenum when food enters. It stimulates the pancreas to produce bicarbonate which neutralizes the acidity of chyme in the small intestine.
126
What is cholecytoskinin?
A digestive hormone produced by the small intestine in response to the presence of fat. It stimulates the gallbladder to release bile and the pancreas to release its enzymes.
127
What is a neuron? What are its parts?
A nerve cell
1) cell body
2) dendrite
3) axon
128
What does the neuron cell body contain?
Nucleus and other cellular organelles
129
What is a dendrite?
Short, abundantly branched, slender extensions of the neuron cell body that receive stimuli.
130
What is an axon?
Long, slender extensions of the neuron cell body that send nerve impulses.
131
What are the 3 groups of neurons?
1) Sensory/afferent neurons
2) Motor/efferent neurons
3) Association/interneuron neurons
132
What are sensory neurons?
| AKA, EX
AKA afferent neurons
| They receive the initial stimulus (i.e. light in eye, touch by hand).
133
What are motor neurons?
| AKA, EX
AKA efferent neurons
They stimulate EFFECTORS (target cells that produce some kind of response). (i.e. stimulate muscles to move to maintain balance or avoid pain, sweat glands to cool body, cells in stomach to secrete gastrin in response to smell of food)
134
What are association neurons?
| AKA
AKA interneuron neurons
Located in the spinal cord or brain, they receive impulses from sensory neurons or send impulses to motor neurons. they are considered INTEGRATORS, evaluation impulses for appropriate responses.
135
Describe polarization across the membrane of a neuron.
An unstimulated neuron is polarized. Na+/K+ pumps in the membrane maintain an excess of Na+ outside and K+ inside the neuron, while large, negative ions such as proteins and nucleic acids, reside inside the cell. It is the large negative ions that contribute to the overall negative charge inside the cell compared to outside.
136
What are the steps in transmitting a nerve impulse?
1) Resting potential (about -70 millivolts)
2) Action potential
3) Repolarization
4) Hyperpolarization
5) Refractory period
137
What is the resting potential of a neuron?
The unstimulated, polarized state (about -70 millivolts).
138
What is the action potential of a neuron? How does it occur?
A complete depolarization of the neuron (about +30 millivolts). In response to a stimulus, gated ion channels in the membrane open and allow Na+ to rush inside the cell, DEPOLARIZING the cell (from -70 to 0 millivolts). If the stimulus is above the THRESHOLD LEVEL, more Na+ gates open, increasing the flow of Na+, causing an ACTION POTENTIAL. This stimulates neighboring Na+ gates further down the neuron to open, and the action potential continues to travel down the neuron.
139
What is repolarization of a neuron? How does it occur?
Restoring the original membrane polarization. In response to the inflow of Na+, K+ channels open and K+ rush out of the cell, causing it to depolarize. Soon after the K+ gates open, the Na+ gates close.
140
What is hyperpolarization of a neuron? How does it occur?
The neuron is about -80 millivolts after the K+ gated channels close. More K+ has moved out of the cell than it is necessary to establish the original polarized potential.
141
What is the refractory period for a neuron?
A period after the action potential has passed during which the neuron will not respond to a new stimulus because Na+ and K+ are on the wrong sides of the membrane. After Na+/K+ pumps in the cell membrane return Na+ and K+ to their resting potential locations, and the neuron is ready for another stimulus.
142
What is a myelin sheath made of? What is its function?
Composed of SCHWANN CELLS, myelin sheaths cover axons on some neurons. They act as insulators and are separated by gaps of unsheathed axons called NODES OF RANVIER. This allows action potentials to jump from node to node in a process called SALTATORY CONDUCTION, speeding the propagation of the impulse.
143
What is saltatory conduction?
A process by which action potentials jump from nodes of Ranvier to other nodes of Ranvier, skipping over areas of axons covered by myelin sheaths. This increases the rate of propagation of impulses.
144
What is a synapse?
| AKA
AKA synaptic cleft
| The gap that separates adjacent neurons.
145
How is an impulse transmitted across a synapse?
An electrical or chemical impulse travels from the presynaptic cell to the postsynaptic cell.
146
What occurs in an electrical synapse?
The action potential travels along the membranes of GAP JUNCTIONS, small tubes of cytoplasm that connect adjacent cells. Less common than chemical synapse.
147
What are the steps of a chemical synapse?
1) Calcium (Ca2+) gates open when the action potential reaches the end of an axon and Ca2+ enters the cell.
2) Influx of Ca2+ causes SYNAPTIC VESICLES to merge with the PRESYNAPTIC CLEFT to release NEUROTRANSMITTERS into the synaptic cleft.
3) Neurotransmitters bind to postsynaptic receptors (proteins specific for different neurotransmitters).
4) The postsynaptic membrane is excited or inhibited, depending on the neurotransmitter and receptor.
5) The neurotransmitter is degraded by enzymes in the synaptic cleft and recycled by the presynaptic cell.
148
What are the two possible outcomes of a chemical synapse?
1) If Na+ gates open, the membrane depolarizes and results in an EXCITATORY POSTSYNAPTIC POTENTIAL (EPSP). An action potential is generated if the threshold potential is exceeded.
2) If K+ gates open, the membrane becomes hyper polarized and results in an INHIBITORY POSTSYNAPTIC POTENTIAL (IPSP), making it more difficult to generate an action potential.
149
What are some common neurotransmitters?
1) Acetylcholine
2) Epinephrine, norepinephrine, dopamine, and serotonin
3) Gamma aminobutyric acid (GABA)
150
What is acetylcholine?
A neurotransmitter secreted at NEUROMUSCULAR JUNCTIONS, the gaps between motor neurons and muscle cells, where it stimulates muscles to contract. It typically produces an inhibitory post-synaptic potential at other kinds of junctions. It is degraded by CHOLINESTERASE.
151
What is cholinesterase?
An enzyme that degrades acetylcholine in the synaptic cleft.
152
What amino acid derived neurotransmitters are mostly secreted between neurons of the central nervous system?
Epinephrine, norepinephrine, dopamine, and serotonin.
153
What is gamma aminobutyric acid (GABA)?
A neurotransmitter that is usually inhibitory among neurons in the brain.
154
What are the two parts of the nervous systems of humans and other vertebrates?
1) Central nervous system (CNS)
| 2) Peripheral nervous system (PNS)
155
What are the parts of the central nervous system (CNS)?
brain and spinal cord
156
What are the part of the peripheral nervous system (PNS)? What are their functions?
1) Sensory neurons transmit impulses to the CNS
2) Motor neurons transmit impulses from the CNS to effectors. It can be divided into two groups (somatic nervous system and autonomic nervous system).
157
What are the two groups of the motor neuron system? What are their functions?
1) The somatic nervous system directs the contraction of skeletal muscles.
2) The autonomic nervous system directs the activities of organs and various involuntary muscles (i.e. cardiac and smooth muscles).
158
What is the function of the somatic nervous system?
The motor neuron system that directs the contraction of skeletal muscles.
159
What is the function of the autonomic nervous system?
The motor neuron system that directs the activities of organs and various involuntary muscles (i.e. cardiac and smooth muscles).
160
What are the two divisions of the autonomic nervous system? What do they do?
1) The sympathetic nervous system stimulates activities that prepare the body for action (fight-or-flight responses).
2) The parasympathetic nervous system activates tranquil functions (i.e. secretion of saliva or digestive enzymes).
161
What is the sympathetic nervous system?
| EX
A division of the autonomic nervous system that stimulates activities to prepare the body for action (fight-or-flight response). EX: increase heart rate, increase release of sugar from liver into blood
162
What is the parasympathetic nervous system?
| EX
A division of the autonomic nervous system that activates tranquil functions. EX: secretion of saliva or digestive enzymes into the stomach
163
What is a reflex arc?
A rapid, involuntary response to a stimulus that always involves a sensory and motor neuron, and sometimes an interneuron. Although information may be transmitted to the brain, it does not actually integrate the sensory and motor activities.
164
What is the nonspecific first line of defense in the immune system? Why is it nonspecific?
Skin and mucous membranes defend against invaders entering through the skin or openings in the body. It is not specialized for a particular invader, but rather defense against all kinds of pathogens.
165
What are the features of the nonspecific first line of dense in the immune system?
1) Skin: physical and hostile barrier covered with oily and acidic (pH 3-5) secretions from sweat glands
2) Antimicrobial proteins (i.e. lysozyme, which breaks down cell walls of bacteria) are contained in saliva, tears, and other secretions on mucous membranes
3) Cilia: line lungs and sweep invaders out of the lungs
4) Gastric juice of stomach kills most microbes
5) Symbiotic bacteria in digestive tract and vagina outcompete many other organisms that could cause damage
166
What are the features of the second line of defense in the immune system?
1) Phagocytes
2) Complement
3) Interferons
4) Inflammatory response
167
What are phagocytes?
Leukocytes that engulf pathogens by phagocytosis. They include NEUTROPHILES and MONOCYTES. Monocytes enlarge into large phagocytic cells called MACROPHAGES. Other leukocytes called NATURAL KILLER CELLS (NK CELLS) attack abnormal body cells (i.e. tumors) or pathogen-infected body cells.
168
What is a complement?
A group of about 20 proteins that "complement" defense reactions by helping to attract phagocytes to foreigns cells and helping to destroy foreign cells by promoting cell lysis (breaking open the cell).
169
What are interferons?
Substances secreted by cells invaded by viruses that stimulate neighboring cells to produce proteins that help them defend against the viruses.
170
What are NK cells?
Natural killer cells that attack abnormal body cells (such as tumors) or pathogen-infected body cells.
171
What is the inflammatory response?
A series of nonspecific events that occur in response to pathogens.
172
What occurs in the inflammatory response when skin is damaged and bacteria or other organisms enter the body?
1) HISTAMINE is secreted by BASOPHILS, white blood cells found in connective tissue
2) Vasodilation is stimulated by histamine, increasing blood supply to the area and allowing for easier movement of WBC and other body fluids through blood vessel walls. This can cause redness, an increase in temperature, and swelling. The increase in temperature may stimulate WBC and make the environment inhospitable to pathogens.
3) Phagocytes are attracted to the injury by chemical gradients of complement and engulf pathogens and damaged cells
4) Complement helps phagocytes engulf foreign cells, stimulate basophils to release histamine, and help lyse foreign cells.
173
What is the third line of defense in the immune system?
The immune response, which targets specific ANTIGENS.
174
What are antigens?
| EX
Any molecule, usually a protein or polysaccharide, that can be identified as foreign. It may be a toxin, part of the virus protein coat, or a molecule unique to the plasma membrane of bacteria, protozoa, pollen, or other foreign cells.
175
What is the MHC? What does it do?
The major histocompatibility complex is the mechanism by which the immune system is able to differentiate between self and non self cells. It is a collection of glycoproteins that exists on membranes of all body cells. The proteins of a single individual are unique, and it is very unlikely two people will possess the same set of MHC molecules.
176
What are the primary agents of the immune response?
Lymphocytes, white blood cells that originate in the bone marrow (like all blood cells) but concentrate in lymphatic tissues such as the lymph nodes, thymus gland, and spleen. Various kinds are grouped into T cells and B cells.
