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235 Cards in this Set
- Front
- Back
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Facilitated diffusion does/doesn't require energy. It transports molecules from ____ to ____ concentrations.
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Doesn't. High to low
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Active transport does/doesn't require energy. It transports molecules from ____ to ____ concentrations.
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Does. Low to high
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What are the two types of carrier-mediated transport?
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1) Facilitated diffusion
2) Active transport |
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What are the levels of organization?
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1) Chemical/Molecular
2) Cell 3) Tissue 4) Organ 5) Organ system 6) Organism |
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What are the functions of the cell?
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obtain nutrients and oxygen
metabolism synthesis exchange of materials intracellular transport reproduction |
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What is the definition of tissue?
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Aggregate of cells and extracellular material
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What are the 4 primary types of tissue?
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Muscle, Nervous, Epithelial, Connective
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Give examples of muscle tissue
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skeletal
cardiac smooth |
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Give examples of nervous tissue
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central
peripheral |
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Give examples of epithelial tissue
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epithelial sheets (form boundaries)
glands (secretion of synthesized materials) Exocrine (external secretion) Endocrine (internal secretion) |
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Give examples of connective tissue
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tendons
bones blood |
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What is the definition of an organ?
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Two or more primary tissues organized to perform a function
e.g. Stomach: composed of all 4 tissue types |
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What is the definition of an organ system?
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Collection of organs that perform related functions essential to survival
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What are the different organ systems?
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~Circulatory System
heart, blood vessels, blood ~Digestive System mouth, pharynx, esophagus, stomach, small intestine, large intestine, salivary glands,pancreas, liver, gall bladder ~Respiratory System nose, pharynx, larynx, trachea, bronchi, lungs ~Urinary System kidneys, ureters, urinary bladder, urethra ~Skeletal System bones, cartilage, joints ~Muscular System skeletal muscles ~Integumentary System skin, hair, nails ~Immune System white blood cells, thymus, bone marrow, tonsils, adenoids, lymph nodes, spleen, appendix, gut and skin-associated lymph tissue ~Nervous System brain, spinal cord, peripheral nerves, sense organs ~Endocrine System hormone secreting tissues: hypothalamus, pituitary, thyroid, adrenals, endocrine pancreas,parathyroids, gonads, kidneys, intestine, heart, thymus, pineal, skin ~Reproductive System male: testes, penis, prostate gland, seminal vesicles, bulbourethreal glands female: ovaries, oviducts, uterus, vagina, breasts |
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** What is homeostasis?
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Dynamic maintenance of a stable internal (extracellular) environment within the organism
- essential to survival of each cell - requires continual exchange of materials between the intracellular and extracellular spaces - each organ system contributes by counteracting changes of internal environment |
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With homeostasis, what factors must be maintained?
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concentration of nutrients, concentration of CO2 and O2, concentration of waste products,
pH, concentration of water and electrolytes, temperature, volume and pressure, defense against foreign invaders |
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How is homeostasis maintained?
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By control systems
(know them) ** |
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** What are the two control systems dealing with homeostasis?
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Intrinsic
Extrinsic |
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What is an intrinsic control system?
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Local control systems built into an organ
e.g. increased CO2 production leads to relaxation of smooth muscle and dilation of blood vessels |
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What is extrinsic control?
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External control system outside of an organ permitting coordinated regulation of several organs
I - Nervous system e.g. low blood pressure detected by nervous system which causes increase in heart rate and constriction of blood vessels II - Endocrine system |
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What are the physiological principles?
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Negative Feedback, Positive Feedback and Feedforward Control
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** What is negative feedback?
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Change in a controlled variable triggers a response that opposes the change
sensor - mechanism to detect the controlled variable set point - the desired value of the variable integrator - compares the sensor’s input with the set point effector - adjusts the value of the controlled variable |
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What is positive feedback?
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Reinforces the change in a controlled variable, occurs relatively rarely
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What is feedforward control?
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Response occurring in anticipation of a change in a control variable.
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What is the plasma membrane and what are it's functions?
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Thin membrane enclosing each cell
-composed of phospholipid bilayer embedded with proteins and carbohydrates -separates intracellular and extracellular spaces -serves as a barrier to diffusion |
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What are membrane proteins and what are their functions?
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Proteins within the plasma membrane
-can selectively transport molecules and ions -can act as receptors to signal responses by the cell -can form adhesions and junctions with other cells |
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What is the nucleus?
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Membrane bound organelle containing the genetic material
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What are the genetic materials that the nucleus contains?
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1) Deoxyribonucleic acid (DNA)
-genetic material; directs protein synthesis; serves as genetic blueprint during cell replication 2) Ribonucleic acid (RNA) -carries out protein synthesis |
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What are the different types of RNA?
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1) messenger RNA
genetic code is copied to mRNA via transcription and the message exits the nucleus 2) ribosomal RNA participates in reading the mRNA and translating it into the appropriate protein sequence (translation) 3) transfer RNA transfers the appropriate amino acid in the cytoplasm to their designated site in the protein being constructed |
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What is the cytoplasm?
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Portion of cell’s interior not occupied by the nucleus. Floating within the cytoplasm are organelles, membrane-enclosed structures that carry out specific functions
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What are the 6 main types of organelles that are similar in all cells?
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1) Endoplasmic reticulum
2) Golgi complex 3) Lysosomes 4) Peroxisomes 5) Mitochondria 6) Vaults |
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What is the endoplasmic reticulum?
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continuous fluid filled network of membranous tubules
* rough ER ER membrane covered with ribosomes that synthesize and release proteins into the ER lumen. The protein products can be secreted or transported to sites within the cell. * smooth ER ER membrane lacking ribosomes that serves to package and transport molecules synthesized in the rough ER. Portions of smooth ER bud off to form transport vesicles that move to the Golgi complex for further processing |
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What is a ribosome?
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ribosome
constructed in the nucleus and programmed to carry out the synthesis of a single type of protein |
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What is the Golgi complex?
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sets of flattened, membrane-enclosed sacs stacked in layers and specialized for processing new proteins
into finished products, and directing the products to their destinations including secretion. |
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What happens in the Golgi complex?
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exocytosis---> membrane-enclosed vesicles containing finished products fuse with the plasma membrane, thereby releasing their diffusible contents into the extracellular fluid.
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What are the lysosomes?
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membrane-enclosed sacs derived from the Golgi, contain hydrolytic enzymes to digest and remove unwanted material. Lysosomes fuse with endocytotic vesicles to breakdown internalized material.
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What happens in lysosomes?
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endocytosis---> the process by which extracellular material is brought into the cell
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What are the different types of endocytosis?
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pinocytosis --->invagination of the plasma membrane to form a pouch and internalize extracellular fluid
receptor-mediated endocytosis phagocytosis--->invagination of the plasma membrane to form a large vesicle and internalize large particles such as bacteria or tissue debris |
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What are peroxisomes?
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membrane-enclosed sacs containing oxidative enzymes which act to remove hydrogen from toxic molecules. This leads to the formation of hydrogen peroxide (H2O2) which is degraded by catalase contained within the peroxisome
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What is a catalase?
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An antioxidant enzyme that decomposes H2O2 into H2O and O2.
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What is a mitochondria?
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oval double membrane-enclosed organelles containing the enzymes responsible for aerobic metabolism
and the production of cellular energy in the form of adenosine triphosphate. |
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What is adenosine triphosphate (ATP)?
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molecule composed of adenosine bound to three high energy phosphate groups that serves as the
energy sources for all cellular functions. Energy is released when ATP is converted to ADP and phosphate. ATP is used for chemical synthesis, membrane transport, and mechanical work. |
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What is glycolysis?
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sequence of enzymatic reactions carried out in the cytosol in which a glucose molecule is
converted into 2 molecules of pyruvic acid and 2 molecules of ATP are synthesized. This reaction sequence is responsible for anerobic metabolism. The pyruvic acid molecules are transported into the mitochondrial matrix where each is enzymatically converted to a molecule of Acetyl-CoA and one molecule of CO2, and one molecule of NADH is synthesized |
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What is the citric acid cycle?
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sequence of enzymatic reactions carried out in the mitochondrial matrix in which the energy stored
in one molecule of Acetyl-CoA leads to the formation of one molecule of ATP, two molecules of CO2, three molecules of NADH, and one molecule of FADH2. |
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What is NADH?
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(nicotinamide adenine dinucleotide-H) a derivative of B-vitamin niacin which acts as an energy source by donating electrons
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What is FADH2?
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(flavine adenine dinucleotide-H2) a derivative of B-vitamin
riboflavin which acts as an energy source by donating electrons |
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What is electric transport chain?
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sequence of enzymatic reactions requiring O2 that are carried out in the inner mitochondrial
membrane in which the donation of high energy electrons from NADH and FADH2 lead to the production of ATP and H2O. Oxygen serves as the final electron acceptor and combines with H+ ions to form H2O. For each NADH molecule, 3 ATP molecules are formed and for each FADH2 molecule, 4 ATP molecules are formed |
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What are the vaults in a cell?
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Octagonally shaped proteinaceous organelles which may function to transport molecules, such as mRNA, to sites within the cytoplasm
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What is the cytosol?
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Semiliquid portion of the cytoplasm in which at least three major functions take place:
Enzymatic regulation of intermediate metabolism Ribosomal protein synthesis Storage of fat and glycogen |
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What is the cytoskeleton?
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Complex intracellular protein network that provides structural support and the capability for transport
of material and cellular movement. Composed of 3 major components. |
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What are the three main components that make up the cytoskeleton?
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1) microtubules
2) microfilaments 3) intermediate filaments |
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What are microtubules?
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long, hollow, unbranched proteinaceous tubes composed primarily of tubulin and responsible for
maintaining cell shape, and for controlling cellular movements such as vesicular (axonal) transport, movement of cilia and flagella, and distribution of chromosomes during cell division |
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What is tubulin?
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small globular protein
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What is axonal transport?
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bidirectional movement of large molecules and vesicles along the axon of neurons.
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What is cilia?
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motile, hair-like protrusions allowing cells to move materials across their surface. They line the respiratory airways and the oviducts.
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What is a flagella?
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single, long whip-like appendage that enables cells to move thru their environment. Form the
tails of spermatozoa. |
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What are microfilaments?
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filaments composed of two strings of actin molecules that function in cellular contraction and mechanical support of cellular extensions such as microvilli.
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What are intermediate filaments?
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irregular thread-like protein molecules that provide structural support for cellular components
subject to mechanical stress, such as neuronal extensions, muscle cells, and skin cells |
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What are types of intercellular communication?
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gap junctions, direct signalling, extracellular chemical messengers
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What are some extracellular chemical messengers?
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paracrine
hormone neurotransmitter neurohormone |
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How are extracellular chemicals secreted by one cell detected by another?
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1. G protein coupled receptors, coupled to 2nd messengers pathways e.g. cAMP, IP3 pathways
These pathways ultimately bring about a cellular response by altering the structure and function of proteins. 2. Activation of ion channels Ion channels are membrane proteins that permit small soluble ions such as Na, K, Ca and Cl to pass across the plasma membrane. There are two major types: leak channels, which are always open, and gated channels, which open and close in response to various stimuli. Different types of gated channels are gated by changes in membrane voltage, mechanical deformation, or binding of chemical messengers |
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What is Ionotropic signaling?
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Activation of ion channels by direct binding of extracellular chemical
messenger |
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What is Metabotropic signaling?
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Activation of ion channel via 2nd messenger pathway
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What is membrane transport?
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The movement of substances across the plasma membrane for the purpose of maintaining homeostasis
or carrying out specific functions. The plasma membrane is selectively permeable to certain substances. Therefore some substances can move passively across the plasma membrane while others must be transported. |
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What is selective permeability?
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The chemical structure of the plasma membrane (i.e. bilayer of phospholipids) makes it selectively
permeable to lipid soluble substances or to small molecules and ions. Polar molecules or macromolecules cannot permeate the membrane. |
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What are the three types of membrane transport?
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Selective permeability
Active transport Passive transport |
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What is passive transport?
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Movement of substances across the plasma membrane without expenditure of cellular energy, via
direct permeation. This type of transport can occur by movement along an electrical or chemical gradient or by carrier mediated mechanisms. |
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What is active transport?
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Movement of substances across the plasma membrane that requires the expenditure of cellular
energy. This process may occur for substances that must be transported against their electrochemical gradient, or for substances for which the plasma membrane is impermeable (e.g. sugars, amino acids, proteins). There are two general types of active transport, membrane pumps and vesicular transport (next page). |
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Describe diffusion down a concentration gradient
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random movement of molecules from regions of higher to lower concentration
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Describe movement along an electrical gradient
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An electrical gradient (i.e. voltage difference) is caused by the spatial separation of electrical charge7
that is created when concentration differences among ionic molecules are established. Molecules that are electrically charged (i.e. ions) will move in a direction along an electrical gradient that is determined by their polarity (i.e. positive or negative charge). |
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What is an electrochemical gradient?
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The combined force of concentration and electrical gradients that act on molecular and ionic
substances. |
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Rate of diffusion depends on several factors:
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magnitude of the concentration gradient
permeability of the membrane surface area of the membrane molecular weight of the substance distance over which diffusion takes place |
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What is osmosis?
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A special case of passive transport occurring when water diffuses down its concentration gradient to regions
of higher solute concentration. When this process occurs across the selectively permeable plasma membrane the diffusion of water can exert osmotic pressure |
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What is osmotic pressure?
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The magnitude of opposing hydrostatic pressure that is necessary to stop osmosis. This pressure is
proportional to the difference in solute concentrations that exist across the plasma membrane. Because of this effect, solute concentrations in the intracellular and extracellular spaces are kept in careful balance to avoid substantial changes in cellular pressure or volume. |
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What is carrier mediated transport?
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This process occurs when a substance is bound to a transmembrane protein that undergoes a conformational
change and the substance is released on the other side of the membrane. It can be passive or active depending on the type. |
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What are the different types of carrier mediated transport?
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Facilitated diffusion
Membrane pump |
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What is facilitated diffusion?
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The binding of the substance can directly cause the protein to change its conformation and thereby
facilitate its diffusion across the membrane. Because the energy of binding is used to induce the conformational change, this is a passive process. Alternatively, the conformational change can be induced by a separate energy-dependent process, such as phosphorylation. This is an active process. The latter mechanisms are often referred to as membrane pumps. |
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What are the common types of membrane pumps?
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hydrogen-ion pump and the Na+/K+ ATPase
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What does the hydrogen ion pump do?
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Active transport protein moves H+ against its concentration gradient
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What is the Na+/K+ ATPase?
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Active transport protein that transports Na+ out of the cell and K+ into the cell . Three Na+ ions
are transported out for every two K+ ions in. This pump is present in every cell and has 3 main functions: |
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What is the function of the Na+/K+ ATPase?
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maintenance of Na+ and K+ concentration gradients
maintenance of osmotic balance establishment of energy gradients are used for co-transport of other substances |
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What is vesicular transport?
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The movement of large polar molecules or macromolecules across the plasma
membrane by means of endocytosis and exocytosis. |
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What is resting membrane potential?
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This is the voltage difference that exists across the plasma membrane, expressed in millivolts, when the cell
is at rest (i.e. no perturbing influences) |
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Charge separation across a membrane creates ________
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membrane potential
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How does the cell create charge separation?
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1. Establishes and maintains concentration gradients for key ions (Na+, K+, A-)
2. Ions diffuse through the membrane down their concentration gradients 3. Diffusion through the membrane results in charge separation, creating a membrane potential (electrical gradient) 4. Net diffusion continues until the force exerted by the electrical gradient exactly balances the force exerted by the concentration gradient |
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What do leak channels do?
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Permit ions to flow down concentration gradients
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Describe the permeability of each of these:
A- Na+ K+ |
A- Impermeable, nearly infinite resistance
Na+ Low permeability, relatively high resistance K+ High permeability, low resistance |
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What are the parts of a neuron?
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Soma
Axon Dendrite |
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What is a soma?
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cell body of a neuron
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What is a dendrite?
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membranous processes extending from the soma that receive synaptic inputs from other
neurons |
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What is an axon?
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a single specialized membranous process extending from the soma that conducts action
potentials |
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What are the parts of an axon?
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axon hillock and axon terminal
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What is an axon hillock?
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- the initial portion of the axon extending from the soma. The site at which
action potentials are most commonly generated. |
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What is an axon terminal?
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the distal end of axonal fibers where chemical synaptic transmitter is
released. |
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What is a graded potential?
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Local changes in membrane potential that decay over short distances. Can occur as depolarizations or
hyperpolarizations and most often result from chemical synaptic transmission. |
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What is depolarization?
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decrease in membrane polarization to more positive values than rest. Most often
produced by excitatory synaptic transmission. |
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What is hyperpolarization?
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increase in membrane polarization to more negative values than rest. Most
often produced by inhibitory synaptic transmission. |
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What is an action potential?
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Brief all-or-nothing reversal in membrane potential (spike), lasting on the order of 1 millisecond, that is
brought about by rapid changes in membrane permeability to Na+ and K+ ions. Initiated in axonal or somatic membranes when the membrane potential is depolarized beyond a threshold potential and can propagate along axonal (and dendritic) membranes at a velocity that is determined by several factors. Because of their ability to propagate, action potentials are the primary mechanism used by the nervous system to transfer information over long distances (i.e. up to 1000 mm). |
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What are voltage gated channels?
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Action potentials occur when Na+ and K+ channels in the plasma membrane open in response to
depolarization. Because of their sensitivity to membrane depolarization these channels are referred to as voltage-gated channels. |
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What initiates the action potential?
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Once the threshold potential is crossed, depolarization occurs via a positive feedback cycle
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Dealing with voltage-gated Na+ channels, what is the threshold?
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his is the membrane potential which, when reached, leads inevitably to the occurrence
of a spike. |
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Dealing with voltage-gated Na+ channels, what is the inactivation?
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Occurs more slowly than channel opening (activation) and contributes to the
termination of a spike |
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Dealing with voltage-gated Na+ channels, what is the absolute refractory period?
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A brief period during a spike in which a second
spike cannot be generated due to inactivation. |
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Dealing with voltage-gated K+ channels, what is after hyperpolarization (AHP)?
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A brief period at the end of a spike in which the
membrane potential is more negative than rest. |
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Dealing with voltage-gated K+ channels, what is relative refractory period?
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A brief period following a spike during which a
higher intensity stimulus is needed to generate a second spike. |
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What is propagation?
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Action potentials propagate when locally generated depolarizing current spreads to adjacent regions of
membrane causing it to depolarize. Conduction velocity is proportional to axonal diameter and is increased by myelin. |
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What is continuous conduction?
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Propagation of action potential in unmyelinated fibers. Is relatively slow and inefficient, especially for
small diameter fibers. |
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What is saltatory conduction?
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Propagation of action potential in myelinated fibers by jumping from node to node
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What is myelin?
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- a multilayered sheath of plasma membrane, derived from specialized glial
cells, that wraps around axonal fibers and acts as an insulator to the flow of current. The sheaths occur at regular intervals (~1mm), and are interrupted by gaps in the insulation called Nodes of Ranvier. |
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What are nodes of Ranvier?
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The nodes contain high densities of voltage-gated Na+ and K+ channels and can
generate action potentials. In myelinated axons, action potentials propagate by jumping from node to node through a process called saltatory conduction (Figure 4-16 in 5 th edition only). This process greatly increases the speed of propagation. |
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What are Schwann Cells?
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myelin-forming glial cells in the peripheral nervous system.
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What are Oligodendrocytes?
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myelin-forming glial cells in the central nervous system.
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What are Demyelinating Diseases?
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certain diseases, such as multiple sclerosis, result from the
degeneration myelin. |
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What are synapses?
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Junction between two neurons, or between a neuron and a muscle or gland that enables one cell to
electrically and/or biochemically influence another cell. |
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What is a Synaptic transmission?
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is the primary means of rapid inter-neuronal communication in the brain
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What does the Presynaptic cell do?
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initiates the signal
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What does the Postsynaptic (target) cell do?
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receives the signal
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What does the Postsynaptic target do?
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can be another neuron, a muscle or a gland
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What is an electrical synapse?
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A direct electrical connection between two cells, formed by a gap junction, that allows current to pass
from one cell to another. Composed of multiple proteins called connexons. This type of synaptic connection has no delay and is less common than chemical synapses. |
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What is a chemical synapse?
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Anatomical junction between two neurons, or between a neuron and a muscle or gland where a chemical
neurotransmitter is released by the presynaptic neuron which diffuses across the synaptic cleft and binds to receptors on the postsynaptic neuron to exert a physiological response. The presynaptic release of neurotransmitter, the postsynaptic response, and the removal of transmitter from the synaptic cleft are each governed by complex mechanisms. |
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Describe Presynaptic release
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Neurotransmitter is concentrated into synaptic vesicles in the presynaptic terminal, and is released
through exocytosis when the vesicles fuse with the plasma membrane. Vesicle fusion depends on the presence Ca++ ions in the intracellular medium. Because the intracellular concentration of Ca++ is kept very low (on the order of 100nM), Ca++ must enter the synaptic terminal from the extracellular space. This occurs when an action potential propagates into the synaptic terminal and strongly depolarizes the membrane, causing voltage-gated Ca++ channels to open and allowing Ca++ to flow down its electrochemical gradient. The entry of Ca++ promotes the fusion of the vesicles with the plasma membrane and the neurotransmitter is released into the synaptic cleft. The opening of Ca++ channels in response to depolarization provides the mechanism that tightly links the release of transmitter to the occurrence of an action potential. At any given synapse there is usually, but not always, one type of neurotransmitter released. |
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Describe Postsynaptic response
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This response most commonly consists of a rapid and graded change in membrane potential in the
postsynaptic neuron referred to as a post-synaptic-potential (PSP). PSPs occur when a neurotransmitter binds to a membrane protein called the postsynaptic receptor causing it to change its conformation and increase its permeability to one or more ions. For each type of neurotransmitter there is a distinct class of postsynaptic receptors. PSPs can exhibit a wide range of properties, but most commonly fall into two major categories: |
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What is Excitatory-Post-Synaptic-Potentials (EPSP)?
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A depolarizing potential that tends to bring the cell towards threshold for generation of an action
potential. These PSPs usually result from an increase in membrane permeability to a combination Na+ and K+ ions. The driving force pulling Na+ into the cell is greater than that pulling K+ out of the cell and the net result is depolarization. The most common excitatory neurotransmitters are glutamate (Glu) and acetylcholine (ACh). |
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What is Inhibitory-Post-Synaptic-Potentials (IPSP)?
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A hyperpolarizing potential that tends to bring the cell away from threshold for generation of an action
potential. These PSPs usually result from an increase in membrane permeability to either K+ or Clions. When the permeability to K+ is increased, K+ will flow out of the cell. When the permeability to Cl- is increased, Cl- will flow into the cell. In both cases, this leads to a13 hyperpolarization resulting from a net decrease in the amount of positive charge inside the cell. The most common inhibitory neurotransmitters are gamma-amino-butyric acid (GABA) and Glycine (Gly). |
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What are 2nd messenger systems?
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Some neurotransmitters produce postsynaptic actions indirectly through the activation of intracellular
second messengers. These are often referred to as neuromodulators. In these systems, the binding of neurotransmitter to the postsynaptic receptor triggers the enzymatic synthesis of molecules that can have widespread secondary actions. The type of 2nd messenger synthesized and its actions depend on the type of transmitter released and the class of postsynaptic receptor that is activated. A common 2nd messenger in neurons is cylic-adenosine-monophsphate (cAMP). Many transmitter types can lead to changes in the intracellular production of cAMP. Dopamine and serotonin are examples of neuromodulators. |
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Describe transmitter removal
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Several mechanisms are present in chemical synapses to remove transmitter that has been released into the
synaptic cleft. The transmitter molecules can be degraded by enzymes present in the synaptic cleft, transported back into the presynaptic neuron by active transport, or can di use out of the cleft. Each of these mechanisms reduces the duration of action of the transmitter and insures that its action will be brief |
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What is convergence?
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The synaptic input of many neurons on to one neuron
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What is divergence?
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The synaptic output of one neuron onto many neuron
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What is temporal summation?
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The additive effect of PSPs occurring close together in time
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What is spatial summation?
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The additive effect of PSPs occurring together on nearby parts of
the same cell |
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What is presynaptic inhibition?
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Synaptic inhibition of a synaptic terminal causing a decrease in transmitter
release |
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The ultimate outcome/goal of summation is to produce an...
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action potential or train of action potentials in
the postsynaptic cell, to carry on signaling to the next level of the neuronal network |
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The duration, rate and
timing of action potentials in this output train encode information about... |
the spatiotemporal pattern of
converging inputs. |
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What is the Central Nervous System (CNS)?
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The central nervous system is composed of the brain and the spinal cord. The brain is the portion of the CNS enclosed within the skull, while the spinal cord is that portion of the CNS enclosed within the vertebral column.
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The brain can be grossly subdivided into the:
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forebrain, the brainstem and the cerebellum
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What is the cerebrum?
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is the portion of the CNS largely responsible for the higher cognitive, sensory and motor functions of the brain.
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What is the cerebral cortex?
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The outer, highly folded surface of the cerebrum. This is a layered structure covering nearly the entire brain. Much of higher brain function takes place here.
*Functional localization *Sensory/motor homunculus |
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What are the parts of the cerebrum?
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Cerebral Cortex
Basal Ganglia |
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What are the parts of the forebrain?
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Cerebrum, Thalamus, Limbic system
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What is the basal ganglia?
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A set of large nuclei lying in the center of the brain. These structures are highly interconnected with the cerebral cortex and the thalamus
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What is the thalamus?
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A large nucleus, composed of many smaller subnuclei, lying in the center of the brain just posterior to the Basal Ganglia. This structure functions cooperatively with and is highly connected to the cerebral cortex
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What is the limbic system?
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A collection of nuclei, interconnected to the thalamus and cerebral cortex, that play a key role in learning, memory and emotions
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What is the brainstem?
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This is the evolutionarily older (so-called reptilian) portion of the CNS. It is essential for the maintenance of life and carries out many autonomic functions
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What is the midbrain?
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The upper portion of the brainstem. Involved in numerous functions including regulation of the sleep-waking cycle and the maintenance of arousal
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What are the parts of the brainstem?
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Midbrain
Pons Medulla Oblongata |
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What is the pons?
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The middle portion of the brainstem. Involved in numerous functions and provides the anatomical link between the cerebrum and the cerebellum
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What is the medulla oblongata?
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The lower portion of the brainstem continuous with the spinal cord. Involved in numerous functions and essential in the control of respiration and cardiac function
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What are the parts of the cerebellum?
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Cerebral cortex, deep nuclei
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What is the cerebellum?
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Large neural lobe located on the lower posterior region of the brain. The cerebellum is also involved in numerous functions, and is particularly important in the control of motor coordination. Heavily interconnected with the cerebrum, particularly the cerebral cortex.
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What is deep nuclei?
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Nuclear structures, analogous to the thalamus in the cerebrum, that lay below the cortex in the depth of the cerebellum. Provide a relay for the output of the cerebellar cortex.
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What is the spinal cord?
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Column of neural tissue extending from the medulla to the lower end of the spinal column. Contains the input and output pathways of the CNS and the neuronal circuitry responsible for spinal reflexes.
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What are the subdivisions of the spinal cord?
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Sensory and motor
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What is the sensory subdivision of the spinal cord?
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Subdivision of spinal cord that processes and relays somatic sensory information to the cerebrum.
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What is the motor subdivision of the spinal cord?
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Subdivision of spinal cord that processes and relays somatic motor information from the cerebrum to the somatic musculature
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What is the peripheral nervous system?
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The PNS is the part of the nervous system not located within the skull or spinal column.
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What is the Somatic Division of the PNS?
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The portion of the PNS containing all of the somatic sensory and motor nerves and ganglia
Sensory somatic sensory nerves and ganglia. Motor somatic motor nerves and ganglia. |
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What are the divisions of the PNS?
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Somatic division
Autonomic Division |
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What is the autonomic division of the PNS?
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The portion of the PNS responsible for regulating the involuntary actions of the internal organs.
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What are the subdivisions of the autonomic division of the PNS?
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Sympathetic, Parasympathetic, and Enteric
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What is the sympathetic subdivision of the PNS?
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Division of the autonomic nervous system that prepares the body for strenuous physical activity, such as might occur in emergency situations
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What is the parasympathetic subdivision of the PNS?
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Division of the autonomic nervous system that maintains resting functions of the internal organs, such as digestion
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What is the enteric subdivision of the PNS?
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Division of the autonomic nervous system that regulates the functions of the stomach and intestinal track.
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What are the different sensory systems?
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Visual, Auditory, Somatosensory, Olfactory, Vestibular
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What are receptors?
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a cell whose axon or dendrite is capable of transduction in a particular sensory modality (e.g. heat, light, sound, chemical).
In each sensory system, stimuli are transduced by receptors grouped together to form a sensory surface, such as the skin. |
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What is transduction?
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the conversion of stimulus energy to a neuronal signal (e.g. photoreceptor converts light into receptor potential).
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What is a relay nuclei?
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Groups of neurons located in the central nervous system that process signals from receptor neurons and transmit signals to the thalamus. Examples include retinal ganglion cells, the cochlear nuclei, and the dorsal columns of the spinal cord.
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What is the thalamus?
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Groups of neurons, organized into nuclei within the thalamus, which process signals from relay nuclei and transmit signals to the cerebral cortex.
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What is the primary cerebral cortex?
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Anatomically defined areas of the cerebral cortex that process signals from the thalamus and transmit signals to secondary cerebral cortex
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What is the secondary cerebral cortex?
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Anatomically defined areas of the cerebral cortex that process signals from primary sensory cortex and transmit signals to association cortex, motor cortex and subcortical structures.
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Stimulation of a receptor cell causes a change in the __________ of the cell's plasma membrane to a particular ion(s), which leads to either __________ or _________at the site of stimulation.
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permeability, depolarization or hyperpolarization
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What is receptor potential?
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Stimulation of a receptor cell causes a change in the permeability of the cell's plasma membrane to a particular ion(s), which leads to either depolarization or hyperpolarization at the site of stimulation.
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What are some actions of receptor potential?
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It can directly influence the release of neurotransmitter by the receptor cell, or cause the receptor axon to fire action potentials by depolarizing it above threshold.
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The magnitude of the receptor potential is influenced by the ....
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intensity of the stimulus
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Each type of receptor cell is sensitive to a particular category of stimulus energy, which defines its ________
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modality specificity
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The location on the receptor surface within which a stimulus (of the appropriate modality) can influence the activity of a sensory neuron is referred to as the __________ of that neuron.
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receptive field
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Sensory acuity is determined by......
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the density of receptors in the sensory map, the size of the receptive fields, and by a process that occurs in the central nervous system called lateral inhibition
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What are photoreceptors?
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Visual receptors, specialized cells (but neurons) located on the outer surface of the retina
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What are the two classes of cells in photorecptors?
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rods and cones
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Rods are sensitive to _______ of light (scotopic vision)
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low levels
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The cones are sensitive to_________ of light (photopic vision) and composed of three subclasses that are sensitive to light of different wavelengths.
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higher levels
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Photoreceptors contain specialized intracellular membranes, located in their outer segments, which can convert the absorption of light into a __________________
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hyperpolarizing receptor potential
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Hyperpolarizing receptor potential leads to a reduction in the amount of _________________
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neurotransmitter released onto the retinal neurons.
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What are the major components of the eye?
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cornea, pupil lens, aqueous humor, vitreous humor, retina, choroid, sclera, optic disc, optic nerve.
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Describe optics of the eye
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the lens inverts and focuses the visual stimulus onto the surface of the retina
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What are the cell types of the neuroanatomy of the eye?
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photoreceptors, bipolar cells, ganglion cells, horizontal cells, and amacrine cells.
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What is the most direct path for information about the visual stimulus to exit the eye?
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The photoreceptor to bipolar cell to ganglion cell circuit is the most direct path for information about the visual stimulus to exit the eye.
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What is phototransduction?
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the process by which energy from light is converted into an electrical (neural).
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What happens with phototransduction in the dark?
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high levels of intracellular cGMP keep the cGMP-gated Na+ channels open, Na+ enters through the cGMP-gated Na+ channel and the cell is depolarized. This depolarization results in a constituitive release of neurotransmitter.
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What happens with phototransduction in the light?
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light stimulation of rhodopsin leads to activation of a G protein (transducin). The activated G protein then activates a cGMP phosphodiesterase (PDE). The PDE hydrolyzes cGMP, thereby reducing its concentration. As cGMP levels drop, the cGMP-gated Na+ channels close, the cell hyperpolarizes, and the cell stops releasing neurotransmitter.
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Describe central processing of the visual system
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Afferent signals from the photoreceptors are relayed to the output neurons of the retina, the ganglion cells, which send their axons out of the eye to form the optic nerve. Half of the fibers in each optic nerve cross at a junction called the optic chiasm, and then project to the visual thalamus. This crossover insures that the left half of the visual field will be represented in the right thalamus and vice versa. The thalamic neurons project to the primary visual cortex, where information from the two eyes is first integrated. The primary visual cortex sends its projections to multiple secondary visual cortical areas. Processing in these areas is responsible for our perception of the visual world. The spatial relationships among the photoreceptors in the retina are preserved at each step of the pathway. In this manner a retinotopic map of the contralateral visual field is maintained at each stage of the pathway.
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What are hair cells?
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Auditory receptors, specialized ciliated cells (not neurons) located in the inner ear within a structure called the cochlea
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What is the cochlea?
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a fluid-filled chamber, connected to the eardrum (tympanic membrane), by way of the middle ear bones (malleus, incus, and stapes).
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The cochlea contains a specialized membrane called the ______ upon which the hair cells are located.
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basilar membrane
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When the tympanic membrane vibrates in response to changes in air pressure in the outer ear, the cilia on the upper surface of the hair cells are deflected when they come in contact with an overlying membrane called the __________
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tectorial membrane
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What is tonotopic organization?
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Hair cells are sensitive to particular frequencies of sound because they lie at particular locations along the basilar membrane. The position of maximal vibration along the basilar membrane varies according to the frequency of the sound, and thus a map of sound frequency is laid out along the surface of the basilar membrane.
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Describe central processing of the auditory system.
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Afferent signals from the hair cells are relayed to the output neurons of the inner ear whose axons form the auditory nerve. These axons enter the brainstem and project to relay nuclei that are innervated by both ears. This early binaural projection distinguishes the auditory system from the somatosensory and visual systems because information from the two ears is present at each level of the central pathway. The brainstem nuclei then project to the auditory thalamus, which in turn sends its projections to the primary auditory cortex and from there to the secondary auditory cortices. The spatial relationships among the hair cells in the cochlea are preserved at each step of the pathway. In this manner a tonotopic map of sound frequency is maintained at each stage of the pathway.
cochlea -> cochlear nuclei -> medulla -> midbrain -> thalamus -> 1o cortex -> 2 o cortices |
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Where are some places that somatosensory receptors are located?
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skin, skeletal muscles, tendons and ligaments.
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What are the categories of somatosensory receptors?
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touch (mechanoreceptors)
pain (nociceptors) temperature (thermoreceptors) proprioception (mechanoreceptors), which signals muscle tension and limb position. |
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What do Slowly adapting, or tonic receptors do?
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provides continuous information about the stimulus. Examples include muscle stretch receptors and joint proprioceptors.
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What do Rapidly adapting, or phasic receptors do?
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signal only changes in stimulus strength and filter out the sustained component. Examples include Pacinian corpuscles, which detect pressure and vibration.
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Describe central processing of the somatosensory system?
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Afferent signals from the skin, muscles and tendons are relayed to the CNS by receptor cells located in the dorsal root ganglia. The central projections of these cells enter the doral horn of the spinal cord and then project to the somatosensory thalamus on the other (contralateral) side of the brain. The recipient thalamic neurons then project to the primary somatosensory cortex, which in turn projects to the secondary somatosensory cortex. The perception of tactile stimuli takes place in these cortical and thalamic structures. The spatial relationships among the receptors on the skin surface are preserved at each step of the pathway. In this manner a topographic map of the body surface (somatotopic map) is maintained for each somatosensory modality. The crossover of the pathways insures that the left half of the body surface is represented on the right half of the brain and vice versa.
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What is the somatic motor system?
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The final common pathway for neural control of the skeletal musculature lies in the motor neuron pool located in the ventral horn of the spinal cord.
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The axons of these neurons project out the ventral root of the spinal cord and make synaptic contact with skeletal muscles at the ______________
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neuromuscular junction.
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What is the Neuromuscular Junction (NMJ)?
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The NMJ is a specialized synaptic contact between spinal motor neurons and skeletal muscle fibers.
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In the NMJ what is the site of contact is referred to as?
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motor end plate
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What is Myasthenia Graves?
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an autoimmune disease of the neuromuscular synapse. Symptoms include muscle weakness, particularly during sustained activity, commonly affecting the muscles that control the eyelids, facial expression and swallowing. In this disease the body’s immune system produces antibodies that attack Ach receptors. Treatment involves the use of Ach-esterase inhibitors such as neostigmine, which effectively prolong the action of synaptically released Ach by reducing the rate of its degradation.
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The simplest of these circuits mediates the reflex known as the _____
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stretch reflex.
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What is the primary motor cortex?
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The primary motor cortex, located on the precentral gyrus, contains a somatotopic map of the skeletal musculature. A subset of the neurons in the motor cortex project directly to the spinal cord where they synapse on and excite spinal motor neurons, as well as other classes of motor neurons and interneurons. This projection forms a large axonal pathway referred to as the corticospinal tract.
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What is the primary motor cortex responsible for?
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The primary motor cortex is responsible for finely coordinated voluntary movements of the distal musculature.
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What are the supplementary motor and promotor cortices?
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These are motor cortical areas that project to and are located anterior to the primary motor cortex. They are involved in complex motor sequences and movement preparation.
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What is the cerebellum?
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Large neural lobe located on the lower posterior region of the brain. The cerebellum is also involved in numerous functions, and is particularly important in the control of motor coordination. Heavily interconnected with the cerebrum, particularly the cerebral cortex.
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What is the cerebellar cortex?
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The outer, highly folded surface of the cerebellum. This is a layered structure covering nearly the entire cerebellum. Much of cerebellar function takes place here.
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What is the deep nuclei?
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Nuclear structures, analogous to the Basal Ganglia in the cerebrum, that lie below the cortex in the depth of the cerebellum. Provide a relay for the output of the cerebellar cortex
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What is the role of the cerebellum?
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The role of the cerebellum is to make refinements to ongoing movements. It does so by comparing a copy of the instructions for the intended movement, relayed from cortex, with information on how the actual movement is proceeding, relayed from receptors in the joints and muscles. The cerebellum is also partly responsible for learning skilled movements, such as riding a bike of playing the piano.
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What is the basal ganglia involved in?
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They are involved in several aspects of motor planning, principally in initiating complex movements.
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What is the basal ganglia?
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A set of large nuclei lying in the center of the brain. These structures are highly interconnected with the cerebral cortex and the thalamus
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What are some neurodegenerative diseases?
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Include multiple sclerosis and Parkinson’s disease. Multiple sclerosis is an autoimmune disease that causes demyelination of neurons in the cerebellum. Patients therefore have difficulty making precise movements and display action tremors, or tremors that only occur during voluntary movement. Parkinson’s disease is a disease that destroys dopaminergic neurons in the substantia nigra of the basal ganglia. Patients have difficulty initiating movements and display resting tremors that occur in the absence of voluntary movement.
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What do Higher Order Sensory and Motor Areas of the Cortex do?
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These are areas of the cerebral cortex that provide input to motor areas or receive and integrate output from sensory areas.
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What are the different areas of the Higher Order Sensory and Motor Areas of the Cortex?
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Posterior parietal cortex
Extrastriate Cortex Premotor and Supplementary Motor Cortex |
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What is the Posterior parietal cortex?
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Located posterior to the postcentral gyrus and receives input from the somatosensory cortex.
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What happens when the Posterior parietal cortex is damaged?
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When damaged can lead to a syndrome of sensory neglect and attention deficits.
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What is the extrastriate cortex?
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Located anterior to and receives input from the primary visual cortex.
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What happens when the extrastriate cortex is damaged?
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When damaged can lead to a syndrome of "cognitive blindness" (e.g. an inability to see things move, or recognize faces etc ...).
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What is the premotor and supplementary motor cortex is damaged?
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Located anterior to the precentral gyrus and sends output to the primary motor cortex. When damaged can lead to a deficit in motor planning and coordination of complex movements.
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What is the association cortex?
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Remaining areas of cerebral cortex are referred to as association areas. These regions integrate multiple sensory, motor and cognitive processes to enable humans and animals to carry out complex functions.
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What are the different association areas?
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Parietal-temporal-occipital
Language areas Prefrontal association areas Limbic association area |
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What are the language areas?
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These areas of the cerebral cortex are located in the left hemisphere in approximately 97% of the population.
Wernicke's Area Broca's Area |
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What is Wernicke's area?
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Located ventral and posterior to auditory cortex and receives input from the auditory, visual and somatosensory cortices. When damaged results in a specific deficit in language comprehension.
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What is Broca's area?
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Located in the ventral and posterior region of the left frontal lobe and sends output to the motor areas of the cortex. When damaged results in a specific deficit in speech production.
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What is the prefrontal association areas?
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Located anterior to the premotor regions in the frontal lobe. Receives input and provides output to many areas of the cerebral cortex. When damaged can result in deficits of planning of voluntary activity, personality changes, and inability to gage appropriate social behavior.
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What is the limbic association area?
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Located in multiple regions of the parietal, frontal and temporal lobes and forms a major component of the limbic system. Receives input from and sends output to many cortical and subcortical structures. When damaged can result in severe deficits in long-term memory formation.
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What is the limbic system?
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A system of cortical and subcortical structures that form a loosely defined ring around the thalamus and are involved in complex aspects of emotion, motivation, learning and memory.
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What is the amygdala?
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A collection of nuclei located at the anterior end of the hippocampus, deep within the temporal lobe. Receives input from and provides output to many subcortical and cortical structures. Is thought to be involved in the regulation of emotional responses such as fear.
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What is the hippocampus?
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A primitive, elongated cortical structure located within the temporal lobe. Anatomically connected with other parts of the limbic system and cerebral cortex. Is thought to be involved in memory formation, spatial guidance of behavior and often is the location in the brain that gives rise to epileptic activity
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What is the hypothalamus?
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A collection of nuclei located ventral to the thalamus. Receives and sends widespread anatomical connections with many other cortical and subcortical structures. Is well established to play many important roles in homeostatic function and hormonal control. When certain regions are damaged, emotional and motivational deficits occur. In rats certain hypothalamic nuclei are sexually dimorphic - on average, different in size between males and females - and may contribute to gender-specific behavior. In humans, sexual dimorphisms of hypothalamic nuclei are less dramatic, and their role in sexual behavior less clear.
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