state exam

• The neuron: structure and types

  • Soma
  • Axon
  • Dendrites
  • Myelin sheath
  • Axon terminals

  
• Types of nerve fibers based on function

  • Sensory (usually pseudo unipolar)
  • Motor (multipolar, lower motor neurons (spinal cord-muscles), upper motor neurons (spinal cord-brain)
  • Interneurons (short axons, multipolar)

  
• Electrical synapse


  Direct physical connection between the presynaptic neuron and the postsynaptic neuron, allowing current to flow directly from one cell into another. Transmits signals more rapidly than chemical synapses.
• Chemical synapse


  Involves release of chemical messengers called neurotransmitters, which carry information from the presynaptic neuron to the postsynaptic cell.

  
• Sodium potassium pump


  1. Inserts 2 potassium ions for every 3 sodium ions taken out, maintaining the cell's polarity at around -70mV (resting potential)

  2. When cell is stimulated, potassium channels are blocked and sodium channels open, depolarizing the cell to +30mV

  3. After stimuli ends, potassium channels open, repolarizing the cell, which may undershoot and become hyperpolarized before returning to resting potential
• EPSP


  Excitatory postsynaptic potential
• IPSP


  Inhibitory postsynaptic potential
• Neurotransmitter release


  1. Action potential arrives at axon terminal, activating voltage-gated calcium channels

  2. Ca2+ rushes in, allowing synaptic vesicles to fuse with the membrane and release neurotransmitter into the synaptic cleft

  3. Neurotransmitter binds to receptors on postsynaptic cell, opening or closing ion channels

  
• Types of nerve fibers (general classification)

  • Type A (large and medium-sized myelinated fibers)
  • Type C (small unmyelinated fibers)

  
• Types of nerve fibers (sensory classification)

  • Group Ia (fibers from muscle spindle annulospiral endings)
  • Group Ib (fibers from Golgi tendon organs)
  • Group II (fibers from cutaneous tactile receptors and muscle spindle flower-spray endings)
  • Group III (fibers carrying temperature, touch, and pain)
  • Group IV (unmyelinated fibers carrying pain, itch, temperature, touch)

  
• Neuronal signal transmission


  1. Resting potential (high K+, low Na+)

  2. Depolarization (action potential, influx of Na+)

  3. Repolarization (K+ channels open)

  
• Excitatory ion channel synapses

  Neuroreceptors are Na+ channels, local depolarization can initiate action potential

  
• Inhibitory ion channel synapses

  Neuroreceptors are Cl- channels, hyperpolarization makes action potential less likely

  
• Non-channel synapses


  Neuroreceptors are membrane-bound enzymes, activation can affect sensitivity of ion channel receptors
• Neuromuscular junctions


  Synapses between motor neurons and muscle cells, always use acetylcholine and are always excitatory
• Electrical synapses


  Membranes of two cells touch, allowing action potential to pass directly from one to the other
• Most abundant ions in neurons and surrounding fluid

  • Positively charged (cations): Sodium (Na+), Potassium (K+)
  • Negatively charged (anions): Chloride (Cl-), Organic anions
• Resting membrane potential


  Stable and unchanging in non-excitable cells, can fluctuate in excitable cells like neurons and muscle
• Signal transduction pathway


  1. Reception (binding of extracellular signaling molecules to cell receptors)

  2. Induction (binding initiates events in transduction pathway)

  3. Response (specific cellular response to signaling)

  4. Resetting (signal molecule detaches, stopping response)

  
• Sensory modality


  One aspect of a stimulus or what is perceived, e.g. light, sound, temperature, taste, pressure, smell
• Specificity


  Each nerve tract terminates at a specific point in the central nervous system, and the type of sensation felt is determined by the point it leads to
• Somatosensory system


  Part of the sensory system concerned with conscious perception of touch, pressure, pain, temperature, position, movement, and vibration, relayed via a 3-neuron pathway to the sensory cortex

  
• Skeletal muscles are responsible for active motion, made up of individual muscle fibers containing multiple nuclei
• Skeletal muscle components


  • Plasma membrane (sarcolemma)
  • Cytoplasm (myoplasm/sarcoplasm)
  • Endoplasmic reticulum (sarcoplasmic reticulum)
  • Fiber -> Myofibrils -> Myofilaments
• Skeletal muscle proteins


  • Contractile: Myosin, Actin
  • Structural: Alpha actinin, Titin
• Muscle contraction


  Myosin heads attach to actin, contracting the actin and causing muscle movement
• Sarcomere


  Functional unit of skeletal muscle, region between two Z-discs with light and dark bands
• Neuromuscular junction


  Transmitter manufactured in neural cell, released at junction, binds to receptors on muscle cell, causing excitable reaction
• Skeletal muscle action potential

  Stable resting potential at -90mV, threshold for contraction around -50mV, "all or nothing" response
• Calcium release and reuptake in muscle contraction

  1. DHP receptor changes shape with action potential, allowing Ca2+ exit from sarcoplasmic reticulum

  2. Ca2+ binds to troponin, exposing actin binding sites for myosin

  3. After action potential, DHP receptor closes, Ca2+ pumped back into sarcoplasmic reticulum
• Hierarchical organization of motor system

  Higher-order areas control global tasks, lower levels program individual muscle movements
• The motor system hierarchy consists of the spinal cord, brain stem, motor cortex, and association cortex, with side loops through the basal ganglia and cerebellum

  
• Hormonal regulation follows general rules, and hormones play key roles in insect development and molting, as well as in the human hypothalamo-hypophyseal system

  
• Evolution of nutrient and gas transport in animals includes cyclosis, gastrovascular systems, and open vs closed circulatory systems, with differences in vertebrate heart anatomy and myogenic rhythm generation
• Properties of red blood cells (erythrocytes)

  • Disk-shaped, 7 micrometers diameter, 5.4 million/μL in males, 4.8 million/μL in females, lifespan 100-120 days, no nucleus/mitochondria/Golgi
• Hemoglobin


  Protein in red blood cells with 4 subunits (2 alpha, 2 beta) and heme groups that can bind 4 oxygen molecules
• Factors affecting hemoglobin oxygen saturation

  • pH
  • CO2 levels
  • Concentration
  • Temperature
  • Diphosphoglycerate level
• Ways CO2 is transported in blood

  • Dissolved in plasma
  • Bound to hemoglobin
  • As HCO3-
• Platelet (thrombocyte) functions


  • Induce vasoconstriction
  • Form physical platelet plug
  • Secrete clotting factors and form fibrin meshwork
• Platelet plug formation


  1. Inactivated platelets adhere to collagen (directly or via von Willebrand factor)

  2. Platelets become activated, rearrange membrane and secrete contents