USABO practice tests

2003:

  1. HIV converts RNA to DNA with reverse transcriptase
  2. RNA transcription involves binding of the RNA polymerase to the promoter region, which is located 5’ to the gene as transcription is 5’--> 3’
  3. Prokaryotes vs. Eukaryotes:

   
   1. Because prokaryotes have no nuclear membrane, they can conduct transcription and translation at the same time

      
      1. Don’t need to undergo RNA processing, because don’t have intro sequences
      2. Most DNA is circular
   2. Because eukaryotes do have a nuclear membrane, transcription is seperated in specialized compartment because it needs to undergo extensive RNA processing

  1. MEMORIZE THE AMINO ACIDS

   
   1. In the transmembrane region of proteins imbedded in the cell membrane, you would expect a nonpolar amino acid like trytophan

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  2. REMEMBER HOW TO DO THIS
  3. Astroyctes: Astrocytes play a critical role in normal function of the mammalian nervous system. Astrocytes regulate synaptic transmission and plasticity, protect neurons against toxic compounds, and support metabolically to ensure their optimal functioning.

   
   1. The most abundant cells in the CNS
   2. Microglia cells are the immune cells of the central nervous system and consequently play important roles in brain infections and inflammation.

  1. Human Physiology - Neurons & the Nervous System II :

   
   1. There are 31 pair of spinal nerves & each has a dorsal root and a ventral root. The dorsal root is sensory (all neurons conduct impulses into the spinal cord) while the ventral root is motor (all neurons conduct impulses out of the spinal cord). The dorsal root has a ganglion that contains the cell bodies of the sensory neurons that pass through the dorsal root. Each spinal nerve includes numerous sensory, or afferent, & motor, or efferent, neurons. Some of these neurons are classified as somatic, and these neurons conduct impulses to or from 'somatic' structures (skin, skeletal muscles, tendons, & joints). Other neurons are 'visceral', and these conduct impulses to or from 'visceral' structures (smooth muscle, cardiac muscle, and glands). Thus, all neurons in spinal nerves (& the peripheral nervous system) can be placed in one of four categories:

  • Somatic afferent
  • Somatic efferent
  • Visceral afferent
  • Visceral efferent
  • Somatic afferent neurons are sensory neurons that conduct impulses initiated in receptors in the skin, skeletal muscles, tendons, & joints. Receptors in the skin are responsible for sensing such things as touch, temperature, pressure, & pain and are called exteroceptors. Receptors in the skeletal muscles, tendons, & joints provide information about body position & movement and are called proprioceptors. Somatic afferent neurons are unipolar neurons that enter the spinal cord through the dorsal root & their cell bodies are located in the dorsal root ganglia.
  • Somatic efferent neurons are motor neurons that conduct impulses from the spinal cord to skeletal muscles. These neurons are multipolar neurons, with cell bodies located in the gray matter of the spinal cord. Somatic efferent neurons leave the spinal cord through the ventral root of spinal nerves.
  • Visceral afferent neurons are sensory neurons that conduct impulses initiated in receptors in smooth muscle & cardiac muscle. These neurons are collectively referred to as enteroceptors or visceroceptors. Visceral afferent neurons are unipolar neurons that enter the spinal cord through the dorsal root & their cell bodies are located in the dorsal root ganglia.
  • Visceral efferent neurons are motor neurons that conduct impulses to smooth muscle, cardiac muscle, & glands. These neurons make up the Autonomic Nervous System. Some visceral efferent neurons begin in the brain; others in the spinal cord. Because we're focusing on spinal nerves right now, we'll focus on those that begin in the spinal cord. It always takes two visceral efferent neurons to conduct an impulse from the spinal cord (or brain, in some cases) to a muscle or gland:
      * Visceral efferent 1 (also called the preganglionic neuron) is a multipolar neuron that begins in the gray matter of the spinal cord, which is where its cell body is located. This neuron leaves the cord through the ventral root of a spinal nerve, leaves the spinal nerve via a structure called the white ramus, then ends in an autonomic ganglion (either sympathetic or parasympathetic). In the ganglion, the visceral efferent 1 neuron synapses with a visceral efferent 2 neuron.
        * Visceral efferent 2 (also called the postganglionic neuron) is also a multipolar neuron and it begins in the sympathetic ganglion (which is where its cell body is located). Visceral efferent 2 neurons may exit the ganglion through the gray ramus, then proceed to some visceral structure (smooth muscle, cardiac muscle, or gland).
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  2. On the other extreme are species that are highly K-selected. K refers to the carrying capacity, and means that the babies are entering a competitive world, in a population at or near its carrying capacity.

   
   1. r and K selection

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