Physiology midterm I
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| How did neurons change through evolution? | Complexity of organization diverse in form but similar between phyla. Nerve nets were simplest NS that were unpolarized (bidirectional). Bilateral symmetry initiated cephalization and centralization which resulted in a more complex NS
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| What are the main functions of neurons | 1) Receiving sensory inputs at dendrites
2) Integration at cell body
3) Conduction of signal along axon
4) Generating output at presynaptic terminal
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| What types of neuroglia are found in the CNS? | - Oligodendrocytes are ensheathing glial cells which insulates axon and increases impulse velocity
- Astrocytes associate with blood capillaries and supply neurons with nutrients
- Microglial cells remove pathogens
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| What are the function and composition of the spinal cord? | Composed of white matter (composed of axons) and grey matter (contains interneurons). It is the centre for reflexes and a way of communication between brain and spinal nerves
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| What is the main difference between the somatic system and autonomic system? | somatic system controls skeletal muscles and signals travel along a single motor neuron. Autonomic system controls cardiac and smooth muscles and use a two-neuron relay
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| What is the difference between sympathetic and parasympathetic divisions of autonomic division? | Sympathetic - ganglion near source and uses norepinephrine as NT
Parasympathic - ganglion is nearer target organs and are Cholinergic neruons
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| How is the Nerst equation useful? | Relates concentration differences across membrane to membrane potential at equilibrium for individual permeating ions. Larger concentration diff = larger equilibrium membrane potential
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| How is the Goldman equation different from the Nerst equation? | Goldman equation determines resting membrane potential for ALL ions (takes into account permeability) while Nerst only talks about individual ions
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| Explain what causes "equilibrium" membrane potential (why is membrane inside negative?) | Higher concentration of K+ ions causes K+ to want to diffuse out of cell. This will cause negative anions to line along inside of membrane. Negative charge will pull back K+ into cell. Equilibrium will be reached eventually (will depend on concentration)
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| How does capacitance and resistance retard membrane voltage changes and limit spread of graded potentials? | 1) Current must first distribute in capacitance (causes changes to occur more gradually)
2) resistance causes some current to be lost via leakage channels
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| What is meant when we say action potentials are all or none events? | - Depolarization below threshold produces no impulse
- Depolarization above threshold produces complete impulse
- Impulses are alike in amplitude and duration
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| How does axon diameter affect AP conduction velocity | Larger axons have more membrane surface area which lowers Rm and Ri. Lambda increases thus which increases conduction velocity
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| What are advantages of nonspiking neurons and pacemaker potentials? | Nonspiking neurons do not produce action potentials and are shorter - do not need spike. Pacemaker are spontaneous and do not need external depolarization
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| What are connexons and how are they important in synapses? | electric currents can flow directly through connexons that make membrane close. Connexons provide low resistance path for current flow
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| What are some advantages of chemical vs electrical synapses? | 1) current flow can be amplified
2) can be excitatory or inhibitory
3) One-way
4) more modifiable properties (learning and memory)
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| Describe process of NT release from chemical synapses? | 1) Action potential depolarizes terminal
2) depolarization opens Ca2+ voltage channels and Ca2+ enters
3) Calcium triggers exocytosis of vesicle
4) NT diffuse synaptic cleft and bind postsynaptic
5) NT binding initiates response in postsynaptic cell
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| Compare and contrast Ionotropic vs Metabotropic Receptors | Iono - open ion channels causing direct flow of ions - fast communication
Metabo - binds to GPCR that activate G proteins which produce second messengers - slow but long lasting communication
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| What are synaptic potentials? | Graded changes in membrane potential of postsynaptic cell by NT binding - Can be excitatory (depolarizing) or inhibitory (hyperpolarizing)
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| What is neuronal integration? | Process by which a postsynaptic cell summates its EPSPs and considers distance from trigger zone to produce action potential
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| What is synaptic plasticity? | changes in synaptic strength over time - result from change in amount of NT released (depend on calcium influx)
- forms the basis for habituation and sensitization
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| What difference between semicircular canals and otilith organs? | Both involved in detection of balance. Semicircular canals detect angular movement of the head. Otilith organs detect linear movement and acceleration
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| How does the head act as a acoustic shadow? | As sound arrives at one ear, it hears it first - time difference between ears.
Sound louder at one ear than other
Used to determine location of sound
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| What is homeostasis? | Internal constancy and the physiological regulatory systems that make adjustments to maintain it
- opposes or reinforces deviations of a controlled variable from a set point
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| How does temperature define the environment an animal lives in? | Most animals are temperature conformers.
In aquatic - lowest limit -1.9 (freezing of seawater) and highest 35-45deg
In terrestrial - highest 50 lowest -90 or -70 (number of temp conformers decrease with latitude)
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| Why is oxygen a problem in aquatic environments? | supply of O2 in water is the O2 that is dissolved in water. O2 has low solubility. Concentration depends on many factors. Can be used up quickly by organisms. Thermoclines cause density layering which prevents mixing
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| Examples of evolutionary processes | - Gene flow
- Genetic drift
- Mutations
- Natural selection
- Non random mating
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| What determines the maximum reaction velocity? | number of active enzymes and the catalytic effectiveness (number susbtrate molecules converter per unit time by each enzyme when saturated)
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| what is the difference between homotropic and heterotropic cooperativity in enzymes? | Homotropic - binding of ligand facilitates or inhibits binding of the same ligand to same enzyme
Heterotropic - binding of one ligand influences other types of ligands to same enzyme
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| How can the types and amounts of enzymes synthesized be regulated? | Gene expression and enzyme degradation
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| What are the advantages of modulating catalytic activities of existing enzymes? | provides instant acceleration or deceleration of enzymes by positioning of certain enzymes to produce rate-limiting reactions or branch point reactions
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| What is the direction of osmosis? | Water moves from area of lower osmotic pressure to area of higher osmotic pressure
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| What are the gradient interactions when talking about the transport of solutes across membranes? | Electrochemical equilibrium is reached when concentration and electrical effect are equal but opposite
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| How does facilitated diffusion differ from simple diffusion? | moves ORGANIC solutes across membrane. Involves non-covalent binding with binding sites on transporter proteins
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