General Interview Questions - Physiology

What is meant by homeostasis?

What is meant by metabolism?
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1. All animal cells have an electrical potential across their plasma membrane; this is known as the resting potential.  It arises from the concentration gradients of Na+ and K+ across the membrane, established and maintained by the action of the Na+, K+ ATPase, and the plasma membrane's differential permeability for Na+ and K+
2. Excitable cells, such as neurons and muscle cells, have voltage-gated ion channel proteins in their plasma membrane.  Activation and inactivation of these channels gives rise to a traveling wave of potential change across the plasma membrane called the action potential .
3. Action potentials have a constant amplitude.  The cells of the nervous system (neurons) encode and transmit information primarily through the frequency and patterns of action potentials, not in terms of action potential size .
4. Action potentials move along neurons with a distinct directionality.  They generally arise in the region adjacent to the neuronal cell body (the soma) known as the axonal hillock.  They pass down the axon .
5. Neurons interact with one another, or with muscle or gland cells, through structures known as synapses.  At a chemical synapse a chemical neurotransmitter is released by the presynaptic cell and binds to neurotransmitter receptor proteins on the surface of the post-synaptic cell.  At an electrical synapse, the electrical wave in the presynaptic cell is directly passed to the post-synaptic cell through gap junction-like membrane proteins .
6. The binding of the neurotransmitter to neurotransmitter receptor can either induce (excite/depolarize) or inhibit (hyperpolarize) the generation of action potentials or other response (contraction of muscle cells, release of hormones by exocrine cells) in the post-synaptic cell .
7. The activity of a synpase is determined by the rate of transmitter release and removal, by either uptake or destruction.
8. Typically, synapses are made on the non-axonal parts of a neuron, known as the dendrites and soma.   Generally these regions cannot generate action potentials.  The activity of the synaptic neuron will be determined by whether the net synaptic inputs lead the depolarization of the hillock region above a 'threshold'.  In this way, a neuron acts to integrate the incoming signals that impinge upon it .
9. Complex behaviors, including memory and consciousness, are generated through the electrical and chemical activities of networks of neuronal interactions .

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