Sensation & Perception: Physiology

12 flashcards · Biology · by lakesare

1. Name 2 (widely wrong) ideas of where the brain was thought to be located during the ages?

   Heart - Aristotle Pineal gland - Rene Descartes Brain - Thomas Willis, 1664 In the fourth century B.C. the philosopher Aristotle (384–322 B.C.) stated that the heart was the seat of the mind and the soul.In the early 1630s the philosopher Rene Descartes, although still accepting the idea of fl owing spirits, specified the pineal gland, which was thought to be located over the ventricles, as the seat of the soul.In 1664 Thomas Willis, a physician at the University of Oxford, published a book tit…

2. Nerve VS axon?

   Nerve consists of many axons. Nerves contain many nerve fibers. The optic nerve transmits signals out the back of the eye. Shown here schematically in cross section, the optic nerve actually contains about 1 million nerve fibers.

3. How is charge of the neuron such as this measured by microelectrodes?

   Difference in charge between 2 electrodes is measured. Recording electrode: located where the electrical signals will occur. Reference electrode: located some distance away so it is not affected by the electrical signals. The difference in charge between the recording and reference electrodes is displayed on an oscilloscope, which indicates the difference in charge by a small dot that creates a line as it moves across the screen.

4. What's resting potential?

   The value oscilloscope records which stays the same when there is no signal in the neuron. In other words, the inside of the neuron is 70 mV negative compared to the outside, and remains that way as long as the neuron VL 3 is at rest.

5. What happens inside the neuron as the action potential rises?

   As the nerve impulse, indicated by the red band, passes the electrode, the inside of the fiber near the electrode becomes more positive. This positivity is the rising phase of the action potential.

6. What ions are the solutions outside VS inside the axon rich in?

   outside the axon: Na+ (positively charged sodium ions) inside the axon: K+ (positively charged potassium ions) The solution outside the axon of a neuron is rich in positively charged sodium (Na+) ions, whereas the solution inside the axon is rich in positively charged potassium (K+) ions.

7. What's selective permeability?

   Selective permeability occurs when a membrane is highly permeable to one specific type of molecule, but not to others

8. What is action potential caused by chemically?

   Stimulation of the receptor triggers a process that causes the membrane to become selectively permeable to sodium, so Na flows into the axon. When the action potential reaches 40 mV, the membrane suddenly becomes selectively permeable to K, so potassium flows out of the axon.

9. Why is there an upper limit to the number of impulses per second that can be conducted down an axon?

   Because of the refractory period - the interval between the time one nerve impulse occurs and the next one can be generated in the axon. Because the refractory period for most neurons is about 1ms, the upper limit of a neuron’s firing rate is about 500 to 800 impulses per second.

10. What happens to action potential when intensity of the stimulus increases?

    Rate of firing increases (and voltage stays exactly the same).

11. What's spontaneous activity of the neuron?

    Another important property of action potentials is illustrated by the beginning of each of the records in Figure 2.10. Notice that a few action potentials are occurring even before the pressure stimulus is applied. The action potentials that occur in the absence of stimuli from the environment is called spontaneous activity. This spontaneous activity establishes a baseline level of fi ring for the neuron. The presence of stimulation usually causes an increase in activity above this spontaneous…

12. Specificity coding VS distributed coding?

    Specificity coding - object is represented by the firing of one type of very specialized neuron, 'Jennifer Aniston neuron' Distributed coding - a particular object is represented by the firing of groups of neurons. How faces could be coded by specificity coding. Each face causes one specialized neuron to respond. One neuron responded to pictures of actress Halle Berry. This neuron responded not only to photographs of Halle Berry, but to drawings of her, pictures of her dressed as Catwoman from…