Unit 3 lecture exam short answers

Difference between spatial and temporal summations.

Spatial summation occurs due to convergence of neurons, 2 or more subthreshold graded potentials from different presynaptic neurons can be summed if they arrive at the trigger zone close enough together in time, long distance between the distal ends of the dendrites and the initial segment of the axon, there is ample opportunity for synaptic potentials to summate, same stimulus, repeated close together in time. Temporal summation is when successive rapid bursts of activity of a single presynaptic axon can cause corresponding bursts of neurotransmitter release, resulting in successive waves of EPSP (or IPSP) that summate w/ each other as they travel to the initial segment of the axon.

Steps of hearing pathway.

Sound waves are funnels through the external ear and hit the tympanic membrane, tympanic membrane starts vibrating and transfers the vibration to malleus, incus, and stapes which in turn vibrates and amplifies the sound waves, the stapes sits on the oval window and vibration of the stapes causes pressure waves in the fluid with the cochlea, this causes the cochlear duct to bend at particular areas (based on the frequency of sound), as the cochlear duct bends, the hair cells bend and stimulates the associated sensory neurons and the info (action potentials) travel via the cochlear branch of the vestibulocochlear nerve (CN VIII) to the temporal lobe of the brain, remaining pressure waves exit the inner ear via the round window.

What is myopia, hyperopia and astigmatism? How can they be fixed? (review your lab notes for this)

Myopia is when rays focus in from of retina (nearsightedness) and concave lens corrects nearsightedness. Hyperopia is when rays focus behind retina (farsightedness) and convex lens corrects farsightedness. Astigmatism is when blurry vision occurs due to irregularly shaped cornea or lens and uneven lens corrects astigmatism.

Explain the functioning of alpha 1 and beta 2 adrenergic receptors on blood vessels.

Alpha 1 receptors are usually excitatory and are coupled to G proteins. When epinephrine or norepinephrine bind to alpha 1 receptors on blood vessels, it leads to contraction of the smooth muscle in the walls of these vessels. This contraction narrows the diameter of the blood vessels, resulting in vasoconstriction. Beta 2 receptors on blood vessels, when bound by epinephrine (especially at lower concentrations), initiate a G protein-coupled signaling pathway that leads to vasodilation. This effect is balanced by the vasoconstricting effects of alpha 1 receptors also present on most blood vessels. Because beta 2 receptors on blood vessels have a higher affinity for epinephrine, in the presence of low concentrations of epinephrine, these beta 2 receptors are preferentially populated. This leads to vasodilation.

Where do we find alpha 2 adrenergic receptors? Explain how they work.

Alpha 2 adrenergic receptors are primarily found in the presynaptic terminals of sympathetic nerve endings and in the central nervous system. They function by inhibiting the release of norepinephrine, which reduces sympathetic outflow and lowers blood pressure. They have both norepinephrine and epinephrine.