Wednesday, February 25, 2009 Lecture

The lecture focused mainly on the autonomic nervous system and touched upon other topics such as secondary messenger systems and the major anatomical landmarks of the eye and ear. All impulses of the autonomic nervous system are efferent impulses. The two major divisions of the autonomic nervous system are the parasympathetic (cranio-sacral) and the sympathetic (thoraco-lumbar) systems. The parasympathetic system is responsible for the “Rest and Digest” reflex and is the restorer of homeostasis. The sympathetic nervous system is responsible for the “Fight or Flight” response. Both systems target smooth muscle, cardiac muscle, and glands. There are two neurons involved in the parasympathetic and sympathetic nervous systems: the pre-ganglionic neuron and post-ganglionic neuron. They are named this because they are before or after a ganglion, or bundle or nerve fibers. The pre-ganglionic neuron always releases Ach and excites the second neuron. The receptors that lie in the post-ganglionic neuron and target cell are cholinergic receptors. Cholinergic receptors include muscarinic (excitatory or inhibitory) and nicotinic (excitatory) and bind to acetylcholine. Another type of receptors is Adrenergic Receptors, which include Alpha 1, Alpha 2, Beta 1, and Beta 2 receptors, each affecting their target organs in different ways. Adrenergic receptors bind to epinephrine and norepinephrine. Secondary Messenger pathways utilize G-proteins to “carry” their message from the receptor to the channels located elsewhere in the cell. There are two different pathways in secondary messenger systems: pKA and pKC.

We also studied the major landmarks of the external, middle, and inner ear.

I’m sure all of us have either had an ear infection or known someone who has had one. If you’ve experienced one yourself you know that it causes a dull pain and can last several days or weeks. I researched exactly what causes an ear infection and found out that it is typically an infection of the middle ear (where the malleus, incus, stapes, pharyngotympanic tube, and the tympanic membrane are located). Middle ear infections are caused by the swelling of the pharyngotympanic tube (which connects the pharynx and the middle ear). This swelling can lead to a blockage of the tube, which traps fluid inside your middle ear where germs and bacteria cause an infection. Ear infections are more typical amongst children because their Eustachian tube is smaller and more easily blocked. Antibiotics can treat the infection.