I know it's been a long time since I last posted, but here's some more notes that I forgot (or more likely couldn't be bothered) to upload earlier.
1. How does sympathetic stimulation prepare an individual for fight?
The actions of the sympathetic nervous system speed up the heart rate, dilate the pupils to increase the amount of light entering the eye, increases the rate of breathing and so on, in order to get more oxygen and nutrients to the brain and muscles and thus prepare the body to respond to whatever stimulus has initiated the fight-or-flight response.
2. What is the effect of parasympathetic stimulation on the cardiac muscles? On respiration?
The parasympathetic nervous system has the opposite effect of the sympathetic nervous system: that is, it slows down heart and respiration rates.
3. What does the presence of more rods at the periphery of the visual field do to acuity of vision in that area?
Rods are photoreceptors (light receptors) that work best in dim light, though only see in black and white. Their location at the periphery of the visual field mean that, at night, our peripheral vision is better than our normal vision. This allows us to detect predators and other things moving around in the darkness.
4. Discuss convergence and divergence as they refer to the circuits of the rods and cones. Which confers greater visual acuity? Sensitivity?
Multiple rods "converge" into one nerve cell- i.e. information from multiple rods is sent to the same nerve cell. This gives better sensitivity at the expense of visual acuity. On the other hand, cones have a lot of receptors to gain the light that they need to function, which provides higher visual acuity at the expense of sensitivity.
5. Describe the components of the middle ear.
The middle ear is home to some of the smallest bones and muscles in the body. The boundary between the outer ear and middle ear is the tympanic membrane, or eardrum, which vibrates in response to sound. Attached to this is the first ossicle (small bone): the malleus (or hammer). This articulates with the incus (anvil), which in turn articulates with the stapes (stirrup). The stapes is then attached to the oval window, which is the membrane forming the boundary between the middle and inner ear.
There are several small muscles that can contract to hold the bones steady during prolonged exposure to loud sounds. One of these is the tensor tympani muscle controlled by cranial nerve V. This muscle holds the malleus steady. Another of these is the stapedius muscle, which is the smallest muscle in the body. It is attached to the stapes and is controlled by cranial nerve VII.
Another important component of the middle ear is the eustachian tube, which connects the middle ear to the back of the mouth. Air can travel through here to equalise the pressure in the ears. This is why blocking your nose and blowing hard can help relieve pain when dealing with pressure changes (such as during takeoff and landing on an aeroplane).
6. How is balance transmitted from the semicircular canals to the brain? Is this static or dynamic equilibrium?
There are three semicircular canals in each ear, oriented in different directions. These canals detect dynamic equilibrium, which is changes in motion (as opposed to static equilibrium, which refers to the orientation of the body). The canals are filled with fluid and lined with cilia, and when the body moves, the fluid in the canals pushes the cilia. A structure called the crista, located in the ampulla (widest section of the canal) detects motion and sends off impulses via its nerve fibres to the brain. (I think that's how it works, anyway- I'm not 100% sure.)
7. What is the anatomic basis of the differences between short-term and long-term memory?
In short-term memory, there are no anatomical changes (as far as we know). No neurons are added and the structure of the neurons does not change. Short-term memory is probably simply a result of short-lived electrical and chemical reactions in the brain. Long-term memory, on the other hand, is signalled by certain anatomical changes, such as more and larger presynaptic terminals capable of carrying more neurotransmitters. Long-term potentiation (LTP) is an enduring increase in synaptic strength in which connections are activated more easily.
8. Describe the differences between movements in patients with Parkinson's disease (rest tremor) and cerebellar ataxia (intention tremor).
Patients with Parkinson's sometimes exhibit rest tremor, which consists of small, shaky movements when the patient is at rest. These tremors, however, go away when the patient carries out some action intentionally, such as reaching out to grab something. Patients with cerebellar ataxia (damage to the cerebellum), on the other hand, exhibit intention tremor, which occurs when patients are carrying out an action intentionally. Since the cerebellum is not functioning properly, patients with cerebellar ataxia find it difficult to judge how much movement they need to carry out some task, so they may continuously over-correct their movements. For instance, if they reach out to grab something and their first movement is a little bit too far over to the left, they might swing their arm wildly over to the right, then wildly over to the left, and so on.
No comments:
Post a Comment