MODULES

TASTE & SENSATION

 

If you can taste it as bitter, you’re a supertaster. Only 1 person in 4 is a supertaster.

 

The fungiform pupilli are little sprouts on the tongue. Each one of them has about 12 taste buds with nerve fibers connected to the brain. Some of the fibers sense taste but most of them don’t sense anything but pain. A supertaster would feel way more pain for eating a hot pepper than a nontaster because he has way more pain fibers.

 

Chili peppers mixed with honey were used to treat sores in the month because they’re really good analgesics.

 

The pain in the aids man’s foot was deep in his foot. The nerves present in the mouth that signal heat and pain are also present in the foot & are interacted in the same way. The numbed his feet and put capsaicin on it (which is beyond strong). The molecule in our nerves that hot peppers activates that causes the painful burn sits like a tramp door on the surface of the pain fiber. Capsaicin unlocks the door, allowing Ca+ ions to rush in, firing off the pain message to the brain. The same reaction comes with hot water. The function of the trap doors may have originally been to signal heat and that we have to be careful. Hot peppers fool our cells into thinking they’re on fire and thus have the same effect.

 

 

MUSCULAR SYSTEM

 

Neuromuscular junction:

To activate skeletal muscle, the CSN initiates an action potential that travels down the spinal cord to the motor neurons. As the nerve fiber branches, the action potential travels down each branch. Each nerve fiber branches many times & stimulates several skeletal muscle fibers. The union of the axon and muscle fibers called the neuromuscular junction. On the microscopic level, each branch of the neuron has a terminal that invaginates the muscle fiber, while remaining outside the vaginate muscle fiber membrane. The action potential arrives at the axon terminal. In the terminal, the AP causes the release of acetylcholine from the synaptic vesicles in the space between the axon terminal and the muscle fiber, called the synaptic cleft. In the synaptic cleft, the acetylcholine binds with the receptor site on the fiber membrane, which opens a chemically gated ion channel. Sodium the rushes through the ion channel into the muscle fiber, causing an AP to form on the fiber membrane. The AP spreads along the muscle fiber. As more nerve branches activate additional fibers, the aP spreads over the entire muscle. Upon activation, the muscle contracts.

 

Mirror neurons:

Neurons that fire every time we watch OR imitate an action. Autistic children are thought to have deficits in the mirror neurons. They don’t show the same brain activity as normal people.

 

Movement disorders:

Both Huntington’s and Parkinson’s affect the basal ganglia. Biggest difference is that Huntington’s is a genetic disease & Parkinson’s can have genetic factors but is not 100% genetic.

 

Parkinson's occurs as result of a loss of nerve cells in the part of the brain known as the substantia nigra. These cells are responsible for producing a chemical known as dopamine, which allows messages to be sent to the parts of the brain that co-ordinate movement. With the depletion of dopamine-producing cells, these parts of the brain are unable to function normally. 

 

 

TEMPERATURE REGULATION, THIRST AND HUNGER

 

Body temperature regulation:

Body’s normal temperature is between 35-37 and rises after eating or exercise. It’s the lowest in the morning & highest in late evening. Temperature homeostasis (regulation) within the body is the balance between heat input & heat output. Heat input can come from 2 ways: internally (metabolism + muscle contraction) & externally (conduction (hot object touching your body) + radiation).

Heat output comes in 4 ways: conduction (cold object touching you = body emits heat out), convective process (hot air rising from ground = body emits heat), radiation (heat being emitted and absorbed) & evaporation (water evaporates from body & brings heat with it).

 

Thermoneutral zone = 27-30 degrees outside, as hot as body temperature. Humans are naturally tropical animals and we actually have a harder time psychologically adapting to cold weather.

 

The thermoregulatory center is situated in the hypothalamus in the brain & it tries to keep internal temperature balance. There’s also thermo receptors (central receptors) in the hypothalamus that notice changes inside the body & there’s thermo receptors in the skin (peripheral receptors) that notice changes on the outside of the body.

 

If the peripheral thermal receptors sense changes in temperature it will send these signals to the thermoregulatory center in the hypothalamus. This information will then get processed & an appropriate response will be sent to the body to keep the internal temperature stable, an autonomic response. If it’s responding to cold weather, the body will try to retain heat by shivering or using brown fat that can cause heat production. If it’s responding to hot weather, it will need to lose heat. It will do this by dilating the blood vessels (vasodilation) which increases heat loss, or by sweating.  

 

Thirst motivation/osmoregulation:

Hypotonic: low concentration of salt & high on water --> hypertonic: high concentration of salt in osmosis. Water always flows to a hypertonic. When the cells shrink it sends a signal to the body to drink.

The part of the hypothalamus that detects thirst & shit is called the Lateral preoptic area. Blood flows right past it & it detects the concentration of the fluid in the blood. They’re going to send a signal to the Posterior pituitary gland to secrete antidiuretic hormone (ADH): vasopressin, that will tell the kidneys to bring water back in because you have a lot of salt in your body. Vasopressin tells the brain to make you drink. Kidney releases Renin that causes the release of Angiotensin which tells the kidney to not release water into the bladder but to bring it back in the blood. Angiotensin also goes to the brain to signal thirst. A lot of angiotensin will cause thirst.