Biology Reflex Actions and the Human Eye

Study Notes

A reflex action is a quick, automatic response to a stimulus
The functional connection at D is a synapse
Neuron B is an interneuron
The synapse ensures that the impulse moves in one direction only, from the sensory neuron to the motor neuron
The order of neurons involved in a reflex action is A → B → C
If neuron C is damaged, the person will be able to receive a stimulus but will not be able to respond to it
Neuron A is a sensory neuron, with a cell body located in a ganglion
Neuron A has a dendrite and an axon
Neuron A's axon is myelinated
Neuron A's axon ends in a synaptic knob

The lens is labeled as B
The choroid is labeled as C
Long-sightedness is a condition where people cannot see nearby objects clearly due to the image being blurred
If the lens is removed, no image will be formed, because light will not be converted into an impulse, as there are no receptors present.
The lens is elastic, transparent, and biconcave
The lens is elastic, which allows it to change shape (convexity) for accommodation
The lens is transparent to allow light rays through
The lens is biconcave to refract (bend) light rays

The pinna (auricle) is labeled as A
The malleus or hammer is labeled as B
The stapes or stirrup is labeled as C
The oval window is labeled as D
If part E is blocked, air will not be taken in or released to equalize pressure on both sides of the tympanic membrane. This stops the tympanic membrane and ossicles from vibrating freely, potentially leading to the tympanic membrane bursting and hearing loss, deafness, or pain.
The middle ear amplifies sounds by concentrating vibrations from the large tympanic membrane to the smaller oval window, through the ossicles arranged from largest to smallest.
Fusion of the ossicles may lead to hearing loss because the bones will not be able to vibrate to pass vibrations to the inner ear (cochlea) and no amplification will occur
Part C is the cochlea
Part D is the semicircular canals
The receptors located in part B are hair cells

Organ 1 is the pancreas
Hormone 2 is insulin
Hormone 3 is glucagon
Diabetes mellitus is a disorder caused by an imbalance in the levels of blood sugar
When blood sugar levels are too low, the pancreas secretes glucagon, which stimulates the liver and muscles to convert glycogen into glucose, increasing blood sugar levels and returning them to normal
When blood sugar levels are too high, the pancreas secretes insulin, which stimulates the liver and muscles to convert glucose into glycogen, decreasing blood sugar levels and returning them to normal
Hormone X is ADH (Antidiuretic Hormone)
The endocrine gland that secretes ADH is the pituitary gland
The target organ for ADH is the kidneys
When a person is dehydrated, the brain detects the decrease in blood volume, stimulating the pituitary gland to secrete ADH.
ADH increases the permeability of the renal tubules, leading to more water being reabsorbed back into the blood, ultimately returning the water level to normal.