Stuff i found i need to memorise Flashcards
middle ear infection
Middle ear infection usually occurs after a viral infection of the upper respiratory tract, such as a cold or flu, when the tissue at the back of the nose and throat is inflamed and swollen. Consequently, the Eustachian tube cannot function properly. Air cannot be replaced in the middle ear, resulting in the air pressure in the middle ear being lower than the atmospheric pressure in the external auditory canal. A negative pressure builds up in the middle ear cavity which leads to fluid being extracted from the surrounding tissue and accumulating in the cavity. This makes the tympanic membrane bulge, causing pain. In severe cases, if not treated e.g. with an antibiotic or grommets the eardrum may burst as pressure builds up.
Explain the consequence if tight fitting underwear on human reproduction
Fertility is reduced because the temperature will always be high this will lead to the production of abnormal sperm
Menstrual Cycle
The menstrual cycle is a series of events that occur in the female body to prepare it for possible pregnancy.
The pituitary gland/hypophysis secretes FSH which stimulates the development of a primary follicle into a Graafian follicle in the ovary
The Graafian follicle secretes oestrogen which stimulates the thickening of the lining of the uterus/endometrium
Around day 13 pituitary gland/hypophysis secretes LH which cause ovulation to occur
The remains of the Graafian follicle develop into the corpus luteum which secretes the hormone, progesterone which continues to stimulate the thickening of the uterus
High levels of progesterone inhibit the production of FSH so that the ovaries are no longer stimulated to produce another follicle (negative feedback mechanism).
If fertilisation does not occur, the corpus luteum degenerates and stops producing progesterone
The pituitary gland/hypophysis is no longer inhibited in its production of FSH and a new follicle develops
The thick endometrium is no longer maintained and it degenerates and is shed together with blood and menstruation takes place
Fertilisation
Sperm surround the secondary oocyte and attach to it
The acrosome releases lytic enzymes to digest the outer follicle cells (corona radiata) surrounding it
The head of one sperm penetrates the egg membrane (the midsection and tail is discarded)
The egg membrane becomes impenetrable to other sperm
The secondary oocyte undergoes meiosis 2 forming an ovum (n) and polar body (n)
The haploid sperm nucleus (n) fuses with the haploid ovum nucleus (n) forming a new diploid nucleus (2n)
Implantation
The blastocyst enters the uterus and after 2-5 days implants into the endometrium. The trophoblast cells secrete enzymes to break down the epithelium of the endometrium. The blastocyst embeds in what is by now a very thick and vascular (due to oestrogen and progesterone) endometrium. The trophoblast develops finger like villi that grow into the endometrium eventually forming the placenta. The placenta secretes progesterone that maintains the endometrium, preventing menstruation.
THE PLACENTA functions
Provide nutrition of the embryo, excretion and gaseous exchange.
A micro-filter preventing pathogen entry, and allowing antigens resulting in passive immunity for the baby.
Endocrine gland: after 12 weeks it secretes oestrogen and progesterone to maintain pregnancy.
AMNION
A tough membrane lining the chorion
This encloses the amniotic cavity, filled with amniotic fluid
This fluid contains water, discarded foetal cells, waste products and microbes
It allows the fetus to move around, prevents shocks, dehydration and reduces temperature change
Significance of a synapse:
It ensures that the impulse moves in only one direction.
It prevents continuous stimulation of the neurons.
It ensures that the impulse is transmitted from the sensory neuron to the motor neuron.
The reflex action of a person touching a sharp pin:
- The stimulus is detected by receptors and converted into a nerve impulse.
- The nerve impulse is transmitted along the sensory neuron through the dorsal root to the spinal cord.
- The impulse is transmitted from the sensory neuron to an interneuron in the spinal cord.
- The impulse is transmitted from the interneuron to a motor neuron in the spinal cord.
- The impulse exits the spinal cord through the ventral root and is transmitted along the axon of the motor neuron to the effector organs (muscle; this causes the muscles in the limb to contract).
- The hand pulls away from the stimulus quickly.
This reflex action does not include the brain. Impulses will reach the brain after the reflex arc is complete and pain will be felt.
How biconcave lenses correct myopia
- Biconcave lenses will help to diverge the light before they enter the eye
- to focus on the retina
