Homeostasis and Response Flashcards
What is homeostasis?
The regulation of the internal conditions of a cell or organism in response to internal and external changes.
What does homeostasis control?
Blood glucose concentration.
Body temperature.
Water and Ion levels.
Nervous and chemical (hormonal) responses.
What do control systems include?
Receptors (detect stimuli).
Coordination centres.
Effectors (responders).
What are examples of coordination centres?
Brain, spinal cord, pancreas.
What are examples of effectors?
Muscles, glands.
What is negative feedback?
A control mechanism where upon a receptor detecting a change in stimulus, the coordinating centre compares the stimulus to a set point, then causes the effector to produce a response to correct any difference from the set point.
Basically, maintains amounts of things in the body. Like blood sugar.
What is the central nervous system (CNS)?
The brain and spinal cord.
What is the purpose of the CNS?
Coordinates the response of effectors.
Describe a reflex arc.
Receptors detect stimuli. Sensory neurone carries impulse to CNS. Impulse passes through relay neurone. Motor neurone carries impulse to receptor. Effector responds.
In what order, in the reflex arc, do neurones appear?
Sensory, relay, motor.
How do neurones communicate?
Synapses.
How do electrical impulses travel?
Through the neurones: once it reaches the synapse, a chemical is released which diffuses across the gap between the two neurones, which causes the electrical impulse to be generated in the second neurone.
What is the endocrine system?
Made up of glands which secrete hormones directly into the blood.
What are hormones?
Chemical messengers, carried in the blood, which target an organ where they produce an effect.
What is the pituitary gland?
The ‘master gland’ which secrete hormones in response to body conditions.
List some glands.
Pituitary gland. Thyroid gland. Adrenal gland. Testis. Ovaries. Pancreas.
What does adrenaline do?
Increases heart rate, so more oxygen and glucose can be supplied to the brain or muscles.
What does thyroxine do?
Increases the metabolic rate.
What does the pancreas do in the endocrine system?
Monitor and control blood glucose concentration.
What does insulin do?
Causes glucose to move from the blood into the cells.
What happens if blood glucose concentration is too low?
The pancreas produces glucagon, which stimulates glycogen to be converted into glucose and released back into the blood.
What is type 1 diabetes caused by?
The pancreas fails to produce sufficient insulin.
What is type 2 diabetes caused by?
The body no longer responds to insulin (usually as a result of an unhealthy diet).
What are the four hormones involved in controlling the menstrual cycle?
Follicle stimulating hormone (FSH).
Oestrogen.
Luteinising hormone (LH).
Progesterone.
Where are follicle stimulating hormones produced?
Pituitary gland.
Where is oestrogen produced?
Ovaries.
Where are luteinising hormones produced?
Pituitary gland.
Where is progesterone produced?
Empty follicles in the ovaries.
What is the function of FSH in the menstrual cycle?
Causes eggs to mature in the ovaries in the first half of the cycle and stimulates ovaries to produce oestrogen.
What is the function of oestrogen in the menstrual cycle?
Inhibits FSH release and stimulate LH release. It also makes the lining of the uterus grow again after menstruation.
What does FSH stand for?
Follicle stimulating hormone.
What does LH stand for?
Luteinising hormone.
What is the function of LH in the menstrual cycle?
Stimulates ovulation (the release of an egg from the ovaries).
What is the function of progesterone in the menstrual cycle?
Maintains lining of the uterus in the second half of cycle and inhibits FSH and LH release.
Describe vitro fertilisation (IVF).
A women is given FSH and LH to stimulate the growth of many eggs.
The eggs are collected from the woman.
The eggs are fertilised with sperm in a laboratory.
A few embryos are inserted into the woman’s uterus.
What hormones are in a fertility drug?
FSH and LH.
What are some disadvantages to fertility treatment?
It can be emotionally and physically stressful.
The success rates aren’t high.
It can lead to multiple births, which puts both the mother and the foetuses at risk.
