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Summary Paper 2 Life Sciences Definitions
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Includes definitions for terms used in the paper 2 life sciences syllabus
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Life Sciences Paper 2 DefinitionsEndocrine System:
Chemical coordination: a slow prolonged process of communication through the
body using hormones
Hormone: an organic chemical substance, that is usually a protein, that is secreted
by an endocrine gland and is carried in the blood to its target organ to regulate
metabolic reactions. It is broken down by enzymes once it has completed its
message, hence, hormones are not long lasting.
Target organ: cells that respond to a hormone, as they have receptor sites for that
specific hormone.
Endocrine gland: vascular (rich blood supply), ductless gland that secretes
hormones.
Exocrine gland: secretions are carried by a gland to the target organ, where they are
needed.
Osmoregulation: a system that ensures that the level of water within the body is
kept constant, at a homeostatic level.
Osmoreceptors: receptors in the blood vessel of the hypothalamus that are
responsible for osmoregulation.
Hypersecretion: over secretion (too much is secreted by the gland)
Hyposecretion: under secretion (too little is secreted by the gland)
Secreted: to be released
Basal metabolic rate: amount of energy the human body needs to keep functioning
at rest
Homeostasis: in order for cells to function properly there must be an optimal
internal environment that must be maintained, this is done by a negative feedback
loop. If homeostasis is not maintained, it can result in illness or death.
Negative feedback mechanism: exists to detect and restore changes or imbalances
in the internal environment of the human body. Mechanism that ensures that, in any
control system, changes are reversed, and returns back to the set level. A process
whereby the response by the effector is opposite to and reverses the stimulus.
o A receptor detects a change from a set point and sends a message to the
control center.
o Control center processes the information and sends a message to the
corrective mechanisms that go to the effector.
o Effector responds and the change is corrected.
Thyroid gland: two lobes of a butterfly-shaped gland on either side of the tracheas
below the larynx in front of the neck, that secretes thyroxin.
Thyroxin: a hormone that regulates the metabolic rate, as well as regulating the
heart and nervous system.
Hypothyroidism: low metabolic rate due to lower activity of the thyroid gland
Myxoedema: a disease caused by hypothyroidism in adults. Manifests in symptoms
such as mental and physical sluggishness, low blood pressure, slow heart and
respiratory rate and low body temperature.
Cretinism: a disease caused by hypothyroidism in children. Manifests in symptoms
such as mental retardation, lack of growth and immature sexual development.
, Hyperthyroidism: high metabolic rate due to high activity of the thyroid gland.
Manifests in symptoms such as high body temperature, increased sweating, heart,
respiratory and blood pressure increases, muscular tremors and nervousness as well
as a swollen thyroid gland (goiter).
Thyroid stimulating gland (TSH): a hormone that stimulates the thyroid gland to
secrete thyroxin (pituitary gland hormone).
Luteinizing hormone (LH): stimulates ovulation (the release of the ovum) in the
ovary and the formation of the corpus luteum (the structure that develops in the
ovary after the ovum has been released and releases progesterone and disintegrates
unless pregnancy has begun) (pituitary gland hormone).
Follicle stimulating hormone (FSH): stimulates oogenesis (formation of the ova) in
the ovaries – females. Stimulates spermatogenesis (formation of sperm) in the testes
– males. (pituitary gland hormone)
Prolactin: stimulates the production of milk in the mammary gland after birth and is
responsible for motherly instincts (pituitary gland hormone).
Growth hormone (GH): promotes muscular and skeletal growth by stimulating
protein synthesis (pituitary gland hormone).
Interstitial cell stimulating hormone (ICSH): stimulates the testes to secrete
testosterone (pituitary gland hormone).
GABI:
o Alpha cells (in the Islets of Langerhans): secretes glucagon (used to raise
blood sugar levels).
o Beta cells (in the Islets of Langerhans): secretes insulin (used to lower blood
sugar levels).
Oxytocin: stimulates the release of milk after childbirth (hypothalamus hormone).
Anti-diuretic hormone: responsible for the process of osmoregulation within the
body (hypothalamus hormone).
Human reproduction:
Scrotum: tissue that contains and protects the testis. Also acts as a temperature
regulator, keeping the testis below body temperature (this is necessary for the
formation of fertile sperm).
Testis: two oval structures that are suspended outside the body by the scrotum, that
are responsible for the production of sperm and testosterone.
Prostate gland: gland located at the base of the bladder that secretes fluid that aids
in the transport of sperm and contains enzymes to make sperm more active.
Penis: consists of 3 sections of erectile tissue, two dorsal and one ventral. Blood fills
this erectile tissue, resulting in an erection which then allows the male to deposit the
semen into the female’s vagina during copulation.
Epididymis: seminiferous tubules that the sperm are sent to, to mature and are
stored in.
Vas Deferens (sperm duct): continuation of the epididymis, leaves the scrotum,
passes through the prostate gland and enters the urethra. Pushes mature sperm
forward using peristaltic waves known as ejaculation.
Urethra: duct at the end of the uro-genital system leading to the outside of the
body. Form the common duct for transportation and sperm and urine.
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