, The endocrine system
The endocrine system is made up of endocrine glands. An endocrine gland is a group of cells
which are specialised to secrete hormones directly into the bloodstream.
Pituitary gland- produces growth
hormone (controls growth of bones &
muscles), anti-diuretic hormone (increases
reabsorption of water in kidneys) & Pineal gland- produces melatonin
gonadotrophins (control development of (affects reproductive development
ovaries & testes) &daily cycles)
Thyroid gland- produces thyroxine
(controls rate of metabolism & rate Thymus- produces thymosin
that glucose is used up in respiration (promotes production &
& promotes growth) maturation of WBC)
Adrenal gland- produces adrenaline Pancreas- produces insulin (converts
(increases heart & breathing rate & excess glucose into glycogen in the
raises blood sugar level) liver) & glucagon (converts glycogen
back to glucose in the liver)
Ovary- produces oestrogen
Testis- produces testosterone (controls ovulation & secondary
(controls sperm production & sexual characteristics) &
secondary sexual characteristics) progesterone (maintains uterus lining)
, Hormones
Hormones are referred to as chemical messengers since they carry information
from one part of the body to another. They are secreted directly into the blood
when a gland is stimulated & travel in blood plasma. The hormones diffuse out of
the blood & bind to specific receptors, found on the membrane or in the
cytoplasm of cells, known as target cells, in the target organ. Once bound to
their receptors the hormones stimulate the target cells to produce a response.
• Steroid hormone- Lipid-soluble. They Hormonal system Nervous system
pass through the lipid component of the Communication is by Communication is by
cell membrane & bind to steroid chemicals called nerve impulse
hormone receptors to form a hormone- hormones
receptor complex. This complex acts as
Transmission is usually Transmission is very
a transcription factor which in turn relatively slow & by blood rapid & by neurones.
facilitates or inhibits the transcription
of a specific gene. E.g. oestrogen
Hormones travel to all Nerve impulse
• Non-steroid hormone- Hydrophilic so parts of body, but only travel to specific
cannot pass directly through the cell target organs respond parts of the body
membrane. Instead they bind to
Response is slow, Response is localise,
specific receptors on the cell surface widespread & long lasting rapid & short-lived
membrane of the target cell. This
triggers a cascade reaction mediated Effect may be permanent Effect is temporary
& irreversible & reversible
by chemicals called second messengers.
E.g. adrenaline
The endocrine system is made up of endocrine glands. An endocrine gland is a group of cells
which are specialised to secrete hormones directly into the bloodstream.
Pituitary gland- produces growth
hormone (controls growth of bones &
muscles), anti-diuretic hormone (increases
reabsorption of water in kidneys) & Pineal gland- produces melatonin
gonadotrophins (control development of (affects reproductive development
ovaries & testes) &daily cycles)
Thyroid gland- produces thyroxine
(controls rate of metabolism & rate Thymus- produces thymosin
that glucose is used up in respiration (promotes production &
& promotes growth) maturation of WBC)
Adrenal gland- produces adrenaline Pancreas- produces insulin (converts
(increases heart & breathing rate & excess glucose into glycogen in the
raises blood sugar level) liver) & glucagon (converts glycogen
back to glucose in the liver)
Ovary- produces oestrogen
Testis- produces testosterone (controls ovulation & secondary
(controls sperm production & sexual characteristics) &
secondary sexual characteristics) progesterone (maintains uterus lining)
, Hormones
Hormones are referred to as chemical messengers since they carry information
from one part of the body to another. They are secreted directly into the blood
when a gland is stimulated & travel in blood plasma. The hormones diffuse out of
the blood & bind to specific receptors, found on the membrane or in the
cytoplasm of cells, known as target cells, in the target organ. Once bound to
their receptors the hormones stimulate the target cells to produce a response.
• Steroid hormone- Lipid-soluble. They Hormonal system Nervous system
pass through the lipid component of the Communication is by Communication is by
cell membrane & bind to steroid chemicals called nerve impulse
hormone receptors to form a hormone- hormones
receptor complex. This complex acts as
Transmission is usually Transmission is very
a transcription factor which in turn relatively slow & by blood rapid & by neurones.
facilitates or inhibits the transcription
of a specific gene. E.g. oestrogen
Hormones travel to all Nerve impulse
• Non-steroid hormone- Hydrophilic so parts of body, but only travel to specific
cannot pass directly through the cell target organs respond parts of the body
membrane. Instead they bind to
Response is slow, Response is localise,
specific receptors on the cell surface widespread & long lasting rapid & short-lived
membrane of the target cell. This
triggers a cascade reaction mediated Effect may be permanent Effect is temporary
& irreversible & reversible
by chemicals called second messengers.
E.g. adrenaline
