Topic 15 (Hormones) Flashcards
(31 cards)
What are hormones?
A chemical substance produced by a gland, transported in the blood (plasma), and alters the activity of one or more
specific target organs.
Where are hormones produced?
Hormones are produced by ductless glands or endocrine glands, and are secreted directly into the bloodstream.
What are some main endocrine glands and hormones in the body?
*Pituitary gland
*Ovaries (in women)
*Testes (in men)
*Hypothalamus
*Adrenal gland (medulla)
*Kidney
*Pancreas
What are the effects of adrenaline?
*It increases the rate of breathing.
*It increases the rate of heartbeat.
*It causes the pupil of the eye to dilate.
*It increases the rate of blood clotting.
*It causes the arterioles to the skin and intestines to constrict.
*It increases the metabolic rate (i.e. the rate
of aerobic respiration) in the muscles.
*It stimulates the liver and muscles to
convert glycogen to glucose.
What is the importance of adrenaline?
*More oxygen can be taken into the body for aerobic
respiration.
*Oxygen and glucose can be transported more quickly to
the muscles.
*Vision is enhanced to help the person see the danger
more clearly.
*If the skin is cut, the blood will clot faster to prevent
excessive loss of blood.
*The person looks pale and digestive activity
decreases, but more blood is sent to the muscles.
*More energy will be released in the muscles.
*More glucose will be available for muscle contraction.
What are the effects of insulin and glucagon?
*Insulin decreases blood glucose concentration.
*Glucagon increases blood glucose concentration.
What are the differences between the endocrine and nervous controls?
ENDOCRINE CONTROL:-
Involves hormones (chemical
substances).
Hormones are transported by the blood.
Usually slow.
May be short-lived (e.g. adrenaline) or
long-lived (e.g. growth hormone).
Always involuntary.
May affect more than one target organ.
NERVOUS CONTROL:-
Involves nerve impulses
Impulses are transmitted by neurons.
Usually quick.
May be short-lived (e.g. adrenaline) or long-lived (e.g. growth hormone).
Short-lived.
Always involuntary.
Usually localized.
What is homeostasis?
*Homeostasis is the maintenance of a constant internal environment.
*The internal environment refers to conditions within the body of the organism. The external environment is
the environment in which an organism lives.
Why does the body temperature have to be kept constant?
Enzymes in the body can only work within a certain range of temperatures.
Why must tissue fluid be kept at a constant pH and water potential?
*A drastic change in the pH of tissue fluid will affect enzyme reactions in cells.
*Drastic changes in the water potential will also affect the cells.
Why does the blood glucose concentration have to be kept constant?
Glucose is needed for cellular respiration, thus a drastic change in glucose concentration can affect cellular activity.
How is the blood glucose concentration regulated when it is above normal levels?
1) Stimulus - blood concentration rises above normal.
2) Receptors (also the control center) - Receptors in the pancreas are stimulated.
3) The Islets of Langerhans secrete insulin into the bloodstream.
4) Blood transports insulin to the liver and muscles.
5) Glucose is absorbed more quickly by the cells.
6) Insulin causes the liver and muscles to convert excess glucose to glycogen. Glycogen is stored in the liver and muscles.
7) Blood glucose concentration decreases. This gives a feedback to the receptor to reduce insulin production. And, then blood glucose concentration goes back to normal.
How is the blood glucose concentration regulated when it is below normal levels?
1) Stimulus - blood concentration falls below normal.
2) Receptors (also the control center) - Receptors in the pancreas are stimulated.
3) The Islets of Langerhans secrete glucagon into the bloodstream.
4) Blood transports the glucagon to the liver and muscles.
5) Glucagon causes the conversion of stored glycogen back to glucose.
6) From the liver, glucose enters the bloodstream.
7) Blood glucose concentration increases. This gives a feedback to the receptor to reduce glucagon production. And, then blood glucose concentration goes back to normal.
What happens when the blood lacks insulin?
If there is no insulin in the bloodstream, glucose cannot be stored as glycogen. This gives rise to a condition
known as diabetes mellitus.
*Diabetes mellitus is also called type 1 diabetes
How can type 1 diabetes be treated?
Insulin injections. It is also important to maintain a good diet and to do regular exercise.
What are the structures involved in regulating body temperature?
*Hairs
*Sweat glands
*Sensory receptors (thermoreceptors)
*Subcutaneous fat
*Blood vessels
How does the body lose heat? (more heat loss)
1) The skin arteriole dilates, increasing blood flow to skin.
2) The shunt vessel constricts.
3) More blood flows to the skin surface. This leads to greater heat loss.
How does the body lose heat? (less heat loss)
1) The skin arteriole constricts, decreasing blood flow to skin.
2) The shunt vessel dilates.
3) Less blood flows to the skin surface. This leads to less heat loss.
What is the function of the hypothalamus?
The hypothalamus in the brain monitors and regulates the body temperature.
What happens when the body temperature begins to rise?
1) Body temperature rises above normal.
2) Thermoreceptors in the skin and the hypothalamus are stimulated.
3) The arterioles of the skin dilate and the shunt vessels constrict. This dilation of the arterioles is called vasodilation. It allows more blood to flow through blood capillaries in the skin. More heat will be lost through the skin by radiation, convection and conduction.
4) Sweat glands become more active. More sweat is produced. As more water in the sweat evaporates from the skin surface, more latent heat of vaporization is lost from the body. This is an efficient mean of losing heat.
5) The metabolic rate is decreased. This reduces the amount of heat released within the body.
6) Body temperature decreases.
What happens when the body temperature begins to fall?
1) Body temperature falls below normal.
2) Thermoreceptors in the skin and the hypothalamus are stimulated.
3) The arterioles of the skin constrict and the shunt vessels dilate. This constriction of the arterioles is called vasoconstriction. It allows less blood to flow through blood capillaries in the skin. This reduces the heat lost by radiation, convection and conduction.
4) Sweat glands become less active. Less sweat is produced. As less water in the sweat evaporates from the skin surface, less latent heat of vaporization is lost from the body.
5) The metabolic rate is increased. This increases the amount of heat released within the body.
6) When the above responses are not sufficient to prevent a drop in body temperature, shivering occurs. This is a spasmodic contraction of the skeletal muscles. It increases the amount of heat released.
7) Body temperature increases.
What is tropism?
The growth and movement of plants are affected by external stimuli such as light, gravity, water and chemical
substances, as well as foreign body.
This growth movement is called a tropic movement or tropism.
What is phototropism?
Phototropism is a response which a plant part grows towards or away from a unidirectional light source.
What is gravitropism?
Gravitropism is a response in which a plant part grows towards or away from gravity.
