G12 C6 Endocrine system Short Question answers

Chapter 6 Endocrine System

Short Answer Questions

Why are hormones called chemical messengers?

Hormones are called chemical messengers because they are small, soluble organic molecules that transport a signal from one cell to another. They travel through the bloodstream to affect specific target cells with unique receptors.

What are neurosecretory cells?

Neurosecretory cells are special cells in the hypothalamus that produce and release hormones. These hormones include releasing factors that stimulate the pituitary gland and inhibiting factors that prevent it from releasing certain hormones.

Name the hormones of the anterior pituitary gland.

The hormones of the anterior pituitary gland include: growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), follicle-stimulating hormone (FSH), luteinising hormone (LH), and prolactin.

Why is the anterior lobe of the pituitary gland called the "master gland?"

The anterior lobe is called the "master gland" because it secretes numerous hormones that regulate and control the function of other major endocrine glands throughout the body.

Describe the median lobe of the pituitary gland.

The median lobe is a thin layer of cells located between the anterior and posterior pituitary. It produces melanocyte-stimulating hormone (MSH), which stimulates melanocyte production and melanin release in the skin.

How is the secretion of ADH controlled?

The secretion of ADH (Antidiuretic Hormone) is primarily controlled by the hypothalamus. It is released in response to dehydration, decreased blood volume, and low blood pressure.

Write the differences between:

• a. exocrine and endocrine glands
  Exocrine glands secrete substances into ducts that lead to the outside of the body or into a cavity, like sweat glands. Endocrine glands are ductless and secrete hormones directly into the bloodstream.
• b. steroid hormones and proteinaceous hormones
  Steroid hormones are made of lipids (steroids), such as testosterone. Proteinaceous hormones are made of amino acids and are soluble in water, such as insulin.
• e. hypothyroidism and hyperthyroidism
  Hypothyroidism is a condition of under-secretion of thyroid hormones (T₃/T₄), leading to a low metabolic rate. Hyperthyroidism is caused by over-secretion, resulting in an increased metabolic rate.
• f. calcitonin and parathormone
  Calcitonin decreases blood calcium levels by promoting its deposition into bones. Parathormone increases blood calcium levels by stimulating its release from bones, working antagonistically.
• g. beta and alpha cells of Islets of Langerhans
  Beta cells secrete insulin to lower blood glucose levels when they are too high. Alpha cells secrete glucagon to raise blood glucose levels when they are too low.
• h. insulin and glucagon
  Insulin is a hormone released by beta cells that lowers blood glucose. Glucagon is a hormone released by alpha cells that raises blood glucose, with their functions being antagonistic to each other.
• i. diabetes insipidus and diabetes mellitus
  Diabetes insipidus is caused by the under-secretion of ADH, leading to excessive urine production. Diabetes mellitus is a metabolic disease caused by insufficient insulin, resulting in high blood glucose levels.
• j. estrogen and progesterone
  Estrogen is responsible for female secondary sex characteristics and uterine wall repair. Progesterone thickens the uterine wall for pregnancy and suppresses ovulation.
• k. positive and negative feedback
  Positive feedback is a loop where the end product speeds up its own production. Negative feedback is a loop where the end product reverses the direction of change to maintain homeostasis.

What is the relationship between a hormone and a target cell?

A hormone has a specific relationship with its target cell, often described by the "lock and key" model. The hormone "key" fits into a unique receptor "lock" on the target cell to deliver a specific message.

Locate the endocrine glands in the human body.

The major endocrine glands include the pituitary gland (below the hypothalamus), thyroid gland (on either side of the trachea), adrenal glands (on top of the kidneys), and gonads (ovaries/testes).

How does a feedback mechanism regulate the activity of the endocrine system?

Feedback mechanisms regulate the endocrine system by either depressing (negative feedback) or enhancing (positive feedback) a process. This allows the body to maintain homeostasis and control hormone secretion based on the needs of the body.

Make a diagram of positive feedback involving the hormone oxytocin.

(1) Baby's head pushes against the cervix.
(2) Nerve impulses are sent to the brain.
(3) Brain stimulates pituitary gland to secrete oxytocin.
(4) Oxytocin travels to the uterus, causing stronger contractions.
(5) Stronger contractions increase pressure on the cervix, stimulating more oxytocin release. This cycle continues until birth.

Predict the effects that insufficient amounts of FSH and LH will have on the menstrual cycle.

Insufficient amounts of FSH and LH will disrupt the menstrual cycle. FSH stimulates follicle development and estrogen production, while LH triggers ovulation and progesterone production. A deficiency would likely lead to a failure of sexual maturation and sterility.

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