9.1

Question 1

What are the forms of signalling?

Answer 1

Autocrine (chemicals affect the same cells that secreted them)
Paracrine (chemicals are secreted onto neighbouring target cells)
Endocrine (chemicals diffuse into the blood stream (hormones) to reach target cells throughout the body (longer distance ))

Question 2

What are chemical signals?

Answer 2

Used both local and long distance communication
Some cells secrete blood borne chemical messengers to carry info to target organs
The speed of communication is slower than the nervous system and usually the duration effect is longer

Question 3

What are endocrine glands?

Answer 3

Glands are ductless and releases hormones into the surrounding fluid

Question 4

What are exocrine glands?

Answer 4

Glands have ducts and substances travel along these surfaces

Question 5

What are the three main types of hormones?

Answer 5

Peptides and proteins
Steroids
Amines

Question 6

Describe peptide and protein hormones

Answer 6

• amino acid chains of various length
• many synthesised as preprohormones modified to prohormone
• stored in secretory vesicles prior to release
• typically have a short life
• lipophobic (fear fat) (transported in blood cannot cross plasma membrane

Question 7

Describe steroid hormones

Answer 7

• All are derived from cholesterol
• synthesised as needed in the smooth ER of gonads, adrenal glands and placenta
• largely bound to carrier proteins in the blood (extends half life)
• Lipophillic- can cross the plasma membrane, receptors are the the cytoplasm or nucleus
• active transcription of target genes, alters protein synthesis

Question 8

Describe amine hormones

Answer 8

Amino acids with modified groups

Question 9

How long do hormones stay
active in the blood and how
quickly do responses occur?

Answer 9

• Onset can range from seconds to hours depending on pathways activated.
• Duration of the response can range from minutes to days
• Clearance is the removal of hormone from plasma (bulk cleared by liver and kidneys with only a small fraction actually removed by target tissue).
• Half-life is the length of time it takes for the hormone concentration to drop by half. This can range from seconds to days.