week 4 Content. Hormones and Endocrine System Flashcards
What are the 2 types of communication systems, provide a general brief description of each
Nervous system: rapid communication, mediated by neurotransmitters
Endocrine system: lower communication, mediated by hormones that travel via blood between receptors
what is the overall role of the endocrine system (4)
- maintain homeostasis
- maintain metabolism
- reproduction
- development
How do hormones travel within the body and what cells can/do they bind to?
- travel via circulatory system(blood capillaries)
- hormone cells only bind to target cells carrying specific receptors to the hormone (distant target cells)
- induce change in the cell receptor to respond to the message
what are the main endocrine organs (10)
- hypothalamus
- pituitary gland (anterior and posterior)
- thyroid
- parathyroid
- thymus
- adrenal cortex (adrenal gland)
- adrenal medulla (adrenal gland)
- pancreas
- ovaries
- testes
what are the 3 types of hormone groups, explain their structure and movement in/out of cell
Lipid derivatives:
- derive from fatty acids
- hydrophobic - directly diffuse across cell membrane to bind with receptors in inside
Peptide:
- made of many amino acids
- hydrophilic- binds to receptors on the outside of the cell
Amino acids:
- modified amino acids
- hydrophilic- binds to receptors on the outside of the cell
what is a hormones interaction with target cells (distant target cells - receptor containing), and where are receptors found
- hormones are only effective once bound to the target cell
- target cells have specific receptors for certain hormones
- receptors are found on the external surface of cell, or inside the cell, specifically in the cytoplasm and nucleus
- a target cell can have more than one receptor, hormones can influence receptors present
Explain Lipid-insoluble/ water soluble hormones and how they initiate change to target receptor cells
- cannot travel across cell membrane
- target cells contain G-receptors on cells surface where hormones bind to
- hormone = 1st messenger
- initiates a chain of communication inside cell via 2nd messengers (cAMP)
- cAMP interacts with protein kinase A (PKA) - causes release of a catalytic subunit
- catalytic subunit binds to a specific target protein in cell- causing it to become phosphorylated
- phosphorylated proteins alter their activity, resulting in multiple physiological responses inside cell
- specific enzyme inactivate 2nd messenger to cease cellular response
- requires another 1st messenger to restart process
Explain Lipid-soluble hormones and how they initiate change to target receptor cells
- require transport proteins to move around body
- a small amount of the hormone is released from transport protein
- hormone can diffuse into cell cytoplasm
- hormone binds to receptors in cytoplasm or nucleus to initiate cellular response
- in nucleus, receptor complex (receptor and hormone) interact with regions of DNA to activate transcription of genes - leading to change in cell function
- regulates gene expression and mRNA
how do hormones effect a cell (5)
- synthesis of molecules
- alter cell membrane permeability
- influence transport of substances in and out of cell
- effect cells metabolic rate (produce new enzymes)
- cause contraction of smooth and cardiac muscle
what controls hormone secretion
- negative feedback loops maintain hormone levels and overall homeostasis
What are the major systems that regulate the secretion of hormones, briefly describe them
Humoral control:
- release of a hormone in response to stimuli (eg changes in extracellular fluid or ion levels)
Hormonal control:
- release of a hormone in response to another hormone released by another endocrine gland
Neural control:
- release of hormones in response to neural stimulation
Neural control
- hypothalamus sends messages along neurons connecting to the adrenal medulla
- activated neurons rapidly release chemical messages in response to neural stimulation
- hormones released in adrenal medulla are:
~ epinephrine (adrenalin)
~ norepinephrine (noradrenalin)
Humoral control
- endocrine cells respond to certain ions in blood or interstitial fluid
- works along a concentration gradient
- e.g glucose molecules in blood are managed by beta and alpha cells in the pancreas by secreting insulin or glucagon (depending on glucose levels)
- high glucose levels are detected by beta cells in the pancreas
- initiates the production of insulin
- insulin is released into the circulatory system and stimulates cells to increase intake of glucose
- glucose levels in blood fall within range and beta cells reduce insulin secretion
Hormonal control and an example
- endocrine glands respond to hormones from other endocrine glands by releasing more hormones
- hypothalamus secretes thyrotrophin-releasing hormone and releases it into the APG
- APG responds by releasing TSH into the circulatory system
- TSH is transported to target cells in thyroid
- thyroid responds by releasing thyroid hormones T3 and T4
- the negative feedback loop detects high levels of thyroid hormones which inhibits production of the TRH in the hypothalamus
how does a negative feedback loop work
- target cell receptors/ enzymes inactivate 2nd messengers, inhibiting the multiple physiological responses in the cell to prevent overproduction of hormones etc
- requires more hormones from other endocrine glands to initiate another response (1st messengers)
explain what happens during high and low blood glucose levels
HIGH:
- beta cells in pancreas detect high levels of glucose
- initiate production of insulin
- insulin released into blood signals for cells to uptake glucose
- blood glucose returns to homeostasis
- beta cells cease production and release of insulin
LOW:
- alpha cells in pancreas detect low blood glucose
- initiates secretion of glucagon into blood
- target cells in liver and skeletal muscle absorb and break down glycogen into glucose
- Glucose is released into blood stream, returning levels to homeostasis
- alpha cells cease production and secretion of glycogen
what is an example of a lipid-insoluble hormone? Where is it produced?
- Oxytocin
- produced in posterior pituitary gland
