Endocrinology Flashcards
1
Q
Homeostasis
A
- Process of maintaining a constant internal environment despite changes in condition
- Homeostasis isn’t equilibrium
2
Q
Feedback Control
A
- Negative Feedback: Initial Stimulus -> Response -> Stimulus that inhibits initial stimulus from generating response(eg. regulation of cortisol secretion)
- Positive Feedback: Initial Stimulus -> Response -> Stimulus that reinforces response, turned off by outside factors(eg. Oxytocin secretion during birth)
3
Q
Intercellular Communication
A
- Gap Junctions: Form direct connections between adjacent cells. Small ions and molecules move through gap junctions(eg. cardiac)
- Contact Dependent: Require interaction between membrane molecules of two cells. Membrane protein binds to membrane protein(eg. immune system)
- Autocrine: Autocrine acts on same cell that secreted them. Paracrine are secreted by one cell and diffuse to adjacent cells. Molecules move through interstitial fluid
4
Q
Reflexes
A
- Simple reflexes mediated by nervous or endocrine system
- Complex reflexes mediated by both systems and go through several integrating systems
5
Q
Why different control systems?
A
- Specificity: Neural terminates on a single target cell. Endocrine effects most of cell in body
- Nature of signal: Electrical signal passes through neuron, and chemical neurotransmitters carry signal. For endocrine, chemical signals secreted in blood for distribution throughout the body
- Speed: Very rapid for neural. Much slower for endrocrine
- Duration: very short for neural. Endocrine lasts much longer
- Coding for stimulus intensity: Signal identical in strength for neural. Endocrine is correlated with amount of hormone secreted
6
Q
Features of hormones
A
- Can be made by different places in the body
-Chemicals made by cells in specific endocrine gland - Transported in blood to different targets
- Binds to specific receptors
- Alter activity in cells
- Action must be terminated
- Maintain homeostasis
7
Q
Hydrophilic Hormones
A
- Water soluble
- Not lipid soluble(lipophobic), cannot cross plasma membrane
- Synthesized in advance
- Dissolved in blood
- Peptide hormones, protein hormones, catecholamines
8
Q
Hydrophobic Hormones
A
- Not water soluble, does not dissolve in plasma
- Synthesized on demand
- Lipid soluble(lipophilic), readily cross plasma membrane
-Bound to carrier proteins in blood - Steroid and thyroid hormones
9
Q
Three types of hormones
A
- Peptide/protein(eg. insulin)
- Steroid(eg. cortisol)
- Amine(single amino acids)(eg. catecholamines)
10
Q
Peptide Hormones
A
- Linked amino acids
- Made in advance
- Synthesized like secreted proteins
- Stored in vesicles, released by exocytosis upon signal
- Water soluble
- Bind to membrane receptors
- C-peptide cleaved after release(proinsulin example)
11
Q
Steroid Hormones
A
- Synthesized from cholesterol
- Made on demand
- Not stored in vesicles
- Released by simple diffusion
- Water insoluble
- Long half-life
- Diffuse into target cells
- Cytoplasm or nucleus receptors
12
Q
Synthesis of catecholamines
A
- Synthesized in adrenal medulla
- Stored in vesicles prior to release
- Released by exocytsosi
- Lipophobic
- Bind to membrane receptors
13
Q
How do stimuli trigger hormone release
A
- Chane in membrane potential
- Increase free cytosolic Ca++
- Change enzymatic activity
- Alter transcription of genes coding for hormones
- Promote survival of endocrine cell
14
Q
Glucose stimulation of insulin release
A
- Glucose goes into cell(increase blood sugar)
- ATP inhibits K+ channel
- Depolarizes cell
- Opens voltage gated Ca++ channel
- Triggers exocytosis insulin release
15
Q
Anterior Pituitary
A
- Hypothalamic releasing and inhibiting hormones
- Does not create hormones
