Midterm 3 Flashcards
List the 3 general ways that a hormone can regulate the activity of its target cells.
- by activating an enzyme
- by activating a receptor that opens a channel
- by acting as a transcription factor…turns on gene
Describe the location of the receptors for lipid soluble hormones and water soluble hormones. Describe how these locations affect the way that a hormone (generally) regulates the activity of its target.
Water soluble hormone - Receptor always located outside the cell on the cell membrane. It activates enzymes and opens channels. (peptide/proteins - series of amino acids folded and epi/norepi)
Lipid soluble hormone - Receptor always located inside the cell (intracellular receptor) It activates transcription factors - turns on gene. (Steroid hormones and T3, T4 which act like steroid)
How are hormones once released into the blood removed from the blood?
- Enzymes in liver destroy them
2. You pee them out
List the three classes of hormones. For each class of hormone describe its chemical structure and give some examples of specific hormones.
- Peptide/ proteins - series of amino acids folded (insulin, parathyroid hormone)
- Steroid hormones - all made form cholesterol; lipid soluble (estrogen, androgens, cortisol)
- Amino Acid based - catecholamines and thyroid hormones (Catecholamines: epinephrine, norepinephrine, dopamine; Thyroid hormone: thyroxine T4 and T3)
When steroid hormones bind to their receptors:
A) adenylate cyclase is activated, B) ion channels are opened or closed, C) G proteins are inhibited, D) gene transcription may increase or decrease
D. gene transcription…..
Define the term trophic hormone. Explain how this term is used in physiology. List the major tropic hormones.
Trophic hormones - hormones that control the secretion of other hormones.
They cause secretion in endocrine glands
Major trophic hormones: ACTH, TSH, FSH, LH, GH
The primary target (organ/cells) of glucagon is what?
Liver
The precise name of the cells that secrete glucagon is what? Where are they found?
alpha cells in the islet of Langerhans in the pancreas
The primary stimulus for glucagon secretion is what? Further describe the stimulus by listing a quantitate value.
Sympathetic NS (Low blood glucose levels)
normal: 100mg/dL
too high: 200mg/dL
too low: 50mg/dL
Describe each of the effects glucagon has on the target (include the substrate and product where appropriate). For each substrate list its primary source in the body.
Liver:
glycogenolysis (glycogen -> glucose)
gluconeogenesis (glycerol, some AA, pyruvate -> glucose)
Adipose tissue:
ketogenesis (fatty acids -> acetyl CoA -> ketone bodies)
How are the effects of glucagon critical for maintaining homeostasis?
Glycogenolysis takes stored forms of glucose and converts it back to glucose and gluconeogenesis takes other forms of energy and converts it to glucose in order to increase blood glucose levels back to their set point. Ketogenesis provides another source of energy to the CNS when it is low.
The primary targets (organ/cells) of insulin are what?
skeletal muscle, adipocytes, liver
The primary stimulus for insulin secretion is what? Further describe the stimulus by listing a quantitate value.
Parasympathetic NS (High blood glucose levels)
normal: 100mg/dL
too high: 200mg/dL
too low: 50mg/dL
The precise name of the cells that secrete insulin is what? They are found where?
beta cells in the Islet of Langerhans in the pancreas
Describe each effect insulin has on its targets (include the substrate and product where appropriate). For each substrate list its primary source in the body.
Skeletal muscle:
Increases glycolysis (glucose -> pyruvate)
Adipocytes:
Increase lipogenesis (glucose -> triglycerides)
Liver:
Increase glycogenesis (glucose -> glycogen)
How are the effects of insulin critical for maintaining homeostasis?
In order to decrease blood glucose levels back to wards their setpoint glucose is stored or converted into other forms throughout the body.
The force generated in a skeletal muscle cell is directly proportional to the number of what?
crossbridges formed
In order for cross-bridge to form in a contracting skeletal muscle cell, calcium must…
bind to troponin which moves the tropomyosin
A myosin head is able to bind to what?
Actin and ATP
Describe the functions of sarcoplasmic reticulum. For each function name the protein responsible for the function and describe what it does and how it does what it does (mechanism)
Stores and releases Ca+2
Pumps in Ca+2 through the Ca+2 pump (1 ATP pumps 1 Ca+2)
Releases Ca+2 through the Ca+2 release channel which is physically/chemically connected to a voltage-sensitive Ca+2 channel that opens when brought to threshold by an AP.
The neurotransmitter released at a neuromuscular junction is what? Is it excitatory or inhibitory?
ACh (Acetylcholine)
Always excitatory
The relaxation of skeletal muscle relies on the activity of the what? which decreases cytoplasmic calcium concentration.
Ca2+ ATPase (calcium pump)
Define “latent period.” Why does it exist? What is happening during the latent period?
The delay between the muscle action potential and the beginning of muscle tension development.
It is the time required for calcium release and binding to troponin.
