{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Logothetis_post - G protein signaling pathway Background A...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
G protein signaling pathway - Background - A muscle cell response Muscle cell response (contract or not) depends on an action potential, which in turn depends on depolarization. - change in membrane potential The plasma membrane of most cells has a resting potential around -70 to -80 mV due mainly to the Na+/K+ ATPase and K+ leak channels: •Na+ high outside. •When Na+ channels open, Na+ flows IN and membrane depolarizes •K+ high inside, •When K+ channels open, K+ flows OUT and membrane hyperpolarizes Resting Potential Action Potential How can an acetylcholine (ACh) signal from a nerve cell lead to a muscle cell response?
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
G protein signaling pathway - Background - Acetylcholine receptors •Two kinds of muscle ACh receptors lead to different responses (MBOC 15-9) 1. ACh stimulates Nicotinic acetylcholine receptors on skeletal muscle to cause skeletal muscle contraction •Nicotinic receptor is a Na+ ion channel receptor •Binding of ACh changes conformation of receptor •opens receptor-gated Na+ channels and causes DEPOLARIZATION of the plasma membrane. •When membrane depolarizes to -40 mV, voltage-gated Na+ channels open allowing for rapid influx of Na+ and formation of the action potential and a contraction. 2. ACh stimulates Muscarinic acetylcholine receptors in the cardiac sinoatrial node (pacemaker that initiates the electrical impulse for ea. heart beat) to slow the heartbeat and inhibit contraction. •trimeric G-protein-linked receptor that leads to activation of a K+ channel •(G-protein-mediated mechanism discussed in paper) •Remember K+ channel has opposite effect of Na+ channel and, thus, HYPERPOLARIZES plasma membrane
Image of page 2
G protein signaling pathway - Background - Acetylcholine receptors •Two kinds of muscle ACh receptors lead to different responses •Sinoatrial node (pacemaker that initiates the electrical impulse for each heart beat) •rhythmic impulses generated by ordered opening and closing of different ion channels •Na+ channels depolarize membrane to a threshold that triggers opening of voltage gated Ca++ channels in the plasma membrane. •Rapid influx of Ca++ generates the electrical impulse that sends an electrical impulse to the heart and causes contraction. •Subsequent opening of K+ channels hyperpolarizes the membrane. •Next heart beat is initiated by opening of Na+ channels.
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.
  • Spring '08
  • Hanna-rose,W
  • Ion channel, Muscarinic acetylcholine receptor, Nicotinic acetylcholine receptor, k+ channel, Acetylcholine receptor

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern