Membranes & Receptors Chemical compounds & electricity are the medium through which, cells communicate! Analogous with information sent via electrical pulses. Ex. Information sent as “actual” messages (letters etc.) rather than “virtual” such as hormones How do cells communicate throughout the body? BI 201 Human Anatomy & Physiology

Chemical signals called ____________ ____________ are molecules with a special spot for the ligand to bind to called either a ________ ____ or a ___________ _____. __________! ~ Lock and Key theory BI 201 Human Anatomy & Physiology How do receptors respond only to the proper signal?

If I had 2 ligands, one that was water soluble and one that was lipid soluble. Which one could enter a cell and interact with an “intracellular receptor”? ? What if there were two molecules, one very large one and one very small one, which one might be restricted to interacting with “membrane bound receptors”? ? BI 201 Human Anatomy & Physiology

Ligands bound with membrane bound receptors cause one of three reactions: 1)1) 2)2) 3)3) BI 201 Human Anatomy & Physiology How can a membrane bound receptor affect change on the inside of a cell?

The protein with the receptor site can be part of a _________ _________. When the ligand bonds, it changes the ______ (and hence function) of the channel protein BI 201 Human Anatomy & Physiology Changing membrane permeability will do what to the inside of a cell?

G proteins (bond with guanine nucleotides) Activated (GTP) Alpha subunit activates a response BI 201 Human Anatomy & Physiology What if the receptor doesn’t have a channel? subunits: Alpha Beta Gamma

Receptor proteins can activate or alter activity of __________ _______. An example is ____________ such as what happens when insulin binds with receptors. BI 201 Human Anatomy & Physiology What if the receptor doesn’t have any G- proteins?

Some ligands diffuse into cell and interact with _________ or ____ itself. DNA is code for specific proteins which, are the cell’s response Ex. __________ & 2ndry sex char. BI 201 Human Anatomy & Physiology How do intracellular receptors function?

Some drugs produce rapid responses, which disappear shortly after the drug is no longer present. Other drugs require many hours before a response is seen, and the effects of the drug take days or longer to disappear once the drug is discontinued. Why is one of these drugs is more likely to influence intracellular receptors and the other is more likely to influence membrane- bound receptors? BI 201 Human Anatomy & Physiology Take 5!!! Discuss with your neighbor and predict an answer.

Hormone Cell Response BI 201 Human Anatomy & Physiology How do different receptors result in response?

Electric signals (called _______________) are essential to nerve cell function and muscle contraction. Refer to tables 11.2, 3 & 4 BI 201 Human Anatomy & Physiology How does the body generate electric potential?

_________ with “-” charge stuck inside cells __________ channels that allow K+ to diffuse in or out of the cell Very few Na+ ions can diffuse through cell membrane EXCEPT via _____________ ___________ contributes to gradient Gated Non-gated BI 201 Human Anatomy & Physiology How does the body maintain electrical gradients?

As K+ diffuse out they leave ____________ inside the cell and develop an electric potential. When the “-” attraction inside the cell is = to the tendency for K+ to leave then __________ is established. Usually around -70 to -90 mVolts… called _______ ___________ BI 201 Human Anatomy & Physiology How does the body maintain electrical gradients?

1) 2) What are the 2 primary ways to change the resting potential? Decrease potential… _____________ (hypopolarization) Increase potential… _____________ BI 201 Human Anatomy & Physiology

What would the effect on the resting membrane potential be if the permeability of the plasma membrane to K+ was reduced? Why? BI 201 Human Anatomy & Physiology Take 5!!! Discuss with your neighbor and predict an answer.

What is the effect on the resting potential that results from changing Na+ concentrations? Change in Na+ ion concentration DOESN”T have much effect Change in permeability DOES Why? BI 201 Human Anatomy & Physiology

Cells such as muscle and nerve cells have >#... What properties make some cells electrically excitable? Depolarization causes the ___ channels to open quickly… (___ open more slowly and close more slowly)

What about the effects of Ca 2+ ions on the resting potential? When extracellular Ca2+ ions are reduced then they _________ _____ ______ (including gated Na+ channels, which causes them to open). What is the result of Hypocalcemia? BI 201 Human Anatomy & Physiology Ca 2+

A localized stimulus usually causes… a _____ _______ (change in resting membrane potential). Can be caused by: 1) 2) 3) 4) 5) BI 201 Human Anatomy & Physiology Are there any potentials other than resting potentials?

Changes in the resting potential can be at different levels of magnitude, i.e. ________ Influence of local potentials can be increased by ___________ BI 201 Human Anatomy & Physiology What are the properties of local potentials? Local potentials taper off as they move away from the stimulus source (see table 11.3)

If the threshold potential is reached… then an _______ _________ results These are propagated along the plasma membrane and are “_____________” 3 phases: Below the threshold = local potential ~ “______” Above the threshold = action ~ “______” BI 201 Human Anatomy & Physiology Do local potentials have any potential? (see table 11.4)

BI 201 Human Anatomy & Physiology How do those waves correlate with cellular reality?

What happens after all the excitement? Refractory period Until the voltage gated channels return to the resting state, no further action potential is possible. When totally insensitive…then ________ __________ _________ BI 201 Human Anatomy & Physiology

How do action potentials move along a cell? What keeps the action potential from reversing direction?

What about getting the electrical “message” (action potential) to the next cell? Generally accomplished via _________ _________ If ligand opens Na+ channels then… If ligand opens K+ channels then… BI 201 Human Anatomy & Physiology

Cardiac & smooth muscle tissue have _________ ____________. Action potentials can be propagated across adjacent cells via the ___ _________, which allow ions to pass through. BI 201 Human Anatomy & Physiology What about getting the electrical “message” (action potential) to the next cell?

Some neurons will continue to maintain a local potential sufficient to initiate action potentials. other neurons begin to become insensitive to continued stimulus and the frequency drops off until the local potential drops below threshold (_____________). BI 201 Human Anatomy & Physiology Do all neurons respond to continued stimulation equally?