Animal Physiology Study Guide

A set of flashcards covering key concepts in animal physiology, focusing on neuronal functions, sensory reception, the nervous system, and homeostasis.

Membrane Potential (Vₘ)

The electrical potential difference across a cell's plasma membrane, created by differences in ion concentrations.

Resting Membrane Potential

The membrane potential maintained by the Na⁺/K⁺ pump and leak channels, typically around -70mV.

Resistance (R)

Hindrance to ion flow; high resistance reduces current leak.

Conductance (g)

The inverse of resistance; a measure of how easily ions flow through open channels.

Capacitance (Cₘ)

The ability of the lipid bilayer to store charge.

Equilibrium Potential (Eᵢₒₙ)

The membrane potential at which there is no net flow of that ion across the membrane.

Voltage-Gated Channels

Channels that open in response to changes in membrane potential, crucial for generating action potentials.

Excitatory Postsynaptic Potentials (EPSPs)

Depolarizations that increase the chance of an action potential in the postsynaptic cell.

Inhibitory Postsynaptic Potentials (IPSPs)

Hyperpolarizations that decrease the chance of an action potential in the postsynaptic cell.

Refractory Period

The period after an action potential when it is difficult or impossible to initiate another.

Dark Current

In the dark, Na⁺ channels are open, allowing a steady inward Na⁺ current that depolarizes photoreceptors.

Ryanodine Receptor

Ca²⁺ release channel on the Sarcoplasmic Reticulum that opens in response to DHP receptor activation.

Glucocorticoids

Hormones that raise blood glucose and suppress the immune system, example includes Cortisol.

Renin-Angiotensin System (RAS)

A hormone system that regulates blood pressure and fluid balance.

Osmoregulators

Organisms that maintain a constant internal osmolarity regardless of the environment.

Systole

The phase of cardiac contraction where the heart muscles contract and pump blood.

Diastole

The phase of cardiac relaxation where the heart fills with blood.

Peristalsis

Coordinated waves of contraction that propel food along the digestive tract.

Enterogastric Reflex

A neural/hormonal reflex that inhibits gastric motility and secretion.

Membrane Potential (V
H

The electrical potential difference across a cell's plasma membrane, created by differences in ion concentrations.

What is the unit of measurement for membrane potential?

Volts (V), or millivolts (mV).

How is membrane potential measured?

Using microelectrodes.

What two types of gradients contribute to the electrochemical gradient across a membrane?

Electrical and Chemical gradients.

Is the inside of a resting cell typically more positive or negative than the outside?

Negative.

Resting Membrane Potential

The membrane potential maintained by the Na⁺/K⁺ pump and leak channels, typically around -70mV.

What mechanisms primarily maintain the Resting Membrane Potential?

The Na⁺/K⁺ pump and leak channels.

What is the approximate voltage of the Resting Membrane Potential?

Around -70mV.

How many Na⁺ ions does the Na⁺/K⁺ pump typically move out for every K⁺ ion moved in?

3 Na⁺ out, 2 K⁺ in.

What is the net charge movement by the Na⁺/K⁺ pump in one cycle?

1 net positive charge moves out, contributing to negativity inside the cell.

Are K⁺ leak channels typically more numerous than Na⁺ leak channels?

Yes.

What is the major ion responsible for setting the resting membrane potential?

Potassium (K⁺).

If a cell became more permeable to Na⁺ at rest, would the resting potential become more positive or negative?

More positive (less negative).

Does the electrochemical gradient for K⁺ favor its movement into or out of the cell at resting potential?

Out of the cell, due to the chemical gradient outweighing electrical attraction.

Resistance (R)

Hindrance to ion flow; high resistance reduces current leak.

Define Resistance (R) in the context of ion flow.

Hindrance to ion flow.

What effect does high resistance have on current leak?

High resistance reduces current leak.

What cellular component provides resistance to ion flow?

The plasma membrane/lipid bilayer.

What determines the resistance of a membrane?

The number of open ion channels, membrane thickness, and lipid composition.

How is resistance related to the permeability of a membrane to ions?

Higher resistance means lower permeability.

What units are used for resistance?

Ohms (\Omega).

According to Ohm's Law, what is the relationship between voltage, current, and resistance?

V = IR or I = V/R.

Conductance (g)

The inverse of resistance; a measure of how easily ions flow through open channels.

How is Conductance (g) related to resistance?

It is the inverse of resistance (g = 1/R).

What does Conductance (g) measure?

How easily ions flow through open channels.

When is conductance high?

When many ion channels are open.

What cellular structures provide conductance paths for ions?

Ion channels.

How does the opening of ion channels affect membrane conductance?

It increases membrane conductance.

What units are used for conductance?

Siemens (S).

What is the relationship between current, voltage, and conductance?

I = gV.

Capacitance (C
H

The ability of the lipid bilayer to store charge.

Define Capacitance (C_m).

The ability of the lipid bilayer to store charge.

What part of the cell has capacitance?

The lipid bilayer of the plasma membrane.

Is the lipid bilayer a good conductor or insulator?

An insulator.

How does membrane capacitance affect the speed of voltage changes across the membrane?

Higher capacitance slows down voltage changes.

What is the relationship between membrane thickness and capacitance?

A thicker membrane generally has lower capacitance.

What units are used for capacitance?

Farads (F), or microfarads (\mu F).

How does myelination affect membrane capacitance?

Myelination decreases membrane capacitance, which increases conduction speed.

Equilibrium Potential (Eᵢₒₙ)

The membrane potential at which there is no net flow of that ion across the membrane.

What defines the Equilibrium Potential (E_{ion})?

The membrane potential at which there is no net flow of a specific ion across the membrane.

What happens to ion flow at the Equilibrium Potential?

There is no net flow of that ion across the membrane.

If the membrane potential equals the equilibrium potential for an ion, what is the net movement of that ion?

There is no net movement.

What equation is used to calculate the equilibrium potential for a single ion?

The Nernst Equation.

What two forces are balanced at the equilibrium potential?

The electrical gradient and the chemical (concentration) gradient.

What would be the net movement of Na⁺ if the membrane potential was more negative than its equilibrium potential?

Inward movement (into the cell).

What would be the net movement of K⁺ if the membrane potential was more positive than its equilibrium potential?

Outward movement (out of the cell).

If K⁺ is primarily concentrated inside the cell, what would its equilibrium potential typically be?

Negative.

Voltage-Gated Channels

Channels that open in response to changes in membrane potential, crucial for generating action potentials.

What triggers Voltage-Gated Channels to open?

Changes in membrane potential.

What is a key function of Voltage-Gated Channels?

Generating action potentials.

Are Voltage-Gated Channels involved in resting potential or action potentials?

Action potentials.

Name an ion commonly associated with voltage-gated channels in neurons.

Na⁺, K⁺, or Ca²⁺.

What are the three main states of a voltage-gated Na⁺ channel?

Closed, Open, and Inactivated.

Which state of a voltage-gated Na⁺ channel prevents immediate re-opening?

The inactivated state.

How do voltage-gated K⁺ channels contribute to the repolarization phase of an action potential?

Their delayed opening leads to K⁺ efflux, contributing to repolarization.

Excitatory Postsynaptic Potentials (EPSPs)

Depolarizations that increase the chance of an action potential in the postsynaptic cell.

Define Excitatory Postsynaptic Potentials (EPSPs).

Depolarizations that increase the chance of an action potential in the postsynaptic cell.

What electrical change is associated with EPSPs?

Depolarization.

How do EPSPs affect the likelihood of an action potential?

They increase the chance of an action potential.

Are EPSPs typically depolarizing or hyperpolarizing?

Depolarizing.

What happens to the membrane potential during an EPSP?

It becomes less negative (more positive).

Do EPSPs typically involve the influx of positive ions or efflux of negative ions?

Typically influx of positive ions (e.g., Na⁺).

Are EPSPs graded potentials or action potentials?

Graded potentials.

What is summation in the context of EPSPs?

The combining of multiple EPSPs to reach the threshold for an action potential.

Name the two types of summation for EPSPs.

Temporal summation and Spatial summation.

Inhibitory Postsynaptic Potentials (IPSPs)

Hyperpolarizations that decrease the chance of an action potential in the postsynaptic cell.

Define Inhibitory Postsynaptic Potentials (IPSPs).

Hyperpolarizations that decrease the chance of an action potential in the postsynaptic cell.

What electrical change is associated with IPSPs?

Hyperpolarization.

How do IPSPs affect the likelihood of an action potential?

They decrease the chance of an action potential.

Are IPSPs typically depolarizing or hyperpolarizing?

Hyperpolarizing.

What happens to the membrane potential during an IPSP?

It becomes more negative.

Do IPSPs typically involve the influx of negative ions or efflux of positive ions?

Influx of negative ions (e.g., Cl⁻) or efflux of positive ions (e.g., K⁺).

How do IPSPs counteract EPSPs?

By moving the membrane potential further away from the threshold for an action potential.

Can IPSPs also undergo summation?

Yes, both temporal and spatial summation.

Refractory Period

The period after an action potential when it is difficult or impossible to initiate another.

When does the Refractory Period occur?

Immediately after an action potential.

What is the characteristic of the Refractory Period regarding action potentials?

It is difficult or impossible to initiate another action potential.

What are the two types of refractory periods?

Absolute Refractory Period and Relative Refractory Period.

During which refractory period is it impossible to initiate another action potential, regardless of stimulus strength?

The Absolute Refractory Period.

What causes the absolute refractory period?

The inactivation of voltage-gated Na⁺ channels.

During which refractory period is it possible to initiate another action potential, but only with a stronger than normal stimulus?

The Relative Refractory Period.