Nervous system 3- Electrical Events Flashcards Preview

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Flashcards in Nervous system 3- Electrical Events Deck (33):

Describe the somatic nervous system

Motor neurones to skeletal muscle. Voluntary control


Why two systems make up the peripheral system

The somatic nervous system and autonomic nervous system


Describe the autonomic nervous system

Neruones to visceral organs, no voluntary control. Made up of sympathetic and parasympathetic


Why are communication pathways rapid

Peripheral nerves transmit information rapidly. Nerve impulses travel to and from the central nervous system.


What are the main components of a neurone

Synapse, nucleus, soma, axon, Schwann cell, terminus


What is the approximate concentration of Na+ inside and outside the cell membrane

Inside = 15 mM Outside = 150 nM


What is the approximate concentration of K+ inside and outside the cell membrane

Inside = 150 mM Outside = 5 mM


What is the approximate concentration of Cl- inside and outside the cell membrane

Inside = 10 mM Outside = 100 mM


Why are there unequal concentrations of ions either side of the cell membrane

1. Large organic anions are produced by the cell and cannot cross the membrane 2. Active transport (Na+/K+ pump) actively transports Na+ out of the cell and K+ into the cell


What does what can get through the cell membrane depend on

Size, electrical charge, molecular shape, solubility


Why do membranes differ in permeabilities

It depends on lipids and proteins present and their arrangement


Describe cell membranes in their resting state

1. Fairly permebale to K+ and Cl-. 2. Poorly permeable to Na+. 3. Impermeable to various large organic anions formed in the cells


What happens at a concentration gradient

Substances move down the concentration gradient from high concentration to low concentration


What happens at an electrical gradient

Ions move down the electrical gradient from positive side to negative side


Describe a cell in steady state

1. Net passive efflux of K+. 2. Net passive influx of Na+. 3. Cell is not loosing Na+, K+, Cl- or A-. 4. Outside of cell is positive compared to inside of cell


Why does a cell in it's resting state have a potential difference

The outside of the cell is positive compared to the inside of the cell


How can the potential difference of a cell be measured

By using a microelectrode


What is the resting membrane potential of a typical neurone



What are the 3 stages that happen during an action potential

1. Depolarisation 2. Repolarisation 3. Hyperpolarisation


What happens during depolarisation

1. After a stimulus the membrane depolarises due to a change in potential difference. 2. Na+ voltage-gated channels open. 3. There is a rapid influx of Na+ into the cell. 4. Causes more Na+ voltage-gated channels to open via a positive feedback loop.


What happens immediately after an action potential peaks



What happens during repolarisation

1. Na+ voltage-gated channels close. 2. Decreases the permeability of Na+ into the axon. Strong electrochemical gradient established. 3. K+ voltage-gated channels open. 4. K+ leaves the cell. 4. The potential of the cell is decreased


What is hyperpolarisation

1. The depolarisation continues past the resting -70mV. 2.This causes the K+ voltage-gated channels to close. 3. The cell returns to resting potential


Why can't an new action potential occur directly after an action potential

Due to the refractory period


What is absolute refractory

When an action potential is at it's peak and there is no way another action potential can occur


What is relative refractory period

Occurs immediately after the absolute refractory period. Another action potential could potentially occur but must be much stronger than initial stimulus.


Where does the propagation of action potentials occur

In unmyelinated neurones


What is the propagation of action potentials

There is an inactive area at resting potential -> Active area which is being depolarised (a graded potential) -> an inactive area at resting potential.


Which directions can action potentials travel in

Only one direction. From the cell body to the end of the axon


What does myelinated cells result in

Faster transmission


Where and how do action potentials travel down myelinated cells

They occur at the nodes of Ranvier. Local circuit currents cause depolarisation of adjacent node of Ranvier so a new AP is initiated here


How often do the nodes of Ranvier occur

Every 0.2-2mm


What happens to the propagation of action potentials at cooler temperatures

It is slower due to decreased a decrease in speed of metabolic activity. Results in the period of inactivation at sodium voltage-gated channels being longer. So signals are not sent because gates have not yet closed from previous action potential