Why could you compare the cell membrane to the gates of a stadium ?

HOW DO SUBSTANCES GET INTO and OUT OF THE CELL?

Before we start---

1) Passive diffusion page– fix the Oxygen with one circle to two circles—O2

2) Sodium page– Left side --add 4 more sodium (Na) to inside the cell

3) Active transport page– Left side- add one sodium (Na) to the inside

HOW DO SUBSTANCES GET INTO THE CELL?

The cell membrane is the gate:

Passive transportSimple diffusionFacilitated diffusion by a protein

Active Transport

Simple diffusion

Facilitated Diffusion with the help of proteins

Diffusion--- Movement of a substance from an area

of high concentration to lower concentration

Active transport---Use of energy (ATP) to transport a substance from low to high concentration

CYSTIC FIBROSISBy:  Dr. Barb GoodmanThe American Physiological Society, Education Office

Cystic fibrosis is an inherited disease that is relatively common in the U.S.  Cystic fibrosis affects multiple parts of the body including the pancreas, the sweat glands, and the lungs. 

When someone has cystic fibrosis, they often have lots of lung problems.  The cause of their lung problems is directly related to basic problems with diffusion and osmosis in the large airways of the lungs.

http://www.the-aps.org/education/lot/cell/cell-ebration.html

People without cystic fibrosis have a small layer of salt water in the large airways of their lungs. 

This layer of salt water is under the mucus layer which lines the airways. 

The mucus layer in the airways helps to clear dust and other inhaled particles from the lungs.

In people without cystic fibrosis, working cystic fibrosis proteins allow salt (chloride) to enter the mucus layer and water follows by osmosis.  The mucus layer is dilute and not very sticky.

In people with cystic fibrosis,

                                                                                                         

                                                                                        non-working cystic fibrosis proteins mean no salt (chloride) enters the space and water doesn't either.  The mucus layer is concentrated and very sticky.

People with cystic fibrosis have lung problems because: 

    ~Proteins for diffusion of salt don't work.   (less diffusion)     ~Less salt means less water in the airways.               (less osmosis)

    ~ Less water in the airways means mucus layer is very sticky

    ~Sticky mucus cannot be easily moved to clear particles from the lungs.

    ~Sticky mucus traps bacteria and causes more lung             infections.

Three DNA bases are deleted in the mutated sequence, resulting in the deletion of an amino acid (phenylalanine) from the CF  protein.

People with the abnormal protein develop cystic fibrosis

Genome.gov

Biology Workbench

The Nerve Impulse

Fig. 2-12, p. 37

The Cells of the Nervous System

Active transport is the protein mediated process by which useful chemicals are brought into the brain.

Glucose, hormones, amino acids, and vitamins are brought into the brain via active transport.

Fig. 2-2, p. 31

The Cells of the Nervous System

All neurons have the following major components: Dendrites. Cell body. Axon. Presynaptic terminals.

The Nerve Impulse The membrane is selectively

permeable, allowing some chemicals to pass more freely than others.

Sodium, potassium, calcium, and chloride pass through channels in the membrane (what kind of diffusion?).

The resting potential of a neuron refers to the state of the neuron prior to the sending of a nerve impulse.

The membrane of a neuron maintains an electrical gradient which is a difference in the electrical charge inside and outside of the cell.

http://www.millersv.edu/~bio375/CELL/membrane/membrane.htm

At rest, the membrane maintains an electrical polarization or a difference in the electrical charge of two locations

the inside of the membrane is slightly negative with respect to the outside. (approximately -70 millivolts)

When the membrane is at rest:

Sodium channels are closed.

Potassium channels are partially closed allowing the slow passage of sodium.

In living cells nerve impulses are started by receptor cells.

Stimulus- food on a taste receptor

Biologymad.com

The Nerve Impulse The sodium-potassium pump is a

protein complex that continually pumps three sodium ions out of the cells while drawing two potassium ions into the cell. helps to maintain the electrical gradient.

Differential permeability of the neuron membrane to Na+ and K+ ions

These ions can only cross the membrane via specific ion channel proteins that allow facilitated diffusion:

ion channel proteinsodium pump

Fig. 2-14, p. 40

The Nerve Impulse

A nerve impulse is the electrical message that is transmitted down the axon of a neuron.

The speed of nerve impulses ranges from approximately 1 m/s to 100 m/s.

When a nerve impulse is transmitted along a neurone a wave of electrical activity passes along it (NB: it is NOT a flow of electrons so it is not an electrical current)

This can be detected (e.g. by using oscilloscope with electrodes placed inside and outside the neurone) as a

transient change in electrical charge on the membrane surface –

this is called an ACTION POTENTIAL and is the basis of the nerve impulse.

The nerve impulse.

The Nerve Impulse

The resting potential remains stable until the neuron is stimulated.

The Nerve Impulse

An action potential is a rapid depolarization of the neuron.

Stimulation of the neuron past the threshold of excitation triggers a nerve impulse or action potential.

Action Potential

http://www.youtube.com/watch?v=pbg5E9GCNVE

The Nerve Impulse After an action potential occurs, sodium

channels are quickly closed.

The neuron is returned to its resting state by the opening of potassium channels.

The Nerve Impulse

Local anesthetic drugs block sodium channels and therefore prevent action potentials from occurring. Example: Novocain

Motor end plate

Synapses between motor nerve and muscle

Neurones are connected together (normally via axons and dendrites) at synapses

This is not a physical junction, there is actually a small gap of approx 20 nm between the cells so there is no membrane continuity so nerve impulses cannot cross directly.

synaptic vesicles

synaptic bulb

pre-synaptic membrane

post-synaptic membrane

How nerve impulses are transmitted across a synapse by neurotransmitters

Transmission is mediated by chemicals called neurotransmitters

Stored in vesicles in the synaptic bulb

Several different types of neurotransmitters

Acetyl choline

The pathogenesis of Alzheimer’s disease (AD) has been linked to a deficiency in the brain neurotransmitter acetylcholine.

Subsequently, acetylcholinesterase inhibitors (AChEIs) were introduced for the symptomatic treatment of AD.

http://www.livinghistoryfarm.org/farminginthe70s/media/pests_0601.jpg

How do drugs cause their effects on the brain and behavior? Drugs interfere with neurotransmission.

More specifically, drugs of abuse produce feelings of pleasure by altering neurotransmission by neurons in the reward system that release the neurotransmitter dopamine.

Drugs

http://learn.genetics.utah.edu/content/addiction/drugs/mouse.html

Nerve Gas http://faculty.washington.edu/chudler/weap.html

Methamphetamine alters dopamine neurotransmission in two ways.

1) enters the neuron by passing directly through nerve cell membranes.

2) carried to the nerve cell terminals by transporter molecules that normally carry dopamine or norepinephrine.

3) causes the release of neurotransmitter and also blocks the dopamine transporter from pumping dopamine back into the transmitting neuron..

Nicotine acts at the cell body to increase the number

of action potentials and number of vesicles released from a neuron,

Drugs may also alter synaptic transmission by directly affecting the postsynaptic receptors.

Some drugs activate receptors, and others block them.

Cocaine

1) enters the brain,

2) blocks the dopamine transporter from pumping dopamine back into the transmitting neuron, flooding the synapse with dopamine.

3) This intensifies and prolongs the stimulation of receiving neurons in the brain's pleasure circuits, causing a cocaine "high."

http://science-education.nih.gov/supplements/nih2/addiction/guide/guide_toc.htm