Flashcards in The Nervous and Endocrine Systems Deck (69)
1. Nerve cells. Soma contains usual organelles.
2. Carries impulses from place to place, received at dendrites (spiky things) and transmitted to axon.
3. The inside of a neuron is more negatively charged than the outside.
Resting membrane potential
1. Inside of a cell is more negative
2. A neuron is polarized when resting
3. -70 mV in humans
An electrical signal.
Na/K ATPase and K leak channel, help to set up resting membrane potential.
K channels that are always open and allow K to leak out of the cell according to its gradient.
How is the inside of a neuron more negative?
1. Na/K ATPase uses a molecule of ATP to move 3 Na ions out of the cell, while moving 2 K ions into the cell.
2. Eventually there is more Na outside the cell and more K inside the cell. These molecules are charged and can't cross the membrane without a channel.
3. Leak channels and pumps allow Na and K to leave the cell, leaving negatively charged items inside the cell, like DNA and proteins.
Charge of K and Na
Voltage Gated Channels
1. Channels in a neuron that open when the cell membrane reaches a particular voltage.
2. 2 types: Na voltage gated and K voltage gated
3. Will open if a neuron is polarized and depolarizes slightly.
Point at which voltage gated channels open (-50 mV)
1. Movement of ions to restore resting membrane potential
2. Causes a chain of action potentials down the axon of the cell.
3. During this, the membrane is positive on the inside and negative on the outside.
Membrane potential moves in the positive direction.
Membrane potential returns to its resting value (negative direction).
Something sticking off of something else.
Process of an action potential
1. If a neuron is polarized and depolarizes slightly, VGC open.
2. Na channels open first, and Na enters according to concentration gradient.
3. Na depolarizes the cell further, reaches a max of +35 mV before Na channels close.
4. K channels open, K enters cell according to concentration gradient.
5. Exiting K ions repolarize the cell, bypassing resting membrane potential to min -90 mV before channels close.
6. Na/K ATPase and K leak channels return membrane to resting polarized state.
Wrapping of Schwann cells, which wrap some axons, increases speed of an impulse.
Nodes of Ranvier
Space between Schwann cells.
Only nodes of Ranvier conduct impulses, so impulses jump from node to node.
1. For a short period of time after firing an action potential, that portion of the membrane can't fire a second
2. This ensures the action potential will only travel away from the cell body.
Point where an impulse is transferred.
Small gap between neurons.
A neuron receives multiple impulses, and will add them up. More stimulatory impulses will cause an action potential.
To depolarize toward threshold, can cause an action potential.
Move away from threshold.
When an impulse reaches the end of an axon
1. An impulse will be transferred to another neuron's dendrite or to an organ.
2. Most neurons use a neurotransmitter to transfer impulses, acetylcholine being the most common.
3. Terminal end of axon 1 contains vesicles with neurotransmitter
4. When the action potential reaches them, vesicles fuse with the cell membrane and nt is released by exocytosis
5. It crosses synaptic cleft and binds with receptors on neuron 2.
6. Receptors are usually connected to ion channels that open when nt binds.
Central nervous system
1. Brain and spinal cord.
2. Like a command center where information is processed and decisions are made.
3. Composed of interneurons
Peripheral nervous system
1. Neurons outside the brain and spinal.
2. Connects CNS to all other centers
3. Composed of sensory and motor neurons
4. Subdivided into somatic and autonomic nervous systems.
Connect sensory and motor neurons.