AP Biology Chapter 37: Neuron Structure and Function

What is a neuron?

The cell type used for both structure and function within the nervous system

What are the three types of neurons?

Sensory neurons, interneurons, motor neurons

What do sensory neurons do?

Transmit information from a sense receptor to the brain or spinal cord

What do interneurons do?

Integrate information within the brain or spinal cord and connect sensory and motor neurons; located within the central nervous system

What do motor neurons do?

Transmit information from the brain or spinal cord to a muscle or gland, causing muscle contraction or gland secretion

Which division of the nervous system includes the brain and spinal cord?

The central nervous system

What is a neurotransmitter?

A chemical that affects an adjacent cell

What are the two types of neurotransmitters?

Excitatory and inhibitory

Which type of neurons have long dendrites and shorter axons? Short dendrites and longer axons?

Sensory neurons have long dendrites and short axons, motor neurons have short dendrites and long axons

What do dendrites do?

Receive information and stimuli

What do axons do?

Carry signals to the next neuron

What is a synapse?

The connection between two neurons

What is the synaptic cleft?

The gap between the presynaptic and the postsynaptic cell

What are the synaptic vesicles?

Vesicles that carry neurotransmitters and ions

What are glial cells?

Non-conducting, support cells within the nervous system

What is the typical resting potential of a neuron?

-70 millivolts

How are the concentration gradients of NA+ and K+ maintained?

Active transport; through sodium potassium pumps

What are the key points about hyperpolarization?

-membrane potential gets farther away from 0

-inhibitory

-loss of K+ ions

What are the key points about depolarization?

-membrane potential gets closer to 0

-excitatory

-gain of NA+ ions

What is the critical value caused by depolarization called? At what charge does it occur?

A threshold, and it occurs at -55 millivolts

What is a wave of depolarization called?

Action potential

What kind of response is it when there are only two options: a huge response, or no response at all?

An all or nothing response

What are the 5 states of nerve impulse transmission? Describe them.

Resting state, Depolarization, Rising phase of the action potential, Falling phase of the action potential, and Undershoot

Are NA+ and K+ channels open or closed during the resting state?

Closed

What triggers depolarization? What channels open during this, and what occurs if the threshold is reached?

An outside stimulus triggers depolarization, during which sodium channels open, and if the threshold is reached, an action potential occurs

During repolarization, how is the membrane charge reestablished?

Potassium channels open, which permits K+ flow

What would the membrane charge graph look like if no threshold was reached?

There would be no spike/peak, which represents the action potential

What are the 3 steps of an action potential being conducted?

The action potential is generated from NA+ flowing inwards across the membrane at one specific location. Depolarization of the action potential spears to a neighboring location, forming the action potential there (the original location repolarizes). The depolarization/repolarization process repeats, carrying the action potential down the axon

What are the two types of glial cells that produce myelin sheaths?

Schwann cells and oligodendrocytes

How does a myelin sheath speed impulse transmission?

It blocks and covers ion channels, causing a signal to jump from place to place, and skip over some locations, so messages can be sent quickly

If myelin sheaths hardened and deteriorated, how would the nervous system function be affected?

Loss of the insulation from the myelin sheaths leads to a disruption of action potential, so the membrane can't depolarize

What occurs to synaptic vesicles as Ca2+ levels increase?

They fuse with the presynaptic membrane, and release neurotransmitters into the synaptic cleft, so they can move to the postsynaptic membrane

What is contained within the synaptic vesicles?

Neurotransmitters

What are the 3 steps of an action potential being transmitted across a synapse?

Synaptic vesicles with neurotransmitters arrive at the end of the presynaptic cell. An increase in calcium ions causes vesicles to fuse with the membrane and release the neurotransmitters. Neurotransmitters trigger receptors on the postsynaptic membrane, and then travel back to the original cell

Insulin

Hormone produced by the pancreas that helps to decrease blood sugar. lowers blood glucose levels by enhancing the rate of glucose uptake and utilization by target cells, which use glucose for ATP production.