SHPEP A&P - neurons (lecture 6)

Central nervous system

brain and spinal cord, function n control and interaction

Peripheral nervous system

Cranial nerves and spinal nerves, connects CNS to receptors, glands, etc

Neurons

A nerve cell; the basic building block (cell) of the nervous system. Conduct ELECTRICAL signals.

Neuroglia

Majority of all nerve tissue cells, support neurons

Dendrite

the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body

Cell body

Largest part of a typical neuron; contains the nucleus and much of the cytoplasm

Axonal hilock

Specialized region in a neuron where the cell body (soma) connects to the axon. It's a cone-shaped area crucial for initiating nerve impulses, acting as a trigger zone where incoming signals from other neurons are processed and integrated

Axon

A threadlike extension of a neuron that carries nerve impulses away from the cell body.

Axon terminal

The endpoint of a neuron where neurotransmitters are stored

Mylelin

an insulating layer (sheath) that forms around nerves in the brain and spinal cord. made up of protein and fatty substances. allows electrical impulses to transmit quickly and efficiently along the nerve cells.

afferent neurons

Nerve cells that carry impulses towards the central nervous system (ARRIVING).

efferent neurons

Nerve cells that conduct impulses away from the central nervous system (EXITING).

somatic nervous system

the division of the peripheral nervous system that controls the body's skeletal muscles (voluntary control of body movements).

autonomic nervous system

the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Regulates involuntary processes like heart rate, blood pressure, digestion, etc. think AUTO for AUTOMATIC processes.

Excitable tissues

neural and muscle tissue that is capable of generating and responding to electrical signals

Nerve and muscle tissues can undergo rapid changes in their resting membrane potentials, and can change their resting potentials into what?

Electrical signals

What is Resting Membrane Potential (RMP)?

Electrical potential energy produced by separation of oppositely charged particles across plasma membrane in all cells

What is the resting membrane potential for many neurons?

70 mV

At resting membrane potential, neither K+ nor Na+ are in…

…equilibrium

Polarization

membrane potential other than 0mV

Depolarization

The process during the action potential when voltage gated Na+ channels open up and sodium is rushing into the cell causing the interior to become LESS NEGATIVE.

When threshold is reached, what does this stimulate?

It stimulates the voltage-gated Na+ channels to open up

Repolarization

Return of the cell to resting membrane potential, caused by reentry of potassium into the cell (because voltage gated K+ channels open at this point) while voltage gated Na+ channels close/sodium exits the cell.

Hyperpolarization

The movement of the membrane potential of a cell away from resting potential in a more negative direction.

when too much K+ leaves the cell what happens?

Hyperpolarization occurs

What maintains/gets us to resting potential?

The sodium-potassium pump

What is the threshold potential?

-55mV

If we reach threshold potential, what will always occur?

An action potential will be generated

What's an action potential?

a rapid, transient rise and fall in voltage or membrane potential across a cell's membrane, specifically in excitable cells like neurons and muscle cells. It's essentially a brief electrical impulse that transmits information. This change in membrane potential is crucial for cell communication and is the basis of nerve impulses and muscle contractions.

A neuron would be most permeable to K+ during…

…Repolarization

A neuron would be most permeable to Na+ during…

…depolarization

Where is Na+ concentration higher?

outside the cell

Where is K+ concentration higher?

inside the cell

Leaky channels

non gated, channels that are always open

ligand-gated channels

channel that opens when a neurotransmitter attaches

voltage gated channels

open and close in response to changes in membrane potential

Mechanical gated channels

respond to physical changes such as pressure

What kind of channels are present in action potentials?

Action potentials primarily utilize voltage-gated sodium (Na+) and potassium (K+) channels. These channels open and close in response to changes in membrane voltage, allowing ions to flow in and out of the cell, thus driving the characteristic phases of the action potential.

What kind of channels does K+ utilize?

Leaky, and voltage gated channels

What kind of channels does Na+ utilize?

ONLY voltage gated channels that are closed at rest, and open when a particular membrane potential is reached (~55 mV)

What happens when a nerve cell 'fires'?

An electrical signal moves down the neuron

Electrical signals are produced by changes in…

…ion concentration (changes brought abt by triggering event)

Where do action potentials originate?

axon hillock

What are the two types of electrical signals?

graded potential and action potential

Difference between graded potential and action potential?

graded you don't use for a long time, action bigger and faster

refractory period

a period of inactivity after a neuron has fired

absolute refractory period

The minimum length of time after an action potential during which another action potential cannot begin, occurs due to inactivated Na+ channels

relative refractory period

the period of time following an action potential, when it is possible, but difficult, for the neuron to fire a second action potential, due to the fact that the membrane is further from threshold potential (hyperpolarized, due to continued outward diffusion of K+)

action potential propagation

Gthe process by which an electrical impulse, or action potential, travels down the axon of a neuron. It's how nerve signals move from one part of a neuron to another, and eventually to other cells, enabling communication within the nervous system.

Nodes of ranvier

Gaps in the myelin sheath to which VOLTAGE-GATED NA+ CHANNELS ARE CONFINED.f

Synapse

Communication junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron (between a neuron and either another neuron or a muscle/gland cell)

By what process are neurotransmitters released?

exocytosis

Saltatory conduction

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.

chemical synapse

a type of synapse at which a chemical (a neurotransmitter) is released from the axon of a neuron into the synaptic cleft, where it binds to receptors on the next structure (either another neuron or an organ)

electrical synapse

a type of synapse in which the cells are connected by gap junctions, allowing ions (and therefore the action potential) to spread easily from cell to cell

The release of neurotransmitters stimulates what kind of changes?

Physiological change (usually change in membrane potential) in the recipient cell

For neurotransmitters to cross the synapse, action potentials trigger what to open?

Calcium (Ca2+) channels open up, and calcium rushes in

Calcium triggers the cell membrane to…

…undergo exocytosis to release the neurotransmitters

When neurotransmitters binds to receptors on the postsynaptic cell membrane, ligand-gated ion channels open, which induces what?

A synaptic potential (electrical signal) in post synaptic cell

What are the two types of synaptic potential?

Excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potential (IPSP)

excitatory postsynaptic potential (EPSP)

Depolarizes the cell, making it LESS NEGATIVE

inhibititory postsynaptic potential (IPSP)

Hyper-POLARIZES the cell, making it MORE NEGATIVE

Excitatory neurotransmitter

Opens channel that depolarizes postsynaptic membrane

inhibitory neurotransmitters

chemicals released from the terminal buttons of a neuron that inhibit the next neuron from firing

G-protein coupled receptors

The neurotransmitter receptor is separate from the protein that serves as the ion channel

Example of G protein-coupled receptor

Pacemaker cells of the heart

Acetylcholinesterase (AChE)

the enzyme that breaks down acetylcholine in the synaptic cleft, which are taken back into the pre synaptic cell for reuse