CH 12 - NERVOUS SYSTEM & CH 13 - SPINAL CORD

What is an action potential?

During action potential the first channels to open are the sodium (Na+) channels. The sodium ions will rush in causing depolarization. The potassium ion channels open during depolarization. They allow the potassium ions (K+) to rush out and producing repolarization.

What does myelination mean?

Myelination is when special lipids (fats) and proteins are wrapped around the axons of neurons. Myelination makes an electrical insulator to speed up the conduction of nerve impulses.

What is a neuroglial cell?

Neuroglial cells are support cells for neurons...think of them as sidekicks. They're the Robin to the Neuron's Batman. There are 6 types of neuroglial cells. Four are found in the CNS and 2 are in the PNS.

What is resting membrane potential?

Resting membrane potential is -70mv

What is threshold membrane potential?

Threshold membrane potential is -55mv

The brain is _______________ matter surrounding ____________ matter.

gray matter surrounding white matter

The velocity of a nerve impulse conduction is greatest in:

heavily myelinated, large diameter fibers

Chemical synapses are characterized by all of the following except:

ions flowing through protein channels from the pre-synaptic to post-synaptic neuron.

The spinal cord is __________ matter surrounding __________ matter.

white matter surrounding gray matter

What are the meninges?

Meninges are special connective tissue coverings encircling the brain and spinal cord.

What are the phases to an action potential?

1) Depolarization Phase 2) Repolarization Phase

What's the dura mater?

Dura mater is dense irregular connective tissue that forms a sac from the foramen magnum to the sacral vertebra.

What are the astrocytes of the CNS?

Astrocytes are found close to the blood supply - capillaries. The astrocytes act as a bridge between the neurons and the artery. They will carry food material from the artery to the soma of the neuron. This formation is called the "blood brain barrier."

Action potentials arise according to the ________ _____ ________ response.

ALL OR NOTHING This means that you will either have an action potential or you won't have one.

What is continuous conduction as opposed to saltatory conduction?

Continuous conduction happens on axons of neurons that are NOT myelinated. Continuous conduction is slow because the axons have no electrical insulation. Saltatory is rapid conduction.

What are IPSPs?

Inhibitory Postsynaptic Potentials or IPSP happens when a neurotransmitter causes hyperpolarization of the postsynaptic membrane. When you think hyperpolarization think IPSP. Hyperpolarization means more negative.

What are microglia?

Microglia are the brain macrophages. This means that they engulf substances that are harmful to the neurons. They are able to do this through use of phagocytosis.

Gray matter is shaped like:

The letter H or like a butterfly

The anatomical region of a multi-polar neuron that has the lowest threshold for generating an action potential is the:

axon hillock.

The arachnoid mater looks like what?

Looks like spider webs because it is made of delicate collagen and elastic fibers

What are EPSPs?

Excitatory Postsynaptic Potentials result from opening of ligand gated positive ion channels. EPSPs bring the membrane closer to the threshold. The EPSP does not initiate a nerve impulse. Instead it makes it more likely to reach threshold because EPSPs cause depolarization (the act of making it more positive.)

What is ganglia?

Ganglia are small masses of nervous tissue. They contain the cell bodies of neurons. They are located outside the brain and spinal cord.

Which cells produce no action potentials?

NEUROGLIAL CELLS

Speaking of neurons..... What are they made of?

Neurons have a cell body or "soma" (AKA the perikaryon) where the nucleus is housed. Inside the soma there are Golgi bodies, an endoplasmic reticulum, ribosomes, Nissl bodies (which is called rough endoplasmic reticulum) and elements of normal cells. The soma has dendrites sticking out from it. There's an axon which goes all the way down from the soma like the trunk of a tree. Between the soma and the beginning of the axon is the axon hillock. At the end of the axon are the axon terminals which will connect one neuron to another neuron. Plus, the myelin sheath on the outside of the axons, which are accompanied by the nodes of Ranvier.

What provides the gray coloring in gray matter?

Nissl bodies provide the grayness. Gray matter is also colored this way due to lack of myelin.

What are oligodendrocytes?

Oligodendrocytes are attached to axons and they secrete myelin in the CNS. In the PNS, Schwann cells carry out this function, but in the CNS the oligodendrocytes myelinate axons.

Explain the refractory period.

Refractory period is the time frame after repolarization where a neuron cannot generate another action potential. Refractory periods can be either absolute or relative. Absolute means that the action potential can't be initiated. Not even a super strong stimulus can generate an action potential. Relative refractory is the time frame when a second action potential can only be initiated by a suprathreshold stimulus.

What does myelination have to do with saltatory conduction?

Saltatory conduction is when a nerve impulse jumps along the axon. When an axon is myelinated the axon takes on the appearance of a poodle's puffy tail. The myelination thereby creates what is called the nodes of Ranvier. Action potential hops along the nodes of Ranvier rapidly.

What are satellite cells?

Satellite cells are flattened cells around the cell bodies of neurons in ganglia. They support neurons in PNS ganglia.

What do Schwann cells do?

Schwann cells produce the myelin sheath that wraps around a single axon of the neurons in the PNS. They also assist in regeneration of the PNS axons.

What is a stretch reflex?

Stretch reflex is a monosynaptic reflex arc. Two types of neurons are involved (one sensory and one motor), and there is only one CNS synapse in the pathway. • This reflex results in the contraction of a muscle (effector) when the muscle is stretched. • Stretch reflexes can be elicited at the elbow, wrist, knee, and elbow joints.

Name the cranial meninges.

The Dura Mater The Arachnoid Mater The Pia Mater

What are the types of glial (neuroglial) cells found in the Peripheral Nervous System?

The Schwann cells and satellite cells

What are the types of glial cells found in the Central Nervous System?

The astrocytes, oligodendrocytes, microglia, and ependymal cells

Nodes of Ranvier? What???

The nodes of Ranvier look like jelly rolls on the axon of neurons. In the CNS, the nodes of Ranvier are produced by the oligodendrocytes. In the PNS, the nodes of Ranvier come from Schwann cells. In the PNS, the Schwann cells begin forming the myelin sheath during fetal development.

What is the innermost meninge?

The pia mater is the innermost meninge. It adheres to the spinal cord and brain. It has many blood vessels which supply oxygen and nutrients to the spinal cord.

What is a synapse?

The place where an axon's branches (axon terminals) make contact with the next cell's dendrites. This is where neurotransmitters pass information from one cell to the next.

What are ependymal cells?

There are spaces inside the brain and spinal cord which are full of fluid. The fluid is called cerebrospinal fluid. The lining of these spaces is called the ependyma (greek word - means covering) and is made of ependymal cells. These ependymal cells are derived from neuro-stem cells and they are ciliated epithelial cells which produce CSF. They form a barrier between the cerebrospinal fluid and the interstitial fluid.