Anatomy Final Exam (copy)

Peripheral Nervous System contains what divisions:

Enteric, Somatic, Automatic

Enteric division of the PNS:

regulates GI tract activity

Somatic division of the PNS:

involved in voluntary skeletal muscle activities

Automatic division of the PNS:

regulates activities of smooth muscle, cardiac muscle, and glands

What makes up the CNS?

Brain stem and Spinal Cord

Neurons (or nerve cells):

specialized cells that transmit and receive electrical signals in the body.

Basic neuron anatomy (3 parts)

Cell body (perikaryon), Axon, Dendrites

Cell body

perikaryon (cell body containing the nucleus)

Axon:

where electrical impulses from the neuron travel away to be received by other neurons

Dendrites:

receive signals from other cells

Axon terminal:

forms junctions with other cells

Synaptic end bulb:

once a nerve impulse reaches this, the neurotransmitter is released into the synaptic cleft

Axon hillock (what zone is this)

generates impulse in the neuron: axon hillock

Cytoskeleton:

* Microtubules and microfilaments, as well as neurofibrils (bundles of neurofilaments)
* Allow the rapid transport of small organelles
* protects the cell

What structures you'd find in the nerve cell body

Nucleus, Ribosomes, rough endoplasmic reticulum (ER), Golgi apparatus

\
Neurotransmitters are packaged into vesicles

\-Provide proteins for maintaining and regenerating nerve fibers

Different structural classifications of neurons

Multipolar, Bipolar, Unipolar

Multipolar neuron:

possesses a single axon and many dendrites

Bipolar neuron:

a type of neuron that has two extensions (one axon and one dendrite)

Unipolar neuron:

only has one nerve process extending from the cell body: an axon that extends into dendrites

6 neuroglial cells

Astrocytes, ependymal cells, microglia, oligodendrocytes, schwann cells, and satellite cells

Which glial cells are in the CNS

Astrocytes, microglia, ependymal cells, and oligodendrocytes

Which glial cells are in the PNS

Schwann cells and satellite cells

Astrocytes

* Star shaped; largest and most numerous type of glia
* Cell extensions connect to both neurons and capillaries
* Astrocytes transfer nutrients from the blood to the neurons
* Contributes to the brain blood barrier

Microglia

phagocytosis of inflamed brain tissue

Ependymal cells

line fluid-filled cavities in CNS, secrete cerebrospinal fluid

Oligodentrocytes

* Smaller than astrocytes with fewer processes (oligo-few dendricites- dendrites)
* Hold nerve fibers together and produce the myelin sheath in CNS
* (wrap around axons to myelinate them)

Schwann Cells

* Found only in peripheral neurons
* Support nerve fibers and form myelin sheaths in PNS
* Wrap themselves around axons to insulate and myelinate them
* Have nodes of ranvier

Nodes of ranvier:

gaps in the myelin sheath of a nerve, between adjacent Schwann cells.

Satellite cells:

supply nutrients to the surrounding neurons and also have some structural function

act as protective, cushioning cells

difference between gray and white matter

Gray matter: unmyelinated
White matter: myelinated

Sodium potassium pump ratio: what the potassium pump is, what it does, how it works

* Active transport mechanism in plasma membrane that transports 3 Na+ out for every 2 K+ in, in opposite directions and at different rates

What is the purpose of the sodium potassium pump

* Maintains and imbalance in the distribution of positive ions; as a result the inside surface becomes slightly negative with respect to its outer surface
* keeps cells in equilibrium in membrane

What happens when the sodium gates open:

if the sodium gates open, depolarization occurs (cell becomes rapidly positive) and an action potential is fired

What is membrane potential

slight excess of positively charged ions on the outside of the membrane and slight deficiency of positively charged ions on the inside of the membrane

Why is it called a membrane potential

Difference in electrical charge is called a potential because it is a type of stored energy

Polarized membrane

a membrane that has a membrane potential

What is an action potential

nerve impulse; when a neuron sends information down an axon, away from the cell body

Resting membrane potential:

determined by concentration gradients of ions across the membrane and by membrane permeability

* Typically -70 mV (resting membrane potential)

What is the slight excess of positive ions on a membranes outer surface produced by

by ion transport mechanisms and the membrane’s permeability characteristics

Concentration of Na+ in intercellular fluid (in cell) vs extracellular membrane at resting potential

More Na+ in the extracellular fluid as well as Cl- with less of a concentration in the cell.

(Think of cell of a salty banana)

Concentration of K+ in intercellular fluid (in cell) vs extracellular membrane at resting potential

lots of K+ AND negative protein molecules in the intercellular fluid with less of a concentration outside the cell (salty banana)

At how many mV does the depolarization reach threshold

at approx -55 mV

What happens after we pass threshold?

all the sodium channels open, and all the sodium rushes in: changes it from negative to positive,

outside of the cell is more negative now while the inside is more positive

Is the inside of the cell negative or positive at resting potential?

negative

Is the extracellular fluid negative or positive at resting potential?

positive

When nerve or sensory receptor is stimulated by a stimulus, to approx -45 mV to -55 mV, what occurs?

the all or nothing reaction occurs, and the nerve fires

At how many mV do the sodium channels close?

\

\+30 mV

What occurs at +30 mV?

all the sodium channels close but all the potassium channels open, letting all the potassium rush out, which makes it more positive than negative on the outside of the cell, called repolalarization

What is the process that occurs at +30 mV called?

repolarization

Depolarization definition:

loss of the difference in charge between the inside and outside of the plasma membrane, voltage becomes positive

Repolarization definition

a stage of an action potential in which the cell experiences a decrease of voltage due to the efflux of potassium (K+) ions along its electrochemical gradient.

When the voltage becomes very negative very rapidly, what is this called

hyperpolarization

Absolute refractory period:

occurs after hyperpolarizarion, no matter how much you stimulate this neuron it will not fire

Relative refractory period:

occurs after hyperpolarizarion, can fire based on if it reaches resting membrane potential

Is the sodium potassium pump always running?

yes

What does the sodium potassium pump require to run?

lots of ATP

Ion channels can be:

voltage-sensitive, ligand-gated, or mechanically-gated in nature.

chemically-gated or ligand-gated channels:

open when a chemical ligand such as a neurotransmitter binds to the protein

voltage-gated channels:

open and close in response to changes in membrane potential

mechanically-gated channels:

open in response to physical deformation of the receptor, as in sensory receptors of touch and pressure

How does a neuron elicit an action potential

* When an adequate stimulus triggers stimulus-gated Na+ channels to open, allowing Na+ to diffuse rapidly into the cell a local depolarization is produced
* As the threshold potential is reached, voltage-gated Na+ channels open and more Na+ enters the cell, causing further depolarization

Local potentials: another name for local potential

A slight shift away from the resting membrane in a specific region of the plasma membrane

\
graded potentials because the magnitude of deviation from the resting membrane potential is proportional to the magnitude of the stimulus

Excitation of the local potential

* Excitation: occurs when a stimulus triggers the opening of additional Na+ channels, allows the membrane potential to move toward zero (depolarization)

Inhibition of the local potential:

* Inhibitions: occur when a stimulus triggers the opening of additional K+ channels, increasing the membrane potential (hyperpolarization)

Excitatory neurotransmitter:

open up the sodium channels to start the depolarization of an action potential

positive reaction


1. excite the neuron and cause it to fire off the message, meaning, the message continues to be passed along to the next cell

Inhibitory neurotransmitter:

block or prevent the chemical message from being passed along any farther; prevents an action potential from being fired

What happens when you have an excitatory neurotransmitter in the synaptic cleft?

excite the neuron and cause it to fire off the message, meaning, the message continues to be passed along to the next cell

What effect would an excitatory neurotransmitter have on the postsynaptic membrane?

Neurotransmitters released at excitatory synapse cause the postsynaptic membrane to depolarize

How do we get rid of neurotransmitters

1. transported back into the synaptic knob (reuptake)
2. metabolized into inactive compounds by enzymes
3. diffused and taken up by nearby glia

The neurotransmitter's action is quickly terminated because:

the neurotransmitter molecules are either reuptaken, metabolized, or diffused

Converging circuit

more than one presynaptic axon synapses with one postsynaptic neuron

Diverging circuit

one presynaptic axon synapses with multiple postsynaptic neurons

Reverberating circuit

nerve impulses are continuous so the action potential never stops firing, and the action itself never stops (breathing is a reverberated action of the neuron)

Difference between neuronal axons in the CNS vs PNS

Oligodendrocytes (form myelin sheaths) in the CNS


Schwann Cells in PNS (form myelin sheaths)

Afferent portion of the neuron:

Afferent: dendrites of the perikaryon, going towards (sensory)

Efferent portion of the neuron:

Efferent: synaptic end, going away (motor)

part of the axon that stores and then releases neurotransmitters

synaptic vesicles in axon terminal

How does the axon store and release neurotransmitters

Neurotransmitters stored in synaptic vesicles located at the axon terminals


Released when synaptic vesicles fuse with neural membrane following influx of calcium ions

What triggers the storage vesicles to release neurotransmitters

* An action potential reaches a synaptic knob, causing calcium ions to diffuse into the knob rapidly
* The increased calcium concentration triggers the release of neurotransmitters by means of exocytosis
* Vesicle and membrane fuse, neurotransmitter is released into the synaptic cleft
* Neurotransmitter molecules diffuse across the the synaptic cleft and bind to receptor molecules, causing ion channels to open
* Opening of ion channels produces a postsynaptic potential, either an excitatory postsynaptic potential (EPSP) or an inhibitory postsynaptic potential (IPSP)

What does the vertebral foramina/spinal canal house

the spinal cord and its meninges

What are meninges

protective connective tissue layers

How many meninges are there

three meninges

What is the dura mater

strongest, dense, irregular connective tissue

What does the dura mater adhere to

the periosteum of cranial bones

Double layer of dura mater forms what

dural sinuses

How is the dura mater separated from the spinal cord

by the epidural space

Are cranial and spinal meninges continuous with each other

yes

How many extensions of the dura mater separate portions of the brain

3

What are the three extensions of the dura mater called

the falx cerebri, the falx cerebelli, and the tentorium cerebelli

What does the falx cerebri do

extension of dura mater; connective tissues that separate the left and right hemispheres of the brain;  a scythe-shaped band of dura mater that separates a part of the cerebral hemispheres. 

What does the falx cerebelli do

The falx cerebelli is a small infolding of the dura in the sagittal plane over the floor of the posterior cranial fossa. It partially separates the two cerebellar hemispheres 

What does tentorium cerebelli do

The tentorium cerebelli (or tentorium) separates the cerebrum from the cerebellum and brainstem.

Where are the dural sinuses

1. :: in the brain only

 What do the dural sinuses do

function as veins, collecting blood from brain tissues for return to the heart (delivers to internal jugular veins)

What is the superior sagittal sinus

one of several dural sinuses

What does the superior sagittal sinus do

carries waste and fluids away from the brain as veins do throughout the rest of the body.

Where is the subdural space found specifically

located between the dura mater and the arachnoid mater 

What is found in the subdural space

interstitial fluid

Where is the epidural space found

in the spinal cord only

Where is the epidural space found specifically

Located immediately outside the dura mater but inside the bony coverings of the spinal cord