Chapter 1: Nerve Cells Flashcards
What is a Neuron?
Neurons are highly specialized cells that possess electrical excitability and function to process and transmit cellular signals.
Neurons receive information and transmit it to other cells
What does the shape of a neuron determine?
It’s connection with other neurons and its contribution to the nervous system
What do neurons vary in?
Size, shape and function
What are Purkinje cells?
Cells that carry info primarily about body movement
How are Purkinje cells arranged?
They are aligned like dominos forming a 2-D grid.
What do Purkinje cells do?
Cell output permits comparison of ongoing movement and sensory feedback derived from it.
Thus, generates an error correction signal that can modify movements already begun
What do Glial cells do?
They provide support and protection for neurons by
- Surround
- Hold in place
-Supply nutrients and oxygen
-Insulate
-Form myelin
-destroy and remove decay and debris
-clearance of neurotransmitters
-crucial to development (synaptic plasticity and genesis)
What is the ratio of glial cells to neurons in cerebral gray matter?
3 glial cells to every 2 neurons
Otherwise its a 1:1 ratio
What do astrocytes do?
Astrocytes synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals released by the axon
By surrounding a connection between neurons, an astrocytes shields it from chemically circulating around.
Also, by taking up ions and transmitters and then releasing them back, an astrocyte helps synchronize, close neurons, enabling them to send messages in waves.
They are important for rhythm — like your breathing
Astrocytes also dilate blood vessels to bring nutrients to the brain.
What do microglia do?
Remove waste material and other microorganisms that may be harmful to the neuron
They act as part of the immune system removing viruses and fungi from the brain
After brain damage they proliferate, removing damaged and dead neurons
They also contribute to learning by removing the weakest synapses
What do oligodendrocytes (cns) and Schwann cells (pns) do?
Build the myelin sheath that surrounds vertebrate axons of the brain and spinal cord
They also supply the axon with nurture to necessary for proper functioning
Radial glia
Guide the migration of neurons and the growth of axons and dendrites during embryonic development
They differentiate into neurons after
What did Camilo Golgi invent?
The procedure of staining Neuronal cells using silver chromate fixed to the neuronal membrane
What did Santiago Ramon y Cajal discover?
Used Golgis cell staining technique to demonstrate that the individual cells comprising the nervous system remained separate but connected to each other by small zones later called synapses
The theory was called the neuron doctrine
When did golgi and cajal receive a nobel prize?
In 1906 for their studies of the structure of the nervous system
Ironically Golgi defended the theory that nerve cells are merged during his speech
What’s different about Neurons versus other cells
Neuronal cells are similar to other cells of the body, but have a distinctive shape
What is a dendrite?
Sensory branching fibers lined with synaptic receptors responsible for bringing in info from other neurons
What is the soma?
The cell body contains the nucleus, mitochondria, ribosomes and other structures found in other cells
Axon
(Motor) Thin fiber of a neuron responsible for transmitting neural impulses away to other neurons, glands, or muscles (myelin sheath, nodes or rancher, terminal buttons)
What are dendrites connected to?
Dendrites are connected to the soma (Cell body)
Why is white matter white?
Axons are myelinated and therefore appear white.
Cell bodies are not myelinated and therefore appear grey matter
What are dendritic spines?
The bumps on dendrites which allow for more precision of functionality with more surface area
Ex> what if one person put there hand on you to get your attention versus whole class
Where are nerves located?
In the peripheral nervous system
Where are tracts located?
Tracts are in the central nervous system
Why do dendritic spines hello?
Dendrites surface are lined with specialized synaptic receptors which receive info from other neurons more surface area means more info is passed
Who’s is Louis Ranvier?
Louis Ranvier is a histologies and pathologist who discovered nodes or gaps in the myelin sheath; linked with saltatory conduction (propagation of the neural impulse)
Do invertebrates have myelin?
No
What are interruptions in the myelin known as?
Nodes of ranvier
What happens in multiple sclerosis?
In multiple sclerosis the myelin sheath, which is a protective membrane that wraps around the axon of a neuron is destroyed with inflammation and scarring
There is an autoimmune system attack on oligodendrytes so then myelin is destroyed in that region
What is a motor neuron
A motor neuron has its soma in the spinal cord and receives excitation from other neurons and conducts impulses along the axon to a muscle
Receives excitation through the dendrites
What is a sensory neuron?
A sensory neuron is specialized at one end to be highly sensitive to a particular type of stimulation
What does efferent mean?
Carries information from a structure
Afferent
Brings information to a structure
What are interneurons or intrinsic neurons
Are those whose dendrites and axons are completely contained within a structure
Keep in mind they are shorted because they are contained
What are the meninges?
It is made up of the dura mater, the arachnoid layer, and the pia matter
It’s function is as a protective covering on the central nervous system
Where does SAS flow from?
SAS flows from subarachnoid space back into the bloodstream
What does the brain need in continuous supply?
The brain needs a continuous source of blood because there is no place in the brain to store energy
Oxygen and glucose are also needed
What is the circle of Willis?
Internal carotid arteries and vertebral, base of shape allows for four potential sources of blood for the brain
What is the blood brain barrier?
It is a structure that surrounds the brain and functions to block most non-toxic and toxic chemical substances from entering.
The tight endothelial cells of the blood vessels and the glial cells combine together to serve in this capacity
What causes cerebral edema?
Brain swells up because of an opening at the endothelial junction allowing molecules that don’t normally pass into the brain
What do endothelial cells do
Endothelial cells come together at junctions, the diameter of that junction determines what molecules can pass
What happens when a virus invades a cell?
Mechanisms within the cell exude the virus particles through the membrane so that the immune system can find them
When the immune system discovered the virus they kill it as well as the cell that contains it
Basically, a cell exposes the virus through its membrane is saying look immune system I am infected kill me to save others
This does not work in places that do not replace cells like the brain
Overview of blood brain barrier
- single layer of glial cell that line blood vessel
- keep toxins out
- allows small fat-soluble molecules of proper electrical affinity to pass
What molecules can/can’t pass through the blood brain barrier?
Most large molecules and electrically charged molecules can not cross from the blood to the brain
A few small, uncharged molecules such as 02 and c02 cross easily
Certain fat-soluble molecules also cross (eg. vitamins, psychoactive meds)
Active transport systems pump glucose and amino acids across the membrane (requires energy)
Why does the blood brain barrier depend on endothelial cells?
Endothelial cells form the walls of the capillaries
Outside the brain cells are separated by small gaps bu in the brain they are very tightly constructed to prevent viruses, bacteria and harmful chemicals
This doesn’t happen in other organs because it can also prevent good chemicals from passing
Where is CSF located?
In the ventricles
What is the Choroids plexus?
The choroid plexus lines the ventricles and produces a filtrate of the blood called cerebrospinal fluid
What flows through ventricles and in what order?
Heavily infiltrated by blood vessels, everything but csf is filtered out
It flows from lateral ventricles to third than fourth, going downstream
Flow of CSF
The CSF circulates through the ventricles and within the arachnoid layer, exiting through the arachnoid granulations back to venous blood
How much does the brain weigh?
The brain weighs 1400 grams but its effective weight is 80 grams due to the buoyancy effect of the CSF
