Chapter 3 Flashcards
Golgi
thought the nervous system was composed of interconnected fibers
Ramon y Cajal
used the brain embryos of chicks and found that the nervous system is made up of discrete cells that become more complex with age
Cell body (soma):
core region of a cell containing the nucleus and other organelles for making proteins
Dendrites
branching extension that collect information from other cells
Axon
“root” or single fiber that carries messages to other neurons
Neurons
are plastic; most CNS neurons are never replaced throughout life
Dendritic spines
small protrusions from on a dendrite; point of contact with the axons of other cells
Axon hillock
where the axon begins; juncture of soma and axon where the action potential begins
Axon collaterals
branch of an axon
Teleodendria
small branches that may emerge from the lower tip of an axon
Terminal button
located at the end of teleodendrion; sits close to the dendritic spine; creates an “almost connection called a synapse
Synapse
information-transfer site between neurons
Sensory Neuron
brings information into the brain from sensory receptors; Types: bipolar, somatosensory
Interneurons (association cells)
associate sensory and motor activity in the CNS; branch extensively; Types: stellate, pyramidal, Purkinje
Motor Neurons
carry information out the brain and spinal cord to the body’s muscles; have long axons and cell bodies; located in the lower brainstem and spinal cord
Bipolar Neuron
Type of sensory neuron; found in the retina and contains one short dendrite and one short axon; transmit afferent sensory information from the retina’s light receptors to the neurons that carry information to the visual centers
Somatosensory Neuron
bring sensory information from the body into the spinal cord
Stellate Cell
type of interneuron; small with many dendrites extending around the cell body
Pyramidal Cell
type of interneuron; brings information from the cerebral cortex to the rest of the brain and spinal cord; has two dendrites and is pyramid shaped
Purkinje Cell
type of interneuron; fan shaped; carries information from the cerebellum to the rest of the brain and spinal cord
Relationship between sensory, interneurons and motor neurons
Sensory (collect afferent)→interneurons→ motor neurons (efferent creates behavior)
Action Potential
neurons fire only if its excitatory inputs exceed its inhibitory inputs.
Glial Cells
support cells; help neurons relay information by binding them together and providing them nutrients, support and protection; can replace themselves
Ependymal Cells
type of glial cell; located on the walls of ventricles; produce and secrete CSF
CSF
constantly being made; flows toward the base of the brain where it is absorbed into the blood vessels. Purpose: shock absorber, eliminates waste, assists in maintaining a constant temperature, source of nutrients for brain areas near ventricles
Hydrocephalus
the fourth ventricle can become fully or partly blocked and can restrict CSF flow causing a buildup of pressure that begins to expand the ventricles and push on the surrounding brain; can cause severe mental retardation
Brain tumors
grow from glial cells. Types: Gliomas (slow growing, not usually malignant if from astrocytes), Meningiomas (tumors usually encapsulated and can often be easily removed), Metastatic (transfer of tumor cells from one region to another, difficult to treat)
Astrocytes (astroglia)
type of glial cell; creates the blood-brain barrier; provide structural support within CNS–their extensions attach to blood vessels and the brain’s lining creating scaffolding that hold neurons in place; provide pathways for the movement of nutrients between blood vessels and neurons; secrete chemicals that keep neurons healthy and help them heal if injured; enhance brain activity by receiving signals from neurons when they pass on the blood vessels, which allow the blood vessels to expand to provide more fuel (oxygen and glucose)
Blood-Brain Barrier
protective partition between blood vessels and the brain; end feed of astrocytes attach to blood vessels and prevent an array of substances from entering the brain through the blood vessel walls; does not allow other (good) substances to enter either → difficult to treat brain infections
Microglia
type of glial cell; originate in the blood (immune system) and migrate throughout the nervous system; monitor health of brain tissue and play a role in its immune system; identify and attack foreign tissue; provide growth factors that aid in repair; they engulf foreign tissue and dead brain cells (called phagocytosis);
Phagocytosis
when microglia engulfs foreign tissue and dead brain cells
Olingodendroglia
Type of glial cell; myelinate axons in the brain and spinal cord; send out large, flat branches that enclose axons; contributes to the neurons’ nutrition and function by absorbing chemicals that the neuron releases and releasing chemicals that the neuron absorbs
Schwann Cells
Type of glial cell; myelinate axons in the PNS; wraps itself repeatedly around part of an axon; contributes to the neurons’ nutrition and function by absorbing chemicals that the neuron releases and releasing chemicals that the neuron absorbs
Myelin
insulation for axons; prevents adjacent neurons from short-circuiting
Multiple Sclerosis (MS)
myelin formed by oligodendroglia is damaged and the neurons’ functions become disrupted; the loss of patches of myelin leads to scaring aka plaque
Paralysis
cessation of both movement and sensation
PNS Glial Repair
when a PNS axon is cut it does and returns to the cell body. Microglia remove debris from dying axon, Schwann cells (provide its myelin) shrink and divide forming numerous small glial cells that are along the path the axon used to take. The neuron sends out axon sprouts that search for the path and then follow it. Schwann cells envelop the new axon, forming new myelin and restoring function