FINAL EXAM Flashcards
Define Nissl body
well developed rough ER, involved in metabolic activity
Do primary brain tumors originate from NEURONS in the brain or the SUPPORTING CELLS?
Supporting cells (neuroglial cells). 1. neurons are amitotic and cannot divide 2. supporting cells are able to divide, and proliferate, causing tumor
Why are neurons amitotic?
they do not contain centrioles, which are needed for cells to divide
Describe the structural organization of a tract or nerve
(innermost –> outermost)
neuron –> endoneurium –> fascicle –> perineurium –> epineurium –> tract/nerve
define Endoneurium
connective tissue that covers each axon
Define tract
bundle of axons in the CNS
Name and describe the function of supporting cells IN THE CNS (4)
- astrocytes: involved in forming the blood-brain barrier
- microglia: clean cell debris
- ependymal cells: beat cilia to move cerebrospinal fluid (CSF)
- oligodendrocytes: myelinates axons
Name and describe the function of supporting cells IN THE PNS (2)
- Schwann cells: myelinate axons, contain neurilemma
- Satellite cells: act as chemical barrier
Which part of a neuron is known as the secretory region and why?
Axon terminals because they release neurotransmitters into extracellular space
define epineurium
connective tissue that covers the bundle of perineurium-covered fascicles
define nerve
bundle of axons in the PNS
Define ganglion
cluster of neuron cell bodies in the Peripheral Nervous System (PNS)
define perineurium
connective tissue that covers fascicle
Define nucleus
cluster of neuron cell bodies in the Central Nervous System (CNS)
Which part of a neuron is known as the conducting region and why?
Axon because it generates and transmits action potentials away from the cell body
Which part of a neuron is known as the receptive center and why?
Dendrites because they receive and convey electrical signals towards the cell body
How many axons can each neuron have?
Each neuron can only have one axon
Which part of a neuron is known as the biosynthetic center and why?
Cell body because all biosynthetic activities occur in the cell body
define Nodes of Ranvier
spaces between adjacent myelin shealths
define neurilemma
outermost nucleated cytoplasmic layer of schwann cells that surrounds the axon of the neuron
which type of supporting cells are involved in the formation of the Blood-Brain Barrier?
Astrocytes
What is the function of the Blood Brain Barrier
- prevents brain and nerve cells from contact with blood
- additional shock absorption and insulation
- provides nutrients and oxygen to the brain
explain why myelinated axons in the CNS do not regenerate when severed
they have no regeneration tube because neurilemma is not present. they are amitotic so they cannot replicate
explain why axsons in the PNS can regenerate when severed
axons in the PNS have regeneration tube formed by the neurilemma from the schwann cell and nuclei to replicate
why are impuses conducted faster in a larger myelinated axon and slower in a smaller unmyelinated axon?
- diameter of axon: larger axons transmit impulses faster because there is less resistance
- degree of myelination: myelinated axons transmit impulses faster because myelinated axons use saltatory conduction (faster) and unmyelinated axons use continous conduction (slower)
Describe the resting membrane potential
resting state with no movement, more Na+ ions outside, more K+ ions inside
describe the depolarization phase of an action potential
Na+ influx (enters the cell)
describe the repolarization phase of an action potential
K+ efflux (exits the cell), occurs after action potential is reached
describe the hyperpolarization phase of an action potential
more K+ efflux (exiting the cell) then return to Resting membrane potential
what is the absolute refractory period and the relative refractory period of an action potential?
- absolute refractory period: occurs when the sodium gates are still open (depolarization phase) and the neuron is unable to initiate a new action potential
- relative refractory period: occurs when the sodium gates are closed (repolarization phase) and a strong stimulus causes initiation of a new action potential
how does the body differ between a strong stimulus and a weak stimulous?
more frequent action potentials indicate a strong stimulus
less frequent action potentials indicate a weak stimulus
Name and describe the structural classes of neurons (3)
- Uni/psuedo polar: a single process extending from the cell body, divided into peripheral and central processes
- bipolar: two processes attached to the cell body (one dendrite, one axon); found only in eye, ear, and olfactory mucosa
- multipolar: many processes attached to the cell body (many dendrites, one axon)
which structural class of neurons is most abundant in the body?
multipolar
name and describe the functional classes of neurons (3)
- sensory (afferent) neurons: carry impulses toward the CNS
- motor (efferent) neurons: carry impulses away from the CNS
- association neurons (interneurons): conduct impulses within the CNS
which functional class of neurons is most abundant in the body?
association neurons (interneurons) make up 90% of the nerves in the body
name and describe the types of nerve fibers (3)
- group A: largest diameter, heavily myelinated; transmits impulses at 150 m/s
- group B: intermediate diameter, lightly myelinated; transmits impulses at 15 m/s
- group C: smallest diameter, unmyelinated; transmits impulses at 1 m/s
which type of nerve fiber has the fastest conduction? why?
Group A fibers because they have the largest diameter, which allows for the lowest resistance during conduction
which type of nerve fiber has the slowest conduction velocity? why?
Group C fibers, because they have the smallest diameter and thus the highest resistance during conduction
What happens to the conduction velocity when myelinated axons become demyelinated?
conduction velocity decreases because myelin insulate the axonal membrane which reduces the ability of current to leak out of the axon, thus increasing the distance along the axon that a current can flow
Name the structures protecting the brain (4)
Cranium, Meninges, Cerebral Spinal Fluid, Blood Brain Barrier
Name the types of meninges (3)
Outermost –> Innermost
- Dura Mater: double-layered, tough and inflexible
- Arachnoid mater
- Pia mater
List where Cerebral Spinal Fluid is located both inside and outside the brain
- Inside: two lateral ventricles (cerebral cortex), third (diencephalon) and fourth (pons + medulla oblongata) ventricle
- outside: subrarachnoid space
Where is the location of the interventricular foramen?
connects the paired (2) lateral ventricles with the third ventricle at the midline of the brain
give the location of the cerebral aqueduct
connects the third ventricle in to the fourth ventricle within the midbrain
What supporting cell lines the ventricles of the brain and what is its function?
ependymal cells, function is to circulate cerebrospinal fluid
What are the four regions of the brain
Cerebrum, Cerebellum, Diencephalon, Brainstem
Define gryus
the ridge (raised area) of wrinkled gray matter in the brain
define sulcus
the grooves between two gyri
define fissure
the deeper sulcus
define corpus callosum
the pathway for communication between the two hemispheres of the cerebral cortex, located deep within the cerebrum
define gray matter
The region of the brain with many cell bodies and dendrites
Define white matter
the region of the brain with many axons
define commissural tract
enables the two sides of the cerebrum to communicate with each other
define projection tract
transmit impulses from the cerebrum to parts of the lower brain and spinal cord
define association tract
connect areas of the cerebral cortex within the SAME hemisphere