exam 1b Flashcards
Parts of a neuron
axon, myelin sheath, button terminals, Nodes of Ranvier, dendrites, nucleus, and cell body (soma)
Soma
cell body
metabolic center of the neuron
contains:
nucleus of the cell
neurotransmitter-synthesizing mechanisms
energy producing and storing structures
dendrites
input unit
branchlike extensions that receive information from other neurons
axon
output unit
extends from cell bodied to target cells and transmits information to other cells
vary from 1 meter to a few centimeters
axon hillock
small bump between axon and cell body where axon originates
oligodendrocytes
myelinates axons in the central nervous system
Schwann cells
myelinates axons in the peripheral nervous system
Pre-synaptic terminals
fingerlike projections at the end of axon
belongs to the neuron transmitting information
Post-synaptic terminal
area on dendrite, cell body, or axon which receives the signal transmitted from pre-synaptic terminal
synaptic cleft
space between two terminals
neurotransmitters
chemical compounds that transfer information about its activity
what is the only direction information can be transferred in?
pre-synaptic terminal to post-synaptic terminal
Nodes of Ranvier
spaces in the myelin sheath not covered by a fatty substance
important for saltatory conduction and aid in speed of signal transmission
How do Nodes and Ranvier aid in speed?
signal jumps over myelinated areas like leapfrog rather than flowing down length of axon
Action potential
ALL or NONE Principle: either the stimulus is strong enough or not to result in action potential
Excitatory Post-Synaptic Potential
EPSP
positive charges that cause the next neuron to move towards the action potential
Inhibitory Post-Synaptic Potential
IPSP
negative charges that cause next neuron to move away from action potential
Absolute Refractory period
period immediately following an action potential during which a neuron cannot fire another action potential, regardless of stimulus strength
time of firing levels to 1/3 of the way through repolarizing
Relative Refractory Period
period following an action potential during which a neuron can fire an action potential, but requires a stronger stimulus than usual
last 2/3 of rest of the potential
Temporal Summation
positive charges building up over time, resulting in an action potential
Spatial Summation
occurs when positive charges keep coming in over and over
Describe an action potential
-Resting potential: -60 mV
-Stimulus causes cell to reduce negativity (move in positive direction) to -50 or -45 mV
-At the threshold for a cell to fire (-50), receptor proteins open and sodium rushes in (sodium is positively charged) DEPOLARIZATION
-Depolarization continues until cell crosses 0
-At peak (35 to 40 mV) cell pumps out potassium and begins to move in a negative direction REPOLARIZATION
hyperpolarization
state in which it is hard for a cell to fire
results in absolute refractory and relative refractory periods
consequences of positive and negative charges
positive charges cause resting potential to increase and can cause action potential
negative charges cause resting potential to decrease and do nothing regarding action potentials
relationship between strength of stimulus and latency
stronger stimulus - shorter latency
sensory nervous system
vision
hearing
touch
smell
measuring sensitivity in sensory nervous system
level of sensitivity is based on how many nerve fibers are affected
motor nervous system
causes muscles to assume various degrees of contraction
ration of nerve and muscle best for fine motor movement (innervation ratio)
low nerve to muscle ratio
1 to 1 is better than 1 to 100
What are the three layers of the meninges?
Dura Mater
Arachnoid Mater
Pia Mater
Dura Mater
outermost layer, thick and non elastic
made of two united layers
has two folds of tissue that protect brain from displacement:
falx cerebri
ternorium cerebelli
subdural space
space below dura filled with cerebrospinal fluid (CSF)
Arachnoid Mater
inferior to subdural space
bridges the sulci and projects into venous sinuses to form arachnoid villi- important for uptake of CSF into bloodstream
subarachnoid space
below arachnoid mater and filled with CSF
important because all cerebral arteries, veins, and cranial nerves pass through this space
Pia Mater
closely adheres to surface of the brain (cannot be removed without destroying cerebral cortex)
bridges gyri and extends down to sulci
What are the ventricles?
Lateral Ventricles
Third Ventricle
Fourth Ventricle
Lateral Ventricles
paired structures, but considered as one
C-shaped
choroid plexus located on medial aspect
Name and locations of the division of the Lateral Ventricle
Body: parietal lobe
Anterior horn: frontal lobe
Posterior horn: occipital lobe
inferior horn: temporal lobe
Third Ventricle
located between thalamis
small slit that is connected to lateral ventricle by foramen of Munro and to fourth ventricle by aqueduct of Sylvius
chiroid plexus located on roof of ventricle
Fourth Ventricle
anterior to cerebellum and posterior to pons & upper half of medulla
continuous with cerebral aqueduct and central canal
chiroid plexus is T shaped
Four parts of Fourth ventricle
roof
walls (2)
floor
Major foreamen of Fourth ventricle
lateral formina of Luschka
foreamen of Magendie
empties CSF into subarachnoid space
Major function of ventricles
To provide circulation of CSF
buildup of CSF- hydrocephalus
ependyma
membrane that lines the ventricles to form chiroid plexus - produces CSF
Cerebral spinal fluid
colorless fluid that protects brain and spinal cords by separating them from bones
functions:
protection
provide nourishment to nervous tissue
regulate intracranial pressure
pressure can be measured for diagnostic purposes
Divisions of the Brain
Hindbrain
Midbrain
Forebrain
Hindbrain
Rhombencephalon
lowest level of the brain
two subdivisions:
Afterbrain
Marrowbrain
Afterbrain
Metencephalon
Subdivision of Hindbrain
includes pons and cerebellum
Marrowbrain
Myelencephalon
subdivision of Hindbrain
consists of medulla oblongota
Medulla
smallest part of the brain
location where some cranial nerves enter and exit
attaches to spinal cords in higher areas
Midbrain
Mesencephalon
consists only of midbrain
highest part of brainSTEM with some connections leaving midbrain
Forebrain
Prosencephalon
highest part of the brain
consists of endbrain and interbrain
Endbrain
Telencephalon
made of cerebral hemispheres and basal ganglia (crucial for motor control and higher cognitive function)
Interbrain
Diencephalon
consists of thalamus and hypothalamus
thalamus
first stop for all sensory information (besides olfaction)and first area with connections to arousal
hypothalamus
important for basic functions (body temp. and hunger)
regulates sensation
Major arteries of the brain
vertebral
internal carotid
communicating
Vertebral arteries
form basilar artery at base of pons which splits to form posterior cerebral arteries - supply posterior temporal lobe and occipital lobe
Internal Carotid Arteries
anterior cerebral artery: supplies medial aspects
middle cerebral artery: supplies lateral aspects
communicating arteries
important incase of blockages
posterior: attaches front and back arteries
anterior: attaches left and right arteries
Circle of Willis
system of arteries
defense mechanism to provide blood flow is blockage occurs
Cranial nerves
12 pairs (24 total)
Cranial nerve I
Olfactory
sensory
smell
Cranial nerve II
Optic
sensory
sight
Cranial nerve III
Oculomotor
motor
eye movement
Cranial nerve IV
trochlear
motor
movement for 1 eye muscle
Cranial nerve V
trigeminal
both sensory and motor
S: face and mouth
M: chewing and soft palate
Cranial nerve VI
abducens
motor
moving eyes outward
Cranial nerve VII
facial
both sensory and motor
S: tongue and outer ear
M: facial expression
Cranial nerve VIII
auditory/vestibular
sensory
hearing and balance
Cranial nerve IX
glossopharyngeal
both sensory and motor
S: tongue and tympanic membrane
M: sylophayngous - important for swallowing and speech)
Cranial nerve X
vagus
both sensory and motor
S: lower pharynx and inner larynx
M: pharynx and larynx muscles
Cranial nerve XI
spinal accessory
motor
soft palate, larynx, and neck muscles
Cranial nerve XII
hypoglossal
motor
tongue movement/tongue control
plasticity
ability to rebound after brain damage
decreases with age
theory of equipotentiality
any neural tissue can subserve any function (can process any type of information within reason)
