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what is temporal summation
one neuron fires rapidly to reach threshold
one, two, three, four impulses and you reach threshold and action potential occurs
what is spatial summation
different neurons fire at the same time to reach action potential
both subthreshold, but together reach threshold and action potential occurs
central nervous system neuroglial cells
astrocytes
microglia
ependymal cells
oligodendrocytes
peripheral nervous system neuroglial cells
satellite cells
schwann cells
astrocytes
most abundant and versatile
most highly branched which are used to reach out and grab onto neurons and capillaries and regulate their permeability to things
provide framework for developing neurons to navigate and form synapses
important in developmental years
microglia
small with thorny processes which contact nearby neurons and monitor health and status
damaged neurons stimulate microglia to phagocytose the damaged neurons
resident immune cell of central nervous system
ependymal cells
line ventricles of brain
vary in shape and size, but usually cuboidal and have cilia
helps make cerebrospinal fluid and acts as a filtration system and cilia circulates cerebrospinal fluid
oligodendrocytes
creates myelin sheath
reaches out and wraps around axon of neuron
can reach out to multiple spots
satellite cells
equivalent to astrocytes, but in peripheral nervous system
wraps around cell body of neuron
schwann cells
equivalent to oligodendrocytes, but in peripheral nervous system
forms myelin sheath of PNS but in 1 spot, 100s of these form myelin sheath of an axon
multipolar neurons
most abundant in the body
sends info from the brain out to the body (efferent)
many processes off cell body
bipolar neurons
2 processes off cell body → one dendrite and one axon
very rare → only in eye and ear
info goes from body to brain (Afferent)
unipolar neurons
one process off cell body that splits into peripheral and central processes
sensory neurons → goes to spinal cord and creates a response before it is sent to the brain (knee jerk reaction)
what is threshold
critical voltage needed to excite a neuron
point of no return → action potential will occur
what is depolarization
membrane potential moves towards 0 mv
less negative or if RMP is above 0 it is more positive
changed membrane potential to be less negative
what channels are open during depolarization
activation gate is open → allows sodium ions in
inactivation gate closes
what is hyperpolarization
membrane potential increases
exceeds resting state (more negative)
harder to excite because more negative → less likely to generate an action potential → less likely to exocytose a neurotransmitter
what channels are open during hyperpolarization
some potassium channels remain open
sodium channels close
what is repolarization
membrane potential returns towards a resting state
return cell to resting membrane potential → make it more negative
what channels are open during repolarization
potassium channels open
activation gate close
inactivation gates open
what is the receptor regions job and where is it
receives signals from other neurons
chemically gated receptor channels
located at cell body and dendrites or distal end of peripheral process in unipolar neuron
what is the trigger zones job, where is it, and what does it contain
responds and creates an action potential
usually located at the axon hillock (junction of the axon and cell body)
area with chemically regulated gates and the area with voltage regulated gates → they meet here
conducting region
where action potential takes place
axon
secretory region where is it, what is in it and what does it do
region where neurotransmitter or chemical are released into synapse
axon terminal
contains neurotransmitter or chemical that neuron releases
what is the cause of an action potential
voltage gated sodium channels open and local currents depolarize membrane
what is the process of an action potential
sodium rushes in depolarizing membrane, reaches threshold around between -55 and -50 mv, depolarization becomes self generating, membrane continues to depolarize until all sodium channels are open → overshoots to 30 mvs (rising phase of action potential), lasts about 1 ms, self-limiting, sodium channels causing sodium to rush out of the cell and neuron is restored
what is the effect of an action potential
as action potential travels down the neuron and opens calcium channels to allow neurotransmitter to exocytose out of neuron
what is an action potential
when membrane potential rises and falls
rapid sequence of changes in the voltage across a membrane
how does an action potential travel
down the axon to the axon terminal
by changing which channels are open allowing sodium to rush into the neuron
what happens if sodium channels are open
depolarization
what happens if sodium channels are closed
repolarization
what happens if potassium channels are open
repolarization
what happens if potassium channels are closed
depolarization
acetylcholine in CNS is an…
excitatory neurotransmitter → causes depolarization
acetylcholine in PNS is an…
excitatory neurotransmitter → causes depolarization
OR
inhibitory neurotransmitter → causes hyperpolarization
glutamate is the…
primary excitatory neurotransmitter in the CNS → causes depolarization
glycine is the…
major inhibitory neurotransmitter of spinal cord → causes hyperpolarization
GABA is the…
major inhibitory neurotransmitter of the brain → causes hyperpolarization
hyperpolarization makes the cell
more negative
depolarization makes the cell
less negative
types of tracts
association
commissural
projection
association fibers
run between areas in the same hemisphere
example of association fibers
cingulum bundle
commissural fibers
connect the 2 hemispheres
example of commissural fibers
corpus collosum
projection fibers
going to lower area of brain or leaving brain and going to spinal cord
some of the longest fiber tracts in the body
projection fibers examples
visual pathways and cortico-spinal or pyramidal tract
where is the prefrontal cortex
in frontal lobe
what does the prefrontal cortex control
intellect, learning and executive functions - some personality
where is the primary motor cortex
in frontal lobe
what does the primary motor cortex do
allows us to produce skilled voluntary movement
where is the somatosensory cortex
in parietal lobe, posterior to central sulcus
what does the somatosensory cortex do
receives sensory input from all sensory areas in brain and filters things out to allow brain to work more efficiently; spatial awareness is formed here
where is the hypothalamus
deep within the brain
what does the hypothalamus do
main link between endocrine and nervous systems
autonomic control center
controls thermoregulation, nutrition and hydration, biological rhythms, and endocrine function
where is the hippocampus
temporal lobe
what does the hippocampus do
codes memory, but does not store them
codes them for storage by putting them into semantic or episodic categories
what does the diencephalon do
coordinates with endocrine system to release hormones, regulate sleep-wake cycles, and relay sensory and motor signals
what is the diencephalon split into
hypothalamus
thalamus
epithalamus
where is the diencephalon located
centrally located in brain sitting on top of brain stem above midbrain and under cerebrum
parts of the brain stem
midbrain
pons
medulla
where is the midbrain
topmost part of the brain stem
what does the midbrain do
processes visual and auditory signals
where is the pons
between midbrain and medulla
contains cranial nerves 5,6, and 7
what does the pons do
handles unconscious processes like sleep-wake cycle and breathing
where is the medulla
lowest portion of brain stem, below pons
what does the medulla do
controls heartbeat, breathing and blood pressure
key role in nerve signals to and from body to brain
what does association have to do with memory
ability to transfer something from short to long term memory is better when you associate it with something you already know
what is short-term memory
temporary holding of information
limited to 7-12 pieces of info for around 3-5 minutes
where does short-term memory take place
in the hippocampus and prefrontal cortex
what is long-term memory
has limitless capacity
remembered for a long time
where are long-term memories stored
in the cortex’s
where is the primary motor cortex located
frontal lobe
where is the premotor cortex located
just anterior to primary motor cortex
in frontal lobe
where is Broca’s area located
just anterior and inferior to motor cortex
typically in left hemisphere but sometimes in lefties can be found in right hemisphere
where is the primary somatosensory cortex located
in parietal lobe
posterior to central sulcus
where is the somatosensory association area located
just posterior to primary somatosensory cortex
in parietal lobe
where is the primary visual cortex located
occipital lobe
most posterior part of cerebellum
where is the visual association area located
occipital lobe
where is the primary auditory cortex located
just under primary somatosensory cortex
temporal lobe
where is the auditory association cortex located
temporal lobe
where is the olfactory cortex located
internalized area of temporal lobe
where is the gustatory cortex located
temporal lobe
where is the visceral sensory area located
occipital lobe
what is multiple sclerosis
disruption or loss of myelin sheath in CNS
autoimmune disease → own cells mistake nerve fibers of CNS for invaders and attacks them
symptoms of multiple sclerosis
signals delayed or weaker
loss of vision, numbness
what is Alzheimer’s disease
degeneration of the brain
abnormal protein accumulation
neurodegeneration
symptoms of Alzheimer’s disease
memory impairment, difficulty concentrating, problems finishing daily tasks, confusion with passage of time
underlying causes of Alzheimer’s disease
age, family history, head injury, cardiovascular disease
what is parkinson’s disease
degeneration of dopaminergic neurons of the substatia nigra (midbrain, but part of the basal ganglia)
loss of dopamine producing neurons in the brain
symptoms of parkinson’s disease
tremors, muscle stiffness, slow movement, impaired balance
underlying causes of parkinson’s disease
blend of genetics and environmental and unknown causes
what is a concussion
traumatic brain injury
bump, blow, or jolt to head causing brain to hit skull
symptoms of concussion
loss of consciousness, sensitivity to light, headache, confusion, vomiting
fissures
deep sulci
gyri
ridges, bumps on top of brain
sulci
more shallow groove
gray matter
more outside, over cerebellum, neuron cell bodies
white matter
more inside, connects parts of brain, mostly myelinated axons
ventricle
hollow, fluid filled space
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