Exam 4 Flashcards
Central Nervous System
brain (97% of nervous tissue) and spinal cord
Grey Matter (nuclei)
groups of neuronal cell bodies in the CNS
White Matter (tracts or fibers)
the bundles of axons which are myelinated in the CNS
Ganglia
groups of neuronal cell bodies in the PNS
Nerves
the bundles of axons in the PNS
How is the brain protected?
skin, cranial bones, cranial meninges, cerebrospinal fluid (made from plasma)
What are the cranial meninges?
dura mater (thick fibrous), arachnoid (thin fibrous and filamentous mesh), pia mater (thin fibrous)
Sinus
a special type of vein that does not contain smooth muscle in it
What happens in the subarachnoid space?
the cerebrospinal fluid circulates there
The purpose of cerebrospinal fluid (CSF)
homeostatic regulation of ions and nutrients, support, immune functions
Where is CSF produced?
First produced in lateral ventricles then flow through the interventricular foramen into the third ventricle producing more CSF which flows through the cerebral aqueduct into the fourth ventricle. From here the fluid can exit and flow around the brain or some of it will exit and flow to the spinal cord
How do we drain CSF?
The fluid is in the subarachnoid space where there is a good amount of pressure from the constantly created CSF that creates bulk flow and some of the CSF will drain into the dural space into the dural sinuses and the CSF will become part of the blood
Choroid plexus
the majority of the CSF is produced here, lining in the ventricles, tight junctions between internal capillaries and ependymal cells create a selective gradient that allows specific ions
How do plasma and CSF differ?
CSF has higher concentration of water and lower concentration of protein, high concentrations of sodium which make depolarization happen more rapidly
Blood brain barrier
endothelial cells with microvessels, exhibit complex tight junctions, everything must go through the barrier to get from plasma to CSF, contain parasites which integrate and process signals to help regulate the flow of nutrients and waste through the network of cells, contain astrocytes that help promote the tight junctions formation in the specialized neuroglia that extend to number of capillaries
What is the neurovascular unit and their function?
endothelium, astrocytes and parasites which controls molecular traffic to keep out toxins, creating ion homeostasis, creating low protein environment in the CSF
How do we create energy within the brain?
Consume lots of oxygen which passes freely across the blood brain barrier and the brain consumes about 15% of blood pumped by heart at rest, consumes lot of glucose which is about half of the body, membrane transporters move glucose from plasma into brain interstitial fluid
What happens if there is a lack of glucose in the brain?
progressive hypoglycemia that leads to confusion, unconscious and progressive unconsciousness and potentially death
What parts of the brain supply the blood?
internal carotid arteries - supplies anterior parts of brain, vertebral artery - supplies posterior parts of brain
Circle of Willis
a circle that provides redundant blood supply and prevent irreversible damage
How does the blood return?
Venous return happen through jugular veins
Cerebrum
highly folded, higher level thinking, responsible for conscious, motor control, and sensory perception
Diencephalon
responsible for homeostatic controls, smooth muscle control, temperature regulation
Function of brainstem
responsible for autonomic/reflex center (breathing or cardiac rhythm)
Cerebellum
responsible for coordination of movement, receives proprioception information, modulates thalamus and other nuclei
Gyrus/Gyri
ridges of the cerebrum
Sulcus/Sulci
the depressions in between the ridges of the cerebrum
Why is the brain organized in folds?
This is because we are limited in size by the pelvis cavity since we are bipedal and the volume and surface area can be increased by folds
Longitudinal Fissure
divides into 2 cerebral hemispheres
Transverse fissure
cuts into cerebrum and cerebellum
Lateral Fissure
separates the temporal lobe from the frontal and parietal lobes
Central Sulcus
separates the frontal lobe and the parietal lobe
Contralateral control
cerebral hemispheres control opposite side of body
Frontal lobe
motor control, speech, memory formation, personality, emotion, formally deemed where all the higher level thinking occurs - “seat of intelligence”
Parietal lobe
involved in sensation and sensory integration, spatial awareness and perception
Occipital lobe
visual processing and storing visual memories
Temporal lobe
hearing, speech and language, and smell
What is the grey matter in the cerebrum called?
cerebral cortex and the deeper parts are called basal nuclei
What are the white matters in the cerebrum called?
commissural fibers - connect hemispheres (corpus collosum), projection fibers - connects cerebrum to other regions (projection fibers of internal capsule), association fibers - connections within cerebral hemispheres (fornix)
Broca’s area
production of speech, in frontal lobe, in most people it is only on left side
Primary motor cortex
the ridge which is located anterior to the central sulcus and allows body parts to move
Olfactory bulb
involved in our perception of smell
Primary somatosensory cortex
in parental lobe, when there is a feeling, it is sent here contralaterally so the person will become aware of that stimulus
Somatosensory association cortex
located posteriorly in parietal lobe is responsible for processing that information
Homunculus
a visual representation of the real estate that are devoted to control or sensation over a particular region of our bodies
Primary auditory cortex
located on edge of temporal lobe, first receive any sounds that we hear and become conscious of them
Wernicke’s area
surrounds the primary auditory cortex and is responsible for language comprehension
Primary visual cortex
located in occipital lobe, first become aware of information coming from the optic nerves (2D sketch)
Visual association area
interprets information from the primary visual cortex
Basal Nuclei
function in modulating motor movements, work with precentral gyrus and cerebellum, semiautomatic motions and subconscious control
What the names of the three basal nuclei?
Caudate nucleus, putamen, globus pallidus
What are the areas of the diencephalon?
epithalamus - posterior, thalamus - superior, hypothalamus - inferior/anterior
Pineal gland
secretes melatonin, a hormone that helps regulate circadian rhythm
Thalamus
role in sensory information, synapse here, “switchboard” - allows us to not be conscious of every single sensory
Hypothalamus
regulates many homeostatic mechanisms throughout the entire body: autonomic nervous system, endocrine system, body temperature, emotional behavior, food and water intake, and circadian rhythms
Brainstem
bidirectional passageway for all tracts extending between the cerebrum and the spinal cord, houses nuclei of many of the cranial nerves, contain many autonomic centers and reflex center required for survival which are midbrain, pons, and medulla
Midbrain
cerebral peduncles - descending motor information, corpora quadrigemina - superior colliculi (visual reflexes), inferior colliculi (auditory reflexes)
Pons
respiratory centers and cranial nerve nuclei
Medulla
respiratory regulation, crane nerve nuclei, pyramids - anterior, tracts of descending motor information
Functions of cerebellum
adjust the postural muscles of the body, error correcting during movement, complex motor learning, and automating and optimizing behavior
Limbic System
known as emotional brain, not one localized region, behavior related to memory, hormones, autonomic nervous system, eating habits, smell, and other sensory information
Structures involved in the limbic system
Hypothalamus, thalamus, amygdala, and hippocampus
Amygdala
emotion
What is the point of the limbic system?
There is a strong link between emotion and memory. There is another strong link between hypothalamus and emotion
Spinal cord
similar to the brain as in surrounded by three meninges and has CSF, but white matter is superficial while grey matter is deep since myelinated parts need to located on the outside
Spinal nerves
bundles of axons in PNS
Grey matter anatomy in spinal cord
in a butterfly shape, can be divided into posterior gray horns (sensory information) and anterior gray horns (motor information)
Sensory nervous system
nervous system division that consists of sensory receptors, neurons, and the parts of the brain that receive and assign meaning to information
Sensation
due to receptors transfusing different stimuli into nerve impulse that are conducted into CNS
Perception
assigns meaning to that information within the brain
General sensation
touch, pressure, temperature, pain
Special sense
vision, olfaction, hearing, gustation
Functional sensory receptors
receptors can be classified based upon their adequate stimulus which are thermoreceptors (temperature), mechanoreceptors (stretch), nociceptors (pain), photoreceptors (light), chemoreceptors (chemicals)
What does using mouthwash mean?
A stimulus of a cool mint could stimulate a thermoreceptor and in response our perception is the modality of the receptor so we experienced a cooling feeling even though out actual temperature was not changed
Location sensory receptors
exteroceptors - external environment, interoceptors - internal environment, proprioceptors - give information about body position in space and relative to one another
What happens during the twisties?
loss of proprioception due to stress or aging
Structural sensory receptors
free - pain, temperature, smell, encapsulated - pressure, touch, rods and cones - sight, hair cells - hearing equilibrium
Sensory unit
a neuron and all of its receptors
Receptive field
the area/region that can be sensed by a sensory unit
Receptor potential
stimulus intensities is encoded in an EPSP where it needs to reach a threshold to generate an action potential
Temporal summation
once threshold is reached, action potentials are rapidly sent which increase the amount of exocytosis of neurotransmitters sent to CNS
Spatial summation
many neurons all at the same time are producing a lot of neurotransmitters and increasing the perception of intensity
Recruitment
stronger stimuli might call in additional afferent sensory neurons
Sensory adaptation
desensitization to repeated/prolonged stimuli by tonic receptors or phasic receptors
Phasic receptors
known as rapidly adapting receptors, prolonged stimulus causes action potentials to be fired initially but the same stimuli over time causes the stop of initiating action potentials and stop perceiving the sensation
Tonic receptors
known as slowly adapting receptors, slowing down the number of action potentials sent over time but there will still be a continued transduction of that signal
What aids in sensory discrimination?
receptors field are unevenly distributed throughout the body, overlap of receptive field
Fovea
the point on the eye where we try to bend light to focus in our vision, highest receptor density specifically of photoreceptors known as cones, low light causes us difficulty in discriminating colors
What is the relationship between size of receptor field and ability to discriminate between 2 points throughout the body?
inverse
Lateral inhibition
sharpens contrast in the pattern of action potentials received by the CNS allowing a finer resolution of stimulus location
Axo-axonic synapse
two axon terminals communicating with each other
Presynaptic inhibition
inhibition through neighboring spinal cord neurons, blocking the presynaptic neuron from sending its neurotransmitters to the postsynaptic neuron
GABA
inhibitory neurotransmitter that inactivates the calcium channels on the axon terminal of the next neuron
Three neurons of a sensory pathway
first order neuron (peripheral tissue to CNS), second order neuron (decussation), third order neuron (cell body in thalamus, synapses in the somatosensory cortex)
What is the dorsal column pathway for?
fine touch and proprioception
First order neuron in dorsal column pathway
peripheral tissue through spinal cord, terminates in medulla, lower body uses fasciculus gracilis and upper body uses fasciculus cuneatus
Second order neuron in dorsal column pathway
decussation in medulla and terminates in thalamus
Third order neuron in dorsal column pathway
cell body in thalamus and synapse in somatosensory cortex
What is the spinothalamic pathway for?
pain and temperature
First order neuron in spinothalamic pathway
peripheral tissue to posterior grey horn
Second order neuron in spinothalamic pathway
decussation in the spinal cord on same level as where it synapsed then terminates in the thalamus, upper body uses anterior spinothalamic tract while lower body uses lateral spinothalamic tract
Third order neuron in spinothalamic pathway
cell body in the thalamus and then synapses in the somatosensory cortex
Layers of the eye
Outer fibrous layer - sclera (white of eye) and cornea (most superficial layer with tough connective tissue), intermediate vascular layer - iris (gives eyes color, allow light to come) and choroid (stems from optic artery, nourishment), deep nervous layer - retina (contains photoreceptors)
Path of light
light bends in cornea then aqueous humor then crosses through the pupil and bends particularly around the lens, passes through more fluid that bends the light and hold the retina in place known as vitreous humor, then most of the light is focused on the fovea
What are the focal disorders?
myopia and hyperopia
Myopia
focal point anterior to fovea or the eye is too long so near-sightedness, glasses would be concave or flat to fix this
Hyperopia
focal point posterior to fovea or the eye is too short so far-sightedness, often occurs later in life, glasses could be convex to fix this
What are the different neurons of the retina?
rods and cones, bipolar cells, horizontal and amacrine cells, ganglion cells
Rods and cones
are photoreceptors, rods give us shape but have low acuity, have lot of rods located outside of fovea, the fovea is exclusively cones, cones show us what color we are looking at
Bipolar cells
intermediate cells between the photoreceptors and the ganglion cells, very short
Horizontal and amacrine cells
might integrate information from multiple photoreceptors on their way to the ganglion cells
Ganglion cells
cells (their axons) that become apart of the optic nerve
Blind spot
where the optic nerve forms, this is because there are no rods and cones, your mind might fill in what it thinks should be there and can trick yourself into not seeing that object at all
Pathway from the eye to the brain
lateral ganglion axons stay on same side, medial ganglion axons crossover in the optic chiasma, then synapse occurs at the thalamus, then another neuron takes the information to the primary visual cortex
The regions of the ear
external - sound conduction (external acoustic meatus), middle - sound waves are converted to mechanical vibrations (tympanic cavity, auditory ossicles), inner - specialize receptors detect pitch and amplitude and send it through the vestibulocochlear nerve
Tympanic membrane
an elastic membrane that vibrates when those sound waves hit them
Cochlea
inner part of ear which contains a variety of structures
Oval window
vibrate internal fluid known as Perilymph, next to stapes
Basilar membrane
center of cochlea, vibrates ciliated receptor cells which then stimulate our cochlear nerve to send the signal
How is pitch determined?
by which region of the basilar membrane is displaced, the fibers that are close to oval window are displaced at high frequencies while the fibers at lower frequencies are displaced at the apex of the cochlea
Premotor cortex
synapses with primary motor cortex, plan specific movements
What does the frontal lobe have?
premotor cortex and supplementary motor area
Supplementary motor area
for motor memories, for athletes and chefs
Subcortical structures
regulates motor movement
What jobs does the thalamus have?
filtering regulatory information, sending excitatory signals to the motor cortex which stimulates it and produces muscle contraction
Internal globus pallidus
one basal nuclei that inhibits the thalamus using GABA
What happens if the signal wants to be sent to the thalamus?
the basal nuclei will inhibit the internal globes pallidus by sending GABA there which allows the thalamus to stimulate the motor cortex
Alpha motor neuron
cell body is ventral grey horn, axon travel through ventral root, spinal nerve, peripheral nerves, axon terminals innervate muscle fibers
RAMI
the nerves coming into the spinal nerves that are dorsal and ventral ramus joined together to form the spinal nerve
Dorsal root ganglion
houses the cell bodies of these neurons, have a unipolar shape (middle of axon)
How do the neurons enter the spinal cord?
afferent neurons enter from either dorsal ramus or ventral ramus, then spinal nerves then dorsal root ganglion then continue and synpase with the neuron in the dorsal horn
How do the neurons leave the spinal cord?
motor neurons have their cell bodies in the ventral grey horn, and exit out through the ventral root then the axons will mix in spinal nerve and exit out either the dorsal or ventral ramus
Somatotopic organization
neurons that are medial will innervate axial muscles while neurons that are lateral will innervate appendicular muscles
Plexuses
weaving of rami which can be seen in cervical, brachial (to arms), lumbar and sacral regions
Spinal cord enlargements
cervical - enlarged to increase upper appendicular real estate, lumbosacral - enlarged to increase lower appendicular real estate
What are the neurons from brain to muscle?
upper motor neuron - brain to ventral horn, lower motor neuron - ventral horn to muscle
Direct pathway
motor cortex to skeletal muscle
Indirect pathway
brainstem to muscle
What are the direct pyramidal pathways?
corticospinal pathway, corticobulbar pathway
Corticospinal pathway
upper motor neuron which originate in motor cortex, then to cerebral peduncles of midbrain, then to pyramids of medulla (arms and legs have decussation here) then terminates in ventral horn of spinal cord (arms and legs in lateral while axial in anterior), lower motor neuron (axial will have decussation here) which will synapse with that neuron and will exit the spinal cord and go to the muscle
Corticobulbar pathway
upper motor neuron which originates in motor cortex then to cerebral peduncles of midbrain, then decussation and terminates in the brainstem and synapses with lower motor neuron then will exit the brainstem and are a part of cranial nerves
What are the indirect pathways?
vestibulospinal tracts (fine tuning for balance and posture), tectospinal tracts (head and neck movement)
Vestibulospinal tracts
upper motor neuron which originates in medulla/pons and received information from cerebellum, inner ear, and basal nuclei and terminates in ventral grey horn and the lower motor neuron will synapse and exit on same side
Ipsilateral control
lower motor neuron will exit on the same side as upper motor neurons
Tectospinal tracts
upper motor neuron which originates in superior colliculi of midbrain and receives information from optic nerve/thalamus, then terminate in cervical spinal cord
What are the ascending tracts in spinal cord?
dorsal column tracts (fasciculus gracilis - lower body and fasciculus cuneatus - upper body), spinothalamic tracts
What are the descending tracts in spinal cord?
corticospinal tracts, vestibulospinal tracts, tectospinal tracts
Reflexes
are automatic responses, can be somatic - involving skeletal muscle or autonomic - involving smooth muscle
Reflex Arc
starts with receptor attached to afferent neuron which comes into spinal cord and reach an integration center (monosynaptic or polysynaptic) then to efferent neuron which innverates a muscle that is known as an effector
Monosynaptic
one synapse between afferent neuron and efferent neuron
Polysynaptic
interneuron would exist between the afferent and efferent neurons
Patellar stretch reflex
a monosynaptic reflex, involve stretch receptor which causes an action potentials to happen in the afferent neuron (femoral nerve) then synapses in ventral horn with efferent neuron (femoral nerve) and innervates the effector (quadriceps)
Stretch receptor
a muscle spindle that is encased in a capsule that has extrafusal muscle fibers surrounding it and inside the capsule has intrafusal muscle fibers that change shape as the extrafusal muscle fibers contract which causes the action potential to be fired
Tendon reflex
prevents over contraction which can put stress on the tendons, polysynaptic reflex, and is inhibitory, first the Golgi tendon organ activates afferent neurons that travel into the spinal cord and synapses with an interneuron then the interneuron synapses with the efferent neuron
Golgi tendon organ
capsule of loosely tangled collagen fibers that are imbedded within extrafusal muscle fibers and contraction straightens these fibers
Withdrawal reflex
a reflex that promotes flexion of a limb when we experience pain, polysynaptic
Crossed extensor reflex
happen primarily in lower limbs, helps us balance on one foot, polysynaptic
Paralysis in spinal cord
regions of paralysis depend on location of injury and where decussation occurs
What happens if there is damage to lateral corticospinal tract on left side?
since the neurons have crossed over in medulla, paralysis would occur on same side in appendicular structures
What happens if there is damage to the anterior corticospinal tract?
paralysis will occur on opposite side in axial muscles
What happens in a damage to a lower motor neuron?
cause hypotonia - lack of muscle tone and atrophy
Dyskinesia
movements that are not intended to be produced
What are the basal nuclei disorders?
dyskinesia, akinesia, hypokinetic disorders (Parkinson’s disease)
Akinesia
atypical posture
Hypokinetic disorders
loss of muscle control
Parkinson’s disease
most common, occurs when the substantia nigra does not produce enough dopamine because the neurons are dying, this loss of dopamine causes the basal nuclei to not be stimulated in a desirable way
Cerebellar ataxia
loss of coordination caused by damage to cerebellum, caused by autoimmune diseases, tumor and toxins that damage the neurons in cerebellum
Stroke
not fatal, lack of oxygen supply by blockage or hemorrhagic stroke, end up with loss of motor control
What types of loss are seen with strokes?
loss of fine motor skills, spasticity, hemiplegia, and non-fluent aphasia (damage to Broca’s area)
