Sleep and VIsion Flashcards
The ____ Muscles are essential for accommodation
Ciliary
Cones in the retina form synapses with which of the following cell types?
Bipolar Cells
What is responsible for the lack of photoreceptors at the optic disc and the consequent blind spot?
Correct!
It is the location where blood vessels and ganglion cell axons leave the eye
The brightest light we can see is about _____ times as intense as the dimmest light we can see
10 Billion
Why is it best to look slightly off center to see a distant, dim star?
Rods are absent in the fovea and numerous in the retina periphery and are sensitive to dim light
Cells in the primate LGN have receptive fields that
Concentric
In _____ cells, light falling in the center of the cell causes excitation, and light falling in the surround cause inhibition
On-center/off-surround
Rod receptors are _____ by the presence of a light stimulus
Hyperpolarized
One of rod vision is less acute because
Rods have higher convergence onto retinal ganglion cells
Which best describes the order of information flow out of the retina
Photo receptor, bipolar cell, retinal ganglion cell
Layer of neurons
Retina
Turning light into neural signals in a process called
Transduction
Bending of light rays
Refraction
Outer layer of eye
Cornea
Light passes through the cornea is further refracted by the lens which
Changes its shape to fine tune that image on the retina
Nearer images to come into focus on the retina process is called
Accomodation
Difficulty seeing distant objects
Myopia
How does myopia develop?
If the eyeball is too long, causing the cornea and lens to focus images in front of the retina rather than on it
Movement of eye is controlled by
Ocular muscles
Where does the first stages of visual process occur?
In the Retina-200-300 micrometer thick
Photoreceptors?
Sensory neurons that detect light
Where do rods and cones photoreceptors release neurotransmitters?
into synapses on bipolar cells
What do bipolar cells connect with
ganglion cells
What do ganglion cells form
The optic nerve
Horizontal cells
make contacts among the receptor cells and bipolar cells
Amacrine cells
Contact both the bipolar and ganglion cells
What do the rods, cones, bipolar, and horizontal cells generate
only graded local potentials, DO NOT produce action potentials
What do ganglion cells conduct
Action potentials
What are rod based systems
Scotopic system (darkness) very sensitive works well in low light. Insensitive to color- cant tell colors apart at night
Convergence
Lots in the scotopic system b/c info from many rods converges onto each ganglion cell
Cones based system
Less sensitive than rods, have higher threshold before they respond. Requires more light to function
Photopic system
differential sensitivity to wavelengths enabling our color vision, has less convergence
Where are light particles detected?
Stack of discs
Only a fraction of light that strikes the cornea actually reaches the retina?
True
Photoreceptors in the dark release
Neurotransmitters onto bipolar cells
When light hits photopigment in the photoreceptor it triggers a cascade of chemical reactions
Hyperpolarize the cell, released less neurotransmitter onto bipolar cells
Stimulation of rhodopsin by light
Hyperpolarize the rods- for rods and cones the size of hyperpolarizing photoreceptors potential determines how much less neurotransmitter will be released
Handling of different light intensities by different receptors with some low thresholds (rods) and other with high thresholds (cones)
Range fractionation
Sharpness of vision
Visual acuity
Where is the highest acuity
In the fovea, more densely packed with cones
Rods provide high sensitivity with
limited acuity
Cones provide
High acuity with limited sensitvity
In the fovea light
reaches the cones without having to pass through blood vessels and other layers of cells
Optic disk is on the
nasal side of the fovea, where blood vessels and ganglion cells axons leave the eye
Why is the optic disk our blind spot?
There are no photoreceptors
Ganglion cells in each eye produce
Action potentials, conduct along their axons to send visual information to the brain. These axons make up the optic nerve
Optic nerve cross the midline at the
Optic chiasm
Half the retina toward your temple project
its axons to its own side of the brain
Where do the majority of retinal ganglion cells send their optic tract axons
Superior coliculus in the midbrain- coordinates rapid movement and controls pupils response to light levels
Most axons on the optic tract terminate on cells in the
Lateral geniculate nucleus (LGN)- visual part of the thalamus
Primary visual cortex is important for
Depth perception
Spot where nothing is perceived- person cannot consciously perceive visual cues
Scotoma
Sensory cells consists of the stimulus features that
Excited or inhibits the cells
Both rods and cones photoreceptors release the synaptic transmitter
Glutamate- light always hyperpolarizes
On bipolar cells glutamate is
Inhibitory
Glutamate is excitatory to
Off- center bipolar cells
Bipolar cells release
Glutamate- always depolarizes ganglion cells
When light is turned on
on center bipolar cells depolarize (excite) on center ganglion cells
When light is turned off
off center bipolar cells depolarize (excite) off center ganglion cells
The entire receptive field of a bipolar cell is
Concentric
Sensory receptor cells inhibit the reporting of information from neighboring receptor cells
Lateral inhibition
What is free running
maintaining its own personal cycle in the absence of external cues
T/ F removing various endocrine glands had little effect on the free running rhythm of rats
True
Suprachiasmatic nucleus (SCN)
A small region of the hypothalamus above the optic chiasm that is the location of a circadian clock
Electroencephalography (EEG)
provide a way to define, describe, and classify levels of arousal and states of sleep
Fully awake alert person is a mixture of what?
low amplitude waves with many relative fast frequencies
Beta activity also known as
desynchronized EEG
Non REM sleep stage 1
slowing of the heart rate and relaxation of the muscles, eyes may roll back slowly
Stage 2
Defined by waves 12-14 Hz called sleep spindles, occur in periodic bursts and by K complexes
Stage 3 (SWS- Slow wave sleep)
Appearance of large amplitude very slow waves called delta waves
REM sleep (paradoxical sleep)
small amplitude, high frequency activity similar in many ways to the pattern on an awake person, except eyes moving back and forth across eyelids
Atonia
Complete absence of muscle tone
During REM motor neurons are
Inhibited, and is accompanied by irregular breathing and pulse rate as in wakefulness, also experience vivid dreams in this state
Stage 3 we are mostly
most deeply asleep and the pituitary gland releases growth hormone
When do night terrors occur
Sudden arousal from stage 3 SWS
Infant sleep is characterized as
Shorter sleep cycles than adults, also showing large perception of REM sleep. Half of sleep in the first two weeks of life is REM
What stage is the most dramatic decline in sleep
Stage 3 sleep 60 year old people spend only half as much time in stage 3 than they did when at age 20. 90 years old stage 3 sleep has disappeared
Photoreceptors are depolarized in the absence of
Light, and constantly release glutamate in the dark
Temple side
Ipsilateral
Nasal side
Contralateral
The circadian rhythm is synchronized by
Light
Lesion of the SCN will
Eliminate circadian rhythm
Retinal ganglion cells form
the retinohypothalamic pathway, carries light information from the eye to the SCN
The relaxed mind exhibits
Alpha rhythm, regular oscillation at the frequency 8-12 hz
Energy Conservation theory
Reduces energy consumption during a time when it is more difficult or dangerous to look for food
Restorative function
Materials used up during waking hours, rebuilt or restored of proteins
Forebrain system
Generates SWS
Brainstem system
Activates forebrain to wakefullness
Pontine system
Triggers REM sleep
Hypothalamic system
Coordinates the other three
The forebrain generates
Slow wave sleep
Reticular Formation Wake up the Forebrain
Acts on basal forebrain
Reticular Activating System (RAS)
Together, the forebrain and reticular formation seem to regulate SWS and wakefulness
Locus coeruleus
Responsible for REM sleep
Orexin neurons in the hypothalamus project to other sleep systems centers
Basal forebrain, reticular formation and the locus coeruleus
What does orexin do?
Determines wakefulness, non- REM sleep, or REM sleep
Interfering with hypocretin signaling leads to
Narcolepsy- People that frequent intense sleep attacks- Do not go through SWS before REM sleep
Sleep onset insomnia
Difficulty in falling asleep and can be caused by situational factors, shift work, or jet lag
Sleep-maintenance insomnia
Difficulty in staying asleep and may be caused by drugs or neurological and psychiatric factors- especially evident in respiratory disorders
Muscle spindles respond to
Muscle stretch and respond during lengthening
Golgi tendon organs are sensitive to
Tension during contraction
Passive stretching of a muscle
Cause activation of the muscle spindle
Spindle will synapse on
alpha motor neuron in the spinal cord
Cerebellum is important for
Making corrections
Pyramidal (or corticospinal) tract
Looks like upside down pyramid- - Comes from primary motor cortex. Name coming from the pyramidal shape of the tract in the medulla- collecting axons from entire motor cortex
Extrapyramidal tract
Modulating reflexes and online tuning of movement- Name reflects the fact this it is outside the pyramidal tract
Pyramidal Tract (corticospinal tract)
Sends motor commands from the brain to the spinal cord- Pass through the pyramids of the medulla.
The lateral tract (90% of fibers)
Cross at the medulla and controls movement of the contralateral limbs- controls the other side of the body
The ventral portion (10% of fibers)
Crosses in the spinal cord and controls trunk movement (controlled together)- does not cross over until synapses the alpha motor neurons
Pyramidal Motor Tract
Many signals originate in upper motor neurons in the primary motor cortex (M1)- send synapses down- Make synapses on alpha motor neurons (also called lower motor neurons) in the spinal cord
Lower limbs
Dorsally and medially
Face
Vental and lateral
Hand area
In between
Large muscles group
Much smaller, Lips, tongue, and hands- have the most control
M1 cells
Change firing rate according to direction of the movement
Extrapyramidal system
Basal ganglia- important for movement and learning (Habit learning dictated by basal ganglia) are a group of structures in the middle of the brain- Plays a role in action selection and onset as well as the execution of learned movement
The cerebellum
Has more neurons in itself than the rest of the brain-consistent wiring pattern, computer of the brain)- is important for motor learning and helps to regain movement as they are happening- makes movements smooth and more accurate- alcohol consumption can affect this
Premotor cortex
In front of motor cortex more on the lateral side- translating sensory information to appropriate motor goals and plans
Supplementary motor cortex
Mainly on the medial surface of the cerebral hemispheres lies on top actions that are well-learned, and actions stimulated by a stimulus in the environment- well-learned actions
The premotor cortex is important in
Translating sensory information into action
The SMA is
Is important for representing internal action goals and for action initiation
What does LTM have
Vast capacity but is subject to forgetting
Doe not deteriorate over time but is it interfered with by other events that occur before or after their formation
Memory tract
The process from retrieving info from LTM can cause
Memories to become unstable and susceptible to disruption or alteration
The return of memory trace to stable long-term storage after recall
Reconsolidation
Synaptic plasticity
Research has focused on learning-related changes in the strength of the synapsis
T/F we dont grow new neurons in our brain but can grow new axon collaterals- more effective having branch out and broader reach
True
Three housing conditions
Standard condion (SC)
Impoverished condition (IC)
Enriched condition (EC)
