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production of new cells.
forming an axons and dendrites.
immature or undifferentiated cells.
glia produce fatty sheaths that accelerate transmission of impulse.
formation of synapses.
- discovered that axons can grow back and connect.
- cut newt’s optic nerve.
nerve growth factor (NGF)
- promotes the survival and growth of the axon.
- cell body dies without it.
- programmed mechanism of cell death.
- different from necrosis b/c damage does not kill the cell.
- NGF cancels the program.
- promotes the survival and activity of neurons.
- when neurons release neurotransmitters they also release these.
brain derived neurotrophic factor
- most abundant neurotrophin in adult brain
- for survival of connecting neurons
- and survival of neurons being connected
fetal alcohol syndrome
- condition marked by impulsiveness, difficulty maintaining attention, motor problems, facial abnormalities
- most dendrites are short with few branches.
- anesthetic drugs increase inhibition of neurons, blocking most action potentials.
focal hand dystonia
fingers become clumsy, fatigue easily and make involuntary movements that interfere with task.
closed head injury
sharp blow to the head resulting from an accident, assault, or other sudden trauma, also blood clots
- cerebrovascular accident
- hemorrhage or ischemia
- impairs the sodium-potassium pump leading to accumulation of sodium within neurons.
stroke as a result of a blood clot or other obstruction in an artery.
stroke as a result of a ruptured artery.
accumulation of fluid which puts pressure on the brain.
tissue plasminogen activator (tPA)
- breaks up blood clots
- patient should receive it within 3 hours of a stroke.
- has serious side effects including hemorrhage.
region surrounding the immediate damage.
- decreased activity of surviving neurons after damage to other neurons.
- increased stimulation should help if there are behavioral deficits.
minimizing stroke damage
- cool the person for 3 afterward (91-97 degrees)
- cannabinoids reduce cell loss after stroke (anti-inflammatory actions)
regrowth of axons
- in mammals only regrow a 1mm or 2mm
- a cut causes a scar which inhibits growth
- neurons cut pull apart
new branches from axons that attach to vacant synapses.
heightened sensitivity to a neurotransmitter after destruction of an incoming axon.
heightened sensitivity as a result of inactivity by an incoming axon.
- only develop if the portion of the somatosensory cortex reorganizes and becomes responsive to alternative inputs.
- connections in the brain remain plastic throughout life.
limb has lost its afferent sensory input.
law of specific nerve energies
impulses in one neuron indicate light, impulses in another indicate sound.
- closest to center of eye
- receive bipolar messages
- form optic nerve
- middle layer of receptor cells
- receives input from rods and cones
tiny area specialized for acute detailed vision.
each is small and responds to just a single cone.
- more numerous than cones
- for dim light
- not in color
- more numerous in periphery or macula
- chemical that releases energy when struck by light.
- rods and cones contain photopigments.
- need bright light
- highest concentration in fovea
- color vision
- less numerous than rods
wavelengths we can see
trichromatic theory of color vision
we perceive color through the relative ratio of response by three kinds of cones
opponent process theory of color
we perceive color in terms of opposites
- cortex and retina perceive color
- cortex compares info from various parts of retina to determine the brightness and
- color for each atrea
color vision deficiency
- complete color blindness is rare
- some people lack one or two of the types of cones b/c of genetics
lateral geniculate nucleus
part of the thalamus
part of the visual field that excites or inhibits a cell.
- small cell bodies and small receptive fields
- mostly in or near the fovea.
- larger cell bodies and receptive fields
- distributed evenly throughout retina.
- small cell bodies
- occur throughout retina.
ability to respond to visual info that people report not seeing.
primary visual cortex
- occipital cortex/ V1
- damage: no conscious vision, imagery, images in dreams.
secondary visual cortex, v2
processes the information further and transmits it to additional areas.
- the “what” pathway
- specialized for identifying and recognizing objects.
- the “where/how” pathway
- because it helps the motor system find and use objects.
- has a receptive field with fixed excitatory and inhibitory zones.
- response depends on angle of bar of light.
- part of the shape pathway
- part of the shape pathway
- do not respond to exact location of a stimulus.
- responds the same for a bar in any position within the receptive field.
- resemble complex cells except it has a strong inhibitory area at one end of its bar-shaped receptive field.
- part of shape pathway.
- oriented in perpendicular planes
- filled with a jellylike substance and lined with hair cells.
sensation of the body and its movements is many senses.
detects sudden displacements of high frequency vibrations on the skin.
- limited area of the body that gets its own spinal nerve
- overlaps one third to one half of next dermatome
- Spinal nerves connect 31 dermatomes to CNS
chemical found in hot peppers that stimulates pain receptors.
released during mild pain
released during strong pain
systems that respond to opiate drugs and similar chemicals.
periaqueductal gray area
opiates bind to receptors found here in the midbrain.
contraction of endogenous morphines.
spinal cord neurons that receive messages from pain receptors also receive input from touch receptors and from axons descending from the brain.
Vestibular organ is located close to inner ear (cochlea)
- Monitors:Direction of head tilt; Acceleration of the head
- Easier to read a sentence while you move your head than if someone else moves the sentence around
- Movement of head to right -> compensatory eye movement to the left, and vice versa
Vestibulo-ocular reflex –
connects vestibular organ with muscles of the eye.
consists of 2 otolith organs
- calcium carbonate particles, lie next to hair cells in a chamber
- Movement pushes particles against hair cell – excitation
- Chambers with patches of hair, detect motion in
- Horizontal – Utricle
- Vertical – Saccule
action potentials from hair cells travel through 8th cranial nerve to brainstem (pons) and cerebellum
Nausea induction: optokinetic drum; environment is moving but you aren’t, throws you off
- Located in both hairy and hairless areas of the sin
- Responds to stretch of skin, slipping of objects along skin
- Helps with finger coordination (gripping objects)
Free nerve ending
- Unmyelinated or thinly myelinated axons
- Located near base of hairs and in skin
- Sensations of pain, warmth, cold
- Can also be stimulated by chemicals
- Capsaicin (chemical in hot peppers)
Conversion of physical or chemical stimuli into bioelectrical signals, by specialized cells or sensitive endings in sense organs: “receptors”
2 pathways of pain
- sensory – to thalamus, somatosensory cortex
- emotional – to medulla, thalamus, hypothalamus
reacts to emotional aspect of pain not the sensation
- long fibers extend from inner t outer layers of brain
- guide migration and growth of axons
- different types of stimuli (light, mechanical pressure) can act upon a particular sensory nerve (retinal receptors, optic nerve), will create the same sensations (vision)
- “common currency”: all types of sensory nerves send same type of information to the brain: action potentials
Specificity of brain area:
- where never fibers terminate gives special character of sensation
- Brain “sees” the activity of optic neurons and “hears” the activity of the auditory neurons.
- Where nerve fibers end is where sensory quality is encoded.
exchange info with bipolar cells and send info to ganglion and other amacrine cells
control lens, can make it flatter or thicker (seeing objects closer) controlled by parasympathetic and sympathetic NS
- 3x5 mm center of retina with greatest ability to resolve detail
- fovea: the center of the macula
Explanation for afterimages:
- Retinal cells produce opposite color output
- Short wavelength = excitation = blue
- Long wavelength = inhibition = yellow
- Then presentation of neutral white or gray ->produces experience of the opposite color yellow (because it is inhibited)