Midterm #1 - CH 1, 2, 3, 5

membrane

separates the inside of the cell from the outside environment

nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

Mitochondria

Powerhouse of the cell, organelle that is the site of ATP (energy) production

ribosomes

site of protein synthesis

endoplasmic reticulum

network of thin tubes transporting newly synthesized proteins

Glia

glue: holds neurons together

astrocyte

type of glial cell:

wraps around synaptic terminal

synthesizes activity for a group of neurons

microglia

type of glial cell:

removes damage and cleans up

Oligrodendrocytes

type of glial cell:

cell that make up the myelin INSIDE CNS

Schwann cell

creates myelin sheath in nerves OUTSIDE CNS

radial glia

guide migration of neurons during embryonic development

cornea

outer surface of eye

- protects eye

- refracts light

iris

colored muscle

- regulates pupil by growing and shrinking to make pupil dilate

pupil

regulates light input

lens

focuses images on retina

ciliary muscle

controls the lens

- muscles attached to the lens that stretch and relax lenses

- as you age, the muscle gets less strong so older people need glasses

fovea

center of vision

- contains most cones

birds have a second fovea

on the side

- makes peripheral vision really good

rodents have a second fovea

on bottom

- makes vision better to watch for predators ABOVE

retina

where light gets processed

- Contains photoreceptors

- transduction occurs at back of retina:

transduction

Converts light to energy to AP

Rods

- 100-120 million

- Sensitive to dim light

- black/white discrimination

- concentrated on the periphery-cannot see details

- Poor detail because many receptors converge their input onto a given ganglion cell

cones

- 4-6 million

- Used for color vision

- Very densely located near the fovea, very few cones in peripheral vision

- Red, green, blue cones

- Good detail because each cone's own ganglion cell sends a message to the brain

in a rod, each ganglion cell is excited by ____________ of rods

thousands

in a cone, each ganglion cell is excited by ______________ cone

one

Photopigments:

Chemicals contained by both rod and cones that release energy when struck by light

photopigment process

- 11-cis retinol bound to proteins called Opsin

- Light converts 11-cis to all-trans retinol

- All-trans activates second messengers within the cell

Human eyes perceive light/color from

400nm to 700nm (wavelengths)

Trichromatic theory (Young-Helmholtz Theory):

color perception occurs through the relative rates of response by 3 kinds of cones

short cone =

blue

long cone =

red

medium cone =

green

Opponent Process Theory:

suggest that we perceive color in terms of paired opposite

- Colors that we cannot perceive at the same time are termed opposing

- Red and green

- Yellow and blue

- White and black

A possible mechanism for the theory is that ganglion cells are excited by one set of wavelengths and inhibited by its opposite

Brightness constancy:

brightness is determined by comparing to nearby objects

Color constancy:

ability to recognize colors despite changes in lighting

Retinex Theory:

V1 cells in the cortex compare info and signals from different parts of the retina to determine color and brightness

- Assumptions based on experiences affect perception

Receptive Field:

part of the visual field hat either excite or inhibit a cell

- For a receptor, point in space from which light strikes it

- For other visual cells, receptive fields are derived from the visual field of cells that either excite or inhibit cells

Ex: ganglion cells converge to form the receptive field of the next level of cells

3 Cellular Layers of the Retinal Ganglion Cell and the LGN

parvocellular

magnocellular

koniocellular

Parvocellular:

Sensitive to color and detail

- in/near fovea

- Small body

- Small receptive field

Magnocellular:

Sensitive to patterns and motion

- Throughout retina

- Large body

- Large receptive field

Koniocellular:

several functions-sensitive to color, shape, patterns, and motion

- Throughout retina

- Small body

- Varied receptive field

Horizontal cells:

type of cell that receives input from receptors and delivers inhibitory input to bipolar cells

- Convert shapes into amacrine cells and ganglion cells in the eyeball

amacrine cells

get info from bipolar cells and send it to other bipolar cells

- enable certain areas to respond

bipolar cells

type of neuron in the retina that receives input directly from the receptor

ganglion cells

type of neuron in the retina that receives input from the bipolar cell

optic nerve

ganglion cell axons that exit through the back of the eye and continue to the brain

- Leaves the retina and travels along the lower surface of the brain

- Ends at either the LGN of the thalamus or hypothalamus and superior colliculus

Superior colliculus:

helps us to quickly shift eyes to stimulus

optic chiasm

where the optic nerve from two eyes meet

- Half axons from each eye ross ino the opposite side of the brain

- Info from temporal half goes to ipsilateral (same) hemisphere

Lateral Geniculate Nucleus (LGN):

primary relay center for visual information received from the retina of the eye (located in thalamus)

- Most ganglion cell axons go in this part of the thalamus

- Some axons go to the superior colliculus and hypothalamus

- Areas that control waking-sleeping schedule

- Sends axons to other parts of the thalamus and visual cortex

- Axons returning from the cortex to the thalamus modify thalamic activity

Lateral inhibition:

reduction of activity in one neuron by activity in the neighboring neurons

- Function = to sharpen borders

- Important for any function in the NS

- In olfaction (smelling), strong stimulus act suppress the response to another that follows close after it due to the inhibition of the olfactory bulb

- In touch, simulation of one spot on the skin weakens the response to stimulation of a beginning sot

- In hearing, inhibition makes it possible to understand speech even with background noise.

The Primary Visual Cortex (V1):

area of the cortex responsible for the first stage of visual processing

- located in occipital cortex aka area V1 or striate cortex

V1 damage

People have no conscious vision, visual imagery and no visual images in their dreams

BUT Adults who lose their vision still have visual imagery and visual dreams

Blind sight:

ability to respond to limited ways to visual info without perceiving it consciously

- Small islands of healthy tissue remain within an otherwise damaged visual cortex, not large enough to provide conscious perception but enough to support limited visual functions

- Thalamus sends visual input to many brain areas including temporal cortex

Simple cell:

type of visual cortex cell that has a receptive field with fixed excitatory and inhibitory zones (ONLY ONE LOCATION)

- The more light shines in excitatory zones, the more the cell responds

- The more light shines in inhibitory zone, the less the cell responds

Complex Cell:

type of visual cortex cell located in areas V1 and V2 that respond to a pattern of light in certain orientation ANYWHERE within it large receptive field

- Responds strongly to stimulus moving a certain direction

End-stopped/hypercomplex cells:

strong inhibitory area at one end of its bar-shaped receptive field

- Same as complex cell but with inhibitory zone like a simple cell

- Responds to bar shaped pattern of light anywhere in its broad receptive field, assuming the bar doesn't extend beyond a certain point

Cells with similar properties group together the visual cortex in columns perpendicular to the surface

Ex: cells in a column might respond to only the left eye, only the right eye, or both eyes equally

- Cells within a column respond best to lines of a single orientation

Feature detectors:

neurons whose responses indicate the presence of a particular feature-shape or direction of movement

If one eye is closed during early development,

the cortex becomes unresponsive to it.

If both eyes are closed,

cortical cells remain somewhat responsive for several weeks, gradually becoming sluggish and unselective in their responses.

Stereopsis (depth perception):

the visual ability to perceive the world in three dimensions (3D) - length, width, and depth

requires the brain to detect retinal disparity

Retinal disparity:

the discrepancy (difference/inconsistency) between what the left and right eyes see

Strabismus: aka lazy eye;

eyes point different directions

If eye muscles can't keep both eyes focused in the same direction, the developing brain will lose the ability for neurons in the visual cortex to respond to input from BOTH eyes, so it'll just respond to ONE eye, causing a loss in stereoscopic depth perception

Astigmatism:

decreased responsiveness to one direction of a line or another

- Due to a not fully spherical eyeball

EX: If a child with dense cataracts on both eyes gets surgery after a few years, the child will be able to identify if objects are the same or different but won't be able to process what the visual info means

The primary visual cortex (V1) sends info to the

secondary visual cortex (area V2)

Area V2: processes info from V1 and transmits it to additional areas

- processes info from V1 and transmits it to additional areas

- Connection between V1 and V2 goes both ways

- Most cells in V2 are similar to V1 cells

- Lines, edges and sine wave gratings

V2 are more elongated cells and respond best to corners, textures and complex shapes

Areas V2 and V3 have some cells highly responsive to color and other cells highly responsive to the disparity between what the left and right eyes see

Area V4: color and curvature

Ventral stream:

visual paths in the temporal cortex that are specialized for identifying and recognizing objects

- The "what" path

- Object recognition

- Matches visual shape to internal representation

Visual Agnosia:

damage in the ventral-the absence of visual knowledge- can't identify what things are

Damage in the temporal cortex causes this

Associated agnosia: can't perceive or identify what they drew, but can draw/copy very well

Dorsal stream:

visual path in the parietal cortex that helps the motor system locate objects

- The "where" path

- Spatial location, topographical orientation, visually guided movements

Ex: Football guy passing ball and timing it correctly for the guy catching the ball

Apraxia:

damage in the dorsal-can't perform planned tasks

- Can't draw/copy pictures

People with temporal lobe damage can use vision to guide their actions, but

they cannot identify what the objects are

Inferior Temporal Cortex-

Portion of the cortex where the neurons are highly sensitive to complex aspects of the shape of visual stimuli within very large receptive fields

specialized areas for perceiving places, faces, and bodies, including bodies in motion.

Fusiform Gyrus:

brain area of the inferior temporal cortex that recognizes faces

connections between ________ and _________ strengthen the fusiform gyrus as they age

right hemisphere and part of the inferior occipital cortex aka occipital face cortex

Prosopagnosia:

impaired ability to recognize faces

- Due to damage in fusiform gyrus or not full development of the fusiform gyrus

MT (middle temporal cortex):

important for perception of visual motion

- Color insensitive

- Respond selectively when something moves at a certain speed in a certain direction

- Detects acceleration, deceleration and absolute speed

- Respond to motion in all 3 dimensions

- Gets some input directly from LGN of the thalamus

MST (medial superior temporal cortex):

responds best to complex stimuli like the expansion, contraction to rotation of visual display

MT and MST receive input mostly from the

magnocellular path: detects patterns of movement over large areas other visual field and ss color incentive

MT and MST allow us to

distinguish the result of eye movements and the result of object movements

Motion Blindness:

Impaired ability to perceive movement

- World moves in stops and starts: stop, go, stop, go; no smooth motion

- People with motion blindness are better at reaching for a moving object than at describing its motion

- Still lack and fall behind others with visual motion detection

Saccades:

voluntary eye movement

- Brain areas that monitor saccades tell area MT and parietal cortex to takes a rest since they're moving the eye muscles

- People become motion blind shortly before and during a saccade (voluntary eye movement), because of suppressed activity is area MT.

central nervous system

brain and spinal chord

peripheral nervous system

connects brain and spinal chord to rest of body's nerves outside of the brain and the spinal chord

which NS has two parts; the somatic NS and autonomic NS?

peripheral

somatic nervous system

axon conveying messages from the sense organs to peak CNS from the CNS to muscles

autonomic nervous system

controls the heart, intestine, and other organs

has some of its cell bodies within the brain and spinal cord

which NS has the sympathetic and parasympathetic nervous systems

autonomic NS

sympathetic nervous system

network of nerves that prepare organs for hard activitiy

- fight or flight

- INcreases breathing, HR, stress

- DEcreases digestion

- releases norepinephrine

sweat and adrenal gland and muscles that constrict blood vessels have sympathetic input NOT para

parasympathetic nervous system

network of nerves for vegetative, nonemergency responses

- rest and digest

- DEcreases HR

- INcreases digestion

- releases acetylcholine

- promotes sexual arousal

Which NS is aka the craniosacral system because of cranial nerves and nerves from the sacral spinal cord

parasympathetic nervous system

dorsal

toward the back

ventral

toward the stomach

anterior

toward the front end

posterior

toward the back end

superior

above another part

inferior

below another part

lateral

toward side/away from middle

medial

toward middle/away from side

proximal

located close to the point of origin/attachment

distal

located far from the point of origin/attachment