Bio Basis Exam 2

Genes vs Alleles

Gene - part of chromosome that codes of a trait

Allele - specific form of a gene

DNA vs RNA

DNA seves as template of RNA (mRNA)

Homozygous vs Heterozygous Inheritance

Homozygous - inherited alleles are identical

Heterozygous - inherited alleles are different

Autosomal genes

on autosomal chromosomes (not sex chromosomes)

Sex-linked genes

on sex chromosomes

Sex-limited genes

on autosomal chromosomes; present in both sexes but only active in one because of hormonal or anatomical differences

Gene mutation

Permanent change in DNA sequence

Histone modification

post-translational chemical alteration of histone proteins (such as H2A, H2B, H3, and H4) that regulates chromatin structure and gene expression without changing the underlying DNA sequence

DNA methylation

an epigenetic mechanism that adds a methyl group (-CH₃) to the 5-carbon position of a cytosine ring, forming 5-methylcytosine without changing the underlying DNA sequence

Stages of brain development

1. 1. Proliferation - production of new cells, begins when neuron tube has closed in the tube’s ventricular zone

2. 2. Migration - new neurons travel from place of origin in the ventricular zone near the center of the brain to their final locations (radial vs tangential migration)

3. 3. Differentiation - process of neurons becoming distinct with a certain function, forming dendrites, axons, and synaptic connections, occurs due to exposure to hormones and certain chemicals, continues after birth

4. 4. Myelination - oligodendrocyte progenitor cells mature into oligodendrocytes that produce myelin for new neurons (spine → hind → mid → fore)

5. 5. Synaptogenesis - formation of new synapses

Cell proliferation

production of new cells, begins when neuron tube has closed in the tube’s ventricular zone

Pluripotent stem cells

unspecialized cells that can self-renew indefinitely and differentiate into almost any cell type of the adult body

Cell migration

new neurons travel from place of origin in the ventricular zone near the center of the brain to their final locations (radial vs tangential migration)

Immunoglobulins and chemokine function on migration

intrinsic guidance cues during normal brain developmen

Myelination

oligodendrocyte progenitor cells mature into oligodendrocytes that produce myelin for new neurons (spine → hind → mid → fore)

Oligodendrocyte progenitor cells

proliferate, migrate, and differentiate into mature, myelinating Oligodendrocytes

Synaptogenesis

formation of new synapses

Neural Darwinism

We start with more neurons and synapses than needed → most successful synaptic connections are kept → the rest are removed through synaptic pruning

Rita Levi-Montalcini

Discovered that muscles determine axon survival, not axon formation, Nerve Growth Factor

Nerve Growth Factor

a neurotrophin promotes axon survival and growth (no NGF = axon apoptosis/programmed cell death)

Fetal Alcohol Spectrum Disorder

Teratogen, short dendrites with few branches, alcohol suppresses glutamate and enhances GABA

Far transfer

Improvement of a skill due to practice at a dissimilar skill (not a large effect)

Brain plasticity in deafness and blindness

Blindness - temporal cortex = movement of sounds, occipital lobe = tactile/verbal info

Deafness - visual processing goes to auditory cortex

Types of stroke

Ischemia - blood clot/obstruction in artery, more common

Hemorrhage - ruptured artery causing bleeding around the brain

Effects of stroke

Edema - accumulation of fluid

sodium-potassium pump impairs so that sodium accumulates in neuron (increases glutamate and blocks metabolism in mitochondria)

Treatments for stroke

tissue plasminogen activator (tPA) breaks up blood clots if delivered within 4.5 hours, only for ischemia

medication blocking glutamate transmission and calcium entry

cooling the brain

cannabinoids

stimulants for healthy brain areas

Phantom limb

Original synapses deteriorate, leaving space for sprouting

Law of specific nerve endings

activity of a specific nerve always conveys the same type of information to the brain

exception - synesthesia

Pupil

Opening where light enters the eye

Cornea

Glassy transparent external surfface of the eye

Lens

clear, curved structure located directly behind the iris and pupil that bends and focuses light onto the retina

iris

gives color to eyes

Optic nerve

nerve bundle of axons from the retina

Myopia vs Hyperopia

Myopia (nearsightedness) and hyperopia (farsightedness) are opposite refractive errors—meaning the shape of the eye stops light from bending correctly onto the retina

Visual acuity

ability to distinguish two nearby points

Visual angle

distance across the retina described in degrees

Photoreceptors

specialized light-detecting neurons located in the retina at the back of the eye that convert light into electrical and chemical signals for the brain

Bipolar cells

specialized sensory interneurons located in the retina of the eye that transmit and process visual signals from photoreceptors (rods and cones) to ganglion cell

Ganglion cells

final output neurons of the vertebrate retina that collect visual and non-visual signals from preceding retinal cells and transmit them to the brain

Rods vs Cones

Rods - long, cylindrical outer segment with many disks, 1000x more light sensitive than cones

Cones - shorter, tapering outer segment with fewer disks, color

more cones in the center of the eye

Fovea

center of retina, acute detailed vision, has most receptors

central fovea = all cones (no rods)

Optic Chiasm

a flat, X-shaped structure at the base of the brain where the optic nerves from each eye meet, converge, and partially cross over

Lateral geniculate nucleus

a sensory relay structure located in the posteroventral region of the thalamus that processes and routes visual information from the retina to the visual cortex

Lateral inhibition

retina’s way of sharpening contrasts to emphasize the borders of objects → reduced activity in a neuron by activity in neighboring neurons

Receptive field

the point in space that activates specific photoreceptors, where light strikes

Aphantasia

no inner eye

Hyperphantasia

extremely detailed inner eye

Blindsight

ability to respond to visual info without perceiving it consciously

Primary visual cortex damage

disrupts how the brain processes incoming visual signals consciously

blindsight

Secondary visual cortex function

receives info from v1 for further processing

Ventral stream

goes through temporal cortex, the “what” pathway

identifying and recognizing objects

Dorsal stream

goes through parietal cortex, the “where/how” pathway

visually guided movements

Ventral stream damage

can see where objects are but cannot identify them (visual agnosia)

Dorsal stream damage

can identify objects but not know where they are

Fusiform face area

in fusiform gyrus, facial recognition

Prosopagnosia

impaired ability to recognize faces after damage to fusiform gyrus

Amplitude

intensity of sound wave (volume)

height of peaks

Frequency

number of compressions per second measured in Hz

length between peaks

Timbre

tone quality/complexity

Pinna

flesh and cartilage, alters reflection of sound waves to help locate source of sound

Tympanic membrane

eardrum

connects to 3 bones that transmit vibrations to oval window

Malleus, Incus, Stapes

smallest bones in human body

stapes vibrates oval window which vibrates fluid in choclea

Oval window

a membrane-covered, kidney-shaped opening that connects the middle ear to the vestibule of the inner ear

Cochlea

a snail-shaped, fluid-filled organ in the inner ear that converts sound vibrations into electrical signals for the brain

Basilar membrane

a stiff, vibrating partition inside the cochlea of the inner ear that separates the fluid-filled scala media from the scala tympani and supports the sensory receptor cells of hearing

has hair cells

Frequency theory

Basilar membrane vibrates in synchrony with sound, produces action potentials at the same frequency

Place theory

Each area of basilar membrane has hair cells sensitive to specific frequencies

Primary auditory cortex function

important for auditory imagery

processing “what” and “where”

contralateral control

damage affects imagined sounds

Amusia

tone deafness

fewer connections between auditory cortex and frontal cortex

Conductive deafness vs nerve deafness

Conductive - middle ear bones fail to transmit sound waves to cochlea, caused by disease, infection, or tumorous growth, can hear own voice, corrected by surgery or hearing aids

Nerve - damage to cochlea, hair cells, or auditory nerve, can be confined to one part of cochlea, can be inherited, baused by disease, or loud noise

Vestibular sense

controls balance, spatial orientation, and head-eye coordination

Otolith organs

tell brain what direction you are moving

saccule and utricle

Types of somatosensory receptors

Free nerve endings
Hair-follicle receptors
Meissner's corpuscles
Pacinian corpuscles
Merkel's disks

Ruffini endings

Krause end bulbs

Cold-sensitive vs heat-sensistve neurons

Cold-sensitive - respond to drops in temperature, adapt quickly

Heat-sensitive - do not adapt, responds to absolute temperature

Somatosensation in CNS vs PNS

• Info from touch receptors in head enters
CNS through cranial nerves
• Each spinal nerve has a sensory component
and a motor component
• Dermatome

Mild pain vs strong pain

• Mild pain – release of glutamate in spinal
cord
• Stronger pain – release of glutamate +
neuropeptides

Opiates and endorphins effect on neurons

Opiates - bind to receptors in spinal cord, acts on nervous system rather than injured tissue

Endorphins - transmitters that attach to same receptors as morphine’s, several types produced

Taste receptors

modified skin cells replaced every 10-14 days

release neurotransmitters

Papillae

small, raised nipple-like structures found on the surface of the tongue

each papilla contains 10+ taste buds

Taste buds

clusters of 50 receptors

Types of taste receptors

sweet, salty, sour, bitter, and umami (savory)

Saltiness receptor function

Permit sodium ions to cross membrane

Sour receptor function

Detect presence of acids

Sweetness receptor function

Activate G-protein which releases a second messenger

Butterness receptor function

Activate G-protein which releases a second messenger

Umami receptor function

Activate G-protein which releases a second messenger

Primary taste cortex

Insula

the region of the cerebral cortex responsible for the conscious perception and intensity of taste

Variations in taste sensitivity

Variance in genes, age, environmental factors, and number of papillae and taste buds

Olfactory epithelium

a specialized patch of mucous membrane located on the roof of the nasal cavity that detects and translates odor molecules into electrical signals for the brain

Cilia

microscopic, hair-like membrane protrusions that extend from the surface of many eukaryotic cells

Olfactory bulb

a paired neural structure in the forebrain that processes the sense of smell, where axons carry info

Glomerulus

a tiny network of looping blood vessels (capillaries) located at the beginning of a nephron

Where receptors for particular chemicals converge