combined ibn sets

skeletal muscle

striateed muscles used for voluntary movement (bones), respiration, and facial expression

cardiad muscle

striated muscle of the heart; moves rhythmically even without nervous system innervation (regulated by the ANS)

smooth muscle

non-striated muscle found in organs (peristalsis) and blood vessels (blood pressure); regulated by the ANS

antagonists

a pair of muscles that move a joint in opposite directions. for example, the biceps (flexor) and triceps (extensor)

synergists

muscles that work together to move a joint in the same directionm

muscle fibers

the individual cells that make up a muscle. one fiber = one cell

alpha motor neurons

large neurons in the ventral horn of the spinal cord that are directly responsible for triggering muscle contraction

gamma motor neurons

neurons that innervate the specialized ‘intrafusal’ fibers inside a muscle spindle; they help maintain the sensitivity of the spindle to stretch

motor unit

a single alpha motor neuron and all the muscle fibers it innervates. this is the smallest unit of motor control

motor neuron pool

all the alpha motor neurons that innervate a single muscle

ventral horn

the front portion of the spinal cord gray matter where motor neuron cell bodies are located

neuromuscular junction (NMJ)

the specialized synapse between a motor neuron axon terminal and a muscle fiber

acetylcholine (ACh)

the exclusive neurotransmitter used by motor neurons at the NMJ to trigger muscle contraction

nicotinic ACh receptor

the specific ionotropic receptor on the muscle fiber that opens sodium channels when ACh binds

end-plate potential

the large depolarization produced in a muscle fiber by the release of ACh; it is always large enough to trigger an action potentual in the muscle

sarcoplasmic reticulum

an internal organelle in the muscle fiber that stores high concentrations of calcium (Ca2+)

t-tubules

‘tunnels’ in the muscle membrane that allow the action potential to travel deep into the fiber to reach the sarcoplasmic reticulum

sarcomere

the basic functional segment of a muscle fiber, containing the ‘sliding filaments’ (actin and myosin)

myofibrils

cylindrical structures within the muscle fiber that contract in response to calcium

proprioception

the ‘body sense’ that informs the brain about the position and movement of limbs in space

muscle spindle (stretch receptor)

located in parallel with muscle fibers; it detects changes in muscle length

intrafusal fibers

the modified muscle fibers inside the spindle, innervated by gamma motor neurons

extrafusal fibers

the standard muscle fibers that provide the actual force of contraction, innervated by alpha motor neurons

golgi tendon organ (GTO)

located in series at the junction of muscle and tendon; it detects muscle tension (force) to prevent injury from overloading

la sensory axons

large, fast axons that wrap around muscle spindels to signal stretch to the spinal cord

lb sensory axons

axons from the golgi tendon organ that signal muscle tension

myotatic reflex

a monosynaptic reflex where stretching a muscle causes it to immediatly contract. it maintains muscle length

reverse myotatic reflex

a reflex mediated by hte golgi tendon organ that causes a muscle to relax if tension becomes dangerously high. it protexts against muscle tears

reciprocal inhibition

a circuit where the contraction of one muscle (agonist) automatically triggers the relaxation of its antagonist muscle via an inhibitory interneuron

flexor reflex (withdrawal reflex)

a polysynaptic reflex used to quickly pull a limb away from a painful stimulus

crossed-extensor reflex

complements the flexor reflex; when one leg lifts (flexes), the opposite leg extends to provide balance so you don’t fall over

central pattern generators (CPGs)

neural circuits in the spinal cord that can produce rhythmic, repeating patterns of movement (like walking or swimming) without constant input from the brain

axial muscles

muscles that control the movements of the trunk

proximal muscles

muscles that move the shoulder, elbow, pelvis, and kneeq

distal muscles

muscles that move the hands, feet, fingers, and toes

somatotopic organization

the arrangment in the ventral horn where neurons controlling flexors are dorsal to extensor, and neurons controlling distal muscles are lateral to those controlling axial muscles

active zone

the specific site on the motor neurons presynaptic membrane where ACh vesicles are clustered and released

motor end-plate

the specialized, ‘frilly’ region of the muscle fiber membrane (sarcolemma) that contains a high density of ACh receptors

sarcolemma

the excitable cell membrane of a muscle fiber that carries the AP

myosin

the ‘thick’ filament that has ‘heads’ which bind to actin to pull the muscle together

actin

the ‘thin’ filament that provides the track for myosin to slide along

sliding filament model

the theory explaining how muscles shorten: the thin filaments slide toward the center of the sarcomere, but the filaments themsevles do not change

alpha-gamma coactivation

the process where the brain sends signals to both alpha and gamma neurons simultaneously. this ensures that as the muscle contracts (alpha), the spindle also contracts (gamma) so it doesnt go ‘slack’ and lose its ability to sense stretch

monosynaptic

a reflex with only one synapse. it is extremely fast

polysynaptic

a reflex involving one or more interneurons

inhibitory interneuron

a neuron in the spinal cord that releases GABA or glycine to ‘shut off’ a motor neuron

excitatory interneuron

a neuron that passes an ‘on’ signal to a motor neuron

amyotrophic lateral sclerosis (ALS)

a disease specifically characterized by the degeneration of alpha motor neurons, leading to muscle wasting and eventual paralysis

noxious stimulus

the technical term for a painful stimulus that triggers the flexor reflex

the thalamic relay

ganglion cells from the retina project to the Lateral Geniculate nucleus (LGN) of the thalamus. this is the first major stop before the cortex

layered organization

the LGN is organized into 6 main layers. it keeps information from the two eyes seperate (each layer receives input from only one eye) but represents the opposite visual field

parvocellular layers (layers 3-6)

‘small cell’ layers. have small receptive fields, are sensitive to color/wavelength, and provide high-detail (photopic-like) info

magnocellular layers (layers 1-2)

‘large cell’ layers. have large receptive fields, are not sensitive to color, but are excelelnt at detecting motion and low-contrast stimuli (scotopic-like)

P cells vs. M cells

retinal ganglion cells named based on whether they project to the parvocellular or magnocellular layers of the LGN

receptive field transformation

while cells in the retina and LGn have concentric (circle) receptive fields, cells in V1 respond to bars and edges

the hierarchical model

V1 ‘builds’ complex images by combining inputs.

simple cells

cells in V1 that respond to a bar of light in a specific orientation and a specific location in the visual cortex

complex cells

cells that respond to a bar of light in a specific orientation, but the bar can be anythwere within their receptive feild

spatial frequency model

an alternative to the ‘bar’ model; suggests the visual system breaks down images into sine wave gratings to analyze texture and detail

trichromatic theory

the idea that color vision relies on 3 types of cones (short, medium, long wavelength) and that any color can be created by a combination of these

opponent-process theory

the idea that we perceive color in oppositves (red vs. green, blue vs. yellow). this explains why we dont see ‘greenish-redish’

modern synthesis of color

we know both theories are right, trichromatic happens at the photoreceptors and opponent-processing happens at the ganglion and cortical levels

spectrally opponent cells (LGN/ganglion)

neurons that are excited by one color and inhibited by another

spectrally opponent cortical cells

located in the cortex (V4); these integrate LGN signals to produce the actual perception of color

V4

the cortical area specifically crucial for processing color and color constancy

two-stream hypothesis

once info leaves V1, it branches into two specialized pathways

V5 (MT)

specialized area in the brain dedicated entirely to the perception of motion

ventral stream (what)

projects to temporal lobe. involved in identifying objects, shapes, and faces

dorsal stream (where/how)

projects to parietal lobe. involved in motion, location, and coordinating movement toward objects

optic ataxia

a condition where a patient can see and reach for an object but cannot name or recognize what it is

orientation column

a column of cells in the vosual cortex that all respond to a bar of light at the same specific angle

ocular dominance column

a region of V1 where the neurons respond more robustly to input from one eye than the otherh

hypercolumn

a complete ‘processing module’ in V1 that contains a full set of orientation columns and ocular dominance columns for a specific spot in the visual field

spatial frequency

rather than just seeing ‘bars’ this concept suggests the brain perceives the world as cycles of light and dark. high spatial frequency = fine detial; low spatial frequency = broad shapes/textures

aperture

a hole or opening thorugh which light travels. in the eye, the pupil servs as the aperture

sensitivity

the ability of the visual system to detect a signal, even at low light levels. larger apertures (dilated pupils) increase sensitivity but decrease resolution

resolution

the ability to pinpoint exaclty where a light signal originated in visual space

inversion

the phenomenon where an image is projected onto the retina completely upside down (top-to-bottom) and reversed (left-to-right)

wavelength

the distance between successive peaks of electromagnetic waves. humans only perceive a specific range of these frequenceis as visible light

retina

the receptive surface at the back of the eye containing photoreceptors and other neurons

photoreceptors

the sensory neurons (rods and cones) that detect light

rods

highly sensitive receptors used for scotopic (night) vision. they are located outside the fovea and do not perceive color

cones

receptors used for photopic (day) vision. they provide high acuity and color vision and are concentrated in the fovea

bipolar cells

retinal cells that receve input from photoreceptors and pass it to ganlgion cells

ganglion cells

the only cells in the retina that produce APs. their axons bundle together to form the optic nerve

horizontal cells

cells that manage communication between photoreceptors and bipolar cells; they are crucial for lateral inhibition

amacrine cells

cells that facilitate communication between bipolar and ganglion cells

fovea

the central region of the retina with the highest density of cones and the sharpest visual acuity

nasal retina

the half of the retina closest to the nose

temporal retina

the half of the retina closest to the temple

optic chiasm

the structure where information from the nasal retinas crosses to the opposite side of the brain, ensuring the left visual field is processed by the right hemisphere and vice versa

lateral geniculate nucleus (LGN)

a part of the thalamus that receives visual info from the optic tract and has concentric receptive fields

visual transduction

process by which light energy is converted into a neural signal. in rods and cones, light causes hyperpolarization (cell becomes more negative), which reduces the release of NT

rhodopsin

the photopigment found in rods that is broken down by light to trigger transduction

opsins

a class of proteins (3 in humans) found in cones that form the basis of color vision

lateral inhibition

a process where interconnected neurons inhibit their neighbors, which sharpens the contrast of borders and edges

range fractionation

a mechanism to handle a wide range of light intensities by using different receptors (rods for low light, cones for high light)

adaptation

the ability of individual photoreceptors to adjust their sensitivity to match the ambient light level

receptive field

the specific area in the visual field to which a particular neuron responds

concentric receptive fields

receptive fields (found in bipolar, ganglion and LGN cells) consisting of a center and an antagonistic surrounc