Week 2 midterm 2 Flashcards
What is a reflex arc?
neural pathways for reflexes
What is the muscle spindle stretch reflex?
the reflex pathway in which muscle stretch initiates a contraction response
What are the 5 neural pathways of a reflex arc?
- stimulus*
1. sensor receptor
2. afferent neuron
3. integration center
4. efferent neuron
5. effector organ - response*
Spinal reflexes require what?
require NO input from the brain
Cranial reflexes require what?
require input from the brain (integrated from within)
Innate reflexes
Genetically programmed in everyones body
Conditioned reflexes
learned reflexes - acquired through experience
Monosynaptic reflexes
Have 2 neurons - afferent and efferent (only somatic motor reflexes)
Somatic motor reflexes
Controls the effector - controls skeletal muscles (efferent)
Autonomic reflexes
Controls the effector - control smooth and cardiac muscle, glands and adipose tissue (efferent)
Polysynaptic reflexes
One or more interneurons between afferent and efferent neurons (all autonomic reflexes – have 3 neurons)
What is the stretch reflex (aka knee-jerk reflex)
only known monosynpatic reflex
- receptor is a muscle spindle that detects lengthening of the muscle
- tapping the patellar tendon below the knee cap causes the quadriceps in the upper thigh to stretch which excites the muscle spindles, therefore generating AP’s that travel to the spinal cord
What are muscle spindles
stretch receptors that send info to the spinal cord and brain about muscle length and changes in it
What are proprioceptors?
sensory receptors in the subcutaneous tissues that detect motion and position of the body through a stimulus produced within the body (in muscles and joints)
What do extrafusal muscle fibers do?
receptor for stretch and force – most of the muscle and are the major force-generating structure (larger than intra)
What are intrafusal muscle fibers?
found within each muscle spindles, contain afferent receptors for stretch and contractile elements on the ends (smaller than extra)
- central region lacks myofibrils
What is the central region of an intrafusal muscle fiber composed of?
no myofibrils, wrapped with sensory nerve endings stimulated by stretch
What is muscle tone?
the amount of tension in muscles (even a little bit present at rest)
What do sensory neurons do? (X3)
- get activated by sensory input from the environment
- send AP’s to the spinal cord
- continuously activate motor neurons keeping the muscle at a tone
What happens when spindles/muscles stretch?
- causes sensory fibers to fire more rapidly
- more AP generated
- creates a reflex contraction to prevent damage
What keeps muscle spindles alive?
gamma motor neurons
What keeps muscle spindles alive/tense/give them tone?
gamma motor neurons
What do alpha motor neurons do?
largest neurons in the spinal cord, innervate (provide nerves) extrafusal muscle fibers and are directly responsible for initiating their contraction
What are the 4 key things for a successful completion of a voluntary motor task
- development of an idea to move
- putting together a program of motor commands for the movement
- executing the movement
- constant feedback to ensure it was smooth and successful
What does the spinal cord do?
it integrates spinal reflexes and contains central pattern generators
What do the brainstem / cerebellum do?
control postural reflexes and hand / eye movements
What does the cerebral cortex and basal ganglia do?
they are responsible for voluntary movements
What does the thalamus do?
relays and modifies signals (manager) as they pass from the spinal cord, basal ganglia and cerebellum to the cerebral cortex
What do central pattern generators (CPG’s) do?
maintain spontaneous repetitive activity
- neural circuits
- walking, swimming, breathing or chewing
Voluntary movement requires coordination between what 3 things?
- cerebral cortex
- cerebellum
- basal ganglia
Voluntary movement requires coordination between what 3 parts of the body?
- cerebral cortex
- cerebellum
- basal ganglia
Voluntary movement requires what 4 things?
- knowledge of the bodys position
- a decision to execute
- a plan for execution
- memory of that plan
Limbic system is related to what step of voluntary movement?
idea
Association areas are related to what step of voluntary movement?
idea
Supplementary motor area is related to what 2 steps of voluntary movement?
idea / program
Premotor area is related to what step of voluntary movement?
program
Primary motor cortex is related to what step of voluntary movement?
program
Pyramidal tract is related to what step of voluntary movement?
execution
Extrapyramidal tract is related to what step of voluntary movement?
execution
Motor neuron is related to what step of voluntary movement?
execution
Sensory systems are related to what step of voluntary movement?
feedback
Cerebellum is related to what step of voluntary movement?
feedback
Thalamus is related to what step of voluntary movement?
feedback
Basal nuclei are related to what step of voluntary movement?
feedback
Brainstem is related to what step of voluntary movement?
feedback
What does the pyramidal tract neuron do?
it controls distal extremities: hands, toes, fingers, etc (distal = further away than proximal)
- takes info from upper motor neurons in the cortex and direct lower motor neurons in the spinal cord (directly connected or indirectly connected with interneurons)
- one pathway
- voluntary movement
Why don’t horses have very developed pyramidal tracts?
cause they don’t have hands or toes
Where is the upper motor neuron and what does it do? How does it respond to signals?
- located in the spinal cord
- always excitatory
- receives signal from the upper motor neuron: fires an AP and muscle contracts
- receives no signal: nothing happens, muscle stays at rest
What do extrapyramidal tract neurons do and what kinda inputs do they have?
pathways outside pyramidal tracts
- support voluntary movement of proximal extremeties (closer to the body than distal)
- controls movement of the trunk, neck and legs
- involuntary movement
- indirect input only
What are the 3 pathways for extrapyramidal tracts and where do they go?
- rubrospinal (red): midbrain to spinal cord
- vestibulospinal: vestibular nuclei to spinal cord
- reticulospinal: medualla oblongata to spinal cord
What does the body use for involuntary control over posture?
receives info from the eyes and ears (vestibular system)
- sensory receptors in the skin
- muscles and joints (proprioceptors)
What is the role of the cerebellum? (x4)
- compares actual to planned movements (regulation of motor coordination)
- stores programs for remembered motor activities
- informs the cortex to make corrections
- contributes to muscle tone
Do herbivores or omnivores/carnivores tend to sleep longer/more?
Carnivores/omnivores
What is the definition of sleep?
a reversible and normal suspension of consciousness
- active process: requires E
What are the most likely reasons for sleep?
- hypotheses why
- conserve E (best/most likely reason)
- allows the body to repair itself
- process memories
- lets brain rest/restore energies
- helps the immune system function
- clearing waste out of the cerebral spinal fluid (especially proteins)
- helps improve performance on tasks and tests
What is electroencephalography?
the electrical activity of the brain
- uses metal discs
- EEG
What are the 4 stages of sleep?
W: wake stage
REM: rapid eye movement
N1,N2,N3: slow wave or non REM
What is REM sleep (rapid eye movement) stage R?
- every 90 mins
- beta waves
- associated with dreaming
- most likely to wake up during
- eyes move and brain is active
- starts 90 mins after falling asleep and the phases of it get longer throughout the night
- characterized by waves with low amplitude and high frequency
- paralyzes skeletal muscles
What are stages N1 and N2 of non-REM?
- theta waves
- N1 = lightest stage of non-REM sleep
- N2 deeper than N1
What is N3 stage of non REM?
- slow wave / deep sleep
- delta waves
- most difficult to awaken
- high amp, low frequency (opposite to REM)
- adjust body position without command from the brain
Towards the end of sleeping, what stages do you spend in most?
REM and N1
What stages of sleep are you in at first?
N1 and N3
What controls circadian rhythm?
the hypothalamic biological clock
What does the biological clock do?
causes changes in the level of wakefulness in response to day/night cycles
What is the ascending reticular activating system (ARAS)?
part of the reticular formation that projects to the thalamus, hypothalamus, and forebrain; signals to the entire brain, most prominently in the cortex
What does the forebrain do in respects of sleep?
Induces non-REM sleep (N1,2,3)
What 3 groups of neurons are involved in sleep-wake cycles?
noradrenergic (norepinephrine), cholinergic (acetylcholine) and serotonergic (serotonin)
What drugs are high during wakefulness and low during sleep?
norepinephrine, serotonin and orexin
What drugs are high during wakefulness and REM but low during non-REM?
acetylcholine and dopamine
What are the 4 steps to falling asleep?
- nerves from the eye signal the suprachiasmatic nucleus (SCN) that the light level is decreasing
- SCN stimulates the ventrolateral preoptic nucleus
- VPN decreases the activity of the reticular formation
- decreased activity causes the thalamus to disconnect from the cerebral cortex. therefore decreasing the level of conciousness
What is the suprachiasmatic nucleus (SCN)?
it recieves signals from the eye that light is decreasing and stimulates the ventrolateral preoptic nucleus
What are orexins and what do they do?
a neurotransmitter that increases before wakening and maintains a state of wakefulness
- stimulates reticular formation which in turn stimulates the thalamus to send an external sensory stimuli to the cerebral cortex
What triggers arousal?
orexin, and the activation of cholinergic and noradrenergic pathways
What are some things that sleep loss can cause?
- imbalance in temperature
- weight loss
- weakened immune system
- decrease in cognitive abilities
- hallucinations (humans)
- death
During infection, what stage of sleep is increased and decreased?
increased: N3
decreased: REM
What microbial components mimic the sleep effect?
lipopolysaccharide (LPS) and muramyl peptides
What interleukins can cause an increase in non-REM sleep?
increases in the intracverebral or plasma levels of the TNF or IL1
What are sensory receptors and how do they work?
they are specialized nerve endings that separate cells that detect a sensory stimulus or a specific form of energy
What are visceral afferents?
receptors that gather info from the visceral organs (heart, lungs, liver, pancreas, intestines, etc.)
What is the afferent branch?
a branch of the peripheral nervous system that carries info from the periphery to the CNS
What 2 sensory systems allow us to perceive the external environment?
- somatosensory system
2. special senses
What does the somatosensory system do?
a sensory network that monitors the surface of the body and its movements
What are the 5 special senses
- vision
- hearing
- balance/equilibrium
- taste
- smell
smell = neurons // rest = nonneural (synapse onto sensory neurons)
What are the 3 receptors and which have myelin
pain (no myelin)
touch (myelin)
ear hair (myelin)
What is the pacinian copuscle?
a touch receptor that detects transient pressure and higher frequency vibrations
Where are free nerve endings found?
in the skin and other tissues
What are chemoreceptors?
chemical sensors in the brain and blood vessels that identify chemical ligands that bind to it (O2, H, glucose… etc.)
What are mechanoreceptors?
sensory receptors responsible for sensing mechanical E due to distortion in body tissues such as pressure, cell stretch, vibration, acceleration and sound
What are baroreceptors?
sensory receptors that sense pressure changes
What are osmoreceptors?
sensory receptors that sense cell stretch
What are thermoreceptors?
sensory receptors that respond to varying degrees of heat (cold/hot)
What are photoreceptors?
sensory receptors that respond to photons of light (for vision – detect light waves)
What is transduction?
the process of conversion of the stimulus energy into electrical energy or graded potentials (transfer of E from one form into another)
What is modality?
the E form of a stimulus (light/sound waves, pressure, temp, chemicals, etc) – receptors specific to one type
What is an adequate stimulus?
the modality to which a receptor is most sensitive, and therefore best responds to
What causes graded potentials?
the opening and closing of ion channels (if greater than threshold, triggers an AP) – increased stimulus increases the amplitude of a graded potential
What is adaptation?
a decrease in the amplitude of a receptor potential over time in presence of a constant stimulus
- decrease in the frequency of the AP
- decreases perception of the stimulus
How do most receptors respond to a stimulus?
some continue to respond for the full time its applied but MOST adapt to it and their response declines with time
Why do we get used to scents?
because olfactory receptors are rapid adapting receptors
What is the first order neuron?
the afferent neuron that transmits info from the periphery to the CNS
What are second order neurons?
interneurons that transmit the info to the thalamus
Where is the visual cortex located?
in the occipital and temporal lobes
Where is the gustatory cortex located and what does it do?
an area of the brain that receives and interprets tastes from the tongue – located partly on the frontal lobe
What is the somatosensory cortex and where is it?
an area at the front of the parietal lobe that registers and processes body touch and movement sensations
What is the vestibular cortex and where is it located
posterior part of the insula and adjacent parietal cortex – is responsible for conscious awareness of balance (head position in space)
Where is the olfactory cortex and what does it do?
located on the inferior surface of the frontal lobe – detects smell
What is the auditory cortex and where is it located?
temporal lobe – responsible for processing sound info
What do third order neurons do?
synapses form between them and second order neurons in the thalamus and they transmit info to the cerebral cortex
What is stimulus intensity coded by?
frequency (stronger stimulus results in a larger receptor potential) and population coding (stronger stimulus activates/recruits a greater number of receptors)
What is the definition of vision?
the process through which light reflected from object in our environment is translated into a mental image
What do photoreceptors do?
transduce light energy into an electrical signal in the retina
What do neural pathways in the retina do?
process electrical signals into visual images
What is the eye
a fluid filled organ
What is the outermost layer of the eye composed of and what does it do?
- sclera and cornea
connective tough tissue (white in colour)
What is the middle layer of the eye composed of and what does it do?
- choroid
gives nutrients for retina
What is the innermost layer of the eye composed of and what does it do?
- retina (photoreceptors – rods and cones)
perceives light
How does blood enter and leave the eye?
enters: arteries
leaves: veins
What does the lens do?
takes light and focuses it into the retina
What does the pupil do?
regulates the amount of light that enters the eye
What does the iris do?
2 smooth muscles that regulate the diameter of pupil and regulates amount of light that enters the eye (pigment that gives the eye its colour)
What does the cornea do?
connective transparent tissue – allows light to enter the eye
What do the zonular fibers/cilary body?
muscles that connect ligaments to the lens and change the size/focus of lens into the retina
What is the sclera?
An outside connective tissue
What is the fovea?
the region of sharpest vision (all cones)
What do zonules do?
they attach the lens to the ciliary muscle
What does the canal of schlemm do?
takes aqueous humour (fluid) and removes it
What causes glaucoma?
when liquid accumulates and the pressure damages the chamber (damage to the optic nerve)
What is the choroid?
it has blood vessels that nourish the retina
What maintains the shape of the eye?
vitreous chamber
What is the range of visible light?
380-750nm
How does wavelength relate to energy?
opposites: increase wavelength, decrease E (vv)
What can a cat see?
blurry during the day and sharp at night – can’t see red and green
What can a bird see?
red, green, blue and UV
What can a cephalopod see?
completely colour blind - shades of gray
What can a snake see?
low res during the day and good night vision - can see infrared
What is the inner circular muscle?
constrictor
What is the outer radial muscle?
dilator
What kind of light do animals and humans perceive?
reflected and emitted light
What is refraction of light?
the bending of light, when its speed differs in different mediums (ex. straw in water)
What does the retina do?
at the back of the eye, receives light that the lens has focused, converts the light into neural signals and sends them to the brain for visual recognition (eye computer signal)
- composed of neural tissue
What is the tapetum lucidum?
an iridescent layer found in nocturnal animals for maximizing vision under low intensity light; reflects visible light back through the retina, increasing light available to photoreceptors
What does the outer layer of the retina contain?
rods and cones (photoreceptors) – communicate with bipolar cells
What does the middle layer of the retina contain?
bipolar cells (communicate with ganglion cells), amacrine cells and horizontal cells (a and h cells provide lateral modulation)
What does the inner layer of the retina contain?
ganglion cells (axons form the optic nerve) – first cell in the pathway to generate APs
What is the optic nerve?
bundle of nerve fibers that transmits sensory info for vision in the form of electrical impulses from the eye to the brain
What are rods? and what kinda/how many opsins
responsible for night vision (black and white), more plentiful in the retina, mostly in the periphery of the retina, high degree of convergence with bipolar cells
- shorter than cones
- 1 type of opsin (rhodopsin)
What are cones? and what kinda/how many opsins
responsible for colour and day vision, less plentiful in the retina, mostly in the fovea, low degree of convergence with bipolar cells
- longer than rod and more slender
- 3 types of opsin
Which vitamin greatly affects vision?
Vitamin A
Red opsin
L - responds to 560 (long wave)
Green opsin
M - responds to 530 (medium wave)
Blue opsin
S - responds to 420 (short wave)
What is transducin
the G-protein that couples rhodopsin to the enzyme phosphodiesterase in rod photoreceptors
How is colour perceived?
through cone comparison
How is glutamate used in convergence?
it is the transmitter released from rods and cones that communicates with bipolar neurons
What is melanopsin?
located in ganglion cells – activated by light it sends signals to the SCN/hypothalamus (regulating circadian rhythm)
Where is binocular/monocular vision located?
binocular: directly in front
monocular: periphery
- animals with eyes on the sides of their heads have much more monocular vision than those who are in front
What is the opponent process theory?
cones can detect the presence of a colour because they inhibit the other colour
What is the trichromatic theory?
that each opsin / cone responds best to its own colour
