1. Biological Foundations of Behaviour Flashcards
T or f, action potentials may also move backward through axons in retrograde transmission.
true!
what is the difference between a bipolar and multipolar neuron?
bipolar –> has one dendrite
multipolar –> has more than one dendrite
both only have one axon
what is anterograde movement?
movement from soma (cell body) towards the axon terminus
What is the resting membrane potential? What is responsible for it?
-70mV
the inside of the cell is negative compared to the outside.
maintained by the Na/K ATPase and potassium leak channels
what does the Na/K ATPase do?
it pumps out 3 sodium ions and pumps in 2 potassium ions by hydrolyzing ATP. (primary active transport)
What is an action potential? What is depolarization?
the resting membrane potential is -70mV indicating that the cell is polarized (i.e. there is a difference in charge on either side of the membrane)
An action potential is a wave of depolarization in which this membrane potential is removed by the influx of positive ions (sodium ions).
t or f, the action potential is an electrical impulse
false, it is an electrochemical impulse, since it uses ions and not simply electrons.
Explain what causes depolarization down an axon, briefly.
voltage-gated sodium channels reach a threshold membrane potential of -50mV. They fully open allowing sodium to influx the cell down its concentration gradient. Sodium comes in bringing the MP to around +35mV. a little bit of sodium moves down the axon and slightly depolarizes the next section, bringing the nearby voltage-gated channels to -50mV. This propagates down the axon.
true or false, some of the voltage-gated sodium channels are partly open if the MP is at -60mV.
FALSE - they only open (and fully open) at their threshold of ~ -50mV. This is because an action potential is an ALL or NONE response (no such thing as half-assing it)
quickly after Na+ channels open they inactivate. What happens if another action potential comes?
They do NOT open. they are inactivated until the MP reaches normal again.
What channels help repolarize the membrane?
voltage-gated potassium channels which open at around +35mV an allow K+ to flow out of the cell
What are Schwann cells, what are oligodendrocytes?
Both are myelin-producing cells.
Schwann cells –> PNS
oligodendrocytes –> CNS
Explain saltatory conduction.
myelin sheath has no voltage-gated channels and no depolarization. However, intermittent gaps in myelin called nodes of Ranvier have both these things. membrane depolarization skips myelin sections allowing the action potential to propagate faster.
are all axons myelinated?
no
CNS Glial cells…explain
- astrocytes
- microglia
- Ependymal cells
- astrocytes –> guide neuron development and regulate neurotransmitters
- microglia –> remove dead cells and debris (like an immune cell)
- Ependymal cells –> produce CSF
What is the equilibrium potential?
This is the MP at which a given ion would have no flow based its gradients. (concentration gradient pulls it in, electrical gradient pushes it out)
sodiums is +50mV, potassiums is -90mV.
What is the Nernst equation?
An equation that allows you to find the equilibrium potential for any given ion.
Explain the absolute and relative refractory periods.
absolute RP –> a neuron will NOT fire as the sodium channels are inactivated (not the same as closed). these will become active once the MP is repolarized.
relative RP –> due to hyperpolarization, an AP will only occur if a strong depolarization occurs.
Explain the 7 step process of synaptic transmission at a chemical synapse.
- AP reaches the end of the pre-synaptic axon
- depolarization causes voltage gated calcium channels to open
- calcium influxes the cell and causes exocytosis of nt vesicles.
- nts diffuse into the synaptic cleft
- nts binds ligand-gated channels on post-synaptic neuron
- IF post-synaptic MP reaches threshold, VG-sodium channels open and an AP starts
- nts are degraded, removed, or taken back up.
what is a well known chemical synapse used in muscle?
Neuromuscular junction where acetylcholine is released.
what determines the effect on the post-synaptic cell, the neurotransmitter or the receptor?
The receptor determines the effect on the post-synaptic cell. therefore, a neurotransmitter can act as excitatory and inhibitory
What is an EPSP and IPSP?
These are excitatory and inhibitory post-synaptic potentials. most neurons have multiple axons providing stimuli. The summation of all this stimuli (all the EPSPs and IPSPs) determines whether the post-synaptic neuron will fire.
what are the forms of synaptic summation?
temporal - continuous stimuli adds up
spatial - multiple stimuli at a given point of time
how can a pre-synaptic neuron increase the intensity of its signal to the post-synaptic neuron?
temporal summation (increased AP frequency)
cannot change AP speed or strength, but can increase how often (limited by the absolute refractory period though)
Explain efferent and afferent neurons.
efferent –> cause an effect, therefore they move away from the CNS to the PNS
afferent –> these detect a signal and bring it to the CNS. these are sensory neurons
reflexes, explain reciprocal inhibition (4 steps).
a reflex is a nervous system response without CNS processing.
- a sensory neuron detects a change
- it synapses with a spinal cord motor neuron and a spinal cord interneuron.
- the motor neuron contracts an agonist muscle
- the interneuron inhibits the motor neuron of the the antagonist muscle. causing relaxation of this muscle.
mono-synaptic reflex arc
What causes an erection? what causes an orgasm?
erection is caused by the parasympathetic NS while the orgasm is caused by the sympathetic NS.
what is a nuclei or ganglia
collection of neuronal cell bodies (CNS and PNS)
what is in the hind-brain? What is each part responsible for, briefly?
The hindbrain consists of the..
- Medulla –> connects to the SC. The medulla relays info between brain regions and has many autonomic responsibilities (e.g. blood pressure)
- Pons –> coordinates movement and some autonomic functions
- Cerebellum –> coordinates complex movements
What is the brainstem?
the medulla, pons, and midbrain make up the brainstem
What is the midbrain responsible for?
the reticular activating system (RAS) which regulates arousal and wakefulness. it also relays visual and auditory information
What are the two sections of the forebrain?
- The diencephalon
2. The telencephalon
What is the diencephalon comprised of? What do the parts do?
The diencephalon has two main sections
- The thalamus –> responsible for sensory information integration
- The hypothalamus –> responsible for autonomic functions and hormone control (link between neurons and endocrine system).
What is the telencephalon?
the second part of the forebrain which comprises the two cerebral hemispheres of the brain.
which side of the brain is responsible for language and logic?
left side (think Left = Logical)
right side = creativity
What is the corpus callosum?
A thick bundle of axons (white matter) in the telencephalon which connects the cerebral hemispheres. If you cut this, you would technically have two brains.
What is the cerebrum?
Essentially the telencephalon. The cerebrum is the paired cerebral hemispheres comprised of cerebral cortex.
Explain the 4 lobes of the cerebral cortex and what each does, briefly.
- Frontal lobe –> movement and problem solving
- parietal lobe –> sensory information
- occipital lobe –> visual information
- temporal lobe –> hearing, emotion, and short term memory
Brocas area verses Wernickes area?
Brocas –> speech development
Wernickes –> language comprehension
What is the basal nuclei?
The basal nuclei are located deep within the cerebral hemispheres where they coordinate movement and learning related functions.
How does the basal nuclei work with the cerebellum?
The basal nuclei is a inhibitory regulator of muscle movement.
The cerebellum is an excitatory regulator of muscle movement.
Basal nuclei fine-tunes cerebellum decisions.
What is the limbic system?
responsible for emotion (amygdala) and memory (hippocampus)
how many pairs of cranial nerves exist? How many pairs of spinal nerves?
12 cranial nerve pairs
31 spinal cord pairs
What is a primary parasympathetic cranial nerve?
The vagus nerve which slows down the heart and stimulates the GI tract.
T or f, the cranial nerves are a part of the CNS
false, they carry information to and from the CNS.
Somatic motor neurons –> where are they located, what do they do?
Somatic sensory neurons –> where are they located, what do they do?
motor neurons –> innervate muscle, release Ach, somas found on the ventral side of the spinal cord.
sensory neurons –> somas found in dorsal root ganglias outside the spinal cord.
t or f, efferent ANS systems consist of two neurons.
true, the pre-ganglionic and post-ganglionic neurons.
ANS organization. Where are the preganglionic and postganglionic neurons in general?
preganglionic neurons have their somas within the brainstem or spinal cord (in the CNS). there axons synapse with an ANS ganglion located outside the spinal column. the post-ganglionic axon then sends informatino to an effector organ (muscle, glands)
Sympathetic nervous system: Explain the pre-ganlgionic and post-ganglionic neurons.
where are their somas?
how long are their axons ?
what neurotransmitters do they release ?
Sympathetic nervous system.
pre-ganglionic neuron has short axon that synapses at a ganglion (releasing Ach) just outside the brainstem or spinal cord. The post-ganglionic axon is very long and synapses at an effector with norepinephrine.
Parasympathetic nervous system: Explain the pre-ganlgionic and post-ganglionic neurons.
where are their somas?
how long are their axons ?
what neurotransmitters do they release ?
Parasympathetic nervous system.
pre-ganglionic neuron has a very long axon and snypases (Ach) with a ganglion close to the effector organ. The post-ganglionic axon is very short and releases Ach as-well.
Para-Long-Pre
What region of the spinal cord does the SNS and PNS synapse with?
SNS - Thoracolumbar (middle)
PNS - Craniosacral (very top, very bottom)
What is the function of the adrenal gland (medulla and cortex)?
The adrenal cortex –> responsible for creating cortisol, aldosterone and sex hormones
The adrenal medulla –> upon sympathetic NS stimulation, releases epinephrine which is a short lived hormone that carries out many SNS funcitons, such as increasing heart rate.
What are vestibular hair cells responsible for?
vestibular hair cells within the semicircular canals detect acceleration and position relative to gravity (they help with balance).
What are Pacinian corpuscles?
Pacinian corpuscles are a type of mechanoreceptor that detects pressure and touch in the skin.
How is stimulus intensity perceived by the CNS?
Intensity is determined by the frequency of action potentials. Many APs = more intense signal.
Stimuli duration: explain tonic and phasic receptors.
Tonic receptors continue to send signals while the stimuli is present (however they do eventually adapt and reduce signalling frequency a lot; like clothing on your body)
phasic receptors fire once and then stop (they don’t continue with stimulation; i.e. adapt immediately)
Caveat: pain-receptors do not adapt because the body needs to deal with that stimulus.
What is proprioception and proprioreceptors?
proprioception refers to awareness of self. Any receptors that monitor yourself (muscle spindle) are proprioreceptors.
What are olfactory bulbs and where are they located?
olfactory bulbs synapse with olfactory nerves to detect smells. olfactory bulbs are found in the temporal lobe near the limbic system (this is why smells are connected with memories).
What divides the outer ear from the middle ear?
The tympanic membrane (eardrum)
What three bones comprise the ossicles of the middle ear?
the malleus, incus, and stapes
t or f, the oval window, attached to the stapes, separates the middle ear from the inner ear.
true
What does the auditory tube (eustachian tube) do?
The auditory / eustachian tube connects the throat to the middle ear, and is responsible for equalizing pressure on both sides of the tympanic membrane (ear pops)
Explain, briefly, the mechanism of hearing starting with sound waves hitting the tympanic membrane (n= 5) hints 2. ossicles 3. cochlea fluid 4. basilar membrane 5. tectorial membrane
- sound waves hit ear drum
- the ossicles feel these vibrations and pass them down the line: malleus to incus to stapes
- the stapes vibrates the oval window which sends pressure through the perilymph and endolymph (fluids in the cochlea).
- fluid then vibrates the basilar membrane of the cochlea, which is covered with hair cells
- the cilia of the hair cells contact the tectorial membrane. pressure against this membrane causes the opening of ion channels which results in nt release resulting in nerve signals to the CNS
t or f, the bones of the middle ear, ossicles, amplify vibrations from sound.
true!
What is the Organ of Corti?
The Organ of Corti comprises the actual ‘hearing’ part of the ear: basilar membrane, tectorial membrane, and hair cells.
Pitch is the frequency of sound. How is it detected in the cochlea?
High frequency detected at its base
Low frequency detected at its apex
What determines loudness?
The amplitude of sound waves (frequency is pitch)
if the afferent neuron of the ear starts sending the brain increased AP frequency, how is this perceived?
Increased frequency of the afferent neuron indicates increased intensity which indicates increased volume. (don’t confuse AP frequency with sound wave frequency)
a change in sound wave frequency would stimulate different regions of the cochlea and thus, different nerves.
What is the choroid of the eye?
The layer just beneath the sclera (white of the eye) which absorbs excess light with darkly-pigmented cells.
What do ciliary muscle of the eye do?
The ciliary muscles change the curvature of the lens, to ensure that light focuses perfectly the fovea of the retina.
t or f, light passes through the lens, travels through the vitreous chamber, hits rods and cones of the retina. rods and cons synapse with bipolar cells which then synapse with ganglion cells whose axons comprise the optic nerve.
True
rods/cons –> bipolar –> ganglion nerves
t or f, the optic disc is known as the blind spot.
true, since no cones or rods are found here. (optic disc = convergence of all ganglion cell axons)
What is the macula of the eye? What is the fovea?
The macula contains most of our photo-receptors. At the center of the macula is the fovea, which only has cones (detect color).
Rods and cones contain opsin proteins that associate with retinal (derived from Vitamin A). Explain what happens with retinal in the dark and in the light. How does depolarization of photo-receptors affect ON-center and OFF-center bipolar cells?
In the dark, rods and cones are resting. In the dark, retinal has several trans bonds and 1 cis bond. In this form, retinal combines with opsin and keeps sodium ion channels open which keeps the cell depolarized.
Upon stimulation of light, retinal obtains an all-trans form. This causes sodium channel closure, repolarizing the cell. Now repolarized, their glutamate release to bipolar cells stops.
ON-center bi-polar cells -> inhibited by glutamate. In the dark they are inhibited and do not fire.
OFF-center bipolar cells -> activated by glutamate. In the dark they activate and synapse with ganglion cells
what receptor perceives dim light?
rods
What is emmetropia, myopia, and hyperopia?
emmetropia = regular vision myopia = nearsightedness, light converges before the retina hypertropia = farsightedness, light converges after the retina
How do you fix myopia and hyperopia?
Recall that the lens of the eye is convex and bends light inward.
Myopia = light converges too quickly, need a concave lens hyperopia = light converges to late, need a convex lens
Accommodating is the ability to change the lens with your ciliary muscles. What is presbyopia?
The inability to accommodate.
Briefly, what is feature detection theory?
the concept that different parts of the brain are specialized at detecting different basic features. This is why different parts of the brain light up when looking at faces verses cars.
What is parallel processing?
many different forms of visual stimuli are processed simultaneously (color, edges, size) and separately before being put together.
binocular cues, what is retinal disparity ?
retinal disparity = both retinas perceive slightly different images. Our brain combines these to interpret distance and depth.
The greater the difference in retinal disparity, the closer the object
binocular cues, what is convergence?
convergence is simply the extent to which your eyes turn inwards (converge). If convergence is high, the object is close.
Several monocular cues also exist that help with depth perception (relative size, clarity, motion, etc).
What is the absolute threshold for some stimulus? What is the difference threshold?
The absolute threshold is minimum stimulus needed to activate the sensory receptor 50% of the time.
The difference threshold is the minimal difference in applied stimulus needed to detect a change in that stimulus, 50% of the time.
What is Weber’s Law?
two stimuli must vary by a constant proportion to detect a change between the two. The constant proportion is different for different stimuli.
Two objects must differ by 2% in weight
Two lights must differ by 8% in intensity
What is signal detection theory?
n=4
signal detection theory tries to explain when someone will detect the presence of a stimuli amongst other stimuli (noise)
- hit: stimuli and perceived
- miss: stimuli and not perceived
- false alarm: no stimuli, but perceived
- correct rejection: no stimuli, not perceived
What is gestalt psychology?
Gestalt psychology is the concept of perceiving something as its whole rather than a sum of it’s individual parts. For example, when we look at a face we see a face, not eyes + a nose + a mouth. Gestalt concepts can be applied to any modality, most often, optics.
Gestalt principles: emergence?
Emergence: the Gestalt principle where we first identify an objects outline and shape before seeing any details. the whole image emerges before the individual parts.
Gestalt principles: Figure / ground?
this is the Gestalt principle where once an object has emerged, that becomes the figure while everything else becomes the background. We focus on one thing at a time.
Gestalt principles: Multistability?
Multistability explains ambiguous images continuously interchange in our minds (switch from figure to ground and back again). E.g. the penrose triangle
Gestalt laws of grouping: the law of proximity and the law of similarity?
law of proximity –> things that are near each other are grouped together
law of similarity –> things that are similar are grouped together.
Gestalt laws of grouping: the law of continuity?
the law of continuity –> we perceive things that have continuous lines or shapes not dis-jointed ones. Venn diagram we see two circles overlapping.
Gestalt laws of grouping:: the law of closure and law of common fate and law of connectedness?
closure –> our brains will fill in missing gaps
common fate –> objects moving in the same direction are perceived as a group (dancers)
connectedness –> things that are joined or linked are seen as their own unit
Bottom-up processing vs top-down processing?
bottom-up: relieve some stimuli, this goes up to the brain where it is integrated. this occurs when we experience new things.
top-down: Receive a signal and we retrieve old information in our head.
we constantly use both
