Bio Class 7 Flashcards
_____ send impulse towards soma, while _____ send impulse away from soma
dendrites, axon
Nodes of Ranvier
“saltatory conduction”
- propagation of AP along myelinated axons from one node to another, increasing velocity of ap
Axon hillock
Connects soma and axon
- ap starts here
Schwaan cells
Found in PNS, wrap around axon to form myelin
Oligodendrocytes
Found in CNS, wrap around axon to form myelin
Myelin
Insulator, increases speed of conduction
Soma
Performs basic function of cell
Types of neurons
Bipolar, unipolar, multipolar (most popular)
Bipolar neuron
Single axon, single dendrite
- direction determined by direction of impulse
Unipolar
Single process that divides to form axon and dendrite
- direction determined by direction of impulse
Depolarization
Move away from rest in positive direction (-70 to -50)
Hyperpolarization
Move away from rest in negative direction (-70 to -90)
Repolarization
Returning to rest from hyperpolarization or depolarization
Equilibrium Potential
The potential at which there is no driving force on an ion
Action Potential Process
Potential starts at -70
Cell depolarizes as Na+ VG channels open (-50)
Reaches Na+ equilibrium potential (+35)
Na+ channel is inactive and K+ VG channel opens
Cell hyperpolarizes
Na+ VG channel shifts to “closed”
K+ channel closes
What is the resting membrane potential?
-50 mV
Absolute refractory period vs relative refractory period
Absolute
- Na+ channel is inactive, cell is too positive
- impossible to fire a second potential
Relative
- Na+ channel is closed, cell is too negative
- close to K+ eq potential
Nerve impulse
Action potential travelling
Synapse
Once signal reaches end of neuron, signal goes to different cell or neuron
If there is a impulse from A –> B –> , why would the AP go towards C and not A?
Because A is in the refractory period
What happens to B and C if A is going through an AP?
Na+ is entering A and the membrane potential of B and C is at -70
- then charge from A reaches B and depolarizes it
- Once B reaches threshold, it’ll fire an AP
Electrical Synapses vs Chemical synapses
Electrical synapse
- Gap junctions
- Unregulated
- Bidirectional
- Always excitatory (always causes AP in postsynaptic cell)
* Relatively rare & found in cardiac muscle cells
Chemical synapse
Opposite of electrical synapse
- Presynaptic neuron has neurotransmitters in vesicles that are bound by synapsin (cytoskeleton filaments)
- When VG Ca2+ channel reaches threshold, it breaks down synapsin
- Vesicles are released and neurotransmitters float in synaptic cleft
- Receptors on post-synaptic dendrite will bind to some neurotransmitters
1. Neurons make one type of NT, but respond to many
2. NT in cleft can be recycled or broken down, medication can change amount of time it spends in cleft
3. Response of post-synaptic cleft depends on receptors
4. takes more than one vesicle of neurotransmitters to elicit a significant response on post-synaptic cell
EPSP
Excitatory post synaptic potential
- when one vesicle dumps into post-synaptic cleft
- If AP comes and dumps lots of vesicles, it will add up and eventually membrane reaches threshold and causes AP
IPSP
Inhibitory Post Synaptic Potential
- Adds up and eventually membrane hyperpolarizes
Summation
Adding EPSP and IPSP
- Spatial - add multiple inputs over wide area
- Temporal - add frequent impulses from a single source
_______ increases intensity in neurons
frequency
General System function of neurons:
______ –> _______ –> _______
Sensory input —> Integration —> Motor output
Sensory input: sensory neurons, afferent, PNS
Integration: making decision, interneurons, CNS
Motor output: motor neurons, efferent, PNS
Reflex
rapid integration to avoid body injury
Simple Reflex - urine example
- In walls of bladder, there’s receptors that monitor stress & tension
- As bladder fills up with urine, tension builds on the bladder
- the bigger the stretch in the bladder, the more frequent AP
- The sensory neuron senses stretch and in the spinal cord it’ll interact with the motor neuron and then cause the bladder to contract
Complex reflex - hitting tendon example
When you hit the tendon:
- tendon of quadricep muscle stretches, stimulates sensory neuron
- activates quadricep muscle, causing it to contract and inhibit motor neuron of hamstring, causing hamstring to relax
Spinal cord
Primitive reflexes
Medulla
Regulates basic vitals
Pons
balance/movement
Diencephlon
Hypothalamus
- maintains homeostasis, controls the pituitary
Thalamus
- sensory relay station, sends to proper brain region for processing
Epithalamus
- includes pineal gland which produces melatonin (sleep/wake cycles)
Telencepholon
Cerebrum or cerebral hemisphere
Limbic system
Emotions and LTM
Cerebellum
Coordinate and smoothe body movements
Midbrain
Startle reflexes
White matter vs Grey matter
White matter - composed of myelinated axons - involved in cell-to-cell communication CNS-brain: tract CNS-spinal cord: tract/column PNS: nerve
Grey matter - composed of cell bodies - involved in integration CNS-deep brain: nucleus CNS-brain surface: cortex CNS-spinal cord: horn PNS: ganglion
Nervous system flow chart
Nervous system breaks into CNS and PNS
CNS: spinal cord and brain
PNS: all nerves and sensory structures outside of brain & spinal cord
PNS breaks into Somatic and Autonomic
Somatic: voluntary control of skeletal muscle
Autonomic: involuntary control of glands & smooth muscle
Autonomic breaks into Sympathetic & Parasympathetic
Sympathetic: fight or flight
Parasympathetic: rest and digest
Somatic vs Autonomic
- neurotransmitters?
- excitatory and/or inhibitory?
- how many motor neurons??
Somatic
- NT: Ach
- 1 motor neuron that connects CNS to skeletal muscle
- excitatory
Autonomic
- NT: Ach, NE
- 2 motor neurons that connect CNS to effector organ
- excitatory or inhibitory
Parasympathetic vs Sympathetic
Para
- decreases BP, resp rate, HR
- increases digestion
- bronchioles constrict, pupils constrict (less o2 needed while sleeping with close field of vision)
Symp
- increases BP, resp rate, HR
- decreases digestion
- bronchioles dilate, pupils dilate (more o2 needed while needing far field of vision
- direct stimulation of adrenal medulla which produces epinephrine which prolongs response of sympathetic nervous system
Difference between NE and Epi?
NE is a NT that’s produced in timely quantities in cleft, acts locally
Epi is a hormone that’s produced and released in blood & acts throughout whole body
Types of Sensory Receptors
Mechanoreceptors - mechanical stimuli Nocireceptors - respond to pain Chemoreceptors - respond to chemicals Photoreceptors/electromagnetic receptors - respond to light Thermoreceptors - respond to temperature
Iris
Coloured part of your eye, regulates diameter of pupil
Pupil
Black opening in middle of eye
Lens
Biconcave structure that focuses light on retina
Retina
Sensitive to light and a layer at the back of the eye
Ciliary muscle
Controls the curvature of lens
Cornea
External transparent layer of eye
Fovea/cones
Responsible for extreme visual acuity
Absolute Threshold
minimum amount of stimulus needed to trigger receptor
Difference threshold
how much change in a stimulus before it’s noticed
Sensory Adaptation
receptors stop responding to continuous stimulus
- pain & sexual receptors don’t adap
Bottom up processing vs top down processing
Bottom up
- Sensory receptor
- Sends info to brain
- Analyze and process
Top down
- Use prior knowledge & expectations
- Analyze sensory info
Optic disc
Blind spot, place on retina where optic nerve forms
Optic nerve
bundle of axons leaving eye towards brain
Organization/flow from retina
Photoreceptors (rod/cone cells) –> bipolar cells –> ganglion cells –> ganglion cells become optic nerve –> occipital lobe for image processing
Rod vs cone cells
Cone
- concentrated in fovea
- colour vision (red, blue, green)
Rod
- in periphery
- black and white
- lower level of light
- more abundant than cone cells
When light is present…
- Inhibition of Na+ channels
- Na+/K+ pump polarizes cell
- Stop release of neurotransmitter (glutamate)
- Bipolar cell inactive so no AP/ bipolar cell is active so AP to brain
When light is absent…
- Na+ channel open
- Na+ enters and depolarizes cell
- Cell releases neurotransmitter into cleft (glutamate)
- Activated so AP to brain/ inactivated so no AP to brain
Structure of the ear
Outer ear
- Pinna
- Auditory canal
Middle ear
- tympanic membrane
- 3 bones: malleus, incus, stapes
Inner ear
- semicircular canals
- Cochlea
- Eustachian tube (auditory tube)
Eustachian tube
Contains a flap that’s normally closed but opens when middle ear wants to equilibrate with atmospheric pressure
Mechanism of hearing
- Sound waves come from outside the ear, channels through auditory canal & reaches tympanic membrane
- Tympanic membrane vibrates and causes 3 ossicles to vibrate which reaches oval window
- Oval window transmits vibration through liquid of cochlea (outer fluid)
- Pressure waves are then converted to AP and sent to brain to get deciphered…
- Pressure waves in endolymph & perilymph lead to vibration of the basilar membrane and movement of hair cells
- Cilia on hair cells dragged across tectorial membrane
- Hair cells get bent & release NT into cleft
- Binds to receptors on auditory neuron which transmits signal to brain
Pitch vs Loudness
Pitch: determined by region of basilar membrane most stimulated
Base of basilar membrane = high frequency, high pitch, high energy, thick and stiff
Apex of basilar membrane = low frequency, low pitch, low energy, thin and floppy
Loudness (=amplitude): determined by frequency of AP reaching the brain
soft = less AP
loud = more AP
Vestibular complex
‘Equilibrium & balance’
- Semicircular canal - rotational balance
- Vestibule - saccule, utricle, ampulla = static balance
