Nervous System Flashcards
describe the structure of a neuron**
dendrite that receives the signal
cell body(soma) that contains the nucleus
axon hillock where the action potential starts
axon is the conducting fibre
what does myelin do for the axon
increases the rate of transmission by insulating the electrical impulse
grey vs white matter
grey = cell bodies
white - myelinated axons
how is myelin made
Schwann cells in the PNS
oligodendrocytes in the CNS
what is saltatory conduction
action potential jumps from one node of ranvier to another to speed up the signal in a myelinated axon
how is the resting potential generated in a neuron
Na/K pump moves 3 Na out of the cell and 2 K in
inside becomes more negative and outside more positive
the rate Na passively diffuses back into the cell increases until it equals the rate its pumped out, K diffuses out of cell due to concentration gradient until it equals the force of the electrochemical gradient (wants to come in because inside is - charge)
when rates reach equilibrium a relative excess negative charge becomes present inside the membrane compared to outside
why can the equilibrium potential of K be used to approximate the resting potential of a neuron
at rest neuron is much more permeable to K
K is leaking out so positive charge is escaping
about -60-70 in the cell
how can the Nernst equation be used to calculate the resting potential of a neuron
take the negative ln of the ratio of Kintracellular/Kextracellular
so if intracellular>extra the ln will be positive so the answer is a negative membrane potential
and if extra>intra the ln will be negative so the answer is positive
where would electrical synapses be found
these are fast so would be in cardiac and visceral smooth muscle
how do chemical synapses use neurotransmitters to initiate a new action potential in a different cell*****
- small vesicles filled with neurotransmitter rest inside the presynaptic membrane of the synaptic knob
- when action potential arrives Ca voltage gated channels open allowing Ca influx
- influx causes neurotransmitters to be released into the synaptic cleft via exocytosis
- neurotransmitter diffuses across the synaptic cleft by Brownian motion and attaches to receptors on the postsynaptic neuron
- post synaptic neuron becomes permeable to ions which move in to generate a new action potential
depolarization of a action potential
voltage gated channels open at a certain voltage
voltage gated sodium channels allow Na to flow into the cell making it more positive
how do local anesthetics work
block voltage gated Na channels on primarily pain neurone because they have small axonal diameters with little myelin
what happens at threshold potential -50
even more Na can enter through positive feedback mechanism
the action potential propagates along the membrane by depolarizing adjacent sections
cell becomes +50
depolarization of the action potential
K flows out of the cell increasing the negativity in the cell
hyper polarization of the action potential
K channels are slow to close and the the inside of the cell becomes more negative than the resting potential and prevents the immediate initiation of a new action potential
summation is the process in which most important stimuli get screened and acted upon, what are the 2 types
spatial: multiple dendrites receive input at the same time and those are summed up
temporal: single dendrite receives many signals and these inputs are summed up
what are glial cells
cells that support the nervous system
not involved in transmitting signals
outnumber neurons big tiime
what are the 6 glial cells you must know
ependymal cells - epithelial cells which line space containing CSF
astrocytes - star shape, physical support for neurons in CNS
oligodendrocytes - create myelin in CNS
microglia - like macrophages of the CNS
satellite cells - support ganglia in PNS
Schwann cells - make myelin in PNS
CNS consists of
brain and spinal cord
what are afferent neurons
sensory , come in from periphery
what are the 5 types of sensory neurons
mechanoreceptors - touch thermoreceptors - temperature nociceptors - pain electromagnetic receptor - light chemoreceptors - taste, smell
interneurons are the most prevalent neurons what do they do
transfer signals from neuron to neuron
what are efferent neurons
motor
carry signal from CNS to the effector
sensory vs motor neuron location
sensory - dorsal from the spinal cord
motor - ventral from the spinal cord
3 components of the brain stem
midbrain - auditory and visual
pons - transfer motor info from pre motor cortex to cerebellum
medulla - regulate cardiovascular, respiratory, blood pressure**
what does the cerebellum do
coordinates and plans movement
receives sensory motor and vestibular input
what is the peripheral nervous system and the 2 components
responsible for sensory and motor functions
somatic system - innervates skeletal muscle , can process sensory info and controls all voluntary muscle systems. also reflex actions
autonomic system - involuntary and affects the smooth muscle, cardiac, and glands
how does the sympathetic nervous system work
preganglionic neurons emerge from thoracic and lumber regions of spinal cord and use Ach
postganglionic use norepinephrine when they synapse on their effectors
preganglionic are shorter than postgang
how does the parasympathetic nervous system work
both preganglionic and post use acetylcholine as their neurotransmitter
long preganglion short post
what are the 2 types of photoreceptors in the eye
rods - light
cones - color
what is the only sense that isn’t regulated through the thalamus
smell
how does the middle ear transmit sound
level system of malleus, incus, and stapes translates the sound wave to the oval window of the cochlea
what does the cochlea in the inner ear do
detects sound
what so the semicircular canals of the ear do
detect orientation and movement of the head
what type of receptors does the skin have
somatic - for external environment
proprioceptive - sense relative position of neighbouring parts of the body
nociceptive - pain
What does the thalamus do
Control centre or weigh station
Processes sensory info before it reaches higher cortical centres
Receives motor demands from cortical areas on the way to the spinal cord
What does the hypothalamus do
Regulates body’s basic physiological needs by maintaining homeostasis
