Nervous system 3 function
-coordinates muscle movement/contraction using electrochemical signals
-sense internal & external environment
-integrates senses to form emotions and sensation
How nervous system works
Receptors receive stimuli sent to by afferent fibers (peripheral) sent to central nervous system then to muscles and glands
Peripheral nervous system PNS consist of? divided into?
nerves and ganalion cells outside brain or spinal cord
-sensory and motor division (motor and glands)
What is the longest nerve in body?
Sciatic Nerve
What are nerves?
Neurons bundle that transmit info to brain/spinal cord and into to muscle and organs
Central nervous system CNS composed of? do?
-consist of brain and spinal cord
-Control center of body
-relay message, process and analyze info
sensory info, generate thought, store memory
3 types of neuron
sensory neuron (PNS)
Interneurons (CNS)
Motor neurons (PNS)
Sensory neurons do and different kind of receptors
Convert external stimuli to spinal cord and brain
Mechanoreceptor- touch, pressure,
Thermoreceptors- temp
Photoreceptor- light
Chemorecptors- chemicals, oxygen, acidic
Nociceptor- pain
Osmoreceptor- concentration of solutes
Interneurons
-relay neurons only in CNS
-form circuits to communicate with each other
-connect sensory and motor neurons and carry impulses between them
Motor neurons
-In CNS but project axons outside CNS to control muscle
-release neurotransmitters that bind to post synaptic receptors
-Carry impulses from brain/spinal cord to muscle and gland
How neurons relay info ?
Info relayed from neuron to neuron using elecrticity and chemical messengers
What are Glia cell or neuroglia?
supportive cell in CNS and PNS
smaller and more # than neuron capable of mitosis
-protect and nourish neurons
-brain tumors more likely from this
Satellite cell
-PNS
-surround neuron cell bodies in ganglia
- prevent injury Regulate O2, CO2, nutrient, and neurotransmitter around neuron in ganglia
Schwann cell
-surround axon in PNS,
-myelination of peripheral axon
-repair process after injury
Oligodendrocytes
-Myelinate CNS axons
-provide structural framework
Astrocytes
CNS
-maintain BBB,
-barrier, prevent injury
- regulate ion, nutrient and dissolved gas concentrations,
-absorb and recycle neurotransmitters
-form scar tissue after injury
Microglia
CNS
Immunity
Macrophage: remove cell debris, waste and pathogen by phagocytosis
Ependymal cell
in CNS
- line ventricles(brain) and central canal (spinal cord). Assist in producing circulating and monitoring of cerebrospinal fluid (CSF)
Neurons have resting potential of ___ due to electrical gradient. What ion is inside/outside
-70 mV
Outside: Na+, Cl-, Ca +
Inside: K+, porteins
difference of cation and anion
Neuron function and structure
excitable cell that conduct info from one part to another via electrical impulse(action potential) conducted along lymph of axon
Cell body (soma)- nucleus and cytoplasm
Dendrites- extensions of PM from cell body, carry impulses from environment or other neuron toward cell body
Axon- carry Infor away from cell body, end at axon terminal
injunction between 2 nerve cell with gap where impulse pass through diffusion
Axon hillock- sum of total signal
synaptic terminal- area where electrical signal is converted to chemical signal
When does neuron travel electrically and when does it travel chemically
Within
Between
Communication between neurons
chemical signals
-chemical synapses release neurotransmitters that work through "lock and key"
How is signal relayed from one neuron to another?
synapse
-Axon terminal, synaptic cleft, dendrite
Process of neurotransmitter release
-Action potential depolarizes the axon terminal
- voltage gated Ca2+ channels
-release synaptic vesicle
-Neurotransmitter diffuse across synaptic cleft and bind with receptor on postsynaptic cell to cause response
Autonomic motor neuron synapse
-onto smooth muscle
release of neurotransmitter (not restricted to acetylcholine) from swelling fiber (varicosities)
-longer travel distance and can bind to any nearby smooth muscle cell unlike NMJ
Major neurotransmitters GABA, Acetylcholine, glutamate, norepinephrine,
Acetylcholine(excitatory). CNS and PNS
Norepinephrine, epinephrine, dopamine (excitatory). CNS and PNS (sympathetic)
Glutamate (excitatory): CNS Brain
GABA (inhibitory): CNS Brain and spinal cord
4 Nervous system ion channels
Ligand(chemically) gated- open by neurotransmitter
Mechanically gated- open by physical force
Always open- ex sodium and Potassium
Voltage gated- respond by changes in membrane potential
Neuronal structure/ function relationship
movement of ions within neuron create 2 types of electrical signals
Graded potential
-variable strength
-sum to cause an AP
Action potential
- all or none
-constant strength
generated at axon hillock
Graded potential
stops at axon hillock
Above -55mV needed to pass trigger zone
short live changes in electrical membrane potential
Excitatory post synaptic potential vs Inhibitory
Excitatory post synaptic potential-presynaptic neuron release glutamate neurotransmitter. cause positive shift Na+ in electrical potential(depolarization)
Inhibitory post synaptic potential- release of GABA. cause negative shift Cl- (hyperpolarisation)
Action potential
brief change in voltage across membrane due to flow of ion
intensity of stimulus = # of neuron generate
strong stimulus (above 55mV)caused by depolarization
electrical signal pass trigger zone and axon hillock
How is action potential similar to toilet?
-action potential or impulse is sent
-refractory period to be refilled
-resting potential, Charged when water is in tank
-All or nothing, same intensity every time
Temporal summation
-same presynaptic neuron stimulates postsynaptic neuron multiple times to cause action potential
Spatial summation
Multiple presynaptic neuron stimulating 1 postsynaptic neuron causing action potential
Axon vs axon hillock
Axon- integration of synaptic signal at axon hillock
generate action potential, and downstream synapese
-Transmit signal actively (amplifies action potential along the way)
axon hillock- decide if action potential will be produced or not
-need to go above 55 mV to initiate action potential
-sodium and potassium channel, sodium potassium pump,
Action potential is the reversal ______ and restoration ______of the membrane potential as an impulse travels along it
depolarization
repolarization
4 steps of transmission of into within neuron
1- sodium potassium pump (Na+/K+) pump maintain resting potential. some K+ leak out of neuron, membrane potential -70mV
2-Voltage gated Na+ channel open and sodium enter through through diffusion. If threshold potential achieved, all Na+ channel open cause membrane to be positive (depolarisation)
3-Na+ channel close and voltage gated K+ channel open. K+ diffuse out of neuron. Membrane become negative (repolarisation)
4- Na+ (out) and K+ (in) need to be reset by Na+/K+ pump, returning to resting potential(refractory period) impulse can only travel 1 direction
Continuous conduction vs saltatory conduction
Continuous conduction
-Action potential travel entire unmyelinated axon at 1 m/s
-wait for ion and gate to move before voltage gated Na+ and K+ channel regenerates
Saltatory conduction
Action potential only propagated at nodes of Ranvier of myelinated axon at 100m/s
-Ap generated only in myelin sheath gap and jumps
Saltatory conduction
Axonial ion channels are import for initiation and propagation of action potential to release neuro transmitters
-when action potential is present at 1 node, Na+ ion cause displacement of K+ ion down axon (makes next node more positive and depolarizes)
Conduction in unmyelinated neurons
Conduction slows due to degenerated myelin sheath
Multiple sclerosis
disease of brain and spinal cord
Immune system attack myelin sheath
cause communication problem between brain and body
-nerve damage
-vision loss, pain fatigue
Action potential have the same _____
amplitude (all or nothing)
weak -70 mV RMP with same action potential
Strong stimulus has
high frequency of action potential generated
Sensory, integrative, and motor function
Sensory function- sense change in internal/external environment through sensory (afferent neurons). Info from receptors
Integrative- analyze sensory info, store, make decisions on behavior (association or interneurons)
Motor functions- respond to stimuli by initating action. Motor (efferent) neuron. Send into to effectors (muslces and gland)