Nervous System Flashcards
nervous system cells + parts
NEURONS – three (and a half) parts (:) dendrite, cell body, axon, axon terminals
gap is called…
synapse
What “closes” the gap?
neurotransmitters
resting potential
Sodium-potassium pumps in neuron membranes use ATP (Na+/K+ ATPase) to actively pump sodium OUT and potassium IN
Potassium leak channels allow some potassium to flow out of the cell, BUT…
Resting potential is at -70 mV (millivolts)
depolarize definition
make less negitive
action potential
NOTE: Membrane has potassium leak channels, Na+/K+ ATPase, and sodium and potassium voltage-gated channels.
(1) Chemical signals depolarize the dendrites, changing values from -70 mV to -50 mV.
(2) -50 mV is the threshold potential for the sodium voltage-gated channels. So they open!
(3) Sodium ions rush in, further depolarizing to +35 mV.
(4) Sodium voltage-gated channels close and potassium voltage-gated channels open.
(5) Potassium ions rush out, repolarizing to -90 mV.
(6) Potassium voltage-gated channels close.
(7) Resting potential (-70 mV) is restored.
This is a CHAIN REACTION traveling down the neuron. The closing of sodium voltage-gated channels prevent the reaction from going backward.
What makes action potential more efficient?
MYELIN SHEATH: helps to speed up movement of action potentials along the axon; made of Schwann cells; gaps in between Schwann cells are called the nodes of Ranvier.
**The action potential JUMPS from node to node (SALTATORY CONDUCTION) = efficient. **
How to increase intensity of signals?
Fire action potentials faster or slower!
Action Potentials: Crossing the Gap (THE LEAP OF FAITH!!!!!!)
When action potentials reach the synapse, they cause release of vesicles, which have neurotransmitters in them.
TWO types of neurotransmitters
excitatory: cause action potential to continue by causing + ions to enter next neuron
inhibitory: cause - ions to enter next neuron, preventing action potential
What’s that actual gap?
synaptic cleft
cnidaria nervous system
simple collections of nerves
annelids & mollusks nervous system
clusters of neurons called ganglia (sometimes form primitive brain)
arthropods nervous system
ganglia + sensory organs
vertebrates nervous system (two parts)
central (CNS) and peripheral (PNS) nervous systems
three types of neurons
sensory (afferent) – info to CNS
interneurons – connect sensory & motor
motor (efferent) – info away from CNS
CNS
brain: made of interneurons
– cerebrum: largest, voluntary movement, conciousness, memory, speech
– cerebellum: balance & coordination
– brainstem: involuntary functions (specific part known as medulla oblongata)
– hypothalamus: homeostasis, emotion
spinal cord: made of all three neurons, simple reflexes
– glial cells: provide support for neurons
PNS
sensory: info from senses to CNS
motor: CNS to organs & muscles
motor nervous system (part of PNS)
somatic: voluntary movement, skeletal muscles, always excites using acetylcholine (neurotransmitter)
autonomic: involuntary movement, tissues other than skeletal muscles, can excite or inhibit
autonomic nervous system (part of motor –> part of PNS)
sympathetic: prepares for emergency situations (fight or flight!!!!!), stimulates release of epinephrine and norepinephrine into bloodstream (reinforcing effects)
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parasympathetic: rest & digest, also uses acetylcholine
eyes (structure)
from outside to inside: cornea –> pupil (size controlled by iris) –> lens –> retina
Rods & cones in retina sense differences in light, firing action potentials to optic nerve to the occipital lobe of brain.
ears (and balance!!)
eardrum (tympanic membrane) –> auditory ossicles (ear bones) –> cochlea
Cochlea hairs change vibrations to action potentials. This is sent to the auditory nerve to the brain.
Three semicircular canals detect the position of the head, sending action potentials when position (balance) changes.
taste & smell
taste: taste bud chemoreceptors create action potentials; sent through facial and glossopharyngeal nerves
smell: Molecules pass along olfactory epithelium, dissolve in its mucus, bind to receptors, activate action potentials
somatic senses
basically feelings of touch felt in skin, muscles, tendons, joints
