Nervous System Flashcards
Central Nervous System
Brain and Spinal Cord
Processes and stores infromation
Peripheral Nervous System
- All nerves outside the CNS
- Sensory, Motor
- Somatic System, Autonomic System
- Sympathetic, Parasympathetic
Sensory Nerves
Conveys info from sensory receptors or nerve endings
Motor Nerves
Stimulates voluntary and involuntary muscles
Somatic /Autonomic Systems
Somatic System
- Controls the voluntary muscles
- MOtor neurons relase acetylcholine onto ACh receptors located on skeletal muscle
- Reflex action
Autonomic System
Controls involuntary muscles(glands and smooth muscles)
Sympathetic/Parasympathetic
Sympathetic
- Norepinephrine as primary neurotransmitter
- activates body for emergency situations
- Fight or flight response
- Increases heart and breathing rate
- Liver converts glycogen to glucose
- Bronchi of lungs dilate and icnrease gas exchange
- Adrenaline raises blood glucose levels
Parasympathetic
- Acetylcholine as primary neurotransmitter
- rest-and-digest response
- deactivate or slow down
- vagus nerve is principle nerve
- Opposes the sympathetic system
- Calms the body
- Decreases heart/breathing rate
- Enhances digestion’
Neuron
- Nerve Cell
- designed to transmit info in the form of electrochemical signals(action potentials)
- COmposed of Dendrites, axons, cell body, myelin Sheaths
Dendrites
- Receive incoming messages from other cells as changes in membrane potential
- carry the electrical signal to the cell body
Axon
- Only one for each neuron
- Transmits an impulse from the cell body to another cell
- wrapped in a myelin sheet that protects the axon and speeds the impulse
Reflex Arc
- Simplest nerve response
- Inborn, automatic, protective
- ex/knee-jerk reflex
- Spinal cord is not involved
- Sensory, interneuron, motor neuron, muscle
Membrane Potential
- A difference in electrical charge between the cytoplasm(negative charge) and extracellular fluid (positive)
- difference between -50mV to -100mV
Polarized
- A polarized neuron is at rest or unstimulated (resting potential)
- membrane potential of -70mV
- Sodium-potassium pump acitively pumps ions out of the cell
- The larger the membrane potential, the stronger the stimulus must be to cause the nerve to fire
- Pos outside(sodium) ; neg inside(potassium)
Action potential
- An impulse that can only be generated in the axon stimulated enough to overcome the threshold
- Sodium channels open and sodium flood into the cell
- Potassium channels open and potassium floods out of the cell
- Polarity of the membrane is reversed (pos inside; neg outside)
- Every action potential is the same size, but more frequency indiactes a larger stimulus
Wave of depolarization
- Rapid movement ions when an impulse passes through an axon
- Sodium in; potassium out
- reverses the polarity of the membrane
- Membrane is less polarized, moving toward 0 potential
Repolarization
Sodium-potassium pump restores the membrane to its orginal polarized condition
Refractory Period
- Period of repolarization
- Neuron can’t respond to another stimulus
- ensures an impulse moves along an axon in 1 direction since the impulse can only move to a region where the membrane is polarized
Myelin Sheet
Protects axon and speeds impulse
What gives neurons an excitable membrane?
A voltage-gated sodium channel
Threshold Potential
- The voltage at which the voltage-gated channels open
THe larger the neuron….
The faster action potentials travel
Nodes of Ranvier
Spaces between the myelin sheets that action potentials jumps from to another, bypassing myelin regions
Saltatory conduction
Action potentials jumping from Nodes of Ranvier to other nodes
Synapse/ Synaptic cleft
- Gap between neuron and target cell where neurotranmitters cross
Neurotranmitter
- chemical signal
- Released by neuron when an action potential travels down an axon to reach the synaptic terminal
- diffuses across the gap between cells and bind to receptors on the target cell membrane
Summation
- the means that a single neuron uses to process info from all neurons that form synapses with it and decide whether or not to initiate an action potential itself.
- determined by adding up the contributions to the membrane potential created by many synapses
Neuromuscular junction
- A specialized synapse of motor neurons with skeletal muscle cells
- When reached by action potential, acetylcholien is released into the synaptic cleft and binds to postsynaptic receptors in the muscle cell
- receptors open sodium channels, depolrize msucle cell membrane, trigger muscle contraction
Ways to turn off a synaptic neurotransmitter
- Diffusion
- Enzymes that degrade and inactive it (pesticides, nerve gas)
- Take it up into cells at the synapse
Vesicles
The cytoplams at the terminal branch contains many vesicles, each containing neurotransmitters
What does deploarization of the presynaptic membrane cause?
- Ca++ ions rush into terminal branch
- stimulates the vesicles to fuse with the presynaptic membrane and release the neurotransmitter by exocytosis into the synapse
- sets up another action potential on teh adjacent cell
Eye
Ear
Brain
