Chapter 11 - Nervous System Flashcards
What are the subdivisions of the nervous system?
- Central Nervous Sysytem
- Peripheral Nervous System
What are the subdivisions of the PNS?
- Sensory (afferent) division
- Motor (efferent) division
What is the Sensory (afferent) division?
- Somatic and visceral sensory nerve fibers
- conducts impulses from receptors to the CNS
EX: sensory neurons in eyes send messages to the brain about light
What is the Motor (efferent) division?
- Motor nerve fibers
- conducts impulses from the CNS to effectors (muscles and glands)
EX: waving hand or kicking a ball
What are the subdivisions of the motor division?
- Somatic Nervous System
- Autonomic Nervous system
What is the Somatic nervous system?
- Voluntary
- Somatic motor
- conducts impulses from CNS to skeletal muscles
EX: controlling your breathing
What is the Autonomic Nervous System?
- Involuntary
- conducts impulses from the CNS to cardiac, smooth muscle, and glands
EX: heartbeat
What are the subdivisions of the Autonomic nervous system?
- Sympathetic
- Parasympathetic
What is the Sympathetic Nervous System?
- Mobilizes body systems during activity
- Emotions
- Fight or Flight
EX: increasing blood pressure
What is the Parasympathetic Nervous System?
- Converses energy
- Promotes house-keeping functions during rest
EX: decreasing blood pressure, peristalsis of stomach contents
What are the fundamental types of neurons in the PNS?
- Sensory (afferent) neurons
- Motor (efferent) neurons
What are the fundamental types of neurons in the CNS?
- Interneurons (association neurons)
What are Neurons?
- Electrical and chemical signals to send information between different areas of the brain, as well as between the brain, the spinal cord, and the entire body.
What are Sensory neurons?
- Conduct signals from receptors to the CNS
- Sense the problem/transmit signal
EX: Touching a hot stove
What are Interneurons?
- Confined to the CNS
- pass message along in the brain
EX: The stove is very hot
What are Motor Neurons?
- Conduct signals from the CNS to effectors (muscle/glands)
- Receives a message from CNS
EX: remove your hand from the hot stove
What are the types of nerve cells?
- Neuroglia (glial cells)
- Neurons (Neural Cells)
What are Neuroglia Cells (glial cells)?
- Nerve “glue”
- Provide nutrients
What are the types of Neuroglial cells in the PNS?
- Satellite Cells
- Schwann Cells
What are Satellite Cells?
- Repair anything in the NS
- Allows muscle tissue to regenerate
What are Schwann cells?
- Wrap around the axon to provide insulation
- Keeps axons alive
- Sometimes covering them with a myelin sheath
- Major glial cell type in the peripheral nervous system
What are the Neuroglial Cells of the CNS?
- Microglia
- Ependymal Cells
- Oligodendrocytes
- Astrocytes
What are Microglia cells?
- Function in immune function
- Remove dead neurons and synapses
- Maintain the health of CNS
- regulate brain development, maintenance of neuronal networks, and injury repair
What are Ependymal Cells?
- Form a barrier for Cerebro Spinal Fluid
- Line the ventricles in the brain and the central canal of the spinal cord
What are Oligodendrocytes?
- Wraps around the axon to provide insulation
- allows fast and efficient transfer of neuronal communication through the myelination of axons
What are Astrocytes?
- 20-40% of all glial cells
- Provides nutrients
- Forms structures
What are the parts of a Neuron?
- Cell Body (soma)
- Dendrites
- Axon
- Axon Hillock
- Schwann cells
- Myelin Sheath
- Terminal Branches
- Axon Terminal
What does the cell body of a Neuron do?
- Receives signals
- Contains organelles and Nucleus
- Provides energy
What are Dendrites?
- Tree-like branches that come out of the soma
- Increases the surface area available for receiving incoming information
- Receiving or input portions of a neuron
What is the Axon?
- Conducts the electrical signal (carries the impulse away from the soma)
- Can be mm to meters long (brain-toe)
- Generates Action Potential
What is the Axon Hillock?
- Region in the cell body where the summation of the excitatory & inhibitory activity occurs
- Starts signal
What are Axon Terminals?
- Small swellings that are found at the terminal ends of axons
- Release neurotransmitter when stimulated by an electrical signal carried by the axon
- if the signal is strong enough it will be transmitted through the Axon terminals, if not it will be terminated
What are the Properties of Neurons?
- Excitable
- Conductivity
- Secretion
What is Excitability in a neuron?
- Ability to respond and recognize a stimulus
What is Conductivity in a neuron?
- Electrical signal transmitted
- Local electrical change triggers a wave of excitation that travels along the muscle fiber
- Action Potential/propagation
What is Secretion in a neuron?
- Release of signal neurotransmitter to interact with the next cell
What are the types of activation Channels?
- Ligan-gated
- Mechanical-gated
- Voltage-gated
What are ligan-gated channels?
- membrane protein channels that only open when a chemical(neurotransmitter) released form the presynaptic neuron bind to them
What are Mechanical-gated channels?
- Channels that open when it senses the change of pressure
- Poking your arm
What are voltage-gated channels?
- Change in voltage of ions in the surrounding areas
- Na+, Ca2+ and K+
What is the baseline resting membrane potential?
- (-70mV)
- Negative inside the axon, Positive outside axon
What is a threshold?
- Magnitude or intensity that must be exceeded for a certain reaction result, or condition to occur
- Needs to reach -55mV for stimuli to occu
What is depolarization?
- Change in membrane potential; moves towards 0/becomes less negative
What happens during depolarization?
- Na+ outside of the cell enters the axon filled with K+ through fast voltage-gated channels causing the resting membrane potential to increase to -55mV causing depolarization
- (-55mV)
What is repolarization?
- the cell experiences a decrease of voltage due to the loss of potassium (K+) ions along its electrochemical gradient
- Na+ fast-voltage channels become inactivated
What happens during repolarization
- Na+ fast-voltage channels become inactivated
- A decrease of voltage due to the loss of potassium (K+) ions through slow voltage-gated K+ Channels along its electrochemical gradient
- (+30mV)
What is hyperpolarization?
- a phase where some potassium channels remain open and sodium channels reset.
What happens during hyperpolarization?
- K+ slow voltage-gated channels are slow to shut so too much K+ leaks out
- Na+ fast voltage-gated channels reopen letting more Na+ in
- (-100mV)
How does the action potential return back to the resting membrane potential after hyperpolarization?
- Using a Na+/K+ atpase pump
- The pump brings K+ in and kicks Na+ out of the axon returning to -70mV
- Requires energy!!!
What is the Absolute refractory period in an axon?
- The axon cannot respond or stimulate another action potential
- Stimulus to peak and part of repolarization
What is the Relative refractory period?
- Axon can respond to a 2nd stimulus but it has to be stronger than the first stimulus
What does myelination help with during a stimulus?
- Allows electrical impulses to transmit quickly and efficiently along the nerve cells
- Creates a sheath around the axon; made up of proteins and fat
- Keeps stimulus from decaying
What does the node of Ranvier do?
- contain sodium and potassium ion channels, allowing the action potential to travel quickly down the axon by jumping from one node to the next.
What cell provides myelination in the CNS?
- Oligodendrocytes
- Branch off and interact with multiple neurons
- 80% fat (lipids) 20% proteins
What cell provides myelination in the PNS?
- Schwann Cells
- Wraps around 1 neuron not multiple!
- Mostly fat
What are synapses?
- The functional connection between a neuron and another cell
What are the types of synapses?
- Electrical (Gap junction)
- Chemical (neurotransmitters)
What are the synaptic relationships between neurons?
- Axodendritic
- Axosomatic
- Axoaxonic
What are Axodendritic synapses?
- Axon terminal of the pre-synaptic neuron interacts with the dendrites of the post-synaptic neuron
What are Axosomatic synapses?
- The axon terminal of the pre-synaptic neuron interacts with the soma (cell body) of the post-synaptic neuron
What are Axoaxonic synapses?
- The axon terminal of the pre-synaptic neuron interacts with the Axon or Axon terminal of the post-synaptic neuron
What happens when an action potential makes its way down the synapes?
- Action Potential interacts with voltage gated calcium channels
- The Ca2+ gates open, bringing in Ca2+ into Axon terminal
- When Ca2+ enters, interacts with cytoskeleton proteins that causes a shift
- When proteins shift, we get neurotransmitted synaptic vesicles to move to and merge with the Plasma membrane
- The vesicles then are excised releasing neurotransmitters into the synaptic cleft binding to channels causing a graded potential
What happens to the neurotransmitters after they bind to channels on the postsynaptic neuron?
- They are reuptaken, broken down by enzymes in cleft, or they break away
