Nervous System Flashcards
What two systems are the Nervous System divided into?
PNS - Peripheral Nervous System
CNS - Central Nervous System
What is the role of the PNS?
Gather central information and then relay this information to intraneurons (CNS) and then send signal to muscles and glands for a voluntary (somatic) or involuntary (autonomic) response.
What is another word for voluntary?
Somatic
What is another word for involuntary?
Autonomic
What are some key characteristics of the somatic system?
Myelinated or unmyelinated?
-Largely under voluntary control
-Sensory neurons carry info about the external environment inward from receptors in the skin, tendons, and skeletal muscles
-Motor neurons carry information to skeletal muscles
-Are all myelinated
How are spinal nerves named?
Based on the region of the body where they are located; Cervical, Lumbral, Sacral
What are some roles of the autonomic system?
- Homeostasis is maintained in the body by the often antagonistic actions of the sympathetic and parasympathetic nervous systems.
- The sympathetic nervous system prepares the body for flight or fight (ex: increasing heart rate), while the parasympathetic system returns organs to a resting state (ex: lowering heart rate)
- Depending on your environment, certain structures in your body react differently. Imagine being chased by a tiger vs. relaxing on the couch
What is the role of the sympathetic nervous system?
What neurotransmitter(s) is released?
Fight or Flight
- Acts when the body is under stress
- Release the neurotransmitter norepinephrine
- Also triggers adrenal gland to release epinephrine and norepinephrine
What is norepinephrine?
Has an excitatory effect on it’s target muscles
What is epinephrine and it’s purpose?
Adrenaline - it triggers stress releases
What is the role of the parasympathetic nervous system?
What neurotransimtter(s) is relased?
Rest and Digest
- Acts to restore and conserve energy
- Uses the neurotransmitter acetylcholine to control organ responses
What is the basic functional unit of the nervous system?
Neuron
What three parts does the Neuron consist of?
- Cell body
- Dendrites
- Axons
What is the function of a nueron?
Transmit information
Parts of Neuron: Cell Body
Contains nucleus and two extensions
Parts of Neuron: Dendrities
Shorter, more numerous, receive information
Parts of Neuron: Axons
Single, long fibers which conduct impulses away from the cell body; send information
What is a Schwann Cell?
Axons usually contain a series of enclosing cells called Schwann cells.
What is the purpose of Schwann Cells?
The presence of the Schwann Cells increases the speed of transmission because it limits the loss of chemicals.
Long projections of a neuron conduct the electrical impulse; what is this electrical impulse called?
Action Potential
What are gaps between the Schwann cells called?
Nodes of Ranvier
What is the purpose of the Nodes of Ranvier
Speed up the impulse
What is the speed of an impulse proportionate to?
The diameter of the axon
If an axon has a greater diameter what happens to the speed of an impulse?
In increases
Do myelinated axons or unmyelinated axons conduct faster?
Myelinated axons conduct faster
What does Myelinated refer to?
It refers to white matter - myelinated axons conduct faster because the myelin sheath increases speed
What are collections of Schwann cells known as?
Myelin Sheath
What does Unmyelinated refer to?
Grey Matter - Lacks a Myelin Sheath
What are the three types of Neuron?
Sensory Neurons
Interneurons
Motor Neurons
What is the purpose of Sensory Neurons?
Gather information from receptors and pass onto interneurons (CNS)
What is the purpose of interneurons?
Process information and send to motor neurons.
What is the purpose of Motor Neurons?
Carry signals from CNS back to the body - organs, tissue, ect.
How do Sensory Neurons gather information?
They gather information from receptors (senses) and transmit impulses to the CNS (Brain and Spinal cord)
What do Interneurons act as?
They act as a link between sensory and motor neurons; process incoming info and relay outgoing info
What do motor neurons do?
Transmit information from CNS to muscles glands and other organs
What is the Nerve impulse pathway?
- Sensory receptors gather information
- Information gathered from sensory receptors is passed onto interneurons in the CNS
- Motor neurons then transmit information from CNS to muscles, glands, and other organs (effectors)
What is a reflex ark?
Only includes a few neurons.
What is a reflex behaviour?
Autonomic, subconscious response.
What is an action potential?
Is an electrochemical message caused by the movement of ions (Potassium and sodium) through the cell membrane.
What is resting potential?
How is it maintained?
Resting potential is the electrical charge difference across a neuron’s membrane when it is not actively transmitting a signal, typically around -70 mV. This is maintained by the sodium-potassium pump, which pumps 3 sodium ions out and 2 potassium ions in, creating a net negative charge inside the cell.
What is the relationship of charged ions and the cell during resting potential?
There are more positively charged ions (mainly sodium) outside the neuron than inside. This creates a difference in charge across the cell membrane, with the inside of the cell being more negatively charged.
What are the steps in action potentials?
- Stimulus received (must pass threshold potential)
- Depolarization: Sodium gates open, sodium flows into neuron (makes it positive inside)
- Repolarization: Potassium flows out of neuron, makes it negative again
- Hyperpolarization: repolarization step overshoots resting potential, important to make sure impulse moves in One direction
- Rest potential brought back by sodium-potassium pump (Uses ATP)
What is the first step in generating an action potential?
A stimulus is received that must pass the threshold potential.
What happens during depolarization in an action potential?
Sodium gates open, allowing sodium ions to flow into the neuron, making the inside of the neuron positive.
What is the role of sodium and potassium gates during repolarization?
Sodium gates close, and potassium gates open, allowing potassium ions to flow out of the neuron, making the inside of the neuron negative again.
What is hyperpolarization, and why is it important?
Hyperpolarization is when the repolarization step overshoots the resting potential, which is important to ensure the nerve impulse moves in one direction.
How is the resting potential restored during hyperpolarization?
The sodium-potassium pump restores the resting potential by using ATP to pump sodium (3) out and potassium (2) into the neuron.
What must a stimulus do to initiate an action potential?
The stimulus must pass the threshold potential to initiate an action potential.
What is the threshold stimulus?
The minimal stimulus required to cause the Na+ gates to open and impulse to be sent
What does the threshold stimulus lead to?
The all or none response
What is the synapse?
Junction between two communicating neurons.
What is Synaptic Transmission?
Synaptic transmission is the process by which a nerve signal is transferred from one neuron to another cell, typically another neuron or a muscle cell, across a synapse
What must be released at the gap to signal the next neuron?
Neurotransmitter
What makes up the CNS?
Brian and spinal chord
What makes up the PNS?
Sensory (afferent) division: Carries sensory information from the body to the central nervous system (CNS), including signals from sensory receptors (e.g., touch, pain, temperature) to the brain and spinal cord.
Motor (efferent) division: Carries motor commands from the CNS to the muscles and glands.
What is another word for sensory neurons?
Afferent Neurons
What does afferent mean?
Into something ex: afferent nerves go into CNS. eyes to brain
What is another word for motor neurons?
Efferent Neurons
What does efferent mean?
Out of someting - ex: Brain to muscles
What is the purpose of Sensory Neurons?
Carry information about external environment inward from recpetors in the skin, tendons, and skeltal muscle.