Nervous System Flashcards
Functions of the Nervous System
- Coordinate the actions of your body
- Ensure effective behaviour
- Maintain homeostasis in the internal environment
Homeostasis
Stability in the body
What send electrochemical messages throughout the body
The brain and hormones
What are the two parts of the nervous system
The Central Nervous System (CNS)
The Peripheral Nervous System (PNS)
What makes up the CNS
The brain and spinal cord
What makes up the PNS
The rest of the body
What are the two types of cells in the nervous system
Neurons and Neuroglial Cells
Neurons
Transmit impulses
Neuroglial Cells
Support neurons
Dendrites
Receive signals
Cell body
Contains the nucleus
Axon
Conducts nerve impulses away
Sensory neurons
Take information from sensory receptors to the CNS
Interneurons
Occur within the CNS and integrate input (nonmyelinated)
Motor Neurons
Informations from CNS to muscles or glands
Nodes of Ranvier
Unmyelinated sections of a myelinated neuron, impulses “jump” from node to node
Neurilemma
A thin layer encompassing neurons in the PNS, promoting regeneration
Schwann Cells
Responsible for the myelin synthesis, type of glial cells (supporting and nourishing cell found in the nervous system)
Axon Bulb
Either at a synaptic bulb or end plate to muscle, contains neurotransmitter
Myelination
Covers long axons with a myelin sheath
What does a sheath contains
Lipid myelin
What does lipid do to the appearance of the myelin sheath
It gives nerve fibers their white appearance
Mulitple Sclerosis
Disease of the myelin sheath
What are nerves made up of
Many neurons
What is white matter
Mylenated neurons
Whats the difference between white and gray matter
White matter can regenerate, gray matter won’t regenerate
Reflex Arc
Pathways that use fewer neurons and it allows you to react rapidly when there is danger
What is the order of a reflex arc
- Sensory Receptor
- Sensory Neurons
- Interneurons
- Motor Neurons
- Effector
Nerve Impulses
Convey Information
Oscilloscope
Nature of a nerve impulse has been studied by using excised axons and voltmeter
Thershold Potential
Neurons either fully activate and give a certain level of response, or it doesn’t activate at all
How is the brain informed of the intensity by
- Frequency of firing is increased
- The number of neurons that respond to that level of stimulus can increase
Resting Potential
When no nerve impulse is being conducted
What is the charge inside the axon when it is at resting potential
-70 mV
What is being pumped in the cell and out of the cell during resting potential
Potassium is being pumped into the cell. Sodium is being pumped out of the cell
Membrane depolarization
Also known as the action potential. When the nerve cell is excited and the polarity changes
What happens to the potassium and sodium ions in the cell during depolarization
The sodium channels open and the sodium rushes in while the potassium gates close. There then becomes a greater concentration of sodium ions in the axon.
What does the charge of the axon become during membrane depolarization
40mV
Membrane Repolarization
The charge changes again, the axon membrane goes back to polarized but the sodium is inside the axon membrane and potassium is on the outside
What does the Na/K Pump restore
The ion concentrations inside and outside the cell
Refractory Period
Lasts 1-10 ms, it gives time for the neuron to recover. The pump requires ATP in order to work
What is the purpose of the refractory period
To make sure that the impulse travels forward
Synapse
The junction between neurons or neurons and effectors
When does a transmission of a nerve impulse take place
When a neurotransmitter molecule stored in the synaptic vesicles in the axon bulb is released to the synaptic cleft between the axon and the receiving neuron
What happens when a nerve impulse reaches an axon bulb
Calcium channels open and Calcium flows into the bulb
What does the rise in calcium cause
Synaptic vesicles to move and merge with the presynaptic membrane
What do the synaptic vesicles merging with the presynaptic membrane cause
Releasing of the neurotransmitter molecules into the synapse
What does the binding of the neurotransmitter to the receptors in the postsynaptic membrane cause
Inhibition and Excitation
Inhibition
Has a hyperpolarizing effect on the postsynaptic membrane
Excitatory
Has a depolarizing effect on the postsynaptic membrane
Summation
Summing up of excitatory and inhibitory signals
Two well known neurotransmitters
Acetylcholine and Norepinephrine
What enzyme breaks down acetylcholine
Acetylcholinesterase
How are neurotransmitter molecules removed from the cleft
Enzymatic breakdown or reabsorption
Why is synaptic transmission much slower than axonal transmission
Neurotransmitter move only by diffusion
