Nervous System Flashcards
What does the central nervous system (CNS) feed to?
The spinal cord and the brain
What does the peripheral nervous system (PNS) feed to?
Sensory pathways and motor pathways
What do motor pathways feed to? Describe each one.
Somatic nervous system (you can control it) and the autonomic nervous system (your body does it)
What doe the autonomic nervous system feed to? Describe each one
Sympathetic nervous system (speeds up reactions - epinephrine) and the parasympathetic nervous system (slows down the body’s response - decreases breathing rate
Describe the function of dendrites
It receives nerve impulses from other neutrons or sensory receptors and relays the impulse to the cell body
Describe the function of the cell body
It has the nucleus and is the site of the cells metabolic reactions
It processes the input from the dendrites
Describe the function of the nucleus
Its the control centre for the neuron cell
Describe the function of the axon
Conducts impulses away from the cell body
Describe the function of the axon terminals
They branch out from the axon and release chemical signals to communicate with effectors (neuron, glands, muscles)
Describe the function of the myelin sheath
It increases speed or nerve impulse transmission. It has a fatting insulating layer to protect against charge loss. It also has a glistening white appearance
Describe the function of the schwann cells
Type of glial which is a supporting cell. It forms myelin by wrapping around the axon
Describe the function of the Nodes of Ranvier
They are gaps between the sections of the myelin sheath that function to speed up nerve impulse transmission. It allows the nerve impulse to “jump” from node to node - this is called: Salvatory Conduction
Describe the function of the Neurilemma
It is the delicate membranes supporting the axon of some neurons. It promotes nerve regeneration (the neuron repairs itself)
Myelinated Neurons: speed, covering, neurilemma, colour and system its found in
Increased speed, covering present, neurilemma present, white and PNS
Unmyelinated Neurons: speed, covering, neurilemma, colour and system its found in
Decreased speed, covering absent, neurilemma absent, grey and CNS
What is Demyelinating Disease?
Multiple Sclerosis (MS): something in the body attacks the myelin and it becomes difficult to control movement
Describe the function of the sensory receptors
Receive stimuli and form a nerve impulse
Describe the function of the sensory neurons
Transmit impulses from the sensory receptors to the interneurons
Describe the function of the interneurons
Are found in the brain and spinal cord and they act as an integration centre
Describe the function of motor neurons
Transmit information from the central nervous system to the muscles, gland and other organs
Describe the function of the effectors
Muscles, glands and other organs that respond to impulses from the motor neurons
Construct a reflex pathway for a pin prick to the finger
Stimulus (pin prick) -> sensory receptor -> sensory neuron -> interneuron -> spinal cord -> motor neuron -> effector (muscle) -> response (move finger away)
What is the first step of Action Potential?
Resting membrane potential:
More potassium leaks out than salt is diffusing in
Na/K pump maintains the negative value of about -70mV
What is the second step of Action Potential?
Threshold:
Stimulation causes NA channels to open and NA moves in the cells (it flows down it’s concentration gradient)
Cell becomes more positive inside (depolarization) and it reaches the threshold to stimulate an action potential
What is the third step of Action Potential?
Depolarization:
More NA channels open and NA rushes into the cell
Inside the neuron cell becomes more positive
Na channels shut
What is the fourth step of Action Potential?
Repolarization:
K channels open and K moves out of the cell
The membrane potential returns to resting level and is repolarized
The outside of the axon is positive and the inside is negative
What is the fifth step of Action Potential?
Hyperpolarization:
The cell membrane becomes more negative than the resting potential
This overshoot is caused by the K channels are still open
NA/K pump must now re-establsih ion concentration gradients
What is threshold potential?
A minimum voltage requirement of usually 15m V is required to cause an action potential. Once it gets it started it can have a bigger voltage but will not increase or decrease the action potential
What is an all or none response?
An action potential occurs maximally or they do not occur at all.
Once the threshold is reached you get an action potential