neuro - (physiology and electrical activity) Flashcards
What are the three parts of a neuron?
- Dendrite
- Cell body
- Axon
Central Nervous System consists of:
- brain
- spinal cord
2 types of cells in the nervous system:
- neuroglia
- neurons
what is the function of the cell bodyÉ
- contains the nucleus
- creates macromolecules
- consolidates information from the dendrites
what is the function of the dendrites?
receptive area - transmit messages to cell body
what is the function of axons?
conduct pulses (action potentials) away from the cell body
what is the function of myelin sheaths?
- insulate the neuron
- increase conduction speed of action potentials
why do myelinated axons have faster conduction speeds
- myelination prevents the movement of Na+/K+ (thus preventing action potentials)
- less action potentials are required to conduct the message down the neuron than unmyelinated neurons
- also thicker and more cable-like
what is the function of the synapse?
the functional connection between the neuron and the second cell
what is the axon hillock?
the origin of the axon (where the cell body becomes the axon)
Which direction do afferent neurons carry information
INTO the CNS from SENSORY RECEPTORS
Which direction do efferent neurons carry information?
OUT of CNS to EFFECTOR ORGANS
What do somatic motor nerves control? Do we have control of these nerves?
- Skeletal muscles
- Yes
- cardiac muscle, smooth muscle and gland secretion is controlled by the ______________
autonomic nervous system
What are the two types of neuroglia in the PNS?
- Schwann cells
- Satellite Cells
What is the function of Schwann cells?
Form the myelin sheath around axons
What is the function of satellite cells?
Support of neuron cell bodies within ganglia of the PNS
What are the four types of neuroglia in the CNS?
- Oligodendrocytes
- Microglia
- Astrocytes
- Ependymal Cells
What is the function of microglia?
move around CNS and phagocytose foreign and degenerative material
What is the function of astrocytes? (4)
- Regulate the external environment of neurons
- needed for the formation of synapses in CNS
- formation of blood-brain barrier
- regulate neurogenesis in adult brain
What is the function of ependymal cells?
epithelial cells that line the ventricles of the brain and canal of the spinal cord
What are the two types of cells that form the myelin sheaths and which nervous system are each of them in?
oligodendrocytes (CNS)
Schwann cells (PNS)
What is the neurilemma and which nervous system is it in?
the continuous sheath of Schwann cells lining the axons in the PNS
What are the unmyelinated regions in between myelinated regions on an axon called?
nodes of ranviers
what is the function of the nodes of ranvier?
conduction of the nerve impulses down the axon
Is axon regeneration more common in the PNS or CNS?
PNS
What are the steps of axon regeneration in the PNS?
- severed axon degenerates
- Schwann cells phagocytose severed axon
- Schwann cells form the regeneration tube
- The growing axon connects to the cell body because it is attracted to the chemicals secreted by the Schwann cells
- Regeneration tube helps guide the new axon to its destination
Why is regeneration of axons less common in the CNS?
- death receptor production after injury of the spinal cord
- prevented by inhibitory proteins in the myelin sheath membranes
- (old myelin is rapidly phagocytosed by Schwann cells, preventing the production of inhibitory proteins in PNS)
what is a preganglionic neuron? (ANS)
- does not innervate an effector cell
- synapses with another neuron in an autonomic ganglion
What is a postganglionic neuron?
innervates the effector cell
what effect does acetylcholine release from somatic motor neurons have on an effector organ?
stimulation
what is the autonomic nervous system?
- division of the PNS
- controls involuntary bodily functions
What effect does fight-or-flight have on postganglionic neurons in the sympathetic nervous system?
mass activation
What are the two divisions of the autonomic nervous system?
- sympathetic nervous system
- parasympathetic nervous system
what does the sympathetic nervous system do?
- fight-or-flight
- “go”
- speed up
- causes activity
What does the parasympathetic nervous system do?
- “rest and digest”
- “stop”
- slow down
How many neurons from CNS to somatic motor effector organ?
one
How many neurons from CNS to autonomic effector organ?
2
What is dual innervation?
organs that are affected by activity from both the SNS and PSNS
Which four organs do not have dual innervation?
- adrenal medulla
- arrector pilli
- sweat glands
-most blood vessels
how does regulation occur in organs without dual innervation?
increases or decreases of sympathetic fibre firing
what are the two functions of the nervous system?
- Control of movement and some functions (motor nerves)
- Detection of external stimuli (sensory nerves)
Nervous system is made up of _______ ________ cells
discrete individual
What are the two functions of neurons?
- Conduct “electrical” signals (action potentials)
- Release “chemical” signals (neurotransmitters)
A(n) _____ impulse is converted to a(n) ______ at the synapse
electrical, chemical
Are interneurons within the PNS or CNS?
CNS
What do interneurons do?
send signals from one neuron to another
How do astrocytes work? (2 ways)
1.
- take up glutamate
- transform glutamate into glutamine
- glutamine released back into neuron that can retransform it into glutamate
2.
- surround the blood capillaries and take up glucose from the blood
- metabolize the glucose to lactate
- releases lactate as source of energy for the neurons
Can alcohol cross the blood-brain barrier?
Yes
Can immune cells and antibodies cross the blood-brain barrier?
No
What are the two divisions of the peripheral nervous system?
Afferent and Efferent
What are the two divisions of the efferent division?
Somatic and Autonomic
What are the two divisions of the autonomic division?
Sympathetic nervous system and parasympathetic nervous system
somatic neurons have cell bodies in the ______ that send axons to _______
CNS, skeletal muscles
_______ motor neurons have ganglia
autonomic
_______ motor neurons have only excitatory effects
somatic
_______ motor neurons have excitatory and inhibitory effects
Autonomic
_____ motor neurons are thick, fast-conducting and myelinated
somatic
______ motor neurons are slow-conducting and thin with some lightly myelinated fibres and other unmyelinated fibres
autonomic
What type(s) of neurotransmitter(s) is/are released across parasympathetic synapses
acetylcholine (pre-ganglionic AND post-ganglionic)
What type(s) of neurotransmitter(s) is/are released across sympathetic synapses?
- acetylcholine (preganglionic)
- norepinephrine (postganglionic)
At the start of action potentials, Na+ is _____ the cell and K+ is ______ the cell
outside, inside
The ____ of the cell is negatively charged compared to the ____
inside, outside
What is the resting membrane potential?
The potential difference (voltage) across the cell membrane
How do signals travel the long length of the axon without weakening?
they are continuously reamplified using voltage-gated ion channel
ion-gated channels are _____ at resting membrane potentials
closed
The voltage-gated ion channels open in response to _______
depolarization
What are the steps of action potentials and repolarization?
- Na+ channels open in response to a depolarization stimulus
- Na+ increase results in reversal of membrane potential from -70mV to +30mV (depolarizing axon)
- Na+ channels close
- K+ flows out of the cell to reduce the positive charge inside the cell repolarizing the cell
What is the absolute refractory period?
- “ball and chain”
- voltage gates will not respond to depolarization
What is the relative refractory period?
While the Na+ channels are recovering and the K+ channels are open, the cell can be stimulated if the stimulus is strong enough to create a depolarization that will overcome the outward movement of K+
Presynaptic cell releases ______ that stimulate APs in the postsynaptic cell
neurotransmitters
_____ stimulates the fusion and exocytosis of neurotransmitter
Ca2+
