Biology: Ch. 4: The Nervous System Flashcards
Describe this neuron feature: axon
The axon transmits an electrical signal (the action potential) from the soma to the synaptic knob
Describe this neuron feature: axon hillock
The axon hillock integrates excitatory and inhibitory signals from the dendrites and fires an AP if the excitatory signals are strong enough to reach threshold
Describe this neuron feature: dendrite
Dendrites receive incoming signals and carry them to the soma
Describe this neuron feature: myelin sheath
The myelin sheaths act as insulation around the axon and speed conduction
Describe this neuron feature: soma
The soma is the cell body and contains the nucleus, the endoplasmic reticulum and ribosomes
Describe this neuron feature: synaptic bouton
The synaptic bouton lies at the end of the axon and releases the neurotransmitter
What is the collection of cells in the CNS called?
A collection of cell bodies in the central nervous system is called a nucleus
What is the collection of cells in the PNS called?
A collection of cell bodies in the peripheral nervous system is called a ganglion
Describe each of the following glial cells: astrocyte
Astrocytes nourish neurons and form the blood brain barrier
Describe each of the following glial cells: ependymal cell
Ependymal cells produce cerebral spinal fluid
Describe each of the following glial cells: microglia
Microglia ingest and break down waste products and pathogens
Describe each of the following glial cells: oligodendrocyte
Oligodendrocytes produce myelin in the CNS
Describe each of the following glial cells: schwann cell
Schwann cells produce myelin in the PNS
what neural structure initiates an action potential
An AP is initiated in the axon hillock
What entity maintains the resting membrane potential? What is the approximate voltage of the resting membrane potential?
The Na+/K+ ATPase maintains resting membrane potential at approximately -70mV
What is temporal summation?
temporal summation is the integration of multiple signals close to each other in time
What is spatial summation?
Spatial summation is the integration of multiple signals close to each other in space
During the action potential, which ion channel opens first?
Sodium channel opens first at threshold (-50mV)
How is the ion channel that opens first during an action potential (Na channel) regulated?
It is regulated by inactivation, which occurs around +35 mV. Inactivation can only be reversed by repolarization of the cell
What effect does the opening of the first ion channel in an action potential (Na channel) have on the polarization of the cell?
Opening of the sodium channel causes depolarization
During an action potential, which ion channel opens second?
Potassium channel opens around +35 mV
How is the second ion channel that opens in an AP (K channel) regulated?
The potassium channel is regulated by closing at low potentials (slightly below -70 mV)
What effects does the opening of the second channel in an AP have on the polarization of the cell?
The opening of the potassium channel causes repolarization and -eventually- hyperpolarization
What is an absolute refractory period?
In the absolute refractory period, the cell is unable to fire an action potential regardless of the intensity of the stimulus
What is a relative refractory period?
In the relative refractory period, the cell can fire an AP only with a stimulus that is stronger than normal
What ion is primarily responsible for the fusion of neurotransmitter-containing vesicles with the nerve terminal membrane?
Calcium is responsible for the fusion of neurotransmitter vesicles with the nerve terminal membrane
What are the three main methods by which a neurotransmitter’s action can be stopped?
A neurotransmitter’s action can be stopped by enzymatic degradation, reuptake, or diffusion
Which parts of the nervous system are in the CNS?
The CNS includes the brain and spinal cord
Which parts of the nervous system are in the PNS?
The PNS includes the cranial and spinal nerves and sensors
What do afferent neurons do?
Afferent (sensory) neurons bring signals from a sensor to the CNS
What do efferent neurons do?
Efferent (motor) neurons bring signals from the CNS to the effector
What functions are accomplished by the sympathetic nervous system?
The sympathetic nervous system provides the “fight or flight” response, with increased heart rate and bronchial dilation, redistribution of blood to locomotor muscles, dilation of pupils, and slowing of digestive and urinary functions
What functions are accomplished by the parasympathetic nervous system?
The parasympathetic nervous system promotes “rest and digest” functions, slowing heart rate and constricting bronchi, redistributing blood to the gut, promoting exocrine secretions, constricting the pupils and promoting peristalsis
What functions are accomplished by the somatic nervous system?
The somatic nervous system is responsible for voluntary actions- most notably, moving muscles
What functions are accomplished by the autonomic nervous system?
The autonomic nervous system is responsible for involuntary actions, like heart rate, bronchial dilation, dilation of the pupils, exocrine gland function and peristalsis
What is the pathway of neural impulses in a monosynaptic reflex?
In a monosynaptic reflex, a sensory (afferent, presynaptic) neuron fires directly onto a motor (efferent, postsynaptic) neuron
What is the pathway of neural impulses in a polysynaptic reflex?
In a polysynaptic reflex, a sensory neuron may fire directly onto a motor neuron, but interneurons are used as well. These interneurons fire onto other motor neurons
