the nervous system Flashcards
what are the two major divisions of the nervous system?
Central Nervous System (CNS) and Peripheral Nervous system (PNS)
what are nerve cells called?
neurons
what does the central nervous system include?
the brain and spinal cord
what does the peripheral nervous system contain?
everything else (that’s not brain and spinal cord)
what are the parts of a neuron?
dendrites, cell body, axon, myelin sheath, schwann cell, nodes of ranvier, synaptic endings
what is a dendrite’s function?
dendrites have lost of surface area to pick up nerve impulses and conduct the impulse towards the cell body
what is the cell body?
the metabolic center of the cell
what does the cell body do?
metabolic reactions occur there (ie: cellular respiration, protein synthesis, lipid synthesis)
what is the function of an axon?
conducts nerve impulses away from the cell body
what is the myelin sheath and what is the function of it?
it is made of lipids and wraps around the axon and cell body to insulate it.
what is a schwann cell?
produces the myelin sheath and has tightly packed spirals of cell membranes that form layers of the myelin
what are the nodes of ranvier?
gaps in the myelin where the axon is not insulated and allows more rapid nerve conduction along the axon
what are synaptic endings?
the end of the axon where vesicles containing neurotransmitters are located
what are neurons?
specialized nerve cells that carry nerve impulses
what are the three types of neurons?
- sensory
- motor
- interneuron
what is another name for a sensory neuron?
afferent neuron
what is another name for a motor neuron?
efferent neuron
what is another name for an interneuron?
association neuron or connector neuron
what does a sensory neuron do?
takes messages from sense organs to CNS
what does a motor neuron do?
takes messages from the CNS to a muscle fibre or gland
what does an interneuron do?
conveys “messages” between parts of the nervous system
what are the characteristics of a sensory neuron?
long dendrites and short axon
what are the characteristics of a motor neuron?
short dendrites and long axon
what are the characteristics of an interneuron
interneurons are completely contained within CNS. dendrites and axons can be long or short
what is nerve conduction?
an electrical impulse that moves in one direction along the length of a nerve fiber
what changes occur with nerve conduction?
voltage and concentrations of certain ions
what can be used to measure potential differences in voltages?
an oscilloscope
what are the three phases of nerve impulse conduction
- resting potential
- action potential
- refractory period
what is resting potential?
the potential difference across the membrane of the axon when it is NOT conducting an impulse
what is resting potential equal to?
-70mv
why is resting potential negative?
the presence of large organic negative ions (proteins) in the axoplasm
what is the axoplasm
cytoplasm inside the axon
during resting potential where are sodium ions more concentrated?
the outside of the membrane
during resting potential where are potassium ions more concentrated?
the inside of the axon
how is the uneven distribution of Na+ and K+ ions maintained?
active transport across sodium/potassium pumps
what is action potential?
when a nerve is stimulated by electric shock, ph change, or mechanical stimulation (touch, temp) and a nerve impulse is generated (the impulse is called action potential)
during the upswing in action potential the -70mv becomes what number?
+40mv
what is the upswing?
the membrane becomes permeable to Na+ ions and sodium moves from outside to inside.
what is it called when when sodium ions move inside and make the axon positive?
depolarization
during the upswing why does the membrane become permeable to sodium ions
sodium channels open
what is the downswing in action potential?
the membrane become permeable to K+ ions and potassium moves from inside to outside of axon
what is it called when potassium moves from inside to outside and makes the axon negative again?
repolarization
why does the membrane become permeable to K+ during the downswing?
potassium channels open
what is the refractory period?
in between nerve impulses/transmissions when K+ and Na+ ions are returned to their original postition
what does the refractory period require?
ATP and a carrier protein
what gives nerves their white and shiny appearance?
myelin
what is the speed of transmission in myelinated fibers?
200m/s
what is the speed of transmission in non-myelinated fibers?
0.5m/s
why is transmission faster with a myelinated fiber?
nerve impulses “jump” from node to node in myelinated fibers and must de and repolarize each point along the fiber in non-myelinated fibers
what are advantages of myelinated fibers over non myelinated?
- think faster
- respond faster
- move faster
what is at the end of an axon?
synaptic endings
what do synaptic endings do?
release neurotransmitters to affect the potential of the next neurons
what is a synapse?
the region between the end of an axon and the cell body or dendrite it is attached to
what are synaptic endings?
swollen terminal knobs on the ends of axon terminal branches
what is a presynaptic membrane?
the membrane of the synaptic ending
what is a postsynaptic membrane?
the membrane of the next neuron just beyond the axons synaptic membrane
what is a synaptic cleft?
the space between the pre and post membranes
what are neurotransmitter substances?
chemicals that transmit the nerve impulses across a synaptic cleft
what are excitatory transmitters?
they make post-synaptic membranes more permeable to Na+
what are some examples of excitatory transmitters?
epinephrine, dopamine, glutamate
what are inhibitory transmitters?
make post-synaptic membranes less permeable to Na+
what are examples of inhibitory transmitters?
GABA, serotonin, glycine
what do synaptic vesicles do?
contain the neurotransmitters near the surface of synaptic endings
what are neurotransmitters?
small molecules. they can be single amino acids, short chains of aa, or derivatives of protein.
what do neurotransmitters do?
take nerve impulses across synapses
what does an excitatory message do?
it tells a neuron to fire
what does an inhibitory message do?
tells a neuron not to fire
what does the PNS focus on?
voluntary and involuntary control
The Peripheral Nervous System consists of nerves that contain only _____ dendrites and/or axons
long
neuron cell bodies are only found where?
brain, spinal cord, ganglia
what are ganglia?
collections of cell bodies in the PNS
what are the three types of nerves?
- sensory nerves
- motor nerves
- mixed nerves
what do sensory nerves contain?
long dendrites of sensory neurons
what do motor nerves contain?
only the long axons of motor neurons
what do mixed nerves contain?
contain both the long dendrites of sensory neurons and the long axons of motor neurons
how many pairs of cranial nerves do humans have attached to the brain?
12
how many pairs of spinal nerves do humans have?
31
where do the roots of mixed nerves lie within?
the vertebral column
the dorsal root can be identified by what?
the presence of an enlargement called the dorsal root ganglion
what does the dorsal root ganglion contain?
cell bodies of sensory neurons
what does the ventral root contain?
axons of motor neurons
where to the two roots (dorsal and ventral) meet?
just before the spinal nerve leaves the vertebral column
what are two branches of the peripheral nervous system?
autonomic and somatic
what are reflexes?
automatic, involuntary responses to changes occurring inside or outside the body
what is the main functional unit of the nervous system?
the reflex arc
what are the steps to a reflex action?
- receptor stimulated
- sensory neuron carries impulse (via dorsal root ganglion)
- sensory neuron synapses with interneuron
- interneuron synapses with motor neuron
- motor neuron carries impulse
what are two branches of the autonomic nervous system?
sympathetic and parasympathetic
which of the PNS branches is voluntary movement
somatic
which of the PNS branches is involuntary movement?
autonomic
what is the main thing the sympathetic nervous system controls?
fight or flight response
the parasympathetic nervous system gives off a ____ state?
relaxed
the sympathetic and parasympathetic nervous systems connect to _____ organs and have the _____ effects?
the same, opposite
how many motor neurons does the sympathetic and parasympathetic system use for each impulse?
2
how many ganglions does the sympathetic and parasympathetic system use for each impulse?
1
what neurotransmitter is connected to the sympathetic NS?
noradrenalin/norepinephrine
what neurotransmitter is connected to the parasympathetic NS?
aretylcholine
what are the 3 protective membranes of the CNS called?
meninges
what are the three meninges called?
dura mater, arachnoid, pia mater
what are the spaces between meninges filled with for cushioning and protection?
spinal fluid (cerebro)
what “nickname” does the spinal cord have?
superhighway of the nervous system
what is grey matter?
cell bodies, where synapses occur and interneurons are located
what is white matter?
myelinated nerve tracts
how much does the brain weigh?
3 pounds (approx)
what are the 4 lobes of the cerebral hemispheres?
frontal, parietal, temporal, occipital
what are the sections of the hindbrain?
medulla oblongata
cerebellum
what are the sections of the forebrain?
thalamus
hypothalamus
corpus callosum
what is the medulla oblongata?
the “brain stem”
controls heart rate, breathing, blood pressure, and reflex reactions
what is the cerebellum?
controls balance and complex muscle movement. it is responsible for maintaining normal muscle tone and pressure
what is the midbrain?
central relay station between the fore and hindbrain and medulla oblongata
what is the thalamus?
receives sensory info from all parts of the body and channels them to the cerebrum
what is the hypothalamus?
regulates homeostasis and controls pituitary gland
what is the corpus callosum?
horizontal connecting piece between the two hemispheres of the brain. it transmits impulses between them
which side of the brain is more creative/ visual?
right
which side of the brain contains speech?
left
what is the conscious brain?
the cerebrum
what is the cerebrum?
the largest and most highly developed portion of the brain. intellect, learning, memory, and sensations are formed here.
what does the frontal lobe control?
thinking, problem solving, movement, moving mouth/tongue to speak
what does the parietal lobe control?
primary senses (touch, temp, pain) and understanding speech
what does the temporal lobe control?
hearing, smelling, memory of visual scenes, music, complex sensory patterns
what does the occipital lobe control?
vision, combining visual experiences with other sensory experiences
