The Nervous System Flashcards
what structures are a part of the central nervous system
- brain
- spinal cord
what is the function of the central nervous system
- take in sensory (afferent) information
- make decisions about the information
- send motor (efferent) signals to control muscles/glands of the body
how many pairs of spinal nerves are there
31
how many pairs of cranial nerves are there
12
what are the two motor divisions of the nervous system
- autonomic nervous system
- somatic nervous system
describe the somatic nervous system
- sends commands to skeletal muscles
- conscious and voluntary control
what are the two divisions of the autonomic nervous sytem
- sympathetic division
- parasympathetic division
what are the effectors of the autonomic nervous system
- cardiac muscle
- smooth muscle
- glands
what are the effectors of the somatic nervous system
skeletal muscle
describe the sympathetic nervous system
- division of the autonomic nervous system
- responsible for fight or flight reactions
describe fight or flight responses
- increased heart rate
- pupil dilation
- sweating
- blood flowing to internal organs (feeling a chill)
- adrenal glands activated
describe the parasympathetic nervous system
- division of the autonomic nervous system
- responsible for regulating resting and digesting functions
are you always in either the sympathetic nervous system or parasympathetic nervous system
no, usually both systems are being activated at varying levels depending on the circumstances
when are you entirely relying on the parasympathetic nervous system and not the sympathetic nervous system
sleeping
is it better to be more on the sympathetic or parasympathetic side of the autonomic nervous system
better to be more in the parasympathetic division
what are the 3 neuron types
- multipolar neuron
- bipolar neuron
- pseudo-unipolar neuron
which neuron type is the most common
multipolar neuron
describe multipolar neurons
- have many dendrites (up to thousands)
- have only one axon
define the trigger zone on a neuron
where an action potential will begin
where is the trigger zone located on a multipolar neuron
where the cell body meets the axon
describe bipolar neurons
- have only one dendrite
- have only one axon
where is the trigger zone located on a bipolar neuron
where the cell body meets the axon
where are bipolar neurons found
- retina
- cranial nerve I (olfactory)
describe pseudo-unipolar neurons
- appear to have no dendrites and one axon
- cell body only connects to the axon
- sensory receptors on a portion of the axon
where is the trigger zone located on a pseudo-unipolar axon
at the end of the sensory recepting portion of the axon
what is the general function of all glial cells
support the functioning of neurons
how many neurons are in the brain
100 billion
how many glial cells are there compared to neurons
50-100x more glial cells than neurons
what are the glial cell types in the CNS
- astrocytes
- ependymal cells
- microglia
- oligodendrocytes
what are the glial cell types in the PNS
- Shwann cells
- satellite cells
what are the most abundant glial cell type
astrocytes
what are the functions of astrocytes
- surround neurons to anchor them in place
- wrap around capillaries with perivascular feet to regulate what can leave the capillary and enter the interstitial fluid (blood-brain barrier)
where are ependymal cells found
- CNS
- lining ventricles of the brian
what is the function of ependymal cells
circulate cerebrospinal fluid in brain ventricles
what type of cell in the skin are microglial cells analogous to
dendritic cells (immune cells)
what are the functions of microglial cells
- attack pathogens found
- remove damaged/dead cells through phagocytosis
what is the function of oligodendrocytes
wrap around axons (myelination) to speed the travel of action potentials in the CNS
how many axons does each oligodendrocyte myeliante
multiple
what is the function of schwann cells
wrap around axons (myelination) to speed the travel of action potentials in the PNS
how many axons does each schwann cell myelinate
one
what type of neuron detects light touch in the hands
pseudo-unipolar neuron
which root of the spinal cord does sensory information pass through
dorsal root
which root of the spinal cord does motor information pass through
ventral root
where in the spinal cord do somatic motor neurons (controlling skeletal muscle) start
ventral horn of the gray matter in the spinal cord
where in the spinal cord do autonomic motor neurons (controlling cardiac muscle, smooth muscle, and glands) start
lateral horn of the gray matter in the spinal cord
what CNS structure makes decision when a damaging stimulus is detected
- spinal cord recognizes and reacts to damaging stimuli
- brain is not needed because it would take more time to react
how many somatic motor neurons are needed from the spinal cord to skeletal muscle
one
how many autonomic motor neurons re needed from the spinal cord to cardiac muscle/smooth muscle/glands
two
define the autonomic ganglion
- collection of cell bodies outside of the CNS
- where the synapse is between a motor neuron from the spinal cord and a motor neuron going to the effector
what do all autonomic responses go through
autonomic ganglion
what is the resting membrane potential of neurons
-70 mv
what are most neurotransmitters made from
amino acids
why are neurotransmitters made from amino acids
- can be easily made
- can be easily destroyed
- can be vacuumed back into the axon that released them
what do neurotransmitters being released and binding to gated channels cause in the cell membrane
- depolarization
OR - hyperpoalrization
define depolarization
- movement of resting membrane potential towards zero
- exciting, making it more likely that an action potential will fire
what is the threshold for depolarization and when an action potential will occur
-55 mv
define hyperpolarization
- movement of resting membrane potential farther from zero
- inhibiting, making it less likely that an action potential will fire
define GABA
- gamma aminobutyric acid
- inhibiting neurotransmitter
- causing hyperpolarization
can an action potential be stopped once it hits the trigger zone
no
describe summation in nuerons
multiple axons firing to get the depolarization wave to reach the trigger zone at a level that will create an action potential at the trigger zone
describe how GABA causes hyperpolarization
- release of GABA will cause Cl- to enter the neuron
- a negative ion entering the neuron will cause hyperpolarization
define the refractory period in neurons
- time when another action potential cannot be fired until the first action potential has finished
- must wait for the membrane to be repolarized
- takes about 1 millisecond
can action potentials summate in axons
- no
- refractory period
what are the two parts of the refractory period of a neuron
- absolute
- relative
describe the absolute division of the refractory period of a neuron
- occurs first during the depolarization and repolarization phases
- nothing will happen if another action potential is fired
describe the relative division of the refractory period of a neuron
- occurs after the absolute division
- during hyperpolarization until the resting membrane potential reaches -70 mv
- another action potential firing will cause a weak reaction
describe why an action potential won’t split into 2 going in opposite directions while traveling down an axon
the refractory period will be in the area right behind the action potential so the action potential cannot start moving backwards
define telencephalon
cerebrum
what surrounds the cerebrum
cerebral cortex
define cerebral cortex
- surrounds the cerebrum
- made of gray matter
- neuronal cell bodies and dendrites
describe the separation of the cerebrum
- divided into 2 hemispheres: left and right
- separated by the longitudinal fissure
define matencephalon
cerebellum
what does cerebellum literally translate to
little cerebrum
what are the functions of the cerebellum
- coordination of movements
- some autopilot functions communicating with the frontal lobe