General Nervous System Flashcards
central nervous system
brain and spinal cord
peripheral nervous system
the sensory and motor neurons that connect the central nervous system to the rest of the body
What two systems are peripheral nervous system divided into?
somatic and autonomic
Which systems receives info from an external system?
Somatic
What system carries sensory information sent to the brain
Somatic nervous system
list 4 properties of somatic system
external, voluntary, cranial nerves and myelinated spinal nerves, targets skin skeletal and tendon, connect spinal to body
How is an electrical gradient established
Difference in charge, like when outside neuron is more positive than inside at resting
autonimic nervous system sends information from…
Internal environment
Which system is under voluntary control
Somatic
What does the autonomic nervous system involuntarily control?
Glandular secretions (sweat) and cardiac muscles (heart rate, blood pressure digestion, breathing)
what impact does sympathetic system have on adrenal gland
triggers secretion of epinephrine and norepehrine in the medulla
when is parasympathetic activated
when body is at homeostasis
which system is our fight or flight response
sympathetic
what does parasympathetic system use as a neurotransmitter to control organ response
acetylcholine (ach)
neurotransmitter
chemical messengers that cross the synaptic gaps between neurons
synapse
the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron
What is the subdivision of autonomic nervous system?
Parasympathetic and sympathetic
Name three properties of the sympathetic system?
Speeds up processes such as heart rate, are nerves that transmit impulses when stressed, connects spinal cord to rest of body
Name three properties of the parasympathetic system?
Transmits impulses when body returns back to its normal state after stress, slows down heart rate and blood pressure, connects brain to rest of body
The nervous system is composed of only two main types of cells:
Neurons and glial cells
glial cells
cells in the nervous system that support, nourish, and protect neurons. Defending against infections and removing waste. They account for about half of the volume of the nervous system.
Neurons
respond to physical and chemical stimuli, to conduct electrochemical signal
What are the three types of neurons
sensory, motor, interneurons/integration
motor output
a response to integrated stimuli; the response activates muscles or glands
sensory input
Information gathered by sensory receptors to the central nervous system. Located in ganglia next to the spinal
Interneurons
neurons within the brain and spinal cord that communicate and intervene between the sensory inputs and motor outputs. They act as a link between the sensory and motor neurons. Located in CNS
Three components of the neuron
cell body, dendrites, axon
Dendrites
Branchlike parts of a neuron that receive stimuli
cell body
Largest part of a typical neuron; contains the nucleus and the cytoplasm
Axon
long cylinder carrying impulse to next neuron or to effector.
effectors of autonomic nervous system
cardiac muscle, smooth muscle, and glands
Neurilemma function
helps regenerate injured axons/ neuron. Neurons without a neurilemma cannot
reflex arc
A direct connection between a sensory neuron and a motor neuron that allows an extremely rapid response to a stimulus, often without conscious brain involvement. Occurs through spinal cord
In steps, explain the reflex arc
- Receptors sense pressure and initiate an impulse in the sensory neuron
Why, after stepping on a stone, you would not feel pain or cry out until after your foot was withdrawn?
Because reflex arc moves directly to and from the CNS before the brain centres involved with voluntary control have time to process the sensory information.
5 components that make up the reflex arc
- Receptor
near
70mV
the membrane registers at
40mV
action potential
a nerve impulse; a brief electrical charge that travels down an axon
The resting potential
The difference in electric charge between the inside and outside of a neuron’s cell membrane
The concentration of potassium at resting potential is
Is high inside the neuron
The concentration of sodium at resting potential is
High outside the neuron
The relative charge outside the neuron is
more positive than inside the neuron
What causes the opening of sodium channels?
When the dendrites of a neuron receive a stimulus the cell membrane becomes more permeable to Na+ by opening specific sodium ion channels.
What stops action potentials from moving backward along cell membrane?
It can only produce another action potential at resting, so during refractory it cannot produce another because it is hyper polarized
How does sodium enter the neuron?
Na+ enters the neuron by facilitated diffusion
Depolarization
The process during the action potential when sodium is enters the neuron causing the inside to become more positive.
Repolarization
Return of the cell to resting state, caused by reentry of potassium into the cell while sodium exits the cell and thus restoring a positive charge
Hyperpolarization
the outside of the neuron is more positive than when it is at the resting potential
What causes hyperpolarization
the potassium channels close more slowly, more potassium ions leave the neuron than sodium ions that have entered the neuron, leaving the neuron in a state of hyperpolarization
What restores the resting neuron potential?
a sodium-potassium pump begins to pump 3 Na+ out of the neuron and pumps 2 K+ into the neuron.
refractory period
The time taken for the membrane to return to the resting potential after repolarization
Complete repolarization must occur before
There’s another nerve impulse
Order of events for membrane potential
- Resting Membrane
threshold level of a neuron
the minimum level of stimulus required to trigger action potential
Any level below -55mV will…
NOT generate a nerve impulse
all-or-none response
When the threshold level of a neuron has been reached, the action potential generated creates a complete response. Increasing the intensity of a stimulus does not increase the intensity of the action potential. — A nerve fibre will respond either completely or not at all to a stimulus
What two ways can the intensity of stimulus be increased?
a) Increase the number of neurons being stimulated
How does autonomic system compare to somatic?
Autonomic is involuntary, gets info from internal environment, controls glandular secretions and cardiac muscles. Somatic is voluntary and from external environment and connects the CNS to skeletal muscles
The relative charge inside a neuron is….?
More negative
Where do motor neurons carry information to?
Skeletal muscles
What is a synapse?
The connection between two neurons, or a neuron and an effector
neuromuscular junction
synapse between a motor neuron and a skeletal muscle
Neurotransmitters
chemical messengers that cross between neurons or from neuron to effector
excitatory neurotransmitters
chemicals released from a neuron that excite the next neuron into firing
inhibitory neurotransmitters
inhibit the next cell from firing
At each stage in membrane potential graph, what is happening? What is the charges?
Resting its at -70MV, depolarization na channels open and they diffuse into the inside of the neuron making it positive on the inside , repolarization k channels open and they move inside making it more negative
Membrane potential
the voltage difference across a membrane
sodium-potassium pump
a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell
How is nerve impulse transmitted from one neuron to another if the neurons do not touch
If its myelinated it goes through nodes of ranvier and synapse, if its not its through depolarization
What are the steps for How is nerve impulse transmitted from one neuron to another if the neurons do not touch
Impulse nerve reaches end of axon, neurotransmitters release to synapse, vessels break down
What system is sensory and motor neurons part of
Somatic
What is acetylcholine?
This is a primary neurotransmitter that transmits impulses across the synaptic cleft.
Is acetylcholine excitatory or inhibitory?
excitatory; produces muscles contractions, memory formation
What does it mean if you’re acetylcholine deficit?
Alzheimer’s
Where’s acetylcholine found
In motor neurons
What is the cause of depolarization?
When many action potentials are generated one after another along the cell membrane and sodium ions rush into the cell
If axon is myelinated, action potential is only generated at
nodes of ranvier
Myelination
Axon part that speeds the transmission of nerve impulses from neuron to neuron
How can acetylcholine be a problem?
If continuous presence, it’ll cause a constant state of depolarization as sodium channels are constantly open
membrane potential
the voltage difference across a membrane
If the neurotransmitter is inhibitory, the receptor will trigger
potassium channels to open, allowing potassium ions to flow out. Results in a more negative transmembrane potential resulting in hyperpolarization
Causes hyperpolarization
Slow to close K+ channels and slow to open sodium channels,
What happens if stimulus causes sufficient depolarization to reach the threshold potential of the membrane
Action potential in all or none response
Myelinated neurons make up
white matter of cns
If the motor area of the right cerebral cortex was damaged in an automobile accident, which side of the body would be affected
Left side of body. each hemisphere of the brain controls the opposite side of the body.
White matter
myelinated axons
grey matter
unmyelinated neuron cell bodies and short, unmyelinated axons
synapse transmission steps
- impulse travels to synaptic terminal
