Nervous System Flashcards
what is the central nervous system comprised of (CND)
Brain and spinal cord
Purpose of the nervous system
Gather information, process it and determine a appropriate response
Sensory input
Sensory receptors detect stimuli
Integration
How the nervous system processes information
Motor output
Activated muscles and glands
What is the PNS for
Sensory input: motor output
What is the PNS
Cranial nerves and spinal nerves
How is the PNS and CNS connected
The PNS is the communication lines between the CNS and the rest of the body
Motor division
Conducts impulses from CNS to effectors
What are effectors
Muscles and glands
What is sensory division
Conducts impulse from receptors to CNS
Somatic nervous system
Conducts impulses from CNS to skeletal muscles
Do you have control over the SNS
Yes you have control (voluntary) over the somatic nervous system
Autonomic nervous system
Conducts impulses from CNS to cardiac muscles and glands
Do you have control over the autonomic nervous system
No control (involuntary)
Sympathetic division
Fight or flight
Parasympathetic division
Conserves energy, rest and digest
Nervous tissue
2 types of cells, neurons, and Schwann cells
Neurons
They are cells that conduct impulses
Schwann cells
Support cells and nourish them, wrap around neurons, impulses can’t pass through
Cell body
Contain nucleus, biggest part of neuron, if damaged the whole neuron dies
Dendrites
Branch from cell body, Carey a nerve impulse TO CELL BODY
Axon
Long branch from cell body, Carry’s impulses AWAY FROM CELL BODY
Myelin sheath
Made of Schwann cells wrapped around the axon
Node of ranvier
Gaps of exposed axon between Schwann cells
Axon terminal
Ends of axon, does not touch other cells, the impulse jumps the gap to continue
3 types of neurons
Sensory, relay, and motor
Sensory neurons
Detects stimulus and take impulse to CNS
What do sensory neurons look like
The have long dendrites and short axons
Inter-neuron/ relay neuron
They interpret sensory information and transmit impulses within the CNS
What do really neurons look like
They have long of axons and dendrites
Where are relay neurons
Only in the CNS (brain and spinal cord
Motor neuron
They transmit impulses FROM THE CNS
What do motor neurons do
They send impulses from the CNS to effectors (glands/ muscles)
Where is the cell body of motor neurons located
Mostly in the spinal cord
What do motor neurons look like
Long axons and short dendrites
What is the order of the 3 neurons
1 sensory neurons get stimuli and send the message which is eventually picked up by 2 relay neurons which send the message within the CNS which eventually reach 3 motor neurons which then figure out a response and send it back out
Where are sensory receptors
All over but you have many in the skin
What are sensory receptors
Dendrites
What is the CNS physically made of
Internurons (relay) no sensory or motor
What is afferent
Sensory neurons in the PNS
What is efferent
Motor neurons in the PNS
What is a nerve
They are a BUNDLE OF NURON PROCESSES ( axons and dendrites)
What kind of neurons do nerves have
Sensory or motor NO RELAY
Where are nerves found and what are they
The are ONLY found in the PNS and are a cable bundle of axons and nerve fibres
What is a reflex arc
It is an involuntary reflex which makes it so you can respond to stimuli quickly without your brain
How many step in the reflex arc
6
What is the first step in the reflex arc
Receptor sense high pain and that starts and impulse (affecter)
Step 2 in the reflex arc
Sensory neurons in PNS send the impulse along the dendrite to the cell body and then along the axon and eventually to the spinal cord
Step 3 reflex arc
The interneurons within the spinal cord pass the message to motor neurons
Step 4 reflex arc
The motor neurons pass the impulse the short dendrite to the cell body then along the axon which leads the muscle
Step 5 reflex arc
The effectors revive the message and reacts to pull away from stimuli
Is the reflex arc a conscious arc
No
Step 6 reflex arc
Step 1-5 happen before the brain had a chance to “think” but pain is not felt until brain receives the impulse
What is an action potential
It is the conduction of an impulse across a neuron
Characteristics of impulses
Temporary, quick and repeatable
Steps of action potential (1)
The cell body becomes depolarized due to a signal
How does the axon get depolarized
First a threshold is reached (-55mv), the Na + gates open and flud in
Resting action potential pumps
Na+/k+ pump is on so it pumps Na+ out and k+ in (3 Na out 2 K in)
Resting potential gates
Na+ gate is closed and K + gate closed
Where are Na+ and K+ during resting potential
Na + outside K+ inside (there are leak channels and that’s why you need the pump)
Pumps during depolarization
The pump turns off
Repolarization pumps
The pump is off
Repolarization gates
Na+ gates are closed and K+ gates are open
Why are K+ gates open during Repolarization
To help shift the charge
Can the neuron conduct and impulse when Repolarization
No, necessary the ions are not restored (Na+ and K+)
Recovery/ Refactory pumps
The pump is on to get the Na + out and K + in
Refractory/ recovery gates
All gates closed
Where are the gates on a neuron
All over cell membrane
What is salty banana
K+ inside and 2x Na+ outside when in resting potential
Order of action potential
1-resting-2 depolarized-3 repolorize-4 refractory/recovery ( happens all the way down )
Saltatory conduction =
Impulses are faster in myelinated neuron because they jump from node to node
Characteristics of action potential
Stimulus must exceed threshold, all are none response
What is an all or none response
The stimuli must reach a threshold, so all impulses are the same (do different things)
How many impulses can happen at once
Neurons can have many or one at the same time in different locations
What do stronger stimuli do
They send repeated impulses
Can you stop an impulse
No you can’t stop it or send a new one till it’s done sending
What is an action potential
When a stimulated neuron sends an impulse
How do impulses get from one neuron to another
Neurotransmitters are sent from one neuron and they lock into receptors on the dendrites of the next neuron
How are impulse conducted within the neuron
Electrically
How are impulses conducted between neurons
Chemically
Where are neurotransmitters stored
In vesicals at the end of axon terminals (axon bulbs)
What is the somatic cleft
The gap between neurons
How are excess neurotransmitters removed from the somatic cleft
With enzymatic breakdown by reabsorption so the stimulus stops
What is a presynaptic neuron
Is is the neuron the impulse is coming from
What is the postsynaptif neuron
It is the neuron receiving the nerve impulse via neurotransmitters
How does the next neuron chemically get the impulse
Neurotransmitter receptors take neurotransmitters in
How many steps of the transmission across the synapse
8
Step 1 across the synapse
The impulse reaches the end of the axon and is at axon bulb
Step 2 across the synapse
The depolarization causes the calcium ions to flood into the axon bulb which pull the vesicles to the presynaptic membrane
Step 3 across the synapse
Neurotransmitters go across the synaptic cleft and activate sodium gates
Step 4 across the synapse
Sodium floods into the POSTSYNAPTIC membrane and causing the next neuron to depolarize
6-7 steps of across the synapse
Action potential continues down the postsynaptic neuron
Step 8 of across the synapse
Enzymes are released to neutralize neurotransmitters in the sympathetic cleft or the neurotransmitters are reabsorbed into axon bulb
