Nervous System Flashcards
How is a signal passed through the nervous system?
stimulus - receptor - sensory neurone - relay neurone - motor neurone - effector - response
What does a thermoreceptor sense?
heat or cold
What does a meissner’s corpuscle sense?
touch
What does a nociceptor sense?
pain
What does a pacinian corpuscle sense?
pressure
Where are internal receptors located?
hypothalamus
What are the name of receptors for light?
photoreceptors
What are the name of receptors for chemicals?
chemoreceptor
What are the name of receptors for temperature?
Thermoreceptor
What are the name of receptors for touch/pressure (physical but not pain)?
Mechanoreceptor
What are the name of receptors for position/movement?
Proprioreceptor
What are 4 benefits of a simple 3 neurone reflex arc?
signal is passed on faster (rapid response)
protective
unlearnt - so is reaction to keep safe
predator avoidance
What does the CNS consist of?
relay neurone, spinal cord, brain
What is the CNS?
Central Nervous System
What neurones are in the PNS?
Motor and sensory neurones
WHat is the PNS?
Peripheral Nervous System
What are involuntary reactions?
things we do not think about
WHat is the function of the brain in nervous response?
learning from the stimulus, coordinating/’deciding’ a response
What are the 2 types of nervous reaction?
autonomic and somatic
What 3 ways can autonomic reactions be categorised?
sympathetic, parasympathetic, enteric
What is sympathetic response?
fight or flight
What is parasympathetic response?
rest and ‘digest’
What is enteric response?
Gastrointestinal (digestion)
What is a somatic response?
movements and decisions including reflex arc
What does the spinal cord consist of?
Dorsal root, root ganglion, and horn
Ventral root, and horn
Central Canal
White matter
Grey Matter
Meninges
What is the Grey matter made of?
synapses and cell bodies of neurone
What is the white matter made of?
myelin sheath (lipid which is electrical insulator)
What is the central canal?
contains spinal fluid which is a shock absorber
What is the meninges?
protective layer around brain and spinal cord
What is the cell body centron?
the spherical part of a neuron that contains the nucleus and other major organelles
What are dendrites?
a short branched extension of a nerve cell, along which impulses received from other cells at synapses are transmitted to the cell body
What is the myelin sheath?
Layer of lipids around axon, act as electrical insulator, action potential passed across nodes of ranvier
What are the nodes of ranvier?
only points on axon where action potential can occur, speeds up transmission across axon as it jumps from node to node
What is a synapse?
a junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.
What types of proteins are in an axon membrane that allow for movement of molecules?
channel protein, gated channel protein for sodium or potassium, Na/K+ pump (carrier protein)
What is the resting potential of the axon?
-70mV where there is a more positive outside and more negative inside
What is the action potential of the axon?
+40mV where there is a more negative outside and more positive inside
When the axon is at resting potential what helps maintain the -70mV charge?
sodium potassium pump 3 Na+ out and 2 K+ in
Other negative ions like Cl- and molecules like ATP-
Some K+ Gated Channels are leaky/open so will diffuse out of axon
Most Na+ Gated Channels are closed so will not diffuse back in axon
Active transport takes place
When is a membrane polarised?
when at resting potential
When is a membrane depolarised?
after stimuli occurs and threshold passed and the charge inside axon is becoming more positive
When is membrane repolarised?
after action potential as charge in axon is decreasing
When is membrane hyperpolarised?
charge of axon has dropped below that of the resting potential
For depolarisation to occur what happens?
Gated Na+ Channel Opens
For repolarisation to occur what happens?
Gated K+ channel opens
For hyperpolarisation to occur what happens?
Gated K+ channels are very slow at closing meaning the charge drops below resting potential and is brought back to resting potential by the sodium potassium pump
What is the refractory period?
after hyperpolarisation occurs the time it takes for the charge to return to resting potential at -70mV
What is the threshold on a membrane potential?
the point where if it is reached after stimulus it triggers an action potential
What are the parts of the synapse?
Pre-synaptic end bulb
Post-synaptic membrane
Synaptic cleft
For the signal to pass across the synapse what has to happen to the impulse?
change from electrical impulse to chemical impulse
What triggers the movement of the vesicles of neurotransmitter?
diffusion of calcium ions into the pre-synaptic end bulb
How do the vesicles of neurotransmitter exit the pre synaptic end bulb?
exocytosis, neurotransmitter released into synaptic cleft
How does post-synaptic membrane receive transmission?
through receptors, which are sodium channels
How can neurotransmitter be removed from synaptic cleft/stopped sending transmission?
can be reabsorbed - calcium prevented entering and actively transported out
broken down
What is an example of a neurotransmitter?
acetyl choline
How can acetyl choline be broken down?
through enzyme acetylcholinesterase which produces choline and ethanoic acid
WHat is the autonomic nervous system responsible for?
regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal. It contains three anatomically distinct divisions: sympathetic, parasympathetic, and enteric.
What is the somatic nervous system responsible for?
regulating the voluntary movements of the body, the somatic nervous system is also responsible for a specific type of involuntary muscle responses known as reflexes, controlled by a neural pathway known as the reflex arc.
What are ganglia?
Collection of neurone connections outside of the central nervous system. Allows for synaptic relays between nerves in the peripheral nervous system.
What is the affect of sedatives?
inhibits nervous system, fewer action potentials in post-synaptic neurone
WHat is the affect of stimulants?
stimulates nervous system, allows more action potentials in post-synaptic neurone
How do drugs mimicking action of neurotransmitter affect transmission of impulses?
drug molecule has same shape as the neurotransmitter and bind to receptors in post-synaptic membrane, increases frequency of depolarisation and impulse generation
How do drugs preventing breakdown of neurotransmitter affect transmission of impulses?
Inhibit acetylcholinesterase, acetylcholine remains in synaptic cleft, causing repeated firing of impulse in postsynaptic neurone
How does nerve gas work?
Inhibits acetylcholinesterase at neuromuscular synapses, generates repeated, uncontrolled contractions of muscles. Can break bones.
What are psychoactive drugs?
Act primarily on central nervous system, can affect different neurotransmitters or receptors. Alters brain function and e.g. perception, mood, consciousness, behaviour.
What is drug tolerance in relation to nicotine?
Nicotine mimics acetylcholine stimulates post-synaptic impulses as binds to receptors. Is not broken-down like acetylcholine, remains in the synaptic cleft. Will continue to initiate impulses, but body will become habituated to this drug and thus require more and more to be taken to stimulate the same response. This is drug tolerance.
What is a Schwann cell?
a type of glial cell that produces the myelin sheath around neuronal axons in the peripheral nervous system
