The Nervous system Flashcards
What are the functions of the nervous system?
- Monitor for changes inside and outside the body; Sensory input
- Process and interperet sensory info and decide what to do; Integration of information
- Creates response by activating muscles or glands; Motor output
Sensory imput
- Information gathered from the senses
- example; you smell smoke
Integration
- CNS decides what to do and sends out a response
- example; Brain takes in sensory info (small smoke) processes it, brain decides to tell your muscles to get you up so you can look for the the source of the smell
Motor output
- Signal travels through efferent pathway to effector organ
- example; muscles contract in response to message from the brain
example of an effector
- Sweat glands
- Muscles
- Mucous cells
Sensory input —> _______
- Afferent
Motor output —-> ________
- Efferent
PNS
- Peripheral nervous system
- spinal and cranial nerves
- Nerves comming out of CNS; communicate between CNS and the rest of the body
CNS
- Central Nervous system
- Brain and spinal cord
- Responsible for integration
- Multipolar cells
What are the major cells of the nervous system? what do they release?
- Neurons
- Chemicals called neurotransmitters
Name the divisions of the PNS
- PNS
- Sensory division (afferent)
- Motor division (efferent)
- Somatic nervous system
- Autonomic nervous system:
Sympathetic division
Parasympathetic division
What does the sensory division of the PNS do?
- Sends info/ Conducts impulses to CNS
What does the motor division of the PNS do?
- Sends info/ conducts impulses from CNS to effectors (muscles/glands)
What does the somatic nervous system of the motor division of the PNS do?
- controls voluntary movement
- conducts impulses from CNS to skeletal muscles
What does the Autonomic nervous system of the motor division of the PNS do?
- Responsible for involuntary (visceral action)
- Conducts impulses from the CNS to cardiac muscles, smooth muscles and glands
What does the sympathetic nervous system do?
- Fight or flight
- Mobilizes body systems during activity
What does the parasympathetic nervous system do?
- Conserves energy
- Promotes house-keeping functions during rest (breathing, digestion, etc)
- Rest and digest
2 types of cells in nervous tissue
- Neurons; nerve cells
- Neuroglia; support cells
Neurons are highly _______ for special _______.
- Modified
- Functions
When a message is comming down an axon; ______ are flowing.
- ions
Definition of synapses
- Point of close contact between 2 neurons or a neuron and effector cell
Definition of synaptic cleft
- Fluid filled space at a synapse
Definition Pre-synaptic cell
- neuron conducting impulse towards a cell body
Definition of Post-synaptic cell
- Neuron conducting impulses away from a cell body
What is an action potential?
- An electrical impulse generated and conducted by an axon upon stimulation
Action potential underline the basic functioning of the __________
- Nervous system
What is happening as an impulse travels through a neuron?
- Ions are moving in and out of the axon
How do action potentials work?
- Resting membrane potential is possible because concentration gradient is maintained by Na+/K+ pump
- At rest the membrane is slightly permeable to Na+
- ACTION POTENTIALS HAPPEN WHEN A CHANGE IN RESTING MEMBRANE POTENTIAL RESULTS FROM A STIMULUS
- MEMBRANE SUDDENLY BECOMES MORE PERMEABLE TO Na+
A change in membrane potential can result from….
- Alteration of ion concentrations on ether side of the membrane
- Anything that changes ion permeability of the membrane
A cell can change its ion permeability by opening and closing _______.
- Membrane channels
Within a membrane you have 4 major Ion (protein) channels
- Na+
- K+
- Cl-
- Ca2+
during an AP Na+ moves ______ the axon.
- Into the axon
During an AP K+ moves _____ of the axon.
- Out of the axon
During an AP Cl- moves ______ the axon.
- into the axon
During an AP Ca2+ moves _____ the axon.
- into the axon.
What insulates ions (keeps ions inside the axon)
- Myelin sheath
What is the trigger zone of an neuron?
- Axon Hillock
What is grey matter composed of?
- Cell bodies
what is white matter composed of?
- Mylenated axons
What is an action potential?
- An electrical impulse that travels down an axon
Why is potassium leaving the axon when it is repolarizing?
- To make the axon more negative.
How many states does a voltage gated K+ channel have and what are they?
- 2
- Opened
- Closed
How many states does a Na+ voltage-gated channel have? what are they?
- 3
- Opened
- Closed
- Inactivated
Sodium channels must close before another Action Potential can happen, true or false?
- True*
- If a strong enough stimulus happens inactive channels can be overriden
Resting state; Stage one
- K+ and Na+ voltage gated channels are both Closed
- More Na+ outside
- More K+ inside
- Na+/K+ ATPase keeps concentrations of ions inside and outside
- membrane is polarized
Depolarization; stage 2
- Na+ channel opens, lets Na+ ions floodinto axon
- K+ channel closed
- Flood of Na+ ions causes the inside of the cell to become more positive (depolarization)
- Action potential starts at -55mV threshold in neuron and peaks at +30mV
Repolarization
- Na+ voltage gated channel becomes innactive blocking more Na+ from entering the axon
- K+ voltage gated channels open releasing K+ into the ECFcausing the cellto become more negative (repolarize)
- Membrane potentialstarts moving back toward -70 mV (but not there yet)
Hyperpolarization
- Na+ voltage gated channels become closed
- K+ voltage gated-channels stay open letting more K+ ions out
- This makes the inside of the cell overly polarized below -70 mV
return to resting state
- Na+ voltage gated channel is closed
- K+ voltage gated channel is closed
- K+, Na+ leak channels return the ionic concentrations back to normal
- Na+/K+ ATPase maintains the differences
Long axons are called _________.
- Nerve fibers
The conducting region of the neuron is the ___________.
- Axon
The secretory region of the neuron is the ______________.
- Terminal boutons; axon terminals
Fatty insulation that wraps around the axon is called the myelin sheath, what are its functions?
- Electrically insulates (keeps ions in the axon)
- Increases transmission speed
Nodes of Ranvier
- Uninsulated gaps on axon
A cell at rest is __________.
- Slightly permeable to Na+
The permeabilities of Na+ and K+ across the membrane are ____________.
- Different
Absolute refractory period
- time period needed for Na+ channels to “re-set” themselves before the nerve can resopnd to another stimulus
Threshold
- Critical level of depolarization needed to generate an AP ( -55 to -50 mV)
APs are all-or-nothing events what does this mean?
- The AP happens completely or not at all; if threshold is not met an AP will not happen
What pump restores the ionic gradient after the AP is over?
- Na+/K+ pump
Do APs depend on stimulus strength?
- No
How does the CNS determine how strong a stimulus is?
- Strong stimuli generate APs more frequently over a given period of time than weak stimuli
conduction velocity varies across neurons; what would be the standard range?
100 m/ sec or more
The rate of an impulse propagation depends on….
- Axon diameter
- Degree of mylination
Multiple Sclerosis
- A condition where myelin is being slowly destroyed in the CNS; slows the signals sent by neurons
What does MS effect?
- Vision
- Muscle control
- Speech
- Urinary Incontinence
- it is an Autoimmune disease
Can AP signals be interupted? What chemicals would interupt these signals if so?
- yes
- Local Anesthetics
- Neurotoxins
- TTX
Local Anesthetics
- drugs used to block Na+ gated channels, stops siganls (APs) from being sent ——> No pain
Neurotoxins
- Toxin that effects neurons functioning
TTX
a toxin found in puffer fish that blocks Na+ channels neurotransmitters
What is the most common type of synapse?
- Chemical synapse
Chemical synapse
- Allow for release and reception of chemical neurotransmitters
What happens at a chemical synapse?
- An electrical signal gets turned into a chemical signal
How many Neurotransmitters have been identified?
- Over 50
What kind of effects do NTs have?
- Excititory and inhibitory effects
All neurons that stimulate skeletal muscles release ________.
- Acetylcholine (ACh)
Nicotinic receptors
- Are found at NMJ on SM
Muscarinic receptors
- Found on viseral effectors
Norepinephrine
- (NE) both a hormone and a NT caausng vasocontriction, increased heart rate, increased BP
- A feel good NT
Dopamine
- A feel good NT
- enhanced by L-dopa and amphetamines
- Reuptake blocked by cocaine
- decreased in parkinsons
- increased in schizophrenia
Seratonin
- Inhibitory
- Plays a role in sleep, appetite, nausea, migraine and regulating mood
What are the type of neural circuits?
- Diverging circuit/ Amplifying circuit
- Converging circuit/concentrating circuit
- Reverberating circuit/ Oscillating circuit
- Parallel after-discharge circuit
Synaptic delay
Graded Potential
- AP that ravels short distances
- a change in potential in the cell body
Re-uptake
- axon terminal takes NTs back
Selective Serotonin Re-uptake Inhibitors
- (SSRI) a class of drugs used as antidepresents
What happens to extra seratoinin or NTs?
- Enzyme degrades it
- Re-uptake
- Diffuses away
Diverging/ Amplifying circuit
- One imputs many out puts
- ex. A single neuron in the brain can activate 100 or more motor neurons in the spinal cord and thousands of SM fibers
Converging/ Concentrating circuit
- Many outputs, one imput
- ex. different sensory stimuli can all elict the same memory
Reverberating/Oscillating circuit
- Controlls rythmic activity
- ex. Involved in breathing, sleep wake cycle, and repetitive motor activities such as walking
Parallel after- discharge circuit
- Impulses reach output cell at different times, causing a burst of impulses called after discharge
- ex. May be involved in exacting mental processes such as mathematical calculations
The brain has a reward center….
- its involved in feeling pleasure and reward
- reward system consists of dopamine- releasing neurons in specific areas of the brain
- ex. Romantically in love; your brain releases large amounts of norepinephrine and releases dopamine
- oxytocin is also released but its a hormone
drug abuse hijacks the _________.
- Reward center
crystal meth artificially stimulates the brain to stop synthesising its own NTs, true or false?
- True, this promotes a vicious cycle of addiction
