Phys. Unit 2: Nervous System Flashcards
Nervous system
major controlling, regulating, and communicating system
How does the nervous system coordinate the body?
- It receives stimuli from external environment and transmits messages to central nervous system (CNS)
- The CNS processes the information and determines response
- CNS issues commands primarily to muscle and gland cells to carry
out response
What does the central nervous system deal with?
central nervous system
brain and spinal cord
(CNS)
What does the peripheral nervous system deal with?
peripheral nervous system
nerves and ganglia
(PNS)
nerve
bundle of nerve fibers
ganglion
knot-like swelling in a nerve where neuron cell bodies of PNS are concentrated.
what is a neuron
a nerve cell
What is included in the sensory category/web?
sensory
subunit fron the PNS
afferent, carries signals from receptors
(A for arrive, afferent)
visceral sensory
carries signal from viscera (heart, lungs, stomach, organs)
somatic sensory
carries signal from receptors in the skin, muscles, bones, joints
What is included in the motor web?
motor
Subunit of the PNS
efferent, from nervous system to effectors
(e for exit, efferent)
somatic motor
to skeletal muscles
visceral motor
to glands; smooth muscle
3 properties of neurons
excitability, conductivity, and secretion
excitability
ability to respond to a stimuli
conductivity
produce electrical signals conducted to other cells
secretion
when a signal reaches the end of an axon, the neuron secretes a neurotransmitter that cross the gap and stimulates the next cell.
sensory neurons
afferent, detect stimuli
Ex: light, heat pressure
interneurons
receives signal from other neurons, makes the decisions, entirely in CNS
‘gossip-ers’
motor neurons
efferent, send signals out to muscles and gland cells
function of sensory (afferent) neurons
recieve signals and carry signals to spinal cord and brain
cell body
(otherwise called ‘soma’) contains nucleus and many organelles
*rough ER
neurites
extensions, reaching out to other cells
dendrites
primary sites for receiving signals from other neurons
axon
specialized for rapid conduction, long cylindrical
highway-electrical conduction
multipolar neuron
most common in CNS
1 axon, many dendrites
bipolar neuron
usually in ear or retina
1 axon, 1 dendrite
unipolar neuron
carry pain and touch signals to spinal cord
1 axon, small dendrite
anaxonic neurons
found in brain, retina, and adrenal gland
no axon, many dendrites
oligodendrocytes
bubble wrap of axons, form myelin sheets in CNS
axonal transport
2-way passage of proteins, organelles and other materials
anterograde transport
movement away from cell body, down the axon
retrograde transport
movement toward cell body and up the axon
fast axonal transport
moves organelles
200mm/day
slow axonal transport
stop-and-go fashion
0.2mm/day
moves enzyme down axon
Schwann Cells
form myelin sheath and assist regeneration of damaged fibers
satellite cells
surround nerve cell bodies, provide insulation and regulate chemical environment
myelin sheath
spiral layers of insulation around axon
formed by Schwann cells in PNS and oligodendrocytes in CNS
20% protein 80% lipid
myelination
production of myelin sheath
begins during fetal development, which is why babies need fat in their milk
Nodes of Ranvier
gaps in the myelin sheath that speeds up conduction
neurolemma
thick, outermost coil, around a nerve axon
ependymal cells
line internal cavities of brain; secrete and circulate cerebrospinal fluid
microglia
macrophages, engulf debris, provide defense against pathogens
astrocytes
most abundant type of gilial cell, in the CNS; wide variety of functions:
nervous tissue framework
form scar tissue
adjust blood flow
*blood-brain barrier
electrical potential
difference in concentration of charged particles between two points. measured in volts
what is a current
flow of charged particles
anion
Cl-, negative charge
cation
Na+, positive charge
or Ca +2
polarization
something with electrical potential
resting membrane potential
charge difference across plasma membrane, typically *-70 millivolts *
speed a nerve signal travels down depends on:
diameter- larger axons conduct signals faster
presence or absence of myelin- myelin speeds up signal conduction
EX) small, unmyelinated: 0.2m/s
large, myelinated: 120m/s (270 mph)
unmyelinated axons have voltage gated-channels…
down entire length
myelinated axons have voltage gated channels where?
concentrated at the nodes
saltatory conduction
action potentials ‘jump’ from node to node
local potential
temporary, short-range change in voltage
characteristics of local potential (4)
graded, decremental, reversible, excitatory/inhibitory
depolarization
causing membrane potential to be less negative (more positive)
Ex: chemical binds to receptor and Na+ enters the cell
(step 3)
hyper polarization
causing membrane potential to be more negative (less positive)
Ex: chemical binds to receptor, opens and Cl- enters cell
action potential
rapid up/down change in voltage produced by the coordinated opening/closing of voltage gated channels
all or none law
if the threshold is reached, neuron fires up to maximum voltage. If threshold is not reached, nothing happens (does not fire)
decremental
get weaker with distance, the farther away it gets from the point of stimulation
irreversible
once started, an action potential travels all the way down, the axon can’t be stopped.
excitatory/inhibitory
make a neuron more or less likely to fire an action potential
electrical synapse
send signals electrically through gap junctions
+ very fast, faster than chemical synapses
- can’t integrate info/ make decisions
chemical synapse
send signals with neurotransmitters across a synaptic cleft
+ advanced info coding, site of learning and memory
- slower, requires more steps
ex: neuromuscular junction
synapse
point where axon terminal meets the next cell, not necessarily physical contact (synaptic cleft)
presynaptic neuron
transmitting signal and releasing neurotransmitters
postsynaptic neuron
responds to the neurotransmitters
axodendritic synapse
majority of our synapses
What are the 5 steps for a neuron-neuron synapse to happen?
transmission for neuron-neuron synapse
- Action potential arrives at end of axon of pesynaptic neuron
- presynaptic neuron releases neurotransmitters
- neurotransmitter binds to receptors on postsynaptic neuron
- binding can have excitatory or inhibiroty effect
- communication ends
What are the two steps need to end communication?
ending communication
-presynaptic ell stops releasing neurotransmitter
-neurotransmitter is cleared from synaptic cleft
neurotransmitter degradation
enzyme in synaptic cleft that breaks down neurotransmitter
One way of getting rid of excess molecules after ending communication:
reuptake
once broken up, the molecule can be reabsorbed into the axon terminal
One way of getting rid of excess molecules after ending communication:
diffusion
simply diffuse away into ECF
*many neurological drugs disrupt this process, also over 100 differnt neurotransmitters (ACh)
neural integration
ability to process, store and recall information and use it to make decisions
excitatory postsynaptic potential (EPSP)
voltage becomes more positive, close to threshold- more likely to fire an action potential
inhibitory postsynaptic potential (IPSP)
voltage becomes more negative, further away from threshold- less likely to fire
usually results in Cl- flowing into cell or K+ exiting cell
summation
adding up postsynaptic potentials and responding to their net effect
temporal summation
single synapse generate EPSPs so fast that each is generated before the previous one fades
Ex) one person yelling “go, go, go!”
spatial summation
EPSPs from different synapses add up to the threshold at an axon hillock
Ex) many people next to you yelling “go, go, go!”
presynaptic facilitation
Advisor to the King
whispering excitatory information, one presynaptic neuron enhanced another, increases likelihood of action potential
Ex: telling you to do a good thing
presynaptic inhibition
Advisor to the King
occurs when whispering inhibitory information, one neuron supresses another one, decreases the likelihood of an action potential
Ex: telling you to do a bad thing
Spinal cord physiology
What are the 4 regions of spinal cord?
cervical, thoracic, lumbar, sacral
top to bottom, neck to butt
conduction
nerve fibers conduct sensory and motor information up and down the spinal cord
neural integration
spinal neurons receive inputs from multiple sources, integrate it and execute appropriate output
Ex: bladder control
locomotion
spinal cord contains central pattern generators= groups of neurons that coordinate movement
reflexes
involuntary, response to stimuli, vital for posture and protection
*skip the brain
what sides are spinal tracts on?
both sides!
ascending tract
carry sensory info up
descending tract
carry motor info down
decussation
crossing of the midline so the brain senses and controls contralateral side of body
- left brain controls right side of body
contralateral
origin and destination are on opposite sides
-left side brain controls right side body
ipsilateral
origin and destination are on the same side, do not cross (decussation)
- left brain controls left side of body
ascending tract & orders
sensory info from periphery to brain
3 orders
1st order of ascending tract
detect stimuli and transmit signal to spinal cord or brainstem, receptors in PNS
2nd order of ascending tract
continue to the thalamus (relay center) in CNS
3rd order of ascending tract
carry up to cerebral cortex, in CNS
What is the function of the posterior funiculus?
posterior funiculus
Dorsal column medial lemniscus pathway or DCML
carries proprioceptions of limb and trunk, deep touch and vibration
What is the function of the anterolateral system?
anterolateral system
spinothalamic tract (STT)
carries sensations of l ight touch, itch, pressure and nocioception (damaged tissue)
sensory nerves
only afferent fibers, carries sensory receptors to CNS, rare!
motor nerves
composed only of efferent fibers; carry signals from CNS to muscles and glands
mixed nerves
consist of both afferent and efferent fibers
*most common type
What are reflexes?
reflexes
involuntary, quick stereotypes reaction (same thing will always happen)
somatic reflexes
somatic nervous system, skeletal muscle
monosynaptic reflex arc
one synapse between afferent and efferent neurons, very fast
polysynaptic reflex arc
multiple synapses on the way to the muscle, takes longer
What is the stretch reflex?
stretch reflex
myostatic, monosynaptic, when a muscle is stretched, it ‘fights back’ and contracts
Ex: knee jerk, head when falling asleep
- use reciproical inhibition same limb
- prevents muscles from working against each other
- in knee jerk, quads contract and hamstrings relax
What is the flexor reflex?
flexor reflex
withdrawl, polysynaptic
- quick contraction with withdrawl of a limb from an injurous stimulus
- use reciprical inhibition
- Ex: touching electrical fence and withdrawing hand
What is the crossed- extension reflex?
crossed- extension reflex
polysynaptic
Ex: step on a lego… both legs must move otherwise you will fall over
What is the golgi tendon reflex?
Golgi tendon reflex
inhibits muscle from contracting too strongly
- can be either mono or polysynaptic- it depends!
cerebrum
largest part of forebrain
- sensory perception, memory, thought, judgement
cerebellum
2nd largest part of brain
- motor coordination, locomotor ability
brainstem
rest of brain
- regulation of breathing, heart rate, sleep
Gray matter
nerve cell bodies, dendrites, synapses
white matter
bundles of nerve fibers
frontal lobe
executive functioning, emotional regulation
parietal lobe
senses (touch, taste, smell) -pain, temperature, pressure
temporal lobe
auditory process and hearing, recognizing language
occipital lobe
vision processing, location , depth
cognition
many areas
ex: banana (see a yellow thing, smell it, oh I can peel it!)
memory
info retrieval and storage
Alzheimers= anterograde amnesia- can’t remember new information
hippocampus
organizes cognitive information, memory consolidation
amygdala
emotional memory
What percent of daily calories consumed is used by the brain’s activity?
25%!
Glutamate and aspartate are…
Excitatory/inhibitory and IPSP or EPSP
excitatory= EPSP
Glycine and GABA are…
inhibitory= IPSP
What type of synapse is formed on the cell body of the postsynaptic neuron?
axosomatic
3 functions of neurotransmitters
They bind to receptors and alter the physiology of the postsynaptic cell.
They are released in response to stimulation.
They are synthesized by presynaptic neurons.
Enzyme amplification occurs at which type of synapse?
Excitatory adrenergic
The ability of your neurons to process information, store and recall information, and to make decisions is called neural____
integration
What would cause postsynaptic stimulation to end? 3
Enzymatic degradation of neurotransmitter in the synaptic cleft
Cessation of signals in the presynaptic nerve fiber
Diffusion of neurotransmitter from the synaptic cleft into extracellular fluid
Reuptake of neurotransmitter into the presynaptic knob
cholinergic uses what as a neurotransmitter
ACh
adrenergic uses what as a neurotransmitter
norepinephrine
The ability of a neuron to enhance the effect of another neuron is called what?
Presynaptic facilitation
describe the location of the initial segment of an axon
Between the axon hillock and first glial cell
what is the ANS?
autonomic nervous system
what does the ANS do?
regulate heart rate, blood pressure, body temp and urination and sexual functions.
*bodily homeostasis
-targets abdominal cavities
-does NOT innervate skeletal muscles
-does not require conscious intent
visceral reflexes
unconscious, automatic
same idea as somatic reflexes, reflex arc is the same
Ex: baroreflex
endocrine system
glands, tissues, and cells that secrete hormones
What are hormones?
hormones
chemical messengers that travel in the bloodstream to tissues and organs
what are the functions of the spinal cord
Conduction, locomotion, and reflexes
sympathetic division
promote activity/ fight or flight
increases heart rate and blood pressure
parasympathetic division
promote relaxing/ rest and digest
clams energy expenditure
enteric plexus
gut-brain
muscarinic receptors
found in organ muscle
nicotinic receptors
found on postganglionic cell bodies
norepinephrine
agernigic
alpha- usually excitatory
beta- usually inhibitory
sympathetic effects last longer than parasympathetic
**
dual innervation
most viscera have nerve fibers from para and sympathetic
- antagonistic effects (opposite)heart rate
- cooperative effects (together) saliva production
Not always necessary to produce opposite effects ex) blood pressure
spinal cord damage may effect what parts of the body?
bladder and bladder control
Characteristics of the nervous system
Nervous system
- responds quickly
- adapts quickly to long-term stimuli
- one organ effected, specific
Characteristics of the endocrine system
Endocrine system
- slow response, days affected
- adapts slowly to long-term stimuli
- very general, widespread effects, many organs
What is a target organ/cell?
target organ/ cell
can be in multiple places (organs)
organs and cells that have receptors for a hormone and can respond
hypothalamus
- forms floor and walls of their ventricle of brain
- regulates primative balance- sex drive, water balance
- many functions by pituitary gland
anterior pituitary
linked to hypothalamus by blood vessels
posterior pituitary
nerve tissue, not a true gland
posterior pituitary hormone
antidiuretic hormone (ADH)
increases water retention by kidneys
oxytocin
sexual arousal
stimulates contractions during birth
stimulates flow of milk during lactation
negative feedback inhibition
increases target organ hormone levels inhibit release of pituitary hormones
most common
ex) thyroid hormone
growth hormone
widespread effects on body tissues
stimulate bone and muscle growth (especially in childhood)
thyroid gland
largest gland, purely endocrine around trachea
releases TH
function: increases metabolic rate
parathyroid gland
4 small glands embedded in the thyroid
release PTH
increase blood calcium levels
hypocalcemia
low calcium
hypercalcemia
high calcium
adrenal gland
sits on top on kidneys (hat)
adrenal hormones
catecholamines
