The Nervous System Flashcards
nervous system functions
sensory input
integration of sensory input
homeostasis
mental activity
muscle control
Nerve impulse
the electrical charge that passes btwn neurons until it reaches a terminal
polar
more negative
resting membrane charge
-77 mv
at what value is an action potential generated
-55 mv
graded potential
a local event (involving one neuron) where there is an incomplete depolarization and no AP is generated
Propagation
movement of AP down the axon
myelin sheath
the covering on an axon that speeds up propagation
nodes of ranvier
the gaps between myelin sheath
saltatory conduction
jumping of an impulse between the nodes of ranvier
how does diameter affect propagation
larger diameter neurons conduct faster impulses
absolute refractory period
point at which the cell has fully depolarized, making it impossible for action potential to travel the opposite way up the axon
synapse
the gap btwn neurons, communication site
synapse components
- axon terminals of pre-synaptic neuron
- receptor sites of post-synaptic neuron
- synaptic cleft
which neurotransmitters are used for neurons ?
acetylcholine (primary for motor neurons of skeletal muscle)
norepinephrine + epinephrine used fir sympathetic nerve endings
what are the two types of incoming post-synaptic response, and what do they lead to?
- excitatory: membrane depolarization, influx of Na+
- inhibitory: hyper polarization, influx of k+
summation
an adding of all EPSP and IPSP’s, performed by the axon hillock
where on the muscles do NT’s bind?
receptor sarcolemmas of the muscle
neuromuscular junction
space between axon terminal motor end plates and the muscle fiber
refractory period
time during depolarization where muscle fibers are unable to respond to other stimuli
Nervous system organization
-central: brain and spine
-peripheral
-afferent/sensory
-efferent/motor:
-somatic
-autonomic:
-sympathetic
-parasympathetic
lobes of the cerebrum
-frontal
-occipital
-parietal
-temporal
-insular (emotion/self perception, sensorimotor processing)
-cerebral cortex (memory, thinking, learning, reasoning)
-motor cortex (voluntary muscle control, skill acquisition)
diencephalon
portion of the brain which contains the thalamus (sensory input center) and hypothalamus (endocrine control, autonomic NS, homeostasis)
cerebellum
portion of the brain which coordinates complex movement, accounts for body position/timing
brainstem
connects cerebrum to spinal cord, houses all sensory and motor nerves, contains pons, midbrain, and medulla
spinal cord
connects to midbrain, allows for 2 way nerve impulse conduction
sensory fibers
afferent, carry signals from sensory receptors to higher levels of CNS (dorsal root)
motor fibers
efferent, carry impulses from brain to spinal cord to target organs (ventral root)
joint kinesthetic receptors
receptors of the sensory NS w/in the joint capsule, sensitive to joint angle changes
muscle spindles
receptors of the sensory NS, relay info ab how much a muscle is stretched
Golgi tendon organs
receptors of the sensory NS, measure tension applied to tendons
autonomic nervous system
innervates involuntary muscle/glands
sympathetic nervous system
prepares the body for exercise by increasing HR, respiration, blood pressure thru broncho and vaso dilation
parasympathetic ns
active during rest, decreases HR, respiration , blood pressure thru broncho and vaso restriction
dual innervation
the autonomic NS is innervated with both sympathetic and parasympathetic divisions
cholinergic neurons
bind acetylcholine for use by the ANS, can be either nicotinic or muscarinic
adrenergic neurons
bind norepinephrine and epinephrine for use by the ANS
what reflex lowers HR?
parasympathetic of vagus nerve
what reflex raises HR?
symp reflex of cardiac accelerator
sensory input process
- receptors detect sensation
- sensory input travels to CNS (via afferent neurons)
- Impulse terminates in one of 5 integration centers
what are the 5 integration centers?
- spinal cord (simple reflex)
- lower brain stem (subconscious motor rxns)
- cerebellum (subconscious gross motor)
- thalamus (conscious movement, response to stimuli)
- cerebral cortex (learned response)
reflex arc
- sensory impulse terminates in the spinal cord
- impulse is transmitted to motor neuron
- impulse transmitted to muscle for involuntary reaction
what receptors initiate reflex response
proprioceptors and chemoreceptors
chemoreceptors
specialized free nerve endings,
- muscle spindles: info on muscle length
- Golgi tendon organs: muscle tension
proprioceptors
same as joint kinesthetic receptors, sense body position and limb movement, divided into free nerve endings, pacinian corpuscles, and Golgi receptors
Muscle spindles
type of chemoreceptor found between muscle fibers, sends info about length, contractile state, rate of change, resist over stretching
Golgi tendon organs
sensory receptors imbedded in tendons, sensitive to tension in the muscle, inhibit agonists and excite antagonists when stimulated by excessive tension
