m3 + 4 lect. - peripheral nervous system Flashcards
what are the two sub-systems that make up the nervous system?
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
what does the central nervous system do?
-receives and processes info
-learn and form memories
-apply in decisions/initiates actions
what does the peripheral nervous system do?
transmits signals between the CNS and the body
what are two types of neurons in the peripheral nervous system?
motor neurons
sensory neurons
what are the two sub-systems of motor neurons?
somatic nervous system
autonomic nervous system
what are the two sub-divisions of the autonomic nervous system?
sympathetic (“fight or flight”)
parasympathetic (“rest and digest”)
what are the receptors of the sympathetic nervous system?
adrenergic receptors
what are the receptors of the parasympathetic nervous system?
cholinergic receptors
what are the adrenergic receptors?
alpha and beta
what are the cholinergic receptors?
muscarinic and nicotinic
what do sensory (afferent) neurons do?
go to the brain or spinal cord
collect info
- hearing, touch, pain, smell, vision, taste, temperature
what do the motor (efferent) neurons do?
- go away from the brain or spinal cord
- send info out to muscle to perform action or reflex
what happens in the somatic nervous system?
voluntary skeletal muscle actions via NMJ
- acetylcholine stimulates action potential
what happens in the autonomic nervous system?
involuntary actions
- cardiac muscle
- smooth muscle
- glands
how many cranial and spinal nerves are there in the PNS?
12 cranial nerve pairs
31 spinal nerve pairs
what are nerves made of?
nerve fibers (axons)
-sensory, motor, mixed
what stimulates action potential in the sympathetic nervous system?
epinephrine (hormone)
nor-epinephrine (neurotransmitter)
what is the covering of a whole nerve called?
epineurium
what is the covering of a bundle of nerve fibers called?
perinerium
what is a bundle of nerve fibers called?
fascicle
- sensory or motor
what covers individual myelinated and unmyelinated nerve fibers?
endoneurium
what does myelination do?
protect
speed up conduction
what is a ganglion?
a distended area containing cell bodies/synpases
- “gray mater”
what does generator potentials mean?
direct stimulation of a receptor
what does summative potentials mean?
total potentials
- at a synapse w/ neurotransmitters
what do excitatory postsynaptic potentials do?
- neurotransmitters, (acetylcholine, norepinephrine) — dopamine
- these stimulants slowly elevate the RMP to threshold— becoming less negative (+30mV)
what do inhibitory postsynaptic potentials do?
- neurotransmitters, (acetylcholine, norepinephrine) —- GABA
- these stimulants will decrease the RMP — makes cell more negative — hyperpolarization (-70mV —> -90mV)
types of sensory nerve endings?
nociceptors (most common, none in brain)
- pain receptor
thermoreceptors
- temperature
mechanoreceptors
- touch, vibration, itch, stretch and pressure
photoreceptors
-light waves
chemoreceptors
- chemical changes, taste, smell
types of dendritic nerve endings?
- free nerve endings (most common, pain/temp.)
- meissner’s corpuscle (hairless skin, fine touch - lips, most sensitive)
- golgi tendon organ
- muscle spindle
what do different locations of sensory nerves allow them to do?
different locations allow the body to monitor external and internal stimuli
what are interoceptors?
monitors the internal environment of the body
ex.) chemicals, position, BP, pH, temp.
what are exteroceptors?
monitors the external environment of the body
ex.) touch, taste, smell, sound, sight
what are proprioceptors?
monitor muscles, ligaments, joints
- sends info to the cerebellum
what are the three levels of the organizational pathways?
- receptor level
- circuit level
- perceptual level
what happens at the receptor level?
- a stimulus is received at the right area and is collected by the dendritic receptors
what happens at the circuit level?
located in spinal cord
- pathway travels up spinal cord, leads to thalamus —- here the info is projected onto the cortex
what happens at the perceptual level?
CNS (mostly brain - cerebrum)
- the ability of the cortex to interpret and identify the stimulus
(six steps)
what is serial processing?
where information does not reach the cortex
- autonomic pathways with involuntary responses — reflexes
—- reasoning: protection and homeostasisw
what is parallel processing?
- conscious activity - info reaches cortex through the thalamus
- multiple connections between cortical areas
- all learning follows this pathway
- glutamate releases to form memories or pathways in brain
- acetylcholine helps us recall the info - completes loop
what does acetylcholine do?
excitatory PSNS, somatic nervous system
- helps with recalling memories
(not enough = Alzheimer’s, dementia)
what does norepinephrine do?
excitatory SNS
- brainstem is main source
what does dopamine do?
excitatory- brain stem (not enough = Parkinson’s)
- voluntary actions
- mood
- helps suppress pain pathways
most addictions —brain stops producing it
what does serotonin do?
excitatory - hypothalamus
“happy chemical”
- controls mood
- if low, = depression
what does glutamate do?
memory formation
what do endorphins do?
brain stem
- suppress pain pathways
- heightens with physical activity
ex) runner’s high
what does substance p do?
- increases when person is injured
- stimulates pain pathways —> chronic pain
ex) spinal cord
what are the two methods of post-synaptic removal?
1) enzymatic destruction
2) active transport back into the presynaptic cell membrane
- removal is necessary to propagate another AP — re-uptake inhibitor
what is pain?
- indicates tissue damage or discomfort
- stimulated by release of bradykinin (pain) at the tissues w/ histamine (inflammatory chemical)
what are the two classifications for pain?
- somatic (body) - very precise in location, not with internal organs
ex) on the surface - visceral - diffused and referred to other body part, internal organs
ex) heart referral patterns - chest tightness, left arm/jaw pain, dizziness, sweaty, SOB, nausea
what might affect people’s tolerance to pain?
- prior experience
- genetics (conditions - no pain receptors)
pain: type A fibers
- high priority, heavy myelinated
- sharp acute pain, desensitizes quickly
pain: type C fibers
- lower priority, unmyelinated
- dull achy pain, doesn’t desensitize until healed
what is chronic pain?
- initiated by recurrent injury
- results in build up of substance p and prostaglandins in the spinal cord (circuit level) —> lowering threshold of the nerves making them hypersensitive
- when hypersensitivity starts – it becomes easier to stimulate the the synapses within the spinal cord
what is a plexus? and what are the types?
spinal nerves that come together to form a large collection of nerves
1) cervical
2) brachial
3) lumbar
4) sacral
aspects of the cervical plexus?
C1-C5
serves the skin and muscles of the neck and posterior head
major nerves
- phrenic nerve C2/C3 —> diaphragm (inhalation)
- ansa cervicalis —> flexors of the anterior neck
aspects of the brachial plexus?
C5-T1 - serves the arm
- axillary nerve —> shoulder joint and deltoid (abductor)
- radial nerve —> arm and forearm extensors (triceps)
- median nerve —> lateral forearm and first three digits (can be carpal tunnel syndrome)
- ulnar nerve —> medial forearm and digits four-five (known as funny bone nerve)
aspects of the lumbar plexus?
L1 - L5 - anterior and medial thigh
- femoral nerve —> anterior hip and thigh including knee (satorius, TFF, quads)
- obturator nerve —> thigh adductors (gracilius)
aspects of sacral plexus?
L5 - S4 - posterior thigh and lower leg
- sciatic nerve (largest, longest L4/L5 - big toe) posterior thigh and hamstrings
- tibial nerve —> post lower leg and plantar flexors
- common fibular nerve —> anterior lower leg and dorsiflexors
what is a reflex? what types of reflexes are there? what is the reason for reflexes?
- a set pathway from a sensory nerve to the spinal cord and back to the motor nerve (muscles, glands)
reflex arc: - receptor, sensory neuron, interneuron, motor neuron, effector
somatic reflexes types: - simple (stretch) reflex
- flexor (withdrawal) reflex
- crossed extensor reflex
- superficial reflex
for: protection, homeostasis
how is the thoracic region innervated?
- intercostal nerves T1 - T12
- follow costal groove, innervate the muscles and tissue
- sensory and motor
what happens in the simple (stretch) reflex?
tested by reflex hammer
- allows antagonist muscles to contract without working against eachother
levels: C5, C6, C7, L4, S1
- maintains posture
what happens in the withdrawal reflex?
- reflex functioning with the upper limb, head and foot
- protective function
what happens in the crossed extensor reflex?
-maintains balance during an unexpected stimulus while ambulating
LA - RL RA - LL
ex) stepping on a sharp object, missing a step, grabbing a person’s arm
what happens in the superficial reflex?
stimulated through the skin
what is the babinski’s reflex?
test: stroke the sole of foot
- toes flare and extend = positive sign (indicates a CNS lesion if older than 2 y.o.)
