ch. 11 Flashcards
characteristics of the nervous system
- receives info from many sources at the same time
- integrates information (processes, compiles and makes sense of the info)
- extremely fast-can receive, integrate and respond in tenths of a second
- can initiate specific responses such as muscle contraction, glandular secretion, conscious control over movement
in order to maintain homeostasis the nervous system works with the
endocrine system
what does the nervous system enable
self awareness and emotions
what are the two principle parts of the nervous system
-central nervous system
-peripheral nervous system
components and functions of the CNS
components: brain, spinal cord and retina (in the eye)
functions: receives, processes and transfers info
peripheral nervous system components and divisions
components: nerves outside of the CNS
*sensory division: carries info TOWARD the CNS (afferent)
*motor division: carries info AWAY from CNS (efferent)
- somatic division: controls skeletal muscles
-autonomic division: controls smooth muscles, cardiac muscles and glands…sympathetic and parasympathetic
what do neurons do
-specialized for communication
-generate and conduct electrical impulses
what are the 3 types of neuron
*sensory neurons: neurons found in the PNS that receive stimuli neurons and transmit info to the CNS
* interneurons: neurons that transmit info between components of the CNS
* motor neurons: neurons found in the PNS that transmit info away from the CNS
3 parts of the neuron
*cell body: main part of the cell, has the nucleus and most of the cytoplasm and organelles
*dendrites: small, slender extensions of the cell body, which receive incoming info
*axons: long, slender extension, specialized to conduct electrical impulses away from the cell body
look at slide 6 of ch11
action potentials…whatis it and what initiates it
-primary means of communication throughout the nervous system
- electrical impulse
- neurons generate and transmit action potentials (initiates it)
what maintains resting potential
sodium-potassium pump
what is resting potential
-measurable difference in voltage across the cell membrane in a resting cell
* -70mV
* interior of cell is negative relative to the exterior
role of the Na+/K+ pump
-maintains cell volume
- establishes and maintains resting potential by ongoing active transport of 3 NA+ out of the cell and 2 K+ into the cell
-the pumping counteracts the effects of Na+ diffusing into the cell and K+ leaking out via leak channels
for the Na+/k+ pump
3 Na+ (positives) out per 2 positives (K+) in = net negative inside
what does graded potential do
-alter resting potential
- transient local changes in the resting potential
-may depolarize or hyperpolarize the membrane
summation
-graded potentials can add up in space or time
-this additive effects may reach a “trigger point” or “threshold” which initiates an action potential
inputs of other neurons can be
excitatory(depolarizing-increases their probability to fire)
inhibitory (hyperpolarizing-less likely to fire)
to trigger an action potential
graded potentials must reach a threshold (triggering point)
what is action potential
sudden reversal of the voltage difference across the cell membrane
- 3 phases of action potential: depolarization, repolarization, reestablishment of the resting potential
-sweeps down axon toward axon terminals
depolarization
voltage sensitive Na+ channels open, Na+ moves into the axon (this reverses the voltage across the membrane… interior is now +)
repolarization
Na+ channels close
K+ channels open
K+ moves out of the axon-restores initial polarity, becomes temporarily hyperpolarized
reestablishment of the resting potential
K+ channels close
-the normal activity of the Na+/K+ pump restores resting potential
refractory period-2 types
-absolute refractory period
-relative refractory period
absolute refractory period
*period when another action potential cannot be generated
- ensures that action potentials only travel in one direction
relative refractory period
*follows absolute refractory period
*membrane is slightly hyperpolarized
- more difficult than usual to generate the next action potential
what are characteristics of action potentials
all-or-none
self-propagating
all-or-none
*individual neuron threshold sets extent of stimulus needed
*action potential triggered if threshold is achieved
*action potential is always the same in speed and voltage once triggered
self-propagating
*continues to propagate itself in the next region of the axon
*moves like a wave down the axon, with constant speed and amplitude
what encodes the strength of the stimulus
the number of action potentials/unit time (frequency)
-stronger stimuli generate more action potentials/unit time
when does the action potential travel faster
-in myelinated axons
- in larger diameter axons
the speed of action potential
-always the same for a particular neuron
-can be different in different neurons
neuroglial cells make up….% of nervous system cells
80%
function of neuroglial cells
-support
- protection
- do NOT transmit action potentals
what are the two types of myelinating glia
-oligodendrocytes in CNS
- schwann cells in PNS
what do schwann cells do
form myelin sheaths in PNS
role of myelin sheath
-save neuron energy
- speed up the transmission of impulses nearly 50X (saltatory conduction, nodes of ranvier)
- help damaged or severed axons regenerate
saltatory conduction
leaping pattern of action potential conductions from node to node
nodes of ranvier
short uninsulated gaps between schwann cells
disorders associated with degeneration of myelin sheaths
-multiple sclerosis (MS)
- amyotrophic lateral sclerosis (ALS)
multiple sclerosis and symptoms
-progressive autoimmune damage to myelin sheaths in brain and spinal cords
- ex. numbness, weakness, visual impairment, paralysis, incontinence
amyotrophic lateral sclerosis
*lou gehrig’s disease
* progressive damage to myelin shealths in spinal cord regions involved in motor control of skeletal muscles
* progressive weakening and wasting of skeletal muscle
ALS reason for death
usually due to respiratory failure due to effects of impulse transmission to diaphragm and intercostal muscles
what are the parts/processthat transfer info from a neuron to its target
synapse
synaptic transmission
define synapse
special junctions between axon terminus of a neuron and its target cell (another neuron, muscles cell or gland)
synaptic transmission
*process of transmission of impulse from sending (presynaptic neuron) across synaptic cleft to receiving (postsynaptic neuron) target
- involves release and diffusion of chemical neurotransmitters
events that occur during synaptic transmission
- action potential arrives at axon terminus of presynaptic neuron, Ca2+ diffuses into axon bulb
- Ca2+ causes release of neurotransmitter from vesicles; neurotransmitter diffuses across synaptic cleft
- neurotransmitter binds to receptors on target (postsynaptic) membrane and opens gated channels
- graded potential results from Na+ diffusion through opened channels
what types of effects do neurotransmitters exert and how long are the effects
excitatory
inhibitory
effects of neurotransmitter are short-lived
what does the response of the postsynaptic target cell depend on
- types of neurotransmitter (>50 types)
- concentration of neurotransmitter
- type of receptors
- type of gated ion channels in postsynaptic membrane
excitatory neurotransmitters
depolarize the postsynaptic cell, approaching or exceeding threshold
inhibitory neurotransmitter
hyperpolarize the postsynaptic cell
what are the 3 ways neurotransmitters are promptly removed from synaptic cleft
- neurotransmitter may be taken up by presynaptic neuron and repackaged for future use
- enzymes in the synaptic cleft may destroy the neurotransmitter
- neurotransmitter may diffuse away
acetylcholine- neurotransmitter
where is it released
principle actions
-neuromuscular junctions, autonomic nervous system, brain
- excitatory on skeletal muscles; excitatory or inhibitory at other sites, depending on receptors
norepinephrine- neurotransmitter
where is it released
principle actions
*areas of brain and spinal cord, autonomic nervous system
* excitatory or inhibitory, depending on receptors, plays a role in emotion
serotonin- neurotransmitter
where is it released
principle actions
- areas of brain, spinal cord
- usually inhibitory, involved in moods, sleep cycle, appetite
dopamine- neurotransmitter
where is it released
principle actions
- areas of brain, parts of peripheral nervous system
- excitatory or inhibitory, depending on receptors; plays a role in emotions
glutamate- neurotransmitter
where is it released
principle actions
-areas of brain, spinal cord
- usually excitatory, major excitatory neurotransmitter in brain
endorphins- neurotransmitter
where is it released
principle actions
- many areas in brain, spinal cord
- natural opiates that inhibit pain; usually inhibitory
gamma-aminobutyric acid (GABA) - neurotransmitter
where is it released
principle actions
-areas of brain, spinal cord
- usually inhibitory, principal inhibitory neurotransmitter in brain
somatostatin- neurotransmitter
where is it released
principle actions
-areas of brain, pancreas
- usually inhibitory, inhibits pituitary release of growth hormone
what does the response in postsynaptic cell depend on
-how many neurons are forming synapses with it
- whether the neurons forming synapses with it are excitatory or inhibitory
convergance
occurs when one neuron recieves input from many others
divergance
occurs when one neuron sends action potentials to muliple other neurons
what does the PNS relay info between
tissues and cns
nerves… made of and carry to
-axons of many neurons wrapped together in a protective sheath
- carries info to and from the CNS
how many cranial nerves. connect where
12 pairs
-connect directly to brain
- connect to muscles, glands, receptors in head, neck and thoracic and abdominal cavities
how many spinal nerves-pairs..connects to what and where are they relative to bone,hwat does it carry
31 pairs
- connect to spinal cord via dorsal root (sensory) and ventral root (motor)
- each spinal nerve carries both sensory and motor info
-spinal nerves are outside of bone
look at cranial nerve flashcard deck
what do sensory neurons do
-provide info for both somatic and autonomic motor divisions of the PNS
- provide info to the CNS
what does incoming (afferent) info arrive at the CNS as andwhere did it come from
action potentials from sensory neurons
function of the somatic division
*voluntary- conscious control of skeletal muscles
*involuntary-reflexes
spinal reflexes-define and examples (part of somatic division)
*involuntary response mediated primarily by spinal cord and spinal nerves, with little brain involvement
1. flexor (withdrawal) reflex
2. crossed extensor reflex
3. stretch reflex, important in maintaining upright posture, movement
autonomic division
-part of the motor output of the PNS
- controls autonomic body functions of many internal organs
-function without our conscious awareness
*2 division
- sympathetic division-neurological arousal
- parasympathetic division- neurological calming
targets of the autonomic division
smooth muscle, cardiac muscle, internal organs
what are the two neurons required to transmit info from CNS to target cell-autonomic
- preganglionic neurons
- postganglionic neurons
expand on preganglionic neurons
-cell bodies lie within CNS
- axons go to ganglia outside of cns
*ganglia: clusters of cell bodies of postganglionic neurons
expand on postganglionic neurons
-cell bodies in ganglia
- axons go to distant internal glands and organs
what does the autonomic division innervate
smooth muscles, cardiac muscle, glands, internal glands
role of sympathetic division, name of neurotransmitter
- arouses body and prepares body for emergencies
- neurotransmitter: eprinephrine
-produces fight or flight response - unified response in all organs ar=t once
- opposes parasympathetic division
signs that are part of the fight or flight response
*increased heart rate and respiration
* raises blood pressure
* dilates pupils
* slows digestion and urine production
role of parasympathetic division, name of neurotransmitter
-relaxes the body
- opposes sympathetic division
-lowers heart rate and respiration, increases digestion, permits defecation and urination
-acetylcholine
to maintain homeostasis…what works together
sympathetic and parasympathetic divisions work antagonistically
for somatic division how many neurons are required to reach the target cell
one
neurotransmitter of somatic division
acetylcholine
what is the CNS made of
brain and spinal cord
what are the components of the protection of the CNS
bone, meninges, cerebrospinal fluid, blood-brain barrier
Bone-cns protection
skull and vertebrae
meninges- cns protection
protective membranes
-dura mater, arachnoid and pia mater
cerebrospinal fluid-cns protection
-bathes the brain, spinal cord
- shock absorber
- produced within the ventricles of the brain
blood-brain barrier- cns protection
prevents entry of certain chemicals and pathogens
what is the role of the spinal cord and the portions of it
-superhighway for action potentials between the brain and the rest of the body
-white matter and grey matter
white matter-spinal cord
-outer portion of the spinal cord
- consists of myelinated ascending (sensory) and descending (motor) axons (nerve tracts)
grey matter- spinal cord
-centre portion of the spinal cord
- contains cell bodies, dendrites
purpose of the brain
command center of the body
3 major anatomical, functional, evolutionary divisions
*hindbrain: coordinates basic, automatic and vital tasks
*midbrain: coordinates muscle groups and responses to sight and sound
* forebrain: receives, integrates sensory input, determines complex behaviour
hindbrain
*movement and automatic functions
*oldest, most primitive part of brain, from an evolutionary perspective
*3 basics parts
1. medulla oblongata-continuous with spinal cord
2. cerebellum
3. pons
hindbrain-medulla oblongata
*connects to spinal cord
*controls vital automatic functions of internal organs
* motor nerves cross over in medulla oblongata (right forebrain controls left side of body and vice versa)
what are the vital automatic functions-medulla oblongata
two centers
*cardiovascular center: regulates heart rate and BP
*respiratory center: adjucts respiration in response to CO2 and O2 levels
cerebellum-hindbrain
*coordinates basic body movements
* stores and replicates sequences of skilled movements ex. using a keyboard
* excessive alcohol consumption disrupts normal cerebellar function
pons- hindbrain
*connects higher brain centers and the spinal cord
*coordinates the flow of information between the cerebellum and higher brain centers
* aids medulla oblongata in regulating respiration
what is the purpose for the midbrain
vision, hearing and sleep/wakefulness
what does the midbrain do
- “sensorimotor” structure- coordinates movements of the head related to vision and hearing
- controls movement of eyes and size of pupils
- includes groups of neurons involved in sleep/wakefulness cycles
- one group of neurons: steady stream of action potentials to cerebrum, keeps us awake and alert
- one group of neurons: “sleep center” releases serotonin and induces sleep
electroencephalogram (EEG) purpose
measures brain electrical activity
whats the practical use of EEGs
-used to study brain activity during sleep
findings of the EEG
*brain activity increases during sleep
* deepest sleep: muscles relax, heart rate and respiration slow, body temperature drops
*rapid eye movement (REM) sleep: happens just before we awaken
- dreaming occurs during REM sleep
- heart rate and respiration increase
- skeletal muscles are limp
*typically 3-5 deep sleep/REM cycles/night
what is the purpose of the forebrain
emotions and concsious thought
receives and integrates information concerning emotions and conscious thought
parts of the forebrain
hypothalamus
thalamus
limbic system
cerebrum (cerebral cortex)
hypothalamus-where, purpose
*base of forebrain
* regulation of homeostasis
* coordinates some pituitary glands functions-e. temp control, breast milk production, water/solute balance)
*monitors sensory signals -sight, smell, body temp, taste, noise
*hunger centre
thalamus purpose
*receiving, processing, transfer centre
* receives sensory information and directs it to the cerebrum for interpretation
what is a gateway to and from the limbic system
hypothalamus
limbic system
*includes all neuronal structures that together control emotional behaviour and motivational drives
*emotions-fear, anger, aggression, sorrow, love etc
*basic behaviours-seeking food, satisfying thirst, sexual gratification
* behaviours are modified by cerebrum
* hippocampus-important in storage/retrieval of long-term memory…damage starts here in alhziemers disease
structure of the cerebrum (cerebral cortex)
*right and left hemispheres connected by corpus callosum
*outer layer of cerebrum
*highly folded
* grey matter (neurons with unmyelinated axons)
corpus callosum
nerve tracts in corpus callosum allow 2 hemispheres to share information
function of the cerebral cortex
*receives, integrates and interprets sensory info from every organ and region of the body
*memory storage, abstract thought, conscious awareness, conscious control of skeletal muscle
* divided in 4 lobes
4 lobes of the cerebral cortex
frontal lobe
parietal lobe
occipital lobe
temporal lobe
function of the frontal lobe
initiates motor activity, responsible for speech, conscious thought
function of parietal lobe
receives and interprets sensory info from the skin
function of occipital lobe
processes visual info
function of temporal lobe
interprets auditory info, comprehends spoken/written language
what are the two primary areas in the cerebral cortex
*primary somatosensory area: region of parietal lobe that receives sensory input from the skin
*primary motor area: corresponding region of the frontal lobe that initiates motor activity
short term memory
*working memory
* info from previous few hours
*stored in limbic system
long term memory
*info from previous days to years
* involves hippocampus and cerebral cortex
* permanent changes in neurons and development of additional synapses in the cerebral cortex
what are psychoactive drugs and what can they do
*affect states of consciousness, emotions or behaviour
-able to cross blood-brain barrier
- influence concentrations or actions of neurotransmitters, which change the normal patterns of electrical activity in the brain
- affect higher brain functions
examples of psychoactive drugs
cocaine-blocks reuptake of dopamine into presynaptic neuron. prolongs sensations of pleasure
opioids- bind to endorphin receptors in the CNS and PNS, blocking pain and causing euphoria, ex. heroin, morphine
psychological dependence
user craves the feeling associated with the drug
tolerance
requires more of the substance to achieve the same effect
addiction
*user needs to continue obtaining and using a substance
*no free choice involved
withdrawal
physical symptoms occur upon stopping the drug
disorders of the nervous system
trauma-physical injury to brain or spinal cord (ex. concussion, spinal cord injury)
infections caused by bacteria or viruses (encephalitis, meningitis, rabies)
brain tumors
disorders of neural and synaptic transmission (epilepsy, alzheimer’s disease, parkinson’s disease)
concussion, what is it, symptoms, risk
*blow to the head, possibly leading to unconsciousness
*disruption of electrical activity in the brain
symptoms
- headaches, memory and concentration problems, problems with balance, coordination
*risk of subdural hematoma-bleeding into meninges
what could happen if you have a subdural hematoma
-may develop slowly
- may cause pressure on the brain
- drowsiness, headache, weakness on one side of body
- occasionally surgeon must drill through skull to alleviate pressure
spinal cord injuries…what and types
*impair sensation and function below site of injury
*paraplegia-below the neck, paralysis or weakness of legs and part of trunk
*quadriplegia-injury to the neck, paralysis or weakness of legs, arms and trunk
the higher the spinal cord injury, it is more likely to be fatal
encephalitis-what is it, how is it caused, symptoms, treatment
*inflammation of the brain
*caused by viruses that cross the blood-brain barrier
-herpes simplex virus(transmitted to newborn at birth if the mother has genital herpes)
- west nile virus (transmitted by mosquitoes)
*symptoms: headache, fever, fatigue, hallucination, confusion, distrubances in speech, memory, behaviour, seizures
treatment: antiviral drugs
meningitis-what is it, whats it caused by, symptoms, types
*inflammation of the meninges
* may be caused by bacteria or viruses
*symptoms: headache, fever, nausea, vomiting, sensitivity to light, stiff neck
- viral meningitis: milder
- bacterial meningitis: life threatening (treat with antibiotics)
rabies: what is it, infects what, how does it happen, symptoms
-infectious viral disease
- infects mammals
-typically from a bite or lick over broken skin
-travels through peripheral neurons to CNS and brain
- swollen lymph nodes, painful swallowing, vomiting, choking spasms of throat and chest muscles…death follows within 2-10 days
rabies control
-vaccination of pets and wildlife
- post exposure prophylaxis (vaccine and anti-rabies IgG) as soon as possible after exposure
brain tumours..what is it, types, size/location, originates from, treatments
-abnormal growth
-noncancerous (benign) tumors can exert pressure against neighbouring tissue, distrupting function
-symptoms vary depending on location and size
-originates in the brain, other can originate elsewhere in the body-metastatic
-treatments: surgery, chemo, radiation
what is epilepsy, causes, triggers, when
-recurring episodes of abnormal electrical activity
- causes: transient recurring bouts of abnormal brain activity, seizures vary widely depending on part of the brain affected
-triggers: fatigue, stress, flashlights
- childhood or adolesence
what is alzheimer’s disease, what does it affect
build up of abnormal proteins (tau and beta amyloid)
-most common cause of dementia (loss of memory and intellectual abilities)
-affects hippocampus then cerebral cortex
when is the diagnosis confirmed for alzheimers
confirmed post mortem. diagnosis based on symptoms.
