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Nervous System : Katy Colindres - Period 6 - Coggle Diagram

- - - - integration
        
        processing and interpretation of sensory input
      - motor output
        
        activation of effector organs (muscles and glands) which produces a response
      - sensory input
        
        info gathered by sensory receptors about internal and external changes
- - - - integration and control center: interprets sensory input and dictates motor output
  - - - spinal nerves to and from spinal cord
      - cranial nerves to and from brain
    - - sensory (afferent) division
        
        somatic sensory fibers
        
        convey impulses from skin, skeletal muscles, and joints TO CNS
        
        visceral sensory fibers
        
        convey impulses from visceral organs TO CNS
      - motor (efferent) division
        
        transmits impulses AWAY FROM CNS to effector organs (muscles and glands)
        
        two divisions:
        
        somatic nervous system (voluntary)
        
        conduct impulses FROM CNS TO skeletal muscle, conscious control of skeletal muscles
        
        autonomic nervous system (involuntary)
        
        consists of visceral motor nerve fibers, regulates smooth muscle, cardiac muscle, and glands
        
        two functional subdivisions:
        
        sympathetic and parasympathetic, work in opposition to each other
- - - - Cell Body
        
        synthesizes proteins, membranes, and chemicals
        
        in most, plasma membrane is part of receptive region receiving input info from other neurons
        
        nuclei: clusters of neuron cell bodies in CNS
        
        most neuron cell bodies are located in CNS
        
        ganglia: clusters of neuron cell bodies in PNS
      - Processes
        
        armlike, branching, extend from cell body
        
        CNS contains both neuron cell bodies and their processes
        
        PNS contain chiefly neuron processes
        
        tracts: bundles of neuron processes in CNS
        
        nerves: bundles of neuron processes in PNS
        
        two types of processes:
        
        dendrites
        
        receptive region of neuron
        
        convey incoming messages toward cell body as short distance signals (graded potentials)
        
        in many areas, finer dendrites are highly specialized to collect info
        
        axon
        
        each neuron has ONE axon that starts at axon hillock (cone-shaped area)
        
        in some neurons, axons are short or absent; in others, axon comprises almost entire cell length
        
        nerve fibers: long axons
        
        branch profusely at their end
        
        axon terminals: distal ending of axons
        
        conducting region of brain
        
        generates nerve impulses and transmits them along axolemma (neuron cell membrane) to axon terminal
        
        axon terminal: region that secretes neurotransmitters into the extracellular space
        
        can excite or inhibit neurons it contacts
        
        communicates with different neurons at the same time
        
        quickly decay if cut or damaged
        
        movement occurs in towards and away from the cell body
        
        myelin sheath
        
        composed of myelin, a whitish protein-lipid substance
        
        myelin protects and electrically insulates axon
        
        myelin increases speed of nerve impulse transmission
        
        myelinated fibers: segmented sheath surrounding most long axons
        
        nonmyelinated fibers: do not contain sheath (conduct impulses more slowly)
        
        thin fibers not wrapped in myelin
        
        myelination in the PNS
        
        formed by schwann cells, wraps around axon in jelly roll fashion, one cell forms one segment of myelin sheath
        
        myelin sheath gaps
        
        gaps between adjacent schwann cells
        
        in the CNS
        
        formed by processes of oligodendrocytes, not whole cells
        
        myelin sheath gap is present
        
        white matter: regions of brain and spinal cord with dense collections of myelinated fibers
        
        gray matter: mostly neuron cell bodies and nonmyelinated fibers
    - - transmit electrical signals and conduct impulses
  - - - astrocytes
        
        support + brace neurons
        
        play major role in exchanges between capillaries + neurons
        
        guide migration of young neurons
        
        control chemical environment around neurons
        
        respond to nerve impulses and neurotransmitters
        
        influence neuronal functioning
        
        participate in info processing in brain
      - microglial cells
        
        processes touch and monitor neurons
        
        migrate towards injured neurons and consume microorganisms and neuronal debris
      - ependymal cells
        
        lines central cavities of brain and spinal cord
        
        forms permeable barrier between csf and tissue fluid bathing cns cells
      - oliodendrocytes
        
        processes wrap cns nerve fibers, forming myelin sheaths in thicker nerve fibers
  - - - form myelin sheaths in thicker nerve fibers
      - similar function as oligodendrocytes
      - plays vital role in regeneration of damaged peripheral nerve fibers
- - - - three or more processes (one axon, other dendrites)
        
        most common and major neuron type in CNS
    - - two processes (one axon, one dendrite)
        
        rare
    - - one t-like process (two axons)
        
        found mainly in PNS, common only in places like dorsal root ganglia of spinal cord and sensory ganglia of cranial nerves
  - - - transmit impulses from sensory receptors towards the CNS
        
        almost all unipolar
        
        cell bodies located in ganglia of in PNS
    - - carries impulses from CNS to effectors
        
        multipolar
        
        most cell bodies located in CNS (except some autonomic neurons)
    - - shuttle signals through CNS pathways
        
        lie between motor and sensory neurons
        
        almost all of body's neurons are interneurons
        
        lie between motor and sensory neurons, most are entirely within CNS
- - - - fornix: fiber tract linking limbic system regions
      - large part of emotional or affective brain
        
        puts emotional responses to odors
        
        most output relayed through hypothalamus
        
        allows us to react emotionally to things we consciously understand to be happening
        
        hippocampus and amygdaloid body also play a role in memory
  - - - these connections allow it to govern brain arousal
    - - vasomotor centers
      - cardiac center
      - respitory centers
  - - - controls voluntary and skilled skeletal muscle activity
      - functions in intellectual and emotional processing
      - localizes and interprets sensory inputs
    - - subcortical motor centers
      - help control skeletal muscle movements
    - - relays sensory impulses to cerebral cortex for interpretation
      - relays impulses between cerebral motor cortex and lower motor centers, including cerebellum
      - involved in memory processing
    - - chief integration center of autonomic nervous system
      - regulates body temp, food intake, water balance, thirst, and biological rhythms and drives
      - regulates hormonal output of anterior pituitary gland
      - acts as an endocrine organ, produces posterior pituitary hormones ADH and oxytocin
  - - - contains visual and auditory reflex centers (superior and inferior colliculi)
      - contains subcortical motor centers
      - contains nuclei for cranial nerves three and five
      - contains projection fibers
    - - relays info from the cerebrum to the cerebellum
      - cooperates with the medullary respiratory centers to control respiratory rate and depth
      - contains nuclei of cranial nerves
      - contains projection fibers
    - - relays ascending sensory pathway impulses from skin and proprioceptors through nuclei cuneatus and gracilis
      - contains visceral nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, coughing, etc
      - relays sensory info to the cerebellum through inferior olivary nuclei
      - contains nuclei of cranial nerves eight, ten, and twelve
      - contains projection fibers
    - - see "reticular formation"
  - - - broca's area
        
        involved in speech production
        
        patients with lesions in this area understand words, but cannot speak
      - wernicke's area
        
        involved in understanding spoken and written words
        
        patients with lesions in this area can speak, but words are nonsensible
      - corresponding areas on right side are involved with nonverbal language components
  - - - two stages of declarative memory storage
        
        short-term memory
        
        temporary holding of info
        
        limited to seven or eight pieces of info
        
        long term memory
        
        has unlimited capacity
  - - - cover and protect CNS
      - protect blood vessels and enclose venous sinuses
      - contain cerebrospinal fluid
      - form partitions in skull
    - - dura mater
        
        strongest meninx
      - arachnoid mater
        
        middle layer with spiderweb-like extensions
        
        separated from dura mater by subdural space
        
        subarachnoid space contains CSF and largest blood vessels of brain
      - pia mater
        
        delicate connective tissue that clings tightly to brain, following every convolution
        
        contains many tiny blood vessels that feed brain
    - - inflammation of the meninges
      - may spread to CNS, which would lead to inflammation of the brain, referred to as encephalitis
      - meningitis is usually diagnosed by observing microbes in a sample of CSF obtained through lumbar puncture
  - - - gives buoyancy to CNS structures
        
        reason brain is not crushed under its own weight
        
        protects CNS from blows and other trauma
        
        nourishes brain and carries chemical signals
    - - obstruction blocks CSF circulation or drainage, resulting in increased pressure
      - in newborns, skull bones are unfused, so increased pressure causes head to enlarge
      - in adults, rigidity of the skull keeps pressure within, potentially leading to brain damage
        
        can compress blood vessels and crush soft nervous tissue
      - treatment is to drain CSF with ventricular shunt to abdominal cavity
  - - - chemical variations could lead to uncontrollable neuron firings
    - - simple diffusion
        
        allows lipid-soluble substances, as well as blood gases to pass freely through cell membrane
      - specific transport mechanisms
        
        facilitated diffusion moves substances important to the brain such as glucose, amino acids and specific ion
    - - necessary to monitor chemical composition and temperature of blood
- - - - all gated sodium and potassium channels are closed
      - only leakage channels for sodium and potassium are open
        
        maintains the resting membrane potential
    - - sodium channels open
      - depolarizing local currents open voltage-gated sodium channels, and sodium rushes into cell
      - sodium influx causes more depolarization, which opens more sodium channels
      - at threshold, (-55 to -50 mV), positive feedback causes opening of all sodium channels
        
        results in large action potential spike!
        
        membrane polarity jumps to +30 mV
    - - sodium channels are inactivating, and potassium channels open
        
        sodium channel inactivation gates close
        
        membrane permeability to sodium declines to resting state
        
        action potential spike stops rising
        
        voltage gated potassium channels open
        
        potassium exits cell down its electrochemical gradient
        
        repolarization: membrane returns to resting membrane potential
      - repolarization resets electrical conditions, not ionic conditions
    - - some potassium channels remain open, and sodium channels reset
      - some potassium channels remain open, allowing excessive potassium efflux
        
        inside of membrane then becomes more negative than in resting state
      - hyperpolarization of membrane is when it slightly dips below resting voltage
      - sodium channels also begin to reset
      - after repolarization, sodium potassium pumps restore ionic conditions
  - - - slow conduction that occurs in nonmyelinated axons
    - - occurs only in myelinated axons and is about 30 times faster
        
        APs generated only at gaps
- - - - sensory nerves of smell
    - - purely visual function
    - - raising eyelid, directing eyeball, constricting iris, and controlling lens shape
    - - primarily motor nerve that directs eyeball
    - - convey sensory impulses from various areas of face and supply motor fibers for mastication
    - - primarily a motor, innervating lateral rectus muscle
    - - facial expression, parasympathetic impulses to lacrimal and salivary glands and taste from anterior two-thirds of tongue
    - - mostly sensory function, small motor component for adjustment of sensitivity of receptors, formerly auditory nerve
    - - innervate part of tongue and pharynx for swallowing and provide parasympathetic fibers to parotid salivary glands and conduct taste and general sensory impulses from pharynx and posterior tongue, and impulses from carotid chemoreceptors and baroreceptors
    - - help regulate activities of heart, lungs, and abdominal viscera and carry impulses from thoracic and abdominal viscera, baroreceptors, chemoreceptors, and taste buds of posterior tongue and pharynx
    - - innervate trapezius and sternocleidomastoid muscles
    - - innervate extrinsic and intrinsic muscles of tongue that contribute to swallowing and speech
- - - - contain efferent (motor) fibers from ventral horn motor neurons that innervate skeletal muscles
    - - contain afferent (sensory) fibers from sensory neurons in dorsal root ganglia that conduct impulses from peripheral receptors
- - - - acetylcholine
        
        released at neuromuscular junctions
        
        also used by many ANS neurons and some CNs neurons
        
        synthesized from acetic acid and choline by enzyme choline acetyltransferase
        
        degraded by enzyme acetylcholinesterase
      - biogenic amines
        
        catecholamines
        
        dopamine, norepinephrine (NE), and epinephrine: made from the amino acid tyrosine
        
        indolamines
        
        serotonin: made from the amino acid tryptophan
        
        histamine: made from the amino acid histidine
        
        all widely used in brain: play roles in emotional behaviors and biological clock
        
        used by some ANS motor neurons
        
        especially NE
        
        imbalances are associated with mental illness
      - amino acids that are proven neurotransmitters
        
        peptides (neuropeptides)
        
        strings of amino acids that have diverse functions
        
        endorphins
        
        beta endorphin, dynorphin, and enkephalins: act as natural opiates; reduce pain perception
        
        purines
        
        monomers of nucleic acids that have an effect in both CNS and PNS
        
        gases and lipids
        
        endocannabinoids
        
        act as same receptors as THC (active ingredient in marijuana)
      - neurotransmitters exhibit a great diversity of functions
        
        two classifications
        
        effects
        
        excitatory versus inhibitory
        
        neurotransmitter effects can be excitatory (depolarizing) and/or inhibitory (hyperpolarizing)
        
        effect determined by receptor to which it binds
        
        actions (direct versus indirect)
        
        direct action
        
        neurotransmitter binds directly to and opens ion channels
        
        indirect action
        
        neurotransmitter acts through intracellular second messengers
- - - - promotes maintenance functions, conserves energy
    - - mobilizes body during activity
  - - - sympathetic: fibers originate in the thoracic and lumbar spinal cord
    - - sympathetic: preganglionic fibers are short, postganglionic are long
    - - sympathetic: ganglia are close to spinal cord
- - - - site of stimulus action
    - - transmits afferent impulses to CNS
    - - either monosynaptic or polysynaptic region within CNS
    - - conducts efferent impulses from integration center to effector organ
    - - muscle fiber or gland cell that responds to efferent impulses by contracting secreting
  - - - somatic reflexes
        
        activate skeletal muscles
      - autonomic (visceral) reflexes
        
        activate visceral effectors (smooth or cardiac muscle or glands)
        
        for example, reflexes that empty rectum and bladder
- - - - produces immediate feelings of sedation and well-being
  - - - affects serotonin pathways responsible for mood, sleep, perception and appetite. also, the excess serotonin stimulates milder release of dopamine along reward pathway making ecstasy slightly addictive
  - - - may affect memory, slows down movement, makes us feel relaxed and calm
  - - - makes user feel intense pleasure and exhileration
  - - - affects areas of the brain involved in memory formation, decision making, and impulse control
  - - - concentrates in the reward pathway, also makes users fidgety and unable to stay still
  - - - LSD is responsible for feelings of wakefulness and evoking a startle response to unexpected stimulus
  - - - opioid
        
        come from opium poppy plants. used as painkillers when prescribed. cause pinpoint pupils and a rush of warmth and pleasure followed by drowsiness and clouded thinking. may also cause nausea, itching, vomiting, loss of consciousness, and the user to b=stop breathing. withdrawal symptoms may include body aches, chills, diarrhea, and vomiting
  - - - inhalant
        
        impair coordination, speech, and judgement. these substances are not designed to be used as drugs. they are found in common household products. may cause hallucinations, confusion, seizures, brain damage, or sudden death.
  - - - stimulant/hallucinogen
        
        can cause both an increase in energy and distortions in perception. causes feelings of euphoria and emotional connection others. involuntary jaw clenching, muscle cramping, chills, and sweating. can cause panic attacks and seizures. also interferes with the body's' temperature regulation
  - - - stimulant
        
        active substance in tobacco plants. increases nerve activity and heart rate. for regular users, it can have a calming effect. withdrawal symptoms include intense cravings, difficulty concentrating, irritability, and sleep disturbances. can contribute to cancer, heart disease, stroke, emphysema, and COPD, a chronic lung disease
  - - - hallucinogen
        
        cause hallucinations and other distortions in perception. some are found in nature and others are made in a lab. intensify sensations and emotions. cause users to see, hear, and feel things that aren't actually there. users may experience multiple emotions at once or swing rapidly from one emotion to another/ increased body temperature, heart rate and blood pressure, dilated pupils, loss of apetite, nausea, paranoia, panic, and sleeplessness
  - - - depressant
        
        relaxing effects. can cause hallucinations, nausea, slowed breathing, coma, or death. not approved for medical use in the U.S. colorless, tasteless, and odorless. can be used as a date-rape drug. victims may not be able to fight off their attackers and they may not remember what happened
  - - - hallucinogen
        
        cause hallucinations and distortions in perception. feelings of detachment from body and its surroundings. may lose touch with reality and behave unpredictable or violent. can cause fever, seizures, coma, or death. terrifying feeling, like a near-death experience
- - - - digits turn pale, then cyanotic
      - treated with vasodilators
  - - - turns myelin into hardened lesions called scleroses
      - impulse conduction slows and eventually ceases
      - demyelinated axons increase sodium channels, causing cycles of relapse and remission
  - - - due to brain damage, possible from lack of oxygen during birth
      - spasticity, speech difficulties, motor impairments can be seen
      - some patients have seizures, are intellectually impaired, and/or are deaf
      - visual impairment is common
  - - - child is vegetative; death occurs soon after birth
  - - - laminae and spinous processes are missing on at least one vertebra
      - spina bifida occulata: least serious, involves only one or few missing vertebrae and usually causes no neural problems
      - child with spina bifida may also have hydrocephalus, paralysis, and bowel and bladder dysfunction
      - most cases cause by lack of folic acid
  - - - genetic factors play a role, but brain injuries, stroke, infections, or tumors can also be causes
  - - - may spread to CNS, which would lead to inflammation of the brain, referred to as encephalitis
      - usually diagnosed by observing microbes in a sample of CSF obtained via lumbar puncture
  - - - key proteins appear to be misfolded and malfunction
  - - - leads to degeneration of basal nuclei and cerebral cortex
    - - usually fatal within 15 years of onset
  - - - can compress blood vessels and crush soft nervous tissue