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afferent division

(away from the periphery) carries information to the CNS about external environment and provides status reports on internal activities being regulated by the nervous system


efferent division

(entering the periphery) instructions from the CNS are transferred to the effector organs (muscles or glands).
Autonomic Nervous System - fibres that innervated the smooth muscle, cardiac muscle and glands.
Somatic nervous system - fibres of the motor neurons that supply the skeletal muscles.
Sympathetic and Parasympathetic Nervous Systems - innervated most of the organs supplied by the autonomous system.


afferent neuron

1) peripheral ending = sensory receptor
2) cell body = devoid of dendrites and presynaptic inputs, located adjacent to the spinal cord.
3) peripheral axon = afferent fibre, extends from sensor to cell body
4) central axon = from cell body to spinal cord (short). Diverge and synapse with other neurons in the spinal cord.
Lie primarily in the PNS, with small central axons extending into CNS.


efferent neuron

1) cell body = originates in the CNS
2) efferent axon = efferent fibres, leave the CNS to course their way to the muscle or gland they innervate.
Lie primarily in the PNS, with the cell body in the CNS.



lie entirely in the CNS. Contain 99% of neurons, with the CNS containing more than 100 billion.
1) Lie between afferent and efferent neurons (as connectors) and are important in integrating peripheral responses to peripheral info.
2) Interconnections are responsible for abstract - thoughts, emotions, memory, etc.


glial cells / neuroglia

do no conduct or initiate nerve impulses. Communicate with neurons and send chemical signals to maintain homeostasis. Serve as the connective tissue of the CNS, maintaining composition of ECF and actively modulate synaptic function.
1) astrocytes
2) oligodendrocytes
3) microglia
4) ependymal cells
Do not lose ability to undergo cell division - brain tumors of glial cells are GLIOMAS.



1) glue - hold neurons together in proper spatial relationships
2) serve as scaffold during fetal dev
3) induce small brain blood vessels to establish blood-brain barrier
4) repair of brain injuries and neural scar formation
5) take up and degrade glutamate and GABA neurotransmitters to halt them.
6) Take up excess K+ from ECF when pump is overwhelmed - if they didn't, ECF K+ conc would decrease threshold potential of cells and cause hyperexcitability.
7) enhance synapse formation and strengthen synaptic tx via chemical signalling with neurons



immune cells of the CNS - play a role in the defense of brain as phagocytic scavengers. Derived from bone marrow tissue. Release low levels of nerve growth factor - wispy cells with many long branches.


ependymal cells

1) line internal cavities of brain and spinal cord
2) contribute to formation of CSF
3) serve as neural stem cells with the potential to form new neurons and glial cells.



four interconnected chambers within the interior of the brain, continuous with the narrow, hollow central canal that tunnels though the middle of the spinal cord. Lined by ependymal cells, the beating of their cilia contributes to flow of CSF throughout ventricles.


CNS Injury prevention

1) enclosure in hard bondy structures - cranium and vertebral column
2) three protective and nourishing membranes - meninges
3) brain floats in special cushioning fluid - CSF
4) highly selective blood-brain barrier limits access of blood-borne materials to brain tissue.



1) Dura Mater (tough mother) - two layers, some regions are separated to blood-filled DURAL sinuses, or VENOUS sinuses.
2) Arachnoid Mater - vascularized cobweb-like. Subarachnoid space is filled with CSF. Protrusions of arachnoid villi in the dural sinuses - CSF is reabsorbed along the surface.
3) Pia Mater - most fragile. Highly vascular and closely adheres to brain and spinal cord. Brings blood supply to ependymal cells lining ventricles.


Cerebrospinal Fluid (CSF)

surrounds and cushions the brain and spinal cord. Shock-absorbing protective fluid. Also helps in exchange between neural cells and brain interstitial fluid. Formed by choroid plexuses - richly vascularized cauliflower-like masses of pia mater tissue. Lower in K+ and higher in Na+ than plasma - specialized for conduction of nerve impulses.


Blood-Brain Barrier

1)anatomical - capillary walls are single layer of cells joined by TIGHT junctions
2) physiological - substances exchanged between blood and brain interstitial fluid (glucose, amino acids and ions) are transported by highly-selective membrane carriers.
Prevents potentially harmful blood-borne substances, hormones that may act as neurotransmitters, limits use of drugs for treatment of brain/SC disorders. Astrocytes surround brain capillaries - tell them to 'get tight' and participate in cross-cellular transport of substances like K+
HYPOTHALAMUS is not behind BBB



Brain cannot produce ATP in absence of O2 (anaerobic) - relies on neuroglobin (O2-binding protein) to bring O2 to tissues. Cannot store glucose, but is only fuel source. Brain damage after... O2 = 5 mins, glucose = 15 mins



the act of process of knowing, including both awareness and judgement.


Brain Stem

Midbrain, pons, medulla -oldest region of brain, continuous with spinal cord.
1) origin of majority of peripheral cranial nerves
2) cardio, resp and digestive control centres (vegetative functions)
3) regulation of muscle reflexes for equilibrium and posture
4) part of ‘reticular formation’ - reception and integration of all synaptic input from spinal cord - activation and arousal of cerebral cortex
5) role in sleep-wake cycle.



More individual neurons than in rest of brain.
1) Vestibulocerebellum - maintenance of balance – proprioception & controls eye movements.
2) Spinocerebellum - enhancement of muscle tone and coordination of skilled voluntary muscle activity – monitors and adjusts ‘motor plan’ from cortical motor areas.
3) Cerebrocerebellum - planning of skilled voluntary muscle activity (dance routine)



1) regulation of many homeostatic functions - temp, thirst, urine output, food intake, uterine contraction, milk ejection.
2) important link btwn nervous and endocrine
3) extensive involvement with emotion and basic behavioural patterns



1)relay station for all synaptic input
2) crude awareness of sensation (can't distinguish location or intensity)
3) some degree of consciousness
4) role in motor control
Screens out insignificant signals and routes important impulses to areas of somatosensory cortex. Directs attention to stimuli of interest (background noise vs. baby crying).


Basal Nuclei / Basal Ganglia

1) inhibition of muscle tone
2) coordination of slow, sustained movements
3) suppression of useless patterns of movement
Do not directly influence efferent motor neurons, but modify activity in motor pathway.


Cerebral Cortex

1) sensory perception
2) voluntary control of movement
3) language
4) personality traits
5) sophisticated mental events - thinking, memory, decision-making, creativity, and self-conciousness
Organized into six well-defined layers and functional vertical columns and four LOBES (parietal, occipital, frontal and temporal)
Diencephalon (hypothalamus and thalamus) and the Cerebrum (Basal Nuclei and the Cerebral Cortex)



1) highly convoluted = more developed species. 80% of the total brain weight.
2) Divided into the right and left cerebral hemispheres which are connected by the corpus callosum - a thick band consisting of about 300 million neural axons through which the left & right hemispheres communicate.
3) Grey Matter is made of neural cell bodies & dendrites + glial cells.
4) White Matter is tracts of myelinated nerve fibres (axons).


Parietal Lobe - Cerebral Cortex

Located on the top of the head, to the rear of the central sulcus (deep infolding). Contains the somatosensory cortex - the site for initial cortical processing and perception of somesthetic input as well as proprioceptive input. Locates the source of sensory input (routed from the thalamus) and perceives the level of intensity.


Frontal Lobe - Cerebral Cortex

Activated by the readiness potential (widespread neuronal discharge about 750 msec before any activity in motor area)
1) Contains the primary motor cortex beside the central sulcus. Primarily confers voluntary control over muscles on the the opposite side of the body. Signals from the PMC terminate on the efferent neurons that trigger muscle contraction.
2) Supplementary Motor Area plays a preparatory role in programming movement sequences.
3) Premotor Cortex orients the body and arms to a specific target, guided by posterior parietal cortex.
Together, the 4 motor regions develop a 'motor program' for different movement patterns.


use-dependent competition

somatotopic mapping is not set in stone - but is subject to constant subtle modifications based on use. General pattern is genetic/developmental, but individual cortical architecture can be influenced. i.e. modified by experience



an ability to change or be functionally remodeled in response to the demands placed on it.



example of early cortical plasticity coupled with later permanence - found in left hemisphere. Involves expression (speaking ability) and comprehension.
1) Broca's area - governs speaking ability, located in left frontal lobe.
2) Wernicke's area - left cortex at junction of occipital/parietal/temporal lobes, concerned with comprehension. Formulates coherent patterns of speech.
Language disorders caused by damage to specific cortical areas are called 'aphasias'.



language disorder - difficulty in learning to read because of inappropriate interpretation of words. Dev abnormalities in connections between visual and language areas - can't break down written words into underlying phonetic components.


Prefrontal Association Cortex

front portion of the frontal lobe just anterior to premotor cortex.
1) plans for voluntary activity
2) decision making (weighing consequences)
3) creativity
4) personality traits
5) site of operation of 'working memory'
Stimulation of the area doesn't show any observable effect, but deficits change personality and social behavior (lobotomy!)


Parietal-Temporal-Occipital Association Cortex

lies at the interface of these three lobes.
1) pools and integrates somatic, auditory and visual sensations for complex perceptual processing.
2) enables one to 'get the complete picture' of the relationship of various parts of your body with the external world
3) lets you place what you are seeing in proper perspective


Limbic Association Cortex

motivation, emotion and extensively involved with memory.


Hemisphere Differences

Left - logical, analytic, sequential and verbal tasks. Processes in fine-detail, fragmentary way.
Right - nonlanguage skills, spatial perception and artistic and musical talents. Processes in big-picture, holistic way.


Electroencephalogram (EEG)

graphic record of brain waves that represent the momentary collextive postsynaptic potential activity (EPSPs and IPSPs) rather than action potentials.
1) clinical tool
2) legal determination of brain death
3) distinguish various stages of sleep


Parkinson's Disease (PD)

deficiency of dopamine in basal nuclei
1) increased muscle tone or rigidity
2) involuntary, useless or unwanted movements
3) slowness in initiating or carrying out different motor behaviors. Difficult to stop ongoing activities.


Limbic System

ring of forebrain structures that surround the brain stem and are connected by intricate neural pathways. Associated with emotion, basic survival and sociosexual behaviours. motivation and learning.



on the interior underside of the temporal lobe - part of the limbic system - processes inputs that give rise to the sensation of fear.


reward/punishment centres

stimulation in these respective areas give rise to pleasant or unpleasant sensations. Reward centres found most in regions involving eating, drinking and sexual activity.



encompasses subjective feelings and moods (anger, fear, happiness, etc) as well as the overt physical responses (laughing, crying, blushing, etc)



the ability to direct behaviour toward specific goals. Homeostatic drives represent subjective urges associated with specific body needs (thirst, hunger, etc).


Psychoactive Drugs

affect moods in humans - neurotransmitters include norepinepherine, dopamine, serotonin.



acquisition of knowledge or skills as a consequence of experience, instruction, or both.


Memory Trace

neural change responsible for retention or storage of knowledge.
1) short-term memory (seconds to hours) involves transient strengthening of pre-existing synapses
2) long-term memory (days to years) involves the activation of specific genes that control synthesis of proteins needed for structural/functional changes of specific synapses.
Transition from 1->2 is called CONSOLIDATION.



lack of memory that involves whole portions of time rather than isolated bits of info.
1) retrograde - going backward, inability to recall recent past events
2) anterograde - going forward, inability to store memory long term for later retrieval.



elongated, medial portion of the temporal lobe, part of the limbic system. Vital role in short-term memory and consolidation into long-term memory. Play special role in 'declarative memories' - the 'what' memories of specific dates, people, places, etc. Extensive damage to this area is seen in Alzheimer's patients.



decreased responsiveness to repetitive presentations of an indifferent stimulus. Closing of Ca2+ channels reduces Ca2+ entry into the presynaptic terminal, which leads to a decrease in neurotransmitter release. Habituation is stored in the form of modification of specific Ca2+ channels.



increased responsiveness to mild stimuli following a strong or noxious stimulus. Ca2+ entry into the presynaptic terminal is enhanced by PRESYNAPTIC FACILITATION, causing a subsequent increase in neurotransmitter release. Facilitating interneuron synapses on the presynaptic neuron, releases serotonin - triggers cAMP which blocks K+ channels, allowing more Ca2+ to pass through.


long-term potentiation (LTP)

refers to prolonged increase in the strength of the existing synaptic connections in activated pathways following brief periods of repetitive stimulus. Lasts for days, weeks - long enough for consolidation to occur. Could result from increased responsiveness to neurotrans in postsynaptic nerve (via NDMA and AMPA receptors), or increased release of neuro from presynaptic nerve.


Retrograde factor

A substance emitted from a postsynaptic neuron that influences the presynaptic neuron, which ultimately enhances the secretion of neurotransmitter from the presynaptic neuron. Nitric Oxide!



1) CREB – molecular switch that turns on the genes important in long-term memory storage
2) CREB2 – repressor of CREB-facilitated protein synthesis.
Formation of enduring memories involves activation of CREB and deactivation of CREB2. Involves ‘immediate early genes’ (IEGs) – synthesize proteins to encode long-term memory



Subjective awareness of the external world and self, including awareness of the private inner world of one’s own mind.
1) maximum alertness
2) wakefulness
3) sleep
4) coma



reduced reaction to external stimuli, reduced voluntary movement, increased rate of anabolism and decreased rate of catabolism. Brain’s activity is not reduced, during certain stages O2 uptake is increased.
1) slow-wave sleep
2) paradoxical or REM sleep


Function of Sleep

Adenosine is generated by awake state – acts as a neuromodulator and inhibits arousal system. Brings on slow-wave sleep. Adenosine levels diminish during sleep. Also might give time for brain to get rid of toxic free radicals, or accomplish long-term structural/chemical adjustments for learning & memory storage.


Slow-Wave Sleep

stages 1-4, 30-45mins, then backwards in same time
EEG – displays slow waves
Motor – considerable muscle tone, frequent shifting
HR/resp/BP – minor reductions
Dreaming – rare
Arousal – easily awakened


Paradoxical/REM sleep

10-15 mins, 20% of time – rapid eye movements
EEG – displays awake person stuff
Motor – inhibition of muscle tone, no movement
HR/resp/BP - irregular
Dreaming – common
Arousal – not easily awakened


Sleep Wake Cycle

1) arousal system – part of reticular activating system
2) slow-wave sleep centre – hypothalamus, containing sleep-on neurons
3) paradoxical sleep centre – brain stem, containing REM sleep-on neurons
arousal system more readily overrides the sleep systems


Spinal Cord

1) Inner Grey matter (neuronal cell bodies and dendrites, glial cells) – dorsal, ventral and lateral horns.
2) surrounded by White matter (tracts of nerve fibres with specific functions).
Two purposes:
1) serve as a link for tx of info between brain and body
2) integrate reflex activity from afferent -> efferent without involving brain (spinal reflex)


Spinal Nerves

Paired, emerging from spinal cord through spaces formed between the bony, wing-like arches (lamina & pedicle) of adjacent vertebrae. Contains both afferent and efferent fibres.
8 cervical
12 thoracic (chest)
5 lumbar
5 sacral
1 coccygeal
forming the ‘cauda equina’ (horse’s tail) after the cord stops close to the lumbar.
Afferent fibres enter spinal cord through DORSAL ROOT – their cell bodies are clustered together in a dorsal root GANGLION.
Efferent neuron cell bodies are inside the grey matter, exit through VENTRAL ROOT.


Spinal Cord White Matter

Ascending Tracts – tx to the brain from afferent
Descending Tracts – tx from the brain to the efferent neurons


Spinal Cord Grey Matter

Dorsal – cell bodies of interneurons on which afferent neurons terminate
Ventral – cell bodies of the efferent motor neurons supplying skeletal muscles
Lateral – cell bodies of autonomic nerve fibres supplying cardiac and smooth muscles and exocrine glands.



Each specific region of the body surface supplied by a particular spinal nerve. ‘Referred Pain’ may originate in a different part of a dermatome (shoulder hurts when it’s really the heart).



Response that occurs automatically without any conscious effort and is part of a biological control system linking stimulus and response
1) simple – built-in unlearned responses
2) acquired/conditioned – result of practice and learning


Reflex Arc

1) receptor
2) afferent pathway
3) integrating centre
4) efferent pathway
5) effector
Digression from arc – responses mediated at least in part by hormones, or local responses that don’t involve either nerves or hormones.


Spinal Reflex

Escape reflex – all components are in spinal cord. The brain can modify the reflex (i.e. you know something is going to hurt)


Withdrawal reflex

Polysynaptic Spinal reflex. Built-in is the inihibition of the muscle that antagonizes (opposes) the desired response, known as reciprocal innervation
The person is not aware of the stimulus until after it has already been processed in the spinal cord and the desired response has been carried out.


Stretch Reflex

Monosynaptic Spinal Reflex. The afferent neuron originating at a stretch-detecting receptor in a skeletal muscle terminates directly on the efferent neuron supplying the muscle, causing it to contract and counteract the stretch.


Crossed Extensor Reflex

Spinal Reflex. Ensures that the opposite limb will be in a position to bear the weight of the body as the injured limb is withdrawn from the stimulus.