Nervous System Flashcards
What is the main function of the nervous system?
Control and co-ordination which is fast,generally short lived responses,electrically mediated
What are the cellular elements of the nervous system
-neurons
-glial cells(sticky)
>there is more than neurons ratio is between 3:1 to 10:1
>there are several subtypes
>their role is to nurture neurons
>sham cells are an example of glial cells
What are the types of glial cells
-ependymal cells
-microglia
-astrocytes
-obigodendrocytes
Ependymal cells
E.g line ventricles and assist in production of CFS(cero spinal fluid)
Microglia
-Remove debris and waste by phagocytosis
-can be considered as the immune cells
-they are scattered throughout the grey and white matter
-can release cytokines
Astrocytes
-blood brain barrier
-absorb/recycle neurotransmitters
-also responsible for homeostatic processes such as ensuring the right concentrations of minerals such as potassium exist in order to prevent neurons from depolarising
Neurons
-functional units of the nervous system
-main function is to process information
-there are 3 main regions
>cells body ands dendrites( inputs which receive the information)
>Axon(transmission)
>Axon terminals(outputs eg contacting another cell)
-all the functions are mediated by neuronal membrane functions which are dependant on membrane potential
How are neurons classified
-Because neurons are very diverse they are classified based on their structure eg uni,multi,bipolar
-can also be classified due to their functions
List all the neuronal pools
-divergence
-convergence
-serial processing
-parallel processing
-reverberation
Divergence
-spread of information to several neurons
-eg significant divergence of sensory information reaching different parts of the nervous system
Convergence
Several neurons synapse On a single neurone
Eg voluntary breathing vs breath holding
Serial processing
-Stepwise processing of information
-nociceptive pathways
Parallel processing
-several neurons receive the same information so divergence must occur
-eg stepping on a pin -for moves, weight moves,sense of pain
Reverberation
-positive feedback loop(amplifying change)
-eg Maintenance of wakefulness
Organisation of the nervous system
-Nervous system is divided into central nervous system and peripheral nervous system
-central nervous system is divided into the brain and
The spinal cord
-peripheral nervous system is divided into afferent and efferent
-efferent is divided into somatic and autonomic
-autonomic is divided into the sympathetic and parasympathetic
-afferent is somatic and visceral
Parts of the nervous system
Brain
Spinal cord
What are the layers protecting the brain
Skull
Bone
Meninges
Csf
Name the lobes of the brain
-frontal lobe(front)
-temporal lobe(side)
-occipital lobe(back)
-parietal lobe(top)
Divisions of the brain
-medulla
-pons
-midbrain
-limbic system
-diencephalon
-cerebrum
-cerebellum
(Increases in complexity)
The brain stem (medulla,pons,midbrain)
-very old
-basic functions include the respiratory rhythm , blood pressure regulation and vomiting
-origin of cranial nerves
-midbrain constitutes part of the reticular formation eg maintenance of wakefulness as well as some aspects of visual and auditory processing
What are cranial nerves
-12 cranial nerves
-all innervate head and neck except the vagus nerve which is parasympathetic
Parts of the diencephalon
Thalamus and hypothalamus
Thalamus
-final relay point for sensory information that will br transmitted to the cortex =acts as a filter eg does the information need to go to the brain?
Hypothalamus
• Controls and integrates activity of the ANS
• Controls the pituitary gland (release hormones) and releases its own
hormones
• Regulates emotional and behavioural patterns e.g. eating and drinking
• Controls body temperature
• Subconscious control of skeletal muscle in relation to behavioural patterns
e.g. rage, aggression, pain
• Coordination between voluntary and autonomic functions e.g. increased HR
when thinking about dangerous situations
• Contains the suprachiasmatic nucleus which controls circadian rhythms.
Functions of the cerebellum
• Electrical stimulation = no loss of sensation or movement
• However, loss of cerebellum = significant motor abnormalities
• Overall, role in controlling postural muscles and rapid muscular activity e.g. typing, playing a musical instrument
• Inputs –motor cortex, vestibular system, proprioceptors
• Outputs –via thalamus to motor cortex and premotor cortex and to vestibular nuclei and reticular formation
What does the cerebellum do?
• Supplement motor activity – particularly control of posture and correcting rapid movements initiated in motor cortex (comparator)
• Motor learning eg shoe laces
• Much of what we know comes from damage
• Staggering walk and difficulty standing –cerebellar ataxia
• Loss of coordination (asynergia) and muscle tone (hyptonia)
Cerebrum
• Separated into two cerebral hemispheres by the longitudinal fissure, each hemisphere divided into four lobes
• Hemispheres connected by the corpus callosum
• Outermost layer of each hemisphere is the cortex, below which is the white matter.
• The cortex enlarges at a greater rate than the underlying white matter – hence its convoluted appearance. Peaks are called Gyri, troughs are called Sulci
Cerebrum-the cortex
• Cortex divided into a number of functional areas – –motor
–sensory –association –integrative
Sensory cortex
• Mainly the posterior half of both cerebral hemispheres, association areas adjacent to these regions
• Primary Somatosensory Area (Area 1,2,3) -located directly posterior to the central sulcus
• Primary visual area (Area 17) -posterior tip of occipital lobe
• Primary Auditory Area (Area 41, 42) –superior part of temporal lobe
Association areas
Interpret incoming information (or coordinate motor responses) • Somatosensory Association Area (5,7)
integrates and interprets sensations e.g. determining shape and texture
• Visual Association Area (18,19)
• Premotor Area (6)
Integrative centres
Integrative Centres
• Coordinate information from a number of association areas (and direct complex movements)
• Also undertake complicated analytical functions e.g. abstract thought
• –Generalinterpretivearea–Wernickesarea
• –integrates sensory info and oversees access to visual and
auditory memories
• –damage limits the ability to interpret what is seen or heard
Motor Activity
• Electrical stimulation of areas of the cortex resulted in movements of specific contralateral areas
• How we generate voluntary movement not clearly understood –But possible to record electrical activity in the pre-motor
cortex, almost a second before movement = readiness potential
