W7 Nervous system Flashcards
List three basic functions of the NS
- Detect changes (stimuli) in the external and internal environment
- Evaluates info
- Responds by initiating changes in muscles or glands
Name and define major anatomical subdivisions of the NS
- The central nervous system
* Peripheral nervous system
What are the subdivisions of the PNS?
- The somatic NS
- The autonomic NS
- The enteric nervous system
Define neuron
Carry out most of the functions of the NS.
*Sensing changes on the outside and inside of the body
Moving muscles
Forming memories
Regulating behaviour
Describe a neurons important structural components
Axon terminal , axon , cell body , dendrites
Define neurons and relationship to each functional role
Dendrites receive infomation
Cell body - performs function of a cell
Axon - transmits messages to terminal
Axonterminal - communication to other cells (neurotransmitters)
Name 3 functional classes of neurons
Multipolar
Bipolar
Unipolar
Describe the function of Sensory neurons
Sensory (Afferent( neurons - detect changes in external and internal environment
Identify types of neuroglia in CNS
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
Explain the importance of the myelin sheath
Formed from wrappings of plasma membrane - appear white
The presence of myelin increases the speed of signal conduction
Describe how the myelin sheath is formed in the CNS and PNS
Produced by two neuroglia:
Obligodendrocytes - produce myelin sheath in the CNS
Schwann cells - produce myelin sheath in the PNS
What is SAME?
Somatic Afferent
Motor Efferent
What are the two main cell types in the NS?
Neurons and Neuroglia
Name 3 functional classes of neurons
- Sensory (afferent) neurons
- Interneurons
- Motor (efferent) neurons)
Describe the function of Interneurons
Involved in the processing of infomation coming into the CNS and initiating actions through motor responses ( telephone component)
Describe the function of Motor (efferent) neurons
Involved in controlling muscles or glands
What is Neuroglia?
Provides chemical and structural support for neurons.
Define Astrocytes
(CNS)Star shaped; largest most numerous type of glia , which transfer nutrients from the blood to neurons. ( neurganglia function)
Define Obligodendrytes
(CNS)Produce a myelin sheath that wraps around axons of CNS neurons (insulation)
Define Microglia
Acts as immune cells in the CNS destroying foreign organisms and damaged nervous tissue
Define Ependymal cells
(CNS)Responsible for the production of cerebrospinal fluid. They also aid in the movement of this fluid though ventricles
Define Obligodendrytes
(CNS)Produce a myelin sheath that wraps around axons of CNS neurons (insulation)
Describe the function of Satellite cells in the neuroglia PNS
Produce structural support and aid in the exchange of nutrient and the surrounding fluids
What parts of neurons make up white matter?
Consists of primarily myelinated axons
What part of neurons make up grey matter?
Consists of neuron cell bodies, dendrites, unmyelinated axons and neurolgia
What part of neurons make up grey matter?
Consists of neuron cell bodies, dendrites, unmyelinated axons and neurolgia
Describe the electrochemical basis of the resting membrane potential
Polar heads prevent movement of charged particle through the membrane
What does the term membrane potential refer to?
The difference in voltage between the inside and outside of the cell
How is membrane potential measured?
Recording electrodes is inserted into the cell the voltage different between the two electrodes is about -70mV
What is the resting membrane potential?
Resting membrane potential is the membrane potential recorded when a neuron is not receiving any input
What is the sodium potassium pump function?
PUMPS out 3 Na+ (sodium ions) PUMPS IN 2 K+ ions
What does the sodium-potassium pump do?
It helps to establish concentration gradients between the inside and the outside of the cell membrane
What is the potassium leak-channel?
Allows potassium to move down(leak out) it’s concentration gradient and outside of the cell
How is the resting membrane potential established??
K+ (sodium ions) wants to move DOWN the concerntration gradient out of the cell though the K+ (potassium ions) leak channels. As K+ moves out, the cell becomes more negative.
How can the membrane potential change?
Graded potentials
Action potentials
What is a graded potential?
A graded potential is a small deviation from the resting membrane of the neuron
What is summation?
Is the process by which graded potentials occurring close enough in time together can produce a bigger change in membrane potential
What is summation?
Is the process by which graded potentials occurring close enough in time together can produce a bigger change in membrane potential
How do neurons communicate?
- The generation of action potentials
2. The release of neurotranmitters
What is action potential?
Rapid and brief reversal of the membrane potential
Where are action potentials initiated?
At the axon hillock has a high concentration of voltage-gated sodium ion channels
What are voltage-gated ion channels?
Are proteins that respond to changes in the membrane potential by opening a channel in the membrane
What are voltage-gated potassium channels?
Opens in response to depolarisation and let K+ move out of the cell (down the concentration gradient)
What are voltage-gated sodium channels?
Channels that open response to a depolarisation of the membrane and let Na+ move into the cell
What is the action potential threshold?
The membrane potential at which voltage-gated sodium channels open, Na+ rushes in
What is meant by a refractory period?
Can initiate another action potential, need a bigger stimulus for second Ag
Is a point during action potential when another action potential can be initiated BUT needs a bigger stimulus
What is meant by the absolute refractory period?
Membrane potentials above 0, the voltage gated sodium channel inactivates and cannot be reactivated for another action potential
Where do action potentials go?
Are initiated in the axon hillock down the axon towards the axon terminals
How do action potentials propagate down unmyelinated neurons?
The action potential propagates down the axon by continuous conduction
How do action potentials propagate down unmyelinated neurons?
The action potential propagates down the axon by continuous conduction
How do action potentials propagate down myelinated neurons?
Propagates down the axon by saltatory conduction - speeds up action potential down the axon
What is the Node of Ranvier?
No insulation points Makes the propagation of a message 10x faster (saltatory conduction)
What is the purpose of a neurotransmiter release?
Allows electrical signal in the axon to be converted into a chemical signal
What is a chemical synape?
A point of communication between two neurons
What happens when an action potential reaches the presnaptic terminals?
- Action potential propagates into the presynaptic terminal
- Action potential opens voltage-gated calcium channels
- Calcium inside the terminal causes snaptoc vesicles to fuse with the presynaptic membrane and release neurotransmitter
- Neurotransmitter diffuses across the synaptic cleft and binds onto receptors for the neurotransmitter
What is a postsynaptic membrane potential that is hyperpolarised called?
Inhibitory synapse
What is a postsnaptic membrane potential that is depolarised called?
Excitably synapse
What are the functions of the CNS?
Detects changes in the outside/inside environment
Controls the bodys responses to external/internal changes
Generates emotions, memories, plans and thoughts etc
What parts of the skeleton first line of defense protect CNS?
Brain located in skull formed by interlocking cranial bones
* The spinal cord is enclosed within vertebral column
What parts of the skeleton protect in the second line of defense?
Cranial meninges surround and protect the brain
Spinal meninges surround and protect the spinal cord
What is the first layer in the meninges layer?
Dura mater - the mot superficial and the strongest and adheres to the interior surface of cranial bones
What is the second meninges layer?
Arachnoid mater - below dura mater, located between the dura mater- filled with interstitial fluid
what is the third meninges layer?
Pia matter - innermost membrane adheres to the surface of the brain and spinal cord
What is the blood brain barrier?
Prevents the flow of many substances from the bloodstream into the interstitial fluid of the NS
How is the blood brain barrier formed?
By Tight cell junctions between the endothelial cells of capillaries supplying the brain
Astrocytes also contribute to the function.
What is the cerebrospinal fluid?
Clear, colourless liquid that circulates continuously through cavities in the brain and spinal cord in the subarachnoid space
What are the three main functions of the cerebrospinal fluid?
- Mechanical protection
- Chemical protection
- Circulation
Describe the mechanical protection function of the cerebrospinal fluid?
Serves as a shock absorber that protects the brain. Also allows brain to float
Describe the chemical protection function of the cerebrospinal fluid
Provides optimal chemical environment for neural function
Describe the circulation function in protection of the cerebrospinal fluid
Provides a medium for the exchange of nutrients and wastes between the blood and nervous tissue
How is CSF circulated
Filled with CBF, these ventricles are connected by narrow ducts that allow the circulation of CBF through these connected ventricles
How is CSF circulated
Ventricles are connected by narrow ducts that allow the circulation of CBF through these connected ventricles
What cells produce CBF?
Ependymal cells which form the CSF by filtering the blood plasma
Where is CSF produced?
Formed at sites call choriod plexuses - these are a network of capillaries in the walls of the ventricles
What is the midbrain function?
Motor control, visual and auditory processing, consciousness
What is the pons function?
Relay from cerebrum to cerebellum, regulation of respiration and autonomic functions
What is the Medulla function?
autonomic functions of breathing, heart rate, blood pressure, vomiting
Describe the Cerebellum
Automatic processing centre that monitors proprioceptive, visual, balance.
- Maintains balance
- Refines movements at conscious and subconscious levels
What is the Diencephalon?
Mainly thalamus relay system for sensory from cerebral cortex and hypothalamus links the nervous and endocrine system
What are two major parts of the Cerebrum?
The cerebral cortex - grey matter (cell bodies)
White matter tracts (myelinated axons)
Define Cerebral cortex
Conscious thought, memory storage and processing, skeletal muscle contractions
Define White Matter Tracts
Connects regions of the cerebral cortex with eachother and the rest of the brain
What are the folds and the grooves of the cerebral cortex called?
folds = Gyri
deeper grooves = fissures
shallower grooves =suculi
What is the most prominent fissure?
Longitudinal fissure separates the LHS and RHS cerebral hemispheres (connected by white matter called the corpus callosum)
What are the names of the cerebral lobes and where are they located?
Frontal
Parietal
Temporal
Occipital
What are the function of the cerebral cortex?
Sensory areas
Motor areas
Association areas- complex processing
What are the primary sensory areas of the cortex located?
Primary somatic motor area
Primary somatic sensory area
Where is the primary visual area located?
Occipital lobe
Where is the primary auditory area located?
Temporal lobe
Where is the primary motor area located?
In the frontal lobe
What are the three main types of white matter tracts present in the brain
Association tracts Commissural tracts
Projection tracts
Describe Association tract
project between the folds of the folds (gyri) of the same cerebral hemisphere
Describe Commissural tracts
Axons that project from gyri from LHS to RHS hemisphere:
- The corpus callosum
- The anterior commissure
- The posterior commissure
Describe projection tracts
These contain axons that project from the cerebrum to lower parts of the brain
What is the function of the thalamus?
It’s primary function is the relay and processing of both ascending sensory info and descending motor info
What is the 6 hypothalamus’ functions?
- Controls body temp
- Production of hormones
- Regulation of emotions
- Regulation of eating/drinking
- Control body temo
- Regulates sleep
What structures make up the brain stem?
Midbrain, Pons, Medulla oblongata
What are the broad functions of the brainstem
Regulates involuntary functions such as breathing, heart rate, blood pressure and digestion
Where is the cerebellum located and what does it do?
Evaluates voluntary movements of skeletal muscle, important in maintaining posture and balance. (back brain)
What is the external structure of the spinal cord
Grey and white matter
What is the interal structure of the spinal cord?
Encased in meninges, pia mater, arachroid mater, dura mater
What is the name of the superior enlargement of the spinal cord?
Cervical enlargement - thickening of spinal cord
What is the inferior enlargement of the spinal cord
Lumbar enlargement
What is the name of the conical portion at the inferior end of the spinal cord?
Conus medullaris
What are the spinal nerve roots?
The points where bundles of axons that make up spinal nerves connect with spinal cord
What are the spinal nerve roots?
- Posterior (dorsal ) root
2. Anterior (ventral) roots
Where are the cell bodies of sensory axons located?
The doral root ganglia (a swelling of the nerve root)
What types of axons are in the anterior roots?
Axon of motor neurons
What is the name given to the grey matter on each side of the spinal cord
- Posterior horn contains inter neurons and axons of sensory neurons
- Anterior horn contains
What is the function of the spinal cord?
- The propagation of nerve impulses from the brain to the body, and from the body to the brain
- The integration of sensory and motor information
