Neuroanatomy Flashcards
What are the two areas of the nervous system and what is included in each of these categories?
PNS
- Cranial nerves (come off brain stem)
- Spinal nerves (come off spinal cord)
- Ganglia (dorsal root ganglia and autonomic ganglia)
CNS
- Brain and spinal cord
What are ganglia?
They are cell bodies of neurones that exist outside of the nervous system
Whats the purpose of the CNS?
Its the control centre for information processing, responding to sensory information, some are voluntary and some are involuntary
Whats included in the CNS and PNS when organising the nervous system in higher order organisms ?
PNS
- Nerve
- ganglia (aggregations of neurones)
- sensory receptors
CNS
- Brain
- spinal cord
Label this neuron…
Why are there several dendrites in neurons?
They are multi-polar so there are several denrites
What is around the axon in a neuron?
myelin which is white in colour and provides insulation to help speed up conduction in the neuron
Tell me 3 functions of a neuron?
Recieve stimuli
Transmit nerve impulses or action potentials
Activate muscles
What the role of a dendrite?
They collect electrical signals and carry input to cell body. They do this with chemical signals as well
Whats the role of the cell body/ Soma (these mean the same thing)?
It integrates signals and generates action potentials
Whats the role of an axon?
Transmits signals over long distances from the cell body to the axon terminals in order to communicate to the next neuron or organ its transmitting information to
Neurons in all species are the functional units of the nervous system, they are organised into a functional network which is capable of what?
- resonse to stimuli
- information processing
- communication
Differences in the nervous system amongst species are due to what?
Not the neurones but how they are organised
What are the ways in which neurons can be organised in different species give an example of a species which possess this type of organisation?
Nerve nets (simple organisms have nerve nets): hydras, jellyfish etc.
Cephalisation: starfish (echinoderms)
CNS: humans, cats, dolphins
PNS: humans, cats, dolphins
Name a multicellular organism without a nervous system?
sea sponges
Invertebrate nervous systems are specialised for what?
- stimulus/ response
- receptor/ effector
- reflexes, conditioned responses e.g. escape from predators
What are nerve nets?
What organisms is it found in?
The simplest form of the nervous system found in some invertebrates such as hydras and jellyfish
Individual nerve cells exist in a net-like formation scattered in layers of body wall.
Why do neurones in a nerve net exist in a ‘loose network’?
In order to allow for contraction and expansion of the body cavity
What do nerve nets lack?
distinct central or peripheral regions, and anything that resembles a brain
Nerve nets have no associative activity they only have what?
Reflexes (with action potentials)
Can nerve signals travel in both directions?
In an electrical synapse the signals can travel in both directions
In a chemical synapse the signals can only travel in one direction
What type of information can neurons carry?
What does the neuron do with the information that it recieves?
Information from sensory organs that detect touch, light or other changes in the environment
These neurons in turn contact neurons that control movement of the organism e.g. swimming
Species like star fish (echinoderms) display some centralisation of the nervous system explain the organisation of the nervous system in star fish and what this allows in terms of movement ?
They have a ring of neurons located in the centre with somple bundles of neurons (radial nerves) extending from the right to the tip of each arm
Radial nerve nets form nerve nets permitting coordinated movement of each arm and the tube feet located on the surface of the arm
When species show cephalisation, how is this known from their structure?
Cephalisation is an evolutionary trend over mant generations where the mouth, sense organs and nerve ganglia become concentrated at the front end of the animal producing a head region
The animals tend to show bilateral symmetry (right and left half and a head end)
In animals with bilateral symmetry what runs down the length of the body?
In animals like flatworms which show bilateral symmetry, there are 2 nerve cords which run down the length of the body
What does cephalisation allow?
The system to be more complex and have more control over the muscles for movement
There is diversity of the nervous system across organisms, tell me all the parts as they build up to make an organism complex like us?
What does a vertebrate nervous system contain?
- sophisticated sensory mechanisms
- clear differentiation of CNS and PNS as well as sensory and motor nerves
- elaboration of brain structure
What are the 3 main parts of the brain and what does each include?
Forebrain (cerebrum, optic structures, olfactory lobe)
Midbrain
Hindbrain (brainstem- pons, meddulla, cerebellum)
What does the hindbrain allow coordination of?
motor reflexes in vertebrates; regulation of autonomic processes
Tell me some similarites or differences you can see in the following image?
- cerebrum gets larger as you move to more complex organisms
- Earlier vertebrates have a smooth cerebrum
- forebrain is up front
- midbrain is the first part of the brain stem
- hindbrain is the lower part of the brain stem
What are sulci?
Infoldings of the cerebral hemisphere that form ‘valleys’ between the gyri
(singlular= sulcus)
What are gyri?
Ridges of the infolded cerebral cortex
(singular= gyrus)
Do all mammals have a gyri and sulci?
No
What does the presence of the sulci and gyri allow?
The presence of both allows for more specialised systems in the cortex and for more neurons which all contributes to a more complex organism as there is a larger surface area present when not smooth surface
What are the subdivisions of the CNS?
What are the subdivisions of the PNS?
What is another term for the forebrain?
Prosencephalon
What is the Proscencephalon divided into and what are each part representing?
Telencephalon (cerebrum)- the outer portion
Diencephalon (thalamus and hypothalamus)- can’t see from the outside of the brain
What is another name for the midbrain?
Mesencephalon- the top of the brain stem
What is another name for the Hindbrain?
Rhombencephalon
What is the Rhombencephalon divided into and what does each part represent?
Myelencephalon (medulla)
Metencephalon (pons and cerebellum)
The brain develops first as a 3 ‘vesicle’ structure, what are these 3 structures?
prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)
The brain then later develops from a 3 vesicle structure to a 5 vesicle structure. what are these 5 structures?
Forebrain:
telencephalon
diencephalon
Midbrain:
mesencephalon
Hindbrain:
myelencephalon
metencephalon
What are the 3 parts of the brain stem and put them in order from outside to inside?
Outside:
Midbrain
Pons
Medulla oblongata
Inside:
What are the CNS brain divisions?
- cerebrum
- diencephalon
- brain stem
- cerebellum
Label the brain lobes
Label the brain divisions in the CNS
What are the 4 different functional areas of the cerebrum in the CNS?
- motor
- sensory
- vision
- auditory
What are the 2 regions associated with the motor region?
Primary motor
premotor
What lobe is the primary motor and premotor region in?
Frontal lobe
(a stroke would significantly impair motor ability)
What is in the sensory region of the brain?
Primary somatosensory
Somatosensory association area
What lobe is the sensory region in?
Parietal lobe
What are the 2 parts of the visual region?
Primary vision
Visual association
What lobe is the vision region in?
Primary visual- back of occipital lobe
visual association- occipital lobe
What are the 2 parts of the auditory region of the brain?
Primary auditory
Auditory association
What lobe is the auditory region found in?
Temporal lobe
Functional areas of the brain
Do the functional areas of the brain exist in isolation?
No
Do the functional areas of the brain always have an association area?
yeah
The human CNS is divided into 7 major parts, what are they?
Brain divisions
- Cerebrum
- Diencephalon (only visible in midsagittal view of the brain)
Brian stem
- Midbrain
- Pons
- Medulla
- cerebellum
- spinal cord
Tell me about the grey matter in the CNS
- cell bodies of neurons residue in the grey matter
- it has a pinkish/ grey colour in the brain, as it is a major component of the CNS
- H shaped in the transverse section of the spinal cord
Tell me about the white matter in the CNS?
- myelinated axons reside in the white matter
- these axons connect different parts of the grey matter to one another
What are the different ways the brain can be viewed and describe the orientation/ where the cut would be?
the sagittal section can be slightly left, centre or sligtly right. If in the middle it is called the midsagittal section
Label the directions in the head of a forward looking human
What 3 main things provide protection to the CNS?
- bone (skull and vertebrae column)
- Meninges
- CSF
What are the 3 protective tissue layers of the CNS and descirbe the characteristics of each one that would help to identify them?
- Dura: Superficial most and strongest, usually in contact with the bone
- Arachnoid: Adhered closely to dura, web-like in appearance (adheres to inner surface of dura, not a thick layer)
- Pia: Deepest layer, in direct contact with CNS tissue (delicate, thin and flimsy layer)
Whats found in the subarachnoid space?
vessels and CSF
Label these structures in the brain
Whats CSF?
Whats its appearance?
Whats it produced by?
Where does it circulate?
CSF is the cerebrospinal fluid
its a clear, cell-free fluid
Its produced by the choroid plexus (ependymal cells)
Circulates in the subarachnoid space (space between the arachnoid and pia mater)
Identify the layers of protective tissue
Afferent input (sensory) to the neocortex comes from a variety of areas, tell me some of these areas?
- Ascending information from the thalamus
- Ascending information from the brain stem and other parts of the forebrain, also the hypothalamus
- Axons travelling between hemispheres (commissural fibres- axons that connect the two hemispheres of the brain)
- Information from the ipsilateral cortex
What are commissural fibres?
Axons travelling between hemispheres
Outputs from the neocortex is excitatory from what?
pyramidal cells (uses excitatory neurotransmitters such as glutamate)
All parts of the cortex project to where?
The thalamus
Axons from motor and somatosensory corticles project to what?
the basal ganglia
Axons project to what?
brainstem (nuclei) and spinal cord
contralateral hemisphere
ipsilateral hemisphere
What does the brain stem connect?
The spinal cord to higher centres (cerebrum and cerebellum)
Whats the function of the brain stem?
- serves as a conduit for ascending and descending tracts connecting the spinal cord to higher centres (cerebrum, cerebellum)
What important things does the brain stem contain?
- important reflex centres associated with control of respiration, heart rate, blood pressure and consciousness
- contains cranial nerve nuclei
Label this simple diagram
What does the cerebellum integrate?
Where does it deliver this information to and why?
Ascending (proprioceptive) information, and feeds it back to cerebral cortex to refine movement
What are the functions of the cerebellum?
- modifies movement (compares sensory information with pre-motor information)
- Maintenance of upright posture
- maintenance of the tension or firmness (i.e. tone) of the muscle
- Aids the cerebral cortex in planning sequential movements to make smooth progressions from one movement to the next
- synergy of movement- motor coordination
- balance
What are the cerebellar inputs?
- spinal cord
- cerebellar cortex
- vestibular system
- motor systems in neocortex
What are the cerebellar outputs?
- vestibular systems
- brain stem
- muscle spindles
- motor and pre-motor corticles
What is the spinal cord?
A two-way conduction pathway and reflex centre
How many pairs of spinal nerves are there?
What are they and their spinal location?
These give rise to the peripheral nerves of the body
Label the spinal cord parts and the sub-parts and the parts of the body they help control?
What does each spinal nerve have?
What is located/ enters here?
A Dorsal root (posterior) through which afferent fibres enter, and which contains the dorsal root ganglion with the cell bodies of the afferent fibres
and
A Ventral root (anterior) through which the efferent fibres leave. Their cell bodies are within the spinal cord
Label this spinal nerve image
What are reflexes/ instinctive behaviour?
A survival mechanism
An inherited ‘hard-wired’, pre-set behaviour that does not require learning, practice or experience
simplest type of animal behaviour which is performed without conscious thoughm usually a rapid, automatic/ involuntary response to stimuli
give an example of a reflex in:
- Invertebrates and vertebrates
- mammals
Invertebrates and vertebrates: locate food (foraging behaviour), locate and live in a suitable habitat, escape predators
Mammals: knee-jerk reflex (humans), suckling behaviour in newborns
Whats the reflex arc?
- receptor (site of stimulus)
- sensory neuron (transmits stimulus)
- integration centre (can be mono (A single synapse between a sensory fibre from a muscle and an alpha-motor neuron (Rapid response time, minimal delay) or polysynaptic)
- motor neuron (conducts impulse to effector)
- effector (muscle or gland)
Tell me about spinal reflexes?
Somatic spinal reflexes provides information on integrity of the reflex pathway and degree of excitability of the spinal cord
What do polysynaptic reflexes involve?
multiple synapses between sensory axons, interneurons and motor neurons
Tell me about interneurons?
control more than 1 muscle group
produce either EPSPs or IPSPs
Give an example of a polysynaptic reflex
The 2 divisions of the autonomic nervous system are responsible for what?
Maintenance of homeostasis
The autonomic nervous system is continuously under…?
Continuously under active normal conditions, with each having discreet and independent functions (antagonistic functions)
ANS and the endocrine system control what?
Control’s the bodies internal organs, thus controlling the circulation of the blood, activity of the gastrointestinal tract and body temperature
What does the ANS innervate?
smooth muscle, cardiac muscles and glands of internal organs (involuntary)
Which part is the sympathetic/ parasympathetic systems?
