Nervous System Anatomy Flashcards
What are some of the main functions of the nervous system?
- Communication
- Regulation of internal events
- Storage of information
- Behavioural organisation
- Sensations, perceptions, emotions
- Make us who we are, how we feel and move in the world
What segments can the nervous system be split into?
- Central: -brain and spinal cord
- Peripheral: - spinal nerves (come off spinal cord) and cranial nerves (come off brain and brain stem)
What does sensory info come through to go into the spinal cord?
- Somatic afferents (sensory info coming from body)
- Visceral afferents (sensory info coming from visceral organs)
What happens to sensory info once it reaches the spinal cord?
It travels up to the brain to be processed then comes back down the spinal cord to be released as motor info.
What does motor info travel through to get to desired area?
- Somatic efferents (for info going to skeletal muscle)
- Visceral efferents (for general info and info going to smooth muscle, cardiac muscle and glands)
What is there between going from spinal cord to visceral efferents?
A synapse in between the 2 fibres.
What is the brain separated into on the surface?
2 cerebral hemispheres separated by longitudinal fissure (a groove in the middle)
What things make up the cerebrum?
- Gyri (ridges) and sulci (grooves), these give the characterisitc folded appearance
- Outer grey layer and an inner white matter
What is the purpose of the gyri and sulci?
They increase surface area meaning more nerve fibres can be in the brain and it helps in the limiting cavity of the skull.
What is the function of the cerebellum?
Controls movement, specifically co-ordinating movement and precision with integration of the sensory system.
What is the brainstem comprised of?
Midbrain, pons and medulla.
What is the function of the brainstem?
Breathing
Heart rate
What parts of the brain make up the forebrain?
Telencephalon (cerebrum)and diencephalon(thalamus and hypothalamus)
What makes up the midbrain and what is its function?
Mesencephalon is the midbrain
Plays role in vision, hearing, motor function and arousal state
What makes up hindbrain?
Rhombencephalon
What are glia?
Non neuronal cells of the brain and nervous system?
What are examples of glia and their function?
- Astrocytes=involved in nutrient supply to neurons in the CNS
- Ependymal cells= involved in production eg.CSF
- Oligodendrocytes= neuronal support and myelin formation in the CNS
- Schwaan cells= neuronal support and myelin formation in PNS
What is the central canal of the spinal cord surrounded by?
Ependymal cells
What does homunculus show?
How diproportionate areas of the sensory and motor function are represented in the brain.
Eg. bottom of body represented by top of brain
What 4 lobes can the brain be split into?
- Frontal
- Occipital
- Parietal
- Temporal
What is the function of the frontal brain lobe?
Long term memory, speech, movement, personality
What is the function of the parietal brain lobe?
Sensory integration, language interpretation, spatial/visual perception
What is the function of the occipital brain lobe?
Visual processing (colour, light)
What is the function of the temporal brain lobe?
Primary auditory cortex, memory, understanding language
What is the corpus callosum and its function?
Right and left cerebral hemispheres joined by corpus callosum.
Fibres cross over the body, so opposite side of brain controls opposite side of body.
It is linked to cognitive function
How is the spinal cord arranged?
Into cervical, thoracic, lumbar, sacral and coccygeal parts.
Where is the conus medullaris?
At lower end of spinal cord at L1-L2.
What is the cauda equina?
Nerve rootlets at L2-L5, CSF can be extracted from here in the subarachnoid space. It sits in the lumbar cistern formed by the subarachnoid space.
Cauda equina extends from conus medullaris to S2.
What is the meninges made up of?
3 layers that wrap around brain and spinal cord
Dura
Arachnoid
Pia
Describe the dura
thick membrane and made of dense irregular connective tissue.
Describe the pia
Innermost layer of meninges and is delicate and allows blood vessels to pass through and nourish brain
Describe the arachnoid
Does not pass into the sulci and is pressed against the dura
What 2 layers does the dura split into in the brain?
Periosteal (joined to bone of skull)
Meningeal
What does the subarachnoid space consist of?
Blood vessels
How is the peripheral nervous system arranged?
Spinal nerves (31 pairs) Cranial nerves (12 pairs) Spinal nerves divided into C (8), T(12), L(5), S(5) and Cox(1)
How many sensory and motor axons does a spinal nerve contain?
Many
What do axons of spinal nerves (sensory neurons)supply?
Supply structures in a well defined part of the body, these regions are called dermatomes for sensory neurons.
What do axons of spinal nerves (motor neurons) supply?
Blocks of muscle called myotomes
Which is the only spinal nerve without a dermatome?
C1
What do the cranial nerves do?
Provides sensory and motor supply to head and neck structures.
What are the names of the 12 cranial nerve pairs and their broad functions?
- Olfactory-smell
- Optic-vision
- Occulomotor-eye movement
- Trachlear- eye movements
- Trigeminal- motor to muscles of mastication and general sensory to face
- Abducens-eye movements
- Facial-muscles of facial expression
- Vestibulocochlear-hearing and balance
- Glossopharyngeal-swallowing, taste
- Vagus-wandering nerve supplying heart, lungs and gut
- Spinal accesory-neck muscles
- Hypoglossal-muscles of toungue
What types of nerve can we get in the PNS?
Pseudo-unipolar sensory neuron supply to sensory receptors
- Multipolar neuron supply to effector organs, skeletal striated muscle
- Autonomic multi-polar neuron (synapse between 2 neurons in this) supply to glands, smooth muscle, cardiac muscle
How does info travel through the spinal cord?
Through afferrent system, through dorsal root ganglion to dorsal horn, somatic or visceral sensory nuclei and then to brain.
Brain feeds back down to ventral horn, somatic motor nuclei here, efferent signal exit to muscle and glands.
Autonomic efferent nuclei exist in the lateral grey horn and mediates sympathetic nervous system.
What components make up a neuron?
- Dendrites
- Nucleus
- Cell body
- schwaan cells
- Myelin sheath
- Node of ranvier
- Axon terminal
How can neurons be categorised?
By shape: -Unipolar -Bipolar -Multipolar Can be myelinated or not (myelin speeds up transmission) Can have 1-1000's of connections
What is the role of the filum terminale?
It anchors the spinal cord
What are some of the deep structures of the brain and their role?
-Limbic system= emotions and emotional behaviour (amygdala)
Learning and memory (hippocampus)
-Basal ganglia = control of movement
-Thalamus = sensory relay centre between spinal cord and cerebral cortex
-Hypothalamus = temp. regulation, other homeostasis
-White matter tracts = eg. corpus callosum
What is the CSF?
It is a clear colourless liquid similar to plasma but has a much lower protein content and different electrolyte levels.
What is the role of CSF?
- Cushions brain against impact/ movement and own weight
- provides stable chemical environment for brain
- nutrient and waste exchange between nervous tissue and blood
- Ageing; reduced CSF turnover, metabolic waste buildup may contribute to neurodegenerative disease
Where is CSF?
Fills ventricles of brain and subarachnoid space of meninges.
Where is CSF produced and what is this process like?
Most produced in choroid plexus in lateral and 4th ventricles.
There is constant turnover of CSF, 125-150 ml at a time.
CSF is resorbed into the venous system via arachnoid granulation.
What are spinal cord tracts?
Bundles of nerve fibres that run up/down the spinal cord.
They can be ascending or descending
They will be autonomic, sensory or motor
What are some examples of spinal cord tracts and their roles?
- Spinothalamic tract = ascending, sensory, pain and temp
- Corticospinal tract = descending, motor, voluntary movement
What are the locations of spinal tracts?
-In specific regions of the cord
-Some decussate (cross over)
They can be ipsilateral (same side) or contralateral (opposite side)
What may cause partial spinal cord injuries?
Damage to specific tracts.
Loss of specific functions below level of injury.
Tracts that decussate below lesion; lose function on contralateral side of body, if no decussation, ipsilateral side.
What are the spaces and potential spaces between meninges layer?
In brain:
- Epidural potential space
- Subdural potential space
- Subarachnoid space; CSF here and blood vessels
Epidural space in spinal cord contains fat and venous plexus.
What is meningitis?
A viral or bacterial illness
Caused by inflammation of pia mater and arachnoid mater, subarachnoid space.
What happens due to meningitis?
In short term there are many symptoms eg. headache and rash
In long term it can cause cerebral oedema as raised intracranial pressure can cause herniation
How would we diagnose meningitis?
Increased WBC’s in CSF (+/- bacteria), extract using lumbar puncture
How can we stop meningits?
Vaccinate and know the signs
What is the blood, brain barrier?
Several features that prevent harmful substances getting into brain and SC from blood.
What are some eg’s of components of the BBB?
- Capillaries in nervous tissue
- Ependymal cells line ventricles and spinal cord
How do capillaries in nervous tissue act in the BBB?
- Tight junctions between endothelial cells restrict movement
- thick continous basement membrane
- astrocytes processes cover vessel
How do ependymal cells lining ventricles and spinal cord act in the BBB?
Tight junctions restrict movement.
Why do some areas of BBB have different permeabilities and give examples?
In order to carry out their function.
eg.- sensory function of area postrema (medulla) for toxin detection and vomiting response
secretory function of pituitary gland (secretes hormones)
What is the permeability of the BBB normally like?
Keeps out toxins, pathogens etc
Stops fluctuations of ions, nutrient, metabolite concentrations in CNS (eg. increased K+ levels would affect nerve impulses0
Permeable to substances that can diffuse across (water, small lilophilic molecules , gases)
Many drugs cant cross BBB.
What separates the fronta lobe from the parietal lobe?
The central sulcus
What separates the temporal lobe from the frontal and parietal lobes?
Lateral fissure
What separates the occipital lobe from the parietal lobe?
The parieto-occiptal sulcus
Where if the 3rd ventricle located?
Either side of the thalamus
What does the brachial plexus do?
Provides innervation to the upper limb
What does the lumbar sacro plexus do?
Provides innervation to the lower limb
What is the white matter of the spinal cord primarily composed of?
Myelinated axons
What is the dorsal root ganglion composed of?
The cell bodies of afferent neurons
What is a nerve plexus?
A collection of nerves that supply specific body regions
What is the spinal origin of the brachial plexus?
C5-T1
What do nociceptive fibres transmit info about?
Pain
