Structure of the Nervous System (Cranial Nerves) Flashcards
What components is the CNS composed of?
Brain
Spinal Cord
What are the 3 major brain regions?
Forebrain:
- Cerebrum
- Diencephalon
Brainstem:
- Medulla
- Pons
- Medulla Oblongata
Cerebellum
What anatomical references are used to identify portions of the brain?
Dorsal (top half) and ventral (bottom half) curves along the body as we are bipedal - same as inferior and superior
How do we describe features in relation to the midline?
Ipsilateral is same side of midline
Contralateral is on different sides of the midline
What is an afferent?
where the neuron is projecting to
What is an efferent?
where the neuron is projecting from
Give an example of an efferent and afferent
A neuron projecting from the thalamus to the cortex is both a thalamic efferent and cortical afferent
How many cranial nerves are there?
12 bilateral cranial nerves (a pair of each nerve - one on either side)
Numbered from anterior to posterior
Describe the efferent and afferent fibres of the cranial nerves
Afferent sensory fibres - sensory information from periphery to brain
Efferent motor fibres - motor instructions from brain to periphery
Outline the 12 cranial nerves
- Olfactory I
- Optic II
- Oculomotor III
- Trochlear IV
- Trigeminal V
- Abducens VI
- Facial VII
- Vestibulocochlear VIII
- Glossopharyngeal IX
- Vagus X
- Accessory XI
- Hypoglossal XII
Oh Oh Oh To Touch And Feel Very Good Velvet A H
What is the role of the olfactory nerve CN1?
purely sensory - olfaction (smell)
olfactory epithelium sends signal to olfactory bulb which outputs to:
Hippocampus
- odour memory
Hypothalamus Amygdala
- motivational and emotional aspects of smell
Olfactory Cortex
- conscious perception of smell
What is the function of the optic nerve CN2?
purely sensory - vision
carries info from retinal ganglion (rods/cone cells) to lateral geniculate nucleus in thalamus which projects to the visual cortex (occipital lobe)
Palpebrae muscles - controlled by CN II for eyelid opening
What are the roles of the 3, 4, and 6 cranial nerves??
Occulomotor, trochlear and abducens
Motor - eyeball and eyelid movement
Parasympathetic - pupillary constriction and accomodation
Outline the eyeball movements mediated via cn3?
CN3 mediates eyeball movement up & down via superior/inferior rectus muscles
Also mediates downward & outward movement via inferior oblique muscle, inward movement via medial rectus
What eye movements is cn4 responsible for?
CN4 moves eye upwards & inwards via superior oblique
What is the role of cn6 in eye movements?
CN6 moves eye laterally via lateral rectus muscle
Explain which muscles are involved in moving the eye side to side
To move eye outwards and back in again, need more than just relaxation of lateral rectus
Medial rectus has to contract also to pull eye in
How can we assess cranial nerve function affecting a patients vision?
To test CN for someone’s vision we ask patient to move eye, up, down, side to side, and to corners to figure out which cranial nerve is causing the problem
What is the function of the trigeminal nerve cn5?
Face sensation
Trigeminal nerve receives somatosensory input from the 3 facial regions:
- Ophthalmic
- Maxillary
- Mandibular
Input travels from (periphery) each of the three regions via the trigeminal nerve efferent to the somatosensory cortex
What is the role of the facial nerve CN7?
sensory - sensations of taste from ant. 2/3 of tongue
Motor - muscles for facial expression and stapedius muscle
Parasympathetic - salivary, lacrimal, nose and palate gland secretions
What is the stapedius muscle function?
Stapedius muscle is smallest in the body - contracts to block out certain noises
What does the Cn8 vestibulocochlear nerve regulate?
Gets sensory info to mediate hearing and balance
How does vestibulocochlear nerve mediate hearing?
via cochlea cells signalling to medial geniculate nucleus in thalamus which signals to the auditory cortex in the temporal lobe via cn8
How is balance regulated via the vestibulocochlear nerve?
via vestibular hair cells send sensory info to ventral postereolateral nucleus in thalamus which signals to the vestibular cortex in temporal lobe
via cn8
What is the role of the glossopharyngeal nerve CN9?
sensory - pharynx, auditory tube + middle ear, posterior
3rd of tongue, aortic BP changes
motor - swallowing
parasympathetic - salivary glands
Outline the functions of the vagus nerve CN10
vasovagal response mediated by vagus nerve
sensory - sensation of pain associated with viscera
motor - muscles for speech and swallowing
parasympathetic - smooth muscle in heart, lungs + abdominal organs
What is the function of the accessory nerve?
motor info
cranial - muscles of the pharynx, larynx and soft palate
spinal - head + neck muscles
What is the role of the hypoglossal nerve CN11?
motor info
tongue movement for swallowing and speech
What is the meninges?
membranous coverings of the brain and spinal cord composed of 3 layers
What are the 3 membranes of the meninges?
Dura mater:
- Tough, in-elastic
Arachnoid Membrane
- Adheres layers together, anchors
Pia Mater:
- Thin membrane, adheres closely to the brain
What is in the subarachnoid space?
The sub arachnoid space is filled with cerebrospinal fluid (CSF)
Where is CSF formed?
CSF is made in the Choroid Plexus
How does CSF enter the subarachnoid spaces?
CSF flows from the cerebrum ventricles down to the brainstem and spinal cord
CSF enters the subarachnoid space via apertures near the cerebellum
What are apertures?
an opening, hole, or gap
What happens to the CSF in the subarachnoid space?
CSF is absorbed by blood vessels in the subarachnoid space
What is the role of CSF?
CSF protects the brain from physical and chemical injury
Regulates intracranial pressure
Essential in exchanging nutrients and waste products between the blood and the CNS
Describe the cerebrovasculature
Two pairs of arteries supply blood to the brain:
The vertebral arteries and the carotid arteries
Branches from the arteries supply blood throughout the brain
What is the circle of willis?
They also form an interconnected structure called the circle of Willis - vulnerable to stroke due to turbulent blood flow in this area
→ v. dangerous to have blood clot as will block blood supply to other brain regions
Which artery supplies the lateral cerebrum surface?
Most of the lateral surface of the cerebrum is supplied by the middle cerebral artery
What supplies the medial cerebral surface?
Most of the medial wall of the cerebral hemisphere is supplied by the anterior cerebral artery
What is the role of lymphatics in the brain?
Delivers immune cells to fight infection
What is the role of the occipital lobe?
Lies posteriorly
Involved in visual processing
e.g. colour, orientation, motion
What is the role of the parietal lobe?
Superiorly located
sensory processing and proprioception
What is the function of the frontal lobe?
Anterior portion of brain invloved in:
- decision making
- attention
- consciousness
- emotions
- deliberate movement
What is the role of the temporal lobe?
Lies laterally involved in language, speech and auditory processing
What is the corpus callosum?
A thick band of nerve fibres dividing cerebral cortex lobes into left and right hemispheres allowing info to be passed between them
What is the role of the hippocampus?
memory formation and retrieval
What is the function of basal ganglia?
collection of nuclei (SCN, STN etc.) in the diencephalon involved in movement, balance and posture
What is the thalamus?
Region within diencephalon with over 40 different nuclei
multi-modal functions
What is the role of the hypothalamus?
Collection of small nuclei regulating:
- temperature
- hunger/thirst
- neuroendocrine control
- circadian rhythms
- BP/HR
Outline the homeostatic functions of the brainstem
- breathing
- HR
- BP
What are the motor movements regulated via the brainstem?
Reflexes
Fine motor movements of limbs and face in conjunction with cortex
What is the role of the cerebellum?
movement precision and coordination
