The Brain and Cranial Nerves Flashcards
4 brain regions
- Cerebrum
- Cerebellum
- Dicenephalon
- Brainstem
Cerebrum
- Largest portion
- Conscious thoughts, sensations, intellect, memory and complex movement
Cerebral hemispheres
Large left and right hemisphere
Surface covered by collection of neurons that form a thin superficial layer of gray matter called cerebral cortex
Cerebral cortex form elevations called gyri
Gyri separated by
Shallow grooves called sulci
Deeper grooves called fissures
Cerebellum
- Second largest, partially hidden by cerebral hemispheres
- Covered by a sheet of gray matter called the cerebellar cortex
- Adjust ongoing movement by comparing arriving sensations with previously experienced sensations
Diencephalon
Thalamus: relay and processing centres for sensory information
Hypothalamus: contains centres involved with emotions, autonomic function and hormone production
Infundibulum: connects hypothalamus to the pituitary gland
Brainstem
- Contains a variety of important processing centres and nuclei that relay information headed to or from the cerebrum or cerebellum
- Midbrain, pons, medulla oblongata
Midbrain
Contains nuclei that process visual and auditory information and control reflexes triggered by these stimuli e.g. reflexes to loud noises
Pons
- The brain connects the cerebellum to the brainstem
- Tracts, relay centres and somatic and visceral motor control
Medulla oblongata
- Connects the brain to the spinal cord
- Central canal
- Relays sensory information to the thalamus and to centres in other portions of the brainstem
- Controls autonomic functions e.g. heart rate
Primary brain vesicles
- 3 weeks
- Three swellings in the neural tube: forebrain, midbrain and hindbrain
Secondary brain vesicles
- 6 weeks
- Telencephaon, diencephalon, mesencephalon, metencephalon, myelencephalon
Brain regions at birth
Cerebrum, diencephalon, midbrain, cerebellum and pons, medulla oblongata
Ventricles
During development, neural tubes form chambers called ventricles
Lateral ventricles, third ventricle, cerebral aqueduct, fourth ventricle
Contain CSF
Cranial meninges
Continuous with spinal meninges (dura mater, arachnoid mater, pia mater)
Dura mater
- Outer and inner fibrous layers
Dural folds
Inward projections that provide additional stabilisation and support to the brain
Dural venous sinuses
Large collecting veins located within dural folds
Veins of the brain open into these sinuses
Largest dural folds
Falx cerebri: superior and inferior sagittal sinus lie within falx cerbri
Tentorium cerebelli: protects the cerebellum and seperates it from cerebral hemispheres
Falx cerebelli: divides two cerebral hemispheres
Subdural space
Separates dura mater from arachnoid mater as a result of disease or trauma
Arachnoid mater
Covers brain with a smooth surface, doesn’t follow brain’s underlying folds
Subarachnoid space
Contains cells and fibres of the arachnoid trabeculae
Lies between the arachnoid mater and the pia mater
Pia mater
Sticks closely to the surface of the brain
Functions of CSF
Supporting the brain
Cushioning neural structures
Transporting nutrients, chemical messengers, and wastes
Choroid plexus
An area within each ventricle that produces CSF
CSF
Filtrate produced by the fluid leaking out of capillaries in the choroid plexuses. Ependymal cells then secrete CSF into ventricles
Epidural hemorrhage
When blood is forced between dura mater and skull
Subdural hemorrhage
Bleeding between dura mater and arachnoid mater
CSF production
- Produced at choroid plexuses
- Reaches subarachnoid space through later and median aperture
- Diffuses across arachnoid granulations
- Goes into superior sagittal sinus
Blood brain barrier
Isolates nervous tissue from general circulation
Where is the BBB incomplete?
In parts of the hypothalamus, pituitary gland, pineal gland and choroid plexus
Cerebrovascular diseases
Cardiovascular disorders that interfere with normal blood supply to brain`
Cerebrovascular accident
Stroke
Occurs when blood supply to portions of the brain is shut off
Why don’t substances have free access to the CNS?
Because specialised ependymal cells create a blood CSF barrier
Relay stations of the medulla oblongata
Olivary nuclei
Reflex centres inc. cardiovascular, respiratory rhythmicity centre
Reticular formation
Begins in the medulla oblongata and extends into more superior portions of the brainstem
Pons
Contains
- Sensory and motor nuclei for four cranial nerves
- Nuclei that help control respiration
- Nuclei and tracts linking the cerebellum with the brainstem, cerebrum, and spinal cord
- Ascending, descending and transverse tracts
Tectum
Roof of the midbrain
Contains corpora quadrigemina (superior and inferior colliculi)
Tegmentum
Contains red nucleus, substantia nigra, cerebral peduncles and headquarters of the reticular activating system (RAS)
Cerebellum
Adjusts postural muscles and programs and tunes ongoing movements
2 cerebral hemispheres consist of anterior and posterior lobes, vermis and flocculonodular lobe
Superior, middle and inferior cerebellar peduncles
Link the cerebellum with the brainstem, diencephalon, cerebrum, and spinal cord and connect the two cerebral hemispheres
Diencephalon
Composed of the epithalamus, thalamus, and hypothalamus
Thalamus
Final relay point for ascending sensory information and coordinates the activities of the basal nuclei and cerebral cortex
Hypothalamus
- Secretes certain hormones
- Regulate body temperature
- Control autonomic function
- Coordinate voluntary and autonomic function
- Coordinate activities of the nervous and endocrine systems
- Regulate circadian cycles of activity
- Control skeletal muscle contractions at the subconscious level
- Produce emotions and behavioural drives
Limbic system
Amygdaloid body, cingulate gyrus, denate gyrus, parahippocampal gyrus, hippocampus, fornix
Emotional states, behavioural drives and memory
White matter of cerebrum
Association fibres, commissural fibres and projection fibres
Basal nuclei
Caudate nucleus, globus pallidus, and putamen
Control muscle tone, coordinate learned movement patterns and other somatic motor activites
Primary motor cortex of the precentral gyrus
Directs voluntary movement
Primary somatosensory cortex of the postcentral gyrus
Receives somatic sensory information from touch, pressure, pain, vibration, taste, and temperature receptors
Association areas
Somatic sensory association, visual association area, premotor cortex
Control our ability to understand sensory information and coordinate a motor response
Specialised language areas of the brain
Receive information from all the sensory association areas. It is usually dominant in only one hemisphere - generally the left
Prefrontal cortex
Coordinates information from the secondary and special association areas of the entire cortex and performs abstract intellectual functions
Broca’s area and Wernicke’s area
- Left hemisphere
- Responsible for language-based skill
Right hemisphere
Typically responsible for spatial relationship and analyses
Electrocephalogram
- Alpha waves appear in healthy resting adults
- Beta waves occur when adults are concentrating
- Theta waves appear in children
- Delta waves are normal during sleep
Cranial nerves
- 12 pairs
- Each nerve attaches to ventrolateral surface of the brain stem near associated sensory or motor nuclei
- Except for CN I and CN II
Olfactory nerves (I)
- Carry sensory information responsible for the sense of smell
- Olfactory afferents synapse within olfactory bulbs
Optic nerves (II)
Carry visual information from special sensory receptors in the eye
Oculomotor nerves (III)
Primary source of innervation for four extrinsic eye muscles
Trochlear nerves (IV)
- Smallest cranial nerves
- Innervate superior oblique muscles of the eye
Trigeminal nerves (V)
- Largest cranial nerves are mixed nerves with three divisions: opthalmic nerve, maxillary nerve, mandibular nerve
Abducens nerves (VI)
- Innervate lateral rectus muscles of the eyes
Facial nerves (VII)
- Mixed nerves that control muscles of the scalp and face
- Provide pressure sensations over the face and receive taste information from the tongue
Vestibulochoclear nerves (VIII)
- Contains vestibular nerve which monitors sensations of balance, position and movement
- Contains cochlear nerve monitors hearing receptors
Glossopharyngeal nerves (IX)
Mixed nerves that innervate the tongue and pharynx and control the action of swallowing
Vagus nerves (X)
Mixed nerves that are vital to the autonomic control of visceral function int he thorax and abdomen
Accessory nerves (XI)
- Have internal branches which innervate voluntary swallowing muscles of the soft palate and pharynx
- Have external branches which control muscles associated with pectoral girdle
Hypoglossal nerves (XII)
Provide voluntary motor control over tongue movements
Cranial reflexes
Monosynaptic and polysynaptic reflex arcs that involve sensor and motor fibres of the cranial nerves
