Neuro 12 PDF

Neuro 12 The mammalian brain Recall, NS is three interconnected systems = CNS, PNS, ANS CNS = brain, SC - Recall structures (tracts, ganglia, roots) are associated with specific functions and regions (somatotopic relationships). This implies that when a lesion/problem is in a spe...

Neuro 12 The mammalian brain Recall, NS is three interconnected systems = CNS, PNS, ANS CNS = brain, SC - Recall structures (tracts, ganglia, roots) are associated with specific functions and regions (somatotopic relationships). This implies that when a lesion/problem is in a specific location, you will observe a specific set of signs associated with the loss of those functions. Organization of the brain In physio we divide brain into 3 functional structures instead: 1. Thalmocortex: cortex and thalamus 2. Cerebellum: anatomical and functional 3. Brainstem: midbrian. Pons. medulla Cortex/telencephalon - Most anterior region, usually associated with advanced functions - Part of forebrain  - Can be divided into three 1. Cerebral cortex: gray matter is external (folding pattern of telencephalon during development) - several different lobes 2. Rhinencephalon - olfactory portion and limbic system 3. Basal nuclei (ganglia) 1) The cerebral cortex (gray matter regions) - Several different lobes - Part of the cortex/telencephalon - Gray matter on the outside! - Folded in to gyri (outward fold) or sulci (inward folds), except for rodents and birds! - Each gyrus and sulcus has a name - 2 hemispheres: 1 on each side - 5 lobes - piriform/olfactory lobe internally folded: medial to temporal lobe - Right hemisphere receives information from left side of the body and vice versa - A lot of decussation at brain, so if you have processing on the left temporal lobe, manifested from a stimulus on the right side of the body 1. Frontal lobe - sensory (caudal part), behaviour (rostral part), voluntary movement, learning 2. Parietal lobe: sensory and association (relationship between incoming physical sensory info and what else is going on with the animal) 3. Temporal lobe: - Audition, equilibrium, association auditory and balance, gets auditory info and balance and association with position, and integrates it 4. Occipital lobe: visual cortex, association vision 5. Piriform/olfactory lobe: - Olfaction, learning, memory, emotions (emotional response) White matter of the cerebral cortex - Contains axons covered with myelin (myelin made by oligodendrocytes) - Connects neurons within same hemispheres → association fibres e.g. corona radiata - Connects cortex to brainstem → projection fibres e.g. optic radiations - Connects hemispheres together → commissural fibres e.g. corpus callosum and rostral commissure 2) The rhinencephalon - Generating olfactory info - Olfactory portion consists of: - olfactory nerve (CN 1), olfactory bulb, olfactory peduncles, entorhinal cortex (piriform lobe)  - Also includes other regions include the limbic system’s Amygdala, septum, hippocampus Connected to the cortex (by the cingulate gyrus), thalamus, and hypothalamus = controls emotions and behaviour Like fear, rage Well described in primates, not really in domestic animals 3) Basal Nuclei - Gray matter nuclei - Concentration of nerve cell bodies - Subcortical collection of gray matter 1. caudate nucleus 2. Putamen 3. globus pallidus 4. claustrum - Function: modulate voluntary movement signals from cortex, important in motor function - More so in people not animals Thalamus - Part of the diencephalon - Also in fore brain - Makes up thalamocortex with the cortex/aka telencephalon - Relay station, AP arrive and consciously be recognized, cortex enhances this function (prof lecture notes) - Composed of several bilateral nuclei (groups of neurons) 1. Lateral Geniculate Nuclei (vision)- one on each side so two all together 2. Medial Geniculate Nuclei (audition) - Receives all sensory info (except olfaction) and projects to specific area of cortex - Clinically linked with cerebral cortex - Gets feedback from cortex and basal nuclei - Some motor function: cranial part of red nucleus (paired) resides in the thalamus (og of rubrospinal tract) - Pain stimuli recognized here (Spinothalamic tract) Thalamocortex - Because cortex and thalamus have many integrated and overlapping functions, neurological lesions and injuries in these areas can have similar presentations. Lesion signs include 1. Seizures 2. behavioural changes 3. motor problems  4. circling in one direction 5. change in gait? Recall red nucleus, basal nuclei… 6. Decrease learning, balance, hearing, vision, olfaction? - Signs of a thalamocortex lesion Hypothalamus - Part of diencephalon but not part of thalamocortex - Regulate nervous and endocrine system - Neurons in hypothalamus that participate in → heart rate, BP, body temp, water balance, food intake, circadian rhythms, emotions… - Receives and sends connection to thalamus, limbic system, ANS - Grouped into several nuclei with specific functions - Controls endocrine secretions of neurohypophysis and adenohypophysis (of the pituitary gland) It secretes NT into blood vessel itself, not a synpatic cleft, at neurohypophusis - Direct secretion of peptides: oxytocin and vasopressin at the neurohypophysis to the bloodstream and acts as hormones It secretes releasing hormones that triggers secretion of other hormones from adenohypophysis: - Hypothalamus also secretes releasing hormones that trigger secretion of hormones of adenohypophysis - Long axons, stimulated, AP cause a release of the RH, interact with cells of the adenohypophysis and causes them to release a second type of hormone → bloodstream → travels to a gland Lesion? - No release of oxy and vaso? - No release of RH? → decreased secretion of T3/T4, glucocorticoids, minderalcorticoids, androgens, decreased production of gametes and secretion of sex steroid, decreased milk production, decreased anabolism and decrease organ growth Pineal gland - Part of diencephalon - Located dorsally to thalamus - NOT pituitary gland - Circadian rhythms - Regulates day/night cycle through release of melatonin - Melatonin is processed from serotonin with light stimulus, thus modified NT - Sleepiness - Antigonadotropic effect → suppresses the effects of sex hormones and release hormones. Lesion - Too many sex hormones? - Changes in day/light cycle? Midbrain (mesencephalon) Note, brainstem = the midbrain, pons, and medulla oblongata Sensory portion: colliculi - Rostral colliculi = visual reflexes processing - Caudal = auditory reflexes processing - Head, neck, eye movement - Receive visual and auditory signals/ visual (rostral) and auditory (caudal) reflexes - Medicate movement of the head in response to light and sound - pretectal nuclei live here for end of cn ii - Motor nucleus of CN IV trochlear nerve lives here Motor portion - Contraction of iris muscle, Aka contraction of pupils due to the oculomotor nerve CN III’s EW nucleus is here! - Movement of the eye: oculomotor and trochlear nerves (CN IV)  → also abducens nerve (CN VI) from medulla - Part of gait (caudal part of Red Nucleus - og of rubrospinal tract) Lesion at midbrain? - Expect many or all of functions to be compromised - No contraction of pupils cuz EW nucleus lives here - No movement of eye - Gait weird cuz ½ red nucleus of the rubrospinal tract lives here Pons (metencephalon) - Gives rise to trigeminal nerve (CN V) → some sensory nuclei for facial sensation, comes in → some motor nuclei give rise to neurons for masticatory muscles movement/contraction, jaw closure - Communicates with cerebellum (regulation of movement) - Some nuclei that participate in resp control - Centres of integration/control of micturition - Part of hindbrain and brainstem Lesion? - Loss of facial sensation - Loos of masticatory muscle movement - Loss of jaw closure - Loss of resp control - Loss of micturition - Regulation of movement damaged Medulla oblongata (myelencephalon) - Controls basal aspects of life - Contains nuclei of cranial nerves VI to XII - Relays sensory info from SC e.g. proprioceptive tracts will end here e.g., tactile, temp, pain - Relays motor motor info from cortex and brainstem - Ascending Reticular Activating System (see reticular formation) involved in maintaining state of consciousness - Cardiovascular and Respiratory functions - How “awake” will be - Lots of traffic Lesions? - Leads to death - Cardiovascular and respiration stops - Proprioceptive damage - Loss of consciousness Reticular formation in brainstem - Complex network of neurons - In brainstem - Present in all parts of the brainstem: medulla, pons, midbrain (+thalamus) - Receives sensory signal form entire nervous system - Projects to cortex via thalamus - Not a single structure - Amount of activity here = determines state of arousal or awareness of the animal - Why its difficult to fall asleep after playing a sport= heightened state of consciousness → Ascending Reticular activating system (ARAS) - Sends continuous flow of impulse to cerebral cortex: awakening - State of consciousness - Responsible for level of arousal - Lesion of ARAS (aka lesion at brainstem) will see → lethargy, obtundation, stupor, coma, decrease state of consciousness Could be at cortex but most likely here ARAS (series of impulses up to cortex to dictate awakening) vs reticular formation (network) → other functions of Reticular formation - Participates in locomotion and muscle tone thus output, where the reticulospinal tract og - Lies at the distal end of the pain tract - True pain: via poorly defined tracts (spinoreticular) in SC → If an animal is experiencing in a high level of pain, it activates the reticular formation - Reflex processes: vomiting, swallowing, sneezing… - Linked to ANS: micturition, defecation, respiration and heart rate modulation Lesion - No pain? - Loss of muscle tone - Loss of locomotion - No vomiting, swallowing, sneezing - Loss of micturition, defecation, respiration and heart rate modulation  Brainstem - Because the midbrain, pons and medulla oblongata are anatomically continuous, have many related functions (basic control of life-supporting activities) and are associated through the reticular formation, they are often collectively called the brainstem and are functionally considered to be one of the three regions of the brain (cerebrum, cerebellum and brainstem) Brainstem: respiration - Specific nuclei in the medulla and pons (aka brainstem parts) are integrated with each other to control inspiration, expiration, breath holding in response to changes in physiological demand - Lesion here? Can’t resume breathing on their own Brainstem: cardiovascular regulation - Part of the ANS - Houses cardiac control and blood pressure regulation! - Cardiac accelerator center (sympathetic): increase heart rate (chronotrope +) and contraction strength (inotrope+) - Cardiac inhibitory center (PARA) through vagal nerve, chronotrope and inotrope - - Vasomotor center: regulate BP → gets info from baroreceptors, carotid sinus (CN IX) and aortic arch (CN X) - Lesion at brainstem? Cardiovascular problems, irregularities of HR Lesion at brainstem - Cardiac, resp failure - Loss of BP regulation Cerebellum - From latin = “little brain” - Part of hindbrain - Compares intended movement to actual muscle activity → Corrects any disparity and Smoothens movement - Spinocerebellar tracts end here! Senses what the limbs are do, modulated output to be smooth - Interacts with vestibular system → Important for balance Physio - Receives info form cortex  → intended movement - At same time, receives from SC → actual movement - Comparison…integrates both - Sends back correction to cortex so subsequent AP is closer to intentende output - All through cerebellar peduncles Anatomy - No large folds. Smaller and more freq folds and ridges - Cortex, cerebellar nuclei, nodular lob - Two lateral hemispheres and a medial vermis Lesion at cerebellum? Animal is able to output movement, but won't be able to do it smoothly = Ataxia, tremors, over steps Ataxia as a sign of lesions in the CNS: different types of ataxia - Ataxia is defined as an inability of an animal to coordinate the activity of its limbs, trunk and/or head in space it moves. 3 distinct types are recognized clinically. It is a sensory (not a motor sign cuz it can still walk just not smoothly!) 1. Proprioceptive/spinal ataxia: SC or brainstem injury to tracts. Recall proprioceptive tracts. 2. Vestibular Ataxia: damage to vestibular system (brainstem, inner ear) 3. Cerebellar Ataxia: Cerebellum injury/lesions Summary of lesions in the brain: narrow down to Thalamocortex, brainstem or cerebellum