Results for "substantia nigra"

Unit 10 – Drugs for Central Nervous System (CNS) Problems (Comprehensive Study Guide – Nursing Pharmacology) ⸻ 🧩 Central Nervous System (CNS) Overview • CNS = Brain + Spinal Cord • Controls body movement, behavior, and cognitive function. • Neurotransmitters are chemicals that transmit signals between neurons. • Excitatory: Acetylcholine (ACh), epinephrine, norepinephrine • Inhibitory: Dopamine, serotonin, gamma-aminobutyric acid (GABA) ⚖️ Balance of dopamine and acetylcholine is critical for smooth movement. An imbalance leads to disorders like Parkinson’s Disease. ⸻ 🧍‍♂️ Parkinson’s Disease (PD) Cause • Progressive CNS disorder due to low dopamine production in the substantia nigra. • Too little dopamine → too much acetylcholine, causing impaired motor control. Key Symptoms Motor: • Tremors (“pill-rolling”) • Bradykinesia (slow movements) • Muscle rigidity, stiffness • Stooped posture, shuffling gait • Difficulty rising, “freezing in place” • Masklike facial expression Nonmotor: • Constipation, urinary frequency • Depression, anxiety, hallucinations • Sleep issues, fatigue • Memory problems ⸻ Drug Classes for PD Goal: Restore balance between dopamine and acetylcholine. 1️⃣ Dopamine Agonists Action: Mimic or increase dopamine. Improve movement, coordination, and muscle control. Examples: • carbidopa/levodopa (Sinemet, Rytary) • pramipexole (Mirapex ER) • ropinirole (Requip) • rotigotine (Neupro patch) Nursing Implications & Teaching: • Give 30–60 min before meals (empty stomach). • Avoid protein-rich foods (reduces absorption). • Monitor for orthostatic hypotension — rise slowly. • Don’t crush extended-release tablets. • Neupro patch: rotate sites, don’t reuse within 14 days. • Avoid vitamin B6 unless taken with carbidopa. • Takes 2–3 weeks for full effect. Side Effects: • Hypotension, headache, nausea, insomnia • Dyskinesia (abnormal movements) • “On/off effect” – medication wears off quickly • Long-term use → hallucinations, impulse control problems Adverse Effects: • Neuroleptic malignant syndrome: fever, rigidity, confusion • Psychosis, severe hypotension ⸻ 2️⃣ COMT Inhibitors Action: Block COMT enzyme → prolong dopamine activity. Examples: • entacapone (Comtan) • tolcapone (Tasmar) Nursing Implications: • Always give with carbidopa/levodopa. • Monitor liver function (q6 months) – risk of liver failure (especially tolcapone). • Harmless side effect: brown-orange urine. • Rise slowly to prevent hypotension. ⸻ 3️⃣ MAO-B Inhibitors Action: Inhibit MAO-B enzyme → prevents dopamine breakdown. Examples: • selegiline (Eldepryl) • rasagiline (Azilect) • safinamide (Xadago) Teaching: • Avoid foods high in tyramine → hypertensive crisis risk. (Aged cheese, wine, beer, cured meats, soy sauce, yogurt, avocados, bananas) • Monitor BP closely. • Avoid OTC decongestants or stimulants. • Can cause insomnia, dizziness, dry mouth, or constipation. ⸻ 🧠 Alzheimer’s Disease (AD) Cause • Progressive neurodegenerative disorder leading to memory loss, confusion, and poor judgment. • Loss of acetylcholine (ACh) and buildup of amyloid plaques and neurofibrillary tangles in the brain. Symptoms • Early: forgetfulness, confusion, mood changes. • Late: loss of reasoning, personality changes, inability to perform ADLs. ⸻ Drug Classes for AD 1️⃣ Cholinesterase Inhibitors Action: Block enzyme acetylcholinesterase (AChE) → increases ACh → improves memory and function. Examples: • donepezil (Aricept) • rivastigmine (Exelon) • galantamine (Razadyne) Side Effects: • Nausea, vomiting, diarrhea • Loss of appetite, GI discomfort • Drowsiness, headache, insomnia • Muscle cramps, bradycardia Adverse Effects: • Dysrhythmias, GI bleeding, hallucinations • Overstimulation of parasympathetic system (too much ACh) Nursing Implications: • Give at bedtime to reduce nausea. • Monitor weight, HR, and mental changes. • Report black/tarry stools or vomiting blood. • Avoid OTC anticholinergics (they reduce effectiveness). ⸻ 2️⃣ NMDA Blockers Action: Block NMDA receptor → decreases glutamate activity → prevents neuron death. Example: • memantine (Namenda) Used in: Moderate to severe AD (often combined with donepezil). ⸻ ⚡ Epilepsy / Seizure Drugs (AEDs) Purpose Reduce excessive electrical activity in the brain and prevent seizures. Common AEDs: • phenytoin (Dilantin) – prevents neuron excitation • topiramate (Topamax) – broad-spectrum seizure control Topiramate Key Points: • Side effects: dizziness, drowsiness, taste changes, paresthesias (“pins and needles”) • Adverse: metabolic acidosis, ↑ ammonia → confusion, lethargy, vomiting • Monitor: serum bicarbonate & ammonia levels • Teaching: stay hydrated, report mental status changes, don’t crush tablets • Contraindicated in pregnancy (teratogenic) ⸻ 💥 Multiple Sclerosis (MS) Pathophysiology • Autoimmune disease where the immune system attacks myelin (fatty sheath around neurons). • Leads to nerve signal disruption → muscle weakness and loss of coordination. • Common type: Relapsing-Remitting MS (RRMS) – periods of flare-ups and remission. Common Symptoms • Fatigue, weakness, difficulty walking • Double vision or blurred vision • Tingling or numbness • Bladder/bowel dysfunction • Depression, poor concentration ⸻ Drug Therapy for MS 1️⃣ Biological Response Modifiers (BRMs) Action: Modify immune system activity and slow disease progression. Examples: • beta-interferons (Avonex, Betaseron, Rebif, Extavia, Plegridy) • glatiramer (Copaxone) • fingolimod (Gilenya) • teriflunomide (Aubagio) Side Effects: • Flu-like symptoms, headache, fatigue • Elevated liver enzymes, slow HR • Thinning scalp hair Nursing Teaching: • Rotate injection sites. • Monitor liver enzymes, CBC, and heart rate. • Avoid live vaccines. ⸻ 2️⃣ Monoclonal Antibodies Action: Destroy lymphocytes that attack myelin. Examples: • alemtuzumab (Lemtrada) • natalizumab (Tysabri) • ocrelizumab (Ocrevus) Side Effects: • Increased risk of infection • Headache, rash, fatigue • GI upset Nursing Teaching: • Given IV every few months to yearly. • Monitor for infusion reactions and infection signs. ⸻ 3️⃣ Neurologic Drugs Examples: • dimethyl fumarate (Tecfidera) – reduces CNS inflammation • dalfampridine (Ampyra) – improves walking by increasing nerve conduction Teaching: • Take daily; don’t crush tablets. • Watch for GI symptoms and dizziness. ⸻ 💪 Amyotrophic Lateral Sclerosis (ALS) Description • Progressive, fatal disorder destroying motor neurons → paralysis. • Death usually occurs within 3–5 years of diagnosis. Drug Therapy Glutamate Antagonists Example: • riluzole (Rilutek, Tiglutik) Action: Inhibits glutamate release → slows neuron damage → prolongs life by months. Side Effects: • Weakness, nausea, dizziness • Liver toxicity (↑ liver enzymes) • Neutropenia, anemia Nursing Implications: • Monitor liver enzymes before and during therapy. • Report jaundice or dark urine. • Take on an empty stomach (1 hr before or 2 hrs after meals). • Avoid alcohol. • Don’t breastfeed while on this med. ⸻ ⚙️ Myasthenia Gravis (MG) Description • Autoimmune disease destroying acetylcholine receptors at neuromuscular junction. • Causes muscle weakness and fatigue, especially in eyes, mouth, throat. Symptoms • Ptosis (drooping eyelids) • Difficulty chewing/swallowing • Weakness in arms, legs, or respiratory muscles • Worsens with activity, improves with rest ⸻ Drug Therapy Acetylcholinesterase Inhibitors Action: Prevent breakdown of acetylcholine → improves nerve–muscle communication. Example: • pyridostigmine (Mestinon) Dosage: Usually every 4–6 hours, depending on patient response. Side Effects: • Nausea, vomiting, abdominal cramps, diarrhea • Increased salivation, sweating • Bradycardia, hypotension Adverse: • Cholinergic crisis (too much medication): → extreme weakness, bradycardia, bronchospasm, respiratory arrest. Nursing Implications: • Use with caution in asthma, COPD, bradycardia. • Give doses at same time each day to maintain muscle strength. • Monitor for myasthenic vs. cholinergic crisis. • Give meds 30–45 min before meals to prevent aspiration. Patient Teaching: • Take missed dose ASAP (but skip if close to next dose). • Don’t double dose. • Avoid alcohol and sedatives. • Report muscle weakness or breathing difficulty. • Keep atropine available (antidote for cholinergic crisis)

Overview of the Nervous System II

EXTERNAL AND INTERNAL STRUCTURE OF THE BRAIN STEM DR A. A. NWAKANMA THE BRAINSTEM •The brainstem is made up of the medulla oblongata, pons and midbrain •It is stalklike in shape and connects the narrow spinal cord with the expanded forebrain •Occupies the posterior cranial fossa of the skull Loading… FUNCTIONS OF BRAINSTEM •It serves as a conduit for the ascending and descending tracts connecting the spinal cord to the different parts of the higher centers in the forebrain •It contains important reflex centers associated with the control of respiration and CVS. •It is also associated with the control of consciousness •It contains important nuclei of cranial nerves II through XII EXTERNAL FEATURES OF MEDULLA OBLONGATA • The medulla oblongata connects the pons superiorly with the SC inferiorly •The junction of the medulla and SC is at the origin of the anterior and posterior roots of the first cervical nerve which corresponds approximately to the level of the foramen magnum Loading… EXTERNAL FEATURES OF MEDULLA •The medulla oblongata is piriform in shape •It has a broad superior part – open part •And a lower closed part •The central canal of the SC continues upward into the lower half of the medulla •In the upper half of the medulla it expands as the cavity of the fourth ventricle EXTERNAL FEATURES OF MEDULLA •On the ant. Surface of the medulla is the anterior median fissure which is continous inferiorly with the ant. Median fissure of the SC •On each side of the median fissure is a swelling called the pyramid EXTERNAL FEATURES OF MEDULLA •The pyramids are composed of bundles of nerve fibers, corticospinal fibers which originate in large nerve cells in the precentral gyrus of the cerebral cortex •The pyramids tapers inferiorly and majority of the descending fibers cross over to the opposite side forming the decussation of the pyramids here •The ant. External arcuate fibers are a few nerve fibers that emerge from the ant. Median fissure above the decussation and pass laterally over the medulla oblongata to enter the cerebellum EXTERNAL FEATURES OF MEDULLA •Posterolateral to the pyramids are the OLIVES which are oval elevations produced by the underlying inf. Olivary nuclei •In the groove b/w the pyramid and olive emerges the rootlets of the hypoglossal nerve •Post. To the olives are the inf. Cerebellar peduncles which connect the medulla to the cerebellum EXTERNAL FEATURES OF MEDULLA •In the groove b/w the olive and the inf. Cerebellar peduncle emerges the roots of the glossopharyngeal and vagus nerves and the cranial roots of accessory nerve •The post. Surface of the sup. Half of the medulla forms the lower part of the floor of the 4th ventricle External features of medulla •The post surface of the inf. Half continues with the post. Aspect of the SC and possesses a post. Median sulcus •On each side of the median sulcus is an elongated swelling , the Gracile tubercle produced by the underlying gracile nu. •Lat. To the gracile tubercle is the cuneate tubercle produced by the underlying cuneate nu. Loading… INTERNAL STRUCTURE OF MEDULLA •The internal structure of the medulla oblongata is usually considered at 3 levels •Level of pyramidal decussation •Level of olive •Level of sensory or lemniscal decussation T/S OF MEDULLA AT THE LEVEL OF OLIVE •This level corresponds to the floor of the 4th ventricle and the cranial n. Nuclei seen include •Hypoglossal n. • Vestibular nuclei •Dorsal nu. Of vagus •Solitary tract and its nu. •Nu. Ambigus • dorsal and ventral cochlear nu. T/S OF MEDULLA AT THE LEVEL OF OLIVE •The other masses of gray matter seen at this level include •The medial and dorsal accessory olivary nu. •Lat. Reticular nu. •Arcuate nu. •The descending tracts seen include •Pyramid •Rubrospinal tract •Spinal nu. And •Tract of trigeminal n. T/S OF MEDULLA AT THE LEVEL OF OLIVE •The ascending tracts include •Medial lemniscus lying in the middle and is L shaped •Spinothalamic T •Spinocerbellar T. •Spinotectal T. •The reticular formation and the inf. Olivary nu. Are also prominent features found at this level T/S OF THE MEDULLA AT THE LEVEL OF LEMNISCAL DECUSSATION •The level represented by this section lies a little above the level of the pyramidal decussation •The structures found at this level include •Central canal surrounded by gray matter •Medial lemniscus •The pyramids the nu. And fasciculus cuneatus •Spinal nu. Of trigeminal n. •The reticular formation T/S OF THE MEDULLA AT THE LEVEL OF LEMNISCAL DECUSSATION •Internal arcuate fibers which arise from the nu. Gracilis and cuneatus and arch forward on the medial side of the gray matter crossing in the midline to form the lemniscal or sensory decussation •Accessory cuneate nu. Lying dorsolateral to the cuneate nu. T/S OF THE MEDULLA AT THE LEVEL OF LEMNISCAL DECUSSATION •The cranial nerve nuclei seen at this level include •Hypoglossal nu. •Dorsal motor nu. Of vagus •Arcuate nu. •Nu. Of solitary tract •Nu. Ambigus •Other structures include •Lower part of inf. Olivary nu. •Lat. Reticular nu. •Arcuate nu. •Lat. & ventral spinothalamic tr. •Doral and ventral spinocerebella tr. •Spino-olivary tr. •Pyramids •Vestibulospinal tr. •Corticospinal tr. •Medial longitudinal fasciculus Connections of the Inferior Olivary Complex • The main afferents of the inferior olivary nucleus are from the cerebral cortex and from the spinal cord • The main efferents are to the cerebellar cortex. • An olivospinal tract is traditionally described, but some authorities hold that the inferior olivary nuclei do not send any fibres to the spinal cord. •The nucleus may be regarded as a relay station on the cortico-olivo-cerebellar and spino-olivo-cerebellar pathways. • The accessory olivary nuclei are connected to the cerebellum by parolivo-cerebellar fibres. THE PONS •The pons is the middle part of the brainstem •Its continuous below with the medulla oblongata and above with the midbrain •It is seperated from the cerbellum by the 4th ventricle •Pons has two surfaces: •Ventral and dorsal External Features Of Ventral Surface Of Pons •The ventral surface of pons shows the following features •The ventral surface is convex and has a shallow groove in the midline called the basilar groove which lodges basillar artery •Transvesely running fibers connecting the pons to the cerebellum thru the middle cerebellar peduncle •The two roots of trigeminal nerve (sensory and motor) emerge at the jxn b/w the ventral surface of pons and middle cerebellar peduncle EXTERNAL FEATURES OF DORSAL PONS •The dorsal surface of pons shows the following features •Median sulcus in the median plane •Medial eminence – shows rounded elevation in the lower part called facial colliculus which overlies the nu. Of abducent n. •Sulcus limitans – is lat. To the medial eminence and seperates medial eminence from vestibular area T/S THROUGH CAUDAL PART OF PONS •The features seen at this level include •Medial lemniscus in the most ant. Part of the tegmentum •The facial nu. Lies post to the lat. Part of the medial lemniscus •The fibers of the facial nerve wind around the nu. Of the abducent nerve producing the facial colliculus T/S THROUGH CAUDAL PART OF PONS •The medial longitudinal fasciculus is situated beneath the floor of the 4th ventricle on either side of the midline •The medial longitudinal fasciculus is the main pathway that connects the vestibular and cochlear nuclei with the nuclei controlling the extraocular muscles (oculomotor, trochlear and abducent) •The medial vestibular nu. Is situated lat. To the abducent nu. And in close relationship to the inf. Cerebellar peduncle T/S THROUGH CAUDAL PART OF PONS •The sup. Part of the lat. And inf. Part of sup. Vestibular nu. Are found at this level •Post. And ant. Cochlear nu. Are also found at this level •The spinal nu.of trigeminal nerve and tract lie on the anteromedial aspect of the inf. Cerebellar peduncle T/S THROUGH CAUDAL PART OF PONS •The trapezoid body is made up of fibers derived from the cochlear nuclei and the nuclei of trapezoid body •They run transversely in the ant. Part of the tegmentum •The basilar part of the pons at this level contain masses of nervr cells called pontine nuclei T/S THROUGH CAUDAL PART OF PONS •The axons of these cells give origin to the transverse fibers of the pons which cross the midline and intersect the corticospinal and corticonuclear tracts breaking them up into small bundles Loading… INTERNAL STRUCTURE OF CRANIAL PART OF PONS •The internal structure of the cranial part of pons is similar to that seen at the caudal level but contains the motor and principal sensory nuclei of the trigeminal nerve •The motor nu. Of the trigeminal nerve is situated beneath the lat. Part of the 4th ventricle within the reticular formation INTERNAL STRUCTURE OF CRANIAL PART OF PONS •The principal sensory nu. Of the trigeminal nerve is situated lateral to the motor nu. •The sup. Cerebellar peduncle is situated posterolat. To the motor nu. Of trigeminal nerve EXTERNAL FEATURES OF MIDBRAIN •Midbrain measures about 2cm in length and connects the pons and cerebellum with the forebrain •The midbrain is traversed by a narrow channel – the cerebral aqueduct ( which is filled with CSF) •On the posterior surface are four rounded eminences that are divided into superior and inferior pairs •The sup. Colliculi are centers for visual reflexes while the inf. Are lower auditory centers •In the midline below the inf. Colliculi emerges the trochlear nerves EXTERNAL FEATURES OF MIDBRAIN •Each colliculi is related to a ridge called brachium •The sup. Brachium passes from the sup. Colliculus to the lat. Geniculate body and the optic tract •The inf. brachium connects the inf colliculus to the medial geniculate body EXTERNAL FEATURES OF MIDBRAIN •On the anterior aspect of the midbrain is a deep depression in the midline called the interpeduncular fossa which is bounded on either side by the crus cerebri •Many blood vessels perforate the floor of the interpeduncular fossa and this region is termed the post. Perforated substance INTERNAL STRUCTURE OF MIDBRAIN •The midbrain is divided into two parts – •An upper tectum and •A lower part called cerebral peduncles •The upper part (tectum) contains mainly the colliculi of the two sides and represents the dorsal part of the midbrain •The cerebral peduncles are subdivided by the substantia nigra into •The tegmentum and •Crus cerebri STRUCTURE OF MIDBRAIN AT OF INF. COLLICULUS •The structures seen at this level include •Crus cerebri- this contain descending fibers from different parts of the cerebral cortex •The medial 1/6 contain frontopontine fibers •The intemediate 2/3 contain corticospinal and corticonuclear fibers •The lat. 1/6 contain temporopontine fibers •Other structures include •Substantia nigra •Cerebral aqueduct : this is surrounded by the central gray matter. •Ventral to this aqueduct is the oculomotor and trochlear nerves STRUCTURE OF MIDBRAIN AT OF INF. COLLICULUS •Reticular formation b/w the substantia nigra and gray matter •Inferior colliculus •Mesocephalic nu. Of trigeminal nerve •Compact bundle of fibers lies in the tegmentum dorsomedial to the substantia nigra •This bundle consistsof the medial lemniscus, trigeminal lemniscus and spinal lemniscus •Medial longitudinal fasciculus •Superior cerebellar peduncle •Rubrospinal tract Structure of midbrain at the level of sup. colliculus •The following structures are seen at this level •Sup. Colliculus in the tectum •Red nu. In the tegmentum dorsomedial to the substantia nigra •Oculomotor nuclei near the central gray matter •Bundles of ascending fibers consisting of medial lemniscus, spinal lemniscus and trigeminal lemniscus Structure of midbrain at the level of sup. colliculus •Dorsal tegmental decussation : this consists of fibers originating in the sup. Colliculus, it crosses to the opp. Side and descend as the tectospinal tract •Ventral tegmental decussation : this originates in the red nu

The Midbrain / Mesencephalon