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BIOD 331 Module 6 (Complete Solution)
(Organization & Function of Nervous System I
I. Nervous System Overview ● Acts as the control center, receiving sensory input, integrating information, and producing responses. ○ SENSATION (Sensory receptor) sensory neurons →INTEGRATION (percept) Motor neurons → REACTION (effectors - skeletal muscle, heart muscle as an example) ● Divided into: ○ Central NS (brain + spinal cord); vital organs, cant be regenerated, so encased in meninges, membranes and skeleton → integration and processing. ■ Brain can be subdivided into 3 regions: ● The hindbrain ● The midbrain ● The forebrain ○ Peripheral NS (nerves outside CNS); sensory receptors, cranial nerves, spinal nerves → carries info to/from CNS. ■ Autonomic division - involuntary - innervating internal organs - glands and smooth muscles ● sympathetic nervous system SNS - activates and prepares body for vigorous muscular, activity, stress, and emergencies ● parasympathetic nervous system PNS - normal resting situations, permitting digestions and conservation of energy ■ Somatic division - voluntary - skeletal muscles, skin and joints II. Central Nervous System ● HINDBRAIN: Affected by sleep disorders and cerebrovascular accidents (CVAs). ○ Cerebellum (coordination, posture, balance), Pons, Medulla (vital functions like respiration/HR ). ● MIDBRAIN: the tracts are main motor nerve pathway - area regulates eye movement, visual and auditory processing ○ Cerebral peduncles, bundle of nerve fibers that make up the corticospinal tracts.
● FOREBRAIN: most rostral part of brain (towards nose) ○ diencephalon (thalamus and subthalamus, hypothalamus) ○ cerebral hemispheres (lobes) connected via corpus callosum ■ Frontal: motor control, planning, judgment. ■ Parietal: sensory input. ■ Temporal: auditory processing, memory. ■ Occipital: vision. ● Basal ganglia: masses of white matter located deep to the cerebral cortex ○ Unlearned postural movements, smooth movements; dysfunction = Parkinson’s. ● Limbic system: located toward the medial aspect of the cerebrum ○ emotion ; stimulation in this area = pleasure, anxiety, rage, etc III. Spinal Cord ● Extends skull → L1/L2; continues as cauda equina which are ventral and dorsal nerve roots that extend beyond the cord itself. ● Oval in shape ● Tissue divisions: ○ Gray matter: butterfly shape, contains cell bodies of neurons. Extensions are horns. ■ Dorsal horn: sensory input (afferent) - from periphery ● Posteriorly within the cord, they receive sensory info by way of afferent neurons from periphery to be transmitted and interpreted ■ Ventral horn: motor output (efferent) - to periphery ● Contain different efferent neurons which carry motor info from CNS to periphery ○ White matter: myelinated tracts (ascending sensory, descending motor). IV. Protective Systems ● Meninges: connective tissue sheaths that surround the brain and spinal cord
- XII Hypoglossal Voluntary TONGUE movements Sample exam questions for this section
- Lateral eye movement issues - Cranial nerve VI
- Voluntary tongue movements which cranial nerve - Cranial nerve XII
- Each of the following are true regarding org of nervous system EXCEPT (pick out FALSE statement) a. The PNS has an afferent and efferent division (true) b. The somatic nervous system can be further divided into the sympathetic and parasympathetic divisions (false - autonomic nervous system is divided into sympathetic and parasympathetic nervous system c. The CNS contains the hindbrain, midbrain, and forebrain (true) d. The PNS contains the cranial nerves (true)
- Each of the following statements is true regarding the organization of the nervous system EXCEPT, select ALL that apply: a. CNS has an efferent and afferent division (false - PNS) b. The autonomic nervous system can be divided further into the sympathetic and parasympathetic divisions (true) c. The CNS contains cranial nerves (false) d. The PNS contains spinal nerves (true)
- Efferent neurons deliver ___input from CNS to the periphery Answer: Motor
- ___neurons delivery sensory input from periphery to CNS Answer: Afferent
- The _____houses the cerebral peduncles Answer: Midbrain
- Specialized ependymal cells that project into the ventricles and produce CSF are called
Answer: Choroid Plexus
- Connective tissue that sheaths that surround the brain and spinal cord providing protection are called the ____ Answer: Meninges
Module 6.2 — Organization & Function of Nervous System
II
I. Neurons - functional cells of nervous system ● Cell Body = Soma: nucleus, protein synthesis. ● Dendrites: branching extensions of soma; receive signals and move them to soma. Synaptic terminals that facilitate communication with axon and dendrites of other neurons. ● Axon: efferent projections of cell body. Most neurons within the body have only 1 axon, some axons may have branches resulting in multiple axon terminals. conducts impulses → synapse. ○ Larger diameter axons = conduct impulses at a higher rate of speed ○ Smaller diameter axons = conduct impulses at a slower rate of speed ● Afferent = sensory, Efferent = motor, Interneurons = connectors. II. Neuroglial Cells - provide protection and metabolic support t o the neurons of the CNS and the PNS ● CNS: ○ oligodendrocytes - make MYELIN in CNS ○ astrocytes - most abundant ; BBB, ion and NT regulation; repair ○ microglia - act as phagocytes - immune + cleanup ○ ependymal (line ventricles, CSF) ● PNS: ○ schwann - make MYELIN in PNS ■ Separated by extracellular fluid gaps called Nodes of Ranvier and are absent of myelin and contain a high concentration of voltage-gated sodium channels. ○ satellite - protect nerve cell bodies in ganglia; regulate exchange of molecules with surrounding tissue III. Myelin & Nodes of Ranvier ● Myelin - gives rise to “white matter”; speeds conduction. Dysfunctions - multiple sclerosis which slows or blocks nerve conduction and can lead to axon death if not repaired ● Nodes allow saltatory conduction (impulse jumps node-to-node).
● Receptors that NTs bind to are either excitatory or inhibitory. Receptors are named according to the NT they bind with (e.g. cholinergic receptors bind with NTs acetylcholine. ● Rapid removal of NTs once they have elicited effects is vital: ○ NTs can be broken down by enzymatic activity into inactive substances ○ NTs can be drawn back into the presynaptic neuron by a process known as reuptake ○ NTs can diffuse into the intercellular fluid until its concentration is too low to elicit a postsynaptic response ● Acetylcholine (ACh): muscle activation, parasympathetic. ● Dopamine: movement, reward (↓ in Parkinson’s). ● Serotonin: mood, sleep, appetite. ● Norepinephrine: alertness, sympathetic. ● GABA: inhibitory (↓ = seizures, anxiety). ● Glutamate: excitatory, learning/memory.
Sleep/Wake Basics
● Humans spend ~2/3 of the day awake (sensory input, motor responses, memory formation) and ~1/3 asleep (reduced consciousness, energy restoration, tissue repair, growth). ● EEG (electroencephalogram) - used to measure brain activity during sleep/wake cycles. Tracks brain activity through 4 wave patterns: ○ Sleep Stage 1 Alpha (8–13 Hz): Awake, eyes closed ○ Sleep Stage 2 Theta (4–7 Hz): Sleep (slow, high amplitude) diminished neuron firing ○ Sleep Stage 3&4 Delta (0.5–4 Hz): Sleep (slow, high amplitude) diminished neuron firing ○ REM Beta (>13–30 Hz): Awake, eyes open & REM sleep (high activity)
Stages of Sleep
A full cycle lasts 90 – 110 minutes and alternates between Non-Rapid Eye Movement NREM (80–85%) and Rapid Eye Movement REM (20–25%) sleep.
NREM Stages
- Stage 1 (Alpha → Theta): Light sleep, easily awakened, hypnic jerks, vital signs decrease
- Stage 2 (Theta + Sleep Spindles): Deeper sleep, memory consolidation.
- Stage 3 (Delta): Short deep sleep phase, body relaxes.
- Stage 4 (Delta): Deepest sleep (20–40 min), vital signs lowest.
REM Sleep
● Rapid eye movement, low muscle tone, vivid dreams. ● High brain activity, irregular breathing, increased HR/BP. ● Critical for psychological function —REM deprivation = anxiety, poor concentration, behavioral changes.
Breathing & Dreams
● Breathing: Irregular in light sleep & REM; regular in deep sleep. ● Dreams: Occur in all stages but especially Stage 1, 2, and REM. ○ REM dreams = emotional, linked to personal experiences. ○ Nightmares = more common in deep stages (3 & 4). ○ Possible role: memory processing and learning.
● Risk increases with age ● Impacts women more than men ● 6th leading cause of death in US ● Progressive neurodegeneration ● Major Features of Alzheimer’s
- Presence of neuritic (senile) plaques - deposits of amyloid-beta (Aβ) a. Composed of deteriorating nerve pieces that arrange themselves around a sticky protein called amyloid-beta (Aβ) → Plays MAJOR role in the PATHOGENESIS of Alzheimer’s
- Neurofibrillary Tangles - found in cytoplasm of abnormal nerve cells a. Formed by abnormal protein filaments called Tau that wrap around each other to form tangles. HALLMARK sign of Alzheimer's.
- Cerebral amyloid angiopathy (CAA) - occurs when there is abnormal accumulation of amyloid in blood vessels III. Clinical Stages ● Preclinical: brain changes, no symptoms. ● Stage - (1) Mild → (2) Moderate/Middle → (3) Severe/Late ○ Difficult to place patients into one of these stages as symptoms can overlap ● Mild: Early Stage: function is normal, independent. Family and close friends recognize changes in memory and cognition before the person affected does. ○ Increased difficulty planning activity at home or work that would normally be easy ○ Difficulty remembering names o f people they have just met ○ Difficulty coming up with right word or name of a familiar object ○ Forgetting information they have just read or had presented to them ● Moderate: Longest Stage: requires a higher level of care. Deterioration of nerve cells and brain tissue → behavioral changes, difficulty everyday tasks and expressing themselves, disease apparent to others not just close friends
○ Difficulty recalling personal information such as personal address or important personal history ○ Difficulty recalling the date or even where they are ○ Changes in sleep patterns ○ Increased episodes of wandering or getting lost ○ Changes in mood - aggression/withdraw ○ Bowel and bladder incontinence ● Severe:Late/Final Stage: around the clock care, unable to interact with the environment safely. Ability to perform ADLs lost ○ Dependance on all ADL ○ No awareness of surroundings ○ Decrease or complete loss of physical mobility (walking,sitting,swallowing) ○ Decrease or loss of ability to communicate ● Death usually occurs as a result of debilitation , typically an infection. IV. Diagnosis ● No single test can confirm Alzheimer’s ○ Exams to rule out other causes like depression, sleep disorders, medication effects, parkinson’s, hydrocephalus, stroke or tumor. ● Clinical ○ Screening tests - mini mental state exam (MMSE), mini-cog → standardized test to determine whether someone has dementia and severity of it ○ Imaging MRI and CT - eliminate other causes; measure levels of amyloid beta V. Treatment - No treatment cure or slow ● Goal = manage symptoms and improve QoL for patient and caregivers ● Early/Mid stages → Cholinesterase inhibitors (Aricept, Exelon, Razadyne) and memantine (Namenda) are prescribed ● Supportive: safe environment, caregiver support; nonmedicinal intervention for sleep disturbances should be used first ○ Nonmedicinal intervention strategies
● Loss of dopaminergic neurons and degeneration of related pathways. II. Risk Factors ● Age, male sex, genetic mutations. ● Environmental toxins (pesticides, metals). ● Head trauma. ● Other syndromes: parkinsonism - manifestation of parkinson like symptoms without having PD III. Clinical Signs (Hallmarks) ● Tremor : repetitive alternating contractions of muscles ○ Pill-rolling repetitive rubbing of thumb or forefinger - classic sign of PD ○ Symptoms occur at rest and disappear with movement as well in sleep. ● Rigidity: resistance of movement through available ROM of a given joint. ○ Cogwheeling → catching of movement that can be felt when a limb is passively taken through a ROM. ● Bradykinesia: slowness in planning, initiation, executing body movement ○ Initiating gait and turning hard, results in shuffling with little or no arm swing ○ Freezing in place during walking especially at doorways ○ Risk of falling increases ○ Facial expression appears flat ○ Tongue and Throat muscles rigid - diff swallowing ○ Speech sound soft and hoarse ● Postural instability (falls). V. Diagnosis No specific tests for diagnosing. PD diagnosis when at least 2/4 hallmark symptoms present over time ● DAT scan (measures dopamine transporters - imaging) optional - symptoms used more for dx
VI. Treatment ● Levodopa- which is mainstay - precursor to dopamine, and crosses BBB ● Dopamine agonists ● PT/exercise (neuroprotective). ● Deep brain stimulation in advanced cases. Deep brain stimulation is a reversible and nondestructive surgical procedure in which wire electrodes are implanted into the subthalamic nuclei. Inhibit or stop the abnormal nerve activity that causes tremor and other unwanted movement patterns
- You are seeing a patient with PD. You notice they are repetitively rubbing their thumb and forefinger. This is an example of what physical manifestation of the disease? a. Pill- rolling b. Cogwheeling c. Bradykinesia d. Rigidity
- You are seeing a patient with PD in your office. You notice they have difficulty turning themselves around to site in the chair freezing in the process. This is an example of what physical manifestation of the disease? a. Cogwheeling b. Bradykinesia c. Tremor d. Rigidity
- PD is characterized by each of the following except a. A loss of dopaminergic neurons b. Lewy bodies c. Neurofibrillary tangles (this is Alzheimer’s) d. Abnormal movement patters
- Each of the following statement is true of PD except: a. Environmental factors alone lead to disease development (genetics are also factors) b. It affects the substantia nigra of the brain c. It is characterized by a loss of dopaminergic neurons d. Incidence increases with age
- _____is the precursor for ____ that crosses the blood brain barrier making it the drug of choice for treatment of PD Answer: Levodopa; Dopamine
- The aim of drug therapy used for Parkinson’s disease is to increase _____ neuron activity or decrease _____ neuron activity Answer: dopaminergic; cholinergic
● Diaphoresis ● Flushing ■ aura - phenomenon that people experience, a sensation or movement that feels different or “off” and is often described as a warning sign that a seizure is about to occur ○ With impairment of consciousness or awareness ■ Typically temporal lobe ■ Can quickly spread to deeper brain^ structure and bilateral brain hemispheres ■ Involuntary, repetitive movements ● Lip smacking ● Hand rubbing ● Movement of their jaw in a chewing motion ■ If spreads → tonic-clonic seizure activity in which the muscle stiffen and entire body begins to jerk ■ Pupillary size increases ■ HR will decrease as breathing shallows ■ May or may not experience hallucinations and fear before and after seizure ■ Often misdiagnosed with psychiatric disorders ● Generalized seizures: ○ 6 Types ■ Tonic-clonic (“grand mal”): Happen in 2 phases. MOST COMMON. Lasts 60 - 90 seconds. ● Tonic phase ○ sudden tonic contraction of their muscle extension ○ lose consciousness, and bowel and bladder control may be lost ● Clonic phase ○ alternating patterns of muscle contraction and relaxation in extremities, or classing “jerking” movements ● Post clonic → postictal phase: a person may remain unconscious
■ Absence (“petit mal”): DO NOT involve convulsive activity ● Typical ○ Typically appear in children, and often disappear when they reach adulthood ○ Blank stare and/or unresponsiveness ○ Abnormal movements, repetitive motions ○ Change in postural tone and possible autonomic nervous system resulting in symptoms ○ Only last a few seconds, once pass resume normal activity ○ Symptoms subtle, unnoticed sometimes ● Atypical ○ Same as typical BUT with greater changes in muscular tone and a less distinct starting and stopping of the seizure activity ● EEG only way to distinguish typical vs atypical ○ Important to use EEG to see if atypical or focal for treatment, focal meds for example can increase absence seizure frequency ■ Myoclonic: brief periods of involuntary bilateral muscle contractions;1- 2 seconds ■ Clonic:^ loss of consciousness with loss of muscular tone ● Repeated clonic or jerking movements of extremities ● 1 - 2 minutes ■ Tonic: sudden increase in muscular tone, esp extensor musculature ● Typically occur in sleep can occur in wake which could cause injury if they are upright ● Less than 20 seconds ■ Atonic: “drop attacks” - sudden loss of muscular tone and their head or body goes limp ● May fall to ground ● Less than 15 seconds ● If you witness a seizure ○ Important to clear the area ○ Redirect them to a safe place if consciousness ○ If upright sit them down or lay them down on side to make breathing easier ○ Call 911 if > 5 minutes, if injury, or has no known seizure diagnosis ○ Do not leave them alone, do not give them food or drink, do not hold them down if clonic muscle movements IV. Diagnosis
their abnormal movement patters. Is this a generalized or focal seizure? Based upon description, what specific type of seizure did this individual experience? i. Focal ii. Focal seizure with impairment of consciousness or awareness
- You witness a seizure in which the person first exhibits a full body muscular contraction followed by a loss on consciousness and convulsions. Is this generalized or focal seizure? Based upon description, what specific type of seizure did this individual experience? i. Generalized ii. Tonic-clonic seizure
- You are baby sitting a 7 yo child with known seizure activity history. You notice they appear flushed and seem unresponsive. You ask if they are feeling alright they stare at you blankly. After a few seconds they act as if nothing happened and return to play. Is this a generalized or focal seizure? Based upon this description, what specific type of seizure did this individual experience? i. Generalized ii. Absence Seizure (Typical usually happens in kids)
Module 6.6 — Cerebrovascular Accident (Stroke)
I. Pathology ● A cerebrovascular accident (CVA): aka Stroke - disruption of blood flow to an area of the brain ○ One of leading causes of death in US ○ “Time is brain” → rapid intervention and treatment ● II. Risk Factors ● Nonmodifiable Factors ○ age- higher risk with increased age ○ sex - men have higher rate at younger ages. Women more likely to die from stroke due to women living longer than men ○ race - african americans and hispanics higher mortality then white caucasian ○ prior history of stroke ○ family history of stroke ● Modifiable Factors ○ hypertension
○ hypercholesteremia ○ diabetes ○ hypercoagulopathy ○ cardiac disease ● Modifiable Behaviors ○ smoking ○ alcohol consumption ○ birth control pills esp w smoking ○ immobility ○ obesity ○ illicit drug use III. Clinical Presentation ● Caused by 1 of 2 possible mechanisms:
- A disruption of blood flow to brain because a vessel is blocked → ischemic stroke
- A blood vessel ruptured → hemorrhagic stroke ● Ischemic strokes ○ 80% of strokes each yr ○ Most common → thrombotic or embolic in nature ○ Thrombotic → usually caused by atherosclerotic plaques that form in the major vessels supplying the brain ○ Cerebral emboli originate in the heart where they dislodge and travel to brain, can also result from plaques in carotid arteries ■ Risk increased with cardiac conditions like atrial fibrillation, recent MI, bacterial endocarditis ○ Lacunar Infarcts - happen because of blockage in smaller vessels located deeper in brain and are result of chronic hypertension and diabetes ○ Transient Ischemic Attacks (TIAs) - “mini strokes” - temp disruption of blood flow due to atherosclerotic blockage in the main feeding arteries to brain ■ Symptoms but normally resolve within 24 hours without permanent damage to brain ■ Don't ignore them, they are a warning sign - eventually a stroke ● Hemorrhagic strokes ○ Occur when blood vessel in brain spontaneously bursts ■ Resulting in hemorrhage intracerebrally or within the subarachnoid space ○ Increased pressure can lead to edema and rapid tissue death, if treatment not fast can lead to coma and death ○ Common causes: ■ Uncontrolled hypertension ■ Excessive or unmonitored use of blood thinners
