Chapter 35_1 flashcards
(16 cards)
Two Main Divisions of the Nervous System
Central Nervous System (CNS): Brain and spinal cord. Peripheral Nervous System (PNS): Cranial nerves and spinal nerves.
Neuron: Basic Components & Function
Dendrites receive signals, the cell body processes them, the axon transmits the outgoing signal, and axon terminals release neurotransmitters to communicate with other neurons.
Myelin: Function & Significance
A protective, fatty sheath that insulates the axons of some neurons, allowing for rapid and efficient conduction of nerve impulses. In demyelinating diseases like Multiple Sclerosis, this sheath is damaged, disrupting nerve signals.
Upper vs. Lower Motor Neuron (UMN vs. LMN)
UMN: Neurons originating in the brain’s motor cortex that travel down to the spinal cord. A UMN disorder points to a problem in the brain or corticospinal tract. LMN: Motor neurons that exit the spinal cord to connect with muscles. An LMN disorder indicates a problem at the spinal cord level or in the periphery.
Decussation: Definition & Clinical Implication
The crossover point of nerve tracts, which occurs in the brainstem (medulla) for the main motor (corticospinal) tract. This is why an injury to one side of the brain typically causes motor and sensory deficits on the opposite (contralateral) side of the body.
Key Neurotransmitters: Acetylcholine (Ach) & Dopamine
Acetylcholine (Ach): Acts at the neuromuscular junction to stimulate muscle contraction. Dopamine: An inhibitory neurotransmitter produced in the substantia nigra; crucial for modulating voluntary movement and is depleted in Parkinson’s disease.
Key Neurotransmitters: GABA & Glutamate
GABA: The chief inhibitory neurotransmitter in the CNS; has a relaxing, anti-anxiety, and anticonvulsant effect. Glutamate: The major excitatory neurotransmitter in the CNS; excess levels are toxic to brain cells and contribute to damage after a stroke.
Cerebrum: Four Lobes & Primary Functions
Frontal Lobe: Reasoning, judgment, voluntary movement, emotions, speech (Broca’s area). Parietal Lobe: Sensation, body position awareness. Temporal Lobe: Hearing, memory, speech comprehension (Wernicke’s area). Occipital Lobe: Vision.
Aphasia: Expressive vs. Receptive
A language disorder, often from damage to the left hemisphere. Expressive Aphasia (Broca’s damage): The person cannot produce speech but can understand. Receptive Aphasia (Wernicke’s damage): The person can speak fluently but uses illogical words and cannot understand.
Brainstem: Components & Vital Function
Components: Midbrain, pons, medulla. Function: Controls vital life functions like breathing, heart rate, blood pressure, and consciousness.
Cerebellum: Function & Consequence of Damage
Responsible for smooth, coordinated movements, balance, and posture. Damage leads to ataxia (an uncoordinated gait) and jerky movements on the same (ipsilateral) side of the body.
Babinski Reflex: Significance in Adults
A positive Babinski reflex (toes flare upward and outward when the sole of the foot is stimulated) indicates an upper motor neuron disorder. A normal response is for the toes to flex inward.
Primary vs. Secondary Headaches
Primary Headaches: Arise independently and are not caused by another medical condition (e.g., migraine, tension, cluster). Secondary Headaches: Are symptoms caused by another underlying condition, such as a head injury, tumor, or sinus infection.
Seizure: Definition
A sudden, abnormal, disorderly discharge of neurons in the brain that causes a transient alteration in brain function, consciousness, or motor/sensory activity.
Epilepsy: Definition
A chronic neurological disorder characterized by recurrent, unprovoked seizures. Requires at least two unprovoked seizures 24 hours apart for diagnosis.
Aura, Ictal, and Postictal Periods
Aura: A unique sensation (e.g., strange light or smell) that precedes a seizure. Ictal Period: The time during the seizure itself. Postictal Period: The phase after a seizure, often characterized by drowsiness, confusion, and headache.
