Chapter 34_1 flashcards
(15 cards)
Central Nervous System (CNS) vs. Peripheral Nervous System (PNS)
CNS: Consists of the brain and spinal cord. PNS: Consists of cranial and spinal nerves, including the somatic and autonomic nervous systems.
Neuron: Basic Components
Dendrites: Receive incoming signals. Cell Body: Contains the nucleus. Axon: Transmits outgoing signals. Axon Terminals: Release neurotransmitters.
Myelin: Function & Significance
A protective, fatty sheath that insulates the axons of some neurons. It allows for rapid and efficient conduction of nerve impulses. Damage to myelin (demyelination) disrupts nerve signals, as seen in disorders like Multiple Sclerosis.
Upper vs. Lower Motor Neuron (UMN vs. LMN)
UMN: Neurons that originate in the brain’s motor cortex and travel down to the spinal cord. A UMN disorder indicates 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 periphery.
Decussation: Definition & Clinical Implication
The crossover point of nerve tracts, which occurs in the brainstem (medulla) for the 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): Can be excitatory or inhibitory; critical for muscle contraction at the neuromuscular junction. Dopamine: Primarily inhibitory; crucial for modulating voluntary movement, motivation, and reward. Produced in the substantia nigra.
Key Neurotransmitters: GABA & Glutamate
GABA (Gamma-aminobutyric acid): The chief inhibitory neurotransmitter in the CNS; has a relaxing, anti-anxiety, and anticonvulsive effect. Glutamate: The major excitatory neurotransmitter in the CNS; involved in cognition, memory, and learning. Excess glutamate is neurotoxic.
Cerebrum: Four Lobes & Their Primary Functions
Frontal: Reasoning, planning, movement, emotions, speech (Broca’s area). Parietal: Sensation, spatial awareness. Temporal: Hearing, memory, speech comprehension (Wernicke’s area). Occipital: Vision.
Aphasia: Expressive vs. Receptive
A language disorder, often from damage to the left hemisphere. Expressive Aphasia (Broca’s area damage): Patient cannot produce speech but can understand. Receptive Aphasia (Wernicke’s area damage): Patient can speak but cannot comprehend language and uses illogical words.
Brainstem: Components & Vital Function
Components: Midbrain, pons, and medulla oblongata. Function: The “vital sign center” that controls essential functions like breathing, heart rate, blood pressure, and consciousness. Damage is often life-threatening.
Cerebellum: Function & Consequence of Damage
Responsible for smooth, coordinated movements, balance, and posture. Damage results in ataxia (an uncoordinated gait) and jerky movements on the same (ipsilateral) side of the body.
Primary vs. Secondary Headaches
Primary Headaches: Arise independently and are not caused by another medical condition (e.g., migraine, tension, cluster). Secondary Headaches: Caused by an underlying condition, such as a head injury, tumor, sinus infection, or vascular problem.
Seizure: Definition
A sudden, abnormal, disorderly discharge of neurons within 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.
Aura, Ictal, and Postictal Periods
Aura: A unique sensation that precedes a seizure, such as seeing a strange light or smelling an odd odor. Ictal Period: The time during the seizure itself. Postictal Period: The phase after a seizure, often characterized by drowsiness, confusion, and headache as the brain recovers.
