Nervous System Organization (Lecture #1)

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Questions and Answers

What is the main function of the Central Nervous System (CNS)?

  • Processing and interpreting information (correct)
  • Transmitting signals to the body
  • Regulating blood flow
  • Releasing neurotransmitters

Which types of neurons are included in the Peripheral Nervous System (PNS)?

  • Motor neurons and interneurons
  • Interneurons and sensory neurons
  • Sensory (afferent) and motor (efferent) neurons (correct)
  • Cranial and spinal neurons

What is the primary role of microtubules within the axon?

  • Creating action potentials
  • Forming synapses with other neurons
  • Transporting neurotransmitters and molecules (correct)
  • Conducting action potentials

What characteristic of the resting neuron contributes to its polarization?

<p>Uneven distribution of Na+ and K+ ions (D)</p> Signup and view all the answers

What type of conduction occurs in myelinated axons?

<p>Saltatory conduction (B)</p> Signup and view all the answers

What best describes the nature of graded potentials?

<p>They can vary in size and weaken over distance (C)</p> Signup and view all the answers

What is the primary function of the Blood-Brain Barrier (BBB)?

<p>To prevent harmful substances from entering the CNS (D)</p> Signup and view all the answers

What role do Na+/K+ pumps play in neuron physiology?

<p>They maintain resting membrane potential by pumping ions (A)</p> Signup and view all the answers

What is the primary role of Ca²⁺ influx in neurotransmission?

<p>To facilitate neurotransmitter release (C)</p> Signup and view all the answers

How does stronger stimuli affect action potentials?

<p>It does not change the size of action potentials (D)</p> Signup and view all the answers

Which neurotransmitter is primarily involved in skeletal muscle contraction?

<p>Acetylcholine (C)</p> Signup and view all the answers

What effect does GABA have on neurons?

<p>Inhibition through Cl- channel opening (A)</p> Signup and view all the answers

What differentiates the sympathetic and parasympathetic nervous systems?

<p>Sympathetic activates 'fight or flight' responses (C)</p> Signup and view all the answers

In the context of sensory adaptation, which statement is true regarding smell compared to taste?

<p>Sensitivity to smells decreases over time (D)</p> Signup and view all the answers

What type of neurotransmitter receptors are found in the parasympathetic nervous system?

<p>Muscarinic receptors (D)</p> Signup and view all the answers

How do SSRIs (selective serotonin reuptake inhibitors) affect serotonin levels?

<p>They enhance serotonin levels by preventing reuptake (D)</p> Signup and view all the answers

What characterizes supertasters compared to non-tasters?

<p>Supertasters have more taste buds and higher sensitivity (A)</p> Signup and view all the answers

Flashcards

Nervous System Divisions

The nervous system is divided into CNS (Central Nervous System) and PNS (Peripheral Nervous System).

CNS Function

The CNS includes the brain and spinal cord, processing and interpreting information.

PNS Components

The PNS includes sensory (afferent) and motor (efferent) neurons, and is divided into somatic and autonomic systems.

Neuron Structure

Neurons transmit signals: Dendrites receive, soma integrates, axons transmit, terminals release neurotransmitters.

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Blood-Brain Barrier

The Blood-Brain Barrier protects the CNS by preventing harmful substances from entering.

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Resting Membrane Potential

A resting neuron has a membrane potential of about -70mV, with high K+ inside and high Na+ outside.

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Action Potential

An action potential occurs with depolarization when Na+ channels open, followed by repolarization as K+ channels open.

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Graded Potentials

Graded potentials vary in size and weaken over distance before reaching the synapse.

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Ca²⁺ Influx

Calcium ions entering the cell trigger neurotransmitter release.

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Neurotransmitter Removal

Processes including breakdown, reuptake, and diffusion to clear neurotransmitters from synaptic cleft.

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Depolarizing Synaptic Potential

Occurs when Na+ channels open, leading to a cell becoming less negative (e.g., glutamate).

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Hyperpolarizing Synaptic Potential

Occurs when Cl- or K+ channels open, making the cell more negative (e.g., GABA).

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Action Potential Frequency

Stronger stimuli produce more frequent action potentials, but not larger ones.

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Motor End Plate

Site where acetylcholine binds to initiate muscle contraction.

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Common Excitatory Neurotransmitters

Includes glutamate, dopamine (in certain areas), and acetylcholine (nicotinic).

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Somatic vs. Autonomic Control

Somatic = voluntary movements; Autonomic = involuntary functions like heart rate.

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Sympathetic vs Parasympathetic

Sympathetic increases heart rate (fight or flight); Parasympathetic decreases heart rate (rest & digest).

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Taste Buds

Sensory organs on papillae that regenerate from stem cells, responsible for taste perception.

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Study Notes

Nervous System Organization (Lecture #1)

  • The nervous system uses electrical and chemical signals to control body functions.
  • It's divided into the CNS (Central Nervous System) and PNS (Peripheral Nervous System).
  • CNS: Processes information; includes the brain and spinal cord.
  • PNS: Transmits signals between CNS and body; includes nerves.
  • CNS organization involves interpreting and processing information.
  • PNS includes sensory (afferent) neurons and motor (efferent) neurons, further categorized into somatic (voluntary) and autonomic (involuntary) divisions.
  • Neuron structure: Dendrites receive signals, cell body (soma) integrates, axon transmits impulses, axon terminals release neurotransmitters.
  • Microtubules are vital for transporting molecules within the axon, including neurotransmitters.
  • The Blood-Brain Barrier (BBB) protects the CNS by preventing harmful substances from entering. Cerebrospinal fluid (CSF) provides nutrients.
  • The blood-brain barrier can be affected by diseases such as meningitis, multiple sclerosis, Alzheimer's, and stroke.
  • The spinal cord transmits signals and orchestrates reflexes; it has gray matter (cell bodies) and white matter (axons).
  • Peripheral nerves primarily consist of axons.
  • A reflex arc is a simple neural circuit where sensory neurons directly synapse onto motor neurons, enabling rapid, involuntary responses.

Neuron Communication (Lecture #2)

  • Resting neuron has a membrane potential of approximately -70mV.
  • Inside the neuron: High potassium (K+) and negatively charged proteins. Outside: High sodium (Na+) and chloride (Cl-).
  • Polarization is due to ion imbalance.
  • The Na+/K+ pump maintains the imbalance by actively transporting 3 Na+ ions out and 2 K+ ions in, using ATP energy.
  • Action potentials occur in axons; involve Na+ channels opening for depolarization, followed by K+ channels opening for repolarization.
  • Action potentials are non-decremental; signal strength remains constant over distance.
  • Myelinated axons conduct signals faster due to saltatory conduction (jumping between Nodes of Ranvier).
  • Unmyelinated axons conduct signals slower through continuous conduction.
  • Synaptic potentials are graded and decremental; strength varies and weakens over distance.
  • Synaptic sequence: Action potential reaches terminal → influx of Ca2+ triggers neurotransmitter release → neurotransmitter binds to receptors on dendrites.
  • Neurotransmitters are removed from the synapse: broken down, reabsorbed, or diffuse away.
  • Depolarizing neurotransmitters (e.g., glutamate) open Na+ channels. Hyperpolarizing ones (e.g., GABA) open Cl- or K+ channels.
  • Stronger stimuli result in more frequent, not larger, action potentials.
  • At the motor end plate, acetylcholine (ACh) binds to nicotinic receptors, causing Na+ influx and muscle contraction.
  • Acetylcholinesterase breaks down ACh to terminate the signal.
  • Common neurotransmitters and their effects: Excitatory (glutamate, dopamine, ACh - nicotinic); Inhibitory (GABA, glycine); Both (dopamine, serotonin, ACh - muscarinic).
  • Substances affecting neural transmission: Cocaine blocks dopamine reuptake; Botulinum toxin prevents ACh release; Curare blocks nicotinic receptors; SSRIs increase serotonin by blocking reuptake.

Autonomic Nervous System (Lecture #3)

  • Somatic nervous system controls voluntary actions (skeletal muscles). Autonomic controls involuntary functions (e.g., heart, digestion), influenced by the hypothalamus and brainstem.
  • Somatic responses are faster (due to thick myelinated axons), while autonomic responses are slower (due to thin or unmyelinated axons).
  • Sympathetic ("fight or flight") response: Increased heart rate, blood pressure, bronchodilation, and glucose release. Parasympathetic ("rest and digest"): Lowers heart rate, boosts digestion.
  • Neurotransmitters involved: Somatic (ACh - nicotinic); Parasympathetic (ACh - muscarinic); Sympathetic (ACh -> norepinephrine - adrenergic).
  • Adrenal glands release epinephrine (adrenaline) in short-term stress response.
  • Cortisol (a steroid) is involved in long-term stress response, regulating glucose metabolism and suppressing the immune system.

Smell & Taste (Lecture #4)

  • Smell has a strong emotional connection, with the olfactory bulb connecting to the limbic system.
  • More smells than tastes exist.
  • Sensory adaptation reduces sensitivity over time.
  • Taste buds are located on papillae and regenerate from stem cells.
  • Taste sensitivity varies: Bitter is most, followed by sour, sweet/umami, and salty.
  • Supertasters have more taste buds and are more sensitive (common in women). Non-tasters have fewer and better tolerate strong flavors.

Hearing & Vision (Lectures #5 & #6)

  • Sound travels: Pinna → auditory canal → eardrum → ossicles → cochlea → auditory nerve.
  • The basilar membrane detects sound frequencies based on place coding (base for high, apex for low frequency).
  • Vision pathway: Cornea → aqueous humor → lens → retina.
  • Accommodation (lens thickening) adjusts for near vision, regulated by the parasympathetic system.
  • Photoreceptors in the retina: Rods detect light, and cones detect color (red, green, blue).
  • Melatonin regulates circadian rhythms, influenced by blue light exposure.

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