BIO SCI 202: Nervous System Part 1 — Neurons, Action Potentials & Reflexes

What does CNS stand for?

Central Nervous System

What is the primary function of the brain?

It receives, integrates, interprets, and responds to sensory stimuli.

What is the spinal cord's role in the nervous system?

It serves as the pathway for messages between the brain and the body.

What are the five sections of the spinal cord?

Cervical, thoracic, lumbar, sacral, coccygeal.

What does PNS stand for?

Peripheral Nervous System

What is the function of the sensory division of the PNS?

It carries sensory information to the CNS.

What does the motor division of the PNS do?

It carries commands from the CNS to target organs.

What is the role of the somatic motor subdivision?

It controls skeletal muscles for movement.

What is the sympathetic division of the autonomic nervous system responsible for?

It prepares the body for 'fight or flight' responses.

What does the parasympathetic division do?

It promotes 'rest and digest' functions.

What is the enteric division of the autonomic nervous system associated with?

It regulates functions of the digestive tract.

What are neurons?

Functional units of the CNS and PNS that receive, integrate, generate, and transmit signals.

What is the difference between a neuron and a nerve?

A neuron is a nerve cell, while a nerve is a bundle of neuron axons.

What is a ganglion?

A cluster of neuron cell bodies that acts as a relay station.

What is the function of the soma (cell body) of a neuron?

It processes and integrates inputs.

What is the role of dendrites in a neuron?

They carry electrical signals to the soma.

What is the function of the axon?

It carries electrical signals away from the soma.

What happens at the axon terminals?

Electrical impulses change to chemical messages.

What is the synapse?

The junction where neurons communicate with each other and target organs.

What are the three classes of neurons based on function?

Sensory (afferent), interneurons, motor (efferent).

What distinguishes upper motor neurons from lower motor neurons?

Upper motor neurons are located in the brain and carry signals to the spinal cord, while lower motor neurons transmit signals from the spinal cord to muscles.

What is the function of astrocytes?

They provide structural support and transport substances between blood vessels and neurons.

What is the role of oligodendrocytes?

They form myelin sheaths in the brain and spinal cord.

What is the function of Schwann cells?

They form myelin sheaths around peripheral neurons.

What is myelin and its function?

Myelin acts as an insulator for axons, speeding up neurotransmission.

What is membrane potential?

The electrical voltage difference across the cell membrane.

What is the resting membrane potential value?

About -70 mV (inside negative).

What ion concentration gradients are important for membrane potential?

Na+ is higher outside the cell, and Cl- is also higher outside the cell.

What ion concentrations are higher outside the cell?

Na+ and Cl-.

What ion concentration is higher inside the cell?

K+.

What role do large anions play in membrane potential?

They stay trapped inside the cell, contributing to the negative charge.

What is the function of the sodium-potassium pump?

It moves 3 Na+ out for every 2 K+ in, maintaining ion gradients and resting potential.

What type of ion channel opens in response to physical force?

Mechanically gated channels.

What type of ion channel opens when a ligand binds?

Ligand-gated channels.

What triggers voltage-gated channels to open?

Changes in membrane voltage.

What is an action potential?

A rapid, temporary reversal of voltage across the cell membrane that allows neurons to transmit signals.

What is the initial energy source for an action potential?

The stored electrochemical gradient.

What happens during depolarization of an action potential?

Voltage-gated Na+ channels open, allowing Na+ to rush in.

What occurs during repolarization?

Voltage-gated Na+ channels close and voltage-gated K+ channels open, allowing K+ to leave the cell.

What is hyperpolarization in the context of action potentials?

When voltage-gated K+ channels remain open longer than needed, causing excessive K+ to leave.

What is spatial summation?

Signals from multiple presynaptic neurons arrive at the same time to reach threshold.

What is temporal summation?

High-frequency signals arrive in rapid succession to reach threshold.

What is the absolute refractory period?

The period during depolarization and early repolarization when a second action potential cannot fire.

What is the relative refractory period?

The period during late repolarization and hyperpolarization when a stronger-than-normal stimulus can trigger a second action potential.

What happens when an action potential reaches the axon terminal?

Voltage-gated Ca2+ channels open, Ca2+ enters, and neurotransmitter vesicles are released.

What is the role of neurotransmitters at the synapse?

They bind to receptors on the postsynaptic cell, initiating a graded potential.

What effect do toxins that block voltage-gated Na+ channels have?

They prevent depolarization and action potential generation, leading to numbness and paralysis.

What is the effect of toxins that keep voltage-gated Na+ channels open?

They cause uncontrolled firing, leading to seizures and paralysis.

What is the stretch reflex?

An involuntary muscle contraction in response to stretching a muscle.

What is the withdrawal reflex?

An involuntary response that pulls a body part away from a painful stimulus.

What is the patellar reflex?

A reflex where tapping the patellar tendon causes the lower leg to jerk forward.

What is the calcaneal reflex?

A reflex where tapping the Achilles tendon causes the foot to jerk into plantar flexion.

What is the biceps reflex?

A reflex where tapping the biceps brachii tendon causes the forearm to flex at the elbow.