Basal Ganglia and Parkinson's Disease Overview

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Questions and Answers

What primarily creates the resting membrane potential in a cell?

Ion channel opening

Unequal distribution of ions (correct)

Electrotonic potential

Capacitance of the membrane

Which equation would you use to determine the equilibrium potential for an ion across the membrane?

Fick's First Law

Morse Code Equation

Ohm's Law

Nernst Equation (correct)

Which term refers to the ability of a membrane to store electric charge?

Electromotive force

Conductance

Resistance

Capacitance (correct)

What is the main factor affecting the flux of ions across the membrane?

Electrochemical driving force Signup and view all the answers

In the context of ion channels, what does ion selectivity refer to?

The preference of a channel for certain ions Signup and view all the answers

Which structure is part of the striatum?

Putamen Signup and view all the answers

Which neurotransmitter is primarily associated with the basal ganglia?

Dopamine Signup and view all the answers

What is a common symptom of Parkinson's disease?

Lead-pipe rigidity Signup and view all the answers

Which type of therapy is NOT used for treating Parkinson's disease?

Cognitive Behavioral Therapy Signup and view all the answers

Which of the following is responsible for maintaining posture and balance?

Cerebellum Signup and view all the answers

Which structure is implicated in hemiballism when there is a lesion?

Subthalamic nucleus Signup and view all the answers

What type of signals are used for communication within the body?

Chemical signals Signup and view all the answers

Which component of the nervous system is responsible for controlling voluntary movements?

Central nervous system Signup and view all the answers

What is a characteristic feature of Huntington's chorea?

Overactive movement Signup and view all the answers

Which structure plays a role in the cortico-basal ganglia-thalamo-cortical loop?

Thalamus Signup and view all the answers

What is the primary function of action potentials in neurons?

Signal transmission Signup and view all the answers

Which system regulates involuntary actions such as heart rate and digestion?

Autonomic nervous system Signup and view all the answers

What is a key characteristic of excitable tissue?

Ability to respond to stimuli Signup and view all the answers

In what way do neurons function similarly to electrical wires?

Both transport electrical impulses Signup and view all the answers

What is the main role of synapses in the nervous system?

Connect neurons Signup and view all the answers

What describes the difference between the central nervous system and the peripheral nervous system?

CNS includes the brain and spinal cord; PNS includes all other nerves Signup and view all the answers

What is the main characteristic of an action potential?

It is an all-or-none response. Signup and view all the answers

What does the length constant describe in the context of electrotonic conduction?

The distance over which a signal falls to 37% of its initial value. Signup and view all the answers

What is the primary role of voltage-gated Na+ channels during an action potential?

To initiate depolarization by allowing Na+ influx. Signup and view all the answers

What does the time constant (τ) indicate in the context of membrane potential?

The time required for the membrane potential to change to 63% of its final value. Signup and view all the answers

What is saltatory conduction primarily associated with?

Myelinated fibers jumping between nodes of Ranvier. Signup and view all the answers

Which statement is true regarding excitatory neurotransmitters?

They enhance the likelihood of an action potential in the post-synaptic neuron. Signup and view all the answers

What type of response does an electrotonic potential represent?

Graded response that decreases with distance. Signup and view all the answers

What is an important feature of the action potential that differentiates it from graded responses?

It follows the all-or-none principle. Signup and view all the answers

What type of receptor is an ionotropic receptor associated with?

Ligand-gated ion channels. Signup and view all the answers

Which statement best describes afterpotential?

The potential change after the action potential that can lead to reset. Signup and view all the answers

What is the primary function of the brainstem?

Regulation of blood pressure and respiratory centers Signup and view all the answers

Which pathways are primarily responsible for the control of distal muscles?

Corticospinal tract Signup and view all the answers

What role does the ascending reticular activating system play?

Regulation of consciousness and arousal Signup and view all the answers

Which area is primarily responsible for the preparation and planning of movements?

Premotor area Signup and view all the answers

Which structure consists of cranial nerves and their nuclei?

Brainstem Signup and view all the answers

Which reflex involves eye movements that stabilize gaze during head movement?

Vestibulo-ocular reflex Signup and view all the answers

The reticular formation is involved in which of the following functions?

Modulating pain Signup and view all the answers

What is the primary function of vestibular nuclei?

Balance and posture control Signup and view all the answers

Study Notes

Basal Ganglia Components

Caudate nucleus, putamen, globus pallidus, subthalamic nucleus, substantia nigra
Striatum (neostriatum) includes caudate nucleus and putamen

Basal Ganglia Circuits

Cortico-basal ganglia-thalamo-cortical loop
Direct and indirect pathways
Dopaminergic cell group

Basal Ganglia Neurotransmitters

Dopamine, GABA, Glutamate

Motor Control by Basal Ganglia and Cerebellum

Basal ganglia: selects and performs cognitive, executive, and emotional programs stored in the cerebral cortex
Cerebellum: posture maintenance, balance control, coordination, fine motor adjustments, and skilled motor learning

Basal Ganglia Lesions

Dyskinesia (movement disorder)
Inability to maintain posture
Hemiballism (subthalamic lesion)
Huntington's chorea
Parkinson's disease

Parkinson's Disease

Caused by loss of dopaminergic neurons in the substantia nigra
Symptoms:
- Rigidity (lead-pipe rigidity, cogwheel rigidity)
- Hypokinesia
- Resting tremor
Therapy:
- L-dopa (dopamine precursor)
- Stem cell therapy
- Transplantation
- Deep brain stimulation

Motor System Summary

Electrical signals and humoral signals control the body
The nervous system is organized into the central and peripheral nervous systems
The nervous system is further divided into motor, sensory, and higher brain functions
Motor system: controls movement
Sensory system: receives information from the environment
Higher brain function: complex cognitive processes

How Signals Are Transmitted to the Brain

Cell membrane potential
Action potential
Cable theory
Nerve impulse
Synapse
Central nervous system and peripheral nervous system
Autonomic nervous system

Neuron vs Wire Conductor

Neurons transmit electrical signals through electrochemical processes
This biological process is similar to the flow of electricity through a wire

Cell Membrane Potential

Electrically charged or polarized
Distribution of ions: Na+, K+
Resting membrane potential: the potential difference across the membrane when the cell is at rest
Graded potential: a small change in membrane potential that is proportional to the strength of the stimulus
Action potential: a large, rapid change in membrane potential that travels along the axon

Generating Mechanism of Membrane Potential

Ionic distribution
Driving force
Membrane potential

Ion Channel

Ion selectivity
Driving force
States of channel
Opening of channel

Na+ & K+ Equilibrium Potential

Nernst potential: the potential difference across the membrane when the ion is in equilibrium
Nernst equation: calculates the Nernst potential

Membrane Properties

Resistance: opposes the flow of electrical current
Conductance: allows the flow of electrical current
Capacitance: stores electrical charge
Polarized, depolarization, repolarization, hyperpolarization
Spike, all-or-none, afterpotential, propagation

Voltage-Gated Na+ Channel and Voltage-Gated K+ Channel

Voltage-gated channels open and close in response to changes in membrane potential
Driving force: the electrochemical gradient that drives ions across the membrane
Inactivation: a process that closes the channel after it has been open for a certain period of time

Recording of Action Potential

Electrotonic potential: a passive, graded potential that decays with distance
Action potential: a self-propagating, all-or-none event
Threshold: the level of depolarization needed to trigger an action potential

Time Constant

The time it takes for the membrane potential to reach 63.2% of its final value
Time constant = Rm x Cm (resistance x capacitance)

Length Constant

The distance over which an electrotonically conducted signal falls to 37% of its initial value
Length constant = √(Rm x Cm)

Axon Hillock and Action Potential

Axon hillock: the region of the neuron where the axon begins
Action potentials are initiated at the axon hillock

Characteristics of Action Potential

All-or-none: an action potential either occurs or it does not
Frequency mode: the frequency of action potentials can vary

Transmission of Myelinated and Unmyelinated Fibers

Myelinated fibers: conduct action potentials faster due to saltatory conduction
Unmyelinated fibers: conduct action potentials slower because the signal must travel the entire length of the axon

Synapse

Synaptic transmission: the process of communication between neurons
Excitatory: increases the likelihood of the postsynaptic neuron firing
Inhibitory: decreases the likelihood of the postsynaptic neuron firing
Neurotransmitters: chemical messengers that transmit signals across synapses

Types of Synapse

Chemical synapse
Electrical synapse

Neurotransmitters

Glutamate, GABA, acetylcholine

Glutamate Receptors

Ionotropic receptor
Ionophore

Synaptic Potential

End plate
Acetylcholine-gated ion channel
Electrotonic potential
Not action potential

Synaptic Transmission in Chemical Synapse

Action potential arrives at the presynaptic terminal
Neurotransmitter is released from the presynaptic terminal
Neurotransmitter binds to receptors on the postsynaptic membrane
Postsynaptic potential is generated

Coactivation of Alpha and Gamma Motoneurons

Gamma loop: feedback loop that regulates muscle spindle sensitivity

Topographic Organization of the Ventral Horn

Motor neurons are organized according to the muscles they innervate

Brain Stem

Medulla, pons, midbrain, diencephalon
Regulates blood pressure, respiratory center, temperature regulation, sleep, consciousness, and arousal
Reticular formation
Vestibular nuclei
Cranial nerves and their nuclei
Ascending lemniscal pathways
Reticular nuclei
Descending pathways
Pathway to and from the cerebellum

Reticular Formation

Somatic motor control: tone, balance, posture
Cardiovascular control
Pain modulation
Ascending reticular activating system: regulator of consciousness, arousal, attention, sleep, awareness
Habituation

Descending Motor Pathways

Pyramidal vs extrapyramidal pathway
Corticospinal tract
Motor area
Lateral vs medial motor system

Lateral vs Medial Motor System

Lateral motor pathways: control of distal muscles (pyramidal tract, rubrospinal tract)
Medial motor pathways: control of proximal muscles, posture, ability to stand or sit upright, control righting reflexes (vestibulospinal system)

Vestibular System Reflexes

Vestibular receptors
Vestibular nuclei (VN): excitatory to antigravity alpha motoneurons
Vestibulo-ocular reflex (VOR): eye movements that stabilize gaze during head movement
Optokinetic reflex; follow objects in motion with stationary head

Motor Cortex

Primary motor cortex
Supplementary motor area (SMA)
Premotor area
Cingulate cortex
Posterior parietal cortex

Motor Cortex: Details

Primary motor cortex: Homunculus
Supplementary motor area: contextural control, programming complex sequences of movement and coordinating bilateral movements
Premotor area: prepare for exercise, plan, learn new exercises, "mirror neuron"

Cerebellum

Cerebellum: coordinates movement and maintains balance
Cerebellar cortex
Deep cerebellar nuclei

Cerebellum: Functions

Controls coordination, balance, and fine motor movements
Learns new motor skills
Involved in cognition and language

Human Anatomy and Physiology Course Outline

The course covers the anatomy and physiology of the human body
The course is divided into two parts:
- Part I: Communication in the Body and Control of the Body
- Part II: The Motor System, The Sensory System, and the Higher Function of the Brain
The course includes lectures, dissections, and laboratory exercises

How Can We Transmit Signals to the Brain

The nervous system controls the body through electrical and chemical signals
The brain receives sensory information from the environment and sends motor commands to the body

Human Intelligence vs Artificial Intelligence

Human intelligence: based on biological systems, capable of learning and making decisions, susceptible to error and bias
Artificial intelligence: based on computer algorithms, capable of performing tasks and processing large amounts of data, limited by its programming

Objectives

Cell membrane potential
Action potential
Cable theory
Nerve impulse
Synapse
Central nervous system and peripheral nervous system
Autonomic nervous system
Excitable tissue

Key Facts

The nervous system is a network of specialized cells called neurons that transmit information throughout the body.
Electrical impulses are conveyed by neurons throughout the nervous system.
The brain is the control center of the nervous system.
Nerves transmit information from the brain to the body and vice versa.
The brain is responsible for a wide range of functions, including thought, emotion, movement, and sensation.

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Description

Explore the key components and circuits of the basal ganglia, including their role in motor control and neurochemistry. This quiz covers important aspects of basal ganglia lesions and their relation to movement disorders such as Parkinson's disease and Huntington's chorea.